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1070645
Factors affecting Volcanic Eruptions
Description
History (British History) Mind Map on Factors affecting Volcanic Eruptions, created by keistajupiter on 14/07/2014.
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geography
tectonics
volcanoes
history
british history
Mind Map by
keistajupiter
, updated more than 1 year ago
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Created by
keistajupiter
about 10 years ago
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Resource summary
Factors affecting Volcanic Eruptions
Dissolved Gases in Magma
Dissolved gases such as water vapour and carbon dioxide are present in magma.
These gases expand near the surface.
Vents = openings near the surface through which molten gases / rock are released.
Eruption violence related to how easily gas escapes from magma.
Gas escapes easily from less viscous magma.
More viscous magma = more explosive eruption.
Therefore the more viscous the magma, the more difficult it is for gas to escape the magma, and the more explosive the volcano.
Magma Temperature
Hotter magma is less viscous = less explosive.
Basaltic volcanoes are very hot - 1200°c.
Andesitic volcanoes are quite hot - 1000°c.
Rhyolitic volcanoes are cooler - 700°c.
The cooler the magma, the less viscous the lava, and therefore the more explosive the volcano.
Magma Composition
Low silica content magma is less viscous = less explosive.
Basaltic volcanoes have a low silica content - 42 to 52%.
Andesitic volcanoes have a medium silica content - 50% or more.
Rhyolitic volcanoes have a high silica content - 70% or more.
Therefore the higher the silica content, the more viscous the magma, and the more explosive the volcano.
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