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Plate Tectonics The Earth’s Crust is Made of Plates What Causes the Plates to Move? • Convection- hot magma rises, cool magma sinks (like a lava lamp Two Types of crust • Continental Crustmade of granite (light) • Oceanic Crust- made of basalt (heavy) Plate Boundaries • Cracks in the plates are called faults Types of Boundaries (Faults) • Convergent Boundary • Divergent Boundary • Transform Boundary Divergent Boundary • Plates move away from each other • Forms volcanoes, new crust and rift valleys • Ex) Iceland, midAtlantic ridge Divergent Boundary – Arabian and African Plates Divergent Boundary – Iceland http://pubs.usgs.gov/gip/dynamic/understanding.html Rift Valleys • A deep valley formed as plates move apart at a divergent boundary. • Ex) The Great Rift Valley in eastern Africa Sea Floor Spreading • Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins • Magma rises to the surface and solidifies and new crust forms • Older Crust is pushed farther away from the ridge Transform Boundary • Plates slide past each other • Creates earthquakes • Ex) San Andreas Fault in California Convergent Boundary • Plates move toward each other • Earthquakes, forms mountain ranges • Ex) Himalayan Mountains Continental-Continental Boundary • Plates fold, creating mountains Convergent Boundaries - Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Oceanic-Oceanic Boundary • • • • Creates trenches (deep valleys) Forms volcanoes Forms Island Arcs Ex) Aleutian Islands (Alaska) Convergent Boundary – Oceanic & Oceanic Subduction occurs when the denser plate sinks below the other http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Oceanic-Continental Boundary • Oceanic plate pushes down because it is more dense. • Creates deep ocean trenches • Creates coastal mountain ranges • Ex) Andes mountains Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Hot Spots • Hot material rises from deep within the mantle. • Heats the lithosphere, causing volcanoes at the surface. • Ex) Hawaiian Islands, Yellowstone N.P. Evidence of Pangaea Vocab to Remember • Fault • Convection • Divergent Boundary • Convergent Boundary Vocab ctd… • Transform Boundary • Rift Valley • Hot Spot