Answer:
asthenosphere
Explanation:
What is being described in the question above, that is a soft weak like layer the upper part of the mantle where lithospheric plates is known as the asthenosphere. In the study of earth's mantle, the asthenosphere is one of the region that can be overlooked as it constitutes part of the upper mantle with its counterpart; lithosphere.
Some of the properties of asthenosphere is the fact it has high temperature, it is viscous and it is ductile. It is also characterized by its density.
