Question

The layer of the earth that is composed of rock, yet flows due to extreme heat and pressure, is known as the _____.

crust
upper mantle
outer core
asthenosphere

Answer 1

Earlier in the body of text you are reading, you should be able to find the fallowing passage: "Upper mantle: solid rock that flows due to plasticity."

Answer: Upper Mantle

Answer 2

It is the upper mantle.