Hey there! 1. Asthenosphere. 2.Lower Mantle. The asthenosphere the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur. The lower mantle A large fraction of Earth's interior, from a depth of about 650 km (400 miles) down to 2,900 km (1,800 miles), consists of the lower mantle, which is composed chiefly of magnesium- and iron-bearing silicates, including the high-pressure equivalents of olivine and pyroxene.
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