VOLCANISM Mount St. Helens, 1980 eruption. Where are volcanoes located?
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VOLCANISM Mount St. Helens, 1980 eruption
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Transcript of VOLCANISM Mount St. Helens, 1980 eruption. Where are volcanoes located?
Gentle-slopes (Shield Volcano)
Non-explosive eruptions
Basaltic flows
Low-viscosity Lava
Low SiO2 content
Mafic composition
Alternating layers of
Basaltic flows and
pyroclastic material
Mafic-felsic composition
steep-slopes (Composite Volcano)
Hot-spot volcanoes are composed of lavas that…
1. Are rich in silica, viscous and explosive
2. Are rich in silica, fluid and explosive
3. Are poor in silica, fluid and not as explosive as convergent margin volcanoes