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Chapter 9

Chapter 9. Volcanoes. Section 1. _________ : mountain that forms when layers of lava and volcanic ash erupt and build up. Magma is _________ dense than the rock around it, so it very slowly rises toward Earth’s surface.

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Chapter 9

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  1. Chapter 9 Volcanoes

  2. Section 1 • _________ : mountain that forms when layers of lava and volcanic ash erupt and build up

  3. Magma is _________ dense than the rock around it, so it very slowly rises toward Earth’s surface

  4. _________ : opening through which _________ flows out on to Earth’s surface

  5. Factors that Affect Eruptions • 1) Water Vapor and Trapped Gases: gas that gets trapped under high pressure eventually escapes, causing explosive eruptions • (slow release = _________ eruption)

  6. 2) Composition of Magma • A) _________ magma: contains little silica, is very _________ , and produces quiet, _________ eruptions

  7. B) _________ magma: is thick with a lot of silica which causes pressure to build, also has a lot of water vapor, which causes _________ eruptions

  8. Section 2

  9. _________ : opening at the top of a volcano’s vent

  10. Types • _________ Volcano: broad volcano with _________ _________ sides formed by _________ eruptions of basaltic lava • Ex. Hawaiian Islands

  11. _________ _________ Volcanoes: _________ , loosely consolidated volcano formed from falling tephra • Tephra: lava erupted into the air and cooled also known as _________

  12. _________ Volcano: cycle of lava and tephra is repeated over and over at convergent boundaries above subduction zones

  13. Formations • Batholiths: largest intrusive igneous rock body formed when huge bodies of magma cool underground and stop rising • Ex. Granite domes (Yosemite National Park)

  14. Formations • Dike: magma that is squeezed into a vertical crack and hardens

  15. Formations • Sill: magma that is squeezed into a horizontal crack and hardens

  16. Formations • Laccolith: dome of rock formed when magma that forms a sill may continue to push the rock layers upward

  17. Formations • Volcanic Neck: in a dead volcano, the cone erodes away first, leaving behind this solid igneous core

  18. Formations • _________ : after an eruption, the top of a volcano may collapse down into the vent, thus a very large opening is formed

  19. Section 3

  20. Where Do Volcanoes Occur? • 1) _________ Boundary: magma flows from rifts and is instantly cooled by seawater. It builds up from the seafloor, sometimes rising high enough to from islands • Ex. Iceland

  21. 2) _________ Boundaries: magma that is created in the subduction zone works its way to the surface, forming volcanoes • Ex. Mount Saint Helens

  22. Pacific _________ of _________ : area around the pacific plate where earthquakes and volcanoes are common

  23. 3) _________ _________ : areas in the mantle that are hotter than others. The melted rock rises toward the crust as magma

  24. Ex. Hawaiian Islands • (plate is moving but hot spot is stationary)

  25. Additional Information • Geothermal Energy: heat from magma can be used to heat water and produce steam in a power plant, the steam is pressurized and spins generators that make electricity

  26. Additional Information • Would it be better to clear forests for geothermal energy or to continue releasing pollution into the atmosphere?

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