Plate Tectonics and Crust Oceanic Lithosphere

1542 Words Mar 28th, 2013 7 Pages
| Lithosphere | Ecology (NASC 1093) |

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The Lithosphere * The lithosphere is the hard shell of the Earth, consisting of the crust and the topmost part of the upper mantle. * It is a relatively thin layer, about 31 to 62 miles (50 to 100 km) thick under the oceans and 93 miles (150 km) thick on the continents. * It contains the minerals, rocks and soils that humans have used for building materials, metals and agriculture. * This layer is composed of the upper crust, about 3 miles (5 km) thick in the oceans and 40.3 mles (65 km) thick on the continents, and the upper mantle, which makes up the remainder.

Two types of Lithosphere * Oceanic Crust * Continental Crust

Oceanic Lithosphere * the outermost layer
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As the overlying plate lifts up, it also forms mountain ranges. In addition, the diving plate melts and is often spewed out in volcanic eruptions such as those that formed some of the mountains in the Andes of South America. * At ocean-ocean convergences, one plate usually dives beneath the other, forming deep trenches like the Mariana Trench in the North Pacific Ocean, the deepest point on Earth. These types of collisions can also lead to underwater volcanoes that eventually build up into island arcs.
Three styles of convergent plate boundaries * Continent-continent collision * Continent-oceanic crust collision * Ocean-ocean collision
Continent-continent collision * Forms mountains, e.g. European Alps, Himalayas
Continent-ocean collision * Called SUBDUCTION
Subduction
* Oceanic lithosphere subducts underneath the continental lithosphere * Oceanic lithosphere heats and dehydrates as it subsides * The melt rises forming volcanism * E.g. The Andes
Ocean-ocean collision * When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. * The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. * The worlds deepest parts of the ocean are found along trenches. * Ex. The Mariana Trench is 11 km deep!
Volcanoes and Earthquakes
Volcanoes
* A volcano

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