The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiated by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core. Earth's mantle is a rocky shell about 2,890 km (1,800 mi) thick[1] that constitutes about 84 percent of Earth's volume.[2] It is predominantly solid and encloses the iron-rich hot core, which occupies about 15 percent of Earth's volume.[2][3] Past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface, upon which we live.[4] The gases evolved during the melting of Earth's mantle have a large effect on the composition and abundance of Earth's atmosphere.[citation needed] Information about structure and composition of the mantle either result from geophysical investigation or from direct geoscientific analyses on Earth mantle derived xenoliths.
Two main zones are distinguished in the upper mantle: the inner asthenosphere composed of flowing rock in the state of plasticity, about 200 km thick,[5] and the lowermost part of the lithosphere, composed of rigid rock, about 50 to 120 km thick.[6] A thin crust, the upper part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick.
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