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Volcanoes

Volcanoes. Chapter 2. What Is a Volcano?. Weak spot in the earth’s crust where molten material comes to the surface Magma – molten mixture of rock-forming substances, gases & water in mantle Lava - magma that has reached the surface

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Volcanoes

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  1. Volcanoes Chapter 2

  2. What Is a Volcano? • Weak spot in the earth’s crust where molten material comes to the surface • Magma – molten mixture of rock-forming substances, gases & water in mantle • Lava - magma that has reached the surface • Volcanic activity is a constructive force that adds new rock to existing land and forms new islands

  3. Where Are Volcanoes Located? • Approx. 600 active volcanoes on land & more under oceans! • Ring of fire – major volcanic belt around Pacific Plate • Three major locations: • Diverging plate boundaries • Converging plate boundaries • Hot spots

  4. How Do Volcanoes Form at Divergent Plate Boundaries? • Plates move away from each other • Lava pours out of cracks in ocean floor • Ex. mid-ocean ridge

  5. How Do Volcanoes Form at Convergent Plate Boundaries? • At subduction zones: • Slabs of oceanic crust sink into mantle • The crust melts forming magma • Less dense magma rises back towards surface & erupts as lava • Island Arcs • String of islands formed along deep ocean trench

  6. How Do Volcanoes Form at Hot Spots? • Hot spot - area where magma from deep in mantle melts through crust like a blow torch • Often in the middle of a plate • Locations: Hawaii, Yellowstone national park in Wyoming

  7. Stages of a Volcano • Active: (live) erupting or shows signs it may erupt in near future • Dormant: (sleeping) may erupt again but not for 1000’s of years • Extinct: (dead) unlikely to erupt again

  8. Parts of a Volcano • Magma chamber: large underground pocket of magma • Pipe: Narrow vertical crack in crust where magma rises • Side vent: branch off pipe • Vent: where magma leaves pipe • Crater: bowl-shaped area around vent

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