The Gutenberg Discontinuity: Melt at the Lithosphere-Asthenosphere Boundary

Abstract

The Thin Melt Line Pronounced and persistent variations in the speed of seismic waves as they travel through Earth's interior imply the presence of a physical or chemical boundary layer. Near the lithosphere-asthenosphere boundary, these seismic discontinuities are often patchy and their origins are disputed. By analyzing a set of short-period seismic waves across the Pacific Ocean, Schmerr (p. 1480 ; see the Perspective by Kawakatsu ) relates the intermittency of this seismic discontinuity to a layer of partial melt below the oceanic lithosphere. The melt may arise from a number of geodynamic processes, including upwellings from the mantle at hot spots like Hawaii, or small-scale thermal convection in the mantle.