High-Res Show Crust-Mantle Boundary - Moho, Where Is Earth's Mantle?

This map shows the global Mohorovičić discontinuity, better known as Moho, based on data from the GOCE satellite.

CREDIT: GEMMA project

Beneath the Earth's crust, the outermost hard shell that makes up just 1 percent of the volume of the planet, lies a hot, viscous layer of rock called the mantle.

Together, the crust and upper portion of the mantle. called the lithosphere, are where most important geological processes occur, such as mountain-building, earthquakes and the source of volcanoes.

The slow churning and overturning of the mantle is what drives the movements of Earth's tectonic plates.

New methods of observation using satellites are helping scientists learn more about this important layer of the Earth's inner and outer layers and where it begins under different regions of the planet.

Andrija Mohorovičić
Until just a century ago, we didn’t know Earth has a crust. In 1909, Croatian seismologist Andrija Mohorovičić found that at about 50 km underground there is a sudden change in seismic speed.

Ever since, that boundary between Earth’s crust and underlying mantle has been known as the Mohorovičić discontinuity, or Moho.

Even today, almost all we know about Earth’s deep layers comes from two methods: seismic and gravimetric.

Seismic methods are based on observing changes in the propagation velocity of seismic waves between the crust and mantle.

Gravimetry looks at the gravitational effect due to the density difference caused by the changing composition of crust and mantle.

But the Moho models based on seismic or gravity data are usually limited by poor data coverage or data being only available along single profiles.

GEMMA Project

GEMMA’s Moho map is based on the inversion of homogenous well-distributed gravimetric data.

For the first time, it is possible to estimate the Moho depth worldwide with unprecedented resolution, as well as in areas where ground data are not available.

This will offer new clues for understanding the dynamics of Earth’s interior, unmasking the gravitational signal produced by unknown and irregular subsurface density distribution.

GEMMA is being carried out by Italian scientist Daniele Sampietro and is funded by the Politecnico di Milano and ESA’s Support To Science Element under the Changing Earth Science Network initiative.

This initiative supports young scientists at post-doctoral level in ESA Member States to advance our knowledge in Earth system science by exploiting the observational capacity of ESA missions

Read more at the ESA Goce website