What is Oceanic crust?
[[Image:Earth_seafloor_crust_age_1996_-_2.png|thumb|300px|Age of oceanic crust]] The '''oceanic crust''' is the part of Earth's [[lithosphere]] that is under the [[ocean]] basins. Oceanic crust is primarily composed of [[mafic]] rocks, or [[Sima (geology)|sima]] which is named for its [[magnesium]] [[silicate mineral]]<nowiki/>s. It is thinner than continental crust, and is about 7-10 kilometers thick, however it is more dense, having a mean [[density]] of about 3.3 [[gram|g]]/[[centimeter|cm]]<sup>3</sup>. Oceanic crust generally does not last longer than 200 million years. In the [[rock cycle]], it is continuously created at oceanic ridges. At these ridges, hot [[magma]] rises into the crust and cools, pushing the crust apart at the ridge. The continuous formation of new oceanic crust pushes the older crust away from the mid-ocean ridge. As it moves away from the ridge, the crust becomes cooler and denser, while the sediment may build on top of it. ==Related pages== *[[Continental crust]] ==References== {{reflist}} ==Sources== *Marshak, Stephen. (2005) Earth: Portrait of a Planet (41-87) == Other websites == *[http://volcano.und.edu/vwdocs/vwlessons/plate_tectonics/part9.html Testing the Sea-Floor Spreading Hypothesis] {{Webarchive|url=https://web.archive.org/web/20071023090129/http://volcano.und.edu/vwdocs/vwlessons/plate_tectonics/part9.html |date=2007-10-23 }} [[Category:Geology]] {{science-stub}}