Oh, dear God! My God, this is hell! I just can't describe it, it's pitch black, just pitch
black. This is hell on earth that I'm walking through. One step at a time, if I can just keep
walking. May 1980, Mount St. Helens, Washington. This is the actual recording made by cameraman
David Crockett as he tried to escape death. I never really thought I'd believe this or say this, but at this
moment, I honest to God believe I'm dead. After nine hours inside a suffocating ash cloud, Crockett
was rescued. Crockett was no innocent bystander. He was there to take pictures because scientists
were predicting a sudden violent eruption, but no one predicted that St. Helens would kill 63
people and destroy 200 square miles of Pacific Northwest. And in this unique film, you'll see
the first full inside account of the volcano that shocked both the world and the people who battled
to understand her. Anyone who paid attention to science class as a child ought to have some
idea of what the inside of a volcano looks like. Now here's a volcano and here is the tube where
the lava comes from and here's the lava producer and the lava is pushed up, up here, and the pressure
pushes it out and it goes, it cracks and goes through the walls and bubbles come up from the lava.
But the picture that's been drawn on a million blackboards does not represent the whole range
of volcanic behavior. At one extreme is the gently sloping Hawaiian type that produces
fountains and rivers of glowing lava. Spectacular, but not usually dangerous. Cooling lava moves so
slowly you can walk away from it. At the other extreme, the dangerous ones that explode without
warning. The molten rock inside a volcano is called magma. Its chemistry determines whether
a volcano produces either lava or pyroclastics, the rock fragments which explode from its peak
or both. Volcanologists from the United States Geological Survey see plenty of molten lava
in Hawaii, but don't often get the chance to study other types of volcano. St. Helens was the chance
of a lifetime. None of them was old enough to remember the last eruption in the continental
United States and the mountain had played a sort of geological overture for a full two months. So
when the curtain finally went up on the major eruption, it was played to a full house of
scientists and their instruments. What their instruments revealed, how one of their colleagues
died in his attempt to collect more data, and what it was like for these scientists to contend with
the political and social forces of public concern, are what this film is about. For this was not a
laboratory experiment, but a major human drama that disrupted the lives of evacuees, foresters,
tourists, and at times even the entire population of Portland as volcanic ash rained down on their
city. Through it all, the region kept its sense of humor, and the ash, though a major inconvenience,
was not lethal. It was even regarded as a gift from heaven by a few entrepreneurs. They saw a
profit to be made in melting it down and making, yes, souvenir ash trays. 315 in the Rose City from
Portland's KDDJJ, and Jeff Davis along with you. Boy, Mount St. Helens really lost her ash,
didn't she? I told her not to eat that stuff before breakfast. Hey, by the way, if you're
planning on visiting Washington State on vacation this year, don't bother, because Washington is
on its way to visit you this year. And you know when you die it's ashes to ashes and dust to dust.
If that's true, there's a lot of people coming and going out there today, isn't there? It's
potent stuff, I'm telling you. Here's a good one for you this afternoon from KDDJJ in Ashes of Love.
It's hard to imagine anyone less inclined to make snap judgments than a geologist. Trained,
like all scientists, to make statements only after careful experiment, those who study them
movements of rocks also get the feeling that a thousand years is about the shortest time in
which anything of interest can happen. But they came out of their labs for Mount St. Helens,
and so had to deal with the press, who wanted to know what was going to happen before their
next newscast. Even after the big eruption May 18th, the question was not so much what happened,
but what now? The usual pattern of events would not be to have another blast like the first one.
A person who is basically a scientist who is used to working in a fairly coherent and structured
manner to find himself faced with a situation that has no structure, in which there are many
more demands placed upon you than can possibly be met in any time frame, let alone in the very
miniscule amounts of time available. These kinds of things are extremely frustrating. But in the
overall sense, no. I mean, I think we recognize this as a social responsibility. We see it as a
challenge, something we hope to rise to, to the extent we can. Since her last eruption in 1857,
Mount St. Helens had been an advertisement for the beauty of nature, not a symbol of its
unpredictable violence. As a seismometer in a Seattle basement decisively twitched on March
20th, 1980, 123 years of inactivity inside Mount St. Helens was coming to an end. That opening
note of the overture was echoed by station after station, reporting the arrival of a substantial
earthquake. One of the guys came running downstairs saying that there had been a magnitude 4 earthquake
reported by one of the permanent manned observatories east of the mountains somewhere in Western
Washington. And we spent about 15 or 20 minutes ascertaining that the earthquake had been at
Mount St. Helens. And about 430 in the afternoon, we had a preliminary fix on the epicenter. We had
a located a very shallow on the north side of the mountain. At that time, there was no local seismic
coverage of Mount St. Helens. But by sheer coincidence, Craig Weaver and his colleague,
Steve Malone, had ordered a set of portable instruments for study of geothermal energy.
The machinery arrived Thursday night and was on the mountain by noon on Friday. Everything
really broke loose on Monday here. We had a further increase in seismicity overnight.
By Monday morning, we had initiated attempts to keep track of the earthquakes. And initially,
we started trying to count earthquakes at the magnitude 2 level. By the end of the day,
that was no longer possible. We were just simply coming too many and too fast. Monday,
we called the 24th, we called the USGS in Denver and said the volcano hazards people
and informed them that we had a major earthquake sequence going on, which was rapidly being,
it would have to be classified as a volcanic sequence. Tiny Vancouver, Washington instantly
became Mecca for geologists from all over the Western United States who dropped their hammers
and took the next plane. The first task was to pool their knowledge about St. Helens past behavior.
Yes, in one sense, we had a lot of good background data. But in another sense, we were very specifically
lacking in data that would give us a direct indication of what kinds of things to expect
by way of precursors. What kinds of gases had been emitted from Mount St. Helens before
any of the eruptions began? A lot of questions like that were totally unanswered.
But they did not share the luxury of time to talk history for long. The volcano's next
move was a small eruption that came five days later. It opened a fresh crater 200 feet wide
on the summit. The eruption had not been a full fire and brimstone affair, but a so-called
phreatic eruption in which heat rising from the deep magma melts part of the icy cap of
the volcano. The result is a steam explosion that draws out volcanic ash left over from
prior eruptions. This small eruption filmed in time-lapse was one of a series that happened
in April as St. Helens warmed up. The scientists were hard-pressed to predict when and even
if a major eruption would happen. A state of emergency was declared by Washington governor
Dixie Lee Ray. Our greatest effort, of course, right now is to get people out of the way
for anything that is occurring. Most of it, so far as any individual is concerned, seems
to be from the Tulal riverside. The second area of concern is the amount... The State
Highways Department held back from the unpopular move of closing down a local scenic area,
but were preempted by the U.S. Forest Service, who closed their own access roads. These people,
I think, have all been faced with pressures from many sides which cannot be resolved to
everybody's satisfaction. They've had to make decisions, they've had to make them quickly,
and I think they've attempted to make them fairly. We've attempted to give them the best
advice we can to use in making those decisions, but clearly we as scientists don't feel it
is either proper or possible for us to attempt to actually make those decisions. Five days
later a second fresh crater that had appeared merged with the first one. The volcano suddenly
seemed more like a living, growing thing than a dead heap of rock and ice. In an attempt
to comprehend the mountain's evolutionary timetable, the scientists tried everything
in the book, but the book on volcanoes of this type was disappointingly slim. No one
knew when the next blast would be, but after every eruption, scientists literally flirted
with death to scoop up ash samples for analysis. Back in a California lab, the chemistry of
the gray ash was analyzed. Chemists were interested not so much in what the ash was made of as
what gases were liberated along with it, particularly gases containing sulfur and chlorine. Titrating
the soluble fraction of the ash isolated those elements. If magma were rising up under the
volcano, it would give itself away by a slight shift in the relative proportions of those
gases. So although no single sample has much of a story to tell, a downward trend in a
series of gas ratio measurements is an indication that magma is on the move. But the mountain
did not reveal its secrets to the chemists. Up to the date of the last documented ash
sample, there was no clear trend. Physicists were equally frustrated by a lack of a clear
trend, though they believed magma was pushing up. The north face of the mountain was swelling
ominously outward. By mid-April, you didn't need any fancy instruments to see it bulging
300 feet out. One possible warning of an imminent eruption might have been a sudden change in
the bulge rate, but that never happened. The mountain grew rapidly, but steadily. By the
end of April, the state authorities agreed it was time to stand back. But the state of
emergency could not be sustained over three eventless weeks. On May 16th, residents were
squirted back into the restricted area. The scientists had no better suggestions. Hours
and days are meaningless within the context of a volcano's life cycle. According to plate
tectonic theory, volcanoes are often formed when oceanic rock flowing out of an undersea
rift is overridden by a continental plate. The friction energy in what's called the subduction
zone melts millions of tons of rock and strains the whole coastal region, allowing some of
the magma to escape to the surface. Apparently, just such a situation once existed in the
northeast Pacific Ocean. But compressing a 70 million year creep into a 30 second sprint,
the Pacific plate moved north as the plate in the middle continued to spread southeast
like this. And the rift line had a huge right angle turn where it stopped spreading and
slipped sideways instead. Fifty million years ago, the Pacific plate itself made contact
with America. And since the relative movement between those two was purely north south,
progressively more of the coast became a slipping zone instead of a subduction zone. This is
the situation today. Here's Los Angeles. Here's San Francisco. The 630 mile slip zone they
sit on is, of course, the famous San Andreas Fault, still slipping at the rate of two and
a half inches a year. Further north, near Seattle and Portland, is the last remaining
bit of a once huge oceanic plate and the last remaining young active volcanoes, the Cascade
Range, less than a million years old in their present positions. St. Helens is about halfway
up and somewhat apart from the rest. And the continuity of volcanic action in the Cascades
becomes apparent when you review the last hundred thousand years, speeded up about a
billion times. Here goes. Sixty thousand. Thirty thousand. Ten thousand. Seven thousand.
Hold it. That last one was the devastation of Mount Mazama, a volcano which lost its
top overnight and is now a tourist attraction known as Crater Lake. The last five thousand
years are better documented. There has not been a century in all that time when a Cascade
volcano hasn't erupted. In the last century, St. Helens, Mount Baker, Mount Rainier and
Mount Hood all had their moments. And finally, Mount Lassen in 1915. Two local geologists
who devoted their careers to St. Helens found stratigraphic evidence that the mountain had
erupted destructively long before there was a government to worry about compensation.
They found thick strata of St. Helens ash clear across the state, reconstructed the
historical eruption sequences and concluded that this was a mountain that should not be
trusted. They even took a large scale map of the area and drew on it the zones they
believed were at maximum risk from flows of lava, pyroclastics and meltwater which would
send torrents of mud down the river valleys. Dwight Crandall and Donald Mullineaux published
their maps in 1978. The booklet didn't say exactly when all this was going to happen.
Soon, perhaps before the end of the century. Many locals felt their farm animals had a
more immediate date in mind. Just as the honking of geese warned of an attack on Rome, so the
excitement of pigs correctly predicted the eruption of Mount St. Helens according to
Vern and Linda Loy. Pigs were squealing the whole time so I figured they must be extra
hungry. When I went out to feed them Ruby was so excited that she jumped up on top of
Wilbur the male and over the fence and ran around circles around the outside of the fence
and he was squealing the whole time too and I had to chase him. Oh, that must have been
an hour. After having so much trouble with the hogs we decided we had to take some drastic
measures and that took care of our problem right there, the butcher. Getting at least
as much media attention as the volcano was the 84-year-old man who defied the mountain
and became a national hero. Even if Harry Truman had wanted to change his mind, it's
difficult for a national hero to back down in front of millions of television viewers.
No way that you'd leave? No, I'm going to leave. I won't leave. They'll have to take
me out of here. They'll have to come get me. They better come get me there, get themselves
a goddamned nest bed of trouble if they come get Truman and they try to force me into anything
that governor better watch out too all the way after her. God damn right I will. She's
a Democrat. Geochemist Dave Johnson was also staying put to observe. He had no illusions
but being a geologist of course, he wasn't making any rash predictions. Hours, it could
be within days or even up to a couple of months. But right now there's a very great hazard
due to the fact that the glacier is breaking up on this side of the volcano on the north
side and that could produce a very large avalanche hazard. This is not a good spot to be standing.
On the night of May 17th, Johnston warily moved further away. Then early the next day,
without any warning, it happened.
All day and most of the next night, the volcano roared. No lava, just mid-air. The volcano
of tons of pumice, gas and ash. By Monday morning, 1,300 feet of its peak was missing.
In its place, a vast steaming cauldron of a crater, one mile wide. Most of what had
come out had been heated to near boiling and tossed down a valley. Harry Truman's lodge
was somewhere under the mud. Dave Johnston had reported the onset of the eruption by
radio and then gone off the air for good. Another real measure of the magnitude of what
had happened was that up to 20 miles away, full-grown Douglas fir trees had been stripped
clean and combed down flat against the hills.
It was a natural disaster of epic proportions, much bigger than the Crandall and Mullineau
maps predicted. The flows of mud in the river valleys had followed the historical pattern,
but the blast damage nearer the mountain had been almost entirely directed to the north.
An infrared aerial picture of the forest, taken on the 2nd of May, shows vegetation
colored dark red. Here's the equivalent picture the day after the eruption. Every trace of
life had been blasted off the map, way beyond what was considered to be the danger zone.
What finally triggered the big eruption was a magnitude 5 earthquake. Analysis of available
photographs taken a second and a half apart showed how the quake dislodged the bulge.
It was the biggest landslide ever recorded. We discussed many times the possibility of
land failure, slope failure, in the area of that bulge and the possibility that it would
go off to the north and have very far-reaching effects there. So we considered that very
strongly in our planning. We also talked about the possibility that such an event could actually
trigger an eruption. And of course, if one thinks then a few steps beyond that, the possibility
that such a lateral event triggering an eruption could produce a lateral eruption is perhaps
not so far-fetched that we shouldn't have given it more thought. And that is precisely
what happened next. With the restraining weight of the north face no longer there, the mountain
uncorked and the avalanche was rapidly overtaken by a black cloud that blasted sideways.
The magnitude of that lateral blast was really astounding. I think that caught all of us
quite by surprise. It was certainly not unprecedented as far as volcanic eruptions are concerned,
but to have such a lateral blast come on so quickly without an immediate pre-monitor is
something that I, even now, I don't think we could really anticipate. If the scientists
were taken by surprise, so were the local authorities. They'd been planning on the
basis of the Crandall and Mullineau maps and were now faced with something entirely different.
They had expected to have to control traffic and evacuees, but not mount a full-scale search
and rescue operation. The National Disaster Relief Machinery moved into action. Unfortunately,
it wasn't as efficiently coordinated as it looked. With the Army, the Air Force, and
the National Guard all eager to demonstrate their iron determination in the face of danger,
there was some confusion over radio frequencies, and search and rescue pilots faced another
problem. Their maps had gone obsolete overnight. There was no reliable list of people in the
area at the time. For a day or two, it was hard to see who was in charge, certainly not
the state government, no matter what their contingency plan may have said. It was the
Forest Service who ended up in control. Mount St. Helens was on their turf, and while their
forest fire management teams were not trained to deal with eruptions, at least they were
set up to implement decisions rapidly. But nothing would ease the task of finding the
casualties. There were 31 confirmed dead, and the location and condition of the bodies
was grim. The bodies were vital evidence for scientists attempting to understand the nature
of that terrible black cloud that swept across the forest. How hot was it? How fast did it
move? The commonest cause of death was ash asphyxiation, not heat. As for the speed of
the cloud, two people died in this car. They had about 400 yards to go, and they were doing
70 miles an hour, according to a survivor who overtook them at 100. The evidence of
survivors was even more valuable, and some were even closer in than victims. It seemed
to be a matter of luck. Thirteen miles due north, a group of young people were on a legitimate
camping trip, well outside the closed area. Their campsite was wrecked. One couple, Sue
Ruff and Bruce Nelson, miraculously survived and were rescued by the National Guard. Their
story was of extreme interest, not only to the press, but to volcanologists.
Can you describe that, what the ash was like? The ash was kind of warm. It was warm all
around us. I'd inhaled so much of it, it had gone down my throat. I swallowed a lot of
it and I had to dig it out of my mouth just to be able to talk. Can you give me any sort
of estimate as to how hot it got? My fingertips got burnt, blistered. Well, I work around
heat quite a bit, so I would estimate it was, I would say, right around 400 degree heat.
That's Fahrenheit. Right, and I crawled out, I pulled Sue out, and we got on top of the
timber, and just about the time we stood up, it went clear. All of a sudden we could see
blue sky. Can you give me some kind of time estimate as to how long this clearing lasted?
I'd say at the longest. 30 seconds. It wasn't very long. Well, it was long enough for Sue
to get her contacts out of her eyes. She handed them to me and I put them in a cigarette pack
that I had in my pocket. You can take your contacts out in 30 seconds? When I'm scared,
I can do anything. That's probably a little longer, 30 seconds. Working off aerial pictures
of the devastated forest, Dr. Susan Kiefer of the Geological Survey's Flagstaff Field
Center mapped the direction in which the millions of trees were laid flat in an attempt to come
to grips with the dynamics of that black cloud. Close to the mountain, the trees were wrenched
off their stumps and smashed. Then came a zone where they were laid flat, pointing away
from the mountain. Then, significantly, a large area where the cloud was moving slowly
enough to swirl around the contours of the terrain. A normal wind would need to be more
than 100 miles an hour to do that much damage and wouldn't follow contours that well. Dr.
Kiefer concludes that the cloud was very dense and so could bulldoze trees and heavy equipment
even at 70 or 80 miles an hour. It was not just gas, but a maelstrom containing chunks
of wood and large rocks, as well as steam and droplets of water. As for temperature,
Bruce Nelson's estimate was a bit high. A rim of burned trees at the limit of the blast
zone suggests that the temperature there was about 200 degrees Fahrenheit. Closer to the
mountain, of course, it had been hotter, and to find out how hot, someone had to get in
there and take the temperature of the pyroclastic flow. When gases dissolved in the rock are
liberated, they turn that flow into a rocky souffle. It looks like snow, except it's very
hot. It's a very good heat insulator, so two days after an eruption, the temperature is
still very high. Burns became an accepted occupational hazard.
Yeah, it just meant I've got to get an adapter. Ah, Jesus. It's hot. Yeah, you're sitting
right over a funeral where the rock's burning my knee. 602 at 75. Can I hit one meter? 623
at one meter. The surface also lacked tensile strength, so a helicopter couldn't land on
it. It had to hover at zero altitude, a dangerous maneuver. Jesus, look at that, Rick. It doesn't
look good, does it? Christ.
As NOVA watched the geologists literally risking their lives collecting detailed evidence,
photogrammetrists in more secure seats were getting equally vital information by finding
out just what violence the volcano had done to the contour map. The trick is to bring
a stereo pair of photographs together into a 3D image. Imagine the slight spot in the
middle sitting, say, halfway up a hill and fly it around the contour. You can't see the
3D effect on television and it wouldn't make much sense even if you could. The point of
all that is to help the geologist write one simple equation to find out how much fresh
material had come out of the volcano. Photogrammetry provided the starting point. The total volume
missing from the mountain was two-thirds of a cubic mile. That's about 30 times the combined
volume of every skyscraper in Manhattan, and most of it ended up in this instant city of
debris. The equation the geologist had in mind was to add up the volumes of everything
lying around the countryside and subtract the two-thirds of a cubic mile that used to
be part of the mountain. The remains must be fresh material from inside the Earth's crust.
They finally concluded that this debris flow amounted to all but five percent of the volcanic
eruption. Although it looked more impressive, the immense column of ash that roared out
of the volcano all day accounted for much less volume. Pictures taken by a weather satellite
during the day show the migration of the ash cloud across three states. A few million tons
will stay up in the stratosphere for a year or more, insignificant in the equation but
possibly significant for the world's weather. Ash rained down and paralyzed several communities.
Six hundred thousand tons fell on the town of Yakima to the northwest. Everyday life
became almost impossible, but in fact only one town close in to the south actually had
to be abandoned. It became for a while a dusty gray ghost town fit only for passing trucks
and television film crews. Geologists too had to venture into areas that by all reasonable
standards were unfit for human existence to collect ash from a measured area and deduce
its thickness at that point. Survey teams covered the ash smothered area rapidly in
a series of longitudinal traverses. From their results a contour map of ash thickness was
drawn. The total volume was worked out by considering each contour as a slab whose thickness
was known and whose area could then be measured with a planimeter. The grand total corrected
downward because of the relatively loose packing on the ground ash was point zero three four
of a cubic mile. Adding in one more figure from this blast deposit the answer was that
the total volume of new material was point zero one five of a cubic mile. It may not
sound much but it weighed one hundred and fifty million tons. Digging down through the
multi-layered deposit the advancing blast cloud left behind geologists were interested
in finding out when fresh material had begun to emerge and lay down a different colored
stratum. It was also a unique opportunity to see what evidence such a momentous explosion
leaves behind it. Knowing that they can now re-examine historical strata near the other
cascade volcanoes and pay closer attention to those with a tendency to erupt sideways
in the future. The deluge of ash led to a survival of the fittest.
Some
life survived in the ashfall area but in the actual blast zone mammals birds and fish were
wiped out. And although it looks as if nothing could have survived this calamity two biologists
from the forest and range experiment station went on a sort of grim hike through the blast
area two months later. They found that life was down but not quite out.
Jim that's a real neat area over here. I was in here and took a look at this the first
time I came in and this was an area that had a snow pack down over it and it protected
a lot of the plants underneath and then besides that as the snow was melted of course the
ash crust is slumped and broken up so all these plants have had a chance to come up
through it. We even see in this spot over here we see a silver fir tree that survived
the blast and that's not very common. Looks like the buds have just burst. Yeah now this
is something new here you know this wasn't here the first time a stink current's come
up here and here it is in bloom. That's really kind of impressive to see this thing blooming
out here. Do you think those are going to survive the summer not get desiccated out?
Well I don't have any doubts that they are going to survive as far as drought is concerned
that isn't going to be their main problem. The main problem is going to be the various
small critters running around things like insects that are going to tend to focus on
those few plants and chew them up. Dr. Jerry Franklin is a forestry biologist an expert
on the trees of the region and he was happy to see vegetation recuperating. Dr. Jim Seidel
is more interested in microorganisms and he was delighted to see that the extraordinary
conditions had not obliterated all his favorite organisms. Look over here Jerry we've got
some really interesting things here it's kind of a St. Helens version of primordial soup
in action. Most of this gunky material here is primarily metal feeding bacteria and the
orange material is a combination of both bacteria and algae growing on here. This black tarry
stuff here is started out first and was feeding on the nutrients from shattered rock and the
shattered organics fragments of trees and fragments of needles and leaves and subsequently
now they're feeding on remnants of that and they're feeding on each other and we've got
a real primordial brew going here. You know it's sure a smelly mess. It seems it would
take the end of the world itself to kill off microbiology. Surprisingly there are even
micro fungi that positively basked in the eruption coloring the surface of the ash and
enthusiastically colonizing the inside of the steam vents oozing sticky fluid. So the
ill wind that howled across this landscape blew some good to biologists who now have
a unique opportunity to watch nature repossessing the place. But the geology of St. Helens changed
as fast as the biology surrounding it. By mid-June after two more small eruptions it
had evolved a lava dome 600 feet across on top of the vent. The dome was like a sleeping
dragon squatting just behind the rampart left by the collapse of the north wall its cool
surface crackling and hissing as the hot plastic interior expanded. A dome can have one of
two fates. It becomes either the volcanic offspring from which a new peak will grow
or it will be instantly blown to bits by a new blast of magma. Any geologist who goes
near a dome does so in the certain knowledge that he's courting death. And yet day after
day Nova Watch scientists fly into the huge amphitheater land and set up a series of glass
reflectors on short posts. Each reflector had to be visible from at least one precise
spot on a hill facing the volcano. Even here the danger of sudden death was considerable.
But if someone hadn't been prepared to undertake these risks not to mention the sheer hard
work there would be no accurate means of measuring slight movements of the mountain. The reflector
is now being set up at the left extremity of the flat rampart under the sheared off
crater wall. The exact time it takes a pulse of laser light to make the round trip between
instrument and reflector is a measure of the distance between them. If it's slightly less
than it was yesterday this side of the mountain is swelling. Took them until June to reestablish
the whole network of geophysical instrumentation around the mountain much of which was destroyed
on May 18th. From then on experts like Peter Lipman were able to give reports to the evening
meetings whenever the weather was clear enough for the laser to see properly. An independent
geophysics team from Portland State University was meanwhile setting up instruments around
the southern flank of the mountain. They were tilt meters, electrical devices buried in
the ground which record on a paper chart every minute change in the slope of the mountain.
Throughout April and May these instruments registered steeper slopes as the mountain
inflated. Then these and some of the geological surveys own tilt meters began to reverse showing
deflation. That observation prompted a debate about what was really going on inside the
volcano. Some geophysicists explained it in terms of a rising blob of magma that inflated
the mountain allowing the lower slopes to deflate once it was passed. There are situations
where if there is a rising diapere of magma there could be drawdown at some distance out.
Let's see, two nights ago we, our new tilt meters which are about four kilometers away
were showing a flat for the past week. They had just been put in and they started deflating
yesterday and I'm just taking that as evidence of a finite size plug gradually moving up
and if so it's about six kilometers deep. Right, I just can't evaluate that kind of
model with this kind of data. We don't have the stations far enough out in the right places
or enough of them. Others suggested no magma blob at all but a very long tube like a drinking
straw sucking up molten rock. One way of checking whether there really is a blob of magma under
a volcano is to set up a seismometer on either side and record the arrival of natural seismic
waves that one instrument registers the pure passage through the magma chamber. The Seattle
team tried this at Mount St. Helens. The initial analysis seems to suggest that there is no
large magma body down there that would behave at least or would distort the seismic waves
in the way we would anticipate in the conventional view of what a magma chamber does to seismic
waves. A refinement of the drinking straw is a two dimensional sheet of magma suggested
by Mount St. Helens data which showed inflation along one linear axis. The data from the Mount
St. Helens region is going to contribute to a revolution in the way we view tectonics
in the northwest. That revolution is beginning right now in that we've tended to view the
volcanoes as an isolated occurrence somehow related to the big picture of plate subduction
beneath the North American coast. The preliminary analysis that we've been doing here the last
few weeks suggests that there perhaps is a much more interesting and in terms of the
way we view volcanism in general, a unified story that's contained in the Mount St. Helens
data. Dr. Weaver's revolutionary concept is of a huge linear fault system across the
Pacific Northwest running generally parallel to the San Andreas and trying to slip just
like it but inhibited by numerous breaks and small spreading centers. Above each of them
a volcano. And some of the supporting evidence for that is just out there in the landscape.
If you look around each of the volcanoes they all sit in little holes. In other words the
land is higher to the east and the west than it is right where the volcano is. The volcanoes
sit in valleys. Graubens is what the technical term is. And those Graubens and the orientation
of those Graubens are all pretty much north-south. There's a big Graubens behind Mount Hood,
Mount Rainier, Mount St. Helens, Mount Baker, Mount Jefferson. And I think that those Graubens
are very consistent with this kind of geometry we now are beginning to envision. However,
these new theories of geophysics have yet to be reconciled with geochemistry. This is
the analysis conducted by a computer using x-rays once the sample has been re-melted
and prepared. Mount St. Helens ash is a daysite rich in silica. Magmas with less silica like
andesites would rather flow than explode. But the problem for the geophysicists is that
certain minerals can only be formed in magma when it's spent a long time sitting at fairly
shallow depths. And the computer finds those minerals in St. Helens ash. Many geochemists
feel that's a strong argument for the traditional blackboard drawing of a magma chamber. Some
even envision a grandmother magma feeding many volcanoes. Dr. Christensen believes the
chemical argument is compelling but complicated by historical data. Because we see in the
geologic history of Mount St. Helens andesites and other less silicic magnets, there must
be an interaction then between those magmas coming through from the depths probably rather
directly without much much residence time with other magnets that are probably residing
in the crust, equilibrating in the higher part of the crust for a longer period of time.
So it's going to be sort of a dualistic model that will ultimately emerge in my view. Researching
Mount St. Helens became a compromise between theorizing and hard practicalities like getting
up early to rig an aircraft with experimental gear. So far as the public was concerned,
scientists should have only one purpose, to predict eruptions and save lives. But raw
data were needed to make the most accurate predictions. So the scientists rushed to adapt
existing equipment to this unique situation. This tube will suck in gases from the volcano
as the aircraft flies through the plume. Inside, two instruments. One measures carbon dioxide,
the other sulfur dioxide. Those invisible gases along with clouds of steam had been
escaping from the vent at an enormous rate, often as much as 16,000 cubic tons a day.
On July 22, the dome was blown to bits at the start of a three hour eruption. Luckily,
no one was hurt. Only three days before this aircraft had recorded a sudden drop in the
ratio of carbon dioxide to sulfur dioxide. The scientists weren't sure, but thought this
might be a warning. Two weeks later, the ratio plummeted again, signaling a potential eruption
around August 7. At 1230 on the 7th, the warning got stronger. A harmonic tremor shook the
seismographs. Steve Malone studied the data and then sounded his first alarm.
Yeah, we just got a pretty good event coming in. We don't know whether it's right under
the mountain or not, but it just occurred, you know, 60 seconds ago. And tremor is building
up a bit. Yeah, I'd say get people out of there. Before two previous eruptions, harmonic
tremors were recorded. The latest vibrations were impossible to ignore, especially because
human welfare was at stake. So it looks like East Dome is 32.0 seconds. Same arrival time
at East Dome and SHW, which puts it then right smack beneath the crater. We talked to Craig
Weaver while the tremor was happening, and he felt confident enough to predict when the
mountain would explode. Based on the experience of the eruption on June 12 and July 22, over
we had about a six to nine hour lead time in the change in the physical parameter we
were measuring. That's why today here at three o'clock in the afternoon, we can say that
we feel there's a very strong probability for an eruption on Mount St. Helens tonight
in the next six hours. Weaver cut his interview short when new information which pinpointed
the location of the tremor source came through on his computer. It was time to act. Steve
Malone made a second warning call to headquarters. The tremor location and the gas ratio data
gave due cause to consider clearing the area and calling a public emergency. It was Bob
Christensen's decision, and the next day he described the situation. So at that point
we did contact our crews in the field, asked our ground crews to pull back from the area,
advised the forest service of our assessment of the situation and of our action with regard
to our own crews, and they decided to similarly advise all of their crews and people working
on forest service permits to withdraw from the immediate vicinity of the volcano. At
430, just 90 minutes ahead of his prediction, Craig Weaver watched it come true.
The
eruption went on until sundown. Another sky full of ash and pyroclastics. The next morning,
people in places like Yakima swept their yards clean for a fourth time and wondered when
it all would end. In her 19th century life, Mount St. Helens erupted like this for 22
years. And since half of the volcanoes in the Cascade Range are still active, future
generations will experience more major eruptions. What science has learned from Mount St. Helens
may not always apply to other volcanoes with their different geochemistries, but with each
successive eruption, scientists are improving their predictive capabilities and taking some
of the danger out of being close to these towering infernos of majestic force and beauty.
Thank you very much.
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