Plate Tectonics Explained

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The interior structure of Earth is chemically divided into an outer solid crust, the mantle, a liquid outer core, and a solid inner core. The core is largely composed of iron, along with nickel and silicon. Other lighter elements are usually in the crust.
The core is divided into two parts, the solid inner core and the liquid outer core. The inner core is thought to be solid and primarily made up of iron and some nickel. The outer core is all around the inner core and is believed to be made up of liquid iron mixed with liquid nickel. The outer core is about 2890 to 5100km. The inner core is 5100 to 6378km.
Earths mantle is mainly composed of substances high in iron and magnesium. The melting point of every substance depends on the pressure and the deeper we go the higher the pressure becomes. Because of this the upper mantle is said to be semi-molten and the lower mantle solid. The upper mantle iron-substances are semi-molten because it is hot and they are under little pressure, lower mantles iron-substances are solid because they are under a lot of pressure. The mantle is 35 to 2890km.
Earths crust ranges from 5 to 70 km in depth. The thinnest parts are the oceanic crust made of dense iron magnesium silicate rocks and underlie the ocean basins. The thicker crust is continental crust, composed of sodium potassium aluminum silicate rocks. The crust varies from 0 to 35 km or 5 to 70km.
Convection currents occur because the density of a fluid is related to its temperature. Hot rocks lower in the mantle are less dense than the cooler rocks above. The hot rocks rise and the cooler rocks sink because of gravity. Convection currents are thought to be the driving mechanism of plate movement. Convection currents cause convergent and divergent movements. When the rising part of the convection current rises it causes the upper mantle to move upward and in a lateral direction. This causes the mantle to split and new material to rise creating new ocean crust. The downward motion of the convection current pulls the mantle crust downward at convergent boundaries. When part of the mantle crust is uplifted the weight of the lifted part, pushes the sinking mantle down, causing motion in the tectonic plates.
A convergent boundary is where two tectonic plates move towards each other. And when they collide they form either a subduction zone with its associated island arc or an...

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...ld Ocean. They are somewhat divided by the continents into the Pacific, Atlantic, Indian and Arctic. The World Ocean is 361 million km² in area, the volume is 1370 million km³, and its average depth is 3790 m.
The landmasses are divided into seven continents. They are Africa, Antarctica, Asia, Australia, North America, South America and Europe. But before there were seven it was said to be just one giant landmass called Pangaea. Supposedly this super continent began to break up about 225-200 million years ago, eventually coming into the position the continents are today.
Similar fossils of several different animals and plants that once lived on land had been found widely separated on the continents. There would be no way that these could have gotten where they were found if the continents were then as they are now.

Works cited

1.) History of Plate Tectonics
-http://www.ucmp.berkeley.edu/geology/tectonics.html

2.) Earth Structure http://volcano.und.nodak.edu/vwdocs/vwlessons/lessons/Earths_layers/Earths_layears4.html 3.) Earth Science Book
-copyright 2002 by the McGraw-Hill Companies, Inc.

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