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 .