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 (ĭk-stro͞o′sĭv, -zĭv)
Derived from magma poured out or ejected at the earth's surface. Used of igneous rocks.


1. tending to extrude
2. (Geological Science) (of igneous rocks) formed from magma issuing from volcanoes or cracks in the earth's crust; volcanic. Compare intrusive2


(ɪkˈstru sɪv, -zɪv)

1. pertaining to extrusion.
2. of or pertaining to a class of igneous rocks that have been forced out in a molten or plastic condition upon the surface of the earth.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.extrusive - of rock material; forced out while molten through cracks in the earth's surface
geology - a science that deals with the history of the earth as recorded in rocks
intrusive - of rock material; forced while molten into cracks between layers of other rock
References in periodicals archive ?
The extrusive rocks in this area include andesite, basaltic andesite, quartz trachyandesite and basalt, though the bulk of these rocks are basaltic andesites and quartz trachyandesite.
Extrusive rocks of Permian age, associated with the Elqui magmatic arc, covered the shallow marine deposits on the east side of the Arrayan pre-orogenic basin (Charrier et al.
The STGM of the Muslim Bagh ophiolite shows a nearly complete ophiolitic sequence, as defined by the Penrose conference (1972), only the uppermost unit consisting of extrusive rocks and related sediments is missing (Fig.
In the area between Vohemar and Andapa, extrusive rocks form a long, thin belt parallel to the oceanic coast (see Figure 1).
The term was used initially to designate serpentinite and later on, a suite of mafic and ultramafic intrusive rocks (ultramafic rocks, gabbro, and diabase) and volcanic extrusive rocks (Brongniart 1821).