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In the beginning of 2010 there has already been some significant seismic events. There was the Haiti Earthquake that flattened Port Au Prince and took over 200,000 lives. It was the deadliest disaster since the Christmas Tsunamis. Now Chile has just experienced a major earthquake that was 8.8 on the Richter Scale. This earthquake is the most powerful to hit Chile in 50 years. It is now likely spurring tsunamis all across the Pacific Ocean. However what causes these seismic events and other geological phenomena? The reason is plate tectonics.
To understand plate tectonics you need to understand the structure of the Earth. The Earth is like an onion with many layers. However, not all these layers are solid and neither are they all one piece. The part of the Earth where life resides and where most of the geological activity we observe occurs is called the crust. The Crust includes both the continents and the bottom of the Earth’s seas. The interesting thing is that instead of being all one peace it is made of interlocking and interacting pieces that we call plates. This is where plate tectonics. The Earth’s crust essentially floats on a layer of molten rock and magma called the mantle.
What causes plate activity is the convection currents in the magma. Like a raft on the ocean currents the plates are moved by the magma this is what causes the formation and separation of landmasses over periods of times. What cause earthquakes and other seismic activity is when the plates literally bump into each other.
One source of this interaction is sea floor spreading. The oceanic crust is much thinner than that of the Continents. So in certain areas of the ocean floor there are weak zones where magma from the mantle can escape. This hardens and create new rock to form the crust. This is one of the forces that help push the continents apart. Another phenomena is subduction when two plates where they are oceanic or continental meet one most “win.” That is one will slide over the other forcing it down into the mantle. Normally the denser plate is the one that sinks.
The interaction of plates cause boundaries called plate boundaries and faults. These can either be convergent, divergent, or transforming boundaries. This can cause different things. For example, if the boundary is convergent like when two continental plates are colliding can cause the formation of volcanoes and young mountains. They also cause other events like earthquakes and tsunamis.
If you enjoyed this article there are several others that you will enjoy. There is a great article about Plate Boundaries. There is also an interesting article on tectonic plates which talks in detail about how the plate move and are formed.
You can also find some great resources online. You can check out the Plate Tectonics page on the University of California Berkley website. The USGS Dynamic Earth website is another excellent source of information.
You can also listen to Astronomy Cast. Episode 142 talks at length about Plate Tectonics.