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Volcano Explosions and Types. What causes different types of explosions?. Trapped gases: Water vapor and carbon dioxide can be trapped in the magma Results in an explosive eruption Composition Silica poor Silica rich. Silica Poor. Low in silica- basaltic magma
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What causes different types of explosions? • Trapped gases: • Water vapor and carbon dioxide can be trapped in the magma • Results in an explosive eruption • Composition • Silica poor • Silica rich
Silica Poor • Low in silica- basaltic magma • Results in a quiet, non-explosive eruption • Kilauea • http://www.youtube.com/watch?v=tcRz_EIZsRk
Silica Rich • High in silica- granitic • Magma being forced upward by denser surrounding rock comes in contact with the crust which is rich in silica • Soufriere Hills • http://www.youtube.com/watch?v=8sPyyHY57H4
Neither Rich or Poor in Silica • Between basaltic and granitic- Andesitic • Often forms at convergent plate boundaries when one plate slides under the other • Violent eruption • Krakatau • http://www.youtube.com/watch?v=JmPuy-pqIQE&feature=related
Forms of Volcanoes • Three main types: • Shield • Cinder cone • Composite
Shield Volcanoes • Typically has sloping sides • Caused by basaltic lava spreading out in flat layers • Hawaii
Cinder Cone • Steep, loosely packed sides • Usually from materials of explosive volcanoes falling back to earth and settling on the mountain sides • Paricutin
Composite • Tepha- composed of rock and/or solidified lava • Composite volcano is the result of layering • Tephra-lava-tephra-etc. • Often occurs where plates come together and one slides beneath the other • Soufriere Hills