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BASALTIC VOLCANISM (ERUPTION TYPES (P = Passive, E= Explosive) (Lava Lakes…
BASALTIC VOLCANISM
ERUPTION TYPES (P = Passive, E= Explosive)
Lava Lakes = P
Can form when the magma supply rate, heat transfer and pressure conditions are just right.Driven by heat, low viscosity magma and high gas supply They can be an analogue for plate tectonics, we see:
- Sea floor spreading (conservative)
- Transform faults (conservative)
- Subduction (destructive)
- Hot spots
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Conduits, Fractures and Fumaroles = P
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BASALTIC LAVA FEATURES
Lava Tubes - lava cools at the sides, top and bottom of a lava flow, keeping the interior of the flow insulated, allows flow to travel long distances >100km up to 5kmph
Rootless Eruptions form away form the main vent, often through sky lights which protrude from lava tubes
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Low magma viscosity allows the formation of larger bubbles during bubble ass]cent = formation of diff flow regimes = generate a no. of diff basaltic activity styles.
can be erupted as lavas in discrete strombolian explosions, during fissure activity and lava fountaining
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Lavas are flows of molten rock which are relatively degassed either fed from vents or by more explosive activity. Their temp and crystal content determine what form they take either Pahoehoe or 'a'a
Pahoehoe flows can be smotth, hummocky or have a ropey surface
'a'a lavas form when crystalisation causes the lava viscosity to increase, making it more resistance to flow, gives the lava a "crumbly" texture = appears to move in a "caterpillar track" motion.