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Evidence of Plate Tectonics http://www.mnh.si.edu/earth/text/4_1_2_3.html
Evidence of Plate Tectonics• 1980s• Ten years of telescope-based measurements from Earth to distant quasars confirmed that the North American and Eurasian Plates are moving away from each other at a rate of 1.7 cm (0.7 in) per year.• Geological studies of ocean- floor rocks suggest the plates have moved at this same average speed for tens of millions of years.
Evidence for Plate Tectonics • Two telescopes — one in Massachusetts, the other in Germany — measured their distance to a pulsing quasar at the same time. This measurement was repeated 803 times over 10 years. Each point on the graph indicates how far apart the two stations were at that time. As you can see, they slowly moved apart.
Plate Tectonics and Volcanos• A volcano is an opening, or rupture, in a planets surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.• Volcanoes are generally found where tectonic plates are diverging or converging.
Volcanos and Divergent Plate Boundaries• A mid-oceanic ridge, for example the Mid- Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart
Volcanos and Convergent Place Boundaries• http://geology.com/nsta/convergent-plate- boundaries.shtml
Volcanos and Convergent Plate Boundaries• The Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together.
Volcanic Islands • Not all volcanos occur at plate boundaries • Hot spots, locations of rising hot magma, can cause magma to reach the surface causing volcanos
Formation of the Hawaiian Islands
Snake River Hotspots Yellowstone
Earthquakes• An earthquake is the result of a sudden release of energy in the Earths crust that creates seismic waves.• The seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.
1989 San Francisco Earthquake• http://www.youtube.com/watch?v=zkx- vO9I8r8&feature=related
Tsunami• A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake.• Earthquakes, volcanic eruptions and other underwater explosions, landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.