Volcanoes

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Volcanoes
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View From Space - Klyuchevskaya, Russia
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Shiveluch, Russia
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Cleveland Volcano, Alaska
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Mount Etna From Space
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Mount Etna From Space
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Mount Etna From Space
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Mount Etna
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Magma molten rock beneath the surfaceLava
molten rock on the surface
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Where Does Magma Come From?

• Earths interior is hot (25 C/km near surface
  1000 C at 40 km)
• Pressure inhibits melting
• Mantle is solid
• Never far below melting point
• Volcanoes fed by small pockets 0-100 km deep
• Rising hot material may melt
• Water can lower melting point

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Why Igneous Rock Classification Matters

• Silica Content Viscosity
• Silica Content Governs Violence of Eruptions
• Silica Poor (Basalt) Fluid lavas, generally
  little explosive activity
• Intermediate Lavas (Andesite) Pasty lavas,
  explosive eruptions common
• Silica-Rich Lavas (Rhyolite) Extremely viscous
  lava and explosive eruptions

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Types of Volcanoes
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Bowen's Series and Volcanoes

• Volcanic Rocks
• (Rare)  Basalt   Andesite                
  Rhyolite
• Plutonic Rocks
• Dunite  Gabbro   Diorite                  
  Granite
• Fluid               Lava Is...                
  Viscous
• Mild                Eruptions                
  Violent
• Type of Volcano
• Shield Volcano     Stratovolcano    Plug Dome

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A Cinder ConeWizard Island, Crater Lake, Oregon
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Anatomy of a Cinder Cone, Hawaii
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Shield Volcano Haleakala, Hawaii
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Eyjafjallajokull, Iceland
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Stratovolcano Mount Shasta, California
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Lava Dome, California
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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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The Stump of Mount Mazama
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Supervolcanoes?

• Magma Chamber Collapse (Yellowstone?)
• Destruction of crops
• Destruction of high technology
• Economic Disruption
• Climatic Effects
• Flood Basalts
• Climatic Effects
• Toxicity

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Jemez Caldera, New Mexico
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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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Landslide, Mount Saint Helens
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Shastina and Landslide Deposit
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Mount Shasta and Landslide Deposit
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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