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Earth's mantle

part of the interior of the planet Earth
(Redirected from Mantle (geology))
Earth cutaway

Earth's mantle is the 1,800 mile (2,900 km) thick shell making up about 84% of Earth's volume.[1] It is over the Earth's iron-rich core, which takes up about 15% of Earth's volume.[1]

The upper mantleEdit

Past episodes of melting and volcanism at the outer levels of the mantle have produced a very thin crust of crystallized melt products near the surface, where we live. The gases evolved during the melting of Earth's mantle have a large effect on the composition and size of Earth's atmosphere.

Uppermost mantleEdit

A thin crust, the lower part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick.[2] There are two main zones in the upper mantle. The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, an irregular layer with a maximum thickness of perhaps 200 km, of which the uppermost mantle is 120 to 50 km thick.[3]

AsthenosphereEdit

Below the lithosphere the upper mantle becomes notably more plastic. It is called the asthenosphere, and is composed of flowing rock in the state of plasticity, about 200 km thick.[4]

Lower mantleEdit

The lower mantle is much thicker than the upper mantle. It is made of magma, under great pressure, and so is thicker (higher viscosity) and flows less easily. The lower mantles temperature has a max of about 4,000 °C (7,000 °F).

The chemical composition of the mantle is heavily biased towards three elements: oxygen 44.8% by weight; magnesium 22.8%; silicon 21.5%. Compounds are oxides: silica SiO2 46%; magnesium oxide MgO 37.8%.

Place with no crustEdit

In 2007 a team of scientists on board the RRS James Cook went to an area of the Atlantic seafloor where the mantle has no crust covering. The anomaly is mid-way between the Cape Verde Islands and the Caribbean in the Atlantic Ocean, at or near the Mid-Atlantic Ridge. It is about three kilometres under the ocean surface and covers thousands of square kilometres.[5][6]

Other such 'Oceanic Core Complexes' (OCCs) were found later.[7] Many have active hydrothermal vents.

Other websitesEdit

ReferencesEdit

  1. 1.0 1.1 Robertson, Eugene (2007). "The interior of the earth". USGS. Retrieved 2009-01-06.
  2. Crust: Schlumberger Oilfield Glossary
  3. Lithosphere: Schlumberger Oilfield Glossary
  4. Asthenosphere: Schlumberger Oilfield Glossary
  5. "Distance and location". www.msnbc.msn.com. Retrieved 2008-06-19.
  6. "About the Mantle". www.sciencedaily.com. Retrieved 2008-06-19.
  7. Roger Searle 2009. Planet Earth online