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30 Cards in this Set

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A compositional group of igneous rocks, indicating that the rock contains at least 25 percetn dark silicate minerals. The other dominant minteral is plagioclase feldspar.
Andesitic or intermediate composition
The formation or growth of a crystalline solid from a liquid or gas.
Crystallization
A compositional group of igneous rocks indicating the rock is composed almost entirely of light-colored silicates
Felsic or granitic composition
The matrix of smaller crystals within an igneous rock that has prohyritic texture
Groundmass
Magma that reaches earth's surface
Lava
The liquid portion of magma excluding the solid crystals
Melt
Conspicuously large crystal embedded in a matrix of finer-grained crystals.
Phenocryst
A compositional group of igneous rocks containing mostly olivine and pyroxene.
Ultramafic composition
A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished without the aid of a microscope.
Aphanitic Texture
During the crystallization of magma, the earlier-formed minerals are denser than the liquid portion oand settle to the bottom of the magma chamber.
Crystal settling
An igneous rock texture resulting from the consolidation of individual rock fragments that are ejected during a violent volcanic eruption.
Pyroclastic texture
A highly heated mixture, largely of ash and pumice fragments, traveling down the flanks of a volcano or along the surface of the ground.
Pyroclastic flow
A compositional group of igneous rocks indicating that the rock contains substantial dark silicate minterals and calcium-rich plagioclase feldspar.
Mafic or Basaltic composition
The process by which most igneous rocks melt.
Partial melting
Igneous rocks that form at depth. Named after the god of the lower world in classical mythology
Plutonic rock
A term applied to aphanitic igneous rocks that contain many snmall cavities called vesicles.
Vesicular texture
Pertaining to the activities, structures, or rock types of a volcano.
Volcanic
Gaseous components of magma dissolved in the melt. Will readily vaporize at surface temperature.
Volatiles
An igneous rock texture characterized by two distinctively different crystal sizes. The larger crystals are called phenocrysts, whereas the matrix of smaller crystals is termed the groundmass.
Porphyritic Texture
An igneous rock with a porphyritic texture.
Porphyry
A body of molten rock found at depth, including any dissolved gases and crystals.
Magma
The process of altering the composition of a magma through the mixing of material from another magma body.
Magma mixing
The process of generating more than one rock type from a single magma.
Magmatic differentiation
A compositional group of igneous rocks, indicating that the rock contains at least 25 percent dark silicate minerals. The other dominant mineral is plagioclase feldspar.
Intermediate composition
Igneous rock that formed below Earth's surface
Intrusive rock
A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals.
Glassy
Natural glass produced when molten lava cools too rapidly to permit recrystallization. Solid composed of unordered atoms.
Glass (volcanic)
Igneous activity that occurs at Earth's surface
Extrusive
A concept that illustrates the relationships between magma and the minerals crystallizing from it during the formation of igneous rocks.
Bowen's reaction series
In igneous activity, the process of incorporating country rock into a magma body.
Assimilation