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Volcanoes Composite.ppt

  1. VOLCANOES By Caleb Pothier and Bonita Sanford
  3. ~An opening in the earth's crust through which molten lava, ash, and gases are ejected. ~A similar opening on the surface of another planet. ~A mountain formed by the materials ejected from a volcano. What is A Volcano?
  4. What is a volcano? • A volcano connects molten rock (magma) from within the Earth’s crust to the Earth's surface. • The volcano includes the surrounding cone of erupted material. vent cone magma chamber conduit
  5. The types Of Volcanoes ~ Shield Volcano ~ Cinder Cone Volcano ~ Composite Volcano ~ Caldera Volcano ~ Fissure Volcano
  6. TYPES OF ERUPTIONS ERUPTIONS FALL INTO 2 CATEGORIES Violent(explosive) eruptions destroy the volcano Non-Violent (calm or quiet) eruptions build up the volcano
  7. Shield volcanoes can span across hundreds of miles. Shield volcanoes have a gentle slope and consist of frozen lava after it is hardened. Shield volcanoes almost always have large craters at their summit. Gentle slopes = non-violent eruptions Hot spots!
  8. Cinder cone volcanoes consist of mostly loose, grainy cinders and have very little to no lava. Cinder cone volcanoes are normally small about a miles span and about one thousand feet vertically. Cinder cone volcanoes have fairly steep slopes and normally have a small crater at the top. Steep slopes = explosive or violent eruptions
  9. Composite volcanoes have another name called “Strato Volcanoes.” Composite volcanoes consist of lava that is mixed with sand or gravel which in turn creates cinders or volcanic ash. Steep slopes = explosive or violent eruptions
  10. Caldera volcanoes are circular depressions in the ground over a magma chamber. Sometimes the depression in Caldera volcanoes are covered in with lava and volcanic ash making it hard to recognize. This type of volcano is easier noticed from space due to the distance and view point. When this volcano erupts it can spew volcanic rocks for miles and miles.
  11. Fissure volcanoes are also hard to recognize from the ground and sometimes from space. Fissure volcanoes have no main crater, the ground just splits and lava pours out through the cracks. After a fissure volcano erupts and has cooled because it’s a solid it will look mainly like the plains.
  12. Types Of Magma Granite magma consist of light-colored rock and is not as heavy as basalt magma. Granite magma is very sticky and flows rather slowly. Basalt magma consist of dark-colored rocks and is much heavier then granite magma. It flows more fluidly then molten granite.
  13. Volcano Environments ~In an island-arc environment, volcanoes lie along the crest of an arcuate. ~In an oceanic environment, volcanoes are aligned along the crest of a broad ridge that marks an active fracture system in the oceanic crust. ~In the continental environment, volcanoes are located unstable, mountainous belts that have thick roots of granite or granite like rock.
  14. Where are volcanoes likely to occur? Volcanoes occur in weak spots in the earth’s crust There are many volcanoes along the Pacific Ocean. Many islands in the Pacific Ocean are actually volcanoes. They form a ring around the ocean which is called the “Pacific Belt of Fire.” Although there are some other “belts of fire”, the “Pacific Belt of Fire” is the biggest. There are approximately five hundred active volcanoes, that are known, lying in these belts.
  15. Volcanoes In Other Places Volcanoes aren’t just a thing from earth they also happen on other planets as seen in this picture. But while on other planets there is no destruction as we have seen from volcanoes on earth. Mariner 9 imagery of Olympus Mons volcano on Mars
  16. VOLCANO FORMATION: HOT SPOTS  A fixed source of magma rising beneath a plate forming volcanic islands  Magma can be basaltic or granitic – so eruptions can be explosive or “quiet”
  17. When and how do eruptions occur? Steam and gases from magma in the earth create bubbles that expand and burst when the pressure above them is lessened. These bubbles usually burst with a tremendous force that along with escaping gas comes magma too. In some cases, it takes years for the magma to break through the surface of the earth.
  18. Why do eruptions occur? Eruptions occur when underground pressure is released when blocks of the earth’s crust shift. For example, earthquakes.
  19. Direct measurements of pyroclastic flows are extremely dangerous!!!
  20. Effusive Eruptions • Effusive eruptions are characterised by outpourings of lava on to the ground. Hawaii Courtesy of
  21. Damages The most devastating destruction from volcanoes is the tremendous loss of life. Following an eruption in 1815, there were 56 000 people killed by a tidal wave from a eruption. Lava from the volcano is hot enough to catch everything in its path on fire, even the ash from a volcano is hot enough to start fires. Lahar can wash away houses and uproot trees. Magma can give off poisonous gases such as carbon monoxide. Damages from volcanoes are very expensive to repair or replace.
  22. No Yes (Cinder Cone) No Yes (Shield) No (These are the Catskills) No Yes (Composite) No Which of these are volcanoes?