Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Derived from magma poured out or ejected at the earth's surface. Used of igneous rocks.

from The Century Dictionary.

  • Capable of being extruded or thrust out; that tends or serves to extrude or thrust out or forth; specifically, in petrography, erupted or extruded: applied to igneous rocks. Same as effusive.
  • noun That which is extruded; specifically, in petrography, same as effusive (which see): contrasted with intrusive.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective (Geol.) Forced out at the surface; ; -- contrasted with intrusive.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective Jutting out; extruding.
  • noun geology Rock which has been formed through volcanic extrusion.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective of rock material; forced out while molten through cracks in the earth's surface

Etymologies

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Examples

  • If the crystallization process occurs at the Earth's surface, the rocks created are called extrusive igneous rocks.

    Rock cycle 2007

  • Geologically, the Plateau is composed of Quaternary extrusive rocks, mostly rhyolite, basalt, and tuff.

    Ecoregions of Wyoming (EPA) 2009

  • The mountain ranges are a geologic mix of faulted limestone reefs, volcanoes and associated basalt, rhyolite, and tuff extrusive rocks.

    Ecoregions of Texas (EPA) 2009

  • Its mix of granitic, sedimentary, metamorphic, and extrusive rocks contrasts with the predominantly volcanic rocks of the Cascades (4).

    Ecoregions of Oregon (EPA) 2009

  • The islands are of volcanic origin associated with crustal rifting with basic intrusive and acid extrusive igneous rock overlying Cretaceous sandstones and surrounded by limestones and alluvial plains.

    Islands and Protected Areas of the Gulf of California, Mexico 2008

  • Besides the dyke swarms, the northern section is composed mainly of serpentinised peridotite and gabbro masses, although there are small areas of extrusive volcanic rocks.

    MacQuarie Island, Australia 2008

  • It has a variety of features: several lateral craters, shield volcanoes, scoriae and lava cones, extrusive domes and huge detached rocks.

    Volcanoes of Kamchatka, Russian Federation 2008

  • Figure 1f shows another puzzling inclusion type found in quartz from intrusive and extrusive units of the Pine Grove system of Utah (Keith et al. 1986).

    Evidence for Fluid Saturation and Degassing 2008

  • They form when magma cools and crystallizes subsurface (intrusive igneous rocks) or lava cools and crystallizes on the surface (extrusive igneous rocks).

    AP Environmental Science Chapter 3- The Solid Earth 2008

  • Granite is an example of an intrusive igneous rock, whereas basalt is an extrusive igneous rock.

    AP Environmental Science Chapter 3- The Solid Earth 2008

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