this is the image of thr San Andreas fault Part 5: Plate Motions and Reconstruct

Question

this is the image of thr San Andreas fault

Part 5: Plate Motions and Reconstructions The evolution of the San Andreas fault system over the last 30 million years is shown below (http://pubs.usgs.gov/publications/text/Farallon.html). Note that each image panel represents a different time in the geologic past. The Pacific plate curren is moving past the North American plate at a rate of about 3.5 cm/year. 1. What is the relative sense of motion along the San Andreas Fault today? es? 2. During what time (in millions of years) would you expect volcanoes near Los Angel hy (i.e, what type of plate boundary existed there at that time)? 3. Should there be active volcanoes in Los Angeles today? Why or why not? Using the scale on the map and the rate of plate motion above, determine how long it will take Los Angeles to reach San Francisco. 4. 139

Explanation / Answer

1) Two of these moving plates meet in western California; the boundary between them is the San Andreas fault. The Pacific Plate (on the west) moves northwestwardrelative to the North American Plate (on the east), causing earthquakes along the fault.

This fault is a long transform that connects divergent boundaries in the Gulf of California with a divergent boundary and subduction zone off the northern coast of California.

The relative sense of motion on theSan Andreas fault is right lateral.

2) about 10 or 20 million years from now the pacific plate from the west will get started subducting into the american plate to the north exactly at the los angeles current location

the subduction zone of that time will get occur the volcanic activities due to bennioff zone near los angeles.at that time convergent plate boundry will be there near los angeles.

3) the los angeles is passing throgh the right lateral transform plate boundry which is also called san andreas fault.

in transform plate boundry activities neighther the crust is made or distroyed so there is no chance of volcanic erruption or volcanic activitiesnear los angeles at present day.

4) Consider this: California is about 1000 miles long. That's

1000 miles x 5280 ft/mile x 12 inches/ft = 63,360,000 inches

At the measured slip rate of about 2.5 inches per year, it will take

63,360,000 inches/ 2.5 inches/year = 25.3 million years

so according to this moion speed

the distance where san fransisco is currently there from los angeles is around 400 miles

so the movemet of plate is 1000miles over 25 million years

so for around 400 miles it will take around 10 milliion years more.

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