What is the Mohorovicic discontinuity?

The Mohorovičić discontinuity, or Moho, is the boundary that separates the Earth's crust from the underlying mantle. It was discovered in 1909 by Croatian seismologist Andrija Mohorovičić through the observation of seismic wave velocity changes. The depth of this boundary varies, sitting much closer to the ocean floor than beneath continental crusts.

What we know

• The Mohorovičić discontinuity is the boundary between the Earth's crust and the mantle. [1, 2]
• The boundary is defined by a distinct change in the velocity of seismic waves passing through rocks of changing densities. [2]
• The Moho lies 5 to 10 kilometres below the ocean floor and 20 to 90 kilometres beneath typical continental crusts. [2]
• The discontinuity was first identified in 1909 by Andrija Mohorovičić when observing seismograms from shallow-focus earthquakes. [2]

Where to go next

• whoWho was Andrija Mohorovičić?
• how we knowHow do seismic waves reveal Earth's internal structure?
• compared withWhat is the Gutenberg discontinuity?
• the bigger pictureWhat is the Earth's lithosphere?
• a case in pointHow does oceanic crust differ from continental crust?
• an unexpected connectionHow does plagioclase connect to planetary crusts?Plagioclase is a major constituent mineral of Earth's crust, and analysis indicates it is also found on the Moon's highlands and as the most abundant mineral in the crust of Mars.

Sources

• [1]Mohorovičić discontinuity (Wikidata Q194259) · CC0 1.0
• [2]Mohorovičić discontinuity · CC BY-SA 4.0
• [3]Andrija Mohorovičić · CC BY-SA 4.0
• [4]Plagioclase · CC BY-SA 4.0
• [5]Gutenberg discontinuity · CC BY-SA 4.0