Name: _____________________________________

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Topography and Contouring

The goal of this laboratory exercise is to teach the principles of a topographic map and how this relates to three-dimensional topography in real life. It is assumed that you have read Laboratory 7 from the lab manual (pages 100-121) At the end of this lab you will be able to:

• Read a contour map • Contour data • Draw a topographic profile through a contour map

During the first part of this exercise you will be shown a series of three-dimensional visualizations using the Department of Geological Science GeoWall. You will also complete a series of exercises using the computer on your desk. Demonstration 1: Mariana Backarc Basin, western Pacific Bathymetry, topography, and seismicity in the Mariana region.

• Dark blue: deepest seafloor. This includes the Challenger deep, which at 10,915 m is the deepest point on the surface of the Earth. The crescent shaped deep blue region is the Mariana Trench. This is where the Pacific Plate is sinking beneath the Philippine Sea Plate.

• Red: shallowest regions. The chain of red peaks is the Mariana Islands, including Guam in the south. Many of these are active volcanoes, including Anatahan which erupted in 2002.

• The long dimension of the image is about 1500 km. • The bathymetry and topography portion of the map is displayed with a vertical

exaggeration of five. • Green dots: Earthquake foci plotted in their true depth location (no vertical

exaggeration). The bulk of these earthquakes are along the top and bottom of the subducting Pacific Plate.

• Your TA will explore this data set and complete a short fly-through Demonstration 2: Augustine Volcano, Alaska Illuminated topography of Augustine Volcano above sea-level, introduction to contours.

• Brown: highest topography. • Blue: lowest topography (sea level). • Augustine volcano is a 1260 m tall composite cone volcano in the Cook Inlet of

Alaska. It last erupted in the January of 2006. • Contours are plotted every 100 m. • Your TA will explore this volcano and explain things such as contour lines and

vertical exaggeration.

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Demonstration 3: Alabama Topography and Geology

• Brown: highest topography. • Blue: lowest topography. • Highest point is 734 m. • The Appalachian Mountains trend NE-SW and dive below the coastal plain. • The image is highly vertically exaggerated (75X) – it looks like there are

mountains on the Gulf Coast. • Your TA will explore this image and overlay a geological map.

Demonstration 4: Mount Mazama - Topographic Profiles Introduction to the concept of topographic profiles: This exercise uses a three-dimensional image of Crater Lake, Oregon. The large depression in the image is a caldera that was formed by the catastrophic eruption of Mount Mazama almost 7000 years ago.

1. Start ModelPress Reader 4.4 by double-clicking on the desktop icon. 2. From the main menu select File – Open. Navigate to the Desktop and then GEO-

101-Summer – Topo Maps – ModelPress. Double-click on the file crater_lake_water.wrl.

3. Follow along with the TA’s demonstration of a topographic profile and then repeat the exercise on your own computer. To do this: • Rotate the image by clicking and dragging with the left-hand mouse button. • From the main menus select Tools - Cut/Cross-section. Select the Width

Cutting Plane Orientation and use the slider to adjust where the image is cut. • When you have selected your preferred cross-section click on the Cross

Section check-box, and then on Finalize. Pan and tilt to show the profile. • Repeat the process, clicking on Clear Cut/Cross Section before choosing

another slice. Demonstration/Exercise 5: Contour Maps and Topographic Profiles Your TA will open a three-dimensional image of Crater Lake, Oregon and display it using the GeoWall. A number of features will be pointed out.

1. Sketch the contour lines for the hill on the screen. Label the contours assuming a contour interval of 10 m and a total hill height of 605 m.

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2. Where are the contours closest together? ___________________________________________________________ Why? ___________________________________________________________

3. Draw a topographic profile through the center of this hill. Include a y-axis that is labeled in meters

4. Sketch the contour lines for the large caldera (a depression created by a massive volcanic eruption) on the screen. Label the contours assuming that the contour interval is 10 m and that the elevation of the water in the lake is 100 m.

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5. Draw a topographic profile through the center of the caldera. Include a y-axis that is labeled in meters

Your TA will display a three-dimensional map of a valley and ridge system with contour lines.

6. Sketch this map and show the likely location of a major stream.

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Your TA will display a three-dimensional map of a cliff with contour lines.

7. Sketch the contours as they approach the cliff and reach the top.

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Independent Exercises:

On your computer’s desktop, double click the GEO101 Summer. Within this you will find another folder named Topo Map – double click again to open this folder. You will find quicktime movies that will be used as a visual aid for the exercises below. Movies and images are courtesy of Stephen A. Reynolds.

1. Describe the landscape corresponding to the contour map below. Double click on the QuickTime move topots_hill_qt for additional visuals. When QuickTime loads, click the play button and watch the image.

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2. Describe the landscape corresponding to the contour map below. Double click on

the QuickTime movie topots_cliff_qt for additional visuals..

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3. Draw the profile for line E-F. Label the vertical scale.

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4. Draw the profile for line C-D. Label the vertical scale.

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5. Draw the profile for line I-J. Label the vertical scale.

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6. Draw the profile for line G-H. Label vertical scale.

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7. Contour the following images with a contour interval of 10 m. What is the

maximum elevation of each map?

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8. What is the contour interval of the map below?

__________________________________________________________________

9. What is the gradient between X and Y (in meters per km)?

__________________________________________________________

10. What is the maximum elevation?

__________________________________________________________

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11. Using the Tuscaloosa Quadrangle, locate the following places and identify their elevation:

a. Smith Hall _____________ b. Denny Chimes _____________ c. Water Treatment Plant _____________ d. Stillman Heights School _____________