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VOLCANIC ACTIVITY

18.1 Drifting Continents. VOLCANIC ACTIVITY. Magma. Molten rock, mineral grains, and dissolved gasses deep inside Earth Rocks begin to melt at 800 o -1200 o C Depth, pressure and melting point have a direct relationship However, wet rock melts at a lower temperature (p.472).

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VOLCANIC ACTIVITY

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  1. 18.1 Drifting Continents VOLCANIC ACTIVITY

  2. Magma • Molten rock, mineral grains, and dissolved gasses deep inside Earth • Rocks begin to melt at 800o-1200oC • Depth, pressure and melting point have a direct relationship • However, wet rock melts at a lower temperature (p.472)

  3. Types of Magma • Basaltic- Hawaiian Islands • Andesitic- Mount St. Helens • Rhyolitic- Yellowstone National Park

  4. Magma Composition • Viscosity- resistance to flow • Basaltic- low viscosity, low gas, low silica, quiet eruptions • Andesitic- found near subduction zones, intermediate viscosity, 60% silica, intermediate eruptions • Rhyolitic- high silica, high gas, very explosive!

  5. Viscosity • Hotter = less viscous • Basaltic lava temperatures = 1000o- 1250oC • Rhyolitic lava temperatures = 700o- 900oC • More silica = higher viscosity

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