Lab 2B

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South Texas College *

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1445

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Geography

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Apr 3, 2024

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docx

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Lab 2B 1. In Figure 2B-1, the vertical and horizontal scales are given in kilometers, and the vertical scale is greatly exaggerated for readability. The vertical scale is only 10 km while the horizontal scale spans ___ km. 1 tick mark on the vertical scale represents 1 km while a tick mark on the horizontal scale is 100 km. d. 5000 2. The oceanic trench in Figure 2B-1 has a maximum depth near ____ km below sea level. a. 8 3. In Figure 2B-1, the active continental margin spans about 350 km and ends at a depth of 8 km. the passive continental margin spans about 900 km and end at a depth of 4 km. That is a slope of ____ for the active margin and ____ for the passive margin. (Slope is the vertical divided by the horizontal or “rise over run.”) a. 44 and 225 4. Tectonically active regions, typically associated with convergent plate boundaries, experience frequent earthquakes and/or volcanic activity. Convergent plate boundaries are found along the ____. Reference the previously examined locations of plate boundaries in Investigation 2A for help. a. western coast of North America 5. The east coasts of North and South America are tectonically passive. The broad continental margins results from ____. a. heavy sediment accumulation from river discharge 6. The west coasts of North and South America are tectonically active. What could happen to the sediment from the land that arrives on the active continental margins along the west coasts of North and South America? a. sediment flows to the ocean floor and accumulates along the continental rise 7. In Figure 2B-3, the vertical scale is in meters with sea level at 0 m and the horizontal distance in kilometers, from 75 degrees W eastward to 70 degrees W, for a total length of 500 km. Compare this vertical cross section with Figure 2B-1. Figure 2B-3 most closely resembles the ___ portion of Figure 2B-1.

b. left 8. The oceanic trench reaches a maximum depth of approximately 7400 m (7.4 km), about 80 km from the shoreline. The nearly horizontal continental shelf extends westward from the shoreline about 10 km before the profile declines steeply, reaching the maximum depth. This portion of the cross section compares to the ___ in Figure 2B-1. a. continental slope 9. West of the oceanic trench, the ocean floor rises and then levels off to a depth of approximately 3900 m, making the deepest part of the oceanic trench about ____ m deeper than the adjacent abyssal plain. d. 3500 10. Why is the cross section along a tectonically active region of the coast so steep? c. the active margin experiences numerous earthquakes that forces sediment farther into the ocean where it accumulates along the abyssal plain. 11. The horizontal distance in Figure 2B-5 is measured from 77 degrees W eastward to near 71 degrees W, covering a total length of about 475 km, and the average maximum depth of the nearly horizontal eastern portion is about 4400 m. Compare this vertical cross section with Figure 2B-1. Figure 2B-5 most closely resembles the ___ portion of Figure 2B-1. a. right 12. In the Figure 2B-5 profile, the coastline is within a few kilometers of the western (left) end. From the coastline, water depth increases very gradually to about 40 m at 140 km from the shore. This segment resembles the ____ as labeled in Figure 2B-1. c. continental shelf 13. Beginning at 140 km from land, the ocean floor profile “breaks.” The slope increases with increasing distance from the shoreline. At about 180 km distance from land, at a depth near 2400 m, there is a distinct change in the slope. The segment of the profile from 140 km to 180 km is the continental ____ portion of the continental margin as displayed in Figure 2B-1. b. slope

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