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Schematic view of the interior of Earth. 1. continental crust - 2. oceanic crust - 3. upper mantle - 4. lower mantle - 5. outer core - 6. inner core - A: Mohorovičić discontinuity - B: Gutenberg Discontinuity - C: Lehmann discontinuity
Ordovician ophiolite in Gros Morne National Park, Newfoundland. This rock which formed in the Moho is exposed on the surface.

The Mohorovičić discontinuity (Croatian pronunciation: [mɔhɔːrɔvitʃitɕ] (Moh-ho-ro-vee-chich)), usually referred to as the Moho, is the boundary between the Earth's crust and the mantle. The Moho separates both oceanic crust and continental crust from underlying mantle. The Moho mostly lies entirely within the lithosphere; only beneath mid-ocean ridges does it define the lithosphere-asthenosphere boundary. The Mohorovičić discontinuity was first identified in 1909 by Andrija Mohorovičić, a Croatian seismologist, when he observed the abrupt increase in the velocity of earthquake waves (specifically P-waves) at this point.

The Mohorovičić discontinuity is on average 7 km below the ocean floor and 30 to 50 km beneath typical continents. It is deepest beneath the Tibetan Plateau, where it is approximately 75 km below the surface.

During the late 1950s and early 1960s, a proposal was taken up in the executive committee of the National Science Foundation to drill a hole through the ocean floor to reach this boundary. However the operation, named Project Mohole, never received sufficient support and was mismanaged; it was canceled by the United States Congress in 1967. Simultaneous efforts were made by the Soviet Union at the Kola Institute, which reached a depth of 12,260 meters (40,226 feet) over 15 years, the world's deepest hole to date, before that attempt was also abandoned.[1]

Reaching the discontinuity remains an important scientific objective. A more recent proposal considers a self-descending tungsten capsule heated by radiogenic heat to explore Earth’s interior near the Moho discontinuity and in the upper mantle.[2] The Japanese project Chikyu Hakken ("Earth Discovery") also aims to explore this general area.


See also





  1. ^ "How the Soviets Drilled the Deepest Hole in the World". Wired. 2008-08-25. Retrieved 2008-08-26.  
  2. ^ Ozhovan, M.; F. Gibb, P. Poluektov and E. Emets (August 2005). "Probing of the Interior Layers of the Earth with Self-Sinking Capsules". Atomic Energy 99 (2): 556–562. doi:10.1007/s10512-005-0246-y.  

External links


Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary



Alternative spellings

Proper noun


Mohorovičić discontinuity


Mohorovičić discontinuity

  1. (geology) The boundary between the Earth's crust and mantle.


See also

  • Gutenberg discontinuity


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