VOLCANOES
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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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VOLCANOES

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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?

  • 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 form?

  • Volcanoes occur mostly along PLATE BOUNDARIES!

Ring of Fire:

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


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


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


CRATER


What are the two types of eruptions?

  • QUIET – mostly lava erupts

  • EXPLOSIVE – ash, cinders, and bombs erupt


Explosive


Quiet


What is a pyroclastic flow?

  • Pyroclastic flow occurs during an explosive eruption.

  • composed of ash, cinders, bombs, gases


Landforms created from lava

  • SHIELD VOLCANO

  • CINDER CONE VOLCANO

  • COMPOSITE VOLCANO


Shield volcanoes

  • Low and broad

  • Quiet eruptions with lava flows, little pyroclastics

    • Example:

      Mauna Loa


Shield Volcano— low and broad in shape


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


Kilauea


Surtsey, Iceland


Cinder cone volcanoes

  • Small volcanoes with explosive pyroclastic eruptions from a single vent

  • Very steep “upside-down ice cream cone” slopes


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


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


Composite Volcano


Mt. Rainer, Washington


Mt. Rainer, Washington


Mt. Fuji, Japan


Mt. Rainer

Mt. Adams


1980: Mt. St. Helens before the eruption.


1982: Mt. St. Helens after the eruption.


Mount St. Helens: May 19,1982

Elevation before eruption: 9,677ft.

Elevation after eruption: 8,377 ft.


Mount Hood, Oregon: Elevation 11,239 ft.


Mt. Lassen, California


Mt. Shasta, California


Mt Vesuvius


Profiles of Volcano Types


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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