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Plate Tectonics

Plate Tectonics. http://www.learner.org/interactives/dynamicearth/images/new_map.jpg. Tectonic Plates. The Earth’s crust is made of many gigantic plates that move as they ‘float’ on the mantle. According to the theory of continental drift, the plates are moving.

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Plate Tectonics

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  1. Plate Tectonics http://www.learner.org/interactives/dynamicearth/images/new_map.jpg

  2. Tectonic Plates • The Earth’s crust is made of many gigantic plates that move as they ‘float’ on the mantle. • According to the theory of continental drift, the plates are moving. • Europe and North America are thought to be moving away from each other 3cm each year. • Other plates are moving toward each other and some are sliding against each other. • Wherever plates meet, earthquakes signal their movement.

  3. Tectonic Plates

  4. Pangaea • Have you ever noticed that the continents look like puzzle pieces? • In 1912, Alfred Wegener suggested that millions of years ago the continents were all part of one big continent called Pangaea. http://upload.wikimedia.org/wikipedia/commons/1/16/Wegener_Expedition-1930_008.jpg

  5. Pangaea http://azgenweb.org/navajo/History/Petrified/Pangaea_continents.png

  6. Continental Drift • Wegener suggested that Pangaea had broken apart and that the continents had and still are drifting apart. • This theory is called Continental Drift • At the time, Wegener’s theory was dismissed as he had no evidence besides the fact that the continents fit together. http://newpangaea.eu/sitebuildercontent/sitebuilderpictures/Pangaea.JPG

  7. The Evidence • Certain fossils of extinct reptiles found only in Africa and South America. • Fossils of plants and animals found in Antarctica, which is now inhabitable. • Rocks similar in age and type found along the coasts of continents that fit together. http://www.lostrivers.ca/points/pangaea.gif

  8. Plate Tectonics Theory • Theory that states that the Earth’s crust is made up of several large sections called plates. • These plates are slowly moving, floating on top of the Earth’s mantle. • Continents drift by riding on top of the plates. http://www.geography-site.co.uk/pages/physical/earth/images/plates.gif

  9. Sliding-By Plates • When two plates slide against each other, a fault is formed. • The plates do not collide or separate; they just slip by. • Ex) The San Andreas Fault in California. http://lacreekfreak.files.wordpress.com

  10. Plate Collisions • When two plates collide, one plate usually plunges below into the hot mantle where it heats up and melts. • This process is called subduction. http://whyfiles.org/031volcano/images/subduction.gif

  11. Separating Plates • When two plates move apart, magma from the mantle rises up into the crack between the two plates and hardens. • This forms ridges of new rock. • Ridges usually form under the ocean but does occur in Iceland also. http://www.utexas.edu/tmm/npl/mineralogy/blowups/oceanicridge.jpg

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