Asthenosphere

The asthenosphere is part of earth's mantle. It is about 100 km to 350 km under the surface. It is the lower part of the upper mantle, and behaves as a hot viscous liquid.

It consists of hot, weak material that can be deformed like silly putty. That means it is capable of gradual flow. It is under the lithosphere.

 References 

Category:Structure of the Earth