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


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


Bioorganic Chemistry Outer Layer Partial Melting Oceanic Crust Plate Tectonic 
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© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

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