Igneous Rocks and Volcanoes

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Volcanoes
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View From Space - Klyuchevskaya, Russia
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Magma molten rock beneath the surfaceLava
molten rock on the surface
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Types of Volcanoes
Composite Cone or
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A Cinder ConeWizard Island at Crater Lake,
Oregon
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Cinder Cone, Hawaii
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Tuff Ring Diamond Head, Hawaii
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Tuff Ring Diamond Head, Hawaii
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Shield Volcano Haleakala, Hawaii
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Stratovolcano or Composite Cone Mount Shasta,
California
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Shastina and Landslide Deposit
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Products of Eruptions

• Gases
• Steam
• Carbon Dioxide
• H2S
• SO2
• HCl
• HF

• Lava Flows
• Pyroclastic Debris
• Bombs
• Lapilli
• Ash
• Mudflows
• Landslides

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Environmental Hazards of Volcanoes

• Pollution
• SO2, HCl in Water
• Lava Flows
• Falling Ejecta
• Ash Falls
• Building Collapse
• Crop Destruction

• Mudflows
• Direct Damage (Colombia, 1985)
• Floods (Several Types)
• Blast (Mt. St. Helens, 1980)
• Pyroclastic Flow (St. Pierre, 1902)
• Gas (Lake Nyos, Cameroon, 1986)

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Pyroclastic Flow or Nuee- Ardente (French Fiery
Cloud)
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How Calderas Form
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Crater Lake, Oregon
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Jemez Caldera, New Mexico
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Collapsing Volcanoes Mount Rainier
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Collapsing Volcanoes - Hawaii
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Evolution of Volcanoes

• An active volcanic landscape

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Evolution of Volcanoes

• A volcanic landscape after a million years or so

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Mauna Loa is a classic example of a shield volcano
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Mount Hood is a stratovolcano in the Cascades of
northern Oregon
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The caldera at Crater Lake National Park cuts
through the flanks of the former Mount Mazama
(composite cone)
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Layers of tephra on Usu (stratovolcano) in Japan.
The crater by the volcanologists was formed in
1977-1978.
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Eruption of Galunggung (stratovolcano) in
Indonesia.
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1980 eruption of Mt. Saint Helens produced 0.1
cubic miles (0.5 cubic km) of ash.

• Stratovolcanoes are associated with subduction
  zones, areas where dense oceanic plates are
  pushed beneath more buoyant continental plates.

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The cinder cone in the above photo is Puu Lilinue
on Mauna Kea in Hawaii.
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Cinder cones are produced by "fire fountains,"
low-energy eruptions that propel fragments of
lava 100s of feet into the air.
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A volcanic dome is a steep-sided, rounded
extrusion of highly viscous lava squeezed out
from a volcano to form a dome-shaped, or bulbous,
mass of lava above and around the volcanic vent
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During the 1989-1990 eruption of Redpubt volcano
(Alaska) several lava domes grew and collapsed
near the summit of the volcano.
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Flood Basalts

• The Columbia River basalts cover parts of the
  states of Oregon, Washington, and Idaho and are a
  famous example of flood basalts that produced a
  lava plain.

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Lava

• Eruptions under water or ice produce pillow lava
  (become pillow basalt)

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Coastal Flows
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"Pahoehoe" and "aa" are Hawaiian words used to
describe the type of lava volcanoes have
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Aa Flow

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Pahoehoe
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Lava Tubes