Transcript Volcano Menu

Volcanic
Eruptions and
Volcano Type
What is a volcano?
•A volcano is any place
where gas, ash, or
melted rock come out
of the ground.
Anatomy of
a Volcano
• Crater
– Lava collects in the
crater, the bowlshaped area that
forms around the
volcano’s vent.
Vent
Crater
Lava Flow
Side Vent
Pipe
Magma
chamber
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• Vent
– The point on the
surface where
magma and gas
leave the volcano’s
pipe.
Vent
Crater
Lava Flow
Side Vent
Pipe
Magma
chamber
Volcano
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• Pipe
– A narrow, almost
vertical crack in the
crust through which
magma rises to the
surface.
Vent
Crater
Lava Flow
Side Vent
Pipe
Magma
chamber
Volcano
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• Magma Chamber
– A large underground
pocket of magma that
forms from magma rising
to the surface.
Vent
Crater
Lava Flow
Side Vent
Pipe
Magma
chamber
Volcano
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• Lava Flow
– The river of lava
that pours down a
volcano over the
land.
Vent
Crater
Lava Flow
Side Vent
Pipe
Magma
chamber
Volcano
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• Types of Volcanic
Eruptions
– A volcano’s magma
determines its
volcanic cone and
influences how the
volcano erupts.
– The silica content
helps determine
whether the volcanic
eruption is quiet or
explosive.
Shield Cones and Quiet Eruptions
(Examples: Grimsvotn of Iceland and Kilauea of Hawaii)
*Form as a result of sea-floor spreading or
“hotspots” in the Earth’s mantle.
• Shield Cones and Quiet Eruptions
– Magma flows easily.
– Dissolved gases in the magma bubble out easily.
– Thin runny lava oozes from the vent and flows
• Volcanic Hazards of Quiet Eruptions
– Quiet Eruptions:
• Lava flows- set fire and bury everything in
their path.
Composite Volcanoes and Explosive Eruptions
(Examples: Mount Vesuvius of Italy and Mount Saint Helens Washington State)
*Form as a result of subduction.
• Volcanic Hazards
– Time between
eruptions for
composite cones can
span hundreds of
years.
(Dormant Volcano)
– Example: Mt. St.
Helens 123 years.
– People may be
unaware of the
danger.
• Explosive Eruptions
• Magma is thick and
sticky.
• Thick magma builds up
in the pipe, plugging it
like a cork in a bottle.
• Pressure builds up due
to the gases in the
magma until the volcano
explodes.
• Volcanic Hazards
of Explosive
Eruptions
– Lahar:
• A mud flow
caused by
melted snow.
– Carries ash,
trees and
rocks.
• Explosive Eruptions
• The gases push the
magma out with
incredible force.
• The explosion breaks
lava into fragments that
quickly cool and harden
into different sizes.
• Explosive Eruptions
• Fragments:
– Volcanic Ash
» fine, rocky, grain of
sand sized particles.
– Cinders» pebble sized particles
– Bombs» large pieces of rock
(baseball to the size of
a car)
• Explosive Eruptions
• Pyroclastic Flow
– Occurs when an
explosive eruption
hurls out ash,
cinders and bombs
as well as gases.
(400mph, 1,800˚F)