geolog

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A geographer's interest is focused largely on the surface of the Earth. Many kinds of tools are used in geographic studies, but probably the most important and most universal are maps. A previous lab introduced topographic maps, which are an important tool in physical geography. This lab will further discuss the fundamental elements of contour maps, as well as giving you experience in interpreting these maps to identify landform types in a variety of different environments.

Pre-lab reading topics: topographic profiles, slope, weathering, erosion (aeolian, glacial, and fluvial transportation), landforms (in arid, glacial and coastal environments)

WEATHERING AND EROSION

Landforms are individual relief features on the surface of the earth, formed by processes of weathering, erosion, and deposition. Interpreting the visual landscape requires a good understanding of the processes that formed it.

1. What is weathering? What are the two general types of weathering?

2. What is erosion? List three important processes by which eroded material may be transported.

ARID ENVIRONMENT

Desert environments frequently exhibit, over very short distances, complex landforms that develop from weathering or erosional processes. This exercise demonstrates how to recognize landscape elements formed by each these processes. The following questions are based on the Stovepipe Wells NE Quadrangle, CA.

3. What type of streams are prevalent in this area? Why is this so?

4. What map symbol is used to represent a sand dune?

5. Define a butte and describe how the Death Valley Buttes (NE) formed. Are the tops of these buttes erosional or depositional features?

6. What is the distance between the peaks of the 2 buttes in feet and km?

7. How were the dunes shown here formed, and what is the source of the sediment?

8. What natural landform feature do you find at the base of Grapevine Mountain in the NE portion of the quadrangle, and how was it formed? Is this an erosional feature or a depositional feature?

9. What is the elevation of the grave (36º 39′ 24″N and 117º 4′ 49″W), marked by a cross, that is about 0.75 km NE of Stovepipe Wells?

10. What is the distance in kilometers and miles from Red Top Peak in Death Valley Buttes to the highest peak in the Grapevine Mountains? Also, what direction (straight line) would one follow to travel from Red Top Peak to the highest peak in the Grapevine Mountains on the map?

11. Calculate the average gradient for the stream channel in the NW part of the quadrangle that extends from point A at the top of the quad downward to point B where the stream channel intersects the highway. Your answer must be unitless.

GLACIAL

This exercise gives practice at interpreting alpine glacial features. The following questions refer to the Holden Quadrangle, WA.

12. What is the bench mark elevation at the summit of Copper Peak?

13. What type of landform feature are Ice Lakes?

14. In the Northwest corner of the map, what would you call the feature that separates Isella Glacier (N) from Mary Green Glacier to the east of it?

15. What is the glacial term for Bonanza peak (NW)?

16. What would you call the bowl-shaped depression immediately NW of Holden Lake, and how did it form?

17. What are the coordinates of the glacier that is immediately west of Dumbell Mountain?

18. On a sheet of paper, sketch a ridge-to-ridge profile across the valley from point X (located at an elevation of 7726 ft. about 1 km east of Dumbell Mtn.) to Copper Peak. Label the X and Y axes with approximate distances and elevations. (Notice that you can exaggerate the vertical relief of the terrain by using different scales for the two axes.)

19. Calculate the average slope between Holden (elevation 3226 ft.) and the un-named peak (6319 ft.) almost directly to the north. Your answer must be unitless. Is this slope less than or greater than the stream gradient calculated on the Stovepipe Wells NE Quadrangle? How does the spacing of contour lines on a map relate to the slope of terrain features?

20.Thinking about the ridge-to-ridge profile you made for question 18, describe in detail how you might test the hypothesis that: glacially carved valleys are deeper and more "u"-shaped than stream carved valleys.

COASTAL

This exercise discusses how to identify structural, fluvial and coastal environments modified by marine processes. Shorelines are very active in their changing geomorphology. Since a large percentage of people live in coastal areas, it is important to understand how these changes will affect the existing inhabitants. The following questions refer to the Drake’s Bay Quadrangle, CA.

21. Drakes Estero (estero is Spanish for inlet or estuary) resembles a dendritic stream pattern. How did Drake’s Estero form? (Hint: the San Andreas fault is nearby.)

22. What is the prevailing direction of longshore drift in the vicinity of Limantour Spit? How do you know?

23. Examine the western coastline. What type of dunes are found in this area? Based on the appearance of the dunes, from which direction does the prevailing wind come?

24. What is the water depth in feet and meters immediately surrounding Chimney Rock at the peninsula's point?