World Beneath Our Feet

Transcription

1 World Beneath Our Feet Lesson Plan 2: Rock Identification Learning Objective Time required Learning Outcomes Materials (provided) Materials (Teacher supplied) background Suggested Procedure Students will evaluate the properties of rocks and record their results to identify mystery specimens. 2-4 lessons Students will discover that rocks are aggregates of one or more mineral. Students will understand that a rock can be named and classified by identifying its minerals and observing its textures Students will develop an understanding of key terminology used in rock identification. Students will become more confident in their rock identification abilities. Rock Identification Flow Charts Sedimentary, Igneous and Metamorphic Rock Information Sheets hand lens (15 use those provided in Activity 1) bottle dropper (1 for acid / carbonate test) sample rocks of identification (10 bags Each contains a sedimentary, igneous and metamorphic rock) Teacher Response Guide copies of Rock Identification Flow Charts (Figure 1 to be photocopied for each student) Vinegar (for acid / carbonate test) tissue for blotting (for acid / carbonate test) Earth is comprised of three types of rock sedimentary, igneous and metamorphic. Each type of rock exhibits specific characteristics that are used by geologists to help them identify specimens. Many of these characteristics are a direct result of how the rock was formed (the rock cycle). Understanding and identifying rock is an important geological skill that takes many years to master. Note: This activity is to be started in groups of three. 1. Provide each group of students with a specimen bag containing three rock specimens and copies of the Rock Information Sheets and the Rock Identification Flow Chart (Figure 1 only). 2. Have students review the Rock Information Sheets and follow the instructions on the flow chart to identify each of their specimens. Each bag contains an igneous, metamorphic and sedimentary rock. To perform a carbonate test (if required), have students place 1-2

2 drops of vinegar on their specimen. Observe if there is an immediate reaction. Blot up the remaining vinegar. 3. Have students record their observations as they complete each step in the chart. 4. When students have reached a consensus and think they have correctly identified their three rocks, have them trade specimens with another student group, and repeat steps 1-3 to verify each other s results. If they agree, have students check their results with the teacher. If they disagree, have them review their observations and see if they can identify where their research differs. 5. Once students have had some practice using the Rock Identification Chart, have each member of the group select one of the three rocks: sedimentary, igneous or metamorphic rock. Have students form new groups (taking their sample with them), based on the type of rock they have selected. In their new groups, students are going to become experts on one of the three rock types. (Note: depending on class size, you might want to break these three large groups into smaller working groups, but it is important they see the full range of specimens provided.) 6. Distribute to each group a copy of the relevant Rock Flow Chart (figures 2,3 and 4). Using the Rock Information Sheets previously distributed, see if you can further classify the rock specimens provided. Look closely at the various specimens to determine some of the key characteristics of each type of rock. 7. Have students write up a summary of the key characteristics of sedimentary, igneous and metamorphic rock (whichever one their group is studying). If there is time, have students prepare a brief presentation to the rest of the class about the specific characteristics of their type of rock. Continuing the Journey Have students complete a more in-depth research project about the rock cycle or one specific type of rock (sedimentary, igneous or metamorphic). Discuss common characteristics of each type of rock and how these relate to the manner in which the rock was formed. Include the following steps: Develop a research question and a plan to execute their research project (i.e. identify how/what sources they plan to use in their research project) Complete their research, keeping a research journal throughout. What unexpected surprises or obstacles affected their research process? How did they solve these problems? What would they do the same (or differently) next time they start a research project? Have students share their research findings this can be in the form of a scientific poster for a mock geology conference in class; an article for a print or on-line student journal; an oral / PowerPoint presentation to the class; or develop a webpage about their mineral.

3 specimen number rock name specimen bag #1 R 1-1 R 1-2 R 1-3 specimen bag #2 R 2-1 R 2-2 R 2-3 Igneous, Gabbro Metamorphic, Schist Sedimentary, Mudstone Metamorphic, Slate Sedimentary, Conglomerate Igneous, Pumice REsponse guide specimen bag #3 R 3-1 R 3-2 R 3-3 Sedimentary, Fossilferous Limestone Igneous, Granite Metamorphic, Phyllite specimen bag #4 R 4-1 R 4-2 R 4-3 specimen bag #5 R 5-1 R 5-2 R 5-3 specimen bag #6 R 6-1 R 6-2 R 6-3 specimen bag #7 R 7-1 R 7-2 R 7-3 specimen bag #8 R 8-1 R 8-2 R 8-3 specimen bag #9 R 9-1 R 9-2 R 9-3 Metamorphic, Gneiss Sedimentary, Sandstone Igenous, Obsidian Igneous, Syenite Metamorphic, Schist Sedimentary, Conglomerate Sedimentary, Fossilferous Mudstone Igneous, Vesicular Basalt Metamorphic, Slate Igneous, Granite Metamorphic, Gneiss Sedimentary, Fossilferous Limestone Metamorphic, Schist Sedimentary, Sandstone Igneous, Pegmatite Sedimentary, Mudstone Igneous, Porphyry Metamorphic, Gneiss specimen bag #10 R 10-1 R 10-2 R 10-3 Igneous, Granite Metamorphic, Schist Sedimentary, Limestone

4 Terminology igneous rock Igneous rock (from the Latin word ignis meaning fire) forms when magma or lava cools and hardens. This process is call crystallization. The rate of cooling determines the texture of the rock. There are two main types of igneous rock intrusive and extrusive. metamorphic rock A metamorphic rock is one that literally has changed its form (from the Greek meta meaning change and morphe meaning form). When igneous, sedimentary, or even existing metamorphic rock is exposed to high temperature and pressure deep inside Earth, a new metamorphic rock is formed. mineral A naturally occurring solid with a specific chemical composition (types of atoms) and a specific structure (a regularly repeated internal arrangement of its atoms). non-silicates Common non-silicates are carbonates, sulfates, chlorides and oxides. rock A naturally occurring solid composed of one or more silicate or nonsilicate minerals. A rock can be named and classified by identifying its minerals and observing the textures. sedimentary rock Sedimentary rock is composed of grains that have been derived from previously existing rocks. Weathering of previously existing rocks can result in grains being separated from the rock or in chemical compounds being put into solution. These two processes result in two main classes of sedimentary rocks: Clastic sedimentary rocks are composed of rock fragments, mineral grains, organic remains and the fine material that cements them and Chemical sedimentary rocks are precipitated from seawater or salt lakes, sometimes through the activities of living organisms. silicates Common rock-forming silicate minerals are quartz, feldspars, micas, pyroxenes, amphiboles, olivine and garnets.

5 Igneous Rocks Magma is melted rock formed deep in Earth s crust or upper mantle. Rock must be heated temperatures of at least 700 degrees Celsius before it melts. Some rocks do not melt until 1000 degrees is reached. Lava is the name given to molten rock that reaches Earth's surface. Igneous rock (from the Latin word ignis meaning fire) forms when magma or lava cools and hardens. This process is called crystallization. The rate of cooling determines the texture of the rock. There are two main types of igneous rock intrusive and extrusive. Intrusive or plutonic igneous rock is formed inside Earth where the magma cools and crystallizes slowly. Therefore, this type of igneous rock often has large, interlocking crystals. Granite is a good example of intrusive igneous rock. Extrusive or volcanic igneous rock is formed when lava erupts at the surface and cools quite quickly, such as during a volcanic eruption. Rapid cooling allows little or no time for crystals to grow. Therefore, this type of igneous rock can be recognized by its glassy or very fine-grained texture. Basalt is a good example of extrusive igneous rock. Classification of igneous rocks is based on the presence or absence of three key minerals: quartz, nepheline, and olivine. Other important minerals found in igneous rock are: muscovite, biotite, feldspar, hornblende, clinopyroxene and orthopyroxene. Many other minerals occur in minor amounts. Igneous rocks are classified as felsic or mafic on the basis of the ratio of light to dark minerals.

6 Metamorphic Rocks A metamorphic rock is one that literally has changed its form (from the Greek meta meaning change and morphe meaning form). When igneous, sedimentary, or even existing metamorphic rock is exposed to high temperature and pressure deep inside Earth, a new metamorphic rock is formed. Sometimes new minerals can grow, the chemistry can change, and characteristic textures can develop. Metamorphism occurs during plate tectonic processes such as mountain building and subduction. When plates collide, high pressure and temperatures result and distinctive textures and structures are recorded by the metamorphic rocks that form. Some metamorphic rocks have a distinct foliation, planes caused by the growth of sheety minerals parallel to one another and the alignment of other mineral grains. Distinct layers can develop in a metamorphic rock when the felsic minerals (light coloured) are separated from the mafic minerals (dark coloured).

7 Sedimentary Rocks Sedimentary rock is composed of grains that have been derived from previously existing rocks. Weathering of previously existing rocks can result in grains being separated from the rock or in chemical compounds being put into solution. These two processes result in two main classes of sedimentary rocks: Clastic sedimentary rocks are composed of rock fragments, mineral, grains, organic remains and the fine material that cements them and Chemical sedimentary rocks are precipitated from seawater or salt lakes, sometimes through the activities of living organisms. The grains and chemical compounds produced during weathering are transported by the processes of erosion, which loosen and carry the grains and compounds away to the place where they are deposited or precipitated. Sediments are deposited in layers upon surfaces of valleys and plains or at the bottom of rivers, lakes, and oceans. Over time, these layers of sediment form new rock, through a process called lithification. Lithification can occur by compaction (grains are pressed together by the weight of sediment on top) or by cementation (minerals are deposited from solution between grains to bind (glue) the sediment together). Textures and structures give important clues about the environment where the sediment was deposited. Sedimentary rock may contain visible fossils.

8 Rock Identification Chart - Fig. 1 Are there fossils in the rock? sedimentary rock (see Fig. 4) Can you see individual particles in the rock? Are they grains? Are they crystals? Is it glass? sedimentary rock (see Fig. 4) metamorphic rock (see Fig. 3) Are the crystals arranged in a regular pattern? igneous rock (see Fig. 2) igneous rock (Obsidian - volcanic glass) Is it shiny? Is it easily scratched? Is it easily scratched? sedimentary rock (coal) metamorphic rock (see Fig. 3) sedimentary rock (see Fig. 4) igneous rock (see Fig. 2)

9 Rock Identification Chart - Fig. 2 igneous Rocks Can you see crystals in the rock? Are the crystals all the same size? Is the rock glassy? Are the crystals >1 cm? Porphyry Obsidian Does the rock have holes in it? Pegmatite Mostly light minerals. Does the rock contain >10% Quartz? Granite Is the rock made of mostly light coloured minerals such as quartz and feldspars, mostly dark coloured such as hornblende, biotite, and pyroxene, or a mixture of both light and dark coloured minerals? Syenite Mixture of light and dark minerals. Diorite Mostly dark minerals. Gabbro Vesicular Basalt - Pumice Amygdaloidal Basalt Does the rock contain irregularly shaped, mineral-filled pockets? Light. Rhyolite Is the rock lightly, moderately or darkly coloured? Moderate. Andesite Dark. Basalt

10 Rock Identification Chart - Fig. 3 Metamorphic Rocks Can you see crystals in the rock (coarse grained)? Are the minerals lined up like sheets of paper in a stack? Does the rock have a metallic sound when it is hit? Does the rock have separate bands of light minerals, such as quartz and feldspars, and dark minerals, such as biotite and hornblende? Does the rock have separate bands of light minerals, such as quartz and feldspars, and dark minerals, such as biotite and hornblende? Slate Phyllite Is the rock shiny? Slate Gneiss Schist Gneiss

11 Rock Identification Chart - Fig. 4 sedimentary Rocks Are there fossils in the rock? Does the rock fizz with acid? (Perform a carbonate test.) Are there visible grains in the rock? Fossiliferous Limestone Fossiliferous Sandstone Can you see grains in the rock? Flat pieces. Fossiliferous Shale Has the rock broken into flat pieces or chunks? Chunks. Fossiliferous Mudstone Are the grains rounded? Conglomerate Are the grains > 2mm? Breccia Sandstone Flat pieces. Shale Has the rock broken into flat pieces or chunks? Coal Clay-Iron Concretion Chunks. Is the rock shiny? Is the rock heavy? Does the rock fizz with acid? (Perform a carbonate test.) Limestone Mudstone