1. What type of faults (normal, reverse, thrust, strike-slip) would you expect i
ID: 116857 • Letter: 1
Question
1. What type of faults (normal, reverse, thrust, strike-slip) would you expect in the Rio Grande rift zone in New Mexico. Why? (1 pt) 2. Other than the Rio Grande rift valley in New Mexico, name ONE other active rift zone (use a global geologic map). (1 pt) 3. Why are the rocks created in rift valleys and at mid-ocean ridges mafic and not felsic? (1 pt) 4. Africa and S. America are now ~5,100 km apart, if the average spreading rate between these two plates is 30 mm/yr, about long ago did the continents separate (in Myr)? Show your work. (2 pts) Section II: Use a global geologic map and Figure 8.1 to answer the following questions: 5. The Marianas Trench (southwest of Hawaii) is the site of the deepest oceanic trench on Earth and separates the Pacific plate from the Philippine plate. What in the dominant type of crust (oceanic or continental) these plates are made of? (1 pt) 6. Determine which is the subducting plate and which is the overriding plate at the Marianas Trench and list them below. (2 pts) 2 7. For the last ~60 Ma, Indian continental crust has been colliding with Asian continental crust to create the Himalayan Mountains and the Tibetan Plateau. Prior to this time, there was widespread andesitic volcanism and magmatism on the southern margin of the Asian continent. If we go back in time to before Indian continental crust collided with Asia, what type of plate boundary might we expect? What type of crust might be on either side of the plate boundary (oceanic or continental)? (2 pts) 8. Where in the contiguous United States do we still have an active margin? What is the name of the magmatic arc chain associated with the active margin? What type of volcanic rocks would you expect here (rhyolite, basalt, or andesite)? (1 pt) 9. Why are there mountains on the west coast of South America, but not the east coast? (1 pt) Section III: General questions 10. If you are standing in Los Angeles, what direction is Las Vegas moving in relation to you (N, S, E, W, NE, SE, SW, NW)? (1pt) 11. Look at Figure 8.6. If movement along the San Andreas fault averages 5.5 cm per year, how long will it take before Los Angeles is adjacent to San Francisco, if the two cities are ~550 km apart (in Myr)? Show your calculations. (2 pts)
Explanation / Answer
1. mainly normal faults because the half graben geometry is frequently observed.
3. the sedimentary fill of the basind consists largely alluvial fans and mafic volcanic flows. the most alkalic lava erupted outside the rifts and the sedimemts deposited during rifting contains sandstone,conglomerate,volcanics.
5. The Marianas Trench (southwest of Hawaii) is the site of the deepest oceanic trench on Earth and separates the Pacific plate from the Philippine plate.bothe are made of oceanic type of crust.
6. pacific plate subducted beneath the mariana plate.
7. For the last ~60 Ma, Indian continental crust has been colliding with Asian continental crust to create the Himalayan Mountains and the Tibetan Plateau. Prior to this time, there was widespread andesitic volcanism and magmatism on the southern margin of the Asian continent. If we go back in time to before Indian continental crust collided with Asia, that was also a collisional boundery.
continental type of crust might be on either side of the plate boundary.
8. in the contiguous United States we still have an active margin is west coast of south america.
the name of the magmatic arc chain associated with the active margin is andes moutain belt.
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