(See related pages)
Below you will find key words and concepts that you should remember from this chapter.
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| andesite | Fine-grained igneous rock of intermediate composition. Up to half of the rock is plagioclase feldspar with the rest being ferromagnesian minerals. (See page(s) 253) |
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| basalt | A fine-grained, mafic, igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar. (See page(s) 253) |
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| block | Large angular pyroclast. (See page(s) 255) |
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| bomb | Large spindle- or lens-shaped pyroclast. (See page(s) 255) |
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| caldera | A volcanic depression much larger than the original crater. (See page(s) 255) |
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| cinder cone | A volcano constructed of loose rock fragments ejected from a central vent. (See page(s) 258) |
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| circum-Pacific belt | Major belt around the edge of the Pacific Ocean on which most composite volcanoes are located and where many earthquakes occur. (See page(s) 261) |
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| columnar structure (columnar jointing) | Volcanic rock in parallel, usually vertical columns, mostly six-sided; also called columnar jointing. (See page(s) 266) |
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| composite volcano (stratovolcano) | A volcano constructed of alternating layers of pyroclastics and rock solidified from lava flows. (See page(s) 260) |
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| crater | A basinlike depression over a vent at the summit of a volcanic cone. (See page(s) 255) |
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| extrusive rock | Any igneous rock that forms at Earth’s surface, whether it solidifies directly from a lava flow or is pyroclastic. (See page(s) 244) |
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| fine-grained rock | A rock in which most of the mineral grains are less than one millimeter across. (See page(s) 253) |
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| flank eruption | An eruption in which lava erupts out of a vent on the side of a volcano. (See page(s) 255) |
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| intermediate rock | Rock with a chemical content between felsic and mafic compositions. (See page(s) 250) |
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| lava | Magma on Earth’s surface. (See page(s) 244) |
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| mafic rock | Silica-deficient igneous rock with a relatively high content of magnesium, iron, and calcium. (See page(s) 250) |
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| magma | Molten rock, usually mostly silica. The liquid may contain dissolved gases as well as some solid minerals. (See page(s) 244) |
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| Mediterranean belt | A major concentration of earthquakes and composite volcanoes that runs through the Mediterranean Sea, crosses the Mideast and the Himalaya, and passes through the East Indies. (See page(s) 261) |
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| obsidian | Volcanic glass. (See page(s) 253) |
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| phenocryst | Any of the large crystals in porphyritic igneous rock. (See page(s) 253) |
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| pillow structure (pillow basalts) | Rocks, generally basalt, formed in pillow shaped masses fitting closely together; caused by underwater lava flows. (See page(s) 266) |
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| plateau basalts | Layers of basalt flows that have built up to great thicknesses. (See page(s) 265) |
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| porphyritic rock | An igneous rock in which large crystals are enclosed in a matrix (or ground mass) of much finer-grained minerals or obsidian. (See page(s) 253) |
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| pumice | A frothy volcanic glass. (See page(s) 254) |
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| pyroclastic flow | Turbulent mixture of pyroclastics and gases flowing down the flank of a volcano. (See page(s) 244) |
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| pyroclast | Fragment of rock formed by volcanic explosion. (See page(s) 251) |
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| rhyolite | A fine-grained, felsic, igneous rock made up mostly of feldspar and quartz. (See page(s) 253) |
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| shield volcano | Broad, gently sloping cone constructed of solidified lava flows. (See page(s) 256) |
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| silicic (felsic) rock | Silica-rich igneous rock or magma with a relatively high content of potassium and sodium. (See page(s) 250) |
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| tuff | A rock formed from fine-grained pyroclastic particles (ash and dust). (See page(s) 255) |
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| vent | The opening in Earth’s surface through which a volcanic eruption takes place. (See page(s) 255) |
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| vesicle | A cavity in volcanic rock caused by gas in a lava. (See page(s) 254) |
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| viscosity | Resistance to flow. (See page(s) 250) |
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| volcanic breccia | Rock formed from large pieces of volcanic rock (cinders, blocks, bombs). (See page(s) 255) |
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| volcanic dome | A steep-sided, dome- or spine-shaped mass of volcanic rock formed from viscous lava that solidifies in or immediately above a volcanic vent. (See page(s) 263) |
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| volcanism | Volcanic activity, including the eruption of lava and rock fragments and gas explosions. (See page(s) 244) |
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| volcano | A hill or mountain constructed by the extrusion of lava or rock fragments from a vent. (See page(s) 244) |
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| lava flows | river or sheet-like extrusions of lava on Earth's surface. (See page(s) 244) |
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| texture | the size, shape, and arrangement of mineral or other constituent grains in a rock. (See page(s) 253) |