Mohorovicic Discontinuity

Moho

 or Mohorovicic discontinuity

Boundary between the Earth's crust and its mantle. The Moho lies at a depth of about 22 mi (35 km) below continents and about 4.5 mi (7 km) beneath the oceanic crust. Modern instruments have determined that the velocity of seismic waves increases rapidly at this boundary. The Moho was named for Andrija Mohorovicic.

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Mohorovičić discontinuity [‚mō·hō′rō·və‚chich dis‚känt·ən′ü·əd·ē]

(geophysics)

A seismic discontinuity that separates the earth's crust from the subjacent mantle, inferred from travel time curves indicating that seismic waves undergo a sudden increase in velocity. Also known as Moho.

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Mohorovičić Discontinuity 

(also “Moho,” M-discontinuity), the boundary surface between the earth’s crust and mantle. The existence of the Mohorovičić discontinuity has been determined from seismic data; the velocity of longitudinal seismic waves passing downward through the Mohorovičić discontinuity jumps from 6.7–7.6 to 7.9–8.2 km/sec, and that of transverse waves jumps from 3.6–4.2 to 4.4—4.7 km/sec. Various geophysical, geological, and other data seem to indicate that the earth’s density at the discontinuity also increases substantially, from 2.9–3 to 3.1–3.5 t/m³. It is virtually certain that the Mohorovičić discontinuity separates strata of different chemical composition. The Mohorovičić discontinuity was named after A. Mohorovičić, who discovered it.