Lehmann discontinuity

The Lehmann discontinuity (often also L-discontinuity , after its discoverer, the Danish geodesist and seismologist Inge Lehmann ) describes a region within the upper mantle in which the seismic speeds of the rock or its gradients change rapidly.

The Lehmann discontinuity was observed at various depths between 190 and 250 km with a global mean around 210 km. There are different opinions about its nature, i.e. the exact cause of the increase in speed: one assumes a mechanical boundary layer, which is associated with a change in the seismic anisotropy , while another viewpoints the L-discontinuity as the lower limit of the asthenosphere .

In some literature the term “Lehmann discontinuity” is also used for the boundary between the inner and outer core of the earth , since the inner core was also discovered by Inge Lehmann. Although this was the far more important discovery by Lehmann, the term has generally gained acceptance for the discontinuity of the upper mantle.