What is the name of the seismic discontinuity between Earth's crust and mantle?

The seismic discontinuity between Earth’s crust and mantle is the Mohorovičić discontinuity, commonly shortened to the Moho. It marks a sharp increase in seismic-wave velocity caused by the change from crustal rocks to denser, compositionally different mantle rocks.

Croatian seismologist Andrija Mohorovičić identified the boundary in 1909 while studying records from an earthquake near Zagreb. He noticed that some seismic waves arrived by a direct path while others arrived later after being refracted through a faster layer below the crust. This showed that Earth has a layered interior.

The Moho is not at one fixed depth. It typically lies about 5–15 kilometres below the ocean floor and roughly 20–50 kilometres beneath continents, with greater depths beneath major mountain ranges. The global average is often given as about 35 kilometres.

The other options are real seismic boundaries but refer to different transitions: the Conrad discontinuity is within the continental crust, the Gutenberg discontinuity separates mantle and outer core, and the Lehmann discontinuity is associated with the inner core boundary.