VOLCANOES
EARTH SCIENCE
Mrs. Baker
cjcb2015
Volcanoes
• An opening in the Earth’s
crust that erupts gases,
ash, and lava
(pyroclastic material).
There are more than
600 active volcanoes
on Earth!
Mt. Kilauea in Hawaii is
the most active
volcano!
Vocabulary
Parts of a Volcano
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A Magma Reservoir
B Flank
C Conduit
D Crater
E Solidified Lava
F Dike
G Ash
H Vent
I Sill
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INTERACTIVE WEBSITES (GO TO “LAUNCH”):
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.nyiragon
go/anatomy-of-a-volcano/
(images)
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.volcanintr
o/volcanism/
(LOTS of information)
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Viscosity
The ability of a substance
to resist flowing.
Materials that flow quickly have a
low viscosity. Examples:
water, basaltic magma
Materials that flow slowly have a
high viscosity. Examples:
syrup, Rhyolitic magma
Types of Magma
• Temperature, pressure, and amount of
water affect the formation of magma.
Explosiveness of a Volcano
• The explosiveness of a volcano depends
on the viscosity of the magma within it.
• High in silica, low in water vapor = High
viscosity.
• The magma will clog the main vent, build
up pressure and result in an explosion.
Life of a Volcano
• Extinct- has not erupted in recorded history
• Dormant- has erupted in recorded history,
not currently erupting
• Active- is currently erupting
Batholith: Large igneous rock mass
underneath mountains
Dike: Magma that cuts across preexisting rock
Laccolith: small pool of magma that collects
just under Earth’s surface
Pluton: Intrusive igneous rocks formed by
converging plates
Sill: Pool of solidified magma in between rock
layers
Stock: Small batholith
Caldera: large crater formed from
volcano collapse during or after it
erupts
Crater: depression at volcano’s
Summit
http://www.boston.com/bigpicture/2011/02/nyiragongo_crater_journey_to_t.html
Hot Spot: Hot area of a tectonic plate not along
plate boundary
Tephra: Rock fragments thrown into the air
during a volcanic eruption
Vent: Opening in Earth’s crust where lava erupts
and flows outward
Pyroclastic Flow: Fast-moving cloud of ash,
gas, and volcanic material after an eruption
Types of Volcanoes
• Cinder Cone
• Composite
• Shield
Composite
Volcanoes
• Composed of alternating
bands of pyroclastic
material (volcanic
fragments) and lava.
• Explosive eruptions
• Andesitic magma (high
silica)
• Example: Mt St Helens
and Mt. Rainier in the
Cascade Range
Pyroclastic
material
Mt St Helens
Solidified
Lava
Mt. Rainier
Shield Volcanoes
• Wide volcanoes,
gentle slope
• Composed of layers
of solidified magma
• Calm lava eruptions
• Basaltic Magma (low
silica)
• Example: Hawaiian
Islands
Solidified lava
Cinder Cone
• Composed of pyroclastic material (Tephravolcanic fragments)
• Small and steep
• Explosive eruptions (high silica)
• Example: Paricutin in Mexico
Pyroclastic
Materials
Volcanoes
•The majority of Earth’s
surface volcanoes are
found along the Pacific
Plate Boundary- Ring
of Fire.
-due to the subduction of
the Pacific Plate.
Volcano Formation at Convergent
Boundaries
Volcano Formation at Convergent
Boundaries
Mt St. Helens
Mt. Pinatubo
Aleutian Islands
Volcanoes
• Volcanoes also
form along the midocean ridges
-due to upwelling
of magma
- long fissures in
places
Volcano Formation at Divergent
Boundaries
Volcano Formation at Divergent
Boundaries
Iceland Volcanic Activity
Black Smoker,
Mid-Atlantic Ridge
Pillow Basalts,
South Pacific
Volcano Formation NOT at Plate
Boundaries: Hot Spot Volcanoes
The Islands of Hawaii
• These islands formed
over a period of 5
million years.
• The islands are slowly
moving to the
northwest with a
active hot spot
currently under the
island of Hawaii.
Plate Movement
Hot Spot
The Yellowstone Caldera is the volcanic
caldera located in Yellowstone National Park
in the United States, sometimes referred to
as the Yellowstone Supervolcano
Volcanic Hazards
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Lava Flows
Pyroclastic Flows
Lahars
Earthquakes
Tsunamis
Toxic Gases
Volcanic Bombs
Ash Falls
More…