How Lava Viscosity and Pressure Change an Eruption

Low viscosity, low gas: Shield volcano, effusive eruption and lava that flows steadily and is runny,can flow very slowly.
Medium low viscosity, low gas: Cinder cone, minor eruption associated with building of these volcanoes, lava splatters around the rim of the volcano, lumps of lava shot out.
Medium high viscosity, low gas: Dome volcano, minor and uncommon eruption makes pancake like shapes of lava.
High viscosity, low gas: Dome volcano, similar to above, if the dome collapses then a pyroclastic flow can occur.
Low viscosity, high gas:Shield volcano, this is called a fire fountain, lava sprays out of the volcano.
Medium low viscosity, high gas: Cinder cone, strombolian eruption, series of explosions where lava sprays out and is relatively harmless.
Medium high viscosity, High gas: Stratovolcano, vulcanian eruption, loud series of explosions, ash clouds and debris are also present.
High viscosity, High gas: Stratovolcano, plinian eruption, most explosive type, ash clouds, pyroclastic flows and landslides are all associated with this type of eruption.


(Discovery Channel Website)


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