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VOLCANOES

VOLCANOES. What is a volcano?. A volcano is a weak spot in the crust where magma comes to the surface. Volcanoes are a constructive force (adds new rock to existing crust). http://gvc1007.gvc10.virtualclassroom.org/volcanoes.html. Where do volcanoes form?.

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VOLCANOES

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  1. VOLCANOES

  2. What is a volcano? • A volcano is a weak spot in the crust where magma comes to the surface. • Volcanoes are a constructive force (adds new rock to existing crust). http://gvc1007.gvc10.virtualclassroom.org/volcanoes.html

  3. Where do volcanoes form? • Volcanoes occur mostly along PLATE BOUNDARIES! • Divergent boundaries: volcanoes form along mid-ocean ridges and rift valleys • Convergent boundaries: volcanoes form at oceanic plate collisions

  4. Where do volcanoes form? • Volcanoes occur mostly along PLATE BOUNDARIES! Ring of Fire: Belt of volcanoes that surrounds the Pacific Plate (convergent boundaries)

  5. Where do volcanoes form? • Volcanoes also occur at hot spots! • a hot spotis an area where magma rises from deep in the mantle through the crust • stays in one place, creating a trail of volcanoes, as plate moves above it • oldest volcanoes are furthest from hot spot; newest volcanoes are closest • Example: Hawaii

  6. Parts of a volcano crater A bowl shaped area that may form at the top of a volcano. Any opening in a volcano pipe A long tube connecting the magma chamber to the surface Where magma collects beneath a volcano

  7. CRATER

  8. What are the two types of eruptions? • QUIET – mostly lava erupts • EXPLOSIVE – ash, cinders, and bombs erupt

  9. Explosive

  10. Quiet

  11. What is a pyroclastic flow? • Pyroclastic flow occurs during an explosive eruption. • composed of ash, cinders, bombs, gases

  12. Landforms created from lava • SHIELD VOLCANO • CINDER CONE VOLCANO • COMPOSITE VOLCANO

  13. Shield volcanoes • Low and broad • Quiet eruptions with lava flows, little pyroclastics • Example: Mauna Loa

  14. Shield Volcano— low and broad in shape

  15. Mauna Loa—located on the big island of Hawaii, largest volcano on Earth

  16. Kilauea

  17. Surtsey, Iceland

  18. Cinder cone volcanoes • Small volcanoes with explosive pyroclastic eruptions from a single vent • Very steep “upside-down ice cream cone” slopes

  19. Sunset Crater(Arizona) — among the largest cinder cones in the world

  20. Composite Volcanoes • Formed by alternating layers of molten lava, volcanic rock and ash • Very steep and jagged • Can have both quiet and explosive eruptions • Example: Mt. Rainer

  21. Composite Volcano

  22. Mt. Rainer, Washington

  23. Mt. Rainer, Washington

  24. Mt. Fuji, Japan

  25. Mt. Rainer Mt. Adams

  26. 1980: Mt. St. Helens before the eruption.

  27. 1982: Mt. St. Helens after the eruption.

  28. Mount St. Helens: May 19,1982 Elevation before eruption: 9,677ft. Elevation after eruption: 8,377 ft.

  29. Mount Hood, Oregon: Elevation 11,239 ft.

  30. Mt. Lassen, California

  31. Mt. Shasta, California

  32. Mt Vesuvius

  33. Profiles of Volcano Types

  34. What are the stages of a volcano? • An active volcano is currently erupting or showing signs of erupting in the future. • A dormant volcano is not showing signs of erupting but may erupt in the future. • An extinct volcano is not likely to erupt again.

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