"Peter Duniho" wrote in message
...

They didn't expect it? Is that why they did a full-scale evacuation?

I'm a little confused...can you be more specific? I can easily believe
that
the 1980 eruption was even larger than expected, but as far as I know,
they
DID expect a very large eruption, one much larger than what they are
currently expecting.

I would expect you to be both confused and just as contrary as usual. I can
at least count on you to keep life from getting dull. In any event, there
was no full-scale evacuation, nor did they predict an explosion at all. They
were concerned about slides and avalanches, and by the time of the eruption
they were letting all kinds of people back into the area to retrieve
possessions and such. In case you have forgotten, 57 people died in the
explosion. Although hundreds of airplanes were reported flying in the
evacuation zones, the FAA investigated only seven reports.

In 1980 St. Helens began a series of eruptions that attracted people from
all over. The Park area was much smaller in those days and there was no good
way of keeping people out. People were 'advised' to leave the area, but some
sightseers and residents, like Harry Truman, stayed. The news media reported
the eruptions extensively, attracting even more people. In any event,
'evacuations,' such as they were, were ordered at the start of the
eruptions, were incomplete. Ostensibly, the area of evacuation was for 15
miles from the mountain. The reason given for the evacuations was that they
were concerned about the potential for avalanches. There was a 'Red Zone,'
where the threat of avalanche was considered severe, and a 'Blue Zone,'
where flooding might be expected. The evacuations were poorly handled, with
deputies manning the roadblocks sometimes just going home. At one point, a
man from Skykomish actually managed to evade the roadblocks in April and
climbed to the summit. At that time, 109 airplanes were reported to be
within the evacuation zone. The evacuation zone was actually reduced in size
in April because merchants were threatening to sue for lost business.

St. Helens is very similar in geological structure to Novarupta in Katmai,
which gave birth to The Valley of Ten Thousand Smokes in Alaska. I felt at
the time that if the harmonic tremors on St. Helens stopped abruptly, then
pressure would build inside the volcano and there would be a huge explosion
within a few weeks. However, none of the scientists studying the volcano
seemed concerned about that and I figured that they knew what they were
talking about. All of the scientific concern was focused on mud flows and
avalanches. No one talked about a major explosion. You can see all this in
the St. Helens diary at http://makeashorterlink.com/?U29731F69 maintained by
USGS.

The flow of magma and the harmonic tremors did suddenly stop on May 8.
Scientists and the news media speculated that "the show is over" and that
there might be more small eruptions in the next few years but that the main
event was over. They talked about letting reducing the size of the
evacuation area and, for all I know, they did. The evacuation areas were
constantly being reconfigured at the request of local property owners who
were demanding access to their summer cabins on Spirit Lake and elsewhere,
but scientists continued to be concerned about the possibility of avalanche.
Jack Hyde, a geologist at Tacoma Community College, said that he thought the
avalanche might be followed by an explosion, but that was discounted. They
were actually escorting property owners in and out of Spirit Lake right up
to the day before the explosion. Another trip was planned for the morning of
May 18.

The explosion of 1980 was only 1/30 the size of that at Novarupta, but
devastated an area up to 20 miles from the mountain. Flying over it today
still reveals an awesome demonstration of the power of that blast. Trees are
flattened in all directions leading from the mountain.

I should mention that Hollywood made an atrocious movie (which I have not
seen) about St. Helens which I understand portrayed scientist David Johnston
as a renegade who predicted the explosion when no one would listen to him
and who had an affair with a local waitress. Nothing could be further from
the truth. Johnston, by all accounts, worked well with his colleagues and
was happily married. His measurements with lasers enabled him to predict on
April 28 that the north flank would have to collapse and no one disputed
that. Still, he never predicted that the mountain would blow up, certainly
with the force that it did, or he would have been much further away.
Johnston was courageous but he was nobody's fool.

People simply do not understand the power and danger of these volcanoes. At
least scientists studying the volcano today are better equipped and funded
and have not discounted the possibility of another explosion. Personally, I
would feel better if they got everybody out of there and kept them out.

The USGS site has this quote from May 5, 1980:

One of the reasons some people do not understand why scientists and
officials have remained cautious may be their familiarity with famous
Hawaiian volcanoes. Their frequent eruptions and familiar lava flows have
contributed to the popular belief that all volcanoes have fluid, channelized
lava flows. One logger was quoted: "We're logging 10 miles away from the
peak...I don't see any hazard. I just came back from Hawaii, where they run
tourist buses right up to the edge of a venting volcano."