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Basaltic lava less silica and higher temperature, low viscosity, gasses escape at surface low pressures, not explosive
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tarix | 01.02.2018 | ölçüsü | 464 b. | | #23377 |
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Basaltic lava - less silica and higher temperature, low viscosity, gasses escape at surface low pressures, not explosive e.g. Shield volcanoes, Rifts, MOR, cinder cones Intermediate silica, explosive, composite = stratovolcanoes, Andes, Cascades, Aleutians Japan, Philippines, often pyroclastic clouds = nuée ardente Rhyolitic lava - more silica and lower temperatures, high viscosity, gasses cannot escape, explosive.
Exhalative (gas: H2O, CO2, SO2) Exhalative (gas: H2O, CO2, SO2) Effusive (lava) Explosive (tephra)
Explosive (tephra)
Coarse = close Thick = close
Layered
Columbia Plateau Columbia Plateau Deccan Traps
Projectiles Divergent Margin +
Rare, extremely explosive Rare, extremely explosive Size of ash cover = violence Toba and our near-extinction
Is on the mid-Atlantic Ridge, 13 volcanoes have erupted since AD 874. most active & volatile is Grímsvötn. Over the past 500 years, Iceland's volcanoes have erupted a third of the total global lava output. One quarter of Iceland ‘s population died due to eruption of the craters of Laki in 1783-84. The craters are a part of a larger volcanic system with the subglacial Grímsvötn as a central volcano. Because most of Grímsvötn’s eruptions have been subglacial, the interaction of magma and meltwater from the ice causes phreatomagmatic explosions
Plugs Dikes
Laccoliths - Henry Mts.
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