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8.2 Volcanic Eruptions

8.2 Volcanic Eruptions. Where the rock cycle begins. Learning Targets. Compare the types of volcanic eruptions Describe a method for predicting volcanic eruptions. Volcanic Eruption. Magma collects in magma chamber Hot magma expands  creates pressure

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8.2 Volcanic Eruptions

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  1. 8.2 Volcanic Eruptions Where the rock cycle begins

  2. Learning Targets • Compare the types of volcanic eruptions • Describe a method for predicting volcanic eruptions

  3. Volcanic Eruption • Magma collects in magma chamber • Hot magma expands creates pressure • Vent: crack in the earth’s surface • Magma moving through vent = eruption

  4. How do volcanoes erupt? • Types of eruptions: • Explosive • Non-explosive; effusive

  5. Explosive Eruptions • Can be 1000 times more powerful than atomic bomb • Pressure builds as gases in magma expand

  6. Explosive Eruptions • Explosion shoots ash and gas high in the air • Heavy debris falls; light debris may float around for years • Why is ash and gas in the air important? • Blocks sunlight, produces poisonous gas, mixes with water to form acid, global climate change

  7. Explosive Eruptions • Some magma crystallizes in the air • Called pyroclastic material: ash, lapilli, bomb • Can come down miles from the volcano

  8. Non-explosive eruptions • Another name for non-explosive eruptions • Effusive eruptions • Different mix of mineralsin magma • No gas build up • Less dangerous but lava flows are consistent and unstoppable

  9. Magma Formation • What causes magma to form • High heat • Hot Spots; effusive • Decreased pressure • Divergent boundaries; effusive • Increased water content • Subduction zones; explosive

  10. Lava - Viscosity • Viscosity: Resistance to flow • Honey, ketchup, water • High viscosity • High silica content • Explosiveeruptions  pressure • Low viscosity • Low silica content • Effusiveeruptions  no pressure

  11. Lava formations • Explosivelava  Pyroclastic material • Pyroclast – lava solidifies in the atmosphere • Pyroclastic flow – fast moving current of superheated gas and rock • Can move hundreds of miles per hour • Effusivelava • A’a: jagged, gravelly texture • Pahoehoe: smooth, even lava flow • Pillow lava: cools underwater forms rounded lobes

  12. Predicting Eruptions • History of eruption • Active, dormant, extinct • Earthquakes • Pressureof magma causes earthquakes • Slope deformation • Plastic deformation due to pressure • Gas emissions • Gas escapes before magma

  13. 5. Remote Monitoring

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