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=Plate Tectonics=

Plate tectonics is how the Earth's surface moves. The surface is divided into different plates. Where two plates meet, there is one of three types of boundaries formed. The three boundaries are convergant, divergant, and transform. Each of these boundaries have different affects on the Earth's crust.

=Convergant Boundaries  =

When convergant boundaries are formed one plate goes into the surface while the other rises to form mountain ranges. The plate that goes under often melts and is then spewed out of volcanoes that may have been formed from the top plate. When these boundaries are formed under the oceans, the plate that "dives" or goes under forms trenches. One these trenches' name is the Mariana Trench. It is the deepest in the world. It is around 7 miles deep. This trench formed when the Pacific and Asian plate collided in the north atlantic ocean. Another example are the Himalayan Mountains. The mountain range formed when the Indian and Asian plates came together to separate India from Asia. The Himalayas formed about 55 million years ago. The mountains are also home to the largest mountain in the world, Mt Everest. Mt Everest is about 29,000 feet high. Since the two plates that formed the mountain range ares continuously pushing together the mountain range's height grows about a 1/4 inch per year. In underwater mountain ranges there can also be underwater volcanoes. When the volcanoes erupt the, lava that flows out eventualy hardens. After so many eruptions the harden lava builds up and sometime reaches the surface to form arc islands. An example of arc islands is Japan. It was formed from the underwater volcanoes in the north west atlantic ocean



=Divergant Boundaries=

Divergant boundaries are formed when magma rises and pushes the plates away from eatchother. Where these boundaries are mountains, volcanoes, and valleys form.one example is the Mid Atlantic Ridge. It is in the Mid Atlantic Ocean formed between the four paltes that make up the Atlantic Ocean. These four plates are the Eurasian Plate, the North American Plate, the South American Plate, and the African Plate. This ocean ridge is one of many ocean ridges in the world. Together all ocean ridges connect all of the world's oceans. They are literaly the worlds longest mountain range in the world, about 25,000 miles long. The Mid Atlantic Ridge on its own is about 6,200 miles long. Another famous boundary of this type is the Great Rift Valley in Africa. It is one a fault line in eastern Africa. If the plate keeps pulling apart in africa, eventualy millions of years from now, eastern Africa will brake awayfrom the continent to form an entirely new landmass. The Alfagja rift valley is another example of a divergant boudary. It is located in Southwest Iceland. It is being pulled apart from the Eurasian and North American Plates.



=Transform Boundaries=

Transform Boundaries are where two plates grind past eatchother. These boundaries don't form mountains or volcanoes but they do cause devastating earthquakes. One of the most deadliest earthquakes in history was caused from a transform boundary in 1908 in San Fransisco California. This Boundary is called the San Andreas Fault. It runs straight through California. This Fault is made from the Pacific And North American plates pulling away from eatchother. Another exanple is the Alpine Fault in New Zealand. It is Created from the Pacific and Australian Plates grinding past eatchother. The last example of a transform boundary is the North Antolian Fault in Turkey. This is formed from the Eurasian and Arabian Plates making a transform Boundary. ==

=Citations=

[] [] [] http://earthquake.usgs.gov/ http://en.wikipedia.org/wiki/plate_tectonics