Plate Tectonics

1. The lithosphere is broken into several plates.

2. The plates move around.

3. Intense geologic activity occurs at plate boundaries.

Lithosphere - crust and upper mantle material, strong.

Asthenosphere - upper mantle material, weak (plastic)

Divergent Boundaries - plates are pulling away from each other.  Creates tensional stress.

Convergent Boundaries - plates are pushing into each other.  Creates compressional stress and subduction zones.

Transform Boundaries - plates are sliding beside each other in opposite directions (ex.  one going north the other going south)  Creates shearing stress.

Subduction Zones - one plate slides under the other plate.  Marine will subduct under a thicker slab of marine plate, or under a continental plate.  Continental plates will not subduct, instead they smoosh together like an accordian to form mountains.