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Plate Tectonics and the Pacific Northwest

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Plate Tectonics & the Pacific Northwest
April Pilcher
7/18/16
GLG/150
Anna Foutz

Plate Tectonics & the Pacific Northwest Plate tectonics is a scientific theory that tries to explain the movements of the Earth’s lithosphere that formed all of the landscape features we see today. The theory of plate tectonics says that the Earth’s lithosphere is made up of individual plates that are broken down into over a dozen different sized pieces of solid rock. The theory of plate tectonics was first discovered by Alfred Wegener in the 20th century. Wegener figured out that all of the continents seemed to have similar edges leading him to believe that the continents were once all connected. He called this a supercontinent and named it Pangaea. He believed that the continents of Pangaea started drifting apart about 300 million years ago and was later known as Continental Drift. ("Geography.about.com", 2016). The Pacific Northwest has a lot of tectonic activity causing many earthquakes. The three tectonic plates that influence these earthquakes are The North America, Juan De Fuca, and the Pacific plate. These three plates make up what is called the Cascadia Strain. The most common damaging earthquakes in Washington and Oregon are deep earthquakes from Juan De Fuca. These earthquakes occur when Juan De Fuca starts to bend and plunge underneath North America. Stresses cause faults in the down going crustal part of the plate causing it to rupture. The Cascadia Subduction Zone is a plate boundary that stretches from Vancouver Island to northern California. Cascadia’s deepest earthquakes are about 100km deep but many subduction zones have earthquakes extending to 600km deep. Cascadia has averaged an earthquake every 243 years over the last 10,000 years. There have been 41 monster quakes along the Cascadia Subduction Zone in that period. The last one was 314 years ago.…...

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