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Plate Tectonics

Plate Tectonics. Hannah Pinsent. Theory. The tectonic plate theory arose out of the hypothesis of continental drift. Alfred Wegener was the main man who proposed the theory by writing a book in 1915, ‘ The Origin of Continents and Oceans’.

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Plate Tectonics

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  1. Plate Tectonics Hannah Pinsent

  2. Theory • The tectonic plate theory arose out of the hypothesis of continental drift. • Alfred Wegener was the main man who proposed the theory by writing a book in 1915, ‘ The Origin of Continents and Oceans’. • He thought that the Earth's continents were once joined together, but gradually moved apart over millions of years. It explained the existence of similar fossils and rocks on continents that are far apart from each other. But it took a long time for the idea to become accepted by other scientists. • In the 1960’s the plate tectonic theory was finally formulated.

  3. Alfred Wegener’s Evidence • Similar fossilised animals and plants are found in South America and Africa. • The shape of the east coast of South America fits the west coast of Africa, as if the world was a jigsaw puzzle. • matching rock formations and mountain chains are found in South America and Africa.

  4. Other Evidence • Later on scientists found that: • The old geological theory explained mountains as wrinkles made by the Earth shrinking as it cools down. • There was no clear explanation of how continents could move about. AND • In the 1950s, evidence from magnetism in the ocean floor showed that the seafloors were spreading by a few centimetres each year. This showed movement of large parts of the Earth’s crust, now called tectonic plates.

  5. BEFORE NEXT AFTER

  6. The different types of plate boundary • Divergent- found where two plates are moving away from each other • Convergent- boundary where two plates collide/ push towards each other (also known as destructive plate boundary) • Subduction Zones- Area where two plates collide and one is forced under the other.

  7. Earthquakes • Occur when two plates are rubbing against each other and build up pressure. • The pressure causes friction. • The pressure is released causing an Earthquake. • They are devastating: kill/ injure many people; destroy homes and destroy economies.

  8. Volcanoes When magma reaches the Earth’s surface causing eruptions of lava and ash. They occur at destructive and constructive plate boundaries. There are two main types of volcanoes: Shield (runny lava) and Cone (less runny lava)

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