[Coyote howl, music, and the sound of a geyser erupting]
You're watching Yellowstone InDepth.
Think of Yellowstone, and most people think of geysers.
And while over three million people come to Yellowstone
National Park each year to see the park's geysers, hot springs,
steam vents, and mudpots, many don't know that the heat
fueling these wonders is coming from a volcano,
possibly the largest on Earth.
A volcano that lies directly beneath their feet.
The Yellowstone supervolcano, hot enough to fuel 10,000
hot water features that have been spewing,
hissing and surging for hundreds and thousands of years.
A volcano whose restless shifting triggers thousands
of small earthquakes in the park each year.
A volcano that has had eruptions thousands
of times more powerful than Mount St. Helens.
A volcano that could, in an instant, change our world forever.
The Yellowstone volcano is one of our planet's restless giants.
For scientists, the question is not one of whether it will erupt again,
but when. In 2003, rangers at the Norris Geyser Basin noticed a
rapid rise in ground temperatures. In the same area, previously
dormant geysers suddenly sprang to life and others boiled dry.
Park Ranger Denise Herman: "I was walking the trails on the morning
of July 11th, talking with visitors, when I was in the area of the
Corporal Geyser. We noticed that the area had been heating up
because we noticed that the trees were emitting a maple syrup smell,
which meant the heat was cooking the sap in the trees themselves.
It looked like there might be some heat in the trail itself,
so I took some temperature readings, and just a few centimeters below
the surface the temperature of the earth was 200 degrees Fahrenheit."
At that altitude, 200 degrees is the boiling point of water.
The park decided to temporarily close the trail to
keep people from getting burned.
The rangers reported what they saw to Hank Heasler, Yellowstone's
park geologist. With the help of the Yellowstone Volcano Observatory,
he set up a grid of ground monitoring equipment to study the changes.
Park Geologist Hank Heasler: "There are three indicators we look
at for an imminent volcanic eruption in Yellowstone.
The first is increased earthquakes in one particular area.
The second is increased ground deformation, the ground rising
on the order of feet to perhaps yards in one particular area.
And then also, changes in thermal activity,
geyser basins becoming hotter and producing more gas."
Jake Lowenstern: "At Yellowstone, all of those things are
happening all of the time. We know, though, that this sort
of thing at Yellowstone has been going on for thousands of years.
But it doesn't always mean, or in fact, it almost never means,
that we get an eruption here. So we get all of this geological
activity that in some places might mean an eruption was coming
but in Yellowstone it just means that's the way the place works."
But Yellowstone still delivers some surprises.
Several years ago, U.S. Geological Survey researchers
mapping the floor of Yellowstone Lake made a series of stunning finds:
large underwater hot springs, submerged earthquake faults,
underwater spires, and a submerged dome 100 feet tall and
almost half a mile long. These discoveries, along with the
increased activity at Norris, generated a great deal of interest
in the media and raised concerns among some park visitors
as to the safety of visiting Yellowstone park.
But with such a large volcano underlying Yellowstone,
scientists have learned to expect the unusual.
At Norris, the flurry of activity continued for several weeks.
Then, as suddenly as it began, the disturbance disappeared.
For now, Yellowstone's volcano slumbers in relative peace.
Park Geologist Hank Heasler: "Yellowstone is truly a magical
place and that magic is rooted in the Yellowstone volcano.
We have a very good volcano monitoring system in Yellowstone
and we'll know if the volcano, and when the volcano,
starts to become excited. So, until that time,
Yellowstone is a great place to come and visit and
experience the beauty of the volcano directly."
One day, Yellowstone's restless giant will reawaken.
It will change Yellowstone as we know it. But in the meantime
and for the duration of our lives and generations to come,
this giant will be a creative force, not a destructive one.
The Yellowstone volcano breathes life into the geysers,
the hot springs, the mudpots. It fuels the geologic wonders
that have amazed countless generations and will thrill countless more.
And it is alive right now.
Right beneath our feet.
[music]