Lab #7 - Topographic Maps Student Responses
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University of Cincinnati, Main Campus *
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001
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Geology
Date
Apr 3, 2024
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docx
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LAB #7 Student Responses – Topographic maps, streams, and drainage basins
(Adapted from Introductory Geology Laboratory Manual by B. Deline, R. Harris, and K. Tefend)
Understanding Topographic Maps
1. Label the elevation of the contours on the map below. Watch out for depressions!
2. Pretend you are a geologist with the US Geological Survey (USGS) and you are given an assignment to create a topographical map of a coastal area. You hike around with a GPS and you
record your position and elevation at various points in the study area. You create the map below by plotting all of your GPS locations and corresponding elevations. Complete the map by adding contour lines using a contour interval of 100 meters. Draw the lines so that they are continuous and either continue off of the map or form an enclosed circle. Map by Brad Deline
3. Below is a map of a glacial feature called a drumlin, which is a pile of sediment left behind by a retreating glacier.
Map by Brad Deline
a. What is the contour interval of this map?
b. What is the total relief of this map?
c. Which area along the red line A-C is steeper? Explain. d. What is the gradient from A-B and from B-C on the map? Show your work.
e. Drumlins can be used to determine the direction of
glacial movement as can be seen in the diagram on
the right. In the map above, what direction did the
glacier travel to form the drumlin? Assume North is
at the top of the map.
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www.northernwoodlands.org
4. Using the topographic map below, construct a topographic profile from A to A’. a. What is the horizontal scale in feet/inch?
b. What is the vertical scale in feet/inch?
c. What is the vertical exaggeration?
USGS Topographic Maps
5. For this section, examine one of the topographic maps provided. All of the information in this section is written somewhere on the map so it should be relatively easy to find.
a. What is the name of this quadrangle?
b. What part of which state is this quadrangle in?
c. What is the ratio scale of this map?
d. How many meters in real life does 1 cm on the map equal?
e. What is the magnetic declination in the area of this map?
f. What is the contour interval of this map?
g. Where, in general, is the highest elevation in this quadrangle? What is the elevation there?
h. Where, in general, is the lowest elevation in this quadrangle? What is the elevation there?
i. What is the total relief of the map?
Using topographic maps to measure streams and drainage basins
6. Examine the Mt. Airy study location on Map 1 and note the location of the Mt. Airy study area on Map 2
. On Map 1, you are looking at two very small streams in the Mt. Airy region of Cincinnati. These streams are not drawn on the map, but their basins are indicated by the numbers 1 and 2
. Map 2 shows the spatial relationship between the streams of Mt. Airy and the larger streams and rivers in the area.
a. What larger stream do these two basins contribute to? What river does that stream enter? Where does this water end up when it reaches sea level?
b. Draw an arrow on the map indicating which direction the west fork of Mill Creek is flowing.
c. Using the contour lines a guide, draw in the stream network in each of the two basins, directly on the map. Follow each stream to where it joins the west fork of Mill Creek.
d. On the map, draw the drainage divides for each of these basins, again using the contours as a guide.
e. On the graph paper provided on the page after Map 1, construct a longitudinal stream profile for the main stem (longest) streams in basin 1 and basin 2
.
You will need to plot elevation on the vertical axis vs. stream distance on the horizontal axis. The contour crossings are good places to measure these values.
Your profiles should both begin where the west fork of Mill Creek exits the map and extend upstream to the drainage divide in each basin.
You will need to measure distance along the stream with a ruler, and to convert map units to real-world distance. Be sure to label your axes, including units!
f. On the profile you just created:
What is the horizontal scale in meters/cm?
What is the vertical scale in meters/cm?
What is the vertical exaggeration?
g. What differences exist between the elevation profiles of two streams?
h. Are there any changes in slope (stream gradient) visible along the profiles? Describe.
i. What is the steepest stream gradient present in basin 1
? At what elevation range is it found (be sure to correspond the profile to the topographic map)?
j. What is the steepest stream gradient present in basin 2
? At what elevation range is it found?
k. Using the drainage basins you delineated, measure the drainage area contributing to each stream above where it joins the west fork of Mill Creek. You can use the grid on the map to estimate the area of the basin (note the grid spacing by comparison to the map scale).
Area of basin 1
:
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Area of basin 2
:
l. Assuming the average rainfall is the same for both drainage basins (which it should be, as they are very close together!), which one would you expect to have a larger stream in it?
m. What is an explanation for the difference in stream gradient between the two basins?
Map 1. Mt. Airy Forest
Map 1 Longitudinal Stream Profile
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Location of Map 1, Mt. Airy Forest
Map 2. A larger view of the region with the study area of Map 1 within the black box.