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Volcano Powerpt


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Volcano Powerpt

  1. 1. By Ms.Kopchick Volcanoes
  2. 2. What are volcanoes? <ul><li>A Volcano is a gap in the earth where molten rock and other materials come to the earth's surface. Some volcanoes are just cracks in the earth's crusts. Others are weak places in the earth's crust, which occur on places where magma bubbles up through the crust and comes to the earth's surface. Magma is molten rock that occurs by partial melting of the crust and the mantle by high temperatures deep down in the ground. Once magma comes to the earth's surface it is called lava. </li></ul>
  3. 3. Active and non-active volcanoes <ul><li>A ctive volcanoes : which are likely to erupt at any moment </li></ul><ul><li>Dormant volcanoes :which lie dormant for centuries, but then erupt suddenly and violently </li></ul><ul><li>extinct volcanoes : ones no longer likely to erupt. </li></ul>
  4. 4. Types of Magma <ul><li>Basaltic Magma: Low viscosity (gentle flow), Low silica content (about 50 % ) </li></ul><ul><li>Basaltic magma forms Shield Volcanoes </li></ul><ul><li>Andesitic Magma: Intermediate viscosity ( can be both gentle and violent), Intermediate silica content (about 60 %) </li></ul><ul><li>Andesitic magma forms Composite Volcanoes </li></ul><ul><li>Rhyolitic Magam: High viscosity (very violent eruptions), High silica content (about 70 %) </li></ul><ul><li>Super volcanoes form out of rhyolitic magma along with Cinder Cones </li></ul>
  5. 5. Structure of a Volcano
  6. 6. 3 Types of Volcanoes <ul><li>Shield Volcano: broad, sloping sides made of basaltic lava layers (very gentle eruptions) </li></ul>
  7. 7. 3 Types of Volcanoes <ul><li>Cinder Cones: smallest of volcanoes, but have very steep sides. Material called cinders are ejected into the air, fall back to earth and pile upward. Very explosive rhyolitic lava. </li></ul>
  8. 8. 3 Types of Volcanoes <ul><li>Composite or Strato-Volcano: built up of alternating lava and ash /rock particles. Andesitic magma can be both explosive and gentle. The more gentle eruptions form the lava layers and the more explosive eruption form the ash/rock layers </li></ul>
  9. 9. Volcanic Material <ul><li>Ash: (volcanic): Fragments less than 2 millimeters in diameter of lava or rock blasted into the air by volcanic explosions. The MOST Dangerous eruptive material! Ash can travel for hundred of miles, it can block out the sunlight and change climate, it is poisonous to breath </li></ul>
  10. 10. Volcanic Material <ul><li>Bombs : Fragments of fluid or partially fluid lava or rock larger than 64 millimeters in size that are blasted into the air by volcanic explosions. </li></ul>
  11. 11. Volcanic Material <ul><li>Cinders: Cinders are vesicular lava fragments 1 centimeter or larger in diameter. </li></ul>
  12. 12. Volcanic Material <ul><li>Pumice: A light-colored, frothy, vesicular volcanic rock, usually of intermediate and felsic composition, formed by the expansion of gas in erupting lava. Commonly perceived as lumps or fragments of pea size and larger but can also occur abundantly as ash-size particles. Because of its numerous gas bubbles, pumice commonly floats on water </li></ul>
  13. 13. Volcanic Material <ul><li>Pyroclastic Flow : Pyroclastic flows are fluidized masses of rock fragments and gases that move rapidly in response to gravity. Pyroclastic flows can be very hot. They can reach 1075 degrees Fahrenheit. They also move extremely fast, over 60 miles per hour. </li></ul>
  14. 14. Famous Volcanoes <ul><li>Mt. Paricutin -----Cinder Cone </li></ul>
  15. 15. Famous Volcanoes <ul><li>Mt. St. Helens------------Compostite/Strato volcano </li></ul>
  16. 16. Famous Volcanoes <ul><li>Sunset Crater -------Cinder Cone </li></ul>
  17. 17. Famous Volcanoes <ul><li>Krakatoa-------Composite/Strato-Volcano </li></ul>
  18. 18. Famous Volcanoes <ul><li>Manau Loa -------Shield Volcano </li></ul>
  19. 19. Famous Volcanoes <ul><li>Mt. Kilauea ---------Shield Volcano </li></ul>