crust spreading

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• Seafloor spreading — Age of oceanic crust; youngest (red) is along spreading centers. Seafloor spreading is a process that occurs at mid ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor… …   Wikipedia

• Oceanic crust — Age of oceanic crust. The red is most recent, and blue is the oldest. Oceanic crust is the part of Earth s lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and… …   Wikipedia

• seafloor spreading hypothesis — ▪ Earth science       theory that oceanic (oceanic ridge) crust forms along submarine mountain zones, known collectively as the midocean ridge system, and spreads out laterally away from them. This idea played a pivotal role in the development of …   Universalium

• sea-floor spreading — noun (geology) The process by which new oceanic crust is generated at oceanic ridges by the convective upswelling of magma • • • Main Entry: ↑sea * * * sea floor spreading «SEE FLR, FLOHR», the process by which the sea floor is being continuously …   Useful english dictionary

• seafloor spreading — Theory that oceanic crust forms along submarine mountain zones, known collectively as the oceanic ridge system, and spreads out laterally away from them. This idea, proposed by U.S. geophysicist Harry H. Hess (1906–1969) in 1960, was pivotal in… …   Universalium

• sea-floor spreading —   the widening of an ocean basin by the creation of new crust at a divergent margin …   Geography glossary

• seafloor spreading — ˈ ̷ ̷ ˌ ̷ ̷ noun : the divergence at midocean ridges of the tectonic plates underlying the oceans that is due to upwelling from the earth s interior of magma which forms new crust …   Useful english dictionary

• Plate tectonics — The tectonic plates of the world were mapped in the second half of the 20th century …   Wikipedia

• plate tectonics — plate tectonic, adj. Geol. a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past… …   Universalium

• Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry       The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… …   Universalium

• North America — North American. the northern continent of the Western Hemisphere, extending from Central America to the Arctic Ocean. Highest point, Mt. McKinley, 20,300 ft. (6187 m); lowest, Death Valley, 276 ft. (84 m) below sea level. 400,000,000 including… …   Universalium