Explosion - John Seach
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
||Point at the
top of a magma column underneath the solidified plug. It acts as a choke
for the accumulating gases.
||A conical depression
at the top of a volcano.
||A long, narrow
sink with deep wells. It originates when many explosion vents are arranged
in a row.
of a magma column where gases accumulate.
by gas eruption without lava emission.
||Stage at which
gas erupts from the magma.
by explosive activity.
violently throws off fragments during flight due to cooling.
Copyright John Seach