Ch 2 Section 3 Internal Forces Shaping the EarthC 2 3节内力塑造地球.pptVIP

Ch 2 Section 3Internal Forces Shaping the Earth Plate Movement Convergent Boundaries Ocean-to-ocean collisions Ocean-to-continent collisions Continent-to-continent collisions Building up of mountain chains Thickest area of the continental crust Suture zones are the result where crust is destroyed as one plate dives under another This is how the Himalayas were formed. Divergent Plate Boundaries where new crust is generated as the plates pull away from each other The mid-Atlantic Ridge, a topographically high area near the middle of the Atlantic Ocean, is an example of a divergent plate boundary. Block Faulting, fractures and fissures result from the stress of the plates pulling apart Basaltic magma wells up through fissures creating new surface New ocean floor is created (50% of the Earth’s surface has been created in the last 200 million years) Divergent plate boundaries usually occur below the sea however in Africa and North America rifting is occurring on the continent Transnational Boundaries No overriding No subduction Designated by a fault complex San Andreas is an excellent example Formed from the gradual subduction of the Farallon Plate during the Cenozoic Farallon Plate ran along the west coast of North America North America plate consumed the middle portion of the Farallon Plate which left 2 small fragments to the north and south – Gorda and Cocos plates North America plate hit the east Pacific rise and overrode the rise so that the actual plate boundary between North America and Pacific plates is now the San Andreas fault line Earthquakes Tsunamis Pacific Ring of Fire – about 80% of all earthquakes happen HERE