Volcanic Explosion - John Seach

Volcanic Explosion - John Seach
Hawaiian, Lava fountain, Phreatoplinian, Plinian, Strombolian, Surtseyan, Vulcanian.

A volcanic explosion is a violent release of lava as it is torn apart by the bursting of gas bubbles. Magmatic volatiles determine the explosivity of volcanic eruptions. Some viscous magmas have internal pressures of 100 atm only a few metres below the surface. Eruption velocities at a vent are determined by the amount of gas in the magma. Eruption velocities can reach 400-600 m/s for plinian eruptions. Eruption velocities can be estimated by the size of blocks deposited near the vent. The height of lava fountains is determined by the amount of gas in the erupting magma. Lava fountains of 200-800 m require pre-eruption amounts of water at 0.3% to 0.6%.

Volcanic explosion terms

Explosion caldera	Subsidence caldera
Explosion crater	Explosion vent
Explosion focus	Point at the top of a magma column underneath the solidified plug. It acts as a choke for the accumulating gases.
Explosion funnel	A conical depression at the top of a volcano.
Explosion graben	A long, narrow sink with deep wells. It originates when many explosion vents are arranged in a row.
Explosion lake	Water filled maar.
Explosion level	Upper part of a magma column where gases accumulate.
Explosion pit	Vent created by gas eruption without lava emission.
Explosion point	Stage at which gas erupts from the magma.
Explosion vent	Vent marked by explosions.
Explosion tuff	Tuff produced by explosive activity.
Exploding bomb	Bomb which violently throws off fragments during flight due to cooling.