What is Earths Mantle?

Answer 1

Earth's mantle is the thick shell of dense rock surrounding the liquid metallic Earth's outer core, and lies directly beneath the Earth's thin crust. The term is also applied to the rocky shell surrounding the cores of other planets. Earth's mantle lies roughly between 30 and 2,900 km below the surface, and occupies about 70% of Earth's volume.

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http://en.wikipedia.org/wiki/Earth's_mantle

Answer 2

Earth's mantle is the thick shell of dense rock surrounding the liquid metallic Earth's outer core, and lies directly beneath the Earth's thin crust. The term is also applied to the rocky shell surrounding the cores of other planets. Earth's mantle lies roughly between 30 and 2,900 km below the surface, and occupies about 70% of Earth's volume.

The boundary between the crust and the mantle is the Mohorovičić discontinuity, named for its discoverer, and is usually called the Moho. The Seismic Moho is a boundary at which there is a sudden change in the speed of seismic waves, which can be detected by sensitive instruments at Earth's surface. At one time some people thought that the Moho was the structure along which the Earth's rigid crust moved relative to the mantle. Current research considers the motion of the crust associated with plate tectonics as the surface manifestation of a much deeper mantle circulation. The uppermost mantle just below the crust is composed of relatively cold and therefore strong material. This strong layer of mantle and the crust forms the lithosphere, and cools mainly by convection.

The mantle differs substantially from the crust in its mechanical characteristics and its chemical composition. The distinction between crust and mantle is based on chemistry, rock types, and seismic characteristics. The crust is, in fact, primarily a product of mantle melting. Typical mantle rocks have a higher portion of iron and magnesium, a higher magnesium to iron ratio, and a smaller portion of silicon and aluminium than the crust.

Mantle rock above about 400 km depth consists mostly of olivine, pyroxenes, spinel, and garnet: typical rock types are peridotite, dunite (olivine-rich peridotite), and eclogite. Between about 400 km and 650 km depth, olivine is not stable and is replaced by polymorphs with approximately the same composition: one polymorph is wadsleyite, and the other is ringwoodite (a mineral with the spinel structure). Below about 650 km, none of the minerals of the upper mantle is stable; the most abundant minerals present have structures (but not compositions) like that of the mineral, perovskite. The changes in mineralogy at about 400 and 650 km yield distinctive signatures in seismic records of the Earth's interior. The changes in mineralogy with depth have been investigated by laboratory experiments that duplicate high mantle pressures, such as those using the diamond anvil. These changes in mineralogy may influence mantle convection, as they result in density changes and they may absorb or release heat during phase transitions in convecting mantle.

In the mantle, temperatures range between 100°C at the upper boundary to over 4,000°C at the boundary with the core. Although these temperatures far exceed the melting points of the mantle rocks at the surface, particularly in deeper ranges, they are almost exclusively solid. The enormous lithostatic pressure exerted on the mantle prevents them from melting.

Answer 3

The layer between the crust and the inner core of the earth

Answer 4

earth is considered tobe made up pf
1.the core-the innermost part
2.the mantle -the middle part and
3.the crust the outermost part