Plate Tectonics

Boundary Types Divergent: plates move apart Convergent: plates move toward each other Transform: plates move horizontally past each other

Boundary Movement

Associated with earthquakes and volcanoes Divergent Plates move apart Most on sea-floor at rift valley Sea floor spreading begins New ocean floor formed Associated with earthquakes and volcanoes Divergent boundary on continents creates a rift valley. i.e. East African Rift Valley a.k.a. Constructive boundary

East African Rift Valley

Convergent Boundaries Oceanic to Continental Example: Cascade Mountain Range Oceanic crust dense therefore Subduction occurs a.k.a. Destructive boundary

Convergent Boundaries (cont) Oceanic to Oceanic Oldest crust is the most dense and will subduct. The Marianas Trench, for example, is a deep trench created as the result of the Phillipine Plate subducting under the Pacific Plate. http://www.platetectonics.com/book/page_5.asp

Convergent Boundaries (cont) Continental to Continental Relatively light and resist downward motions so the land buckles up or sideways. Example: Himalayas and Appalachian http://www.platetectonics.com/book/page_5.asp

Transform Boundary Plates slide horizontally past each other Most occur along mid-ocean ridges San Andreas Fault in CA is transform boundary found on land Associated with EARTHQUAKES http://www.visionlearning.com/library/module_viewer.php?mid=66

San Andreas Fault

Causes of plate motion