Answer – The asthenosphere is the layer of the Earth directly under the lithosphere. It experiences relatively high temperature and pressure, and thus the rock in this layer is more malleable than that of the lithosphere.

Explanation:

The word ‘asthenosphere’ is derived from the Greek asthenis, which means weak. This is a reference to the nature of the rock material that comprises this layer. 

The lithosphere is the outermost layer of the Earth, formed by the crust and the uppermost section of the mantle. It is solid and cool. The asthenosphere lies directly under the lithosphere, ranging from about 100 km below the Earth’s surface to approximately 700 km. 

Being closer to the molten core, it is at a higher temperature (approximately 2,372°F and above) than the lithosphere above. The latter also exerts a certain amount of pressure on it. Both of these variables together make the rock in this region softer, more malleable, and in some areas, molten, producing magma. Altogether it is a more fluid layer than the lithosphere.

This semi-molten state of the asthenosphere has an important role to play in the tectonic plate theory. According to it, the lithosphere is divided into several plates that experience movement toward, against and away from each other. This motion is attributed to the fluid nature of the asthenosphere, on which these plates rest. Convection currents arise easily in the asthenosphere from variations in temperature and pressure, and this in turn produces movement in the plates above it.

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