Encyclopedia of Astrobiology

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

Igneous Rock

  • Nicholas Arndt
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_773-3

Synonyms

Definition

An igneous rock forms by solidification of magma. There are two main types: volcanic rocks that crystallize or solidify from erupted lava or fragmental (pyroclastic) material that reached the surface and contacted the atmo- or hydrosphere and plutonic or intrusive rocks that crystallize from magma that did not reach the surface. These two types are distinguished by their grain size: intrusive rocks are coarse-grained and typically show an interlocking fabric because they crystallize slowly in a thermally insulated setting, whereas volcanic rocks are fine-grained or even glassy because they cool rapidly following eruption at the Earth’s surface; crystals typically float in a fine-grained matrix. Common minerals in igneous rocks are olivine, pyroxene, amphibole, mica, feldspar, and quartz. Common intrusive rock types include peridotite, gabbro, granodiorite, and granite; their volcanic equivalents are komatiite, basalt, andesite, and rhyolite,...

Keywords

Grain Size Volcanic Rock Bioorganic Chemistry Rock Type Main Type 
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