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A Typical Topography
Much of the geology of an area is concerned with the activities that affect the earth’s surface.
Wind, running water, groundwater, ice volcanism, and earth movements continuously act on
the surface if the state and produce many surface features.
By studying the landforms in an area, it is possible to determine what processes are at work
now and what processes were at work in the past. The basic tool for this task is the
topographic map. A topographic map represents a view of the landscape as seen from above.
The map is a scale drawing that shows various details of landforms – size, shape, and relative
distances among them. Figure 1 shows examples of typical landforms. Figure 2 is the
corresponding topographic map.
The full page topographic map in figure 3 is of a small town of Damon, Texas. Highway 36
runs northwest to southwest on the east side of town. The surrounding countryside is flat and
devoid of contrasting landforms. Damon is built on a mound that consists of about 1200
hectares. Northwest of the mound, beginning almost at the base lays a wooded area and a
limestone quarry.
The mound itself is caused by a massive dome of salt that is slowly working its way from deep
beneath Damon to the surface of the earth. The contour lines, or curved lines on the map,
connect points of equal elevation. High areas are represented by a series of roughly circular
contour lines. As the elevation increases, the circles become smaller. Closely spaced lines
represent steep slopes. Lines further apart represent gentle slopes. The change in elevation
between lines is 1.5 meters (5 feet). Use the topographic map to answer the following
questions about the surface features of Damon Mound. Remember, you will need to convert to
metric units to answer the questions.
1. What is the lowest elevation shown on the map?
elevation on the mound?
What is the highest
Based on these values, how high is Damon
Mound?
2. A cemetery marked with a cross, is located on top of the mound. What is its elevation?
3. Oil is produced at the mound. In what direction from the mound is the oil field located?
4. Does Damon Mound appear to cross Highway 36?
5. Compare the closeness of the contour lines on the west side of the mound with those
on the east side of the mound. Which side shows the steepest slope?
6. Study the top of the mound. How would you describe its appearance?
7. Houses appear on the map as small black squares. Is housing found throughout the
entire area of the mound?
8. Oil wells appear as small white circles. Where are most of the wells at Damon Mound
found?
9. What is the north-south distance (A, A’) of Damon Mound?
The west-east distance (B, B’)?
It is often desirable to construct a profile, or cross section, of landforms. A profile gives a more
natural view of an area and shows hills and valleys from the side. You will now construct a
profile of Damon Mound from point A to A’. Use the following directions and Figure 4 to make
your profile.
1. Place a strip of paper along line A, A’ as shown in figure 4a. On the paper, mark the
exact spot where each contour line crosses the strip. Label the elevation of each line.
2. Place the strip of paper along the bottom of the chart as shown in Figure 4b. Transfer
each mark on the paper strip to the proper spot on Figure 5.
3. Connect the points with a smooth line.