Plate Tectonics

Sea-Floor Spreading Process by which new oceanic lithosphere is created as older materials are pulled away Creates Mid-Ocean Ridges Underwater Mountain Chains

Theory of Plate Tectonics Theory that both continental and oceanic crust move Theory states: Earth’s lithosphere is divided into tectonic plates that move around on top of the asthenosphere

Causes of Motion Heat and Gravity Convection Slab Pull Hot material rises and cooler material sinks. Drags tectonic plates sideways Slab Pull Oceanic lithosphere is denser than the asthenosphere. Oceanic plate sinks and pulls the rest of the plate with it

Tectonic Plate Boundaries Convergent Two plates push into another Result depends on what type of crust Continental / continental Push crust upward Continental / Oceanic Oceanic plate slides under Oceanic / Oceanic One of the plates slides under

Tectonic Plate Boundaries Divergent Two plates move away from each other Examples: Sea-floor spreading Mid-ocean ridges are the most common Can be found on continents

Sea-Floor Spreading Process Plates move away from each other Creates a gap in the sea floor Magma rises to fill gap Magma cools and forms underwater mountains

Newer Crust = At the Mid-ocean crust Older Crust = Edges of continents

Tectonic Plate Boundaries Transform Two plates slide past each other horizontally Plates are smooth so they grind and jerk Cause Earthquakes Example San Andreas Fault in California

Tracking Plate Motion Slow and Gradual Measured in centimeters per year Measure using GPS Global Positioning System