Thank you, Diana. It's a pleasure to be here.
This is quite a subject that I've only actually
been fully engaged in for a few years, but
it was my great privilege to be able to come
over to this program, and it's a very engaging
topic. So we'll jump right into it here.
I think all of you have probably heard of
the expression the 'Ring of Fire'. Basically
it's the Pacific Ocean, and the Pacific Ocean
is being swallowed on all sides by subduction
zones, and those subduction zones take material
down and in the earth it melts and comes up
to form arcs of volcanoes.
So we have a number of arcs around the Ring
of Fire, and I'm only showing the northern
part here because we're dealing with in the
U.S., and that includes the Cascades. Many
of you have probably been out there. The Aleutian
Island arc, which is part of Alaska. The Marianas
arc. There's a lot of active volcanoes in
Russia. And then Hawaii is a hot spot.
It's our job in the USGS to monitor these
for activity and try to predict eruptions.
We do that with a variety of instruments on
the ground, I'll touch on that briefly, and
we have scientists stationed at a number of
places. We have five volcano observatories.
That's what the VO stands for.
We have Alaska Volcano Observatory in Anchorage,
Cascade Volcano Observatory in Vancouver,
Washington across the river from Portland,
Long Valley Observatory and Yellowstone Volcano
Observatory, which are kind of virtual meeting.
We don't have staff at those locations. They're
in our headquarters center in Menlo Park.
Hawaii Volcano Observatory is literally right
on the volcano, and I hope you get a chance
to go see it.
Mariana Islands Volcano Observatory is a recent
addition, and that's actually run out of both
Alaska and Hawaii.
Now, most of the volcanic activity in the
"U.S." occurs in the Aleutian Island arc.
There's a lot of activity, lots of kinds of
volcanism you're not likely to ever be on
the ground around those volcanoes, so I'm
going to concentrate more on what has and
what could happen in areas that you're likely
to visit, in the Cascades and Hawaii.
We just touched on this briefly, but I'll
say in advance that much of our funding goes
to monitor these volcanoes. I think you all
know the Iceland incident that occurred where
Europe was shut down in airspace. That's the
same reason why we monitor these, because
they send up dangers, they send up ash into
the atmosphere, and that can shut down a jet
engine.
Here's an example. This is Cleveland Volcano
out in the middle of the Aleutians. This photograph
was taken by an astronaut on a space shuttle
as it went by.
We did not know this volcano was erupting.
It's so remote we don't have instruments on
it yet. He phoned down from space to the Alaska
Volcano Observatory and told them it was erupting.
It's one of the greatest phone calls.
We usually don't like to be surprised like
that, and that's why most of these, at least
the ones that are less remote, we have lots
of instruments so we can keep tabs on them.
But this ash going into the air, if a jet
flies through that, that can shut down your
engines. We had a near-disaster in 1989; cloudy
weather, KLM 747 jet, fully loaded coming
into Anchorage, flew right through a volcanic
ash plume and all four engines shut down.
They managed to restart two of them and land.
After that, Senator Ted Stevens said, "We
need to do a better job of monitoring volcanoes."
He got funding for the Alaska Volcano Observatory,
and we've been off and running since then.
That was one of the big triggers.
Well, keeping that in mind as we leave Alaska,
a lot of the air routes, you'd be surprised
to know, come right over the Aleutians. If
you're flying from Chicago to Tokyo, you may
actually fly right over there via the Great
Circle route. So you'd think it's way off
in the middle of the nowhere, but it's not.
And that's where we get the expression, "There
are no remote volcanoes," especially when
you have thousands of people in the air any
one time.
So as I say, we're going to more familiar
terrain. This is Mt. Rainier from Washington.
And since this is the 30th Anniversary of
the Mt. St. Helens eruption, the 1980 eruption,
I thought I'd go into that in depth. It produced
a variety of different kinds of phenomena.
I want to go through those, because that actually
did happen, and then we're going to look at
other Cascade volcanoes and I could show you
what might happen based on past geologic history.
But we'll use the 1980 eruption as an example
for that.
If you went to Spirit Lake in Washington in
the '70s, this is the view you might see:
a beautiful, symmetrical volcano. This was
called, I think, the Mt. Fuji of North America
or something. Little did we know the hidden
history of it until we started working on
it.
On March 20th, 1980, they started picking
up seismic signals from their instruments,
and then on March 27th, steam broke through
the snow and ice on the summit and blasted
this hole. You can see the snow is already
covered by a mantle of gray ash.
That was kind of the beginning of the unrest.
The volcanologists, I don't think there was
a Cascade Volcano Observatory yet, but early
in April, it steamed off and on, dirty ash-laden
steam coming out.
The other thing that started happening, here's
a shot from early April. Ominously, this bulge
started appearing on the north side of the
volcano. In hindsight, this, of course, is
a huge danger signal. At the time, though,
we didn't really realize what might happen.
They called it a 'cryptodome'. They thought,
'OK, magma's welling up underneath.' They
didn't realize what enormous pressure it could
be under.
So you can see a lot has happened here. The
snow is darkened by ash. Here's a little mudflow
or 'lahar', and we'll come back to these.
This theme we're going to come back to, the
heat from all this magma, this volcanism,
will melt snow and ice on the top, and that
will generate slurries, most of them small,
but some can be huge, that go down the mountain.
One of the themes of this talk is that's one
of our main threats in the Cascades in the
Pacific Northwest. Here's a little one that
started here and went down to here and stopped,
a mudflow or a lahar.
Here is late April. Look at that. You can
just see the bulge coming out, the ice was
cracking. It's sort of ironic; this guy's
umbrella, given what was going to happen,
is a little inadequate. Now, he's just shielding
himself from the sun, but I thought it was
kind of an ironic photo. I'm not sure what
he's doing. He's doing measurements. They
are measuring the dome, they are measuring
the gasses from afar.
The main headquarters for the study. This
was Cold Water Ridge just opposite the north
side of the volcano. As you can see, we had
a trailer set up there and they were doing
measurements and observations from there.
One of the young geologists there was David
Johnston. This shot was taken on May 17th,
1980. He was stationed up there. In fact,
he actually, I just heard this story, it was
another student, a grad student who was supposed
to be up there. He said, "I've got to go down
and talk to my thesis adviser. Can someone
take my place?" David Johnston volunteered.
After the eruption, well, we know obviously
he did not survive. There's never been any
trace of any of this stuff found, either his
body or the trailer or anything. Just to show
you how powerful that blast was.
So we all know what happened on May 18th.
Here is a classic shot, I think, from Austin
Post showing an ash column rising up, and
there's mudflows going down the side.
What I want to do here is I want to dissect
this eruption and show you the different processes,
and then again we can apply those to other
volcanoes as we go along.
This is the south side. The north side is
what gave way. You can see a funny little
cloud in the distance. That's part of the
landslide or maybe the blast that went off
the north side. And then we have this ash
going up.
First, I'm going to cover what happened to
the north face of the mountain, and then we'll
come back to the ash later.
Here are two stills from that famous movie
I'm sure you've all seen, and they nicely
show the process. First, the north side of
the mountain just gave way. That bulge made
it gravitationally unstable and it just went
down. This little ridge here, that's that
side of the mountain just flowing downhill.
When that happened, that exposed the magma
underneath, which was under tremendous pressure.
Then we have two things going on. We have
magma starting to shoot out, and this is all
of course a matter of seconds, here, and we
call that the 'lateral blast'.
Then we have another one going straight up,
and that's the 'vertical plume'. So the previous
slide, that's the vertical plume turns into
this. And then I'll show you what happens
with the lateral blast.
So we have landslide, lateral blast, vertical
ash cloud. I'm going to show you something
about the landslide first.
That's just a massive earth, 'debris avalanche'
was another name they have applied to it,
then it went down, and then the Toutle River
is just to the north and it kind of turned
the corner. It's the largest recorded landslide
in history in terms of the amount of material
it's removed.
This white stuff is part of a glacier, so
it just carried everything with it down there.
This picture was taken not long after the
event. They probably helicoptered in there.
And you can see, it's just this chaos. All
that new terrain, that's just mountainside
that's now been deposited at the bottom.
Looking downstream, probably from where we
just saw that last shot, looking down to the
west, this is actually years later, but it's
a good shot of the Toutle River Valley. You
can see this hummocky terrain.
And then where those ice blocks were are now
little lakes, so they of course melt, they
can't survive, and it just leaves little ponds.
We call those, well, 'kettles'. So the landslide
went out to about here, and then from there
on down was one of these lahars or mudflows,
and we'll come back to that.
The Toutle River at this point. This is three
years later, I think. It's starting to cut
a channel through there. A lot of material.
All right, so that was the landslide. Landslide,
the mountain gave way, came down, went part
of the way down the Toutle River Valley. That
unroofed the magma. The magma came out. All
that pressurized gas originally is, we use
champagne bottle, it's a very good analogy,
because the gas is dissolved in the liquid,
but you release the pressure, it all comes
out as bubble, and that provides a tremendous
force. That lateral blast came out to the
north and it just shredded everything. It
just denuded the landscape.
This is a helicopter view, but looking north,
there is Mt. Rainier. Here is Spirit Lake.
This all used to be forested, so the blast
was such it just tore the trees right out.
Some of them, it was so powerful they didn't
even have time to unroot themselves. They
were just snapped off at the base.
The trees, this kind of coloration in here
that you can see, that's all trees. And they're
large trees. That's the scale of this thing.
There are large, old-growth trees floating
in that lake to call it coloration. No sign
of trees up here. They've all been blasted
away to the north.
Near the edge of the blast where it's starting
to give out, the trees merely were knocked
over and stripped of all their branches. You
can see that here. They're snapped off, they're
stripped. And then finally, that blast surge
gave out, gave away energy, and it singed
these trees, but they were kept standing.
Now if you go to the David Johnston Visitor
Center now, you have to look hard. You see
little traces of this now, but of course,
this was Forest Service land, it came in and
salvaged all this timber. And then if you
look carefully, you'll see little remnants
of where the blast came out and kind of combed
the forest around following the contours.
All right, so we've covered the landslide,
the lateral blast. Now we're going to look
at the vertical plume. This is called a 'Plinian
eruption' because we think it's similar to
what Pliny the Elder saw in AD 79 when Vesuvius
erupted and buried the city of Pompei.
But the most powerful eruption sent the clouds
straight up 50,000, 60,000 feet, and that
has its own thing. We'll come to that in a
minute.
But the first thing that happens is some of
that ash falls out. You can see this kind
of fuzzy area. We call it 'column collapse'.
The ash comes down and then builds into what
we call a 'pyroclastic flow'. This is an important
term in volcanology because they're very common.
They're fragments of rock.
I better stop a minute and say what ash is.
It's little fragments of rock from these bubbles
blowing apart the magma. Each ash is kind
of the intersection of one of these gas bubbles,
these little ash particles. They tend to be
rather sharp. And of course, they're very
hard because they're made out of glass or
rock.
So that stuff's pouring up in the air. Well,
how can something like that float? Because
the hot gasses are just so buoyant, they just
carry all this ash up with them.
But not all of it. Some of it falls to earth,
and it's still got gas and it rides down the
mountainside and can go very fast. So we have
a pyroclastic flow starting here, roaring
down the mountainside. And that's something
you can't outrun. You can outrun a lava flow,
but you can't outrun a pyroclastic flow.
The most famous example is the town of Saint-Pierre
in Martinique, 1902. Mt. Pelée erupted, it
sent one of these things down and wiped out
a town of 30,000 people in a minute. Vesuvius,
the same thing happened and they were rapidly
buried by deep ash.
This next slide shows a better example. Now
this is later in the summer, a later eruption,
but it shows beautifully a pyroclastic flow.
We have ash going up, some ash coming out
and roaring down the mountainside at, I don't
know, let's say 60 miles an hour or something.
Now if you go up to that deposit later, there's
the deposit.
And look at the scale here. Here's the helicopter
and there's a person. You can see how big
those blocks are. How did they get out there?
Well, they're carried along on a cushion of
gas, so they're going along and makes these
beautiful forms.
Now if you go up there now, you can still
make these out, but you have to look carefully
because everything's now overgrown with vegetation.
But that's a real classic pyroclastic flow
made up of all these blocks that came out
with the magma. Now there's another kind that
I'll discuss later.
All right, so we've discussed three things
now. We'll go on to the fourth.
Here's the edge of that giant debris avalanche.
But the next thing that started happening,
and this is not a very good slide but it's
the only one I could find, water and mud are
pouring out of the end of that thing. So that
stuff comes out and it compresses and there's
a filter pressing going on. Mud and water's
pouring down the Toutle Valley, and this is
the start of a huge flood.
Now it's worse than a flood because it's got
so much ash in it that it has a lot of carrying
power. It's more like wet concrete, so anything
in its path is just swept up much easier than
if it were mere water.
Here is a logging camp farther downstream.
This mudflow or lahar came down and just carried
logs, transported trailers and so on, overran
roads, and severely damaged houses. I don't
think there was much in the way. Fifty-seven
people died in this eruption. I think most
of them were caught under the ash. I don't
think there was too many that were done in
by these mudflows.
However, the extent of these things is much
more far-reaching than, say, a lava flow,
and this is the thing that people are only
now starting to realize about volcanoes. Their
reach is longer.
All right, so going back to that ash that
went straight up into the air, that created
a huge ash cloud that the prevailing winds
carried east.
This shot was taken from Ephrata, Washington,
145 miles east of Mt. St. Helens, and you
can see what's going on. In this area, fine
ash rained down from the sky and coated everything
a little bit. Well, that may just be a nuisance,
but it can wreck your carburetor and engines
and stuff, so if it's thick enough it will
collapse roofs.
Near the volcano, well, there weren't houses
in there, but near the volcano it was feet
thick, and then at this point it's maybe a
centimeter or two or less, and by the time
it got to eastern Washington, Montana was
a dust bowl.
Here is an airport near Vancouver. Since I
was in Eugene, Oregon, I heard the eruption.
When I finally got up there that summer, everything
was gray. Even in Portland, there was this
gray film covering everything. It was very
eerie.
All right. After that eruption, we went into
another cycle. Now all that gas that came
out with the magma, that was released, and
then the next batch the magma came up with
much pour in gas, so it comes out as regular
viscous lava. The composition is so thick
as it comes out, it can't flow very well like
a nice Hawaiian flow. It comes up as a plug
or what we call a 'dome'.
In later May and June, this dome appeared
right in the same part of the vent where the
May 18th eruption occurred, and then it was
blown away by another eruption. This is the
July 22nd eruption, looks very similar to
the May 18th.
I saw this one. I was halfway between Portland
and Corvallis. I was driving south and saw
people on the overpass looking north. 'What
are they looking at?' I looked in my rearview
mirror and here's a mushroom cloud rising
from Mt. St. Helens.
That destroyed the dome that I just showed
you, because obviously more gas had built
up and then it just blew it apart, and then
another dome built. And then that one was
destroyed, and then another one. This is dome
number three, and this started the end of
the process. From now on, there's not much
in the way of ashy eruptions and it's mostly
dome growth.
Starting in late 1980 and then going on to
about 1986, this is what you would've seen
in about 1985 or something. Here is the crater
where that whole landslide, that's how much
was removed, and then you had this dome just
sitting in there slowly growing. By 1986,
they declared it over.
So this is, again, what Mt. St. Helens looked
back then. I think this shot was taken in
the 2000s.
So we thought maybe it was over, but it turned
out it was not. In March of 2004, an explosion
took place and a small ash eruption right
behind that dome that you just saw on the
last picture. More magma had come into the
system and it was trying to get out again.
What I'm showing you here is, this is a camera
that took a series of shots over time, you
can see the time lapse, and it shows this
thick magma coming onto the ground. Now we
call that a 'spine' because sometimes they
look spine-like. It's part of dome growth.
You can see the spine building, and then it
just kind of erodes in place and falls away.
That's pretty much indicative of what was
going on here.
Let's just go ahead into the next. Oh, here's
come another spine, and that's when the movie
ends. There were seven spines that have come
up since 2004.
Here's a shot from above using digital elevation
models and giving you kind of the same effect.
These thick rafts of magma are pushed out,
and this shows most of the growth up to, I
think, 2007. So that was going on there.
Now another thing, you might say, 'What's
this? Looks like lava flows.' This is a glacier,
and the cool thing about this, because this
was north-facing, this part of the crater
never got sun, so snow was able to build up
year after year and actually build a glacier,
and then finally that glacier started to flow.
I think this is the only double-ended glacier
in the world because you obviously need a
pretty unique setting to get that. These lobes
are now touching each other several years
later.
Again, there is a recent shot. Here's that
double lobe of glacier. Here's the dome steaming
quietly.
In 2008, we declared Mt. St. Helens dormant
again.
Oh, this is a shot of LANDSAT images. Now
in these kind of infrared images, vegetation
is red. Here is the volcano pre-1980. Then
right after the eruption, you can see the
devastation.
So that lateral blast came out and defoliated
this whole area. The landslide went to about
here. This white area is later pyroclastic
flows that I showed you a picture of, and
then the mudflow went downstream. And then
10 years later, you can see it's mostly re-vegetated
again. Of course, biologists are having a
field day here studying how stuff recolonizes.
It's a great experiment.
Now lest you think that Mt. St. Helens is
the only action we've had, most people here
weren't alive at this point, but in 1915,
Mt. Lassen in Northern California erupted.
This shot is from 40 miles away. Look at the
size of that plume. There was a series of
eruptions during that period. Of course, at
this point volcanology was in its infancy.
The Hawaiian Volcano Observatory is the nation's
first that had been founded three years before.
This tells us that there's a lot more going
on than just Mt. St. Helens. Geologists look
at these layers, and I'll show an example
in a minute, to figure out how frequently
volcanoes erupt. We monitor them for current
activity. It's also extremely important to
figure out their past history because that
gives us a sense of how frequent this is going
to happen, and we find that every volcano
has a different personality.
Here is Mt. St. Helens in the last 4,000 years.
Look how many times it's erupted. It's not
surprising that we saw it erupt in our lifetime.
And then all these others. What's another
common one that's had a lot of eruptions?
Lookie there, Mt. Rainier 2,000 years ago
had a variety of eruptions.
Now all these little symbols aren't the same,
as I'll show you. Some are lava eruptions,
some are big ash explosions, and so on. We're
going to go through these others next to show
you how different the personalities are.
But first, here's the St. Helens records.
Geologists dig cuts and go through all these
layers starting 30,000 years ago, starting
around here. Each one of these is an ash layer
from a previous eruption. We can date them
using isotopes.
So you can see that there's lots going on.
Here's 1800, 1400, 1200, before present, and
so on. Mt. St. Helens has had a lot of eruptions,
and very ash-rich ones, very explosive ones.
We have to do this basically for every volcano
that we're interested in in order to understand
the frequency of the eruption. So that's how
you make this diagram with those, that careful
geologic work.
As I say, as we do that, we noticed that Mt.
Rainier has been fairly active, too, but not
in the same way: mostly little lava flows
coming out, so not huge ash eruptions that
coat the landscape. However, look at the summit.
Look how much snow and ice is up there. You
get that hot rock mixing with that, what's
going to happen? Lahars. Mudflows. And look
at the elevation difference here, 14,000 feet.
So that's the story with Mt. Rainier.
Here's the view from Paradise Glacier. Look
at all the glaciers. I put this in, this is
Mt. Redoubt in Alaska 2009, just to show you
what one of these mudflows looks like farther
downstream. This is the kind of thing we would
expect Mt. St. Helens to produce. So in the
next slides, when I talk about mudflows going
down valleys, you can keep that image in your
head. That's about 10 meters thick worth of
dense mud.
For Mt. Rainier and other volcanoes, we make
a hazards map. So here is the summit, and
this explanation shows that it's almost all
about lahars. Well, OK, first you have an
area, this gray area. This is where you might
get lava flows and pyroclastic flows, those
hot, rubbly flows. But anywhere farther away
from that, it's the valleys that are under
threat.
In the hazards world, things that are less
hazardous occur more frequently, and things
that are more hazardous occur less frequently.
So we have small lahars maybe every 100 years
or so occurring just around the outskirts,
larger lahars that may go all the way down
the river occur every 100 to 500 years, and
then very large lahars, in this case could
go all the way to Puget Sound, every maybe
1,000 years.
So that's what you have to study with Mt.
Rainier because of all that snow and ice.
Now this is the town of Orting, which you
can see here in the valley, it's way down
there. The next shot is taken from Orting.
Again, look at the elevation difference here.
So how do you warn a community that lahar
is coming? You do a lot of public relations.
You do a lot of information dissemination,
handouts. You head community meetings. 'This
is what might happen. You might have, in this
case, say, 10, 20 minutes to get to higher
ground.' It's sort of like a tsunami warning.
You want the members of the community to be
aware that there could be a situation where
a mudflow's roaring down the valley and they
have to get up to higher ground. So you do
a lot of education on that.
And then we set up instruments called 'acoustic
flow monitors' which are aimed up the valley.
They can sense a wall of something coming
down the valley and they will trigger alarms.
We have a number of these acoustic flow monitors
set up along the valley upstream from Orting
and other communities that will warn them
if a mudflow is coming downstream.
The next volcano to the north, Glacier Peak,
has a very different personality, mostly ash
eruptions. It's one that you can see from
Seattle, but the range is so rugged you can
have trouble picking it out. So it's not a
very conspicuous volcano and it's heavily
eroded, but here's the hazard map for Glacier
Peak. It might get pyroclastic flows right
around it. Well, no one lives there, it's
a wilderness area, but mudflows can go down
and impact all of these communities.
Mt. Baker, to the north of that, near the
Canadian border, similar situation. Now Mt.
Baker actually has erupted relatively recently,
but like Rainier, it does these little lava
flows. Well, the lava flows themselves aren't
going to hurt anyone; it's the fact that they're
going to melt snow and ice and the snow and
ice is going to go down the valley.
Here's the Mt. Rainier hazard map. By now
these are all becoming very familiar to you,
I'm sure. Again, it's mostly the valley communities
that get impacted. In a way, it would be very
interesting to have an eruption there. It
would just be the fact that the threat of
the property downstream, not so much people
but property.
Mt. Hood, from the north. Now Mt. Hood is
going back, well, it's got a different personality
yet. Now, near the summit of Mt. Hood, here
is the summit, this is a rock called Crater
Rock.
Now you remember that movie I just showed
you of that lava coming out of the ground
those ponds? That's exactly how this was made,
and it was 200 years ago. So right at the
beginning of white people settling in the
Pacific Northwest, Mt. Hood had an eruption.
This thing came out, and then it generated
pyroclastic flows. Now this kind of pyroclastic
flow, the rock crumbles as it comes out. The
dome comes out and then fragments come off,
and because everything's hot, they ride that
cushion of air downstream.
If you go to Timberline Lodge there, you see
all this gray here, this gray blanket of rubble,
all of that came from up there, that rock.
All of that, much of it, is 200 years old.
So Timberline Lodge is in a pretty high-risk
zone because if an intrusion comes up again,
we may get a similar eruption and we may get
more hot pyroclastic flows coming down and
blanketing this flank of the volcano.
Here is the Mt. Hood hazard map. Now this
one's interesting because what they do is
they give predicted times that a mudflow is
going to reach an area. So here at Troutdale
near the Columbia River, they're saying it
will take about three and a half hours, but
up here, it's only going to take 30 minutes.
So I find that rather interesting. They modeled
that part of it.
Now we're engaged right now at making more
detailed maps of this and doing actually population
and property inventories of who lies in that
path. This is how emergency managers have
to think. Let's say you've got a retirement
home there. How are you going to evacuate
them in 30 minutes? So you have to think all
this through in advance. So they're having
meetings. Maybe someday they'll get to the
point of having actual drills. We know it's
going to happen. It's just a matter of when.
This is a little farther downstream, but in
the mudflow, it's near the Sandy River, looks
like a nice innocuous woods here and there
are houses nearby on this. See these boulders
here? That's the tipoff that not everything's
right here. And if you go to the nearby river
and look in the stream bank, giant boulders
here that were not carried by any normal stream.
It was one of those muddy flows that can pick
up anything in its path. This is the cross-section
through a lahar. One of the ones that came
down.
Now Lewis and Clark went up the Columbia River
in, whenever it was, 1803 or 1804, just after
the most recent eruption of Hood, and they
reported the Sandy River was running very
muddy. In fact, I think they even said it
was warm, so they got there only a year or
two after the eruptions. So it gives you a
sense of how recent things are here.
Here's another shot of that cross-section.
Here's a 200-year-old forest that was buried
by that lahar, and the trees are emerging
again. They were buried for a long time and
now they're emerging due to bank erosion.
That's the remnant of the forest that was
around just before Lewis and Clark came through.
Now we're going to jump way south. This is
Mt. Shasta in Northern California. It also
has its own personality, hasn't erupted in
a while, has little lava flows, but again,
you have that threat of lahars.
But it also has another one. If you notice
the stream, remember that shot looking down
the Toutle River, the hummocks? It took a
long time, but geologists finally realized
this is a remnant of a giant landslide from
Shasta. Look how far away the mountain is.
So Shasta underwent one of these giant debris
avalanches. When they get that big like St.
Helens or Shasta, we call them 'sector collapses'.
So like a third of the mountain just gives
away suddenly. And that avalanche, that landslide
went all the way out to here. That may not
be very frequent, but it's something to keep
in mind for the future.
Another kind of eruption that we haven't gone
into much are the really big ash eruptions.
This is Crater Lake in Oregon. In this case,
there used to be a beautiful symmetrical volcano
there called Mt. Mazama. 7,700 years ago,
there was so much magma underneath, the mountain
just foundered and collapsed in and all that
magma came out in the form of ash, and that
was a giant eruption.
You've probably heard the expression 'super
volcano'. This was a super volcanic eruption.
The Mt. Mazama ash which was found all over
the Pacific Northwest came out. There were
Native Americans that must have witnessed
this. That must've been amazing. This ash
came out, the volcano collapsed and produced
this beautiful Crater Lake.
Not much has happened here, but I use this
as an example of what's happened elsewhere.
Going back down to California, Long Valley
is about two hours south of Reno, where that
crook in the elbow of California is. Whereas
Crater Lake is a few miles across, this caldera
is about 20 miles across, so this was a much
bigger eruption.
Similar kind, 760,000 years ago, this, whatever
it was here, collapsed. They don't always
have to be beautiful volcanoes, but there
was a giant magma chamber, the top collapsed,
an enormous amount of ash came out. We call
it the Bishop Tuff. Many, many feet near the
volcano, I mean, tens of feet of ash came
out and just must have completely devastated
the landscape.
Well, today, we have Mammoth Mountain, which
is one of the most popular ski areas in the
United States. Here is the town of Mammoth
Lakes. There is geothermal stuff going on.
But it turns out the threat today is not another
giant eruption, and I'm going to come back
to this theme for Yellowstone, it's the little
things that tend to follow these giant eruptions.
In this case, north of the Long Valley caldera,
and here's Mammoth Mountain, there is a string
of little eruptions that have occurred. And
look at this timeline, 5,000 to present. All
this activity has occurred in the last 5,000
years.
They've used tree-ring dating to determine
that the most recent was actually August of
1450, I think it was. Late summer of 1450,
one of these things erupt. Well, what are
these? Well, they're little dome-like things,
they're little rhyolite plugs that come out.
They tend to be accompanied by some ash fall.
So they're local hazards. They would certainly
impact the town of Mammoth Lakes. If something
erupted under Mammoth Mountain, that would
of course be a big deal.
Here's one of these things close up. So this
is a different kind of eruption yet.
Long Valley is a very active area tectonically.
There's a lot going on. They tend to have
earthquake swarms. Every time you get an earthquake
swarm, you have to ask, is it tectonic or
is it volcanic? And sometimes they're not
sure. You have to look at the signals very
carefully. They came that close in the early
'90s to evacuating the town of Mammoth Lakes
because they thought there was going to be
another one of these eruptions, and then finally
the swarm died away.
Well, that's a good question, actually. One
could influence the other. There's one idea
that the crust is pulling apart there, allowing
space for the magma to come up, so it could
be the tectonic is aiding and abetting the
volcanic. Maybe some of these fluids are traveling
along faults. It's our most complex area to
study and it's fascinating. I went on a field
trip there last fall.
Now here's a view from the top of Mammoth
Lakes. One thing that's happening around the
ski area is CO2 gas is coming out and it's
causing tree die-off. You'd think, 'Well,
that's interesting.' Well, it can be deadly.
In fact, the gas comes up in the wintertime
and gets embedded in the snow, and if you
fall into a tree well, you can suffocate.
In fact, four people have died in the last
10 years, skiers, from getting suffocated
by CO2. That's actually the most fatalities
we've had for many a volcano in the United
States is right on Mammoth Mountain, and it
was all due to this invisible odorless gas.
So that's something we have to keep an eye
on and they keep readjusting the fencing around
these areas. Here's a sign near one of the
vents, "Stay away from here." Particularly
in the winter, you don't want to fall into
a hole and lose all your oxygen.
Going on to Yellowstone. Now Yellowstone gets
a lot of press because it's a super volcano,
yadda yadda yadda, but in fact, the last big
eruption was 600,000 years ago. We'll look
at some other things, but first, here is the
caldera. This is the section that collapsed
inward. It did generate an enormous eruption
2.1 million, 1.3 million, and 600,000 years
ago. Three really big ones.
Here is the ash from that. This is probably
one of the biggest in the United States. I
think this is the 600,000-year. This is how
far it got in North America. Look how big
the Mt. St. Helens eruption is. Not very big
at all, is it? Here's the Long Valley one
that I just told you about. That's a pretty
good size, but even Yellowstone is much bigger
than those.
When you see Discovery Channel stuff, that's
all based on this work. That's how we know
that there was giant eruptions, because the
ash traveled so far.
Today, there is a lot of activity going on.
It's the same thing at Long Valley. We've
got tectonic swarms and of course we have
geysers and a lot of hydrothermal activity.
So every one of these white dots is a recent
earthquake. We've got earthquakes swarms.
Again, you have to question, is it tectonic?
Well, Hebgen Lake had a 7.5 earthquake in
1959. That was definitely tectonic. There
was no magma involved. Another one in Norris
Geyser, 6.1. All these others, most of them
are probably tectonic, but some of them could
be volcanic.
The biggest threat today in Yellowstone is
not a super volcanic eruption, it's steam
blast.
These stars are little craters blown out in
the last, say, 500 years. This is something
we have to keep an eye on because I don't
think we really understand yet what's the
warning signs for these steam blasts. But
they're probably the biggest threat. That
and big earthquakes are what you're going
to encounter at Yellowstone much more so than
some gigantic eruption.
This applies to all calderas. You have the
big cap of magma underneath, and that pushes
up the rock, and then you have ring faults.
That's why you get these roughly circular
things. The water in the crust above it is
doing all sorts of things, going crazy because
it's so hot. There's a lot of hydrothermal
activity. Here's a swarm of earthquakes. Same
thing applies to Long Valley.
And then we use satellites. We can do very
sensitive measurements to the ground surface.
This bullseye here is a welt that came up
in 1996 to 2000. That could imply magma coming
to the surface. In fact, in North Sister Cascades,
we think that's what happened, a dike of magma
came up and then stopped.
Here, it's a little more complicated. It could
be all hydrothermal. But this is why we have
to keep close tabs on Yellowstone as well
because it's such a complex area. We're not
really sure what's going to happen next.
All right, for our last visit, I'm going to
go to Hawaii quickly, which is a completely
different animal. Here is the Big Island.
That's where all the volcanic activity is.
You can see Mauna Loa there.
Right now there are two eruptions occurring
on Hawaii. Here is Mauna Loa in the background.
Kilauea caldera's back there. There is a vent
emitting steam. This is the Puu Oo vent over
to the east and it's quietly erupting lava.
There is Puu Oo. The lava is coming out and
building these levees and then just slowly
going down here. A very quiet kind of eruption.
Very effusive. There's a lot of lava coming
out.
This is a shot taken this August with a new
thermal camera that we got. So Puu Oo is up
there and those lavas I just showed you are
up here, and then the lava comes down the
cliffs of the Palis, and then you get breakouts.
That's where the lava breaks out of the crust.
You can see the good red stuff. The thermal
camera just shows it more completely.
Well, it's been going into the ocean now for
a long time. This whole eruption started in
1983. What the new wrinkle is it's started
edging eastward and there's a fault riding
here that's starting to direct the lava east
right into a subdivision. Well, back in '83,
the Royal Garden Subdivision was completely
overrun, and now the threat is slowly returning
because it's slipping eastward again, just
at a lower level, and it's starting to impact
these houses down here.
Here's some shot of lava crossing the road.
Obviously you can outrun this kind of thing,
but it's not a good thing if you're a house
to encounter, and there's nothing you can
do about it.
Then over at Kilauea, here is the main caldera.
The HVO is right over here and there is the
Visitor Center over here. A vent blew out
about two years ago and started emitting steam,
and the initial throat-clearing of that vent
was quite explosive and powerful.
Here is the visitor's overlook to look down.
This is Halemaumau crater inside the larger
Kilauea. So this was a visitor's overlook.
Fortunately, this explosion occurred in the
middle of the night, so no one was hurt. But
you can see it completely destroyed it, and
these are just blocks thrown up by all that
steam pressure.
Now, no lava's come to the surface, but we
can use that same caver to look down into
the hole, and that's the surface of a lava
lake. Now, sometime in the future, I'm sure
that lake level will rise and will once again
get lava pouring out on the surface of Kilauea
like we have many times.
Now just to the west of there is the giant
shield volcano Mauna Loa. You can just look
at it and see that there's been a lot of eruptions
here. That's probably a bigger threat right
now because there's subdivisions. This is
called the 'southwest rift'. There's subdivisions
up there that's been built since the last
eruption, which I think is 1984, and then
there is the main highway here. Stuff can
be cut off here. This slide is showing how
that could get impacted.
We expect this to happen, erupt again, even
quite likely in our lifetime, so we need to
be ready for it. It's not something that's
going to be that sudden, but it will be destructive
nonetheless.
All right, the last couple of slides just
showing how we monitor things. We put seismographs.
Seismicity of a volcano is the best indication
that something's going to happen. The magma's
rising, the earth shakes. So it's like a stethoscope.
We have stethoscopes monitoring each volcano.
And a whole variety of other instruments,
but this is the main one.
Here is a volcano, Augustine, in Alaska, showing
all the instruments around it. So we don't
want to be caught by surprise. We also have
GPS, which shows the volcano swelling. That's
another good indicator that magma is rising
to the surface.
Here is Tom Murray, Director of the Alaska
Volcano Observatory, and this bank of instruments,
each screen is tied to a different volcano
out in the Aleutians. Thanks to satellites,
we can do all this remotely and keep tabs
on things.
Here is a seismograph when quiet, and this
is during an eruption. This is Augustine 2006.
To do this, we're trying to institutionalize
more our technique for monitoring. We are
starting in 2011 the National Volcano Early
Warning System, and we hope to get funding
from Congress on this, increase the monitoring,
there's a lot of volcanoes that are under-monitored,
and work with communities more, create a 24/7
watch office, data-clearing house, fund academic
researchers. So we hope to get that going.
That will be our initiative for the next 20
years.
If you want more information, here is our
website. This one might be too heavy to lift,
but if you want to really know more about
the St. Helens eruption or the more recent
one, this just came out. This is a USGS professional
paper. It's got a lot of good material in
here.
For general reading on the Cascades, I really
like this book, "Fire Mountains of the West".
Now this guy, this is the third edition. They
used to call it "Fire and Ice". It's all about
the Cascades, much of what I talked about
here. It's very readable. He draws on good
scientific information. This edition came
out in the last five years. But it's a good
read if you want to read more about volcanic
activity in the Cascades. It's scientific,
but it's readable.
So I think that's it, and I can entertain
questions. Yes.
Audience 1: Are there any potential at all
for volcanoes in the Eastern United States?
Bill Burton: No.
Audience 1: Sometimes we have earthquakes.
Bill Burton: Well, If we run the movie forward
100 million years, I'll say yes, because sooner
or later the Atlantic Ocean floor will break
off and start subducting under eastern North
America, and that will generate a line of
volcanoes. But again, we're talking probably
100 million years from now. That's usually
what happens.
Now, I'm trying to think if there's any other.
I really can't think of anything else. I mean,
we could get surprised, but there are no hot
spots. That's the other way to punch up, get
in the middle of the continent, is a hot spot.
And I forgot to mention Yellowstone is a hot
spot. So there's a hot spot moving across
the western U.S. But offhand I can't think
of anything else right now. You have to go
to the Caribbean.
Now, that doesn't mean we're not under threat.
For instance, the Azores in the Canary Islands
are volcanic islands off Europe and Africa.
If one of those volcanoes had a sector collapse,
and it's possible, that would generate a tsunami
that could seriously hurt the east coast of
the U.S. That is a viable scenario.
Of course, the Iceland volcano could erupt
again and if the wind is right could carry
ash over the Northeast U.S. So there are scenarios.
Once again, we were surprised that not a very
major volcano could do such damage. But if
everything lines up right, it's possible.
Yeah. There's one of these ash layers called
the Bandelier Tuff and it's, I don't know,
100-feet thick. I think that is the largest-known
in geologic history. If you take that volume
and put it back, that's how much was erupted.
Eruptions around the world can affect us.
Tambora in 1815 caused The Year Without a
Summer in the United States. They're more
effective if the volcanoes are near the equator,
because the way the global atmosphere currents
go, that will tend to get spread out to the
north.
High-latitude volcanoes, it's hard for them
to affect areas farther south in latitude,
but Tambora 1815, gigantic eruption. The one
in Toba 75,000 years ago was so big, some
people think it nearly wiped out the human
race. So a volcanic eruption is capable of
global effects.
But remember our rule, the bigger the event,
the less frequent it is. So we at least have
that going for us.
[Laughter]
Anyone else? Yes.
Audience 2: How was Mt. St. Helens being monitored
before the eruption?
Bill Burton: No, there were some seismographs.
I don't really know. There were some seismometers
around it. At that time, we didn't have GPS,
so I think they did tiltmeters. They had tiltmeters
on it and they had some seismometers. They
were monitoring it; it's just not to the same
level we are today.
Now lately they've developed these things
called 'spiders'. They're complete instrument
packages and they can drop down from helicopters
and sit on the ground. After an eruption,
when you can't land in an area but you want
to put some instruments, you can lower these
things. And they're solar-powered.
And now we're trying to make them smart. So
if you have a network of these things, if
one goes out here, it doesn't affect all the
ones behind it. They re-route their signal
through others and get it back to the observatory.
All those signals have to go back to, in that
case, Cascade Volcano Observatory, which was
founded in '82 or '83, I think. Every observatory
has those banks of monitors that you saw looking
at a volcano.
Anyone else? OK, thanks a lot.