GEOL MAP B Contour Assignment
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GEOL 1580L: Natural Disasters Lab
Contour Maps
Name ____________________________ Topographic maps depict the 3-dimensional shape of the Earth’s surface on a 2- dimensional piece of paper. There are different styles of topographic maps. Probably the most useful one for geologists is the contour map. The purpose of this lab is to introduce students to contour maps and their principles. Understanding contour maps is important to this course because we will be using these types of maps for several of the future labs. Contours A contour is a line that connects points of equal elevation. Because contours are lines of equal elevation, they are horizontal. An example of a real horizontal line on the Earth’s surface is a lake shoreline. Because water forms a level surface, all of the points at the shoreline have the same elevation. With regard to a contour map, one can conceptualize contours of the map as representing shorelines of lake surfaces with the lake at different levels. Map A attached to this handout is an example of a contour map. Contour Principles 1. The elevation of the contours used on a map will be at elevations useful for the scale
and purposes of the map. 2. The elevation difference between contour lines on a given map will be uniform and is
referred to as the contour interval. In addition to a uniform interval, the elevations will be drawn at convenient values, such as every 100 feet or every 10 meters.
3. Contour lines will not intersect one another (unless there is a vertical cliff). 4. On a contour map, areas where contours are closely spaced represent steeper slopes
than areas where the contours are further spaced. 5. The contours for a hill or basin will form a bulls-eye pattern (although it is often
irregularly shaped). If the feature with the bulls-eye pattern is a basin, tick marks will be placed on the contours forming the basin.
6. Where contours cross stream channels they will have a “V” pattern with the apex of
the “V” pointing up-stream. If the stream is in a large valley, the “V”s will be large.
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Topographic Profiles A useful property of a contour map is that one can use the map to construct a topographic profile. A topographic profile shows a side view of the shape of the Earth’s surface along a chosen line. For geologists, a profile view is useful because the geologic structure below the Earth’s surface can be shown. . How to Construct a Topographic Profile Step 1: Put a piece of paper along the line of profile drawn on the map. Step 2: On the paper, put a tick mark at each end of the profile line and put
corresponding labels for each end on the paper. Step 3: For each location where a contour intersects the line of profile put a tick mark
on the piece of paper. On the paper below each tick mark label the elevation of the contour. Also put tick marks and labels where streams intersect the line of profile.
Step 4: Move the piece of paper with the tick marks to the profile graph paper. Align
the tick marks at the two ends of the profile line with the profile graph. Step 5: Graph each contour elevation at the appropriate elevation on the profile graph.
The graphed elevation should be lightly plotted as a point on the graph. Step 6: Remove the paper with the tick marks and finish the profile by drawing a line
that connects the graphed points. The line should be smoothly curved. Note: Topographic profiles are typically drawn without vertical exaggeration, but
sometimes employing vertical exaggeration is useful. A profile without vertical exaggeration has a vertical scale that is the same as the horizontal scale. Vertical exaggeration is drawn by using a vertical scale that is larger than the horizontal scale.
Lab Assignment 1. a. Map A is a contour map with the elevation at a point shown. The contour interval
is 100 feet. In the open space shown along the contours, label the elevation of the contour. Be sure to look carefully over the map to find all of the open spaces.
Note that there is “bulls-eye” pattern on the map where contours have tick marks. Realize that this represents a basin.
b. Draw the topographic profile for the line A – A’ shown on the map. The profile graph paper is provided on the page after the map. Draw the profile first using the
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upper graph and then the lower. The upper graph shows the profile without vertical exaggeration and the lower graph shows the profile with 2x vertical exaggeration.
2. a. Map B is a map of an island with the elevation of different points given. Using
these data points, draw the contours for the island using a contour interval of 20 feet. Be sure to label each contour line with its elevation.
b. Draw the topographic profile for lines A-A’ and B-B’ using the profile graphs on
the page after the map. 3 a. Draw contours on Map C at a contour interval of 10 feet.
b. Draw the profile for line A-A’ on the profile graph below the map.
A
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GEOL 158: Natural Disasters, Contour Maps
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Map B
GEOL 158: Natural Disasters, Contour Maps
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Sea Level
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Sea Level
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GEOL 1580: Natural Disasters, Contour Maps
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GEOL 1580: Natural Disasters, Contour Maps
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- 01 Contour Maps
- 02 Map A Contour
- 03 Map A Profile
- 04 Map B island contour map
- 05 Map B Island Topo Profile
- 06 Map C copy