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Chapter 9 Volcanoes

Chapter 9 Volcanoes. 9.1 How and Where Volcanoes Form. How and Where Volcanoes Form. The term volcano refers to both the opening that the lava escapes from and the landform that develops around this opening. Magma Formation. A volcanic eruption occurs when magma rises to the surface.

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Chapter 9 Volcanoes

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  1. Chapter 9Volcanoes

  2. 9.1How and Where Volcanoes Form

  3. How and Where Volcanoes Form • The term volcano refers to both the opening that the lava escapes from and the landform that develops around this opening.

  4. Magma Formation • A volcanic eruption occurs when magma rises to the surface. • Solid rock beneath the surface can become magma one of three ways… - Decreased pressure - Increase in temperature - Increase in amount of water

  5. Once magma forms it raises up because it is less dense. e e

  6. At Subduction Boundaries • Subduction boundaries are where plates collide. • When an oceanic plate collides with a continental plate mountain ranges form like the Cascades. Click to see animation of Himalas Form

  7. When an oceanic plate collides with another oceanic plate - volcanic island arcs form like the Aleutians. Click to see Volcanic Island Arcs form

  8. The oceanic plate carries water with it to depth. This allows the melting point to lower forming magma. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es0902page01.cfm?chapter_no=visualization

  9. Pompeii • Subduction zone volcanoes can produce violent eruptions that can burry whole cities like Pompeii (79 AD) with little warning.

  10. At Divergent Boundaries • Where plates move away from each other, pressure is lowered. • This allows for magma to form, raise and create new crust.

  11. This also creates a ridge or raised area that runs for thousands of miles below the oceans. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0903/es0903page01.cfm?chapter_no=visualization

  12. Over Hot Spots • In some places the magma gets so hot it burns through the crust. • The Hawaiian Islands were created from the Pacific plate moving slowly over one of these hot spots.

  13. Over millions of years this process has created an island chain over a 1000 miles long. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0904/es0904page01.cfm?chapter_no=visualization

  14. State Standards3b Students know the principal structures that format the three different kinds of plate boundaries.3f* Students know the explanation for the locationand properties of volcanoes that are due to hotspots and the explanation for those that are due to subduction.

  15. Quiz1. A volcanic eruption occurs when _______ rises to the surface.2. Magma can form from a decreased in pressure, increase in temperature, and an increase in _____3. What is created at the surface when an oceanic plate collides with another oceanic plate? 4. A __________ boundary is where plates move away from each other.5. Hawaii was formed by a ______ spot.

  16. End

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