After our fascinating tour of Egypt and the divergent boundary around the Red Sea, we boarded a plane headed to San Fransisco, California. I loved being in Egypt for a few days but it felt good to be back in the US near home. John said that we were right on the San Andreas fault that lies on the Pacific Plate and North American Plate at 37°38'27.40"N 122°29'0.18"W. This boundary is a transform boundary which means that the two plates slide against each other. According to John this is why California has so many earthquakes, it lies right on a major fault line! Lucky for the people in California, transform boundaries don't cause volcanoes because there is no convection of rising magma or subduction of plates to cause an eruption, just a lot of shallow earthquakes.
A lot of the mountains and valleys in California have come from the movement of the San Andreas fault because as it moves rocks are displaced making high points and low points. A large trench can be seen where the fault line is. California has a history of seismic activity because of the San Andreas fault. Some of the famous earthquakes that came from the fault were the 1857 Fort Tejon earthquake, magnitude 7.9, the 1906 San Francisco earthquake, magnitude 7.8, the 1989 Loma Prieta earthquake, magnitude 6.9, and the 2004 Parkfield earthquake, magnitude 6.0. The San Andreas fault has existed for 15-20 million years and studies show that large earthquakes have occurred about every 150 years but thousands of small ones occur every year around the San Andreas fault.
After we learned all about the fault we traveled to some of the locations where you can see it and then went home to have dinner and get ready to go on our next adventure tomorrow. Here is a picture of one of the places we went:
- Katherine
Picture Sources:
http://en.wikipedia.org/wiki/File:MORMON_ROCKS_San_Andreas.jpg
your science is very nice and specific and your pics are great!
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