Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Oceanic Crust

  • Nicholas Arndt
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1100-4

Definition

Oceanic crust is the outer layer of the solid Earth beneath the oceans. This type of crust is 6–9 km thick and comprises three main layers (from top to bottom): Layer 1, a thin layer (typically less than 500 m thick) of deep-water unconsolidated carbonate or siliceous sediment that thin towards mid-ocean ridges; Layer 2A consisting of ~0.5 km thick, glassy-to-finely crystalline basalt, usually in the form of pillow basalt; Layer 2B, consisting of ~1.5 km thick sheeted vertical diabase dykes; Layer 3, ~5 km thick and of a density of 3.0 g cm−3 consists of gabbro (the intrusive form of basalt) and ultramafic cumulates. The crust forms through partial melting of upwelling mantle beneath mid-ocean spreading centers; the layering results from differentiation of the basaltic magma produced by this melting. On Earth, the age of oceanic crust ranges from zero at spreading centers to a maximum of about 180 Ma in the northwestern Pacific.

See Also

Keywords

Bioorganic Chemistry Outer Layer Partial Melting Oceanic Crust Plate Tectonic 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Maison des GéosciencesLGCA, Université J. FourierSt-Martin d’HèresFrance