Notes: Plate Tectonics

There are three types of plate boundaries: divergent, convergent, and transform

1. Divergent Boundary: occurs between plates that are separating  most divergent boundaries are between 2 oceanic plates and occur at the mid-ocean ridge; some geographic examples of places where this is happening are the Mid-Atlantic Ridge and the East Pacific Rise  The Great Rift Valley in Africa is a geographic example of a continental-continental divergent boundary where the African continent is being broken into smaller plates

2. Convergent Boundary: occurs between two plates that are coming together; there are 2 kinds of convergent boundaries – subduction and collision A. Subduction  Possible plate combinations are oceanic-continental or oceanic-oceanic  the denser and thinner plate buckles down under the less dense plate, plunges down (gets subducted) into the mantle and melts; a trench forms at the place where the plates meet and one goes under the other  Volcanoes usually form on the overriding plate (sometimes mountains form)  Geographic examples are the Mariana Trench and the Aleutian Trench B. Collision  Occurs where 2 continental plates come together  Forms high mountain ranges  Geographic examples are the Himalayas and the Appalachians 3. Transform Boundary: occurs where plates slide past each other, usually in opposite directions but can be in the same direction but at different rates  This type of boundary causes lots of earthquakes and faults  A geographic example is the San Andreas Fault in California