America's Dangerous Volcanoes
It has been thirty years since Mount Saint Helens reawakened, but what other volcanoes pose the threat of lava flows, toxic gases, volcanic ash, and mudflows? Bill Burton of the U.S. Geological Survey Volcano Hazards Program discusses the efforts being made by the federal government to monitor volcanoes in the Pacific Northwest, Hawaii, and Yellowstone for eruptive activity.
Bill Burton: 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.
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.
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.
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.