To answer question 20, look at look at the Geologic Map of North America in your
ID: 160066 • Letter: T
Question
To answer question 20, look at look at the Geologic Map of North America in your classroom. Look at the western portion of North America, near Nevada and Utah, parts of Arizona, and northwestern Mexico (the Sierra Madre Occidental). What is the predominant type of fault that occurs in these regions? What type of stress causes this type of fault? What is the orientation (compass direction) of most of these faults? We have discussed the mountains that result from this faulting many times in this class and in your Physical Geology class. What do we call this part of North America?Explanation / Answer
a) Most of the World's Earth quakes and active faults occur in narrow belts that outline a mosaic pattern on the earth surface much like the patchwork surface of a soccer ball. These zones define the edge of large crustal plates. The plates move slowly across the earth surface in different directions. earth quakes occur as these plates bump into, plunge benath or spread aprt from each other. Not all earth quakes occur at plate margins, though the Intermountain seismic belt(ISB) in which Wasatch fault is located is one example.
ISB extends Montana to Nevada and arizona 800 miles.Located within the western interior of North American plate,much of the area is active for million of years.Long ago the area now Nevada and utah compressed.With changing plate motions the bain and range began stretching and and the crust adjusted to this new motion through the proces of Normal faulting. The wasatch fault one such adjustment marks the eastern edge of basin and range extension.
b) Stress is similar to earth quake causing fault means the liquod magma under the plate starts causing pressure.
c) Wasatch mountains uplifted and tilted towards east.
d) Block mountain range--the upper portion is called Horst and downeard is called graben.
other examples of block mountains are Rhine valley and vosges mountains in Europe.
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