Mohorovičić discontinuity
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The Mohorovičić (IPA: [mɔhɔ'ɹɔvɪtʃɪtʃ]) discontinuity, usually referred to as the Moho, is the boundary between the Earth's crust and the mantle. The Moho serves to separate both oceanic crust and continental crust from underlying mantle. The Moho mostly lies entirely within the lithosphere; only beneath mid-ocean ridges does the Moho also define the mesosphere-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. Ophiolites are sections of oceanic crust and possible mantle rock that have been obducted into the continental crust during plate collisions.
The interior Earth location of the Mohorovičić discontinuity varies between about 5 km beneath the mid-ocean ridges to approximately 75 km beneath continental crust.
During the late 1950s and early 1960s, there was a proposal 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 the proposal was canceled by US Congress in 1967. This remains as an important scientific objective, which is being addressed by scientific drilling.
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[edit] Moho in popular culture
The Mohorovičić Discontinuity is mentioned in one particular computer game, an RTS called "Total Annihilation." Players can build a "Moho Mine" in order to mine metal at or close to the Mohorovičić Discontinuity. Due to the size of the structure, the public being unfamiliar with the Mohorovicic Discontinuity, and an expansion structure called the "Moho Metal-Maker", "Moho" is misinterpreted as meaning "big."
The Mohorovičić Discontinuity is also mentioned in the novel 'Abduction' by Robin Cook, in which a team of scientists are abducted by inhabitants of an underground civilization.
In the cartoon "Inhumanoids" the monster, D-Compose's kingdom of Skellweb lies within the Moho.
In Star Control 3, one of the "ramblings" of the odd Mycon race is referring to the Deep Children as "Dwellers of the Mohorovicic." This is a reference to the fact that a "deep child" will burrow deep into the surface of a planet to begin terraforming
Deep Storm: A Novel by Lincoln Child details an expedition where a team of scientists attempts to drill through the ocean floor to the Mohorovicic Discontinuity.
In the Mars trilogy by Kim Stanley Robinson, the colonizers of Mars dig deep "moholes" to allow outgassing from the planet's interior as a means to increase the atmospheric pressure - thus contributing to the terraforming of the planet.
Also, in Sid Meier's Alpha Centauri game, the Mohorovicic Discontinuity is mentioned with the technology advance "Industrial Automation."
[edit] See also
- Gutenberg Discontinuity
- Lehmann discontinuity
- Brittle-ductile transition zone
- Kola Superdeep Borehole
[edit] References
- Harris, P., 1972, 'The composition of the earth', in Gass, I.G., Smith, P.J., and Wilson, R.C.L. (eds), Understanding the Earth: A Reader in the Earth Sciences. The Open University Press.
- Schlumberger Oilfield Glossary
Douglas Dixon, P., 2000, "Beginners Guide To Geology" Chancellor Press.
