For the next hour or so, we're going to talk about Yellowstone.

Yellowstone, for those who haven't been there, it's in the northwest corner of Wyoming. About

1000 miles to the northeast of us here. And it's a pretty big park. It's about 9000 square

kilometers, or something like 3600 square miles. And for this Bay Area audience it might

be useful to look at Yellowstone relative to the Bay Area itself.

So that's Yellowstone National Park. The pink line in the middle is the caldera. We'll talk

more about that, but the outline of the park is here. So it stretches pretty much from

San Jose to San Pablo Bay and from Bolinas all the way over to Pittsburg.

It's a big park, and so when we talk about things happening at Yellowstone, you have

to think a little bit big.

Yellowstone is many things to many people. It of course is the first National Park in

the United States and it was the first National Park in the world and it started a trend of

humans trying to preserve their wild places for the benefit of future generations, and

so Yellowstone is a really special place just from that standpoint alone.

Of course it was preserved primarily because of the amazing geothermal features that are

there. The geysers.... pressurized boiling waters.... a boiling groundwater system.

Its spectacular Rocky Mountain scenery.

Its world-class fly fishing.

Its charismatic megafauna, as they are known. Lots of animals that have a place to breed

because we have such a special large, wild wilderness area for them to hang out in, where

they're free from hunters and other problems we often have with our civilized society.

Of course, more and more lately Yellowstone is starting to be known as the supervolcano.

And along with that we get a lot of crazy publicity, with articles in newspapers often

highly exaggerated and very frequently with a great deal of misinformation. So we're going

to try and cut through some of that today and see what really has happened at Yellowstone.

What's possible at Yellowstone.

And we're going to do that starting out with what we know about Yellowstone, and go through

a short history of the park and our understanding of the geology and volcanology of it. We'll

then talk about the primary geologic hazards and their relative probability. What's more

likely than other things? What's actually happening right now? How do we go about monitoring

Yellowstone? What are the techniques that we use and what do we learn? And then a little

more about the prospects for future activity. And any of those who want to stick around

we can do plenty of questions and answers if you're still awake.

Originally there wasn't a whole lot known about Yellowstone except the legends of the

Native Americans and the tall tales told by the trappers. Jim Bridger here talked of petrified

forest with petrified birds singing petrified songs. And he talked about rivers that raced

downhill so fast they turned warn on the bottom. But there wasn't a lot of cold hard facts.

Congress finally put together a whole series of expeditions to explore the various parallels

and Ferdinand Hayden was one of the people who ran the expedition that went through Yellowstone

in 1871. These were the groups that eventually got the U.S. Geological Survey started about

ten years later. Hayden brought along William Henry Jackson, a photographer, and Thomas

Moran, a painter, to help document what they found in the area. They collected samples,

they documented what they were seeing, and they did it both through the photography and

the painting. Those materials went back to Washington and they were really instrumental

in having Congress set aside Yellowstone as a national park.

Hayden also figured out quite a lot about the geology. He recognized that this was a

volcanic area. And so here as he was looking out from Mount Washburn over the surrounding

terrain he said : "..it is probable that during the Pliocene period the entire country drained

by the sources of the Yellowstone and the Columbia was the scene of as great volcanic

activity as that of any portion of the globe. It might be called one vast

crater, made up of thousands of smaller volcanic vents and fissures out of which the fluid

interior of the earth, fragments of rock, and volcanic dust were poured in unlimited

quantities .... Indeed, the hot springs and geysers of this region, at the

present time, are nothing more than the closing stages of that wonderful period of volcanic

action that began in Tertiary times."

So he recognized that this was a volcanic area. He recognized that it was not TOO long

ago in the geologic past that it was active. He put it a little bit older than it actually

is, and he also recognized that the hot springs and hot water are in some way related to the

volcanic system.

He and his colleagues camped on the north side of Yellowstone Lake and they experienced

another remarkable thing that we know about Yellowstone that there are a lot of earthquakes.

They experienced what we now call an earthquake swarm, where they were awakened in the middle

of the night by a series of shocks that woke them up, woke their horse up, and were shaking

the trees. And this is a little quote from Albert Peale, one of the people on the expedition.

Philetus Norris was the second superintendent at Yellowstone and he had the good fortune

of witnessing a hydrothermal explosion... sort of a "geyser gone bad," where rocks are

thrown out into the air. And he has a great quote here:

"The pool was considerably enlarged, its immediate borders swept entirely clear of all movable

rock, enough of which had been hurled or forced back to form a ridge from knee to breast high

at a distance of from 20 to 50 feet from the ragged edge of the yawning chasm."

So a very alliterative quote. This photo here is the hydrothermal explosion... something

that we'll talk later on tonight.

And then Thomas Jaggar who later founded the Hawaiian Volcano Observatory, went to a place

called Death Gulch, and saw seven grizzly bears that had imbibed a bit of poisonous

gas and he wrote:

"... the poor creatures are tempted one after another into a bath of invisible poisonous

vapor, where they sink down to add their bones to the fossil records of an interminable list

of similar tragedies, dating back to a period long preceding the records of human history."

These guys knew how to write back then. And they also made a lot of great observations.

So we knew that there was a lot of gas coming out at Yellowstone. There's earthquakes there,

there's hot springs. It's a big volcanic system. And so the stage was set...

It wasn't really though, until the 1960s when a modern perspective on Yellowstone came to

pass. This is Bob Christiansen (Chris). He works here. He's retired now, but works out

of the USGS in Menlo Park. And he spent much of his career working at Yellowstone. And

over here on the right is a picture of a thin section of the Lava Creek Tuff. Tuff is a

word for a kind of rock that had been known to be present all around the Western US. In

the 1950s, a guy named RL Smith, out of the USGS in Reston started doing a lot of work

on this particular type of rock. They're fragmental rocks, and they contain crystals and they

contain a lot of glass. And so in this example from Yellowstone, there's a little glass shard.

The glass is quenched silicate melt. It's the melt that's present in a volcanic eruption.

Bubbles form as gas comes out of solution when the eruption is starting. The material

is going into the air and the liquid quenches into glass. The bubbles break and form little

glass shards that are swept along in very violent, very hot clouds that fill in valleys

and are called "tuff," or called ignimbrite, also called pyroclastic flow. In this case,

there's such a thick amount of material that gets deposited and it's so hot, that it starts

to weld over time. It condenses. And all the little glass shards tend to get stretched

out and aligned. So the glass shards stretch out and you can see they wrap around this

crystal that is a much tougher, less pliable material. Anyway, these kinds of rock, the

welded tuffs, are evidence of massive volcanic eruptions. And Chris was able to find not

just one of these eruptions, which they knew about, but he found that there were three

separate eruptions that had happened relatively recently in the geologic past. There was the

Lava Creek Tuff that he mapped out in green here. This is a map of how it would have looked

640,000 years ago, right after the eruption of the Lava Creek Tuff. And preceding it was

the Mesa Falls Tuff, and before that was another, very, very large eruption, the Huckleberry

Ridge Tuff (purple). So the material comes out and moves down valleys and sometimes is

many hundreds of feet thick. And it completely fills in this area here, which is called the

caldera. Now, in the case of the Lava Creek Tuff, there's a thousand cubic kilometers

of material that got taken out of the ground, more or less, during that eruption. That's

enough material to bury the State of Texas about five feet deep. So it's a really big

amount and it all came out of Yellowstone. So when you take that amount of material out

of the ground, and you put it on top of the ground, you're left without a whole lot of

support for the ground surface, and it caves in. It's what we call a caldera. It's kind

of like a giant sinkhole. These are all the fractures that are associated with the formation

of this caldera. And all of this happened 640,000 years ago at Yellowstone. It's the

last really large eruption in this particular place.

I'm going to really focus in this talk on what the USGS did at Yellowstone, also some

other colleagues, but we're here in Menlo Park and I want to focus on some of the work

that's been done in this particular location. These guys right here had an amazing time

back in the 60s. On the right is a guy named Don White and on the left is his protégé

Bob Fournier, who's around and still lives in Portola Valley. We see him pretty frequently.

These guys were funded, as was Bob Christiansen by NASA to do studies at Yellowstone. And

they got the opportunity to study the geothermal system and to drill 13 science exploration

wells into the geyser basins at Yellowstone. First of all, that would be very difficult

to get permission to do today, so we're very grateful to them for what they were able to

learn, and for the samples that they collected in drillcores. We're able to use them today

because they're sitting in a warehouse in Denver. Anyway, these guys wrote a lot of

very classic papers on Yellowstone and a lot of what we know about geothermal energy production

really came from the work that was done back in the 60s. Here's an example of one of the

wells that they were drilling at the time.

So the next really remarkable thing about Yellowstone is that it moves up and down.

The ground surface is unstable and over time it moves. Bob Smith, who's down here, was

one of the party that came in and re-surveyed a series of roads that hadn't been surveyed

since the 1920s. Dan Dzurisin also worked on this topic. He's at the Cascades Volcano

Observatory, and here he's carrying this tripod that was used for leveling. Well Bob and his

colleagues re-occupied the benchmarks that were done previously in Yellowstone, and this

is a contour map that shows the number of millimeters that the area had gone up between

the 1920s and the 1970s. You can make out 500, 400, 700 is the largest one in the middle.

Here's the caldera, and so most of the activity here is going on in the caldera, and the maximum

uplift is about 700 mm in between these two areas that we call the resurgent domes, the

areas of maximum uplift within the caldera. So 700 mm is 70 cm, it's around 2 feet...

and so that had happened in those 50 years. This was really a remarkable observation and

something that we've been tracking ever since.

Bob Smith by the way, is one of our collaborators at the University of Utah through the Yellowstone

Volcano Observatory, and he's been working there on a very, very productive career for

many years.  

The last topic I want to bring up is the gas flux from Yellowstone, which is something

that we didn't know about until about ten years ago, at least in terms of its magnitude.

Here are my colleagues Bill Evans and Deb Bergfeld who are trying to figure out how

much gas is coming out of this particular pool at Terrace Springs. Over here is Cindy

Werner.  She's now at the Alaska Volcano Observatory, but she did her PhD at Yellowstone

using this, an accumulation chamber. Here's an example of some more modern ones. These

look at the flux of gas through the soil. If you have enough of them and you spend enough

time in the field, in her case, many, many summers, going to many places and running

grids, she was able to ascertain that a very high flux of gas is coming out of Yellowstone,

on the order of 45,000 tons of CO2 every single day. And that makes Yellowstone one of Earth's

most prolific natural sources of carbon dioxide, comparable to a pretty big coal-fired power

plant.  It's similar to Mount Etna and similar to what comes out of Kilauea in Hawaii.  Basaltic

magma, that's the kind that gets formed deep down in the Earth's mantle, contains a lot

of carbon dioxide when it comes up towards the surface. So when you see a lot of carbon

dioxide, that's a typical thing for a volcano, but its something we didn't necessarily know

was happening at Yellowstone, and by seeing that big number we can equate Yellowstone

with some of the other big volcanoes on Earth.

Let's step back a little bit and try to understand how this works on a larger scale.  This is

a map of the Western United States. (Shows Idaho and Wyoming, followed by , Oregon, Utah

and Nevada). This is a feature called the Snake River Plain.  Idaho Falls and Twin

Falls are there. The Snake River runs through it.  It is very productive farming country.

 It's also very flat.  Underneath all that flat terrain is a whole series of old volcanic

calderas very similar to Yellowstone.  Around 16 to 17 million years ago there was a rifting

in Northern Nevada.  There was the outpouring of the Columbia River basalts in Oregon and

Washington and there were calderas forming in northern Nevada, and these numbers, 16,

14, 12, 11, are a progression in the occurrence of these caldera systems that move towards