A volcano is a mountain that forms when molten rock is forced to the Earth

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A volcano is a mountain that forms when
molten rock is forced to the Earths surface.
Volcanoes can by active, dormant, or extinct.
Volcanoes
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Active Volcano
Kilauea Volcano is presently one of the most
active volcanoes on Earth.
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Dormant Sleeping Volcano
Mt. Hood, Oregon
Dormant Volcano A volcano which is presently
inactive but which may erupt again. Most of the
major Cascade volcanoes are believed to be
dormant rather than extinct.
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Extinct Volcano
Kohala Volcano
Extinct Volcano A volcano that is not presently
erupting and is not likely to do so for a very
long time in the future.
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Where do volcanoes form?
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1. Volcanoes form when hot material from below rises
   and leaks into the crust.
2. Eventually, but not always, the magma erupts onto
   the surface. Strong earthquakes accompany rising
   magma.

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Parícutin, Mexico, 1943

• In the winter of 1943, the countryside near
  Parícutin, Mexico was rocked by a series of
  earthquakes. The tremors lasted for nearly two
  weeks when a fissure open in a farmer's field and
  the birth of cinder cone was underway. Within 12
  hours of the initial eruption, the fissure was
  ejecting pyroclastic material as well as huge
  clouds of gas and ash. Lava began to spill from
  the base of the cone building the volcano
  laterally.

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Parícutin, Mexico, 1943

• Within 24 hours a 40 meter high cone hurling
  volcanic bombs several kilometers away had been
  built.
• After nine years of activity, two villages had
  been buried

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Anatomy of a Volcano
Crater- A bowl-shaped depression at the mouth of
a volcano Magma chamber -A large underground
pool of molten rock lying under the surface of
the earth's crust
Vent - The opening through which the molten rock
flows onto the surface.
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What is the difference between magma and lava??
Lava molten rock on the earths surface.
Magma molten rock deep inside the earth.
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II. What erupts from a volcano?

• Gases
• Water Vapor, Carbon Dioxide, Sulfur Dioxide,
  Nitrogen, Hydrogen, Argon
• Rock Fragments
• Dust, ash, bombs, and blocks
• LAVA!!

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IV. Types of Lava and Rock Fragments
aa Sharp, jagged lava
Pahoehoe - Smooth, wrinkled lava
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Pillow Lava
Pillow lava forms on the ocean floor and cools
into rounded blobs.
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In Greek Pyro fire Clastic Broken
Mt. St. Helens
Mt. Pinatubo
Pyroclastic material - avalanche of hot ash,
pumice, rock fragments, and volcanic gas that
rushes down the side of a volcano
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Rock Fragments
Lapilli less than 64 mm in diameter
Volcanic ash 2 mm in diameter Volcanic dust
- lt 0.25 mm in diameter
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Volcanic blocks greater than 64 cm in diameter
Volcanic bombs greater then 64 mm in diameter
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III. Types of Volcanoes

• Shield Volcanoes
• Nonexplosive
• Thin, runny lava
• Gently sloping
• Dome-shaped mountains

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Stratovolcano or Composite

1. Alternating layers of rock particles and thick
   lava.
2. Violent eruptions
3. Large cone-shaped mountain
4. Most common type.

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Cinder Cone

1. Different sizes of volcanic material
2. Explosive eruptions
3. Large bowl-shaped craters
4. Steep sides with loose rock particles

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Mafic Lava
Felsic Lava
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What type of volcano am I?
Stromboli Volcano in Italy
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Mt. St. Helens, WA
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Kanaga Volcano in Alaska
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Sunset Crater, Arizona
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Mauna Loa Volcano, Hawaii
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• Water (steam) 77.0
• Carbon dioxide 11.7
• Nitrogen 3.0
• Carbon monoxide 0.5
• Hydrogen 0.5
• Sulfur dioxide 6.5
• Sulfur 0.3
• Chlorine 0.05
• Argon 0.05