Plate Boundaries

The Change, Destruction, Death and Rebirth of the Crust

A. Divergent Boundaries

= Constructive plate boundaries– Two plates moving away from each other

I. The Oceanic Ridge– A very long crack in the crust which lets out lava– Driving Force of Plate movement• Creates new oceanic crust• As more crust is created

– “Pushes” 2 plates away from each other

The Oceanic Ridge

B. Convergent Boundaries

= Destructive plate boundaries– Two plates crushing against each other• Earthquakes• Volcanoes• Mountains

• Three TypesI. Oceanic-ContinentalII. Oceanic-OceanicIII. Continental-Continental

B. Convergent Boundaries

I. Oceanic-Continental• Oceanic Crust = More dense• Continental Crust = Less dense

– When they collide • More dense Oceanic Crust subducts under less dense

Continental Crust– Friction causes Heat– Depth causes pressure– Creates Volcanic Mountain Ranges

» Continental volcanic arc

B. Convergent Boundaries

II. Oceanic-Oceanic• One Oceanic crust descends under the other• Creates Volcanic Island Arc

– Aleutian Islands – Alaska– Japan– Philippines

B. Convergent Boundaries

III. Continental-Continental– Starts off as Oceanic-Continental

– Creates Continental Volcanic Arc

1. Oceanic Plate happens to carry Continental Crust2. Continental Crust collides with Continental Crust

– This Forces existing Volcanic Arc even more upward» India collides into China 10 million years ago

C. Transform Fault Boundaries

– Plates grind against each other – Without destroying the crust

– San Andreas Fault• California