During a volcanic eruption there is most often a vertical blast from the top of the volcano. If the side of the volcano is weak then a lateral blast out of the side is possible.
Synonym: flank eruption
Features:
(1) The side of the volcano is weak. A landslide immediately before the eruption may weaken it further.
(2) Deformation from a rising lava dome may cause a bulge on the side of the volcano.
(3) The main force of the eruption goes through the weakened wall.
(4) The hot gases and ejecta go outwards parallel to the ground.
Because a large proportion of the eruption goes out laterally the extent of direct destruction in that direction may be much greater than for a vertical eruption. The zone of destruction is often in the shape of a cone spreading out from the volcano.
If the velocity of the blast exceeds 735 miles per hour then a sonic boom can be heard.
A volcano that has a lateral blast will usually have a vertical eruption as well.
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