1 Table of Contents General Tips for Getting Started 2 Errata 4 Before You Teach a Laboratory 5 Pedagogical Model 7 Lab 1: Thinking Like a Geologist 8 Lab 2: Plate Tectonics and the Origin of Magma 23 Lab 3: Mineral Properties, Identification, and Uses 40 Lab 4: Rock-Forming Processes and the Rock Cycle 48 Lab 5: Igneous Rocks and Processes 54 Lab 6: Sedimentary Processes, Rocks, and Environments 61 Lab 7: Metamorphic Rocks, Processes, and Resources 72 Lab 8: Dating of Rocks, Fossils, and Geologic Events 77 Lab 9: Topographic Maps and Orthoimages 87 Lab 10: Geologic Structures, Maps, and Block Diagrams 99 Lab 11: Stream Processes, Landscapes, Mass Wastage, and Flood Hazards 116 Lab 12: Groundwater Processes, Resources, and Risks 127 Lab 13: Glaciers and the Dynamic Cryosphere 137 Lab 14: Dryland Landforms, Hazards, and Risks 146 Lab 15: Coastal Processes, Landforms, Hazards, and Risks 154 Lab 16: Earthquake Hazards and Human Risks Pearson Education, Inc. 1
2 GENERAL TIPS FOR GETTING STARTED Please consider these tips to help you use the Laboratory Manual in Physical Geology AGI/NAGT (10 th edition) and this Instructor Manual more effectively. 1. Review the lab manual Instructor Resource Materials that are available to you, and obtain the ones you need. You can find these resources online at or you can contact your Pearson-Prentice Hall sales representative at 2. Review the Pedagogical Model upon which the lab manual is based (page 6). 3. Familiarize yourself with the following resource materials that are available to your students: Pre-lab Videos created by Callan Bentley help students understand how to successfully complete the lab activities by following a clear series of steps. They can be accessed with the QR code on the cover flap of the lab manual or at mygeoscienceplace.com GeoTools are cardboard and transparent rulers, protractors, grain size scales, UTM grids, and more for students to cut out and use as needed. They can be found at the end of the lab manual. A Math Conversion Chart, Introduction to SI Units, pictures of lab equipment, and a map of North America are available in the Preface of the lab manual (pages xi xiv). TMYN TM, MasteringGeology TM, and Learning Catalytics TM, if used. QR Codes, which provide students with quick access to web sites they need or may use in addition to resources provided in the lab manual. 4. Consider personalizing your students learning experience by using MasteringGeology TM, Learning Catalytics TM, or TMYN (The Math You Need, When You Need It) remedial tutorials. MasteringGeology TM is an online tutorial and homework program. Pre-lab video quizzes can be assigned as formative assessments for you to analyze with a variety of tools to isolate weaknesses and misconceptions of a student or class. This allows you to build a plan for intervention and make the most of the time that students will have in the laboratory. Learn more at Learning Catalytics TM is pedagogical approach in which students use any webenabled device of their choice (smart phone, tablet, laptop, etc.) to engage in formative assessments (that guide learning) and summative assessments (that are used for grading purposes) before, during, or after the laboratory. You can create or select multiple choice questions for students to answer and/or you can create or select openended questions that ask for numerical, written, or graphical responses. You can build a seating chart, and then use the chart to see what students or groups of students have answered specific items and how they answered them. You can assign questions for students to answer synchronously during class/lab (one question is answered by each student, but all students address the question at the same time), or in a self-paced Pearson Education, Inc.
3 mode for formative or summative assessments. Learn more at learningcatalytics.com/ TMYN TM is an online set of modular math tutorials for students in any introductory geoscience, developed and managed by Jennifer Wenner (University of Washington Oshkosh) and Eric Baer (Highline Community College) with funding from the National Science Foundation. You can assign the free modules for students to use on their own, or you can assign them as formative or summative assessments. You can also compare students pre-lab and post-lab ability to solve geological problems involving mathematics and, thereby, measure the extent of their learning. Learn more at serc.carleton.edu/mathyouneed/index.html Please send comments, criticisms, and suggestions regarding the laboratory manual or this instructor manual directly to Rich Busch, Department of Geology and Astronomy, West Chester University, West Chester, PA or Thank you! 2015 Pearson Education, Inc. 3
4 ERRATA Lab 2 On page 58, part B (Reflect and Discuss) is actually part D. On page 68, part A, item 5b, the vector motions should be in mm/yr (not cm/yr). Lab 5 On page 136, Figure 5.4, Step 3: for the description of pegmatitic texture, change 1 mm to 1 cm. On page 144, part A, change Minerals Database (pages ) to Minerals Database (Pages 93 97). On page 152, part C, change 200 million years ago to 190 million years ago. Lab 6 On page 185, part B, change Photograph A to Photograph B Pearson Education, Inc.
5 BEFORE YOU TEACH A LABORATORY BEFORE LAB BEGINS 1. Decide what activities your students should complete before and during the lab. Most labs deliberately include more activities than your students could complete in a single lab period, so you can choose the activities that you think will best enable your students to learn what you expect them to learn in the lab time available. 2. Check the list of errata (page 4 in this Instructor Manual) for corrections that must be made in the lab that you plan to use. 3. Assign pre-lab preparations for your students to complete. This may include: a. Complete the first activity of the lab and by the start of the lab. b. Watch the pre-lab video for the lab. c. Take a pre-lab quiz using MasteringGeology TM or other quiz of your design. d. Complete assigned readings in the lab manual, class textbook, or other. e. Know what activities must be completed by the end of the lab period. f. Know what materials each student must bring to the start of the lab (as noted in the blue boxes of the lab manual that start of each activity and as noted at the start of each laboratory section of this Instructor Manual). 4. Review and assemble the Instructor Materials that you must provide during the lab period. A list of the Instructor Materials is provided in this instructor manual, at the start of each for each lab section. They are generic lists only and must be modified by you to avoid confusion and know exactly what to assemble for the laboratory. 5. Review each activity and the Answers to Questions (provided in this instructor manual) for each activity/question that you assign to your students. Some questions have more than one right answer depending on how you have presented material for students to read or explore. 6. Analyze pre-lab results, if you are assigned a pre-lab quiz using MasteringGeology TM or a similar program. Use that information to isolate weaknesses and misconceptions of a student or class. Then build a plan for intervention that makes the most of the time that students will have in the laboratory. 7. Develop the scope and sequence of the teaching/learning plan that you plan to follow during the lab period. a. What will you do at the start the lab period? For example, you may: Declare the scope and sequence of what students must do during the lab period, how they are expected to do/record their own work yet work and/or work in collaborative groups, and the safety practices that they must follow. Review pre-lab weaknesses and misconceptions and/or use lab PowerPoint to introduce the lab Pearson Education, Inc. 5
6 Review how and where students obtain the materials they need (the materials that you are providing in the lab). Address questions. b. What will you do during the lab period? For example, you may: Allow students to work on activities at their own pace or according to your other plan. Move about the room to be sure students/groups have the materials they need and are on task. Address questions, use guiding questions of your own to help students scaffold from the unknown to the known (or inability to ability), and implement personal interventions as needed (especially relative to pre-lab quiz results and special-needs). c. What will you do near/at the end of the lab period? For example, you may: Review the results of each activity (item by item or the Reflect and Discuss questions for formative purposes (i.e., to guide learning). Have students submit their individual worksheets for summative assessment (evaluation for a grade). Have students complete a graded post-lab quiz. Have students address the Think About It questions linked to the lab and/or the activities that they completed. DURING THE LAB PERIOD 8. Carry out the plan that you developed above, in parts 7a and 7b. AT/NEAR THE END OF THE LAB PERIOD 9. Carry out the plan that you developed above, in part 7c. 10. Grade materials and provide grades and feedback to students in a timely fashion. 11. Reflect on any feedback about the lab that students may have volunteered and use it to inform/guide your grading and future teaching Pearson Education, Inc.
7 PEDAGOGICAL MODEL Each lab proceeds from items 1 through 4 and involves resources and assessments Pearson Education, Inc. 7
8 LABORATORY ONE Thinking like a Geologist BIG IDEAS: Geology is the science of Earth, so geologists are Earth scientists or geoscientists. Geologists observe, describe, and model the materials, energies, and processes of change that occur within and among Earth s spheres over time. They apply their knowledge to understand the present state of Earth, locate and manage resources, identify and mitigate hazards, predict change, and seek ways to sustain the human population. THINK ABOUT IT (Key Questions): How and why do geologists observe Earth materials at different scales (orders of magnitude)? (Activity 1.1) What materials, energies, and processes of change do geologists study? (Activity 1.2) How and why do geologists make models of Earth? (Activity 1.3) How and why do geologists measure Earth materials and graph relationships among Earth materials and processes of change? (Activity 1.4) How is the distribution of Earth materials related to their density? (Activities 1.4, 1.5) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser metric ruler (cut from GeoTools sheet 1 or 2) calculator blue pencil or pen (Activity 1.3 only) drafting compass (Activity 1.3 only) several coins (Activity 1.3 only) INSTRUCTOR MATERIALS (Check off items you will need to provide.) ACTIVITY 1.1: Geologic Inquiry none Pearson Education, Inc.
9 ACTIVITY 1.2: Spheres of Matter, Energy, and Change none ACTIVITY 1.3: Basketball Model of Earth s Spheres drafting compasses (one per student) extra metric rulers (for students who forgot them) extra blue pencils (for students who forgot them) several coins/student: pennies, nickels, quarters, dimes ACTIVITY 1.4: Measuring and Determining Relationships extra metric rulers (for students who forgot them) small (10 ml) graduated cylinders (one per group of students) waterproof modeling clay (at least 1 cubic cm. per student) gram balance (one per group of students) wash bottle or dropper bottle, filled with water (one per group) paper towels to clean up spills ACTIVITY 1.5: Density, Gravity, and Isostasy extra metric rulers (for students who forgot them) gram balance wood blocks about 8 cm x 10 cm x 4 cm. Do not use cubes because they float diagonally. Pieces of pine 2 x 4 studs work well. For variety, give some groups pine and others a more dense wood like walnut (one block per group of students). small bucket or plastic basin of water to float wood block (one per group of students) paper towels to clean up spills ACTIVITY 1.6: Isostasy and Earth s Global Topography large (500 ml) graduated cylinders (one per group of students) pieces of basalt and granite that will fit into the large graduated cylinders (one piece of each per group of students) gram balance wash bottle filled with water or dropper (one per group) paper towels to clean up spills INSTRUCTOR NOTES AND REFERENCES 1. Metric and International System of Units (SI): refer to laboratory manual page xi. 2. Mathematical conversions: refer to laboratory manual page xii. 3. In Activity 1.5 of this laboratory, students explore the isostasy of a floating wood block. You can make this more of a real-world inquiry by providing students with two or more densities of wood. For example, pine and walnut work well because 2015 Pearson Education, Inc. 9
10 students can easily see that the pine blocks float higher than the walnut blocks. This makes it easier for students to conceptualize how isostatic differences between granitic and basaltic blocks may explain Earth s hypsographic curve. 4. Hydrous minerals of Earth's Mantle. Hydrous minerals include not only the obviously hydrous minerals like gypsum, but also minerals like amphibole and pyroxene that are "nominally hydrous" (actually hydrous even though they are generally regarded as anhydrous). See David R. Bell and George R. Rossman's 1992 paper on this (Science, v. 255, p ). Shortly after the Science article was published, Science News quoted Bell and Rossman as estimating that the mantle may contain a volume of water equal to 80% of the volume of the world's oceans. Even if this Bell and Rossman estimate of mantle water seems high, one must still account for the hydrous and nominally hydrous minerals in Earth's crust. Therefore, having students assume that the solid Earth may contain water equal to 80% of the volume of the world's oceans may be a conservative estimate. For information on recycling of water into Earth's mantle, refer to: C. Meade and R. Jeanloz Deep-focus earthquakes and recycling of water into Earth's mantle. Science 252: Pearson Education, Inc.
11 LAB 1 ANSWER KEY ACTIVITY 1.1: Geologic Inquiry 1.1A. Observation, analysis, and description of the parts of Figure Pearson Education, Inc. 11
12 1.1B. Every part of Figure 1.1 shows objects that contain copper (Cu). 1.1C. Analyze Figure 1.1 and answer the following questions. 1.1D. 1. The best location for a new mine (pit) is location C, because the rocks there have the same pink-red color in the false-colored satellite image as the rocks of the current and old copper mine pits. 1.1D. 2. To see if location C is actually a good source for more copper ore, one must go there to collect samples of the rock and determine if it contains copperbearing minerals in profitable quantities to be mined Pearson Education, Inc.
13 ACTIVITY 1.2: Spheres of Matter, Energy, and Change 1.2A Pearson Education, Inc. 13
14 1.2B. answer sheet Pearson Education, Inc.
15 1.2C. Completed Venn diagram 1.2D. Reflect and Discuss: Do you think that most change on Earth occurs within individual systems, at boundaries between two systems, or at the intersections of more than two systems? Why? In general, one might expect that at the most change occurs at intersections of more than two systems, because there are more varied materials and energy forms (than in one system or the boundary between just two systems) Pearson Education, Inc. 15
16 ACTIVITY 1.3: Modeling Earth Materials and Processes 1.3A. 1. See the completed basketball model below. Students should realize that it is nearly impossible for them to draw separate lines for hydrosphere and atmosphere (because they are so narrow compared to the diameter of the basketball). The crust will be about the thickness of a pencil/pen line. You could have students use another color of pencil for the crust (i.e., as done in red below) Pearson Education, Inc.
17 1.3A. 2. The radius of the basketball model is 0.119m (119 mm), but the actual radius of Earth is 6,371,000 m, so the ratio scale of model to actual Earth is to 6,371,000. Dividing 6,371,000 by reduces the ratio scale to 1: 53,537,815. Thus, the basketball model is 1/53,537,815th of the actual size of Earth. Fractional scale: 1/53,537,815 Ratio scale: 1:53,537, B. MODELING LANDSLIDE HAZARDS 1. If you lift one end of the ruler, then the coin slides towards the opposite end. 2. The coin did not slide off of the ruler at the very second you started to lift one end of the ruler, because there was friction between the coin and the ruler. 3. The coin start sliding when the force of gravity overcame the friction between coin and ruler. 4. REFLECT & DISCUSS: When students describe how they would modify the ruler and coin model, their answers will vary widely. Most will use different solid materials, such as rocks on a piece of marble. Some will introduce water. Some will introduce wind. Some will want to measure values and graph results. ACTIVITY 1.4: Measuring and Determining Relationships 1.4A. The mathematical conversions (using the table on laboratory manual page xi) are: miles x km/mi = kilometers (or rounded to 16.1 km) foot x m/ft = meters (or rounded to 0.3 m) kilometers x 1000 m/km = 16,000 meters meters x 100 cm/m = 2500 centimeters ml x cm 3 /ml = 25.4 cm liters x 1000 cm 3 /L = 1300 cm 3 1.4B. 1. 6,555,000,000 = x = x C. Students should be able to use a metric ruler (cut from GeoTools sheet 1 or 2) to draw a line segment like this one that is exactly 1 cm long. 1 cm 1.4D. Students should be able to use a metric ruler to draw a square that is exactly 1 cm long by 1 cm wide. [Note that this is a two-dimensional shape called a square centimeter, or cm 2.] 1 cm 1 cm 2015 Pearson Education, Inc. 17
18 1.4E. Students will have some difficulty drawing a three-dimensional cubic centimeter on two-dimensional paper because the dimensions must be distorted to give the drawing its perspective view. However, their drawing of a cubic centimeter should be as close as possible to actual size. Some students will try to trace the cubic centimeter in Figure 1.11B (which is correct, but must be traced exactly). 1.4F. Students should explain a procedure similar to this one and determine that water has a density of about 1 g/cm 3 : a. Fill a small graduated cylinder about halfway with water and record this starting volume of water in the cylinder. The graduated cylinder will probably be graduated in ml (which equals cm 3 ), so students should record the starting volume of water in cm 3. b. Weigh the graduated cylinder of water from step a and record the starting mass of water in grams. c. Add a small amount of water to the graduated cylinder and: Read and record this ending volume of water. Weigh and record this ending mass of water. d. Use the following mathematical formula to determine the density of water: Ending mass of water (g) starting mass of water (g) = about 1 g/cm 3 Ending volume of water (cm 3 ) starting volume of water (cm 3 ) 1.4G. Students will determine that their clay has a density greater than 1 g/cm 3. Most brands are between 2 g/cm 3 and 4 g/cm 3. There are two main methods/procedures that students use to determine this. Method 1 procedures: a. Construct a cubic centimeter of clay (1 cm 3 of clay). b. Weigh the cm 3 of clay in grams. This is the grams per cubic centimeter (density) of the clay. Method 2 procedures: a. Weigh a small lump of clay (that will fit in a graduated cylinder) and record its mass in grams. b. Fill the graduated cylinder about halfway with water and record the exact starting volume of water in cubic centimeters. c. Place the lump of clay into the water (do not splash) of the graduated cylinder and record this ending volume of water in cubic centimeters. d. Determine the volume of the clay by subtracting the starting volume of water in the graduated cylinder (b) from the ending volume of water in the graduated cylinder (c). e. Determine the density of the clay by dividing the mass of the clay sample (a) by the volume of the clay sample (d) Pearson Education, Inc.
19 1.4H. 1. Clay sinks in water because it is more dense than water (it has a density greater than 1 g/cm 3 ). 2. Some students will try to flatten the clay into a sheet that can float on the surface tension of the water. Other students will try to make a boat or a clay sphere. (If students are having great difficulty getting the entire lump of clay to float, then you can ask them to consider how the Navy gets steel to float i.e., it makes the steel into ship shapes.) 3. When students eventually make a ship shape (or sphere) and get their clay to float, then they should realize that the clay floated because it took on a new shape with a larger volume. This decreased the density of the clay and increased its buoyancy. 1.4I. Reflect and Discuss: The hydrosphere (liquid water) is less dense than the lithosphere, so it sits on top of the lithosphere. The atmosphere is the least dense of them all, so it occurs above them. In summary, the spheres are most dense at Earth's center and less dense with position away from Earth's center. Many students will draw this relationship and label the spheres. 1.4J. RATES: 1. a. 1.6 km x 1,000,000 mm/km = 1,600,000 mm 6 million years = 6,000,000 yr So: 1,600,000 mm 6,000,000 yr = mm/yr = x 10-1 mm/yr b mm/yr times the age of the student in years = answer C 3.9 km = C/km 1.4K. Single Line Graph 2015 Pearson Education, Inc. 19
20 1. The amount of CO 2 in the atmosphere at Mauna Loa Observatory, Hawaii has increased every decade since The values for carbon dioxide increase as the years increase, and the line has a positive slope. 1.4L. Bar Graph 1.4M. Two-line Graph 1. The relationship revealed in this graph is that there is a close correlation between atmospheric carbon dioxide (ppmv) and global temperature. When carbon dioxide levels are, the temperature is high. When carbon dioxide is low, then the temperature is low. Over the past 400,000 yr, both factors have risen and fallen together in cycles lasting about 100,000 yr. Carbon dioxide concentrations did not exceed 300 ppmv in any of those natural cycles or drop below 180 ppmv in any of those natural cycles. 1.4N. Reflect and Discuss Graph K and M show that since at least 1962, carbon dioxide levels have been higher than at any time in the past 400,000 years and reached a level of 393 ppmv in Graph L shows that the rate of carbon dioxide increase is also rising. One can expect the level and rate to increase in the future by extrapolating the graphs into the future. Also, based on Graph M, the levels of carbon dioxide in our atmosphere are greater than at any time in the past 400,000 years. Graph M also shows that global temperature and carbon dioxide concentrations rise and fall together, so one can infer that abnormally high global temperatures will accompany the abnormally high carbon dioxide levels of the future Pearson Education, Inc.
21 ACTIVITY 1.5: Density, Gravity, and Isostasy 1.5A. Student answers will vary according to the type of wood. However, students should realize that they can determine the mass of the wood block by weighing it in grams (g). They should be able to determine the volume of the wood block by using a ruler to measure its three linear dimensions in cm, and then multiplying the dimensions together to find the volume in cubic centimeters (cm 3 ). The density of the wood block is its mass in grams divided by its volume in cubic centimeters. 1.5B. Bear in mind that the proportions of wood above and below the waterline will vary according to the type of wood. Pine floats higher than walnut. Exact measurements recorded by students will also vary according to type of wood and size of the block. 1.5C. The exact form of equations will vary from student to student. The common form is: H below = (Ρ wood Ρ water ) H block 1.5D. The exact form of equations will vary from student to student. Using the equation above (answer to Question 17), the common form would be: H above = 1 [ (Ρ wood Ρ water ) H block ] 1.5E. The density of water ice (in icebergs) is g/. The average density of (salty) ocean water is g/. 1. % below = (0.917 g/cm g/cm 3 ) 100% = 89.5% 2. % above = 100% [(0.917 g/cm g/cm 3 ) 100%] = 10.5% 3. Students will generally find that their grid estimations of the percentages of the iceberg below and above sea level are consistent with their calculations above. 4. As the top of the iceberg melts, its submerged base will rise to establish a new isostatic equilibrium. 1.5F. Where mountains have been eroded, their roots are still rising very slowly, so ancient shorelines become elevated above the levels where they originally formed Pearson Education, Inc. 21
22 ACTIVITY 1.6: Isostasy and Earth s Global Topography 1.6A. Student values for the density of pieces of basalt that they personally analyze will vary from about 2.9 g/cm 3 to 3.3 g/cm 3. However, they should still determine that the average density of all 10 basalt samples is about 3.1 g/cm B. Student values for the density of pieces of granite that they personally analyze will vary from about 2.7 g/cm 3 to 3.2 g/cm 3. However, they should still determine that the average density of all 10 granite samples is about 2.8 g/cm C. 1. H above = 5 km [ (3.1 g/cm g/cm 3 ) 5 km ] = 0.3 km 2. H above = 30 km [ (2.8 g/cm g/cm 3 ) 30 km ] = 5.0 km km 0.3 km = 4.7 km 4. The calculated value of 4.7 km in part c is close to the actual difference between the average height of the continents and the average depth of the oceans on the hypsographic curve in Figure D. Reflect and Discuss: Earth has a bimodal global topography because its granitic continental blocks of lithospheric rock have an average density that is less than the average density of basaltic sea floor rocks. Thus, on average, the continental blocks sit about 4.53 kilometers higher in the mantle than the basaltic blocks. Oceans cover the basaltic blocks, but the tops of continental blocks remain above sea level. 1.6E. Reflect and Discuss: As a mountain forms, it establishes a level of isostatic equilibrium in the denser mantle a sort of mantle line (like the waterline on an iceberg). In other words, most of the mountain is a submerged root, just as most of an iceberg is its root below sea level. As a mountain is eroded, its root rises to establish a new level of isostatic equilibrium. 1.6F. Reflect and Discuss: Students can take and defend any inference, but the best and most correct inference is one that is supported by data and good logic. The most correct proposal (according to their work in this laboratory) is a compromise hypothesis stating that: Blocks of Earth s crust (actually lithosphere) have different densities (Pratt) and different thicknesses (Airy), so they sink to different compensation levels Pearson Education, Inc.
23 LABORATORY TWO Plate Tectonics and the Origin of Magma BIG IDEAS: Tectonics is the study of global processes that create and deform lithosphere. Plate tectonics is the theory that Earth s lithosphere is broken into dozens of plates (thin curved pieces). The plates are created and destroyed, move about, and interact in ways that cause earthquakes and create major features of the continents and ocean basins (like volcanoes, mountain belts, ocean ridges, and trenches). THINK ABOUT IT (Key Questions): Is the lithosphere beneath your feet really moving? (Activity 2.1) What causes plate tectonics? (Activities 2.2, 2.3) How are plate boundaries identified? (Activities 2.4, 2.5, 2.6, 2.7) How and at what rates does plate tectonics affect earth s surface? (Activities 2.4, 2.5, 2.6, 2.7) What are hot spots, and how do they help us explain plate tectonics? (Activity 2.8) How and where does magma form? (Activity 2.9) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities computer with Internet access (Activities 2.1 and 2.8 only) laboratory notebook pencil with eraser metric ruler (cut from GeoTools sheet 1 or 2) protractor (cut from GeoTools sheet 4) calculator plastic ruler or popsicle stick (Activity 1.2) colored pencils (red and blue) visual estimation of percent chart (cut from GeoTools sheet 1 or 2) INSTRUCTOR MATERIALS (Check off items you will need to provide.) ACTIVITY 2.1: Plate Motion Inquiry Using GPS Time-Series extra metric rulers (for students who forgot them) 2015 Pearson Education, Inc. 23
24 ACTIVITY 2.2: Is Plate Tectonics Caused by a Change in Earth s Size? extra metric rulers (for students who forgot them) ACTIVITY 2.3: Lava Lamp Model of Earth extra blue pencils (for students who forgot them) extra red pencils (for students who forgot them) extra plastic rulers or popsicle sticks, so each student has one Silly Putty TM lava lamp (turned on at least one hour ahead of time) and/or lava lamp video clip ACTIVITY 2.4: Paleomagnetic Stripes and Seafloor Spreading extra metric rulers (for students who forgot them) ACTIVITY 2.5: Atlantic Seafloor Spreading extra metric rulers (for students who forgot them) extra blue pencils or pens (for students who forgot them) extra red pencils or pens (for students who forgot them) ACTIVITY 2.6: Using Earthquakes to Identify Plate Boundaries extra metric rulers (for students who forgot them) extra red pencils or pens (for students who forgot them) ACTIVITY 2.7: San Andreas Transform-Boundary Plate Motions extra metric rulers (for students who forgot them) ACTIVITY 2.8: Hot Spots and Plate Motions extra metric rulers (for students who forgot them) ACTIVITY 2.9: The Origin of Magma extra metric rulers (for students who forgot them) hot plate (one per group of students) sugar cubes (two per group of students) dropper with water or dropper bottle (one per group of students) aluminum foil (one sheet per group of students) or foil baking cups (two per group of students) crucible tongs (one per group of students) permanent felt-tip marker (one per group of student) INSTRUCTOR NOTES AND REFERENCES 1. Metric and International System of Units (SI): refer to laboratory manual page xi. 2. Mathematical conversions: refer to laboratory manual page xii Pearson Education, Inc.
25 3. To model Kinetic Theory, place small plastic or glass marbles in a clear plastic box or tray on an overhead projector. Hold the model still and elevated at one end, so the marbles form a close-packed array resembling a crystalline solid structure. Vibrate the model slightly to model a rise in kinetic energy and to start moving the marbles apart, as if melting is initiating. Vibrate the model more to model a greater rise in kinetic energy and to cause all of the marbles to move about independently, as if total melting or vaporization has occurred. (To model crystallization by decreasing kinetic energy, repeat these tasks in reverse.) Note: be sure to remind students that plumes of Earth s mantle are rock, not liquid magma or lava. 4. One lava lamp, or two, or three? Most lava lamps must be lighted for at least one hour before they exhibit active and obvious convection. It helps to have two or more lamps that have been turned on at different times, so the lava (wax) has varying amounts of kinetic energy. This helps students understand kinetic theory and how unequal amounts of heating affect the development and rate of convection. A lava lamp video clip is provided on the IRC-DVD. Note: be sure to remind students that Earth s mantle is rock, not liquid magma or lava. 5. Decompression melting. To help students visualize decompression melting, have them mix corn starch and water to make a corn starch suspension. Then have them try to roll some of the suspension into a ball and watch the suspension flow through their fingers. So long as the suspension is under pressure (i.e., while it is being rolled into a ball), it remains in a solid-like state. When the suspension is not under pressure (i.e., when a ball of suspension is placed on the palm of a hand), it flows in a liquid state. This is NOT decompression melting, but it helps students understand that pressure can prevent flowing even in materials that are normally fluid. 6. To model mantle plumes and hot spots, make a model of Earth s compositional layering first by placing clear corn syrup in a clear plastic cup (to represent Earth s mantle) and then by adding a few mm of water on top of it (to represent Earth s crust). To prepare material for a mantle plume, heat a small amount of corn syrup (with a few drops of red food coloring) on a hot plate. Fill a dropper with the hot red corn syrup, and then squeeze some of it out onto the bottom of the plastic cup containing the cool syrup and water. Watch as the hot red corn syrup rises through the cooler corn syrup to form a long narrow plume and a pool of red syrup just beneath the water (crust). This is especially useful for having students entertain ideas about the origin of hot spots. 7. Flux melting. In the smelting industry, the term flux refers to materials such as fluxstone that are added to raw ore in order to lower the fusion (melting) temperature and produce slag. Experimental petrology has demonstrated that water lowers the fusion temperature of some minerals commonly found in granite, basalt, and peridotite, thereby initiating partial melting at lower, wet solidus temperatures Pearson Education, Inc. 25
26 8. Water in Earth's mantle. For information on recycling of water into Earth's mantle, refer to: C. Meade and R. Jeanloz Deep-focus earthquakes and recycling of water into Earth's mantle. Science 252: San Andreas fault slip rate. For a published estimate of the recurrence interval for very large earthquakes along the San Andreas fault north of San Francisco (221 +/ 40 yr), see: T.M. Niemi and N.T. Hall Late Holocene slip rate and recurrence of great earthquakes on the San Andreas fault in northern California. Geology 20: During the recurrence interval, the accumulated strain would be about 3.2 m (10 ft). However, Niemi and Hall (1992) also estimated that the Late Holocene rate of movement on the fault is about 2.4 cm/yr. For a published estimate of the recurrence interval for very large earthquakes along the San Andreas fault zone 70 km northeast of Los Angeles, California, see: T.E. Fumal, S.K. Pezzopane R.J. Weldon II, and D.P. Schwartz A 100-Year Average Recurrence Interval for the San Andreas Fault at Wrightwood, California. Science 259: They calculated a recurrence interval of about 100 years, a slip rate of about 2.5 cm per year, and a slip per very large earthquake of about 4 meters. LAB 2 ANSWER KEY ACTIVITY 2.1: Plate Motion Inquiry Using GPS Time-Series 2.1A. Answers will vary. For example, although most students in the United States live on the North American Plate, some live on the Pacific Plate. 2.1B. Answers will vary and must be checked on an individual basis Pearson Education, Inc.
27 2.1C. Students will have some difficulty generalizing about the general motion of North America and South America, but most will agree on the general motion of Africa and Europe. 2.1D. Reflect and Discuss: Most discussions of plate tectonics describe how the Atlantic Ocean is developed around a divergent plate boundary (Atlantic Mid- Ocean Ridge), so North America and South America are moving away from Europe and Africa. The generalized plate motion vectors above (black arrows) seem to confirm that. Therefore, students generally use the above map to say that it supports the Plate Tectonic Theory. ACTIVITY 2.2: Is Plate Tectonics Caused by a Change in Earth s Size? 2.2A Pearson Education, Inc. 27
28 2.2B. 2.2C Some students will notice that the percentages of convergent and divergent boundaries is nearly equal and that the percentage of transform boundaries is a bit less. However, most will conclude that there is roughly one-third of each kind of plate boundary and that Earth s size is staying about the same ,000,000 km km 2 /yr = 150,000,000 yr (or 1.5 x 10 7 yr) 2.2D. Reflect and Discuss: Based on the answers to questions above, there is evidence for about equal amounts of crustal compression, tension, and shear. Thus, it seems reasonable that Earth s size is not changing (i.e., Earth is staying about the same), and plate tectonics is not driven by a change in Earth s size. Some students will come to the likely conclusion that for Earth to remain the same size, there must be mantle convection, whereby lithosphere is created at divergent boundaries, recycled back into the mantle at convergent boundaries, and neither created nor recycled at transform boundaries. Most students will know about Earth s hot interior and will at least suggest that it is processes inside of Earth that are causing its change in size. Their descriptions of those processes will vary widely, and should not be graded with one strict answer in mind at this point. Their conceptions serve as working hypotheses for future parts of the lab Pearson Education, Inc.
29 ACTIVITY 2.3: Lava Lamp Model of Earth 2.3A. 1. See the completed table below. 2. Rheidity is the time it takes for a solid material under stress to lose its elasticbrittle behavior, entirely, and just permanently deform (flow) like a viscous fluid. So a rheid is a solid material that can change from viscoelastic behavior to just viscous behavior. Silly Putty has such behavior, so it is a rheid. 3. Reflect and Discuss: Brittle solid rocks of the lithosphere may exhibit viscoelastic behavior and even shatter when they exceed their elastic limit (as in an earthquake). However, when the same rocks subduct into the mantle and are subjected to intense forces over long periods of time (and are hot), they can flow as a viscous fluid. 2.3B. Students must observe a convecting lava lamp (that has been heating at least one hour) or a movie clip of a convecting lava lamp to answer these questions. 1. The lava moves from the base of the lamp to the top of the lamp, where it sits temporarily before sinking back to the bottom of the lamp. 2. Lava at the base of the lamp is heated by the light bulb. As the lava is heated, its kinetic energy level rises, which causes the lava to expand to a slightly greater volume and lower density. When the density of lava is less than the surrounding fluid, the lava rises. 3. Lava at the top of the lamp is cooling. As it cools, its kinetic energy level decreases, which causes the lava to contract into slightly less volume and higher density. When the density of lava is greater than the surrounding fluid, the lava sinks. 4. convection 2015 Pearson Education, Inc. 29
30 2.3C. 1. Earth s mantle is like a lava lamp, because: mantle rocks are unequally heated like lava in the lava lamp. mantle rocks are heated at the base of the mantle, like lava in a lava lamp is heated at the base of the lava lamp. it has warmer rocks that rise like lava in a lava lamp. it has cooler rocks that sit atop the mantle or sink back into the mantle, like the masses of cooling lava at the top of the lava lamp. 2. Earth s mantle is different from a lava lamp, because: the mantle is rock, not lava or wax. the mantle is heated by Earth s outer core, but the lava lamp is heated by a light bulb. the mantle convects more slowly (i.e., cm/year) than the lava lamp (cm/second or cm/minute). 2.3D. By comparing lab manual Figures 2.4 and 2.3, students should observe that: 1. the warmer, less dense mantle rocks (red in Figure 2.6) mostly occur beneath divergent plate boundaries and hot spots. 2. the cooler, denser mantle rocks (blue in Figure 2.6) mostly occur beneath continents. 2.3E. Reflect and Discuss: The nature and detail of student cross sections will vary, but it should be at least a labeled, simple sketch like the one below Pearson Education, Inc.
31 ACTIVITY 2.4: Paleomagnetic Stripes and Seafloor Spreading 2.4A. 1. The exact position of the modern divergent boundaries and transform faults connecting them is somewhat difficult to determine in some parts of the seafloor map, but maps should approximate the completed map below. 2. The distance from B to A is about 250 km and covers an age of about 8 million years. 250 km x 100 cm/km = cm. Therefore, the spreading rate is cm / 8,000,000 yr, which reduces to cm/yr. 3. The distance from B to C is about 190 km and covers an age of about 8 million years. 190 km x 100 cm/km = cm. Therefore, the spreading rate is cm / 8,000,000 yr, which reduces to cm/yr. 4. East of the Juan de Fuca Ridge, the rocks older than 11 million years have been subducted Pearson Education, Inc. 31
32 5. a. trench b. North American Plate c. Juan de Fuca Plate 6. Reflect and Discuss: The Juan de Fuca Plate subducts beneath the North American Plate. Water from the subducted plate enters the mantle wedge above it and lowers the melting point of the rocks. Partial melting begins, and the magmatic arc (Cascade Range) volcanoes form as magma rises towards Earth s surface. ACTIVITY 2.5: Atlantic Seafloor Spreading 2.5A. 1 and 2 2.5B. Although points B and C were together 145 million years ago, they did not spread apart at exactly the same rate on opposite sides of the mid-ocean ridge. You can tell this because distance A-B is greater than distance A-C. 2.5C. How far apart are points B and C today? ~ 4300 km km 145 million years = km/m.y. 2. There are 1000 m/km and 1000 mm/m, so there are 1,000,000 mm/km. 4,300,000,000 mm 145,000,000 yr = mm/yr OR km/1,000,000 yr 1,000,000 mm/ 1 km = mm/yr Pearson Education, Inc.
33 2.5D. Reflect and Discuss: When Africa and North America were together as part of one continent, points D and E were at the same location. They are now about 5800 to 5900 km apart (about 5850 km, depending on how students measure the distance) km km/m.y. = 195 m.y. and 5900 km km/m.y. = 199 m.y., so students should determine that Africa and North America were part of the same continent about m.y. ago (early part of the Jurassic Period according to Figure 1.3 on page 7 of the Lab Manual). 2.4E. Reflect and Discuss: = 238 yr AND 238 yr mm/yr = 7059 mm So, 7059 mm m/mm = m. Students should calculate that Africa and North America have moved apart by about 7 meters since the United States formed in ACTIVITY 2.6: Using Earthquakes to Identify Plate Boundaries 2.6A Pearson Education, Inc. 33
34 2.6B. 1. convergent 2. See the black line (solid and dashed) on the graph above. 3. Lithospheric earthquakes occur mostly in the continental lithosphere (above the black line), but they also occur at or just below the top of the subducting lithospheric plate (so long as it remains brittle) km (volcanoes above it) 5. Reflect and Discuss: The deepest earthquake plotted on the cross section occurs at 620 km (a deep focus earthquake). It is likely that this may be at or near the lower limit, below which earthquakes are not likely to occur (in relation to the subducting plate) because the plate is no longer rigid (viscoelastic) or has been assimilated into the mantle rocks around it Pearson Education, Inc.
35 ACTIVITY 2.7: San Andreas Transform-Boundary Plate Motions 2.7A. 1. There are two main bodies of rock that have been displaced along the fault, so students can use either one to calculate a rate of fault motion. The Oligocene sedimentary rocks (Os) have been displaced about 323 km since they formed 25 million years ago. Multiply 323 km by 100,000 cm/km to get a distance of 32,300,000 cm. Then, 32,300,000 cm 25,000,000 yr equals an average rate of 1.29 cm/yr. The Oligocene volcanic rocks (Ov) have been displaced about 340 km since they formed 23.5 million years ago. Multiply 340 km by 100,000 cm/km to get a distance of 34,000,000 cm. Then, 34,000,000 cm 23,500,000 yr equals an average rate of 1.45 cm/yr. 2. Based on the measurements determined above: The Oligocene sedimentary rocks (Os) were displaced 323 km, which equals 323,000 meters. 323,000 meters 5 meters per displacement equals 64,600 displacements. 25,000,000 yr 64,000 displacements of 5 meters equals years, so the average 5-meter displacement occurred once every 391 years. The Oligocene volcanic rocks (Ov) were displaced 340 km, which equals 340,000 meters. 340,000 meters 5 meters per displacement equals 68,000 displacements. 23,500,000 yr 68,000 displacements of 5 meters equals years, so the average 5-meter displacement occurred once every 346 years. Students should determine that if all displacements along the fault were 5 meters, then a 5-meter displacement occurs every 346 to 391 years. 2.7B. 1. The North American Plate (north of the red San Andreas Fault) is moving about 20 mm/yr. The Pacific Plate (south of the red San Andreas Fault) is moving about 40 mm/yr. So, the Pacific Plate is moving about twice (2 times) as fast as the Pacific Plate here Pearson Education, Inc. 35
36 2. Note the half arrows on the map (showing the relative motion of the fault) below. 2.7C. Reflect and Discuss: Absolute plate motion refers to the movement of a lithospheric plate in relation to a fixed point on Earth or the actual motion of a point on a lithospheric plate in relation to a fixed position outside the Earth (such as the movement of a plate measured relative to known fixed geographic locations determined with the GPS satellite constellation). Relative plate motion refers to the motion of one plate in relation to another, which is assumed to be in a fixed position (even though it is likely that all of the plates are moving in relation to one another). ACTIVITY 2.8: Hot Spots and Plate Motions 2.8A. 1. The Emperor and Hawaiian Islands form one continuous chain of islands that developed as the Pacific Plate moved over the Hawaiian hot spot. The Emperor Islands formed 60 to 40 million years ago, and the Hawaiian Islands have been forming from 40 million years ago to the present day. Note: You can simulate how a hot spot burns a line of volcanoes into a plate moving over it. Remove the cover from a very large (poster size) permanent black felt-tip pen and place it tip-up on a table. Hold the pen while you slowly slide a piece of white paper over the pen tip. The ink from the pen will bleed through the paper. If you do this with a very slow motion and stop periodically, then you will create a pattern of islands separated by lines Pearson Education, Inc.
37 2. The Emperor Islands is a north-south string of islands about 2300 km (230,000,000 cm) long that formed over a period of 20 million years (40 60 Ma). For this to happen, the plate had to move north over the Hawaiian hot spot from Ma at a rate of 230,000,000 cm/20,000,000 yr, which reduces to 11.5 cm/yr. 3. From 4.7 to 1.6 million years ago, the Hawaiian Islands moved northwest over the Hawaiian hot spot. The Pacific Plate moved 300 km northwest over 3.1 million years, so its average rate of motion was 30,000,000 cm 3,100,000 yr, which reduces to 9.67 cm/yr. 4. From 1.6 to 0 million years ago, the Hawaiian Islands moved northwest over the Hawaiian hot spot. The Pacific Plate moved 105 km northwest over 1.6 million years, so its average rate of motion was 10,500,000 cm 1,600,000 yr, which reduces to 6.56 cm/yr. 5. a. According to the NPOC plate motion vector, the Pacific Plate is still moving northwest over the Hawaiian hot spot, but it is now moving a bit more north than west compared to its motion over the past 40 million years. 5. b. The vector data for this question should be in mm/yr, not cm/yr. You should zoom in on the NPOC station at the JPL-NASA GPS Time Series website and show students that the actual vector data is mm/yr. If students use the data in cm/yr, then the sum of ( cm/yr) 2 plus ( cm/yr) 2 equals 2, cm/yr 2. The square root of 2, cm/yr 2 equals cm/yr., so they will determine that the NPOC station is moving very fast ( cm/yr). However, the correct units are mm/yr, so the NPOC station is actually moving northwest at a rate of mm/yr, which reduces to cm/yr. (This plate motion was for the years 2007 to 2013.) 2.8B. Reflect and Discuss: From 60 to 40 million years ago, the Pacific Plate moved north at a rate of about 11.7 cm/yr. Since 40 Ma, the plate has moved northwest, but its rate has slowed since that time. The plate moved 9.67 cm/yr from 4.7 to 1.6 million years ago and slowed to 6.56 cm/yr over the past 1.6 million years. [If the NPOC data were analyzed correctly (see item 5b above), then the NPOC site indicates current plate motion of just cm/yr.] 2.8C. 1. Yellowstone Park is volcanically active at the present time. It is part of a line of volcanic calderas that have formed since 13.8 million years ago and are successively older with distance from Yellowstone Park. Therefore, it seems that Yellowstone Park is located over a hot spot, and the North American Plate has moved west-southwest over the hot spot for at least the past 13.5 million years Pearson Education, Inc. 37
38 2. Over the past 10.5 million years, the North American Plate moved about 230 km over the Yellowstone hot spot. Therefore, its rate of motion was 23,000,000 cm 10,500,000 yr, which reduces to 2.19 cm/yr. 3. Reflect and Discuss: Hot spots help us understand plate tectonic processes and rates, because they are fixed points on Earth. This means that they can be used as a fixed reference point to determine the absolute motion of plates that have moved over them. ACTIVITY 2.9: The Origin of Magma 2.9A. 1. about 750 C 2. about 1000 C 3. solid (It is left of the solidus in the field labeled 100% solid peridotite rock.) 4. It would partially melt. If you move point X to the right until it is below the temperature of 1750 C, then it is located in the field of partial melting, between the solidus and liquidus. 5. It would melt completely because it would be located in the field to the right of the liquidus, which is labeled 100% liquid magma. 2.9B. 1. about 40 km and 13,000 atm 2. decompression melting 3. Decompression melting could occur where a plume of hot mantle peridotite rises to a shallower depth and lower pressure where melting can occur. This may be happening along divergent plate boundaries (like ocean ridges and rifts) and at hot spots. 2.9C. Reflect and Discuss: To begin partial melting, the peridotite at point X in Figure 2.8 must be uplifted to a depth of about 40 km (and a pressure of about 13,000 atm) or else it must be heated to about 1450 C. 2.9D. 1. The wet sugar cube melted first. 2. water 3. The solidus, liquidus, and all fields would move to the left (to lower temperatures). 4. subduction zones Pearson Education, Inc.
39 2.9E. Reflect and Discuss: 1. divergent plate boundary 2. decompression melting 3. A mass/plume of hot mantle peridotite rises close to Earth s surface, where it encounters lower pressure and melts to form basaltic magma. The magma erupts along the oceanic ridge, where it pushes the existing rock plate apart. This pushes the plates and starts the process of seafloor spreading. 2.8F. Reflect and Discuss: 1. convergent plate boundary 2. flux melting 3. Wet seafloor basalt subducts beneath the less dense continental edge of an adjacent plate. The basalt dehydrates and hydrates the base of the continental crust. Flux melting causes formation of magma, which rises to form a line of volcanoes (volcanic arc) Pearson Education, Inc. 39
40 LABORATORY THREE Mineral Properties, Identification, and Uses BIG IDEAS: Minerals comprise rocks and are described and classified on the basis of their physical and chemical properties. Every person depends on minerals and elements refined from them, but the supply of minerals is nonrenewable, and the magnitude of their use may be unsustainable. THINK ABOUT IT (Key Questions): What are minerals and crystals, and how are they related to rocks and elements? (Activity 3.1) How and why do people study minerals? (Activities 3.2, 3.3, 3.4) How do you personally depend on minerals and elements extracted from them? (Activities 3.4, 3.5) How sustainable is your personal dependency on minerals and elements extracted from them? (Activities 3.5, 3.6) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser calculator cleavage goniometer cut CAREFULLY and EXACTLY from GeoTools sheet 1 mineral samples with identifying numbers/letters (or provided by instructor) other mineral analysis tools (see below, or provided by instructor) hand lens (optional, or provided by instructor) computer or other electrical device with Internet (Activity 3.6 only) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 3.1: Mineral and Rock Inquiry none Pearson Education, Inc.
41 ACTIVITY 3.2: Mineral Properties (optional) 1 set of samples of amethyst, rose quartz, milky quartz, and flint for each group for part D (optional) 1 set of samples of sucrose (table sugar), epsomite (epsom salt), and halite (table salt) for each group for part K ACTIVITY 3.3: Determining Specific Gravity (SG) 1 set per group of numbered/lettered samples of three different minerals with relative densities that students can distinguish by hefting (for part B) specific gravity equipment (one set per group): 500 ml graduated cylinder, gram balance, wash and/or dropper bottle, water mineral set (one per group): three minerals samples that will easily fit into the 500 ml graduated cylinder. Choose from native sulfur, quartz, fluorite, garnet, barite, pyrite, and galena, which occur in the identification table in part D (p. 82). paper towels ACTIVITY 3.4: Mineral Identification, and Uses 1 set per group of mineral samples with identifying numbers/letters (or obtained by student) 1 set per group of mineral analysis tools (one set per group of students, or else obtained by students): steel masonry nails, wire nails, glass plate, streak plates, copper pennies and/or nails, small magnet) dropper bottle of dilute (1 3%) hydrochloric acid, HCl (one per group of students) paper towels hand lens (one per group of students, or provided by student) ACTIVITY 3.5: The Mineral Dependency Crisis none ACTIVITY 3.6: Urban Ore (optional) electronic devices with Internet access, so students can search for the current New York spot gold price INSTRUCTOR NOTES AND REFERENCES 1. Mineral samples must be marked with an identifying number or letter so they can be organized on the Mineral Data Charts (Activity 3.4). 2. Glass plates should be thick glass with rounded edges so students cannot cut themselves. Be sure to demonstrate for students that they must rest the glass plate flat on a table and only then attempt to scratch a mineral against it for the hardness test. Inform students that they should never hold the glass plate in one hand and scratch it with a mineral sample held in the other hand. (The glass often breaks and the student may be injured.) 2015 Pearson Education, Inc. 41
42 3. Acid test. The dilute hydrochloric acid (HCl) used to test for carbonate minerals should be about 3% HCl. Stronger solutions may cause dolomite to effervesce even before it is powdered. Be sure to inform students that they should place a sample on a paper towel to do the acid test and that they should rinse the sample after the test. They should not drop the acid onto their clothing or skin. Their skin may peel and their clothing may develop holes (after washing it several times) from exposure to the acid solution. 4. Taste test. Be sure to have students ask you if it is safe to do a taste test for halite before they do the test. Some minerals are toxic and/or have sharp edges that could harm students. 5. Fingernail hardness. Some students may use nail hardeners or have artificial nails. Treated or artificial nails generally have a hardness slightly greater than 2.5, but generally less than 3 on the Mohs scale. 6. Cleavage goniometer. Encourage students to cut out their cleavage goniometers as carefully and exactly as possible. Also encourage students to measure cleavage angles as exactly as they can on several parts of each mineral sample. All mineral crystals have imperfections, so cleavage angles are seldom perfect (but they are often close to perfect). 7. Students require a computer or other electrical device with Internet access for Activity 3.6, so they can search to find the New York spot gold price in U.S. dollars (USD) per ounce. LAB 3 ANSWER KEY ACTIVITY 3.1: Mineral and Rock Inquiry 3.1A. 1. Some students will report that they see no minerals crystals in the sample, because they see no crystal faces. Others will report 3 or many. They should be able to recognize two different kinds of minerals in the sample: a gold colored mineral and a white mineral. 3.1A. 2. Students should recognize that this sample is one single crystal of one kind of mineral that varies from transparent and colorless to translucent and gray. 3.1A. 3. Students should be able to recognize that there are many mineral crystals and two kinds of minerals in this sample: a transparent yellow mineral and an opaque gray mineral Pearson Education, Inc.
43 3.1A. 4. Students should recognize that there are many crystals of three or four different kinds of minerals: glossy black, pink/orange, white, and gray minerals. Some students do not recognize the gray and white minerals as different. 3.1B. Sample one has crystals of a valuable element: gold. 3.1C. Reflect and Discuss: A rock is a piece of Earth s geosphere. One could also say that rocks are the solid materials that make up most of Earth, our Moon, and the other rocky planets of our solar system. Most rocks are made of one or more mineral crystals (of one or more kinds of minerals). ACTIVITY 3.2: Mineral Properties 3.2A. 1. a mirror: metallic 2. butter: nonmetallic 3. ice: nonmetallic (vitreous) 4. a rusty nail: nonmetallic (earthy) 3.2B. 1. salt: white (as in table salt) 2. wheat: brown or gold (as in whole wheat flour) or white (as in bleached wheat flour) 3. pencil lead: gray or black 3.2C. 1. quartz in Figure 3.1B: hexagonal pyramids (or short hexagonal prisms and pyramids) 2. native copper in Figure 3.6: dendritic 3.2D. var. flint (black) var. rose quartz (transparent to translucent gray) var. milky quartz (white) var. amethyst (purple to magenta) 2015 Pearson Education, Inc. 43
44 3.2E. 1. soft 2. Hardness is , because the mineral is harder than 4.5 (wire nail) and softer than 5.5 (masonry nail). 3. apatite 3.2F. 1. Hardness is 3.5 4, because the mineral is harder than 3.0 (calcite) and softer than 4.5 (wire nail). 2. fluorite 3.2G. Hardness is 6, because it scratches glass (i.e., is harder than 5.5) but does not scratch the streak plate (is softer than 6.5). 3.2H. 1. Hardness is less than 4.5, because it is scratched by the wire nail. 2. The angles are 75 degrees and 105 degrees, so this is called rhombohedral cleavage (breaks along rhombohedrons). 3. calcite 4. calcium carbonate: CaCO 3 5. used to make antacid tablets, fertilizer, cement, ore of calcium 3.2I. 27 g 10.4 cm 3 = density of 2.6 g/ cm 3, so SG = 2.6 Students should realize that specific gravity (SG) is the ratio of the density (in g/ cm 3 ) of a substance divided by the density of water. Since water has a density of 1 g/cm 3, the units cancel out. Thus, SG is the same number as the density (in g/cm 3 ), but without any units. 3.2J. 1. dendritic 2. hexagonal crystal system: The crystals are six-sided, and the six points occur along three axes of equal length in the same plane of the crystal structure. 3. Ice crystals (snowflakes) have different habits, because they form at different temperatures over different lengths of time. 3.2K. 1. Sucrose (table sugar) belongs to the monoclinic crystal system, because it forms tabular crystals (tablets) with a parallelogram-shaped cross section as pictured in Figure 3.5 (page 79) Pearson Education, Inc.
45 2. Epsomite (Epsom salt) belongs to the orthorhombic crystal system, because it forms orthorhombic prisms. The horizontal axis of Epsomite crystals is rectangular, but may appear square to students. Even so, students should be able to match up the Epsomite crystal shapes to Figure 3.5 (page 79). NOTE: In the first printing of this edition of the lab manual, the orthorhombic rectangular cross section was drawn as a square rather than a rectangle (it should be slightly rectangular). This error was corrected in successive printings of this 9th edition. 3. Halite (table salt) belongs to the cubic crystal system, because it forms crystals with cubic shapes. ACTIVITY 3.3: Determining Specific Gravity (SG) 3.3A. The boxes are the same size, so they vary only in mass. The box with the greater mass of cereal inside feels heavier if you heft the boxes. 3.3B. Answers will vary according to the letters/numbers and relative densities of the samples that you provide for students to heft. 3.3C. Convert kilograms to grams: kg 1000 g/kg = 453 grams Calculate the volume of the box: 20 cm 25 cm 5 cm = 2500 cm g 2500 cm 3 = g/cm 3 3.3D. Reflect and Discuss: Answers will vary widely according to each student s/group s results and the minerals used to analyze. However, nearly all students/groups conclude that they need to be more exact in their work. ACTIVITY 3.4: Mineral Identification and Uses Completed Mineral Data Charts will vary according to the mineral samples that you have assigned your students to analyze. Students must refer to the Mineral Identification Procedures in the lab manual, unless you direct them to do otherwise Pearson Education, Inc. 45
46 ACTIVITY 3.5: The Mineral Dependency Crisis 3.5A The United States would probably not be able to manufacture cell phones if a world crisis prevented it from importing minerals and elements, because the United States has 100% import reliance on some of the minerals/elements that it needs to make the phones (fluorite, graphite, sphalerite) and high import reliance on others (bauxite, barite, silver). 3.5B. Answers vary widely according to the student. 3.5C. Reflect and Discuss: Just as the United States must import many minerals/elements that it needs, so do many other countries. As demand increases and supply decreases, and with increasing political instability in many parts of the world, the United States will probably find it difficult to sustain its 2012 levels of net import reliance on minerals and selected commodities of Figure Pearson Education, Inc.
47 ACTIVITY 3.6: Urban Ore 3.6A. 1. a. NY spot gold price per ounce will vary from day to day. b g/ton of ore g/ozt = ozt of gold per short ton of ore c. Using a NY spot gold price of $1200 per ounce (ozt): ozt/short ton of ore x $1200/ozt = $ d. $640/ozt x ozt = $65.28 e. $122 minus $65 = $57 3.6B oz/16.00 oz/lb = lb/phone (2000 lb/ton) lb/phone = 8097 phones/ton phones/ton x g = grams/ton grams 31.1 g/ozt = ozt 4. Using a NY spot gold price of $1200: ozt x $1200 = $ C. Reflect and Discuss: Student answers will vary, but most students focus on recycling of electrical devices. The more that materials are recycled/reused, the less has to be mined (which is good for managing the environment) or imported (which is good for sustaining supply) Pearson Education, Inc. 47
48 LABORATORY FOUR Rock-Forming Processes and the Rock Cycle BIG IDEAS: Rocks can be classified as igneous, sedimentary, or metamorphic on the basis of their present composition and texture and how they formed. The rock cycle model explains how all rocks can be formed, deformed, transformed, melted, and reformed as a result of environmental factors and natural processes that affect them. THINK ABOUT IT (Key Questions): What are rocks made of, and where and how do they form? (Activities 4.1, 4.2, 4.3) How are a rock s composition and texture used to classify it as igneous, sedimentary, or metamorphic? (Activity 4.4) How are rocks formed, deformed, transformed, melted, and reformed as a result of environmental factors and natural processes of the rock cycle? (Activity 4.5) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser colored pencils mineral identification materials (or provided by instructor, see below) hand-held magnifying lens (optional) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 4.1: Rock Inquiry none ACTIVITY 4.2: What are Rocks Made Of? none Pearson Education, Inc.
49 ACTIVITY 4.3: Rock-Forming Minerals (optional, per group) set of rock-forming minerals numbered same as the 15 minerals on Worksheet 4.3 (optional, per group) set of mineral analysis tools ACTIVITY 4.4: What is Rock Texture? (optional, per group) set of rocks numbered same as the 15 minerals on Worksheet 4.4 ACTIVITY 4.5: Rocks and the Rock Cycle Model extra colored pencils (two colors: for students who forgot them) LAB 4 ANSWER KEY ACTIVITY 4.1: Rock Inquiry 4.1A. Reflect and Discuss: This is an inquiry-based activity, and knowledge/ability to analyze and interpret this rock will vary greatly among students. Students should recognize that the rock has many rounded holes, or bubbles, and try to infer how they may have formed. A few students may call the rock a cinder and describe how cinders form. 4.1B. Reflect and Discuss: This is another inquiry-based activity, and knowledge/ability to analyze and interpret this rock will vary greatly among students. Students should recognize that the rock has many animal shells within it and try to infer how they ended up inside a rock. ACTIVITY 4.2: Rock Inquiry 4.2A. In situ ( in place ) mineral grains are present in the rock where they originally formed. Examples are mineral crystals newly formed from cooling of lava or magma (in igneous rocks), crystals newly formed or recrystallized in rock or hot watery solutions under conditions of intense heat and pressure or (in metamorphic rocks), or as newly formed crystals precipitated from evaporating surface or groundwater (in sedimentary rocks). Detrital mineral grains are not in situ. They did not form where they are now found, are not intergrown, and do not lock together to form the rock. They were removed from the place or rock where they originally formed and were moved by 2015 Pearson Education, Inc. 49
50 wind, water, ice, organisms, and/or gravity to a new place. Examples are pebbles and sand grains in sedimentary and metamorphic rocks. 4.2B. 1. gravel, bioclasts 2. clay 3. gravel, clasts, detrital minerals 4. mineral grains (in situ) 5. silt 6. clasts (rock fragments); gravel, sand, silt 7. sand, clasts (detrital minerals--quartz) 8. mineral grains (in situ) 9. glass ACTIVITY 4.3: Rock-Forming Minerals 4.3A. 1. olivine (transparent to translucent green) 2. serpentine (opaque green) 3. kaolinite (white to pale brown clayey mass) 4. muscovite (white to brown mica) 5. chlorite (notice the green color) 6. biotite (glossy black mica) 7. gypsum (can be scratched with a nail or your fingernail) 8. potassium feldspar (orthoclase) 9. plagioclase feldspar 10. halite (cubic cleavage) Pearson Education, Inc.
52 ACTIVITY 4.5: Rocks and the Rock Cycle Model 4.5A Pearson Education, Inc.
53 4.5B. Completed chart for samples in Figure C. Reflect and Discuss: More than one answer is possible Pearson Education, Inc. 53
54 LABORATORY FIVE Igneous Rocks and Processes BIG IDEAS: Igneous rocks form wherever magma or lava cool to a solid state. The composition and texture of igneous rock samples, and the shapes of bodies of igneous rock, can be used to classify them and infer their origin. Lava and igneous rock-forming processes can be observed at volcanoes, which occur along lithospheric plate boundaries and hot spots, are linked to underground bodies of magma, and can pose hazards to humans. THINK ABOUT IT (Key Questions): What do igneous rocks look like? (Activity 5.1) What are igneous rocks composed of? (Activities 5.2, 5.3) How is composition used to classify and interpret igneous rocks? (Activities 5.2, 5.3) What are igneous rock textures? (Activities 5.4, 5.5) How is texture used to classify and interpret igneous rocks? (Activities 5.4, 5.5) How are rock composition and texture used to classify, name, and interpret igneous rocks? (Activities 5.6, 5.7, 5.8) How can the shapes of bodies of igneous rock be used to classify them and infer their origin? (Activity 5.9) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser igneous rock samples with identifying numbers/letters (or provided by instructor) chart for visual estimation of percent (cut from GeoTools sheet 1 or 2) hand-held magnifying lens (optional) metric ruler (cut from GeoTools sheet 1 or 2) mineral analysis tools (see below, or provided by instructor) INSTRUCTOR MATERIALS (Check off items you will need or provide.) Note: One same set of numbered igneous rock samples should be used for Activities 5.4, 5.5, and Pearson Education, Inc.
55 ACTIVITY 5.1: Igneous Rock Inquiry (optional): a set of igneous rock samples for each group ACTIVITY 5.2: Minerals That Form Igneous Rocks (optional, per group) set of rock-forming minerals numbered same as the eight minerals on Worksheet 5.2 (optional, per group) set of mineral analysis tools ACTIVITY 5.3: Estimate Rock Composition scissors for students to cut out Visual Estimation of Percent Chart from GeoTools 1 or 2 at the back of the lab manual ACTIVITY 5.4: Glassy and Vesicular Textures of Igneous Rocks Materials per group or demonstration: granulated sugar (~50 ml or 1/8 cup) hot plate small metal sauce pan with handle or 500 ml Pyrex beaker and tongs water (~50ml) safety goggles for students heating sugar solution aluminum foil (about 1 square foot) collection of numbered igneous rock samples (same set as will be used in Activities 5.5 and 5.8) hand lens ACTIVITY 5.5: Crystalline Textures of Igneous Rocks extra metric rulers (for students who forgot them) hand lens (at least one per group of students) collection of numbered igneous rock samples (same set as used in Activities 5.4 and 5.8) ACTIVITY 5.6: Rock Analysis, Classification, and Origin (optional) rock samples similar to those pictured on Worksheet 5.6 ACTIVITY 5.7: Thin Section Analysis and Bowen s Reaction Series none ACTIVITY 5.8: Analysis and Interpretation of Igneous Rocks collection of numbered igneous rock samples (same set as used in Activities 5.4 and 5.5) extra metric rulers (for students who forgot them) mineral analysis tools (or obtained by students): pocket knife or steel masonry nails, wire nails, glass plates, streak plates, copper pennies, small magnets (one set per group of students) hand-held magnifying lens (one per group of students) charts for visual estimation of percent (cut from GeoTools 1 or Pearson Education, Inc. 55
56 ACTIVITY 5.9: Geologic History of Southeastern Pennsylvania none INSTRUCTOR NOTES AND REFERENCES 1. Rock samples in the set of rock samples (same set for Activities 5.4, 5.5, and 5.8) must be marked with an identifying number. 2. Lava lamp option. Student understanding of magmatic processes and igneous intrusions is aided by making simple analogies to the "lava" in a lighted convecting lava lamp. This is especially useful for showing how masses of "lava" in the lamp accumulate at the top of the lamp in a manner analogous to how batholiths may form. 3. Igneous rock-forming minerals. It is useful to have students construct a flowchart for identification of these minerals. You may also want to display examples of these minerals for student observation/analysis. LAB 5 ANSWER KEY ACTIVITY 5.1: Mineral and Rock Inquiry 5.1A. 1. black and gray rock; made of hornblende and plagioclase; coarse-grained visible crystals randomly arranged and intergrown 2. transparent dark brown to black rock; made of glass; glassy texture breaks with a conchoidal fracture 3. dark gray rock; made of tiny crystals and vesicles (bubbles) 4. pink/orange, black, white, and gray rock; made of K-spar, plagioclase, quartz, and biotite; visible crystals are randomly arranged and inter-grown 5. black, white, and pink/orange rock; made of hornblende, K-spar, and quartz; very large visible crystals intergrown randomly 6. dark gray to red-gray rock; made of fine-grained material and abundant vesicles (bubbles); randomly arranged vesicles (bubbles) 5.1B. Reflect and Discuss: Answers will vary greatly Pearson Education, Inc.
57 ACTIVITY 5.2: Minerals That Form Igneous Rocks 5.2A. 1. olivine: (Fe, Mg) 2 SiO 4 ferromagnesian silicate 2. muscovite mica: potassium hydrous aluminum silicate 3. quartz: SiO 2 silicon dioxide 4. biotite mica: ferromagnesian potassium hydrous aluminum silicate 5. augite pyroxene: calcium ferromagnesian silicate 6. plagioclase feldspar: NaAlSi 3 O 8 to CaAl 2 Si 2 O 8 calcium-sodium aluminum silicate 7. K-spar (orthoclase): KAl Si 3 O 8 potassium aluminum silicate 8. hornblende amphibole: calcium ferromagnesian aluminum silicate 5.2B. Reflect and Discuss: The green, dark gray, and black minerals are mafic (1, 4, 5, 8). The other minerals are light-colored and felsic (2, 3, 6, 7). ACTIVITY 5.3: Estimate Rock Composition 5.3A Pearson Education, Inc. 57
58 5.3B. Reflect and Discuss: 1. Students can infer that either method is better but must qualify their inference. 2. There is a benefit to using two or three methods, so they can be used to verify or falsify one another. ACTIVITY 5.4: Glassy and Vesicular Textures of Igneous Rocks 5.4A. Viscosity increased as the water boiled off of the watery (aqueous) sugar solution. 5.4B. Viscosity increased as the molten sugar cooled on the aluminum foil. 5.4C. Glass and plastic objects exhibit this glassy texture when they break. 5.4D. The gas bubbles could not escape from the molten sugar, because the molten sugar was too viscous (and the bubbles could not flow from it). 5.4E. Reflect and Discuss: First, the molten sugar was so viscous that sugar molecules could not move about freely and assemble into crystals. Second, the molten sugar cooled so quickly that there was no time for visible crystals to form. 5.4F. Answers will depend on your numbered set of rock samples. 5.4G. Answers will depend on your numbered set of rock samples. ACTIVITY 5.5: Crystalline Textures of Igneous Rocks Note: If you have students melt thymol to observe its cooling and crystallization, then be sure to have them melt and cool the thymol under a fume hood. Also be sure that they do not directly touch the thymol. Check materials safety sheets for thymol before using it. 5.5A. Actual size of small crystals on left is about 0.5 mm. Actual size of larger crystals on right is about 1.5 mm. 5.5B. aphanitic texture represents the most rapid cooling 5.5C. Most students will infer that the porphyritic texture formed when a magma containing the large white crystals was erupted to Earth's surface, where the remaining melt cooled quickly to form the aphanitic groundmass. 5.5D. Answers will depend on your numbered set of rock samples Pearson Education, Inc.
59 ACTIVITY 5.6: Rock Analysis, Classification, and Origin 5.6A Pearson Education, Inc. 59
60 ACTIVITY 5.7: Thin Section Analysis and Bowen s Reaction Series 5.7A. This is an example of discontinuous reaction of the olivine with melt from which pyroxene crystallized. The olivine reacted with the melt and began to dissolve, but it became surrounded with pyroxene before it reacted completely. 5.7B. The zoning of the plagioclase crystal was caused by continuous crystallization of a plagioclase crystal in a melt of changing composition (as it cooled). As the melt became depleted in Ca, the crystal developed zones of both Ca and Na. Successive zones contained less and less Ca (and more and more Na). 5.7C. ACTIVITY 5.8: Analysis and Interpretation of Igneous Rocks Answers on the Igneous Rocks Worksheet will vary according to the rock samples assigned by you for your students to analyze and evaluate. ACTIVITY 5.9: Geologic History of Southeastern PA 5.9A. Features like A are dikes (sheet dike or radial dike). 5.9B. Based on the evidence provided in this map, most students will interpret Features like B as ring dikes. (They are actually sills that have been folded and weathered to create the ring-like map pattern.) 5.9C. Reflect and Discuss: The red units on the map are 190 million-year-old extrusive igneous rocks: basalt (and diabase, a medium-grained form of gabbro). As shown in lab manual Figure 5.15, dikes are normally associated with volcanoes. Therefore, the ancient landscape ( Ma) probably included features of extrusive igneous activity, such as volcanoes (and/or geysers) Pearson Education, Inc.
61 LABORATORY SIX Sedimentary Processes, Rocks, and Environments BIG IDEAS: Sediments are loose particles of Earth materials, including rock fragments, mineral grains weathered from rocks, animal shells, twigs, crystals precipitated from evaporating water, and chemical residues like rust. Sedimentary rocks form wherever the loose particles of sediment are compacted, cemented, or otherwise hardened to a solid mass. Layers of sediments and sedimentary rocks are like pages of a book. Their fossils and geologic structures tell us about Earth s history and past environments and ecosystems. THINK ABOUT IT (Key Questions): What do sedimentary rocks look like, and how can they be classified into groups? (Activity 6.1) What are sedimentary rocks made of, and how are they formed? (Activities 6.2, 6.3, 6.4, 6.5) How do geologists describe, classify, and identify sedimentary rocks? (Activity 6.6) What can sedimentary rocks tell us about Earth s history and past environments and ecosystems? (Activities 6.7, 6.8, 6.9, 6.10) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser sedimentary rock samples with identifying numbers/letters (or provided by instructor) hand-held magnifying lens (optional for Part 6B) metric ruler (cut from GeoTools sheet 1 or 2) sediment grain size scale (cut from GeoTools sheet 1 or 2) mineral analysis tools (see below, or provided by instructor) 2015 Pearson Education, Inc. 61
62 INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 6.1: Sedimentary Rock Inquiry none ACTIVITY 6.2: Mount Rainier Sediment Analysis none ACTIVITY 6.3: Clastic and Detrital Sediment Materials for each group of students or demonstration: extra metric rulers (for students who forgot them) hand lens (or microscope) grain size scale (GeoTools 1, 2) small piece of flat shale medium quartz sandpaper two small pieces of granite or diorite ACTIVITY 6.4: Biochemical and Chemical Sediment and Rock Materials for each group of students or demonstration: dilute (1-3%) HCl (hydrochloric acid) in dropper bottle paper towels seashells/clamshells charcoal briquette coal hand lens, plastic sandwich bags, piece of chalk from a chalkboard limonite hematite Bunsen burner Pyrex test tube with metal holder mortar and pestle safety glasses safety glass shield or classroom fume hood square of aluminum foil about the size of your hand ACTIVITY 6.5: Sediment Analysis, Classification, and Interpretation extra metric rulers (for students who forgot them) ACTIVITY 6.6: Hand Sample Analysis and Interpretation sedimentary rock samples with identifying numbers/letters (for Part 6B, one set per group of students) mineral analysis tools: pocket knife or steel masonry nails, wire nails, glass plates, streak plates, copper pennies, small magnets (one set per group of students) Pearson Education, Inc.
63 dropper bottle of dilute (about 3%) hydrochloric acid, HCl (one per group of students) paper towels ACTIVITY 6.7: Grand Canyon Outcrop Analysis and Interpretation ACTIVITY 6.8: Using the Present to Imagine the Past Dogs and Dinosaurs none ACTIVITY 6.9: Using the Present to Imagine the Past Cape Cod to Kansas none ACTIVITY 6.10: Reading Earth History from a Sequence of Strata none INSTRUCTOR NOTES AND REFERENCES 1. Rock samples for Activity 6.6 must be marked with an identifying number or letter, sothey can be organized on the Sedimentary Rocks Worksheet. 2. Sedimentary rock-forming minerals. It is useful to have students construct a flowchart for identification of these minerals. You may also want to display examples of these minerals for student observation. 3. Sedimentary Structures. As an introduction to this part of the lab, it is useful to have students examine examples of sedimentary structures in the classroom and have students recall locations around their campus or home where these or other sedimentary structures exist. For example, think of a dirt path near a building or sports field on campus. What do the sedimentary structures tell you about the activities of organisms (humans, dogs, rodents, birds, etc.) that occur there? Alternatively, one might ask how sedimentary structures can be used to analyze a crime scene Pearson Education, Inc. 63
64 LAB 6 ANSWER KEY ACTIVITY 6.1: Sedimentary Rock Inquiry 6.1A. 1. The rock is made of rounded mineral/rock grains, a mixture of sand and gravel, with the grains randomly arranged. 2. The rock is made of gravel-sized rounded shell fragments that are randomly arranged (poorly sorted). 3. The rock is made of cubic crystals (halite), randomly arranged and intergrown. 4. The rock is made of green silt and appears to be layered. 5. The rock is made of layered clay, with fossil ferns between the layers. 6. The rock is made of sand (quartz sand) and shows no layering. 6.1B. Reflect and Discuss. Answers will vary widely. ACTIVITY 6.2: Mount Rainier Sediment Analysis 6.2A. 1. a. gravel b. gravel c. gravel and silt/clay d. silt/clay 2. a. angular b. subangular c. subround 3. This is mostly detrital sediment, because it is mostly grains broken and worn from Mount Rainier. 4. a. breccia b. conglomerate c. wacke d. mudstone 5. The yellow-orange material is limonite (rust; hydrated iron oxide). The iron came from the chemical decay of iron-bearing minerals in the rocks of Mount Rainier. 6. a. Mechanical fragmentation of bedrock, probably aided by ice wedging b. Rounding of rock fragments as they move down in flowing water and under the influence of gravity, chemical decay of iron-bearing minerals, and formation of rusty stains as the iron oxidizes onto rock particles Pearson Education, Inc.
65 c. More rounding of large rock fragments also causes them to become smaller; clay and silt particles worn from the large grains accumulates as mud. Feldspars chemically decay to form clay. d. Water washed the mud from larger particles, forming a body of mud. 6.2B. Reflect and Discuss: With distance from its source the grain size of detrital decreases, the grains become more rounded, some grains chemically decay, and water/wind sort large from small particles. ACTIVITY 6.3: Clastic and Detrital Sediment 6.3A. 1. There is a mixture of mineral grains and rock fragments. 2. siliciclastic sediment 3. very angular 4. sand and silt 5. Students will record that the sharp corners that existed before abrasion became flat or rounded after abrasion. 6. Sediment will generally be more rounded as it moves from upstream to downstream (although some grains will break apart to form fresh sharp edges) Pearson Education, Inc. 65
66 6.3B. 1. The shale surface develops linear parallel scratches/groves. If this process continues, then a flat (faceted) surface will develop. 2. The shale surface develops curved scratches and rounded edges. 3. Reflect and Discuss: A grain of sediment that was abraded in a glacial environment (held in ice) will have flat surfaces and linear scratches/grooves like B1 above. A grain of sediment that was shaped while being transported by water or wind will have rounded edges and curved scratches. ACTIVITY 6.4: Biochemical and Chemical Sediment & Rock 6.4A. 1. bioclastic 2. very angular 3. The clasts are mostly subrounded. The grains were probably rounded in waves of the surf zone along a coastline or in shallow gravel bars. 4. Chalk rock is made of calcium carbonate (calcite or aragonite), which will effervesce in dilute HCl. So if the "chalk" in the classroom does not effervesce during the HCl acid test, then it is not really chalk. Some classroom "chalk" is actually gypsum (plaster of Paris) or clay. 5. Chalk forms from calcareous ooze on the deep ocean floor, where the microscopic calcium carbonate shells of calcareous plankton settle to the sea floor Pearson Education, Inc.
67 6.4B. 1. The charcoal briquette pieces are fragments of gray/black wood and stems. 2. The coal may exhibit some stems or wood fragments, but it much more dense than the charcoal briquette because it was buried within the crust under great pressure. 6.3C. Reflect and Discuss: Biochemical sedimentary rocks are rocks made mostly of fragments/grains of organisms. 6.3D. 1. Hematite has a red or red-gray color. It is Fe 2 O 3 (iron oxide). 2. Limonite is "rust" colors: yellow, orange, brown. It is Fe 2 O 3 nh 2 O (hydrated iron oxide) or FeO(OH) nh 2 O (hydrated iron oxide hydroxide, also called hydrated iron oxyhydroxide). 3. limonite 4. The heated limonite powder lost its water (became deydrated) and turned to red hematite powder. 5. Reflect and Discuss: Some modern soils that contain hematite may contain detrital hematite that was transported there formed in another location or the hematite may have formed where hot, arid conditions occurred for long periods of time Pearson Education, Inc. 67
68 ACTIVITY 6.5: Sediment Analysis, Classification, and Interpretation 6.5A-C. 6.5D. Reflect and Discuss: Quartz sand would be the LEAST diagnostic of a specific environment, because it is so common in many different environments. ACTIVITY 6.6: Hand Sample Analysis and Interpretation Answers on the Sedimentary Rocks Worksheet will vary according to the rock samples assigned by you for your students to analyze and evaluate Pearson Education, Inc.
69 ACTIVITY 6.7: Grand Canyon Outcrop Analysis and Interpretation 6.7A This cross-bedding is current cross-bedding that indicates a single direction of current flow and sediment transport. 3. Reflect and Discuss: Two hundred and seventy million years ago, this location was an ocean with moving currents of water. Ocean (marine) conditions are indicated by the presence of corals, brachiopods, and crinoids that live only in ocean/marine environments today. ACTIVITY 6.8: Using the Present to Imagine the Past Dogs and Dinosaurs 6.8A. 1. The modern environment and Triassic rock both are characterized by animal tracks (dog, dinosaur), which indicates that they both represent terrestrial (land) settings. Both have brown mud and mudcracks, which indicate dessication of mud. 2. The modern environment is muddy and has dogs living there (note dog track in image); whereas, the Triassic sample is rock and represents an ancient muddy environment where dinosaurs lived. 3. The ecosystem that Coelophysis walked in, about 215 Ma, must have been a terrestrial (land) environment with moist mud in which the dinosaur could leave its tracks (and the tracks could be covered and preserved as fossils). There must have been rain/floods to wet the mud and sun to dry the mud quickly and cause it to crack. There must have been other organisms for the dinosaur to eat Pearson Education, Inc. 69
70 6.8B. Reflect and Discuss: A dinosaur stepped in mud to make the footprint. The mud dried an cracked to form mudstone. The cracked mudstone was covered by a new layer of mud and preserved. ACTIVITY 6.9: Using the Present to Imagine the Past Cape Cod to Kansas 6.9A. 1. The modern environment and Kansas rock are both characterized by sandsized sediment and marine organisms (starfish, echinoderms). 2. The modern environment is characterized by siliciclastic sediment and live starfish, but the rock is made of carbonate sediment with starfish trace fossils. 3. Two hundred and ninety million years ago, the Kansas ecosystem must have been a sandy marine environment where starfish and their prey (molluscs, like clams) could survive. Students may imply that the water was 40 m deep, based on the modern environment, but modern starfish live in much deeper and shallower environments. 6.9B. Reflect and Discuss: In order to turn into sedimentary rock, the sediment in Photograph B must be cemented together and/or compacted. ACTIVITY 6.10: Reading Earth History from a Sequence of Strata 6.10A. Before students fill in this chart, have them work in pairs or small groups to review the hand samples (green column) and rock descriptions (yellow column), and decide what kind of environments these represent. A description of the paleoenvironment where each rock unit and hand sample formed is what students should record in the pink column. Encourage students to use the terms ocean (normal marine environment), muddy bay or estuary, evaporating bay, peat bog or swamp, and land when completing the pink column (as provided for the bottom two units). Paleoenvironmental descriptions in the pink column are used as the basis for coloring in the record of change (purple column). A completed chart is provided on the next page of this instructor manual. Also note: If your students have trouble with this rather complex analysis and evaluation, then do a similar activity by stacking two or three rock samples atop one another Pearson Education, Inc.
71 to make a simpler hypothetical sequence. Students can then examine actual rock samples and sketch the sequence in their lab notebooks. This activity works especially well if you choose rock types from local formations and samples that have obvious land (plant fossils) or ocean (seashell fossils, corals) indicators. 6.10B. Reflect and Discuss: The sea level could have risen and fallen due to cycles of glaciation in polar regions or due to uplift and subsidence of the land Pearson Education, Inc. 71
72 LABORATORY SEVEN Metamorphic Rocks, Processes, and Resources BIG IDEAS: Metamorphic rocks are rocks that have changed to a new and different form as a result of intense heat, intense pressure, and/or the action of watery hot fluids. The mineralogy and texture of a metamorphic rock can be used to deduce its original form (parent rock) and infer the geologic history of how and why it changed. Metamorphic rocks are widely used in the arts and construction industries and are sources of industrial minerals and energy. THINK ABOUT IT (Key Questions): What do metamorphic rocks look like? How can they be classified into groups? (Activity 7.1) What are the characteristics of metamorphic rocks, and how are they formed? (Activity 7.2) How are rock composition and texture used to classify, name, and interpret metamorphic rocks? (Activity 7.3) What can metamorphic rocks tell us about Earth s history and the environments in which the rocks formed? (Activity 7.4) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser metamorphic rock samples with identifying numbers/letters (or provided by instructor) hand-held magnifying lens (optional for Part 7B) metric ruler (cut from GeoTools sheet 1 or 2) mineral analysis tools (see below, or provided by instructor) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 7.1: Metamorphic Rock Inquiry none Pearson Education, Inc.
73 ACTIVITY 7.2: Metamorphic Rock Analysis and Interpretation none ACTIVITY 7.3: Hand Sample Analysis, Classification, and Origin metamorphic rock samples with identifying numbers/letters (one set per group of students) mineral analysis tools: pocket knife or steel masonry nails, wire nails, glass plates, streak plates, copper pennies, small magnets (one set per group of students) dropper bottle of dilute (1 3%) hydrochloric acid, HCl (one per group of students) ACTIVITY 7.4: Metamorphic Grades and Facies none INSTRUCTOR NOTES AND REFERENCES 1. Rock samples for Activity 7.3 must be marked with an identifying number or letter, so they can be organized on the Metamorphic Rocks Worksheet. 2. Metamorphic rock-forming minerals. It is useful to have students construct a flowchart for identification of these minerals. You may also want to display examples of these minerals for student observation. 3. Foliation. To model the development of foliated texture, mix coarse metallic confetti or flakes of biotite into a lump of play dough. Cut open the lump to observe the random arrangement of confetti/biotite grains. Next, shear the lump between two boards/books and cut it open to observe the foliation (layering) of the grains. 4. Density of metamorphic rocks. To understand the effects of extreme pressure, have students determine the density of a piece of sedimentary sandstone and a piece of dense quartzite. Then have the students explain the density and textural differences. LAB 7 ANSWER KEY ACTIVITY 7.1: Metamorphic Rock Inquiry 7.1A. 1. This rock is composed of dark (biotite) and light mineral grains arranged into Layers Pearson Education, Inc. 73
74 2. This rock is a fine-grained material that has been folded without breaking the layers. 3. This rock is composed of white calcite mineral crystals that are about equal in size. 4. This rock is made of mica-bearing layers and randomly placed garnet crystals. 5. This is a very fine-grained rock that has been folded on a small scale so it looks wrinkled. 6. This rock is made of equal-sized muscovite mica grains arranged into layers. 7.1B. Reflect and Discuss. Answers will vary widely. ACTIVITY 7.2: Metamorphic Rock Analysis and Interpretation 7.2A. 1. Both rocks are made of calcite. Both should effervesce in dilute HCl. 2. The marble has an equigranular crystalline texture, but the limestone has a bioclastic texture consisting of odd-sized grains of shells (crinoids, brachiopod, trilobite part). 7.2B. 1. The slate has the most fine-grained grain size. The grains are too small to see. The phyllite has a glittery appearance, because of its very fine grain size. The grains are flat are barely visible. The schist has the greatest grain size. The mineral grains are several mm wide. So grain size increases from slate to phyllite to schist. 2. Pyllite has a wrinkly foliated texture but schist has a scaly (like fish scales) foliated texture. 3. As rock containing platy (flat) minerals experiences strain, the platy minerals shear past one another and get compressed together. 7.2C. This rigid layered rock may have folded without breaking because it was hot when it was folded. For example, it is possible for a person to bend a steel bar that has been heated to a red hot temperature Pearson Education, Inc.
75 7.2D. 1. The part of this rock made of muscovite has a layered appearance, so the rock is foliated. 2. porphyroblastic 3. muscovite schist, garnet muscovite schist, or porphyroblastic muscovite schist 4. mudstone (claystone, siltstone, shale), slate, or phyllite 7.2E. 1. The pyroxene and plagioclase are interlayered, so the rock is foliated. 2. eclogite 3. basalt or gabbro 7.2F. Reflect and Discuss: The muscovite schist in part D and the eclogite in part E contain a mineral that can indicate high grade (garnet: see Figure 7.6 on lab manual page 192), so either rock could represent the highest grade of metamorphism. Students can make other arguments, but they must use evidence and logic to back them up. ACTIVITY 7.3: Hand Sample Analysis, Classification, and Origin Answers will vary according to the rock samples assigned by you for your students to analyze and evaluate. ACTIVITY 7.4: Metamorphic Grades and Facies 7.4A Pearson Education, Inc. 75
76 7.4B. 1. The rocks in Map B were metamorphosed under greater pressure, because kyanite is present. 7.4C C 7.4C C. 3. Reflect and Discuss: Answers will vary widely, but students should realize that metamorphic environments vary according to changes in temperature and/or pressure. The greater the temperature and pressure, the greater the metamorphic grade Pearson Education, Inc.
77 LABORATORY EIGHT Dating of Rocks, Fossils, and Geologic Events BIG IDEAS: Geologists use relative and absolute dating techniques to infer the ages of geologic features and events in geologic history. Relative age dating is the process of determining what happened first, second, and so on, in relation to other geologic features and events. Absolute age dating is the process of determining when something formed or happened in exact units of time such as days, months, or years. The geologic time scale is a chart showing the chronological sequence (relative ages) of named rock units and corresponding divisions of relative time arranged next to a scale of absolute age in years. THINK ABOUT IT (Key Questions): How can you tell relative age relationships among the parts of geologic cross sections exposed in outcrops? (Activity 8.1) How can geologic cross sections be interpreted to establish the relative ages of rock units, contacts, and other geologic features? (Activity 8.2) How are fossils used to tell geologic time and infer Earth s history? (Activity 8.3) How do geologists determine the absolute age, in years, of Earth materials and events? (Activity 8.4) How are relative and absolute dating techniques used to analyze outcrops and infer geologic history? (Activities 8.5, 8.6) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets attached to assigned activities laboratory notebook pencil with eraser calculator ruler (cut from GeoTools sheet 1 or 2) pen 2015 Pearson Education, Inc. 77
78 INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 8.1: Geologic Inquiry for Relative Age Dating none ACTIVITY 8.2: Determining Sequence of Events in Geologic Cross Sections none ACTIVITY 8.3: Use Index Fossils to Date Rocks and Events none ACTIVITY 8.4: Absolute Dating of Rocks and Fossils (optional) Geiger counter and radioactive mineral or rock sample (to demonstrate radioactive decay) ACTIVITY 8.5: Infer Geologic History from a New Mexico Outcrop extra metric rulers (for students who forgot them) ACTIVITY 8.6: CSI (Canyon Scene Investigation) Arizona extra metric rulers (for students who forgot them) INSTRUCTOR NOTES AND REFERENCES 1. Geologic Cross sections. The geologic cross sections in Activity 8.1 are arranged in order of increasing difficulty. 2. Radioactive decay. To help students understand the concept of radioactive decay, it helps to demonstrate by detecting with a Geiger counter the radioactivity emitted from a radioactive rock or mineral sample Pearson Education, Inc.
79 LAB 8 ANSWER KEY ACTIVITY 8.1: Geologic Inquiry for Relative Age Dating 8.1A. 1 and 2 8.1B. 1. The red rock (ancient body of soil) at the bottom of the picture is the oldest. It had to be there before the other layers could be stacked on top of it Pearson Education, Inc. 79
80 2. 8.1B. 3. The fractures must be younger than the lava flow layer, because the lava flow had to be there to be cracked. 4. The lava flow is under the brown soil, so it must have been there before the brown soil developed on top of it. Thus, the clasts of lava flow rock that are included in the soil must be older than the layer of soil. The soil layer is forming now, but the lava flow is not. 8.1C. 1. Students should be able to carefully trace the contact between the red sandstone and the yellow conglomerate above it. The red sandstone layers must have been compressed from one or both sides of the photograph to fold the layers. 2. Students should be able to label the exact position of the unconformity on both sides of the photograph. The sequence of events that formed the unconformity was: 1. The red sandstone layers formed as flat layers. 2. The red sandstone layers were folded. 3. The top of the folded sandstone layers was eroded (worn away). 4. The yellow conglomerate was deposited on top of the erosional surface, which is now an unconformity. 8.1D. Reflect and Discuss: Students should be able to write down three rules. They usually include statements of the Law of Original Horizontality, Law of Superposition, Law of Cross-Cutting Relationships, and/or Law of Inclusions Pearson Education, Inc.
81 ACTIVITY 8.2: Determining Sequence of Events in Geologic Cross Sections 8.2A. Geologic Cross Section 1 Geologic Cross Section 2 F (youngest, occurred last) G (youngest, occurred last) R H B I K R N A S B A F (occurred any time after C, but before R) J C D D M L O E H M C S L J G K (oldest, occurred first) P E (oldest, occurred first) Geologic Cross Section 3 Geologic Cross Section 4 S (youngest, occurred last) N J Z K D X E O M A H R B C G P F (oldest, occurred first) R (youngest, occurred last) N (Note that the house is sliding/creeping into a valley already filled with H.) H Q D Y A T F L XX G J W Z CC S B U E 2015 Pearson Education, Inc. 81
82 K X M O P C V (oldest, occurred first) ACTIVITY 8.3: Use Index Fossils to Date Rocks and Events 8.3A. 1. The brachiopod is Mucrospirifer and the trilobite is Phacops (Figure 8.10). 2. The relative age of the rock (based on when these two fossils co-existed) is middle to late Devonian Ma 8.3B. 1. The fossils are Exogyra (a bivalve/oyster mollusk) and Baculites (a cephalopod mollusk). 2. The relative age of the rock/sand (based on when these two fossils co-existed) is middle to late Cretaceous Ma 8.3C. 1. The brachiopods are Strophomena, an index fossil for the Ordovician Period. The trilobite is Flexicalymene, an index fossil for the middle to late Ordovician. 2. The relative age of the rock (based on when these two fossils co-existed) is middle to late Ordovician Ma 8.3D. 1. contact between C & D 2. Ordovician system of rocks is completely missing (and most of the Silurian). 3. The time from the top of the Olenellus zone to the base of the Phacops zone is million years, so the rock for 90 m.y. of time is missing. 8.3E. Reflect and Discuss: Rock units A D where tilted (due to a regional uplift or mountain building) and eroded off to form an unconformity Pearson Education, Inc.
83 ACTIVITY 8.4: Absolute Dating of Rocks and Fossils 8.4A. 1. One half of a half-life (0.50 half-life) has elapsed x 713,000,000 yr = 356,500,000 yr (about 357 million years old) The lava flow must be less than or equal to the age of the zircon crystals (357 million years old). 3. The rocks beneath the lava flow are older than the lava flow, so they are more than 357 million years old. 4. The rock layers above the lava flow formed after the lava flow, so they must be less than 357 million years old. 8.4B. Fifty percent of the parent has decayed, so one half-life of 4.5 billion years has elapsed. Based on this logic, the Earth is about 4.5 billion years old. 8.4C. 1. Ninety-four percent of the parent (C-14) has decayed (because only 6% remains), so about four half-lives of 5730 years have elapsed. So the peat must be about 22,920 yr old. 2. Younger plant roots would contaminate the peat with more C-14 and make it seem younger, while older limestone would contaminate the peat with more N-14 and make it seem older. 8.4D. 1. No, the zircon crystals are weathered from older igneous rocks. The zircon crystals did not form at the same time as the sand deposit; they are older than the sand deposit. 2. The radiometric age of a crystal in a rock is about the same age as the rock only if it formed at about the same time as the rock (and has not been reheated or isotopically contaminated). 8.4E. Reflect and Discuss 1. Carbon dating cannot be used to date materials older than about 60,000 yr, so carbon dating could not have been used to date a bone that is 400 million years old. (See Figure 8.10, lab manual page 182). 2. Dinosaurs did not exist 400 million years ago. They existed about 225 to 65 million years ago (Figure 8.9, lab manual p. 180) Pearson Education, Inc. 83
84 ACTIVITY 8.5: Infer Geologic History from a New Mexico Outcrop 8.5A. 1. The sedimentary rocks are Paleogene (or mid-tertiary on Figure 8.9) based on the presence of Fagopsis leaf fossils within them. 2. The zircon crystals probably formed at about the same time as the sill, before it cooled but while it was being emplaced. Zircon crystals in the sill have 98.9% U-235 and 1.10% Pb-207, so the U-235 has decayed 1/64 of a half-life. Thus, the age of the sill is x 713,000,000 yr = 10,695,000 yr (10.7 million years). 3. about 2 meters (based on the scale provided in Figure 8.11) 4. a. Sand was deposited with Fagopsis leaves during Paleogene (mid-tertiary) time. b. Mud was deposited (with Fagopsis leaves) on top of the sand during Paleogene (mid-tertiary) time. c. Additional sediments were deposited on top of the mud and compacted the sand and mud into sandstone and shale. d. The sill intruded between layers of sedimentary rock above the shale. This occurred in Neogene time (Miocene Epoch on Figure 1.3), about 10.7 Ma. e. Earthquakes and faulting occurred to produce the fault in this outcrop and its 2 m of displacement. f. Erosion of the rocks above the sill occurred to produce the present-day landscape. The fault may still be active. 8.5C. Reflect and Discuss: Answers vary widely Pearson Education, Inc.
85 ACTIVITY 8.6: CSI (Canyon Scene Investigation) Arizona 8.6A A. 2. angular unconformity 8.6A. 3. Reflect and Discuss: 1700 Ma Ma = 1159 Ma 2015 Pearson Education, Inc. 85
86 8.6B. 1. See below. 2. Angular unconformity 8.6C. Reflect and Discuss: Analysis of the photograph reveals that layers below the unconformity form an angle with the layers on top of the unconformity Pearson Education, Inc.
87 LABORATORY NINE Topographic Maps and Orthoimages BIG IDEAS: Topographic maps are two dimensional (flat) representations of threedimensional landscapes, viewed from directly above. Horizontal (two-dimensional) positions of landscape features are represented with symbols, colors, and lines relative to geographic grid systems, specific scales, and directional data. The third dimension, elevation (height) of the landscape, is represented with contour lines marking certain elevations in feet or meters above sea level. The three-dimensional and quantitative aspect of topographic maps makes them valuable to geologists and other people who want to know the shapes and elevations of landscapes. They are often used in combination with orthoimages (aerial photographs that have been adjusted to the same scale as the map). THINK ABOUT IT (Key Questions): How are specific places and quadrangles located using the latitude-longitude coordinate system, and how could geologists use Google Earth TM to study them? (Activity 9.1) What are topographic quadrangle maps, and what geographic grid systems, scales, directional data, and symbols are represented on them? (Activity 9.2) How are topographic maps constructed and interpreted? (Activities 9.3, 9.4) How are topographic maps used to calculate the relief and gradients (slopes) of landscapes? (Activity 9.5) How is a topographic profile constructed from a topographic map, and what is its vertical exaggeration? (Activity 9.6) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets attached to assigned activities laboratory notebook pencil with eraser colored pencils pen (black or blue) metric ruler (cut from GeoTools sheet 1 and 2) protractor (cut from GeoTools sheet 4) UTM templates cut from GeoTools sheets 2 4 as needed calculator computer or other electrical device with Internet access (Activity 9.1) topographic quadrangle map assigned by your instructor (or provided by instructor) 2015 Pearson Education, Inc. 87
88 INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 9.1: Map and Google Earth TM Inquiry computer or other electrical device with Internet access for students who do not have it ACTIVITY 9.2: Map Locations, Distances, Directions, and Symbols extra metric rulers (for students who forgot them) extra protractors for students who forgot them, or scissors for students to cut them from (cut from GeoTools sheet 4) ACTIVITY 9.3: Topographic Map Construction none ACTIVITY 9.4: Topographic Map and Orthoimage Interpretation extra metric rulers (for students who forgot them) ACTIVITY 9.5: Relief and Gradient (Slope) Analysis extra metric rulers (for students who forgot them) ACTIVITY 9.6: Topographic Profile Construction extra metric rulers (for students who forgot them) INSTRUCTOR NOTES AND REFERENCES 1. Raised Relief Maps. Raised relief maps of topographic quadrangles are a very useful aid for having students understand how to read topographic maps. Such maps are available commercially, perhaps even for your region. 2. Topographic map construction. You may want to modify this laboratory with a part on topographic map construction in the field. See Bart, H.A., A hands-on approach to understanding topographic maps and their construction. Journal of Geological Education 39: Pearson Education, Inc.
89 LAB 9 ANSWER KEY ACTIVITY 9.1: Map and Google Earth TM Inquiry 9.1A. Answers will vary in terms of scale, absolute location, or location relative to known features. For example, a student may say that s/he is in San Diego, University of Nebraska, or on 234 Oak Lane in Pittsburgh. A student may give his/her location in relation to geographic coordinates. A student may also say that s/he is in the first row of chairs in a specific classroom of a building on a particular street, or s/he may say that s/he is on top of a big hill on the south side of campus. 9.1B. 1. Answers will vary according to the student. 2. Answers will vary according to the student. 3. Answers will vary according to the student. Check to be sure that their coordinates are correct for their answer in B2. 4. The quadrangle is located from 0 30 degrees south latitude and degrees east longitude. 9.1C. 1. Answers will vary according to the student. 2. Answers will vary according to the student. 3. Answers will vary according to the student. 4. Answers will vary according to the student. 9.1D. Reflect and Discuss: Answers will vary according to the student Pearson Education, Inc. 89
90 ACTIVITY 9.2: Map Locations, Distances, Directions, and Symbols 9.2A. Latitude: 40 S Longitude: 20 W 9.2B. 1. center SW1/4, NE1/4, SE1/4, sec. 11, T1S, R2W 2. A township is 6 miles x 6 miles, or 36 square miles. Since 1 square mile contains 640 acres, there are 36 x 640 acres in a township, or 23,040 acres altogether. 3. This area is ¼ of ¼ of 1 section, and a section is 640 acres or 1 square mile. So, the area is x 640 acres, or 40 acres. 40 acres x $500/acre = $20, C. 1. 1:100,000 means that 1 inch on the map equals 100,000 inches on the ground. There are 12 inches per foot, so 100,000 in. 12 in./ft = feet There are 5280 ft/mi, so ft 5280 ft/mi = mi So, one inch on the map equals miles on the ground. 2. 1:100,000 means that 1 cm on the map equals 100,000 cm on the ground. There are 100 cm per meter, so 100,000 cm 100 cm/m = 1000 m So, one cm on the map equals 1000 m (i.e., 1 km) on the ground. 9.2D. At a scale of 1:24,000, 1 mm on the map equals 24,000 mm on the ground. There are 1000 mm/m, so 1 mm on the map equals 24 meters on the ground. 5 m 24 m = 0.2, so an object that is 5 m long in real life (on the ground) will be 0.2 mm on the map. 9.2E. 1. north 24 east; azimuth of south 24 west; azimuth of F N, W 2. 11S 3. The map was made in 1958, and photorevised in E 5. sec. 21, T5N, R13W 9.2G. 1. Woods are a solid green color. Orchard is a green dotted pattern. Refer to Figure 9.4 symbols. 2. Dual highway with median strip (Route 14) Primary highway (Sierra Highway) Pearson Education, Inc.
91 Secondary highway (Escondido Canyon Road) Light duty roads Unimproved roads Trail (one trail in the NW corner of the map) m N m E H. Reflect and Discuss: The red numbers (14, 15, 16, 21, 22, 23) are PLSS section numbers in the middle of sections outlined with red lines. Each section is 1 square mile. The complete width of sections 15 and 22 are visible, so the bar scale for 1 mile must equal the exact width of section 15 and 22 (i.e., 67 mm long). According to the Mathematical Conversions chart on Lab Manual page xii, one kilometer equals mile. Therefore, the bar scale for kilometers must be times the width of sections 15 and 22 (i.e., 41.6 mm long) Pearson Education, Inc. 91
92 ACTIVITY 9.3: Topographic Map Construction 9.3A. 9.3B Pearson Education, Inc.
93 9.3C. 9.3D. Reflect and Discuss: Two of the bold index contours are labeled 7300 feet and 7800 feet (above sea level), and there are five bold contour lines from the 7300 line to the 7800 line. This means that the index contour lines are spaced at an interval of 100 feet. There are also four narrow contour lines between each two index contour lines, so the spaces between them are 20 feet. The contour interval is 20 feet Pearson Education, Inc. 93
94 ACTIVITY 9.4: Topographic Map and Orthoimage Interpretation 9.4A. 1. The highest point in the map is at the crest of SP Mountain, where a reference elevation of 7021 is located. It means that the elevation is 7021 feet above sea level. 2. Students should notice the general relief of the land based on the index contour lines. The north-central part of the map is below 6000 feet. There are two streams there, and one exits the map at an elevation of about 5930 feet, which is the lowest point on the map (inside of the triangle) Pearson Education, Inc.
95 3. The highest point on SP Mountain is 7021 feet, and its base (along the southeast edge of the mountain) is as low as 6200 feet. Therefore, the total relief of the mountain is 821 feet. 4. The locations where streams begin are circled on the map above. Contour lines for a V shape where they cross a stream, and the V always points upstream, like the head of an arrow. 5. The crater has hachure lines on the contour lines to indicate which contours are located inside of a closed depression. 6. The crater is a circular depression that seems to be a crater at the top of a volcano. Using the black grid as a reference (each square is one square kilometer), the crater has a diameter of km, or 328 meters (328 m x ft/m = 1076 feet). 7. The orange-brown colored area is probably a lava flow that cooled to form a body of igneous rock Pearson Education, Inc. 95
96 9.4B. 1. See the figure below, where the dashed line indicates the approximate outline of the older volcano. 2. See the figure below, where the solid line indicates the outline of the crater of the older volcano. The crater has no hachure marks on the topographic map, because it is not a closed depression. It has two streams that drain from it. 9.4C. 1. Contour lines on the 2011 topographic map are more smoothed and generalized than they are in the 1989 map. 2. The 1989 map indicates that there were orchards, but no orchards are shown for D. Students will vary in their opinions of which map series is the best and its advantages and disadvantages. Have them discuss this in small groups or by brainstorming as a class Pearson Education, Inc.
97 ACTIVITY 9.5: Relief and Gradient (Slope) Analysis 9.5A. 1. The contour interval is 20 meters meters 180 meters = 240 meters (Student answers may be m higher.) meters 3 km = 13 m/km 4. Reflect and Discuss: One kilometer is about 4.5 mm long on this map and the contour interval is 20 m. So any area where the contour lines are closer than 4.5 mm is an area where the slope exceeds 20m/km. 5. Using the method described above, the areas of the map with slopes steeper than 20m/km have been shaded (next page). Thus, the black line from A to B is one route you could drive to avoid gradients over 20 m/km. The dashed line from A to B is another route you could drive to avoid gradients over 20m/km by having a road with many switch-backs. Other routes are possible Pearson Education, Inc. 97
98 ACTIVITY 9.6: Topographic Profile Construction 9.6A. Completed topographic profile. NOTE: Student profiles will vary in vertical scale and vertical exaggeration unless you specify them ahead of time. 9.6B. The horizontal scale of the map and profile is printed on the map: 1:24,000. If students use a vertical scale of 1 inch equals 100 feet, and there are 12 inches per foot, then the vertical scale is 1:1200. Using either method 1 or 2 from Figure 2.14 (lab manual page 213), students can calculate that the vertical exaggeration is thus 20x. This answer will vary if students use a different vertical scale. 9.6C. Reflect and Discuss. Most topographic profiles are exaggerated. If you do not know how much they are exaggerated, then you cannot imagine what the topography is actually like Pearson Education, Inc.
99 LABORATORY TEN Geologic Structures, Maps, and Block Diagrams BIG IDEAS: Some of Earth s rocky landscapes expose originally horizontal layers of rock that have been visibly tilted, fractured, dislocated, folded, or otherwise deformed into complex geologic structures. The structures are often too large to see in one place. To visualize them, geologists make regional geologic maps and block diagrams with field data assembled from many sites. The maps and diagrams are then used to reveal the structures and determine how they formed. THINK ABOUT IT (Key Questions): How are deformed rocks identified and classified? (Activity 10.1) What kinds of stress relationships cause geologic structures to develop? (Activity 10.2) How do geologists map geologic structures on and beneath Earth s surface? (Activities 10.3, 10.4) How are three-dimensional models used to visualize geologic structures? (Activities 10.5, 10.6) How do geologists define, analyze, and interpret geologic structures using images of landscapes? (Activity 10.7) How do geologists visualize geologic structures using geologic maps? (Activity 9.8) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets attached to assigned activities laboratory notebook pencil with eraser set of colored pencils scissors Cardboard Models 1 6 (cut from back of laboratory manual) calculator metric ruler (cut from GeoTools sheet 1 or 2) (optional) computer or other electrical device with Internet access (Activity 10.7) 2015 Pearson Education, Inc. 99
100 INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 10.1: Geologic Structures Inquiry none ACTIVITY 10.2: Visualizing How Stresses Deform Rocks none ACTIVITY 10.3: Map Contacts and Formations red and blue colored pencils (for students who do not have them) ACTIVITY 10.4: Determine Attitude of Rock Layers and a Formation Contact none ACTIVITY 10.5: Cardboard Model Analysis and Interpretation extra metric rulers (for students who forgot them) extra protractors (for students who forgot them) extra scissors (for students who forgot them) ACTIVITY 10.6: Block Diagram Analysis and Interpretation none ACTIVITY 10.7: Nevada Fault Analysis Using Orthoimages none ACTIVITY 10.8: Appalachian Mountains Geologic Map extra metric rulers (for students who forgot them) extra protractors (for students who forgot them) scratch paper INSTRUCTOR NOTES AND REFERENCES 1. Cardboard Models. Significant time is saved if you require your students to cut out their cardboard models 1 6 before the laboratory period and bring them to lab. 2. Society Value of Geologic Maps. To engage students at the start of this laboratory, it is useful to brainstorm the value of geologic maps to society and to the individuals in the lab. A useful source of information for this type of engagement is: Bernknopf, R.L., Brookshire, D.S., Soller, D.R., McKee, M.J., Sutter, J.F., Matti, J.C., and R.H. Campbell Societal Value of Geologic Maps. U.S. Geological Survey Circular 1111:53. (Multiple copies can be ordered free from the USGS Map Distribution Center, Box 25286, Building 810, Denver Federal Center, Denver, CO ) Pearson Education, Inc.
101 LAB 10 ANSWER KEY ACTIVITY 10.1: Geologic Structures Inquiry 10.1A. 1. Undeformed: these rocks have their original horizontality and no fractures, faults, or folds. 2. Deformed: these rocks have been faulted (due to compression of brittle rock). 3. Deformed: these rocks have been folded in a manner suggesting that the rock was not brittle. There is one fault, so there was some shearing during the folding process. 4. Deformed: these rocks still have their original horizontality, but there are large fractures that cut across them (so the rock was brittle when fractured). 10.1B. Reflect and Discuss: Classifications will vary widely among students. ACTIVITY 10.2: Visualizing How Stresses Deform Rocks 10.2A. 10.2B Pearson Education, Inc. 101
102 10.2C. Answers will vary, but most students will describe the force of gravity, which pulls rocks towards the center of Earth. Mantle convection can force rocks to move in any direction; although, students generally think of it as causing rocks to rise (buoyant force of less dense rocks) or sink (dense rocks). ACTIVITY 10.3: Map Contacts and Formations 10.3A Compression 10.3B. Check to be sure that students have done a reasonably neat and exact job of mapping both formations on both sides of the Colorado River. 10.3C. Reflect and Discuss: The Watahomigi Formation outcrops are of equal width and elevation, so the rocks appear to be relatively horizontal and undeformed Pearson Education, Inc.
103 ACTIVITY 10.4: Determine Attitude of Rock Layers and a Formation Contact 10.4A. 10.4B Pearson Education, Inc. 103
104 10.4C. 10.4D. Reflect and Discuss: Check to be sure that each student actually traced along a possible formation contact and justified their method for doing so. ACTIVITY 10.5: Cardboard Model Analysis and Interpretation 10.5A. Cardboard Model 1 1. Refer to completed Model 1 ahead. 2. All of the formations were deposited as horizontal layers. They were all tilted 24 degrees west after Permian time. 10.5B. Cardboard Model 2 1. Refer to completed Model 2 ahead in this book. 2. The strikes are identical (north-south). 3. The rocks dip west at locations I and II, but the rocks dip east at locations III and IV. In other words, rocks at locations I and II dip west and away from the rocks at locations III and IV (which dip east). 10.5C. Cardboard Model 3 1. Refer to completed Model 3 ahead. 2. The strikes are identical (north-south). 3. The rocks dip east at locations I and II, but the rocks dip west at locations III and IV. In other words, rocks at locations I and II dip east toward the rocks at locations III and IV (which dip west) Pearson Education, Inc.
105 4. This fold is not plunging. 5. This is a syncline. 6. There is no variation in strike if the fold is non-plunging, as in this model. 10.5D. Cardboard Model 4 1. Refer to completed Model 4 ahead. 2. Unlike Model 3 (where strike and dip on both limbs of the fold are the same), the strike in this Model 4 plunging fold is different on each limb of the fold. Each limb also dips in a different direction from Model 3; the rocks now dip at an angle to one another instead of directly at one another. 10.5E. Cardboard Model 5 1. Refer to completed Model 5 ahead. 2. It plunges north. One can see on the west edge of the block (a cross section parallel to the fold axis) that the formations are dipping to the north. 10.5F. Cardboard Model 6 1. Refer to completed Model 6 ahead. 2. In vertical cross-section, and in three-dimensional perspective of the block diagram, the fault is a reverse fault. The hanging wall moved up relative to the footwall. Notice, however, that if viewed solely from above (map view), then the fault appears to be a strike-slip fault. Thus, the fault has a small amount of oblique motion, which is common for many reverse and normal faults.) 3. The contact is apparently offset to the west on the north side of the fault, so there is a small amount of left-lateral motion along the fault. 4. Yes, it has a small amount of left-lateral offset. (Many reverse faults have some oblique motion, so they appear as strike-slip faults when viewed solely from above. This is the exact motion of the hanging wall and footwall). 5. Reflect and Discuss: Yes. The formations dip due west, so as erosion lowers the landscape, the formation contacts that crop out at Earth s surface will migrate west. To see this, look at the south end of the block diagram and imagine how the formation contacts would move if you slowly eroded the top of the block. The formation contacts at the top of the block would move west the dip direction of the beds/formations. If you do the same for the fault (by looking at the west or east side of the block), then you will notice 2015 Pearson Education, Inc. 105
106 that the location where the fault breaks the land surface would move north (the direction that is down the dip of the fault) as the block is eroded Pearson Education, Inc.
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112 ACTIVITY 10.6: Block Diagram Analysis and Interpretation Pearson Education, Inc.
113 ACTIVITY 10.6 (continued) 2015 Pearson Education, Inc. 113
114 ACTIVITY 10.7: Nevada Fault Analysis Using Orthoimages 10.7A B. 1. See the image below. 2. The main faults are right-lateral strike-slip faults. Some very short faults have a left-lateral strike-slip motion. 10.7C. Reflect and Discuss: This region experienced shear stress 11 6 million years ago. The rocks were not deeply buried, so they ruptured in brittle fashion to make the faults Pearson Education, Inc.
115 ACTIVITY 10.8: Appalachian Mountains Geologic Map 10.8A. See the completed geologic cross section below. 10.8B. See the labels on geologic structures below. 10.8C. See the red half arrows on the fault below, which is a right-lateral strike-slip fault Pearson Education, Inc. 115
116 LABORATORY ELEVEN Stream Processes, Landscapes, Mass Wastage, and Flood Hazards BIG IDEAS: Streams shape the landscape and provide water to communities and agricultural systems. Flood hazards and mass wasting are also associated with streams. Tools and methods for determining flood hazards are provided by the Federal Emergency Management Agency (FEMA). THINK ABOUT IT (Key Questions): How are you affected by streams? (Activity 10.1) How does stream erosion shape the landscape? (Activities 10.2, 10.3, 10.4, 10.5) How do geologists determine the risk of flooding along rivers and streams? (Activity 10.6) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser calculator piece of string about 30 cm or 12 inches long (or provided by instructor) metric ruler (cut from GeoTools sheet 1 or 2) pocket stereoscope (or provided by instructor) computer or other electrical device with Internet access (Activity 11.1) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 11.1: Streamer Inquiry none ACTIVITY 11.2: Introduction to Stream Processes and Landscapes extra metric rulers (for students who forgot them) about 1 foot (30 cm) of thread per student (to measure sinuosity) Pearson Education, Inc.
117 ACTIVITY 11.3: Escarpments and Stream Terraces none ACTIVITY 11.4: Meander Evolution on the Rio Grande extra metric rulers (for students who forgot them) ACTIVITY 11.5: Mass Wastage at Niagara Falls extra metric rulers (for students who forgot them) pieces of string about 30 cm or 12 inches long for students (or obtained by students) ACTIVITY 11.6: Flood Hazard Mapping, Assessment, and Risk extra metric rulers (for students who forgot them) LAB 11 ANSWER KEY ACTIVITY 11.1: Streamer Inquiry 11.1A. Students will choose many different communities to study, so their answers will vary greatly in this part of this activity. 11.1B. Students will choose many different communities to study, so their answers will vary greatly in this part of this activity. 11.1C. 1. Regardless of what stream system a student has studied, s/he should notice that from small tributaries to the largest river: The amount of water in a stream increases. The width of the streams increases. The slope of the streams decreases. 11.1D. Reflect and Discuss: Most communities want to know where the water in their stream comes from (i.e., what is up stream) because they want to be sure that the water supply and quality is good, and the flood hazard is low. What happens upstream impacts communities downstream in terms of water supply, quality, and flood control. 11.1E. Reflect and Discuss: A community located on/near a stream may want to know where the water goes after passing their community because the downstream communities may have rights to some of the water supply (that would limit how much water an upstream community could withdraw from the stream) and may pursue legal requirements for water quality and flood hazards that upstream 2015 Pearson Education, Inc. 117
118 communities would have to honor. In river systems with important fish spawns, the downstream communities would have access to spawning fish before the upstream communities. Sometimes, what happens downstream impacts upstream communities. ACTIVITY 11.2: Introduction to Stream Processes and Landscapes 11.2A. Trout Run Drainage Basin 1. a. 20 feet b. 240 feet c. 100 feet d. 180 feet e. 1 mile f. 80 feet/mile g. See the shaded (crosshatched) hilltops and dashed drainage divide below. h. north Pearson Education, Inc.
119 2. No. It is unlikely that oil spilled at location x would wash downhill into Trout Run because x is outside the Trout Run drainage basin. 11.2B. 1. The gradient of the ancient upland surface is shown by the red line at the base of Figure 11.4 (Lab Manual page 290). The elevation changes from 3080 feet to 3010 feet (a difference of 70 feet, or 21.3 meters) over a distance of 2.76 miles (4.4 kilometers). So the gradient of the ancient upland surface is: 70 ft / 2.76 mi = 25.4 ft per mi, OR 21.3 m / 4.4 km = 4.84 m/km 2. The present-day drainage pattern in the Lake Scott quadrangle is dendritic. Dendritic drainage patterns commonly develop in regions having relatively flat-lying (horizontal) layers of rock or homogeneous sediment layers (see Figure 11.2). Folded strata and faulted strata would cause the water to flow in annular, radial, trellis, or rectangular patterns. Therefore, the bedrock of this region must be comprised of relatively horizontal layers. 3. See the completed map below. The dashed line shows the boundary of the Garvin Canyon drainage basin Pearson Education, Inc. 119
120 4. From A to B the first order stream in Garvin Canyon has the following gradient: 110 ft / 0.75 mi = 147 ft/mi From A to B the first order stream in Garvin Canyon has the following sinuosity: 0.8 mi / 0.75 mi = The stream in Timber Canyon is a second order stream, because it has several first order streams as tributaries. From C to D, the stream in Timber Canyon flows from the 2950-foot index contour to the 2850-foot contour over a distance of about 2.48 mi. From C to D the second order stream in Timber Canyon has the following gradient: 100 ft / 2.48 mi = 40.3 ft/mi From C to D the second order stream in Timber Canyon has the following sinuosity: 3.3 mi / 2.48 mi = As stream order increases from first order streams like the one in Garvin Canyon to the tenth order Mississippi River, the stream gradient decreases. 7. Discharge of streams increases as they increase in order, so the relative number of fish living in a stream should also increase with increasing stream order (because there is more space in which they can live). 11.2C. Strasburg, VA quadrangle 1. Trellis drainage: A pattern of channels resembling a vine growing on a trellis. It develops where tilted layers of resistant and nonresistant rock form parallel ridges and valleys. 2. From E to F, this small stream has the following gradient: 800 ft / 0.75 mi = 1067 ft/mi From E to F, this small stream has the following sinuosity: 0.78 mi / 0.75 mi = From G to H, Passage Creek has the following gradient: 80 ft / 2.53 mi = 31.6 ft/mi From G to H, Passage Creek has the following sinuosity: 4.24 mi / 2.53 mi = Pearson Education, Inc.
121 11.2D. Ennis, Montana quadrangle 1. a. straight and sinuous b. straight, sinuous, and braided c. meandering and braided 2 and 3. Refer to the completed profile below. 4. a. 3 rd order b. The stream order reverses itself, as the streams on the alluvial fan diverge (instead of merge). As the streams diverge, their discharge and ability to transport sediment decreases, so sediment accumulates on the alluvial fan Pearson Education, Inc. 121
122 11.2E. 1. Graph 2. There is a relationship. The higher the gradient, the lower the sinuosity. Streams with very high gradient tend to be linear, those with less gradient are sinuous, and those of least gradient are meandering. 11.2F. Reflect and Discuss: The kind of stream drainage pattern that develops on a landscape, and weather a stream is eroding bedrock or depositing sediment, depends on characteristics of the bedrock (homogeneous and/or horizontallybedded, versus dipping and having layers of different resistances to weathering) and the gradient of the landscape. Students may also infer factors such as climate and land use practices Pearson Education, Inc.
123 ACTIVITY 11.3: Escarpments and Stream Terraces 11.3A. Yazoo tributaries, oxbow lakes, marshes 11.3B. Sketch with labels 11.3C. The escarpments form at the edges of floodplains, when the flooding river cuts into adjacent hillsides. 11.3D. See the sketch above. 11.3E. See the sketch above. The past width of the Souris River floodplain is indicated by the extent of terraces between two major escarpments. 11.3F. The Souris River had a wider floodplain in the past because it had a greater discharge from glacial melt water. It was noted at the start of this part that glaciers were melting in this region about 11,000 12,000 years ago. Therefore, the discharge of the Souris River was probably greater at that time (and less at this modern time). 11.3G. Reflect and Discuss. The south side of the Souris River may have one terrace that is feet higher than the main terrace on the north side of the river. This may be an older terrace, and its northern half was eroded by later (more recent) cutting of terraces. ACTIVITY 11.4: Meander Evolution on the Rio Grande 11.4A. The cutbanks moved downstream and toward the outside of the meanders. 11.4B. 1. Mexico 2. USA 2015 Pearson Education, Inc. 123
124 3. These meanders (H and I) got longer and narrower until the river cut across them at their narrowest point (neck cutoff), thus leaving an oxbow lake behind. 11.4C. Meanders here will experience meander cutoff, so an oxbow lake will result. 11.4D. L, M, and N are oxbow lakes that indicate the former locations of meanders. This indicates that meandering and neck cutoff have occurred here for a long time. 11.4E. The meanders have migrated meters over the 55 years from , so they migrate at a rate between 5 and 15 meters/year. The data from meanders A G reveal an average rate of about 500 meters/55 years, or about 9 meters/year. 11.4F. Reflect and Discuss: A straight channel develops sinuosity that leads to welldeveloped meanders that migrate downstream and outward (toward the edges of the floodplain). During floods, the river cuts through the neck of some meanders (neck cutoff). This leaves an oxbow lake behind and re-establishes a straight channel. ACTIVITY 11.5: Mass Wastage at Niagara Falls 11.5A. The falls have retreated about 12 kilometers (1,200,000 cm) in 11,000 years. So, 1,200,000 cm 11,000 yr = 109 cm/yr. 11.5B. Some factors that could speed up the retreat of the falls are: increase in river discharge caused by a change to a wetter climate. increase in river discharge caused by more frequent episodic discharges of water from dams or factories on the Niagara River or its tributaries. slight differences in the composition or fracturing (more fractures) of the bedrock being eroded may make it easier to erode. 11.5C. Some factors that could slow down the retreat of the falls are: decrease in river discharge caused by a change to a drier climate. decrease in river discharge caused by fewer episodic discharges of water from dams or factories on the Niagara River or its tributaries. slight differences in the composition or fracturing (fewer fractures) of the bedrock being eroded may make it more difficult to erode. 11.5D. Based on Question 11.3A, the falls have been retreating at a rate of about 109 cm/year. Also, there are 100,000 cm/km, so 35 km = 3,500,000 cm. 3,500,000 cm 109 cm/yr = 32,110 yr (or about 32,000 years) Pearson Education, Inc.
125 11.5E. Reflect and Discuss: The falls probably formed when glaciers that cut the Great Lakes retreated, leaving the escarpment. ACTIVITY 11.6: Flood Hazard Mapping, Assessment, and Risk 11.6A. Before students move to part B, check their work to be sure that they correctly traced the 290-foot contour line and labeled the 1994 Flood Hazard Zone. 11.6B. Some structures are: Mobile home park: homes would have been destroyed. Felton Cemetery: graves may have been disturbed. Sewage treatment pond: raw sewage would have contaminated the river. Drinking water filtration plant was flooded, so no drinking water. Mentezuma Post Office: no mail delivery. Georgia Power Company: electrical outages. Roads/highways: no travel between Oglethorpe and Montezuma. 11.6C. The pale yellow-brown grid is a UTM grid of 1 x 1 km squares. Use that as a scale km km 11.6D feet 2. The flood reached a level of 290 feet, so point Z was under 20 feet of water. 3. The flood stayed within the floodplain of the Souris River, so it was within the normal range of flooding for this river. 11.6E. 1. Recurrence interval for ranks 1 5. Rank of annual highest river stage (S) Recurrence interval (RI), in years A 100-year flood is a flood magnitude that has a 1-in-100 probability, or 1 percent chance, of occurring in any given year Pearson Education, Inc. 125
126 3. Points plotted by different students should occur in the exact same location on the graph; however, lines of best fit will vary from students to student. Most students plot one of these lines of best fit: a line passing through the points for recurrence intervals of 1.0 and 100. a line passing through the points for recurrence intervals of 3.4, 5, 20, 25, 33, 50, and 100. a line passing through the points for recurrence intervals of 1.3 and 100 (because it separates six points below and above the line). a line passing through the point for recurrence interval of 1.0 and a point located at recurrence interval of 100 and Flood Magnitude of 293 (because points below and above the line are separated from the line by equal vertical distances). 4. The probability that a future 10-year flood will occur in any given year is 1-in-10 or 10%. Students will determine that such a flood would have a magnitude of feet, depending on the line of best fit that was drawn by each student in 36c. 5. Answers will vary according to the line of best fit drawn by each individual student above; however, the answers should range from years. 11.6F. Most students answer that the BFE for Montezuma, GA is 290 feet, because they have a point plotted on their graph for a RI of 100 and a corresponding flood magnitude of 290 feet. However, some students read the point where their line of best fit intersects the vertical line for the RI of 100, in which case answers will normally vary from feet. 11.4G. Reflect and Discuss: Based on their answer above, the new BFE line plotted by students is normally higher in elevation in most areas than the line plotted by FEMA on its1996 FIRM. This makes the flood hazard zone larger Pearson Education, Inc.
127 LABORATORY TWELVE Groundwater Processes, Resources, and Risks BIG IDEAS: Groundwater is subsurface water, beneath the landscape rather than on its surface. Most bodies of groundwater form when rainwater seeps into the ground under the influence of gravity and fills up (saturates) spaces in cracks and between grains. Some groundwater is unconfined and must be pumped from the ground to be used. Confined groundwater is under pressure and will flow on its own if a well is drilled to its location. Karst topography and rapid movement of water can occur when groundwater dissolves caves in soluble rocks, and land subsidence can occur when humans withdraw groundwater faster than it can be replenished. THINK ABOUT IT (Key Questions): How does groundwater behave underground? (Activity 12.1) What is karst topography and how does water flow beneath it? (Activities 12.2, 12.3) What can happen if groundwater is withdrawn faster than it is replenished? (Activity 12.4) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser metric ruler (cut from GeoTools sheet 1) calculator (or provided by instructor) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 12.1: Groundwater Inquiry (optional) samples of two kinds of shale and two kinds of sandstone (per group) and dropper bottles filled with water for students to analyze the permeability of shale and sandstone 2015 Pearson Education, Inc. 127
128 ACTIVITY 12.2: Karst Processes and Topography none ACTIVITY 12.3: Floridan Limestone Aquifer none ACTIVITY 12.4: Land Subsidence from Groundwater Withdrawal groundwater modeling jars (optional, see Instructor Note 1 below) INSTRUCTOR NOTES AND REFERENCES 1. Groundwater Model. You can make a simple groundwater model by filling a jar with aquarium gravel, and then adding water colored red with food coloring until about half of the gravel is submerged. Replace the lid tightly. When students turn the jar upside down, they will see the red water flow under the influence of gravity to form a zone of saturation, zone of aeration, and water table. No matter how they orient the jar, these three features reform. 2. Florida Groundwater References (Activity 12.3). Two useful references are: Rosenau, J.C., Faulkner, G.L., Hendry, C.W., and R.W. Hull Springs of Florida. Florida Bureau of Geology Bulletin 31:461p. Stewart, J.W., and L.R. Mills Hydrogeology of the Sulphur Springs area, Tampa, Florida. U.S. Geological Survey Water Resources Investigations Report: For an excellent summary of USGS investigation of the hydrogeology of the Santa Clara Valley (Activity 12.4), refer to the 1984 UNESCO Guidebook to studies of land subsidence due to ground-water withdrawal Case History No. 9.14, Santa Clara Valley, California, U.S.A., by Joseph F. Poland (U.S. Geological Survey, Sacramento, California): LAB 12 ANSWER KEY ACTIVITY 12.1: Groundwater Inquiry 12.1A. 1. Water beaded up on the shale. The shale was not permeable, so shale will confine water Pearson Education, Inc.
129 2. Water soaked into the sandstone samples, so water can conduct the flow of water. Water should be able to pass through it or be stored in it. 12.1B. Graph. 1. The distance that the water jet flows is directly related to the height of water in the bottle that is above the hole from which the water jet is shooting. 2. a. See the graph above. Water is flowing from the hole in the bottle in the artesian part of the graph. b. See the graph above. When the water in the bottle is the same as the level of the hole in the bottle, then water stops flowing from the bottle (and the system is no longer artesian). 12.1C. Reflect and Discuss: Student sketches should show the bottle tilted at an angle, so the water jet would take on a more vertical position. One situation where this could occur is where sandstone in a syncline is confined by shale above and below (like the sides of the bottle). A well drilled at the axis of the syncline would be artesian Pearson Education, Inc. 129
130 ACTIVITY 12.2: Karst Processes and Topography 12.2A. 1. The plants are growing along lines running in two different directions. Groundwater into the bedrock must be channeled along these linear features, which probably represent fractures or faults in the bedrock. There are two sets of these fractures/faults at roughly right angles to one another. Surface water probably seeps into the bedrock along these fractures/faults, where it becomes groundwater that the plants require for their survival and growth. 2. The groundwater is contained in, and flowing along, the fractures/faults. A well drilled at a point where two or more of the fractures/faults intersect would be expected to produce more water than a well drilled along just one fracture/fault or between the fractures/faults. Aerial photographs made in spring or summer, when plants are growing along the fractures/faults could be used to identify them and locate the best place to drill a well using the above logic. 3. Reflect and Discuss: The features in both figures are developing as a result of the solution of limestone bedrock by acidic groundwater. The bedrock in both locations has intersecting fractures/faults along which groundwater flows. Figure 12.5 is a cave that could be developing beneath an area like B. 1. Site B is the most hazardous, because it is located directly over very large caves that are only partly filled with water. The weight of a new home (and the lack of hydrostatic pressure), or vibrations from heavy equipment, may cause the cave roof to collapse and form a large sinkhole. 2. Site C is the least hazardous because it is not located directly over any caves. 3. Reflect and Discuss: Drill holes into the bedrock to check for caves beneath the site. 12.1C. 1. There are sinkholes, small lakes, solution valleys, and disappearing streams on the portions of the map where limestone bedrock occurs at/near the surface of the land. The areas underlain by limestone generally are of low elevation and the hills lack steep slopes (because the bedrock is chemically decayed). 2. A depression contains a pond if the bottom of the depression is below the water table Pearson Education, Inc.
131 3. Reflect and Discuss: Ponds occur where the water table is higher than the bottom of a sinkhole. To determine how groundwater travels through the region, make a contour map of the elevations of the water surfaces in the ponds (i.e., elevations of the water table in the ponds). Groundwater flows down gradient, from higher elevations of the water table to lower elevations of the water table. 12.1D. 1. Students should realize that the contact between limestone and sandstone is marked by a change in relief. The sandstone makes steeper slopes, so it seems to occur at elevations equal to and above 600 feet (red line on the next page). 2. See the blue arrows and circle on the next page. 3. See the elevations and arrow in black on the next page. 4. Examples of solution valleys are marked by green lines on the next page. 5. Reflect and Discuss: The pond has an elevation of 825 feet, and the highest water table in ponds just south of Bald Hill is about 595 feet, so the well must be drilled about 230 feet just to reach the water table (825 ft ft = 230 ft) Pearson Education, Inc. 131
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133 ACTIVITY 12.3: Floridan Limestone Aquifer 12.3A. See the completed map on the next page. 12.3B. See the completed map on the next page. 12.3C. See the arrows drawn on the map on the next page of this book. There are few lakes in the southern part of the map because the water table is generally lower than the bottom of the closed depressions. 12.3D. See the completed map on the next page. 12.3E. See the completed map on the next page. 12.3F. See the completed map on the next page. 12.3G. 1. about 400 feet/hour 2. about miles/hour 3. about 123 meters/hour 12.3H. 1. Student answers will vary widely but should reflect an understanding of groundwater supply issues. Most of the topographic map in Figure 12.6 is red, indicating the new development that results in more water being withdrawn from the Floridan Aquifer. Many of the new structures are buildings much larger than the size of a typical home, so they may be businesses using more water per day than an average family. Increased pumping and withdrawal of water from the aquifer is reducing the amount of water that reaches Sulphur Springs. 2. Student answers will vary widely but should reflect an understanding of groundwater quality issues. Greater development of the land produces greater amounts of runoff from roads, parking lots, construction sites, lawns, landfills, and storm drains. Such water contains motor oil, gasoline, trash, and other materials that may chemically or biologically contaminate the aquifer. Also, there are probably sewage pipes (that may leak) and on-site septic systems that provide sewage contamination of the aquifer. 12.3I. Reflect and Discuss: subsidence caused by formation of sinkholes flooding in areas of low elevation changes in groundwater level if drainage/supply problems change from human or natural factors possible contamination of groundwater (drinking water supplies) and streams (where people swim, fish, boat) 2015 Pearson Education, Inc. 133
135 ACTIVITY 12.4: Land Subsidence from Groundwater Withdrawal Background: For an excellent summary of USGS investigation of the hydrogeology of the Santa Clara Valley, refer to the following 1984 UNESCO Guidebook to studies of land subsidence due to ground-water withdrawal Case History No. 9.14, Santa Clara Valley, California, U.S.A., by Joseph F. Poland (U.S. Geological Survey, Sacramento, California): In the summary, Poland concludes that subsidence occurred because of a decline in the artesian head; thereby increasing the relative amount of overburden load on water-bearing strata in the confined system. He specifically notes that the clayey confining beds (aquitards) compressed the most, even though they have low permeability, and that the compression/compaction of strata was permanent. 12.4A. 1. in the center of the valley, near the towns of San Jose and Santa Clara 2. The subsidence from 1934 to 1967 was: 12.7 feet 4.6 feet = 8.1 feet. 3. The subsidence rate is 8.1 feet over 33 years, or 0.25 feet/year. 4. Either of these answers is possible: southeast of San Jose, where the subsidence contours are closest together (Figure 12.10), because this is where the most tilting of the land occurs near the southern end of San Francisco Bay, because increased subsidence will cause present land areas to be flooded 5. No. The darker areas are consolidated rocks that will not impact much if their groundwater is withdrawn. 6. The rate was (12.7 feet 9.0 feet) 7 years = 0.53 feet/year. 7. a. Water in the San Jose well was at the land surface in b. Water in the San Jose well was about 180 feet below the land surface in Extrapolation of the hydrograph curve (Figure 12.14) to the left suggests that the well may have been artesian before 1915 and that it flowed intermittently through about Pearson Education, Inc. 135
136 9. There are five fluctuations of equal duration between 1920 and 1925, so these are annual fluctuations caused by seasonal changes in recharge of the aquifer and by variations in discharge from the aquifer for irrigation. 10. From about 1938 to 1948, the water level in this well was above the average rate of subsidence, whereas in the other years, the water level in the well dropped about the same rate as the land subsided. The rate of land subsidence also decreased during the period of about 1938 to Reflect and Discuss: By 1937 the United States was recovering from the Great Depression and was initiating wartime manufacturing industries. Workers from depression-era farms flocked to higher-paying factory jobs created to manufacture war goods for U.S. allies in Europe and the Pacific. Also note the large increase in the well level during 1941, 1942, and The United States entered World War II in 1941 (when Japan attacked Pearl Harbor) and American men and women flocked to factories and to the military. Irrigation equipment and farm workers were in short supply, so groundwater withdrawal was much reduced and water levels rose in the well. 12. Reflect and Discuss: Some possible reasons are: development and use of groundwater conservation practices (voluntary regulation of water use) government and farm regulation of irrigation (government regulation of water use) land use practices may have changed, so fewer farms were available to irrigate more sources of water (dams, lakes, aqueducts from mountain sources) were developed, so reliance on groundwater was reduced Pearson Education, Inc.
137 LABORATORY THIRTEEN Glaciers and the Dynamic Cryosphere BIG IDEAS: Earth s crysphere is its snow and ice (frozen water), including permafrost, sea ice, mountain glaciers, continental ice sheets, and the polar ice caps. The extent of snow and ice in any given area depends on how much snow and ice accumulates during winter months and how much snow and ice melts during summer months. Glaciers are one of the best known components of the cryosphere, because they are present on all continents except Australia and have created characteristic landforms and resources utilized by many people. THINK ABOUT IT (Key Questions): What is the cryosphere, and how do changes in the cryosphere affect other parts of the Earth system? (Activity 13.1) How do glaciers affect landscapes? (Activities 13.2, 13.3) How is the cryosphere affected by climate change? (Activities 13.4, 13.5, 13.6) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser metric ruler (cut from GeoTools sheet 1) calculator (or provided by instructor) pocket stereoscope (or provided by instructor) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 13.1: Cryosphere Inquiry none ACTIVITY 13.2: Mountain Glaciers and Glacial Landforms extra metric rulers (for students who forgot them) ACTIVITY 13.3: Continental Glaciation of North America none 2015 Pearson Education, Inc. 137
138 ACTIVITY 13.4: Glacier National Park Investigation none ACTIVITY 13.5: Nisqually Glacier Response to Climate Change extra metric rulers (for students who forgot them) ACTIVITY 13.6: the Changing Extent of Sea Ice extra metric rulers (for students who forgot them) pieces of string about 30 cm or 12 inches long for students (or obtained by students) LAB 13 ANSWER KEY ACTIVITY 13.1: Cryosphere Inquiry 13.1A. 1. First: easonal snow Second: permafrost discontinuous with mountain glaciers/ice caps Third: permafrost continuous with mountain glaciers ice caps Fourth: sea ice (polar) 2. For glaciers to exist at/near the equator, there must be a source of moisture and mountains high enough to achieve freezing temperatures. 3. If global temperature were to rise, then more cryosphere would melt, and the water would be added to the hydrosphere. Places that were too cold for most life to survive would become warmer, diversity of life could increase there, and growing seasons would be longer in high latitude zones. 4. If global temperature were to fall, then the amount of cryosphere would increase. There would be less water in the hydrosphere as more and more of the hydrosphere would be converted to ice and stored in the cryosphere. Places that were warm enough to support a high diversity of life would become colder, so the diversity of life there would decrease and growing seasons would get shorter Pearson Education, Inc.
139 13.1B. 1 to 4. See the image below. 5. The glaciers seem to be receding, so there is a net negative mass balance; however, it would be good to have images from several different years in order to compare trends in advance or retreat of the glaciers and extent of the zone of accumulation before deciding the answer to this question. 13.1C. 1. The zone of ablation in this image occurs where there is no pure white snow/ice, but there is gray stagnant ice that is melting. As it melts, sediment that was inside of the glacier accumulates on the ice and makes it look dirty. In places where the ice has melted completely, only the sediment remains. 2. Resources include: ice, water, and gravel/sand. 13.1D. Reflect and Discuss: The glaciers carve out river valleys and make them wider and more U-shaped, wear away the surface of the landscape as if it were sanded by a giant sheet of sandpaper, and leave behind lakes and bodies of sediment when they melt. The presence of lakes, glacial sediment, and wide valleys with smooth sides suggests that the glaciers here were more extensive in the past Pearson Education, Inc. 139
140 ACTIVITY 13.2: Mountain Glaciers and Glacial Landforms 13.2A. 1 and 2. See below. 3. S-T: The river cuts downward (apex of the V) and the sides of the valley slump toward the river. 4. G-L: Glacial ice scours the entire valley surface, rounding the V-shape into a U-shape. 5. a and b. See the profile on the previous page. c. The glacier would probably be 1000 to 1500 feet thick, depending on how students drew it. 13.2B. 1. The best place to look for gold would be location X, because a medial moraine connects C with X. 2. They are transverse crevasses that formed where the glacial ice descends over a break in slope, as indicated by the topographic contour lines on the ice surface Pearson Education, Inc.
141 13.2C. This is a hanging valley, formed when the glacial trough of a tributary glacier did not erode down to the same level as the main valley glacier that it was merging into. 13.2D. Reflect and Discuss: Based on the map from 1960 and the satellite image from 2000, Harvard Glacier had a positive mass balance. The glacier was advancing farther down the valley in 2000 than it was in 1960 and also seems to be thicker. ACTIVITY 13.3: Continental Glaciation of North America 13.3A. 1. drumlins: elongated mounds or ridges of glacial till (unsorted drift) that accumulated under a glacier and was elongated and streamlined by movement (flow) of the glacier 2. esker: a long, narrow, sinuous ridge of stratified drift deposited in a meltwater stream flowing under glacial ice or in tunnels in the ice 3. Based on the orientation of the drumlins, the glacial ice flowed towards the southwest (from the northeast) here. 13.3B. 1. drumlins and ground moraine in the northwest quadrant of the map terminal or recessional moraine in the southeast quadrant of the map marshes and swamps kettle holes (kettle lakes) 2. The ice probably flowed from north to south (or north-northwest to southsoutheast) over this region, based on the asymmetrical shapes of the drumlins and the location of the terminal/recessional moraines. 3. Some are human-made lakes created by dams on rivers (e.g., Cushman Pond). Some are kettle lakes that formed where chunks of glacial ice were isolated in deposits of ground moraine, whereupon they melted to form waterfilled depressions (e.g., Rome Pond, Blue Springs Lake). 4. a terminal or recessional moraine with scattered kettle holes 5. This feature could be a swale, but students may regard it simply as a poorly drained area between two recessional moraines. It is possible that at some point in the past this marshy area was an ice-margin lake. 13.3C. Reflect and Discuss: Answers vary from student to student. Discuss this in small groups or brainstorm as a class Pearson Education, Inc. 141
142 ACTIVITY 13.4: Glacier National Park Investigation 13.4A. cirques with cirque glaciers aretes finger lakes (like Quartz Lake) U-shaped valleys (glacial troughs) horns cols 13.4B. a. The valley of Quartz Lake was filled and scoured by a valley glacier. b. As the valley glacier retreated (melted), it paused near the location of the Patrol Cabin where a recessional moraine was deposited (the piece of land on which the Patrol Cabin is now located). c. The valley glacier then retreated up valley, so that only small cirque glaciers remain of it today. d. Rain and melt water from snow and the cirque glaciers are trapped behind the recessional moraine to form Quartz Lake (a finger lake). 13.4C. mountain glaciation 13.4D. 1. There are more glaciers and lakes on, and west of, the Continental Divide than east of it. 2. Moist air rising over the Rocky Mountains here must rise, cool, and condense to form rain and snow. As the air travels east of the Continental Divide, it is drier, so there is less precipitation there. 13.4E. The size (area in km 2 ) of Agassiz Glacier decreased from 1850 to 1993, but it stayed about the same from 1993 to F. The size (area in km 2 ) of Vulture Glacier decreased from 1850 to 1993, but it increased slightly from 1993 to G. Reflect and Discuss: Based on the data in parts E and F, above, one might expect the trend of the glaciers to be staying the same or increasing in size. However, the 2005 data could be a short-lived phenomenon. With other glaciers throughout the world mostly decreasing in mass balance, one might expect the same to be true of these glaciers Pearson Education, Inc.
143 ACTIVITY 13.5: Nisqually Glacier Response to Climate Change 13.4A. Student data varies, so student graphs also vary somewhat in terms of numerical values. However, general trends in the student graphs will be the same, as follows: The glacier generally retreated up the valley from 1850 to The glacier advanced down the valley from 1963 to The glacier retreated up the valley from 1968 to The glacier advanced down the valley from 1974 to The glacier has retreated up the valley since B. From 1880 to about 1963, Nisqually glacier generally retreated up the valley as averaged global land surface temperature increased. The sharp return to coolerthan-average temperatures in 1963 (blue) is marked by a sharp advance of the glacier (with one minor retreat that correlates to a warming in the early 1970s). The sharp return to warmer-than-average temperatures (red) in 1976 is marked by a sharp return to retreat of the glacier. 13.4C. 1. The long-term trend in averaged global land surface temperature, from 1880 to 2011, was warming from about 8 C to 9 C, or 47 F to 48 F. 2. Students recognize two intervals of cooler-than-average temperatures (1880 to about 1935; 1963 to 1976) and two intervals of warmer-than-average temperatures (1935 to 1963, 1976 to now). 13.4D. The long-term (century) trend of Nisqually glacier retreat up the valley correlates with the long-term warming trend in averaged global land surface temperature that has occurred since Since about 1960, Nisqually glacier also shows a close correlation with the short-term (decades) cycles of cooling climate (glacial advance) and warming climate (glacial retreat). Since the advances and retreats of Nisqually glacier seem to correlate with changes in averaged global land surface temperatures, Nisqually glacier is like a global thermometer. 13.4E. Reflect and Discuss: Student answers will vary considerably but must use logic and evidence (from above) to justify a persuasive explanation Pearson Education, Inc. 143
144 ACTIVITY 13.6: the Changing Extent of Sea Ice 13.6A. 1. Answers will vary according to how carefully and exactly the students collected their data. There is also some confusion about how to measure the area of sea ice where it occurs with islands. This can lead into a discussion of how data can be collected by pixel rather than by physically measuring by hand. Nevertheless, most students will get a sea ice circumference of 10,000 12,000 km. Using a circumference value of 11,000 km, the radius is 1752, and the square kilometers is 9,638,243 km Answers will vary, as noted above; however, students tend to get a sea ice circumference of kilometers. Using a circumference value of 7500 km, the radius is 1194, and the square kilometers is 4,476,497 km Answers will vary, but check to be sure that students correctly calculate the rate of sea ice decline in km per year. Using the data above: (9,638,243 km 2 minus 4,474,497 km 2 ) (2012 minus 1979 yr) = 156,477 km/yr 13.6B. 1. See graph below. 2. ( ) 8 = 41.1/8 = 5.1 million km 2 3. ( ) 6 = 28.6/6 = 4.8 mllion km Pearson Education, Inc.
145 4. Comparing answers in parts B1, B2, and B3, above, the extent of Arctic sea ice is decreasing. 5. Extrapolating the graph above, one might expect that the extent of sea ice in 2015 will be about 4.3 million km 2 ; however, there is annual variation of about +/- 1 million km 2, so it could be million km See the graph above. 7. ( ) 8 = 18.9 million km 2 8. ( ) 6 = 19.2 mllion km 2 9. Comparing answers in parts B6, B7, and B8, above, the extent of Antarctic sea ice is increasing slightly. 13.6C. Reflect and Discuss: Answers will vary widely. Obviously, the factors affecting the extent of Arctic and Antarctic sea ice are not all the same. Some students notice that Arctic sea ice is surrounded by continents and many islands, whereas the Antarctic sea ice occurs around the fringes of one continent. Circulation of wind/ocean currents may also be different. Allow students to speculate and hypothesize. Those with Internet access can find some of the latest research/thinking by scientists on this issue. Be sure they describe at least one hazard of decreasing Arctic sea ice (such as decline of ice on/around which many polar mammals live and migrate) and one benefit (a more navigable Arctic Sea) Pearson Education, Inc. 145
146 LABORATORY FOURTEEN Dryland Landforms, Hazards, and Risks BIG IDEAS: Drylands are lands of arid-to-dry, subhumid climates that generally have sparse vegetation and receive precipitation just a few days or one season of the year. Even so, water is one of the primary agents that produces characteristic dryland landforms and flood hazards. Wind is also a factor in the erosion and transportation of sediment, especially dust and the sand that makes dunes. Although many people live in drylands, true deserts do not support any agriculture without irrigation or a well. THINK ABOUT IT (Key Questions): What are some characteristic processes, landforms, and hazards of drylands? (Activity 14.1) What can we learn from topographic maps and satellite images about dryland processes and landforms? (Activity 14.2, 14.3) How can topographic maps and aerial photographs of drylands be used to interpret how their environments have changed? (Activity 14.4) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets attached to assigned activities laboratory notebook pencil with eraser set of colored pencils metric ruler (cut from GeoTools sheet 1) calculator (optional) computer or other electrical device with Internet access (Activity 14.1) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 14.1 Dryland Inquiry none ACTIVITY 14.2: Mojave Desert, Death Valley, California colored pencils (if not obtained by students) ACTIVITY 14.3: Sand Seas of Nebraska and the Arabian Peninsula colored pencils (if not obtained by students) Pearson Education, Inc.
147 ACTIVITY 14.4: Dryland Lakes of Utah calculator (or obtained by students) colored pencils (if not obtained by students) (optional) pocket stereoscopes LAB 14 ANSWER KEY ACTIVITY 14.1 Dryland Inquiry 14.1A. 1. The primary factor preventing plant growth is likely the fact that the sand is in motion each day, so plants do not have time to germinate and establish a system of supporting roots before they get eroded from the sand and die. Also, water drains rapidly through the sand, so there is little water available for plant growth. Finally, there is no topsoil. 2. The hazard created by the wind is not only the wind itself, but also blowing sand. Blowing sand fills the canal (which must be dredged to keep it open) and covers the road (from which it must be plowed). 3. Vehicle tires physically disrupt the land surface and even move sand and rocks about, so they accentuate the effects of sand movement and the hazards named above. Where plants do establish themselves, vehicles erode them from their habitat. Thus, there are fewer plant roots to trap and bind the sand. 14.1B. 1. When a heavy rain falls on the rocky surfaces of these steep mountain slopes, it cannot seep into the land. It runs off of the rocks surfaces and causes development of flash floods. 2. The rivers of these mountains only flow during infrequent rain events. Death Valley gets less than 2 inches of rain per year. Flash floods are channeled through the narrow channels of the river system and transport rock particles (called alluvium, or alluvial sediment) along with the water. When the floods enter the valley, the energized flood waters fans out over the valley, the energy level drops, and sediment settles out of the water as a deltalike deposit (called an alluvial fan). 3. Water flowing into Death Valley carries with it a minute percentage of chemicals dissolved from the rocks over which it flows. Rain events are rare, the climate is arid, and summers are the hottest in North America, so the water evaporates. As the water evaporates, the percentage of dissolved 2015 Pearson Education, Inc. 147
148 chemicals per volume of water increases. The water becomes alkaline to salty, and minerals like gypsum and halite may precipitate from it. 4. The white patches on the floor of Death Valley are evaporate minerals, the ones that precipitate from evaporating ponds and lakes as described above. The minerals include aragonite (calcite), gypsum, halite, and many others. 5. Furnace Creek is one of the few places in Death Valley where there are springs with abundant fresh water that is potable (drinkable). The little bit of rain water that soaks into the ground in the Amargosa Mountains (east of Death Valley), seeps down through cracks in the rock, and seeps out as springs at Furnace Creek. Many people flocked to the springs in the early 1900s, because they thought the springs restored health. 14.1C. 1. Rancho Mirage sits atop an alluvial fan like the one described in part B2. 2. Answers will vary according to the years viewed; however, the number of dwellings and other structures at Ranch Mirage has increased over the years. 3. There is a storm-water management system that is intended to divert flash floods around Rancho Mirage, and the uphill part of the community is a golf course rather than homes. 4. As in society at large, answers vary greatly according to the risk perceived by each student in relation to the flash flood hazard. 14.1D. Reflect and Discuss: There are many environmental barriers to living in drylands (lack of potable water, almost no rain for agriculture, little vegetation for human or animal consumption, shifting sand dunes and winds, flash floods, etc.). Developing/growing drought resistant plants, following strict land management practices (few grazing animals and people per acre), water conservation, and attention to flash flood hazards, are some of the things that people must do to live in drylands Pearson Education, Inc.
149 ACTIVITY 14.2: Mojave Desert, Death Valley, California 14.2A. 1 to 6. Refer to the next page for a completed map from lab manual p The lowest contour line on the map has an elevation of -260 feet. 8. The lowest elevation marked on the map is -265 feet (but playa lake E is lower even though its elevation is not marked). 14.2B. There would be very coarse grained sediments and boulders in the highest parts of the arroyo and alluvial fan. Storm/flood water loses its velocity as it spreads out over the alluvial fan, so its ability to carry large particles of sediment decreases rapidly. Thus, grain size would decrease as one walks down the alluvial fan. From the downstream end of the fan to the letter E, grain size would also decrease. Only silt and clay, plus evaporite minerals, would be expected at E. 14.2C. If there is a significant fault on the west side of the graben, then it should occur approximately at the leading edge of the mountain front and at the leading edge of the chain of inselbergs. There is not good evidence for such a fault, but students may draw one in as on the next page (dashed line). On the east edge of the graben, the main fault could be expected to occur along the mountain front, where there is a dramatic change in the slope of the valley wall and where alluvial fans C and D begin. This obvious fault has been labeled with a dashed line on the completed figure on the next page. The symbols U (up-side or horst-side of the fault) and D (down-side or graben-side of the fault) have been added to both dashed lines indicating faults. Most students do not infer a fault along the western side of Death Valley here, so they infer that the valley is a half graben. Students that infer faults on both sides of the valley will, alternatively, infer that the valley is a full graben Pearson Education, Inc. 149
150 14.2D. Reflect and Discuss: There is a mountain spring only a mile upstream from the fan (a source of drinking water that is not alkaline). The stream on alluvial fan C flows due south along the mountain front, so only the southern half of this fan is active with a significant flash flood hazard. This is the only fan with significant vegetation on it (notice the green coloring on the map), so it is moist enough for lawns, gardens, trees, and crops. Completed map from p. 370 ACTIVITY 14.3: Sand Seas of Nebraska and the Arabian Peninsula 14.3A. 1. Barchans and barchanoid ridges occur in this image. They developed due to the combination of fairly constant wind and limited sand supply. 2. The horns (tips) of barchans point downwind, which is south in this image Pearson Education, Inc.
151 14.3B. 1. The Sand Hills are bachans and barchanoid ridges similar in form to those of the Barren Quarter (but somewhat smaller). 2. If these large dunes of the Sand Hills were not active during the VERY dry and windy Dust Bowl, then desertification must proceed to conditions worse (drier and windier) than experienced here in the Dust Bowl. 3. Most have elevations of 4070 to 4190 feet and are developed on a surface of about 3900 feet in elevation, so their relief varies from 170 to 290 feet. 4. The steep slip faces of the megabarchans and barchanoid ridges face southeast, so the winds that formed them must have come from the northwest. 5. As wind blows over a region it erodes and carries sand-, silt-, and clay-sized grains of sediment. As the wind loses its velocity and energy the sand is deposited first, followed by the silt, and then the clay. Such eolian deposits of silt and clay are called loess (as in lab manual Figure 14.2). Since the Nebraska loess deposits are all southeast of the Sand Hills (eolian sand deposits), the source of the sand and loess must have been northwest of Nebraska. 14.3D. Vegetation is holding the sand in place and keeping dunes stable (from being activated), so it is important that grazing be kept to a minimum where some ground cover remains to trap and bind the sandy soil. It would be good practice to shift cattle from one field to another, or keep only a few cattle per acre, to insure that the land is not overgrazed. 14.3E. Reflect and Discuss: Cities in other parts of Nebraska may take steps to use water from the Sand Hills or east of the Sand Hills. Thus, less groundwater would be available to flow through the Sand Hills, and the Sand Hills could not sustain existing levels of vegetation. Thus, the Sand Hills would be likely to experience more desertification and all of the dunes could become active again. ACTIVITY 14.4: Dryland Lakes of Utah 14.4A. Wah Wah Valley Hardpan is a playa. 14.4B. The lowest elevation of the lake is 4637 feet and the highest point in the valley to the northeast is about 4670 feet (just above the dashed contour line for 4660 feet). So the lake would have to be 33 feet deep before it would overflow. Students could also say that the lake simply has to get deep enough that its level exceeds 4670 feet in elevation Pearson Education, Inc. 151
152 14.4C. They are ancient shorelines of the lake, from times when it was deeper. 14.4D. The deltas migrated basinward (toward the playa) as the lake level fell. Therefore, they appear as a line of deltas, rather than as one single delta with a typical triangular shape. 14.4E. Point X occurs at the highest level of shorelines resembling bathtub rings. There is a small escarpment (cliff) where the water of the lake cut into an alluvial fan. Its elevation is about 1510 feet on the topographic map. 14.4F. The fans at the Z points are younger than the ancient shoreline, because they cut across the ancient shoreline. 14.4G. See the completed map on the next page. The shoreline is drawn as a dark blue line at an elevation of 5110 on the completed figure on the next page of this book. The area covered by parallel, light blue lines was submerged by the lake. 14.4H ,000 years old 2. Using an elevation of 5110 feet from part E above: 5110 ft 4200 ft = 910 ft, and 910 ft + 30 ft = 940 feet Using an elevation of 5100 feet from the Utah Geological Survey and U.S. Geological Survey: 5100 ft 4200 ft = 900 ft, and 900 ft + 30 ft = 930 feet 17,000 years ago, the Great Salt Lake was about feet deep. 14.4I. Reflect and Discuss: Over the past 17,000 years, the climate of Utah must have fluctuated between times of high rainfall (when lake levels were high: like 17,000, 16,000, and 12,000 years ago) and times of more arid conditions with little rainfall (like now, with lower lake levels) Pearson Education, Inc.
153 Completed figure from page 374 (Part 14.4 G) Dark blue lines are shorelines. Light blue lines show the extent of the lake water Pearson Education, Inc. 153
154 LABORATORY FIFTEEN Coastal Processes, Landforms, Hazards, and Risks BIG IDEAS: A coastline is the boundary between land (geosphere) and the ocean or a lake (hydrosphere), but it is also affected by the atmosphere, organisms (biosphere, including humans), and sometimes glaciers (cryosphere). The shapes of coastal landforms depend on how the land is affected by the other spheres. Specific factors like waves, erosion, sediment supply, storms, and sea-level changes, are particularly effective in shaping coastal landforms and may pose hazards to humans or their property. Therefore, artificial structures are used to manage shorelines and protect coastal properties. THINK ABOUT IT (Key Questions): What factors affect the shape and position of shorelines? (Activities 15.1, 15.2) How successful are efforts to protect shorelines from erosion by building artificial structures? (Activity 15.3) How will rising sea levels affect communities along shorelines? (Activity 15.4) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets attached to assigned activities laboratory notebook pencil with eraser set of colored pencils metric ruler (cut from GeoTools sheet 1) calculator (optional) computer or other electrical device with Internet access (Activity 14.1) INSTRUCTOR MATERIALS (Check off items you will need or provide.) ACTIVITY 15.1 Coastline Inquiry none ACTIVITY 15.2: Introduction to Shorelines none Pearson Education, Inc.
155 ACTIVITY 15.3: Shoreline Modification at Ocean City, Maryland none ACTIVITY 15.4: The Threat of Rising Seas none LAB 15 ANSWER KEY ACTIVITY 15.1 Coastline Inquiry 15.1A. 1. a. This coastline is saltmarsh plants rooted in mud and sand. It has a very low slope, so it would be much affected by tidal changes, storms, and waves that could erode the marsh. b. This coastline is very rocky. Not much can erode it except for the constant pounding of daily waves and storms. c. This coastline is a sandy delta. A river carrying sand enters the ocean here, and the sand is deposited as a delta. The shoreline is affected by the amount of sediment carried there by the river and waves, currents, storms that affect the shape of the delta. d. This North Carolina coastline is a sandy beach. It is affected by waves and storms (hurricanes) that move the sand. e. This urbanized coastline is sandy, and the sand is covered by homes that sit right on the beach. Waves and storms (hurricanes) move the sand and, perhaps, the homes. f. This Florida coastline is a mass of mangrove roots that normally buffer wave energy and protect the shoreline from erosion. However, storms (hurricanes) could erode them and modify the shape of the shoreline. g. This Maine coastline is a beach made of large (1/2 to 2 meters in diameter) rounded rocks. Only strong storm surges could move them. New rocks can be added as they fall from the adjacent rocky cliff. h. This Caribbean coastline is made of coral. It is affected by growth of the coral and the action of organisms that break the coral apart (fish, sea urchins, boring organisms). Storms (hurricanes) can also break apart coral and erode the coastline Pearson Education, Inc. 155
156 15.1B. Reflect and Discuss: 15.1C is a coastline with a delta. As the river adds sand to the coastline, it accumulates faster than it can be eroded by waves and tidal currents. 15.1D is a sandy coastline that is receding. Notice the sandy cliff, where storm waves eroded the shoreline faster than sand could be added from up or down the coast. ACTIVITY 15.2: Introduction to Shorelines 15.2A. 1. The distance from the town of Adria to the mouth of the Po River is about 40 km. So the rate of delta progradation is 40 km over 2600 years ( ). 40 km is 40,000 meters and 4,000,000 cm, so the rate of delta progradation is: 4,000,000 cm / 2600 yr = 1538 cm/yr 2. Over 60 years, the delta would prograde 92,280 cm (992.8 meters, 0.92 km). 3. Reflect and Discuss: The river supplies so much sediment to the delta that it continues to build up and seaward in spite of sea level rise. 15.2B. 1. salt marsh mud 2. The ocean has advanced landward over the salt marsh, killing and removing the salt marsh plants and leaving only bare relict salt marsh mud partly covered by beach sand. 3. washover fans 4. The fact that the ocean is advancing over salt marsh indicates that it is advancing toward, and drowning, the land. Aaron s Hill will be eroded away if this process continues. 5. No, Aaron s Hill would not be a good location for a beach resort. If the hill can erode away, then the hotel on the hill would be undermined and would collapse. 6. Reflect and Discuss: The living salt marsh will eventually be covered and killed by sand of washover fans and/or it will be killed and eroded by the advancing ocean currents (like the relict salt marsh mud on the east side of Figures 15.6A and B) Pearson Education, Inc.
157 ACTIVITY 15.3: Shoreline Modification at Ocean City, Maryland 15.3A. Sand has accumulated on the north side of the jetty (at the south end of Fenwick Island where Ocean City is located). The sand must have been transported there by longshore currents moving from north to south. 15.3B. 1. The jetty described above (at the southern end of Ocean City on Fenwick Island) prevents sand from reaching the northern end of Assateague Island. (The mouth of the inlet is dredged by the Army Corps of Engineers to keep it open despite the jetty.) Therefore, sand removed from Assateague Island is transported south by the longshore current and is essentially not replaced at nearly the rate it is removed. The net result is that the northern end of Assateague Island is shrinking and migrating westward. 2. Recall that, until 1933, Fenwick Island looked like the 1849 black-pen outline in the Figure Other parts of Figure 15.7 were photorevised in Fenwick Island migrated westward about 0.3 to 0.4 mile over the period of , its rate of westward migration has been: 0.3 to 0.4 mile/ 39 yr = 1584 to 2112 feet / 39 yr = 41 to 54 ft / yr = 12.5 to 16.5 m / yr 3. The lagoon behind Fenwick Island is only about one-fourth of a mile wide (1320 ft, 402 m). So the island will merge with Ocean City Harbor in: 1320 feet ft/yr = 32 to 24 years 4. The channel is kept open by strong tidal currents and human dredging. 15.3C. 1. The groins trap sand that is moving south along the coastline. Beaches get wider as the sand accumulates. 2. Sand trapped by the groins north of Ocean City s Municipal Pier will never make it to the south end of the island to build up the Municipal Pier area. 15.3D. Now that the north end of Assateague Island has receded west, the southern end of Fenwick Island is exposed and vulnerable to a hurricane approaching from the south. 15.3E. Although the northern end of Assateague Island remained in a stable position from 1972 to 2010, parts further south did not. At the bottom of Figure 15.7, it is evident that the island migrated landward by as much as 0.3 km (300 meters). There are many reasons why this could have happened. Allow students to suggest multiple hypotheses related to lack of sediment supply, the effects of storms/waves, etc Pearson Education, Inc. 157
158 15.3F. Reflect and Discuss: Removing all of the groins, jetties, and sea walls around Ocean City would likely lead to loss of sand from Fenwick Island, addition of sand to the northern end of Assateague Island, and perhaps even a closure of the inlet and a return to shoreline that existed in 1849 on Figure ACTIVITY 15.4: The Threat of Rising Seas 15.4A. 1. a mm/yr b mm/yr 2. a mm b in. c mm d in. 3. On a day when a storm surge is combined with a high tide, sea level will rise 3.9 feet and put the ocean at the front door of the home, which is 4 ft above sea level. Any additional rise in sea level combined with these effects will put the ocean inside the home. 4. Even a Category 1 hurricane will raise sea level 4 feet, which is the elevation of the home's front door. So, it would not be wise to purchase this home. 5. Reflect and Discuss: A combined storm surge and 3-foot rise in sea level could cause sea level to often be located about 9 feet higher than present sea level. Therefore, new construction should not be done below the 10-foot topographic contour line if it is for permanent and/or not easily moved structures that can be damaged by flooding. In fairness to Ocean City s planners, you can inform your students that since 1972 all homes in flood-prone parts of Ocean City must be constructed on pilings so they are elevated above ground level about one story high. Have students discuss whether or not this is a reasonable solution to flooding problems, given the fact that pilings are easily eroded, decayed, or bored by organisms (and wind damage is generally severe in hurricanes). This provision may also actually encourage development in high-risk, flood-prone areas Pearson Education, Inc.
159 LABORATORY SIXTEEN Earthquake Hazards and Human Risks BIG IDEAS: Earthquakes are vibrations of Earth that occur naturally when magma moves beneath volcanoes, volcanoes erupt, or rocks suddenly rupture along faults. The vibrations radiate outward as seismic waves, which are detected at seismic stations and recorded as seismograms. The seismograms can be used to calculate distance from the earthquake, and seismograms from three or more seismic stations can be used to determine where the earthquake occurred. Geologists use models to study the effects of earthquakes on natural materials and human structures and mitigate earthquake hazards. THINK ABOUT IT (Key Questions): How do bedrock and sediment behave during earthquakes and how does this affect human made structures? (Activity 16.1) How can seismic wave data be used to locate the epicenter of an earthquake? (Activities 16.2, 16.3) How do geologists use remote sensing, geologic maps, seismograms, and first motion studies to analyze fault motions? (Activities 16.4, 16.5) STUDENT MATERIALS (Remind students to bring items you check below.) laboratory manual with worksheets linked to the assigned activities laboratory notebook pencil with eraser metric ruler (cut from GeoTools sheet 1 or 2) calculator drafting compass INSTRUCTOR MATERIALS (Check off items you will need to provide.) ACTIVITY 16.1: Earthquake Hazards Inquiry several coins per student (pennies, nickels) small cups containing dry sand (two per group of students) wash bottles (one per group of students) ACTIVITY 16.2: How Seismic Waves Travel through Earth none 2015 Pearson Education, Inc. 159
160 ACTIVITY 16.3: Locate the Epicenter of an Earthquake drafting compasses (or provided by students) ACTIVITY 16.4: San Andreas Fault Analysis at Wallace Creek none ACTIVITY 16.5: New Madrid Blind Fault Zone none LAB 16 ANSWER KEY 16.1A. 1. When an earthquake was simulated with Model 1 (uncompacted/unconsolidated sediment), some coins fell on their side and/or sank into the sediment. 2. When an earthquake was simulated with Model 2 (compacted sediment), some coins lean over, but most remain in their original position before shaking. 3. Uncompacted sediment is more hazardous because structures constructed on/in it are not well anchored and sink or fall over. 4. More. Adding more water causes liquefaction. 5. Reflect and Discuss: Homeowners who have their homes constructed on uncompacted sand and landfills are at risk. Their homes are not well anchored, so they face the risk of having their homes fall down or sink into the uncompacted sediment in a major earthquake. 16.1B. 1. The risk at location X is low. Little or no damage would be expected because the apartment buildings would be constructed on hard rigid Franciscan Sandstone that should behave like the compacted rigid sediment in Model The risk at location Y is high. Damage can be expected because the apartment buildings would be constructed on uncompacted beach and dune sands that would probably behave like Model The risk at location Z is high. Damage can be expected, because the apartment buildings would be constructed on debris/rubble that would probably behave like Model Pearson Education, Inc.
161 16.1C. 1. The ground at location X is rigid rock, so the shaking was not noticeable (as one would expect based on Model 2 and the answer to Question 16.1B1). However, the ground at locations Y and Z is loose, uncompacted materials that moved about during the earthquake and accentuated the shaking (as one would expect based on Model 1 and answers to Questions 16.1B2 and 16.1B3). 2. The ground at location Y was uncompacted, loose sand, but the sand at location X has been hardened into rock (sandstone). Therefore, location Y behaved like Model 1 and location X behaved like Model 2. Earth shaking and damage to buildings occurs more on uncompacted/loose materials than on compacted/rigid materials. 16.1D. Reflect and Discuss: To avoid the hazard: Map/locate hazardous areas. Modify building codes to prevent construction on hazardous substrates. To adapt to the hazard: Tamp (pack down) fill areas to make them firmer to build on. Anchor buildings to rock or firm clay under the sand/fill (with steel pilings). ACTIVITY 16.2: How Seismic Waves Travel through Earth 16.2A. The points fall in discrete paths that represent seismic P-waves, S-waves, and L-waves. Regardless of when and from what earthquake they originate, these waves travel through Earth in the same way every time. Also, Earth s internal variations (concentric layering) in density with depth must be essentially the same everywhere (like the concentric layers of crust, mantle, and core). 16.2B. The S-wave curve is steeper than the P-wave curve because the P-waves travel faster (and arrive at recording stations sooner) than the S-waves. 16.2C. L-waves are surface waves that travel only through rigid crustal rocks. The P- waves and S-waves are body waves. They speed up as they travel deeper inside Earth (through progressively denser rocks) and then slow down again as they approach Earth s surface at a recording station. This gives them a curved distance/time path. 16.2D. As distance from the epicenter increases, so does the S-minus-P time interval Pearson Education, Inc. 161
162 16.2E minutes 2. about 3200 km 3. You would need data from two or more additional stations, so you can triangulate to a single epicenter. ACTIVITY 16.3: Locate the Epicenter of an Earthquake 16.3A. First P First S S-minus-P arrival arrival time interval Sitka, AK 8:07.4_ 8: minutes Charlotte, NC 8:08.5 8: minutes Honolulu, HI 8:09.4 8: minutes 16.3B. Sitka, AK about 2700 kilometers Charlotte, NC about 3500 kilometers Honolulu, HI about 4500 kilometers 16.3C. When students determine the epicenter of this earthquake, their arcs may intersect in a triangle rather than a point. The epicenter would be the center of the triangle. Ideally, the arcs will intersect at a point in southern California at about: 34 N latitude 118 W longitude 16.3D. San Andreas fault Pearson Education, Inc.
163 ACTIVITY 16.4: San Andreas Fault Analysis at Wallace Creek 16.4A. 1 and 2. See the completed aerial photograph ahead. 3. The San Andreas fault has offset the modern course of Wallace Creek by meters. 4. If you stand on the southwest side of the fault in the image below, then the northeast side of the fault seems to have moved Wallace Creek to the right. Thus, the San Andreas fault is a right-lateral fault. 16.4B. about 10 meters or less 16.4C. Reflect and Discuss: This feature closely resembles the offset river valley to the southeast on the same side of the fault (in which the offset part of Wallace Creek now flows). Therefore, the feature is an ancient offset river valley (probably one in which Wallace Creek once flowed) Pearson Education, Inc. 163
164 ACTIVITY 16.5: New Madrid Blind Fault Zone 16.5A. See the completed map below. 16.5B. See the map below. 16.5C. Reflect and Discuss: The fault has a right-lateral motion. Stress moves from the field of dilation to the field of compression. So, notice above that stress on the northwest side of the fault zone moved south to north, and stress on the southeast side of the fault zone moved north to south. If you stand on one side of this fault zone and look across to the other side, then the other side appears to have moved to the right, so this is a right-lateral fault zone Pearson Education, Inc.
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Page 1 of 13 EENS 1110 Tulane University Physical Geology Prof. Stephen A. Nelson Continental Drift, Sea Floor Spreading and Plate Tectonics This page last updated on 26-Aug-2015 Plate Tectonics is a theory
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