from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Tending to push or thrust out.
- adj. Tending to protrude or project.
- adj. Derived from magma poured out or ejected at the earth's surface. Used of igneous rocks.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Jutting out; extruding.
- n. Rock which has been formed through volcanic extrusion.
from the GNU version of the Collaborative International Dictionary of English
- adj. Forced out at the surface; ; -- contrasted with
from The Century Dictionary and Cyclopedia
- 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.
- n. That which is extruded; specifically, in petrography, same as effusive (which see): contrasted with intrusive.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. of rock material; forced out while molten through cracks in the earth's surface
Sorry, no etymologies found.
If the crystallization process occurs at the Earth's surface, the rocks created are called extrusive igneous rocks.
Geologically, the Plateau is composed of Quaternary extrusive rocks, mostly rhyolite, basalt, and tuff.
Its mix of granitic, sedimentary, metamorphic, and extrusive rocks contrasts with the predominantly volcanic rocks of the Cascades (4).
The mountain ranges are a geologic mix of faulted limestone reefs, volcanoes and associated basalt, rhyolite, and tuff extrusive rocks.
It has a variety of features: several lateral craters, shield volcanoes, scoriae and lava cones, extrusive domes and huge detached rocks.
They form when magma cools and crystallizes subsurface (intrusive igneous rocks) or lava cools and crystallizes on the surface (extrusive igneous rocks).
Granite is an example of an intrusive igneous rock, whereas basalt is an extrusive igneous rock.
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.
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.
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).