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Rock (Definition)
A consolidated aggregate of one or more minerals.
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3 Basic Rock Types
- igneous rocks
- -“from fire” crystallized from molten rock
- -interlocking crystals
- sedimentary rocks
- -lithified fragments of pre-existing rocks
- metamorphic rocks
- -changed into new rocks by heat and/or pressure
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Magma
- Molten rock and volatile chemicals below the surface.
- -Completely or partially molten minerals
- Volatile compounds
- -water vapor (H2O
- -carbon dioxide (CO2)
- -sulfur dioxide (SO2)
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Lava
Magma that has reached the earth's surface
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Igneous Rocks
Rocks formed directly from the crystallization of magma or lava
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Extrusive (Defined)
- new rock from magma at or near the surface
- -or volcanic igneous rock
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Intrusive (Defined)
- new rock from magma below the surface
- -also called Plutonic Igneous Rocks
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Extrusive (4 Types)
- 1. Aphanitic
- 2. Glassy
- 3. Vesicular
- 4. Pyroclastic
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Aphanitic
- a solid mass of numerous fine crystals
- cool at or near the surface
- solidify relatively rapidly
- ex. Basalt
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Glassy
- "frozen magma"
- cool in the atmosphere or in water
- solidify "instantaneously"
- no time for crystals to assemble themselves
- ex. Obsidian
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Vesicular
- "spongy"
- cavities formed by trapped gasses in a rapidly cooling magma
- ex. Pumice
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Pyroclastic
- angular fragments, rock particles of various sizes
- generally within a fine grained matrix
- deposited from explosive volcanic eruptions
- ex. Tuft
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Types of Volcanoes and Volcanic Landforms
- 1. Shield Volcanoes
- 2. Tuyas
- 3. Cinder Cones
- 4. Composite Volcanoes
- 5. Calderas
- 6. Volcanic Fissures
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Shield Volcano
- Broad, slightly domed shaped
- generally covers large areas
- produced by low intesity eruptions of large columes of basaltic lava
- -Tuyas
- --extremely steep sided basaltic volcanoes erupted under ice
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Cinder Cone
- built mainly from ejected cinder and rock fragments
- steep slope angle/ small size
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Composite Cone (Stratovolcano)
- large, classic shaped volcano
- composed of inter bedded lava flows and pyroclastic debris
- most violent type of volcanic activity
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Caldera
- largo bowl-shaped depressions within large cones
- formed after violent eruptions empyt a large portion of the magma chamber
- volcano collapses in on iteselft
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Pahoehoe Flow
ropey texure
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Columnar Jointing
- large volumes of lava cooling
- -it insulates itself, creating vertical layers
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Pillow Lava
fissures under water
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