Plate Tectonic Theory Theory of Plate Tectonics -Earth’s crust is broken into plates which float and move.

Earth’s crust made of many plates is similar to the shapes on a outside of a soccer ball.

There are about 13 plates covering Earth’s surface

Two Types of Plates Continental Plates – lighter, thicker, made of granite Oceanic Plates – heavier, thinner, made of basalt

Plate Boundaries (edges) When the plates move, their boundaries, or edges, can scrape each other or collide.

Convergent Boundary Plates move toward each other

Convergent Boundary When two continental plates move into each other, the plates combine and form mountains. (India into Asia) om/media/attachment.action ?quick=12t&att=2783

Convergent Boundary When an oceanic plate runs into a continental plate, the heavier oceanic plate subducts (sinks) into the mantle and melts back into magma.

Volcanic mountains and deep sea trenches are created along this edge. absorblearn ing.com/me dia/attachm ent.action? quick=12s &att=2781

Oceanic plate into continental Example: Pacific plate (oceanic) subducts (sinks) under Japan (continental).

Divergent Boundary Plates move apart

When both diverging plates are oceanic, it is called seafloor spreading (Mid-Atlantic Ridge)

When both diverging plates are continental it is called rift valley formation (Africa) hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/ /30425/19_21.swf::Fig.% % 20-%20Evolution%20of%20a%20Divergent%20Plate%20Boundary

Transform Boundary Plates slide past each other

San Andreas Fault

San Andreas Fault, CA Each time the plates slide past each other, an earthquake occurs

Find the three boundaries

Asthenosphere A plastic-like layer found below the lithosphere. The rigid oceanic and continental plates of the lithosphere sit on top

The Asthenosphere is heated by the hot Outer Core

Convection Current Hot material rises, cooler material sinks, creating a current, called a Convection Current core mantle crust

When the asthenosphere moves, it carries the lithospheric plates Convection currents cause plate motion

Every time these plates move we get earthquakes, volcanic eruptions, and possibly tsunamis