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Chapter 7 Lesson 3 Volcanoes

Chapter 7 Lesson 3 Volcanoes. What is a Volcano?. Volcano- a place where molten rock, hot gases, and solid rock from deep underground erupt through an opening in the crust . What is a Volcano?.

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Chapter 7 Lesson 3 Volcanoes

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  1. Chapter 7 Lesson 3Volcanoes

  2. What is a Volcano? • Volcano- a place where molten rock, hot gases, and solid rock from deep underground erupt through an opening in the crust.

  3. What is a Volcano? • Beneath every volcano is a source of magma that rises to the surface through cracks in the rock and erupts out of a central opening, or vent to become lava.

  4. What is a Volcano? • Once magma comes out of the vent, it is called lava. • At the top of the volcano there is a hollow around the vent called a crater.

  5. How Do Volcanoes Form? • Magma can collect below a volcano in an area called the magma chamber. • As the magma accumulates the pressure inside the magma chamber increases. • When the pressure becomes too great, the chamber breaks open, and the magma rises in the volcano.

  6. How Do Volcanoes Form? • If magma reaches the surface, an eruption occurs through the vent of the volcano. • Erupted material cools and hardens around the vent in a mound. • After many eruptions it can pile up into a big hill or mountain; this is a volcano.

  7. How Do Volcanoes Form?

  8. Where Do Volcanoes Occur?

  9. Where Do Volcanoes Occur? • The Pacific Ring of Fire is an area located by the edge of the Pacific Plate and is known for its volcano and earthquake activity. • Most volcanoes occur in belts along the edges of plates along convergent and divergent boundaries.

  10. Where Do Volcanoes Occur? • Where plates are moving apart, volcanoes can form at the edge of spreading plates. • These are called rift volcanoes and they are found deep underwater along mid-ocean ridges. • Volcanoes also form along the edges of slowly colliding plates where one plate plunges beneath another.

  11. Where Do Volcanoes Occur? • Example: The volcanic island arc of Japan

  12. Where Do Volcanoes Occur? • Sometimes volcanoes can form in the middle of plate over a hot spot. • Hot spot- a very hot part of the Earth’s mantle, where magma can melt through a plate moving above it. • Example: The Hawaiian Islands

  13. Volcanoes Are Classified into Three Types Based on How They Form • Cinder-Cone Volcano • Sudden, violent eruption • Steep cone-shaped mound • Ex. Mount Paricutin, Mexico

  14. Volcanoes Are Classified into Three Types Based on How They Form • Shield Volcano • Slow, gentle eruption • Low, gently-sloped sides • Ex. Mauna Kea in Hawaii

  15. Volcanoes Are Classified into Three Types Based on How They Form • Composite Volcano • Both violent and gentle eruption • Cone-shaped mound, steep sides • Ex. Mount St. Helen’s in Washington State

  16. Why Are Only Some Volcanoes Active? • An active volcano is one that has recently erupted and there is a possibility that it may erupt soon. • A dormant volcano has not been active for a long time but has erupted in recorded history. • An extinct volcano has not erupted in recorded history.

  17. BRAIN POP - VOLCANOES • http://www.brainpop.com/science/earthsystem/volcanoes/ • See World Book Online Student for a table of famous volcanoes.

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