11/18/15

 Earth’s lithosphere is divided into tectonic plates that move on top of asthenosphere  Theory of plate tectonics explains: Continental drift Sea-floor spreading

Hot material from deep within Earth rises while cooler material near surface sinks Motion of convecting mantle drags plates sideways Convection

 Ridge Push Occurs at mid-ocean ridges  Higher elevation than surrounding lithosphere Gravity causes the ridge to “push” oceanic plate down the lithosphere- asthenosphere boundary

 Slab Pull Oceanic lithosphere denser than asthenosphere Oceanic plate sinks and pulls rest of tectonic plate with it  Occurs because of process of subduction

 Occurs when two plates push into one another  Three types (depends on plates involved) Continental/continental Continental/oceanic Oceanic/oceanic

 Occurs when two tectonic plates move away from one another  Results in new oceanic lithosphere (sea-floor spreading)  Can also be found on continents East African Rift

 Occurs when two tectonic plates slide past each other horizontally  Plates grind past one another often resulting in earthquakes Tectonic plates are not smooth San Andreas Fault

 Movement affected by: Type of plate Shape of plate Interaction with surrounding plates  Generally slow (few centimeters per year) San Andreas fault is exception  Measure motion by use of GPS  “Stationary” GPS satellites send signals to ground stations Amount of time taken to receive signal in relation to distance determines rate