volcanoes
DESCRIPTION
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?. - PowerPoint PPT PresentationTRANSCRIPT
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VOLCANOES
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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
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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
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Where do volcanoes form?• Volcanoes occur mostly along PLATE
BOUNDARIES!Ring of Fire:
Belt of volcanoes that surrounds the Pacific Plate (convergent boundaries)
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Where do volcanoes form?• Volcanoes also occur at hot spots!– a hot spot is 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 fromhot spot; newest volcanoes are closest
– Example: Hawaii
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Where magma collects
beneath a volcano
A long tube
connecting the
magma chamber
to the surface
pipe
Parts of a volcano
Any opening in a volcano
A bowl shaped area that may form at the top of a volcano.
crater
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CRATERCRATER
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What are the two types of eruptions?
•QUIET – mostly lava erupts
•EXPLOSIVE – ash, cinders, and bombs erupt
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Explosive
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Quiet
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What is a pyroclastic flow?
• Pyroclastic flow occurs during an explosive eruption.
• composed of ash, cinders, bombs, gases
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Landforms created from lava
• SHIELD VOLCANO• CINDER CONE VOLCANO• COMPOSITE VOLCANO
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Shield volcanoes
• Low and broad• Quiet eruptions with lava flows, little
pyroclastics– Example:
Mauna Loa
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Shield Volcano— low and broad in shape
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Mauna Loa— located on the big island of Hawaii, largest volcano on
Earth
Mauna Loa— located on the big island of Hawaii, largest volcano on
Earth
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Kilauea
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Surtsey, Iceland
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Cinder cone volcanoes• Small volcanoes with explosive pyroclastic
eruptions from a single vent• Very steep “upside-down ice cream cone” slopes
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Sunset Crater (Arizona) — among the largest cinder cones in the world
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•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 Volcanoes
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Composite Volcano
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Mt. Rainer, Washington
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Mt. Rainer, Washington
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Mt. Fuji, Japan
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Mt. RainerMt. Adams
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1980: Mt. St. Helens before the eruption.
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1982: Mt. St. Helens after the eruption.
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Mount St. Helens: May 19,1982 Mount St. Helens: May 19,1982
Elevation before eruption: 9,677ftElevation before eruption: 9,677ft.Elevation after eruption: 8,377 ft.Elevation after eruption: 8,377 ft.
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Mount Hood, Oregon: Elevation 11,239 ft.
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Mt. Lassen, California
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Mt. Shasta, California
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Mt Vesuvius
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Profiles of Volcano Types
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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.