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Mindmap von keistajupiter, aktualisiert more than 1 year ago
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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.
- 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.
- Gas escapes easily from less viscous magma.
- Therefore the more viscous the magma, the more
difficult it is for gas to escape the magma, and the
more explosive the volcano.
- Dissolved gases such as water vapour
and carbon dioxide are present in
magma.
- 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.
- Hotter magma is less viscous = less explosive.
- 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.
- Low silica content magma is less
viscous = less explosive.
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