Phreatic eruption

A phreatic eruption occurs when the magma meets a tablecloth of subterranean water, as it exists about it to a few hundred meters under the top of the volcano. In contact with the extreme temperature of the magma, this pocket of water is transformed into vapor, brutally increasing the internal pressure of the volcano which then becomes the seat of an explosive process. This dreaded phenomenon already occurred with the Meeting in 1860 and 1980 with the Holy Mont Helens, where one had then observed the projection of rock blocks to several kilometers of the crater.

At the time of the eruption:

Projections of bombs, lapilli and elements of the base
Clouds of ashes and gas

The base is crystalline.

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