Term
Andesitic Composition
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Intermediate Composition |
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Definition
| A compositional group of igneous rocks, indicating that the rock conatins at least 25 percent dark silicate minerals. The other dominant mineral is plagioclase feldspar. |
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Term
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Definition
| A texture of igneoous rocks in which the crystals are too small for individual minerals to be distinguished without the aid of a microscope. |
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Term
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Definition
| In igneous activity, the processs of incorporating country rock into a magma body. |
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Term
Basaltic composition
or
Mafic |
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Definition
| A compositional group of igneous rocks indicating that the rock contains substantial dark silicate minerals and calcium-rich plagioclase feldspar. |
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Term
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Definition
| A concept proposed by N. L. Bowen that illustrates the relationships between magma and the minerals crystallizing frtom it during the formation of igneous rocks. |
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Term
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Definition
| The formation and growth of a crystalline solid from a liquid or gas. |
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Term
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Definition
| During the crystallization of magma, the earlier-formed minerals are denser than the liquid portion and settle to the bottom of the magma chamber. |
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Term
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Definition
| Melting that occurs as rock ascend due to a drop in confining pressure. |
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Term
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Definition
| Igneous activity that occurs at Earth's surface. |
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Term
Felsic Composition
or
Granitic Composition |
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Definition
| A compositional group of igneous rocks indicating the rock is composed almost entirely of light-colored silicates. |
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Term
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Definition
| The gradual increase in in temperature with depth in the crust. The average is 30 degrees Celsius per kilometer in the upper crust. |
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Term
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Definition
| Natural glass produced when molten lava cools too rapidly to permit recrystallization. Volcanic glass is a solid composed of unordered atoms. |
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Definition
| A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals. |
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Term
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Definition
| The matrix of smaller crystals within an igneous rock that has porphyritic texture. |
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Term
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Definition
| Rock formed from the crystalization of magma. |
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Term
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Definition
| 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. |
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Term
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Definition
| Igneous rock that formed below Earth's surface. |
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Term
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Definition
| Magma that reaches Earth's surface. |
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Term
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Definition
| A body of molten rock found at depth, including any dissolved gases and crystals. |
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Term
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Definition
| The process of altering the composition of a magma through the mixing of material from another magma body. |
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Term
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Definition
| The process of generating more than on erock type from a single magma. |
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Term
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Definition
| The liquid portion of magma excluding the solid crystals. |
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Term
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Definition
| The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occurred, a melt with a higher silica content results. |
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Term
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Definition
| A very carse-grained igneous rock (typically granite) commonly found as a dike associated with a large mass of plutonic rock that has smaller crystals. Crystallization in a water-rich environment is believed to be responsible for the very large crystals. |
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Term
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Definition
| A texture of igneous rocks in which the interlocking crystals are all larger than one centimeter in diameter. |
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Term
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Definition
| An igneous rock texture in which the crystals are roughly equal in size and large enough so the individual minerals can be identified without the aid of a microscope. |
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Term
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Definition
| Conspicuously large crystal embedded in a matrix of finer-grained crystals. |
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Term
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Definition
| Igneous rock that form at depth. After Pluto, the god fo the lower world in classical mythology. |
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Definition
| An igneous rock texture characterized by two distinctively differetn crystal sizes. The larger crystals are called phenocrysts, whereas the matrix of smaller crystals is termed the groundmass. |
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Term
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Definition
| An igneous rock with a porphyritic texture. |
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Term
Pyroclastic texture
or
Fragmental texture |
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Definition
| An igneous rock texture resulting from the consolidation of individual rock fragments that are ejected during a violent volcanic eruption. |
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Term
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Definition
| The size, shape, and distribution of the particles that collectively constitute a rock. |
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Term
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Definition
| A compositional group of igneous rocks containing mostly olivine and pyroxene. |
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Term
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Definition
| A term applied to aphanitic igneous rocks that contain many small cavaties called vesicles. |
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Term
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Definition
| Gaseous components of magma dissolved in the melt. Volatiles will readily vaporize (form a gas) at surface pressures. |
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Term
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Definition
| Pertaining to the activites, structures, or rock types of a volcano. |
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