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Regional Geology |
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Contour Maps (Cont'd) |  |
Activity #2. Using a sheet of notebook paper create a map using 10 foot contour lines to make two ridges separated by a ravine, make one ridge line 200 feet high and the other 100 feet high. Label your lines and make your lowest elevation sea level or zero feet elevation. Can you visualize the shape of the terrain you just created? To get a real look at your topography in 3D trace each contour line onto a separate piece of cardboard, you can use a pencil or pin to poke holes through the paper into the cardboard, then connect the dots and cut along the lines. Glue each layer into place one on top of the other. By doing so you create a 3-D model of your map. Save your map for an activity later in the lesson.
To
the right is an image of one of the flagpoles at the top of Mt. Davidson. Note the snow on the mountains in the background. The flagpole dates
to the late 1880's and was forged in a local Virginia City foundry.
Mt. Davidson is a topographic high and can be considered an elevation anomaly. The contour lines for any mountain make a series of rings that get smaller with increasing elevation (go back and look at the topographic map of Mt. Davidson). In nature, anomalies happen for a reason and they are often the result of some special situation or occurrence. The reason that this mountain is a topographic high is because it is made of harder rock than the surrounding area. In this case the rocks at the top of the mountain are intrusive rocks (an extinct or frozed magma chamber)surrounded by soft volcanic rocks. Different rates of erosion are due to the different rock types; a mountain forms where there is hard rock and a valley forms where there is soft broken rock. The Comstock Lode formed adjacent to Mt. Davidson where the underlying rock is soft and valley terrain and low land dominates. In addition, Mount Davidson and the Virginia Range are higher than the surrounding valleys as a result of faults that dropped the valleys relative to the mountains.
Activity #3. Shaded relief maps utilize topographic information and present it in a different form from that of the traditional contour map by the use of coloration and shading. Draw one of these maps at the site link listed below:
http://www.nationalatlas.gov/scripts/start.html
1. At this site zoom-in on the State of Nevada.
2. Click the following layers:
States
Shaded Relief
Streams and Water Bodies
Cities and Towns.
3. Click on "Download" and view the map.
4. Write a paragraph describing what you observe about the Nevada shaded relief map. Is Nevada flat, or does it have mountains; what happens to the rivers that flow in interior Nevada? Does Nevada have more mountains or more valleys? Is there a grain to the land? These are some of the questions to consider when writing your paragraph.
End Lesson
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Contour Maps (Cont'd) | |
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