Volcanoes

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Volcanoes

Images used in this presentation are from the
United States Geological Survey
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What is a volcano?
An opening in the Earths surface through which
gases, ash and/or molten rock escape.
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How common are volcanoes?

• About 50 eruptions
• worldwide every year

• About 500 volcanic
• centers worldwide

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Why Study Volcanoes?

• Human Safety
• Land-use Planning
• Mineral Exploration
• Effects on Climate
• Energy Source

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Products of Volcanic Eruptions

• Lava Flows
• Pyroclastics
• Gases
• Lahars
• Pyroclastic Flows
• Tsunamis
• Effects on Weather and Climate

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Lava Flows

• Usually not dangerous
• Move slowly (people can get away)
• Predictable path (down stream valleys)
• Destroy everything in their path
• Some control success with dams, dikes and water
  sprays

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Pyroclastics

• Ejected materials
• Dust (powder-size)
• Carried by wind
• Breathing hazard
• Lifted high into atmosphere
• Blocks sunlight
• Danger to aircraft

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Pyroclastics (continued)

• Ash (sand-size)
• Carried by the wind
• Thick accumulations
• Overloads roofs
• Damages crops
• Removal problem
• Cinders (up to a few inches in size)
• Bombs / Blocks (very large particles)

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Gases

• Water vapor
• Carbon dioxide
• Carbon monoxide
• Sulfur compounds
• Chlorine compounds
• Many of these are deadly
• Diluted when carried a short distance
• Some react in the atmosphere

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Lahars

• A mudflow (water, ash, soil, plants)
• Very fast (up to 60 mph)
• Travel down stream valleys
• Long travel distances (up to 100 miles)
• Flash melting of a snowcap
• Heavy rains during eruption
• Heavy rains at later times

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Pyroclastic Flows

• Cloud of superheated gas/dust/ash
• Produced with little or no warning
• Heavier than air (flows downhill)
• Fast up to 60 mph
• Incinerates everything
• Knocks down buildings
• Effects on Weather and Climate

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Tsunami

• Seismic seawave
• Produced by a volcanic blast / earthquake
• Very fast hundreds of miles per hour in the
  open ocean
• Builds into a giant breaker in shallow water
  (over 100 feet tall)
• Not a tidal wave nothing to do with tides

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Climate and Weather Effects

• Large amounts of dust in atmosphere
• Blocks sunlight
• Large amounts of gases in atmosphere
• React with atmospheric gases to modify incoming
  sunlight