Greetings! Please tell me everything that ever happened at Mt. St.
Helens in one page or less!! Seriously, why do all the
simulations that show her erupting again show her erupting in the same
direction as May 1980? Also, what are the long-term predictions for the
changes in topography caused by Mt. St. Helens' eruptions? (Such as the
pumice plain and the new lakes formed by the eruption.)
Sue Wall
Hi Sue,
Part of your question is a lot easier to answer than the other part.
Unless future eruptions are really huge, the reason that they will go out
to the north is that there is no caldera wall in that direction. Any
explosions that are directed to the east, south, or west will just hit the
walls of the caldera and bounce back. However, eruptions directed to the
north have free access to the outside world.
As for the future of topography changes, this is harder to predict. I
guess one of the more dramatic topographic changes was the damming of the
North Toutle by the big debris avalanche. There is a paper in the USGS
Professional Paper #1250 that describes this avalanche and its potential
for failure leading to a catastrophic flood down the N. Toutle. They
determined that there was little risk of such an event. That isn't much
of an answer, but perhaps one of our Mt. St. Helens experts, Jon Nelson,
will add to my answer (hint hint).
Sincerely,
Scott Rowland
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