The weak or "soft" zone in the upper mantle just below the lithosphere, involved in plate movement and isostatic adjustments. It lies 70 to 100 km below the surface and may extend to a depth of 400 km. Corresponds to the seismic low-velocity zone
Iowa State University, College of Liberal Arts and Sciences, Department of Geological and Atmospheric Sciences, Glossary of Geologic Terms (based on the glossary in Earth: An Introduction to Geologic Change, by S. Judson and S.M. Richardson, Englewood Cliffs, NJ, Prentice Hall, 1995), Iowa, USA 2004. http://www.ge-at.iastate.edu/courses/Geol_100/old_ files/glossary.v2.html, (ND/ Geol - Amer) {111}