Volcanoes and Plate Tectonics

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Volcanoes and Plate Tectonics
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What is a volcano?

• Volcanoes are weak spots in the crust where magma
  rises to the surface.

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Location of Volcanoes

• Volcanic belts form along the plate boundaries.
• Volcanoes occur in belts like the Ring of Fire

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Location of Volcanoes

• Most volcanoes occur along diverging plate
  boundaries or in subduction zones.

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Volcanoes at Diverging Plate Boundaries

• Volcanoes form at the mid-ocean ridge underwater

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Volcanoes at Converging Plate Boundaries

• Volcanoes form in subduction zones
• Two oceanic plates collide
• An oceanic plate and continental plate collide

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Volcanoes at Converging Boundaries

• If subduction zone involves two pieces of oceanic
  crust, volcanoes are created
• These volcanoes create a string of islands called
  an island arc

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Volcanoes at Converging Boundaries

• If subduction zone involves oceanic and
  continental crust, volcanoes are created on land.

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Hot Spot Volcanoes

• Hot spot is an area where magma melts through the
  crust like a blow torch
• Hot spots are not often at plate boundaries

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Hot Spot Volcanoes

• Hot spots volcanoes can be created in the ocean
  floor
• Hawaii

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Hot Spot Volcanoes

• Hot spots can form under continents
• Yellowstone
• National Park

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Types of Volcanoes

• There are three major types of volcanoes
• Shield
• Cinder Cone
• Composite

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Shield Volcanoes

• Lava slowly leaks onto crust and hardens
• Wide, gently sloping mountains

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Cinder Cone Volcanoes

• Steep, cone-shaped hill or mountain
• Lava is thick and produces ash and cinders
• This material piles up and forms the mountain

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Composite Volcanoes

• Tall, cone-shaped mountain
• Layers of lava alternate with layers of ash
• Lava leaks out in between explosions

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Lava Plateaus

• Sometimes, lava does not form mountains
• Lava flows out of crust and collects in one area,
  forming a high plateau

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Calderas

• Enormous eruptions can empty the magma chamber
  under the volcano
• With nothing left for support, the mountain
  collapses

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Caldera

• The hole left over is a caldera