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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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chapter 9

Chapter 9


section 1
Section 1
  • _________ : mountain that forms when layers of lava and volcanic ash erupt and build up
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)
2) Composition of Magma
    • A) _________ magma: contains little silica, is very _________ , and produces quiet, _________ eruptions
B) _________ magma: is thick with a lot of silica which causes pressure to build, also has a lot of water vapor, which causes _________ eruptions
  • _________ Volcano: broad volcano with _________ _________ sides formed by _________ eruptions of basaltic lava
    • Ex. Hawaiian Islands
_________ _________ Volcanoes: _________ , loosely consolidated volcano formed from falling tephra
    • Tephra: lava erupted into the air and cooled also known as _________
_________ Volcano: cycle of lava and tephra is repeated over and over at convergent boundaries above subduction zones
  • Batholiths: largest intrusive igneous rock body formed when huge bodies of magma cool underground and stop rising
    • Ex. Granite domes (Yosemite National Park)
  • Dike: magma that is squeezed into a vertical crack and hardens
  • Sill: magma that is squeezed into a horizontal crack and hardens
  • Laccolith: dome of rock formed when magma that forms a sill may continue to push the rock layers upward
  • Volcanic Neck: in a dead volcano, the cone erodes away first, leaving behind this solid igneous core
  • _________ : after an eruption, the top of a volcano may collapse down into the vent, thus a very large opening is formed
where do volcanoes occur
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
2) _________ Boundaries: magma that is created in the subduction zone works its way to the surface, forming volcanoes
    • Ex. Mount Saint Helens
Pacific _________ of _________ : area around the pacific plate where earthquakes and volcanoes are common
3) _________ _________ : areas in the mantle that are hotter than others. The melted rock rises toward the crust as magma
Ex. Hawaiian Islands
  • (plate is moving but hot spot is stationary)
additional information
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
additional information33
Additional Information
  • Would it be better to clear forests for geothermal energy or to continue releasing pollution into the atmosphere?