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23 Cards in this Set
- Front
- Back
Obsidian
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A usually black, glassy, non-crystalline igneous rock. It is felsic to intermediate in composition.
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Lahar
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A volcanic mudslide that happens when a volcano erupts pyroclastic material which melts ice on the volcano which creates mud.
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Intrusive
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An igneous rock created below the surface of the earth. They have larger crystals (1mm-10+mm in diameter) than extrusive rocks.
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Extrusive
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An igneous rock that formed above the surface of the earth. It has smaller crystals (no crystals-1mm in diameter) than intrusive rocks.
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Aphanitic
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An igneous rock that has crystals less than 1mm in diameter.
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Vesicular
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An igneous rock containing small cavities (vesicles) which form when gases expand during the cooling process and then escape the lava.
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Tephra
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Ash: Less than 2 mm diameter
Lapilli: 2 - 64 mm diamter Bocks/Bombs: 64+ mm diameter |
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Shield Cone
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A broad, gently sloping volcano that erupts mafic lava with a high viscosity that solidifies and forms the "shield."
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Gabbro
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An intrusive, phaneritic, mafic igneous rock.
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Felsic
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An igneous rock high in aluminum, potassium, silicon, and sodium. It is composed of melted crust.
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Diorite
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An intrusive, intermediate, phaneritic igneous rock made primarily of plagioclase feldspar
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Composite Cone
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Also known as a stratovolcano, it is made of tephra and lava.
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Cinder Cone
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A relatively small volcano made primarily of pyroclastic materials ejected from a single cone. They are steep-sided and erupt only tephra.
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Mafic
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An igneous rock that is low in silicon but high in calcium, iron, and magnesium. It is made of melted mantle and is found at divergent boundaries as well hot spots.
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Caldera
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A large depression typically caused by collapse or ejection of the summit area of a volcano.
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Andesite
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An intermediate, aphanitic, extrusive igneous rock.
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Rhyolite
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An extrusive, aphanitic, felsic igneous rock. It forms a highly viscous lava.
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Pyroclastic Flow
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A mixture of superheated gases and tephra and boulders. Temperatures within the cloud can reach several hundred degrees.
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Scoria
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A vesicular, extrusive, aphanitic mafic igneous rock. It is dark in color.
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Pumice
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A felsic to intermediate, extrusive, vesicular, glassy, non-crystalline igneous rock.
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Granite
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A light colored, intrusive, phaneritic, felsic igneous rock.
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Porphyry
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A texture of an igneous rock where large crystals are embedded in a matrix of smaller crystals.
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Phaneritic
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An igneous rock containing crystals between 1 and 10 mm.
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