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| surface rock resulting form volcanic activity |
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silica deficient rocks
50% |
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| chemical content between that of silicic and mafic. |
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| a mixture of gas and pyroclastic debris that is so dense that it hugs the ground as it flows rapidly into low areas. |
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a silicic rock
usually cream colored, tan or pink
made up of mostly feldspar but always includes some quartz |
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crystallizes from an intermediate lava
moderately gray or green color |
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| has a relatively low amount of silica (50%) |
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| refers to a rock's appearance with respect to the size, shape, and arrangement of its grains or other constituents. |
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| one in which most of the mineral grains are smaller than 1 millimeter. |
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volcanic glass
one of the few rocks that is not composed of minerals.
fine grained or glassy texture distinguishes extrusive rocks from most intrusive rocks. |
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| one in which larger crystals are enclosed in a groundmass of much finer grained minerals or obsidian. the larger crystals are termed phenocrysts. |
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| cavities in extrusive rock resulting form gas bubbles that were in lava, and the texture is called vesicular. |
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| a frothy glass with so much void space that it floates in water. |
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solid rock has been blasted apart by volcanic explosion
pyroclastic fragments are angular, not rounded |
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spindle or lens shaped pyroclast
occurs when lava is ejected into the air. |
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| rock composed of fine grained pyroclastic particles |
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| a rock that includes larger pieces of volcanic rock |
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| opening through which eruption takes place |
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| lava pours from a vent on the side of a volcano |
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| volcanic depression much larger than the original crater |
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| broad, gently sloping volcanoes constructed of solidified lava flows. |
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| a volcano constructed of pyroclastic fragments ejected from a central vent |
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| one constructed of alternating layers of pyroclastic fragments and solidified lava flows. |
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| steep sided or spine shaped masses of volcanic rock formed from viscous lava that solidifies in or immediately above a volcanic vent |
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| columnar structure or jointing |
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| individual layers may appear to be formed of parallel, vertical columns, mostly six-sided. |
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| rocks, gernerally basalt, occuring as pillow shapped, rounded masses closely fitted together. |
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