What is Mohorovicic discontinuity?
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The Mohorovicic Discontinuity, or "Moho," is the boundary between the crust and the mantle. The red line in the diagram shows its location. In geology the word "discontinuity" is used for a surface at which seismic waves change velocity. At this discontinuity, seismic waves accelerate.
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Answer:
The Mohorovicic Discontinuity, or "Moho," is the boundary between the crust and the mantle. The red line in the diagram shows its location.
In geology the word "discontinuity" is used for a surface at which seismic waves change velocity. One of these surfaces exists at an average depth of 8 kilometers beneath the ocean basin and at an average depth of about 32 kilometers beneath the continents. At this discontinuity, seismic waves accelerate. This surface is known as the Mohorovicic Discontinuity or often simply referred to as the "Moho."
How Was the Moho Discovered?
The Mohorovicic Discontinuity was discovered in 1909 by Andrija Mohorovicic, a Croatian seismologist. Mohorovicic realized that the velocity of a seismic wave is related to the density of the material that it is moving through. He interpreted the acceleration of seismic waves observed within Earth's outer shell as a compositional change within the Earth. The acceleration must be caused by a higher density material being present at depth.
The lower density material immediately beneath the surface is now commonly referred to as "Earth's crust." The higher density material below the crust became known as "Earth's mantle." Through careful density calculations, Mohorovicic determined that the basaltic oceanic crust and the granitic continental crust are underlain by a material which has a density similar to an olivine-rich rock such as peridotite.
depth of mohorovicic discontinuity
Crustal thickness map: Thickness of Earth's crust by USGS - since the Moho is at the base of the crust, this map also shows depth to Moho.
How Deep is the Moho?
The Mohorovicic Discontinuity marks the lower limit of Earth's crust. As stated above, it occurs at an average depth of about 8 kilometers beneath the ocean basins and 32 kilometers beneath continental surfaces. Mohorovicic was able to use his discovery to study thickness variations of the crust. He discovered that the oceanic crust has a relatively uniform thickness, while continental crust is thickest under mountain ranges and thinner under plains.
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