When Mt. St. Helens erupts again will the ash cloud be as large as
the 1980 eruption ?
W. Ostrander
Hi W. Ostrander,
Probably not. At the time of the 1980 eruption there was the weight of
the whole volcanic cone available to keep the magma pressure from
erupting. This allowed a large amount of pressure to build up and
consequently the eruption was large. Now the whole top of the mountain
is gone so there is a good deal less weight available as a counter
balance to the pressure. This means that eruptions occur after lesser
amounts of pressure have built up and the eruptions are therefore
smaller. Eventually, of course, Mt. St. Helens will recover its
cone-shaped shape by filling in the amphitheater with lava domes and
ash. Once this occurs (probably over a period of a few hundred years)
it'll be ready to suffer another large 1980-size eruption.
Sincerely,
Scott Rowland
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