Asthenosphere and lithosphere

What does the mantle consist of? ASTHENOSPHERE is the lower mantle extends beyond the asthenosphere. It is in solid state. Asthenosphere is a thin semifluid layer of the earth (100-200 km thick), below the outer rigid lithosphere, forming part of the mantle and thought to be able to flow vertically and horizontally, enabling sections of lithosphere to subside, rise, and undergo lateral movement

LITHOSPHERE is the rigid layer formed from the uppermost part of the mantle and the crust together. Outermost shell of a rocky planet has in average 100 km thick. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater. There are two types of lithosphere: oceanic lithosphere, which is associated with oceanic crust and exists in the ocean basins and continental lithosphere, which is associated with continental crust.

The lithosphere is always moving, but very slowly. It is broken into huge sections called tectonic plates. The extreme heat from the mantle part of the lithosphere makes it easier for the plates to move; this is similar to how iron is bendable once it's heated. The movement of the lithosphere, called plate tectonics, is the reason behind a lot of Earth's most dramatic geologic events. When one plate moves beneath another, or when two plates rub together, they can create earthquakes and volcanoes.

Plate tectonics may explain why we have continents. Scientists believe the continents used to be one major landmass called Pangaea, which separated because the lithosphere broke apart. There is evidence to support this theory. For example, the eastern coast of South America and the western coast of Africa look like they would fit together. And even though they are separated by an ocean, similar animals and plants are found in both regions.

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The lithosphere

<== попередня сторінка	\|	наступна сторінка ==>
	\|	Continental and oceanic earth’s crust

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