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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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what is a volcano
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
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

where do volcanoes form1
Where do volcanoes form?
  • Volcanoes occur mostly along PLATE BOUNDARIES!

Ring of Fire:

Belt of volcanoes that surrounds the Pacific Plate (convergent boundaries)

where do volcanoes form2
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
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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

what are the two types of eruptions
What are the two types of eruptions?
  • QUIET – mostly lava erupts
  • EXPLOSIVE – ash, cinders, and bombs erupt
what is a pyroclastic flow
What is a pyroclastic flow?
  • Pyroclastic flow occurs during an explosive eruption.
  • composed of ash, cinders, bombs, gases
landforms created from lava
Landforms created from lava
  • SHIELD VOLCANO
  • CINDER CONE VOLCANO
  • COMPOSITE VOLCANO
shield volcanoes
Shield volcanoes
  • Low and broad
  • Quiet eruptions with lava flows, little pyroclastics
    • Example:

Mauna Loa

slide23

Cinder cone volcanoes

  • Small volcanoes with explosive pyroclastic eruptions from a single vent
  • Very steep “upside-down ice cream cone” slopes
slide26

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
slide31

Mt. Rainer

Mt. Adams

slide34

Mount St. Helens: May 19,1982

Elevation before eruption: 9,677ft.

Elevation after eruption: 8,377 ft.

what are the stages of a volcano
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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