What is the name of the seismic discontinuity separating Earth’s mantle from its outer core?

The Gutenberg discontinuity is the seismic boundary separating Earth’s mantle from its outer core.

It lies at a depth of about 2,900 kilometres beneath Earth’s surface. At this boundary, solid silicate mantle gives way to the liquid iron-rich outer core, creating a sharp change in density and seismic-wave behavior.

Primary waves, or P-waves, pass through both solids and liquids but slow and refract at the boundary. Secondary waves, or S-waves, cannot travel through liquid, so their disappearance beyond the outer core helped establish that the outer core is liquid.

The discontinuity is named for Beno Gutenberg, a German-American seismologist who helped map Earth’s deep interior. It differs from the Mohorovičić discontinuity, or Moho, which separates the crust from the mantle, and the Lehmann discontinuity, associated with the inner-core boundary.