Laboratory Manual for Physical Geology. Topographic Maps

Transcription

1 Laboratory Manual for Physical Geology Topographic Maps Overview... 2 Materials Needed... 2 Topographic Maps... 2 Map Symbols... 2 Map Scales... 3 Types of Scales... 3 Map Use... 5 Small Scale V. Large Scale... 6 Latitude and Longitude... 8 Contours Topographic Map Symbols Rules for Contour Lines Contour Intervals Public Land Survey System Background Meridians and Base Lines Township, Tier, and Range Sections and Legal Descriptions Markers Sources Exercises Mapquest Contouring Elevation Data, Part Contouring Elevation Data, Part Topographic Maps Page 1 of 23

2 OVERVIEW Whether on paper or a computer screen, a map is the best tool available to catalog and view the arrangement of features on the Earth's surface. Maps of various kinds road maps, political maps, land use maps, maps of the world serve many purposes. One of the most widely used of all maps is the topographic map. The U.S. Geological Survey (USGS) produced its first topographic map in 1879, the same year the organization was established. Today, more than 130 years and millions of map copies later, topographic mapping is still a central activity for the USGS. The topographic map remains an indispensable tool for government, science, industry, and leisure. The resource text that accompanies this lesson is 100 Topographic Maps. The Introduction in 100 Topographic Maps explains many details that will help you use the book efficiently. MATERIALS NEEDED 12 string or thread Ruler Magnifying glass 100 Topographic Maps Printouts or pdfs of the Mapquest and Contouring Elevation Data Questions Printouts of the Contouring Elevation Data map points TOPOGRAPHIC MAPS A topographic map is a two-dimensional map that uses contour lines to depict a three-dimensional land surface. Contours are imaginary lines that join points of equal elevation on the surface of the land above or below a reference surface, such as mean sea level. Contours make it possible to measure the height of mountains, depths of the ocean bottom, and steepness of slopes. MAP SYMBOLS Topographic maps include symbols, lines, points, and shaded areas that represent both natural and manmade features. Natural features include mountains, valleys, plains, lakes, rivers, and vegetation. Map symbols also identify the principal works of man, such as roads, boundaries, transmission lines, and major buildings. Vegetation, water, and densely built-up areas are among the most obvious features on a topographic map. Individual houses may be shown as small black squares. For larger buildings, the actual shapes are mapped. In highly Topographic Maps Page 2 of 23

3 developed areas, most individual buildings are omitted and an area tint is shown. On some maps, post offices, churches, city halls, and other landmark buildings are shown within the tinted area. (See Ft. Collins, p. 7) Many topographic features are shown by lines or combinations of lines that are straight, curved, solid, dashed, or dotted. Various symbols depict features such as buildings, campgrounds, springs, water tanks, mines, survey control points, and wells. Colors of lines usually indicate similar classes of information. Names of places and features, for example, are shown in colors that correspond to the type of feature, such as blue for water. Colors of symbols shown in 100 Topographic Maps differ slightly from USGS symbols. Note that vegetation is not shown in 100 Topographic Maps because the book is printed in a limited number of colors that does not include green. Brown Blue Heavy Black Black topographic contours hydrographic features lakes, streams, irrigation ditches, etc. land grids and important roads other roads and trails, railroads, boundaries, and other cultural features Table 1-1 Commonly used colors in 100 Topographic Maps. For a complete list of Map Symbols and colors, refer to, p. 10 of 100 Topographic Maps. MAP SCALES TYPES OF SCALES All maps represent a portion of Earth's surface. Their smaller-than-life size is a convenient method of illustrating the world. If maps are to be at all useful, the relationship between the size of the graphic and the actual size of the same region of Earth depicted in the graphic must be known. Simply defined, scale is the correlation between distance on the map and distance on the Earth s surface. Map scales most often take one of three forms: representative fraction, bar (graphic) scale, and verbal scale. Type of Scale Representative Fraction (R.F.) Example 1:24,000 or 1/24,000 Records the number of units on Earth s surface represented by one of the same units on a map. May be written as either a ratio or a fraction to show how much the real world has been reduced to fit on a map. Topographic Maps Page 3 of 23

4 Not tied to a specific measurement system, so scales work in metric as well as U.S.A. and/or other systems. Example: For an R.F. scale of 1:24,000, one inch on the map represents 24,000 inches on the ground. Since the R.F. scale has no assigned units, one centimeter on the map also represents 24,000 centimeters on the ground. Unit (inches, cm, etc.) chosen for one side of the fraction or ratio must be the same unit for the other side of the fraction or ratio. Note: The number 1 is always in the numerator of the fraction (left side of the colon in the ratio). USGS topographic maps display R.F. at the bottom of the map under the map name. The text, 100 Topographic Maps, displays scale information under the map on the right side of each page. Bar Scale Figure 1-1 Bar Scale Typically, bars are drawn with numbers marked along the length of the bar and the units (miles, feet, km, etc.) indicated. Allows distance to be measured on the map and directly compared to the bar scale, so math calculations are not needed. Sometimes referred to as graphic scales. USGS topographic maps display three bar scales at the bottom of each map in units of miles, feet, and kilometers. The text 100 Topographic Maps displays bar scale information under each map near the bottom of each page; only mile and kilometer scales are included. Verbal Scales One inch on the map represents about a mile on the ground Informal; used most commonly in conversation and on popular atlases and maps. Estimates the proportion between distance on a map and distance on the ground using either R. F. or bar scales. Converts large numbers of units on the right side of an R.F. expression to more manageable units. Simplifies bar scales by converting units and restating information, for example, one centimeter on the map represents approximately 600 meters on the ground. Can also be derived by placing a ruler on a bar scale and stating what is observed. Topographic Maps Page 4 of 23

5 Geologists most often use R.F. scales when comparing maps of differing scales. For instance, if the scale were 1:63,360, then 1 inch on the map would represent 63,360 inches, or 1 mile on the ground (63,360 inches divided by 12 inches equals 5,280 feet, or 1 mile). The first number of an R.F. scale (map distance) is always 1. The second number (ground distance) is different for each scale. The larger the second number, the smaller the scale of the map. "The larger the number, the smaller the scale" sounds confusing, but it is actually easy to understand. A map of an area 100 miles long by 100 miles wide, drawn at a scale of 1:63,360 would be more than 8 feet square. To make the map a more convenient size, either the scale used or the area covered must be reduced. If the scale is reduced to 1:316,800, then 1 inch on the map represents 5 miles on the ground. An area 100 miles square can then be mapped on a sheet less than 2 feet square (100 miles at 5 miles to the inch equals 20 inches, or 1.66 feet). On the other hand, if the original 1:63,360 scale is used, but the mapped area is reduced from 100 to 20 miles square, the resulting map will also be less than 2 feet square. Small scale maps are easier to handle, but are they more useful? In the smallerscale map (1:316,800), there is less room; therefore, everything must be drawn smaller. Some small streams, roads, and landmarks must be left out altogether. On the other hand, the larger-scale map (1:63,360) permits more detail but covers much less area. When large scales are needed over large areas, multiple maps are often used instead of one large, unwieldy one. Question If you copied a map and reduced it by 2%, which scales would still be useful and/or accurate? MAP USE Many areas have been mapped at different scales. The most important consideration in choosing a map is its intended use. For instance, a civil engineer may need a very detailed map to locate specific sewers, power and water lines, and streets. A commonly used scale for this purpose is 1:600 (1 inch on the map represents 600 inches, or 50 feet, on the ground). This scale is so large that many features such as buildings, roads, and railroad tracks can be drawn to scale instead of just being represented by symbols. The USGS publishes maps at various scales. The scale used for most U.S. topographic mapping is 1:24,000. USGS maps at this scale cover an area measuring 7.5 minutes of latitude and 7.5 minutes of longitude and are commonly called 7.5-minute quadrangle maps (see p. 8 for more information on Topographic Maps Page 5 of 23

6 latitude and longitude). Map coverage for most of the United States has been completed at this scale, except for Puerto Rico which is mapped at 1:20,000 and 1:30,000. A few states have been mapped at 1:25,000, while most of Alaska has been mapped at 1:63,360, with some populated areas also mapped at 1:24,000 and 1:25,000. Figure 1-2 Scale for USGS quadrangle maps. Maps at 1:24,000 scale are fairly large and provide detailed information about the features of an area, including the locations of important buildings and most campgrounds, ski lifts, and water mills. Footbridges, drawbridges, fence lines, and private roads are also shown at this scale. Usually these features are omitted from maps in the scale range of 1:50,000 up to 1:100,000. These maps cover more area while retaining a reasonable level of detail. Maps at these scales are most often produced using the 30- by 60-minute quadrangle formats. Small-scale maps (1:250,000 and smaller) show large areas on single map sheets, but details are limited to major features such as boundaries, parks, airports, and major roads. SMALL SCALE V. LARGE SCALE Large Scale Medium Scale Small Scale 1/24,000 1/100,000 1/250,000 Figure 1-3 Comparing map scales of Crater Lake. Topographic Maps Page 6 of 23

7 Comparing a set of three maps for Crater Lake illustrates how much of the mountain is included in maps with different scales. Choose a common feature to compare between maps, such as Wizard Island. Also, notice the details preserved from one scale to another. The small scale map (1:250,000) shows most of the lake, whereas the large scale map (1:24,000) shows mostly the island in the lake. Questions 1. Name a feature that can be seen in the 1/24,000 but not in the 1/100,000 map. 2. Name a feature that can be seen in both the 1/24,000 and 1/100,000 maps but not in the 1/250, How might each map be useful to someone planning a hiking trip at Crater Lake? Large Scale 1/24,000 Medium Scale 1/100,000 Topographic Maps Page 7 of 23

8 Small Scale 1/250,000 Figure 1-4 Comparing map scales of Ft. Collins. The set of three maps for Fort Collins, CO, allows the comparison of man-made features such as roads and buildings on the same three scales. Notice the tinted area shows the municipality and not the individually plotted buildings. Select one feature on the first map to compare to the other maps in order to see the effect of different scales on the map view. Questions 1. Which scale shows the least area? 2. Which scale shows the most area? LATITUDE AND LONGITUDE The most common way to locate points on the surface of the Earth is by standard geographic coordinates called latitude and longitude. The values of these coordinates are measured in degrees, minutes, and seconds and represent angular distances calculated from the center of the Earth. Figure 1-5 Equator. Imagine the Earth as a sphere, spinning around an axis. The ends of the axis are the North and South Poles. The Equator is a line around the earth, an equal distance from both poles. The Equator is also the latitude line given the value of 0 degree, making it the starting point for measuring latitude. Latitude values indicate the angular distance between the Equator and points north or south of it on the surface of the Earth. Topographic Maps Page 8 of 23

9 A line connecting all points with the same latitude value is called a line of latitude. This term usually refers to lines that represent values in whole degrees. Since all lines of latitude are parallel to and equally spaced from the Equator, they are sometimes referred to as parallels. Figure 1-6 Lines of latitude Figure 1-7 Prime Meridian. There are 90 degrees of latitude going north from the Equator, and the North Pole is at 90 degrees N. There are 90 degrees to the south of the Equator, and the South Pole is at 90 degrees S. When the directional designators are omitted, northern latitudes are given positive values and southern latitudes are given negative values: + 90 degrees or 90 degrees. Lines of longitude, called meridians, run perpendicular to lines of latitude. All lines of longitude pass through both poles. Each longitude line is part of a great circle. A great circle of a sphere is a circle that runs along the surface of that sphere so as to cut it into two equal halves. The great circle therefore has both the same circumference and same center as the sphere. It is the largest circle that can be drawn on a given sphere. Figure 1-8 Great Circle Unlike latitude, there is no obvious 0 degree point for longitude. By international agreement, the meridian line through Greenwich, England, is currently given the value of 0 degree of longitude. This meridian is referred to as the Prime Meridian. Figure 1-9 Longitude. Longitude values indicate the angular distance between the Prime Meridian and points east or west of it on the Earth s surface. The Earth is divided equally into 360 degrees of longitude. There are 180 degrees of longitude to the east of the Prime Meridian; when the directional designator is omitted these longitudes are given positive values (+ 90 degrees). There are also 180 degrees of longitude to the west of the Prime Meridian; when the directional designator is omitted these longitudes are given negative values ( 90 degrees). Topographic Maps Page 9 of 23

10 The 180-degree longitude line is located opposite the Prime Meridian on the globe. This line is the same going either east or west. An imaginary line running roughly along the 180-degree longitude is the International Date Line (IDL). With diversions to pass around some territories and island groups, it mostly corresponds to the time zone boundary separating +12 and 12 hours Greenwich Mean Time (GMT). Crossing the IDL while traveling east results in a day, or 24 hours, being subtracted; crossing the IDL while traveling west results in a day being added. Degrees of latitude and longitude can be further subdivided into minutes and seconds: there are 60 minutes (') per degree and 60 seconds (") per minute. For example, a coordinate might be written 65 32' 15". Degrees can also be expressed as decimals: degrees and decimal minutes: ', or even degrees, minutes, and decimal seconds: 65 32' ". All these notations allow us to locate places on the Earth quite precisely to within inches. A degree of latitude is approximately 69 miles and a minute of latitude is approximately 1.15 miles. A second of latitude is approximately 0.02 miles, or just over 100 feet. A degree of longitude varies in size to adjust for drawing a square grid on a spherical surface. At the equator, it is approximately 69 miles, the same size as a degree of latitude. The size gradually decreases to zero as the meridians converge at the poles. At 45 degrees latitude, a degree of longitude is approximately 49 miles. Because a degree of longitude varies in size, minutes and seconds of longitude also vary, decreasing in size toward the poles. CONTOURS Topographic contours depict the general shape of the terrain. They are shown on maps by brown lines of different widths. Index contour lines are wider (bolder) and usually labeled with elevation values (height above sea level). The narrower intermediate and supplementary contours between index contours help show more details of the land surface shape. Topographic Map Symbols Index Contour Interval These thicker contour lines have a number written on them that indicates the elevation (height above sea level) of all points along the contour line. The unit of measurement (feet, meters) depends on the map. Intermediate Contour Interval. These lines appear between index contour lines (see above) and have no elevation numbers. Supplementary Contour Interval. These dotted lines are placed in Topographic Maps Page 10 of 23

11 areas where elevation change is minimal. If there is a lot of space between index and intermediate contours (as happens where the land is relatively flat), these lines are added to provide additional elevation measurements, even if they are few and far between. Depression. A depression is a decline in elevation inside a rise in elevation, for example, a crater whose sides rise but whose center is lower. Depressions are marked by hachured lines. Cut; Fill. Cuts and fills occur where a roadway has been blasted through land, drastically lowering (cut) or raising (fill) the elevation in a distinct and small area. Table 1-2 USGS topographic contour symbols. The elevation difference between adjacent contour lines, called the contour interval (C.I.), is selected for each map to best show the general shape of the terrain. A map of a relatively flat area may have a contour interval of 10 feet or less. Maps in mountainous areas may have contour intervals of 100 feet or more. The contour interval is printed in the margin of each USGS map. In the resource text, 100 Topographic Maps, the contour interval is listed below the scale in the bottom right corner of the map margin. To read contour lines, one must determine the uphill and downhill directions. Clues are everywhere. For example, water flows downhill so locating a stream usually helps find the lowest elevations on a map. Carefully inspecting the numerical values of index contour lines can also help. Relief, the difference between the highest and lowest elevations on a topographic map, indicates the ruggedness of the terrain. In mountainous areas, it is not uncommon for the relief to be thousands of feet. Relief values in the Mississippi flood plain, however, would be, at most, hundreds of feet. Relief is calculated by reading the map and subtracting the lowest elevation from the highest elevation. Note that the highest and lowest elevation values are only rarely recorded on the map as numerical values. The customary procedure is to interpolate the highest (might be tops of hills or mountain) and lowest values (generally streams at the downhill edge of the map). RULES FOR CONTOUR LINES 1. Contour lines connect points of equal elevation. Every point on a given contour line is the exact same height above sea level. 2. Contour lines do not intersect, branch, split or cross. The only exception to this rule is when overhanging cliffs are present. In this extremely unusual circumstance, the hidden contours are dashed. Topographic Maps Page 11 of 23

12 3. Contour lines always come to closure with themselves, forming irregular circles and ellipses. This closure may not be apparent, however, within the map area of a single topographic quadrangle; consequently, many contour lines appear to end abruptly at a map s edge. 4. The difference between any two adjacent contour lines of different elevation on a topographic map is called the contour interval (C.I.). Usually every fourth or fifth contour line is a heavier line and is labeled with the elevation. These heavier contour lines are known as index contours. 5. The elevation of any point which lies between two contour lines must be estimated on the basis of its relative distances from the two nearest contour lines. 6. Contour lines always separate points of higher elevation (uphill) from points of lower elevation (downhill). From any reference point, you must determine which direction is higher and which is lower by inspecting the map for streams (water always flows downhill), benchmarks, or nearby index contour lines. 7. The spacing between contour lines on a topographic map reflects the slope or gradient of the land. Mathematically, this is the change in elevation (vertical change) over a given distance (horizontal change). Perfectly level ground is not crossed by any contour lines. A uniform slope is represented by equally spaced contour lines. A gentle slope is represented by widely spaced contour lines. A steep slope is represented by closely spaced contour lines. A vertical cliff is represented by merged contour lines. 8. Every point enclosed by a solid contour line is topographically higher than the line itself. Thus, solid contour lines enclose topographic highs such as hills and mountain ridges. 9. Hachured lines (see Depression illustration on p. 10 of 100 Topographic Maps) are used to mark the contours of closed depressions which have no drainage outlets, such as ponds and sinkholes. Every point enclosed by a hachured contour line is topographically lower than the line itself. The outer hachured contour line around a topographic low has the same elevation as the closest solid contour line. 10. When contour lines cross streams or dry stream channels, each line that crosses forms a V with the point oriented upstream. 11. Topographic maps published by the USGS are contoured in feet or meters measured from sea level. CONTOUR INTERVALS Elevations of points which are not exactly on contour lines are determined by applying the contour interval (C.I.) and interpolating (making a reasonable estimate based on available map data) between the two nearest contour lines. Sometimes these are not labeled because they are intermediate contour lines. In Topographic Maps Page 12 of 23

13 this case, it is necessary to locate the nearest index contours, the heavier lines, and an associated number marked on every fourth or fifth contour line. 1. Determine the C.I. by choosing a location on the map where two successive index contours and the intermediate contour lines between them are easily read. 2. Starting at one index contour, usually the lower numerical value, count the number of contour lines to the next index contour line. (Do not include the initial index contour in the count.) This tells you how many divisions to the higher index contour line. 3. Subtract the smaller index contour value from the larger index contour value which you read on the map. 4. Divide the index contour interval (larger number) by the number of divisions you counted (smaller number) to find the map Contour Interval (C.I.) 5. Example: The difference in elevation between two index contour lines is 200 feet and there are 5 divisions (4 intermediate contour lines plus the higher index contour line). Suppose you are standing with your feet on the lowerelevation index contour line. An easy scenario to imagine (and do the math for) would be at sea level. So, you are standing with your heels in the ocean and your toes on the beach. You are looking toward a nearby hill. If you can see a flag planted uphill on the next index contour line, the base of the flag is 200 feet higher than your feet. It does NOT mean the flag is 200 feet away (UNLESS it is directly overhead, which would mean the flag is at the top of a sheer cliff). To determine the contour interval, divide the 200 ft. elevation into 5 equal segments (the 5 divisions referred to above) or 200 ft. 5 = 40 ft. You would have to climb 40 feet higher to arrive at the level of the first intermediate contour line, making the elevation of that line 40 ft. (Remember that the elevation of sea level is, by definition, 0 feet). The elevation of the next intermediate contour line would be 80 ft. (40 ft.+ 40 ft. = 80 ft.), and so on. PUBLIC LAND SURVEY SYSTEM BACKGROUND The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. All lands in the public domain are subject to subdivision by this rectangular system of surveys, which is regulated by the U.S. Department of the Interior, Bureau of Land Management (BLM). Originally proposed by Thomas Jefferson, the PLSS began shortly after the Revolutionary War (1785), when the Federal government became responsible for large areas west of the thirteen original colonies. The government wished to distribute land to Revolutionary War soldiers to reward them for their service, and Topographic Maps Page 13 of 23

14 also to sell land as a way of raising money for the nation. Before this could happen, the land needed to be surveyed. Figure 1-10 Red areas are included in the Public Land Survey System. The PLSS encompasses major portions of the land area of 30 southern and western States. Since the original PLSS surveys were completed, much of the land that was originally part of the public domain has been transferred to private ownership and in some areas the PLSS has been extended, following similar rules of division, into nonpublic domain areas. MERIDIANS AND BASE LINES Figure 1-11 Meridians and Base Lines The reference meridian in this survey is named Willamette Meridian. The PLSS actually consists of a series of separate surveys. Most PLSS surveys begin at an initial point with townships surveyed north, south, east, and west from that point. The north-south line that runs through the initial point is a true meridian and is called a Principal Meridian. The names of the 37 Principal Meridians are used to distinguish the various surveys, e.g., the Willamette Meridian Survey. The east-west line that runs through the initial point is called a base line. This line is perpendicular to the Principal Meridian or reference meridian. TOWNSHIP, TIER, AND RANGE The PLSS typically divides land into 6-mile-square townships. Each township is identified with a township or tier (row) and range (column) designation. Tier designations indicate the location north or south of the base line. Range designations indicate the location east or west of the Principal Meridian. For example, a township identified as Township 7 North, Range 2 West means it is in the 7th tier (row) of townships north of a base line, and in the 2nd column range of townships west of a baseline. Topographic Maps Page 14 of 23

15 In Figure 1-12, all tier numbers for Washington townships are marked north because the baseline is located just south of the state boundary (dotted line) between Oregon and Washington. Therefore, in Washington state, no tier numbers have an address that includes south. SECTIONS AND LEGAL DESCRIPTIONS Townships (6 square miles) are subdivided into 36 one-mile-square sections (640 acres in each section). Sections can be further subdivided into aliquot parts, which are quarter sections (160 acres), quarter-quarter sections (40 acres), or irregular government lots. Figure 1-12 Township divisions. A legal land description of a section includes the State, Principal Meridian name, Township and Range designations with directions, and the section number. Sections are subdivided repeatedly in order to get to a scale that is useful in recording the location of a plot of land. In common usage, the smallest subdivision is listed first in the description. For example, a 10-acre plot in Washington state could be described as: SW¼, SE¼, NW¼, Section 14, T2S, R3W, Willamette Meridian Topographic Maps Page 15 of 23

16 Looking at Figure 1-14, this description indicates the NW¼ of Section 14 is subdivided into quarters; this quarter is further subdivided into quarters, and the 10 acre plot of interest is the SW quarter of this second subdivision. Other quarters are further subdivided into smaller plots. Figure 1-13 Section subdivisions. Topographic Maps Page 16 of 23

17 MARKERS Over the past two centuries, almost 1.5 billion acres have been surveyed into townships and sections. The original PLSS surveys were often marked by wooden stakes or posts, marked trees, pits, piles of rock, or other lesspermanent markers. Today, permanent monuments are usually inscribed tablets set on iron rods or in concrete. Normally, a permanent monument, or marker, is placed at each section corner. Monuments are also placed at quarter-section corners and at other important points, such as the corners of government lots. SOURCES Information for this lesson has been adapted from: United States Geological Survey, United States Geological Survey, United States Department of the Interior, EXERCISES Assignments: Lab Prep Part 1: Part 2: Your instructor may ask you to verify the contents of your lab kit by downloading and completing the Lab Kit Inventory form. Handson Labs will only resolve problems reported within two weeks of delivery. Mapquest: Print the page from the lab manual or download the fillable pdf form to record your answers to the questions. Contour elevation data map. Print the data points and draw the map. Answer the questions for Contouring Elevation Data using either the printout from the lab manual or the downloadable pdf. READ THIS BEFORE YOU BEGIN 1. View the lab videos. Introduction to Geology lab Introduction to topographic maps Drawing contour lines 2. Review the lab manual chapter for reading topographic maps. Topographic Maps Page 17 of 23

18 Part 1: Mapquest Question Student Name Section 100 Topographic Maps title and page number 1. What is the elevation of the dashed contour line located just west (<1/10 mile) of Reid Cemetery? 2. Why is the contour line just west of Reid Cemetery a dashed line instead of a solid line? 3. What is the elevation of the center of the larger depression located in the NW¼ of section 13? 4. What is the elevation of the High School located north of Crystal Lake? (Hint: Use the elevation of the contour line that runs through one of the buildings.) 5. What do the small squares marked diagonally half white/half black indicate? (For example, there are three in the SE¼ of Section 31.) Rover, TN 89 Rover, TN 89 Lake Wales, FL 31 Lake Wales, FL 31 Holy Cross, CO Which direction is the river flowing? St. Paul, AR If one walked from the river bank to the top of the nearest hill (both locations inside Section 33, T14N, R27W, and southeast of Patrick, Arkansas), how much higher than the river would the top of the hill be? 8. Suppose you hiked the trail from the house closest to Possum Creek School (T13N, R27W, Sec.8) to the summit of Stacy Mountain (T14N, R27W, Sec.19,). St. Paul, AR 15 St. Paul, AR 15 a) How far would you walk? b) Describe your hike in terms of uphill, downhill, and features you would see and cross. c) There are several switchbacks in the trail in the last mile of the trek. Why? Topographic Maps Page 18 of 23

19 Part 1: Mapquest Question Student Name Section 100 Topographic Maps title and page number 9. What is the PLS address (to the nearest quarter section) for Delaney Creek School? St. Paul, AR What is the relief for this entire map? Bray, CA The PLS location of East Jerome Butte is Sec.17, T45N, R1W. (Hint: Look in the northwest corner of your map.) What is the PLS location of Garner Butte (to the section)? Bray, CA The Lat/Long coordinates of Garner Butte are 41 37' 28"N, ' 8"W. Which of the following represents the coordinates for East Jerome Butte? a) 21 44' 32"N, ' 26"W b) 81 44' 17"N, ' 43"W c) 41 44' 32"S, ' 50"E d) 41 44' 32"N, ' 50"W e) 41 30' 31"N, ' 2"W 13. The Hanging Valley Mine is marked in Section 22 with a symbol. What does that symbol tell about the mine? Bray, CA 17 Mount Tom, CA Three symbols/sets of map conditions indicate a change in the slope gradient sign (uphill to downhill, or downhill to uphill). What are they? 15. By subtracting the lowest elevation of a depression from the outermost (or highest) elevation hachure contour of the same depression, one can only estimate the depth of the depression. Assuming the lowest elevation of the depression is recorded on the map, why can the resulting value not be the exact maximum depth of the depression? Topographic Maps Page 19 of 23

20 Part 2: Contouring Elevation Data Map Instructions: Use the elevation data points to create a contour map. Student Name Section YOU MUST USE PENCIL AND ERASER FOR THIS EXERCISE. Print Contouring Elevation Data Map. Printing multiple copies in is highly recommended. EVERYONE who contours maps makes erasures and adjustments. If a work copy becomes too messy, i.e., the erasures are not complete or the lines are not evenly spaced and smooth, redraw a clean copy rather than erase large areas before submitting a map to your instructor. Reminder: This is NOT a connect the dots exercise! Steps for contour mapping: 1. Write the numbers for contour intervals 210 and 220 in the margins where these lines exit the map. Continue to write numbers for each contour line you draw that goes off the map. 2. Choose two elevation points near the map edge that require a contour line elevation between them. For example, two points with elevations of 249 and 258 require a contour line at 250 since the contour interval is 10 ft. 3. Place a mark between the two known points (249 and 258) that represents an estimate of the true position. Is 250 halfway between the points or is it closer to one point than the other? 4. Observe all the nearest points. Compare every possible combination of two points until you find one combination that mathematically allows the line to pass between the two. Plot this point. 5. Using the marks from steps 3 and 4, draw the first segment of the line. 6. Repeat this comparison process to extend the contour line until it either closes on itself or exits the map. 7. Choose the next contour line 10 ft. up or down from the first line and repeat the process until all contour lines are drawn. (Be sure to draw contours for 230 and 240.) Topographic Maps Page 20 of 23

21 Part 2: Contouring Elevation Data Map Student Name Section Check and submit your work: Do all point elevations have values between the adjacent contour line elevation values? For example, when the contour interval is 10 ft., all elevation values between the 220 and 230 ft. contour lines fall between and include 221 and 229 feet. Does the map make sense? Pick an area and imagine you are crossing this terrain. To determine whether the stream V s are drawn correctly, imagine you are walking across the map. Are you going down into streams or up into streams? Is the uphill/downhill direction consistent? Have you violated any Rules for Contour Lines? Are all lines readable and labeled with the contour elevation value? Is each index contour heavier and darker? Have you answered the questions in Part 2? Submit Parts 1 and 2 as directed by your instructor. Topographic Maps Page 21 of 23

22 Part 2: Contouring Elevation Data Map Student Name Section Topographic Maps Page 22 of 23

23 Part 2: Contouring Elevation Data Questions Student Name Section To answer the following questions, locate two sets of points (225 ft., 267 ft.) and (257 ft., 291 ft.) on the west side of your contour map and imagine you are walking on the map. 1. As you cross from 225 ft. to 267 ft., are you walking uphill or downhill? 2. As you cross from 225 ft. to 267 ft., how many contour lines do you cross? 3. As you cross from 291 ft. to 257 ft., are you walking uphill or downhill? 4. As you cross from 291 ft. to 257 ft., how many contour lines do you cross? 5. Compare the steepness of slopes for #1 and #3. Which would be a steeper climb, #1 or #3? 6. Approximately how many feet of water would it take to fill the depression to the brim? 7. If you walked from the point (264 ft.) on the west side of the map to the point (271 ft.), how far would you walk? 8. Suppose you walked from the most northeast point with a given elevation (306 ft.) in a south-southwesterly direction to the point with elevation, 308 ft. Describe the changes in elevation as you cross this part of the map. Topographic Maps Page 23 of 23