Its delicately balanced pressure and temperature results in most of its material being near its melting point, allowing for flow and movement responsible for volcanic activity.
Located from 70 to 200 kilometers beneath the earth's surface and as much as 600 kilometers thick in some places, seismic velocities are distinctly lower in this layer than in adjacent parts of the Earth's layers. Its delicately balanced pressure and temperature results in most of its material being near its melting point, allowing for flow and movement responsible for volcanic activity. FTP, name this upper layer of the mantle, also called the "low velocity zone".
Located from 70 to 200 kilometers beneath the earth's surface and as much as 600 kilometers thick in some places, seismic velocities are distinctly lower in this layer than in adjacent parts of the Earth's layers.
asthenosphere (prompt on mantle; accept low velocity zone until mentioned)