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Volcanoes

Volcanoes. Volcano - a place where magma reaches the surface due to its lower density. A constructive & destructive force , creating new crust and destroying it in explosive eruptions A “window” into the Earth’s interior. Volcano Diagram. Types of Eruptions. Explosive Eruption

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Volcanoes

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  1. Volcanoes Volcano- a place where magma reaches the surface due to its lower density. A constructive & destructive force, creating new crust and destroying it in explosive eruptions • A “window” into the Earth’s interior

  2. Volcano Diagram

  3. Types of Eruptions • Explosive Eruption • Caused by thick silicon rich lava or from lava with high water content • dust & ash clouds • pyroclastic flows reaching speeds of 200 km/h and temperatures over 700 degrees Celsius. • ex: Ring of Fire

  4. Types of Eruptions

  5. Types of Eruptions • Slow/Quiet Eruption • Caused from little silicon in lava • easily flows • ex: Mid-Atlantic Ridge & Hawaii

  6. Types of Lava • High Viscosity Lava (flow slowly) Blocky Lava Pahoehoe

  7. Types of Lava • Low Viscosity Lava (flows quickly) Pillow Lava Aa

  8. Types of Lava Rock (Igneous Rock) • Basalt • dark colored • high content of Fe & Mg

  9. Types of Lava Rock (continued) • Rhyolite Lava • light colored • high content of Si & Al

  10. Pumice porous trapped gases floats Obsidian cools so fast no crystals form (volcanic glass) Types of Lava Rock (continued)

  11. Types of Pyroclastic Material • Volcanic Dust • smallest, very fine • .25 mm (size of flour) • reaches high in stratosphere • can circle globe for years, effecting weather

  12. Types of Pyroclastic Material • Volcanic Ash • 0.25mm to 5 mm (size of rice)

  13. Types of Pyroclastic Material • Volcanic Cinder or Lapilla • a few cm in size (size of a golf ball)

  14. Types of Pyroclastic Material • Volcanic bombs • Blobs of magma that harden in the air

  15. Types of Pyroclastic Material • Volcanic Blocks • Pieces of rock erupted from a volcano

  16. Types of Volcanoes • Shield Volcano • slow/quiet eruption • basalt lava rock • covers a huge area of land • gently sloping sides • ex: Mauna Loa, HI

  17. Types of Volcanoes (continued) • Cinder Cone • layers of cinders • explosive eruptions • narrow base & steep sides • associated with larger volcanoes

  18. Types of Volcanoes (continued) • Composite Volcano • a.k.a. stratovolcanoes • layers of cinder & lava • explosive eruptions of cinder & ash followed by lava flows • rhyolite lava rock • ex: Ring of Fire Volcanoes

  19. Volcanic Activity • Active • continuous or periodic eruptions • ex: Mt. St. Helens, WA & Mauna Loa, HI • Dormant (sleeping) • has erupted in modern time, is now inactive • ex: Mt. Rainer, WA & Mt. Hood, OR • Extinct • has not erupted in modern history • ex: Mt. St. Helens before 1980

  20. Craters and Calderas • Crater • funnel-shaped pit at the top of a volcanic cone • Caldera • a large crater formed from the collapse of the magma chamber that feeds the volcano • Ex. Yellowstone

  21. Lava Plateaus, Geysers and Hot Springs • Lava Plateau • a landform from repeated lava flows spread over a large area. • Ex. Columbia River Plateau is 3 km thick • Geysers and Hot Springs • Super heated water from magma coming in contact with ground water. • Ex. Old Faithful

  22. Old Faithful

  23. Mt. St. Helens, WA Before 1980 Eruption Mt. St. Helens in 1984 Just After Eruption

  24. What is the Volcano Type? A. Sunset Crater, AZ B. Mt. Hood, OR C. Kahoolawe, HI

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