VOLCANOES AND PLATE TECTONICS Ch. 3.1, 3.3, 3.4

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VOLCANOES AND PLATE TECTONICSCh. 3.1, 3.3, 3.4
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A. Volcanoes

1. A weak spot in the crust
2. Magma-molten material from mantle comes to the
   surface

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Vocabulary to know..

• Magma-
• molten material made of
• gases
• rock-forming substances
• water
• silica is the force for magma to erupt
• Lava-
• Is magma that reaches the surface

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B. Ring of Fire

1. Major volcanic belt
2. Formed by many volcanoes around the rim of the
   Pacific Ocean
3. Forms along plate boundaries

Volcano 101
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C. Volcanoes occur at.

• 1. Divergent Boundaries
• -mid-ocean ridge

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• 2. Subduction Zone
• -edges of oceans

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• 3. Hot Spots
• -magma from deep within mantle melts through the
  crust like a blow torch
• -Hawaii was formed this way

A Pacific Plate drifts over a hot spot to form
Hawaii
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Label your worksheet.
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What is viscosity?

• A physical property of a liquid
• The resistance of a
• liquid to flow
• The greater the viscosity,
• the slower the flow
• Lava viscosity depends on the silica content and
  temperature
• Pahoehoe fast moving lava, low viscosity
• Aa slow moving lava, high viscosity

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• Other vocabulary you should know.
• Active volcano
• -is erupting or will erupt
• Dormant volcano
• -sleeping
• -will awaken in the future, become active
• Extinct volcano
• -dead
• -will not erupt again

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Volcanic 4 Landforms

• Shield volcanoes
• 1.Many layers of lava
• 2. Quiet eruptions
• 3. Gently sloping mountain formed by repeated
  lava flows
• 4. 90 is lava flow
• 5. Lava flows far from the vent
• 6. Ex. Hawaiian Islands

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• Cinder Cone Volcanoes
• 1. piles of cinders form a cone-shaped hill
• 2. a pyroclastic flow, explosive eruptions,
  producing
• ash
• cinders
• gases
• bombs
• -mass of
• thick magma
• 3. the longer the eruption, the higher the cone

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• Composite volcanoes
• 1. known as stratovolcanoes
• 2. tall mountain volcano
• 3. explosive eruptions
• 4. alternating layers of ash, cinders, bombs
• 5. multiple eruptions over hundreds of years
• 6. occur in chains, mostly in the Ring of Fire
• 7. Ex. Mount St. Helens
• Mt. Rainier

How Volcanoes Form