5 Things to Know: PLATE TECTONICS
1. Plate tectonics is the movement of the crust of earth (lithosphere).
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Oceanic crust is denser than continental crust.
2. Movement occurs because of convection currents in the asthenosphere, which move the
lithosphere on top. Mantle heats up as it approaches the core, so it rises to the top,
where it cools and cycles back down toward the core, and so on and so forth.
3. Divergent plate boundaries – two plates moving away from one another
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Seafloor spreading – Red sea, Mid-Atlantic ridge, East pacific rise
4. Convergent boundaries – two plates move toward each other
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Subduction: oceanic crust is pulled underneath the continental crust because its
denser. 95% volcanoes are subductions zones (other 5% are “hot spots” where
magma is close to earth’s surface)

Continental-continental: mountains
5. Transform fault boundaries – two plates slide past each other.
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Cause earthquakes (San Andreas Fault in CA)
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Epicenter of earthquake is on earth’s surface directly above the focus (area where
energy is released)
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Earthquakes can cause tsunamis