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Volcanoes
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Magma Molten rock underground- magma Molten rock aboveground- lava
Volcano- an opening in Earth’s Crust through which an eruption takes place.
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2 types of Magma Mafic- low silica content, thinner, darker, flows easily. Felsic- high silica content, thick, light- colored, slow moving
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Volcanic Gases Water vapor, carbon dioxide, sulfur are the most important gases. The more gas in the magma the more explosive the eruption.
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Tephra Debris released from volcanoes Ranges from 2 mm- 64 mm
Ash smallest particles- bad for lungs, build up can collapse buildings. Ash Lapilli Bombs/Blocks
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Pyroclastic Flow Extremely hot gases sweeping down an area/side/flank of a volcano. Most dangerous part of a volcanic eruption.
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Extraterrestrial Volcanoes
Lava flows on the moon The largest volcano in the solar system is on Mars: Olympus Mons Io, a moon of Jupiter, has more than 100 volcanoes.
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Volcanic Structure 1. Large magma chamber 2. Bedrock 3. Conduit (pipe) 4. Base 5. Sill 6. Dike 7. Layers of ash emitted by the volcano 8. Flank 9. Layers of lava emitted by the volcano 10. Central Vent / “Throat” 11. Parasitic cone 12. Lava flow 13. Vent (left = side vent) 14. Crater / “Mouth” 15. Ash cloud
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Sills and Dikes A Sill is where magma cuts between layers of preexisting rock in the volcano. A Dike is where magma cuts across layers of preexisting rock.
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Caldera Huge crater caused by the collapse of materials back towards the crust. Can be miles long. Crater Lake in Oregon is a caldera.
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Shield Volcano Gas levels: Low Viscosity: Thin, “mafic lava”
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Cinder Cones Gas levels: High Viscosity: Medium
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Composite (Strato) Volcano
Gas levels: High Viscosity: Thick, “felsic lava”
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Lava Dome Gas levels: Low Viscosity: Thick, “felsic lava”
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