San Andreas Fault Rocks

The rock at the San Andreas fault can tell us a lot about the fault itself. On a field trip that we took recently to the San Andreas fault we saw rocks that had been put under so much pressure that the rocks turned into a smooth, glassy texture(Wikipedia Contributors). This is called slick and slide. You can see the extreme pressures that accrue at a transform fault. We also found a schist and gneiss that was folded by the compressive forces at the San Andreas fault. All of these rocks tell us that there are extreme forces molding the rocks. The schist that we found there, called Pelona schist was formed in the ocean when sand and other sediments fell into the ocean and metamorphosed. It was uplifted by the movement of the Pacific plate and is now found on land.

(Wikipedia Contributors)

Mormon Rocks

One of the rock formations along the San Andreas fault is Mormon rocks in the Cajon pass. They are made of sandstone and are visible from I-15. Sandstone is formed when grains of sand at the bottom of lakes, rivers or oceans are compacted and cemented together over thousands or millions of years. At Mormon rocks you can tell that they were formed in a river or lake because of the layers of sediments. The layers go from sand sized particles to gavel and cobbles sized rocks, sand sized particles to gavel and cobbles sized rocks and so on. This is proof of a flooding event. You might wonder why the Mormon rocks are at a tilted angle. They were lifted by the movement of the San Andreas fault.

(Google Maps)

(“Hiking in Mormon Rocks, CA”)

(“Mormon Rocks Interpretive Trail”)

(“Mormon Rocks, Hesperia California”)

Bibliography

“Hiking in Mormon Rocks, CA.” Travel Tips - USA Today, 2013, traveltips.usatoday.com/hiking-mormon-rocks-ca-108985.html. Accessed 24 Apr. 2023.

“Mormon Rocks, Hesperia California.” Adventuresinsoutherncalifornia.com, 2013, www.adventuresinsoutherncalifornia.com/2012/05/mormon-rocks-hesperia-california.html. Accessed 24 Apr. 2023.

“Mormon Rocks Interpretive Trail.” Outdoor Project, 2021, www.outdoorproject.com/united-states/california/mormon-rocks-interpretive-trail. Accessed 24 Apr. 2023.

“Mormon Rocks near the Cajon Pass.” Calisphere, 2023, calisphere.org/item/4f1999004faa0af1ab5fbf210ed6d129/#:~:text=The%20Mormon%20Rocks%2C%20also%20known,re%2Dexposure%20of%20these%20beds. Accessed 24 Apr. 2023.

Wikipedia Contributors. “Slickenside.” Wikipedia, Wikimedia Foundation, 31 Mar. 2023, en.wikipedia.org/wiki/Slickenside#/media/File:Slickenslides_at_500m_depth_in_a_Permian_sandstone.jpg. Accessed 30 May 2023.

‌

Page updated

Google Sites

Report abuse