Video review 4: The Geologic History of Southern California Watch the video by W
ID: 289819 • Letter: V
Question
Video review 4: The Geologic History of Southern California Watch the video by Wendy Van Norden in the study forum below. In this video, you will see the processes that formed the western United States. Notice how the various plates have moved over time. Write a brief review of this video. Explain how shifting plates has shaped the land we live on. How were the Sierra Nevadas formed? How was the Coastal Range formed? Are these processes continuing today? How do you know? Can you speculate on why there is a valley between the Sierras and the Coastal Range?
Explanation / Answer
ANSWER-
Geology of the Western America with South Carolina in particular-
The geologic setting of the area is a result of the platetectonics movement.There is North American plate made of continental crust and the Pacific plates made up of oceanic crust,in addition to the two smaller plates Juan de fuca plate(north) and Cocos plate (south).
During late cretaceous ,a series of plates subducted under N.America .During mesozoic ,Western edge of N.America was a subducting zone mostly basement rocks of California tha was created in this environment.Mountains of California such as Sierra Nevada and Coastal range with N-S orientation is a direct result of subduction that went on during mesozoic and th eearly cenozoic.Sierra was formed when farallon plate subducted under N.America.Coastal ranges are the result of pacific plate beneath the West border of N.America during mesozoic.During 18ma , tranform fault,San andreas fault was formed.Range province province started forming as Andreas fault formed and rims of continents pulled away due to motion of pacific plate.
In present days ,in Southern California ,present days Baha of Caifornia was pulled off from Mexico since miocene.Santa Barbara was formed as the rims of the continents were rotated.After rotation ,old rocks are pointing E-W and transverse ranges were formed including Santa Monica .The San Andreas fault makes the place vulnerable to earthquakes.
The central valley is thought to have been originated below sea level as an offshore area depressed by the subduction of the Farallon plate into a trench further offshore.
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