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As continents shift and clash,

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volcanoes erupt, glaciers grow

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and recede, the Earth's crust

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is carved in countless,

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fascinating ways, leaving a

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trail of geological mysteries

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behind.

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And one of the greatest is right

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here, at Yellowstone National

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Park in Wyoming.

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This is one of the world's most

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geologically active places,

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shaken by up to 5,000

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earthquakes every year, and

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with more geysers and hot

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springs than in the rest of the

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world combined. Why is

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Yellowstone so active? How did

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it form? And why here in the

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heart of the Rockies?

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Scientists studying Yellowstone

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are uncovering a violent past.

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Carved by water, crushed by

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ancient glaciers and blasted by

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the biggest volcanic eruptions

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ever known on the planet.

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And even today, Yellowstone is

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one of the most dangerous

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places on Earth.

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How The Earth Was Made 01x08
Yellowstone
Original Air Date on March 31, 2009

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== sync, corrected by <font color=

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Yellowstone National Park is one

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of the most amazing places on

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Earth, and it's unique.

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It contains some of America's

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most stunning scenery and

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wildlife that attracts three

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million tourists a year.

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To understand where Yellowstone

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came from, and why it is so

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active today, we need to take a

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continent and deep into the

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Earth's interior.

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Yellowstone sits 8,000 feet up

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on a remote mountain plateau,

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primarily within Wyoming, but

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stretching into parts of Idaho

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and Montana.

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The park covers 3,468 square

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miles, 63 miles north to south

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and 54 miles east to west.

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And it's on top of one of the

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world's most unusual and

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deadliest geological structures.

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>> What's unusual about the

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park? Are the wildlife unusual?

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No. Is the wide open space

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unusual? No. You've got it all

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over the western US. What's

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unusual? It's a very unusual

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geology that created the park.

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Yellowstone was founded as the

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world's first National Park

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because of the geology.

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>> It's this strange geology

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that attracts teams of

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scientists to the park.

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Their task, to piece together

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the story of the incredible

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processes that built this

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unique, extraordinary landscape

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by digging deep into

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Yellowstone's past.

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>> The geologic history of

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Yellowstone goes back to the

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formation of the North American

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continent. Some of the rocks in

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Yellowstone are 2.8 to 3.2

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billion year old rocks, some of

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the oldest in North America.

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>> Only by traveling back into

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the past can we figure out why

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in this particular location

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there are 2,400 miles of

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rivers, more than 300 waterfalls

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and the world's greatest

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concentration of 10,000 hot

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water springs, bubbling

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mud-holes, gas vents and

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geysers. What do these features

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reveal about this landscape, and

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how it was formed?

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The investigation begins at

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Yellowstone's star attraction,

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Old Faithful.

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It's a key clue to what's going

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on underneath the surface.

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Located in the southwest of

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Yellowstone Park, the geyser

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puts on an explosive display

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every 90 minutes or so, blasting

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out thousands of gallons of

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scalding hot water.

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>> Yellowstone is like no other

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place on Earth, there is so

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much heat coming out here.

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It's really a singular

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phenomenon.

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Well, after about a 90-minute

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nap, Old Faithful has roared

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back to life. It wasn't actually

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napping, it was recharging, and

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the temperature of the water was

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increasing, the system was

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pressurizing. Beneath Old

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Faithful is a rather complex

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plumbing system, filled with

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caverns and conduits and

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constrictions.

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>> Rainwater saturating the

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ground around the geyser slowly

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fills its underground reservoir.

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Hot rocks below ground heat the

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water under pressure for around

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90 minutes. Suddenly, some water

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spurts through a tiny, five inch

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wide crack in the rocks.

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This causes a drop in the

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pressure within the water

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chamber. In an instant,

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thousands of gallons of water

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are turned to steam and blasted

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up into the air.

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>> When the pressure builds up

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enough, steam bubbles start

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rising to the surface, the

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system depressurizes, and a

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full eruption can occur.

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>> Old Faithful shows that rocks

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below the surface are very hot.

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Scientists find clues to a

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violent past 34 miles southeast

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of the hot springs, on the

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shores of a circular lake

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called Indian Ponds.

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>> As a field geologist, my job

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is to basically be a rock

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detective. And so I try to

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determine what their origin is

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and what the history is of that

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particular rock. There we go.

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OK, now, in this particular

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case-- Let's look at this. This

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rock, when it started, it was

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just a loose sand, you could

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just put your fingers through

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it.

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>> The solid boulder is formed

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from millions of individual

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grains of sand.

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Microscopic analysis reveals the

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grains have been cemented

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together by chemicals and

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pressure deep under the ground.

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But how did the rock get to the

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surface?

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Morgan has chemically dated the

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rocks and discovered that 3,000

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years ago, the boulder was

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blasted out of the ground by

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the hot water explosion of a

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gigantic geyser.

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>> You would see boiling water,

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rock fragments and fine muddy

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material being ejected up into

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the air as high as 3 to 5,000

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feet. And then, at some point,

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material would start raining

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down from this explosion column.

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Now, you wouldn't want to be

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standing next to one of those.

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>> Indian Ponds is the crater

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that the geyser left behind.

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But it is dwarfed by the crater

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Morgan has found at Mary Bay in

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Yellowstone Lake.

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Morgan has dated this geyser

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explosion to 13,000 years ago.

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>> So here we are in the middle

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of Yellowstone Lake, and it's,

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as you can see, a beautiful day

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and it's nice and placid, but on

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the floor of Yellowstone Lake,

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it's anything but quiet.

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>> Morgan's research proves that

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geysers were exploding around

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the lake, and even under the

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water, between 13,000 and 3,000

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years ago. And their size

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suggests that whatever was

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powering them was huge.

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But is it still active today?

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A clue comes from underwater

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vents at the bottom of the

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geyser crater.

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They pump out vast quantities of

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hot water and gases.

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To find out what's creating the

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gases, Jake Lowenstern and his

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assistant collect samples from

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the hot springs in the center

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of the park.

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The funnel they use is designed

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to collect up gas bubbles

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before they reach the surface,

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so that they're not contaminated

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by ordinary air.

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>> So we let it sit for five

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minutes and let the oxygen get

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out?

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>> Yeah.

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It is a very complex mix of

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gases and--but we have a--a lot

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of tools that we can use to try

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to unravel this rather, uh,

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complicated information.

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So we'll look at all of the

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gases that are coming out, we

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can learn about the different

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kinds of rocks beneath

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Yellowstone and try to

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understand how things might be

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changing from--from week to

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week, or year to year or--or

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decade to decade.

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>> Analysis of the gases reveals

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that they are a mix of carbon

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dioxide, sulphur dioxide and

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hydrogen sulphide. It is the

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same mix that is found coming

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out of volcanoes.

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But the final clue to what's

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actually going on underground

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is found on the edge of the same

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hot springs.

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>> So these are quartz crystals

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that we collected on the side

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of the pool there. This stuff is

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what remains. It gets tossed up,

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and forms a little burr around

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the side of the cr--pool and

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it's all beautiful little quartz

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crystals. Some of them have a

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little bit of iron staining and

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other things, um, but most--most

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of them are--are nice, uh,

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shades of yellow and--and clear.

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>> Quartz crystals like these

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can only have formed as a hot,

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molten rock lava flow slowly

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cooled after being erupted onto

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the surface from deep

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underground. So the crystals are

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clear evidence that under the

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springs is a volcano.

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Yellowstone's hot water features

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all point to one conclusion.

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Yellowstone must be powered by

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the heat of a volcano.

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Geysers only erupt if the rocks

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are hot enough to turn water

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into steam. Gases from

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underwater have the same

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composition as those from

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volcanoes. Quartz in the hot

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springs must have come from

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volcanic lava.

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>> There is an immense amount of

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energy coming out of the ground

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that's expressed by the geysers,

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the mud pots, the hot springs

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and the steam vents. Where's all

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that heat coming from? It's

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coming from the molten rock

285
00:11:43,862 --> 00:11:45,596
associated with the Yellowstone

286
00:11:45,697 --> 00:11:47,498
volcano.

287
00:11:47,599 --> 00:11:48,699
>> But that leaves a big

288
00:11:48,767 --> 00:11:51,402
question unanswered. In this

289
00:11:51,503 --> 00:11:53,671
gentle rolling landscape,

290
00:11:53,772 --> 00:11:58,409
where's the volcano?

291
00:12:06,329 --> 00:12:08,055
Yellowstone's unique volcanic

292
00:12:08,056 --> 00:12:09,957
geology is potentially deadly

293
00:12:10,025 --> 00:12:13,394
dangerous. It makes it crucial

294
00:12:13,462 --> 00:12:14,762
to monitor what's happening

295
00:12:14,830 --> 00:12:16,530
under the ground.

296
00:12:16,565 --> 00:12:18,365
>> The Yellowstone volcano is a

297
00:12:18,400 --> 00:12:19,834
very, very active volcanic

298
00:12:19,901 --> 00:12:22,536
system, and so it really

299
00:12:22,571 --> 00:12:25,105
requires observation.

300
00:12:25,207 --> 00:12:27,007
Everything that we do here has a

301
00:12:27,108 --> 00:12:28,476
research component, but it also

302
00:12:28,577 --> 00:12:29,844
has a volcano monitoring

303
00:12:29,911 --> 00:12:32,112
component and, uh, you know,

304
00:12:32,214 --> 00:12:34,081
if--if--if activity picks up

305
00:12:34,115 --> 00:12:35,416
here, we're going to want to

306
00:12:35,484 --> 00:12:36,484
know something about the

307
00:12:36,551 --> 00:12:39,887
plumbing system beneath us here.

308
00:12:39,921 --> 00:12:41,288
>> To try and predict when

309
00:12:41,389 --> 00:12:42,823
Yellowstone's hidden volcano

310
00:12:42,891 --> 00:12:44,725
will erupt in the future,

311
00:12:44,826 --> 00:12:46,994
scientists study its geological

312
00:12:47,028 --> 00:12:49,830
past.

313
00:12:49,898 --> 00:12:51,732
>> Part of our task is to look

314
00:12:51,833 --> 00:12:54,435
at the landscape and read the

315
00:12:54,469 --> 00:12:57,171
geologic story, and there are so

316
00:12:57,205 --> 00:12:59,540
many clues and so much evidence

317
00:12:59,574 --> 00:13:01,542
here to look at that it's a

318
00:13:01,543 --> 00:13:06,780
fascinating place to work.

319
00:13:06,815 --> 00:13:07,982
>> Scientists began

320
00:13:08,083 --> 00:13:09,717
investigating Yellowstone even

321
00:13:09,784 --> 00:13:11,352
before it became the world's

322
00:13:11,419 --> 00:13:15,456
first national park 1872.

323
00:13:15,490 --> 00:13:16,924
But observations of this

324
00:13:16,958 --> 00:13:18,459
astonishing land began

325
00:13:18,493 --> 00:13:26,200
long before that.

326
00:13:26,301 --> 00:13:28,068
Dating ancient arrowheads shows

327
00:13:28,136 --> 00:13:29,470
that Native Americans first

328
00:13:29,571 --> 00:13:34,742
lived here 11,000 years ago.

329
00:13:34,843 --> 00:13:36,310
Their legends of Yellowstone's

330
00:13:36,411 --> 00:13:37,678
angry spirits who made the

331
00:13:37,746 --> 00:13:39,446
ground tremble were passed on to

332
00:13:39,481 --> 00:13:41,582
early explorers such as Lewis

333
00:13:41,683 --> 00:13:45,219
and Clark.

334
00:13:45,287 --> 00:13:46,587
Later reports from trappers,

335
00:13:46,655 --> 00:13:48,589
explorers and mountain men like

336
00:13:48,657 --> 00:13:51,025
John Colter and Jim Bridger told

337
00:13:51,126 --> 00:13:53,093
of geysers that fired 70 feet

338
00:13:53,128 --> 00:13:55,296
into the air and springs so hot

339
00:13:55,397 --> 00:13:57,264
that meat was readily cooked in

340
00:13:57,299 --> 00:14:00,634
them.

341
00:14:00,669 --> 00:14:01,735
But these were thought to be

342
00:14:01,770 --> 00:14:04,638
tall tales until the 1860s,

343
00:14:04,673 --> 00:14:06,574
when geologists investigated and

344
00:14:06,675 --> 00:14:08,275
found that the lava flows and

345
00:14:08,310 --> 00:14:10,744
hot vents were signs of volcanic

346
00:14:10,845 --> 00:14:20,087
activity.

347
00:14:20,121 --> 00:14:21,655
But something clearly wasn't

348
00:14:21,756 --> 00:14:24,024
right. Nobody could actually

349
00:14:24,092 --> 00:14:27,895
find the Yellowstone volcano.

350
00:14:27,996 --> 00:14:29,563
>> We say that Yellowstone is

351
00:14:29,664 --> 00:14:31,465
one of the world's most active

352
00:14:31,533 --> 00:14:34,034
volcanoes. People come out here,

353
00:14:34,102 --> 00:14:35,469
visitors, other scientists, and

354
00:14:35,537 --> 00:14:36,737
they say, "What do you mean?

355
00:14:36,838 --> 00:14:38,939
I--I don't see a smoking

356
00:14:39,007 --> 00:14:41,208
volcano, I don't see a big

357
00:14:41,309 --> 00:14:44,378
steep volcanic, uh, uh,

358
00:14:44,479 --> 00:14:46,447
crater," all the things that one

359
00:14:46,481 --> 00:14:48,182
normally thinks of for an active

360
00:14:48,216 --> 00:14:50,117
volcano.

361
00:14:50,185 --> 00:14:51,752
>> So, without obvious signs of

362
00:14:51,820 --> 00:14:54,388
a volcano, scientists hunted for

363
00:14:54,456 --> 00:14:58,025
other clues.

364
00:14:58,093 --> 00:14:59,526
They would find them in the

365
00:14:59,561 --> 00:15:01,395
sweeping forests of Lodge Pole

366
00:15:01,463 --> 00:15:04,665
pines. These are the only plants

367
00:15:04,733 --> 00:15:06,200
that thrive on the poor soil

368
00:15:06,267 --> 00:15:07,735
that comes from a particular

369
00:15:07,802 --> 00:15:14,575
type of lava called rhyolite.

370
00:15:14,643 --> 00:15:15,909
And Yellowstone's constant

371
00:15:16,011 --> 00:15:17,845
plagues of mosquitoes also

372
00:15:17,912 --> 00:15:19,747
reveal the presence of that same

373
00:15:19,848 --> 00:15:23,651
rhyolite lava.

374
00:15:23,752 --> 00:15:25,886
>> The rhyolites are--are not

375
00:15:25,920 --> 00:15:29,356
very permeable, and so in--it

376
00:15:29,391 --> 00:15:31,558
creates these little ponds of

377
00:15:31,626 --> 00:15:34,662
water that never go away, and

378
00:15:34,729 --> 00:15:36,563
those are wonderful breeding

379
00:15:36,631 --> 00:15:39,366
grounds for mosquitoes. There

380
00:15:39,434 --> 00:15:40,801
are a lot of mosquitoes, if you

381
00:15:40,835 --> 00:15:42,169
can't see them, flying around my

382
00:15:42,203 --> 00:15:43,837
head.

383
00:15:43,905 --> 00:15:45,105
>> So the pine trees and the

384
00:15:45,173 --> 00:15:46,840
insects both indicate that

385
00:15:46,908 --> 00:15:48,342
there's a lot of rhyolite in

386
00:15:48,376 --> 00:15:51,278
Yellowstone. And that's

387
00:15:51,346 --> 00:15:53,714
important, because rhyolite lava

388
00:15:53,748 --> 00:15:55,382
creates incredibly violent

389
00:15:55,450 --> 00:15:58,886
volcanic eruptions.

390
00:15:58,920 --> 00:16:01,088
>> It's much more like a bread

391
00:16:01,189 --> 00:16:03,257
dough. It's about a thousand to

392
00:16:03,291 --> 00:16:05,159
a million times thicker or more

393
00:16:05,193 --> 00:16:06,894
viscous. If we put a bunch of

394
00:16:06,928 --> 00:16:08,929
gas in it, we can have a very

395
00:16:08,997 --> 00:16:11,465
explosive eruption.

396
00:16:11,533 --> 00:16:13,267
>> But if rhyolite lava is that

397
00:16:13,334 --> 00:16:16,203
explosive, how big a bang did

398
00:16:16,271 --> 00:16:30,384
it produce?

399
00:16:30,452 --> 00:16:32,453
To find that out, scientists

400
00:16:32,554 --> 00:16:34,188
looked, not inside Yellowstone

401
00:16:34,289 --> 00:16:36,457
Park, but in a faraway river

402
00:16:36,558 --> 00:16:42,963
valley at Meadow Creek, Wyoming.

403
00:16:42,997 --> 00:16:44,264
Cutting down through the land

404
00:16:44,332 --> 00:16:45,999
over millions of years, the

405
00:16:46,067 --> 00:16:48,001
river has exposed an unusual,

406
00:16:48,103 --> 00:16:50,270
thin layer of black rock in the

407
00:16:50,338 --> 00:16:53,907
cliff face.

408
00:16:54,008 --> 00:16:55,642
A nearby road cutting lets

409
00:16:55,744 --> 00:16:57,177
investigators examine the

410
00:16:57,245 --> 00:17:05,085
mysterious, dark rock.

411
00:17:05,186 --> 00:17:06,286
>> If you look at this sample,

412
00:17:06,354 --> 00:17:08,455
um, in detail up close, you can

413
00:17:08,556 --> 00:17:09,623
see that here's a pumice

414
00:17:09,724 --> 00:17:12,359
fragment, these--these red

415
00:17:12,427 --> 00:17:13,827
fragments here are--are little

416
00:17:13,895 --> 00:17:16,530
rock fragments, and, uh, if we

417
00:17:16,631 --> 00:17:17,965
were to make a thin section of

418
00:17:17,999 --> 00:17:19,099
this rock and look at it under

419
00:17:19,167 --> 00:17:20,734
the microscope, you would in

420
00:17:20,802 --> 00:17:23,504
fact see compressed, uh, glass

421
00:17:23,538 --> 00:17:25,806
shards.

422
00:17:25,907 --> 00:17:27,007
>> The black layer that

423
00:17:27,075 --> 00:17:29,076
geologists call obsidian is

424
00:17:29,144 --> 00:17:32,346
actually a type of glass.

425
00:17:32,447 --> 00:17:33,981
It's crucial evidence that the

426
00:17:34,082 --> 00:17:35,916
rocks and soil here came out of

427
00:17:35,984 --> 00:17:40,254
a volcano.

428
00:17:40,355 --> 00:17:42,156
Because obsidian is forged when

429
00:17:42,223 --> 00:17:44,424
boiling hot ash and gas rapidly

430
00:17:44,492 --> 00:17:49,563
cool under great pressure.

431
00:17:49,597 --> 00:17:51,031
And that's just what happens

432
00:17:51,065 --> 00:17:52,866
when hot volcanic clouds roll

433
00:17:52,934 --> 00:17:56,036
out across the landscape.

434
00:17:56,104 --> 00:17:58,105
The obsidian forms in the very

435
00:17:58,139 --> 00:17:59,940
bottom layers, cooled from

436
00:17:59,974 --> 00:18:01,508
below and crushed by the weight

437
00:18:01,576 --> 00:18:07,047
of hot debris on top.

438
00:18:07,115 --> 00:18:08,649
The ash layer that crushed the

439
00:18:08,683 --> 00:18:10,217
obsidian at Meadow Creek is

440
00:18:10,285 --> 00:18:13,287
still visible today.

441
00:18:13,321 --> 00:18:14,855
>> Its base is characterized by

442
00:18:14,923 --> 00:18:16,824
this very thick, dense, obsidian

443
00:18:16,858 --> 00:18:18,959
as--as the flow came to rest and

444
00:18:19,027 --> 00:18:21,061
was compacted. And then, above

445
00:18:21,129 --> 00:18:23,030
this dense glass layer as it

446
00:18:23,097 --> 00:18:25,032
grades upwards into a tan sort

447
00:18:25,099 --> 00:18:26,834
of region and continues up for

448
00:18:26,868 --> 00:18:28,402
about an additional 30 feet. And

449
00:18:28,503 --> 00:18:30,504
then up on top of that, as it's

450
00:18:30,572 --> 00:18:32,105
exposed today, modern soil has

451
00:18:32,140 --> 00:18:33,640
formed and we can see growing up

452
00:18:33,675 --> 00:18:34,675
there various sorts of

453
00:18:34,742 --> 00:18:36,143
vegetation, trees and grasses

454
00:18:36,211 --> 00:18:39,580
and things of that sort.

455
00:18:39,647 --> 00:18:40,581
>> Studying the mineral

456
00:18:40,682 --> 00:18:42,216
composition of the ash proved

457
00:18:42,317 --> 00:18:43,750
that it came from an ancient

458
00:18:43,785 --> 00:18:46,019
volcanic blast in Yellowstone

459
00:18:46,054 --> 00:18:48,589
Park.

460
00:18:48,690 --> 00:18:50,490
And there's only one way that so

461
00:18:50,558 --> 00:18:51,959
much ash could have been

462
00:18:52,026 --> 00:18:53,861
blasted so very far away from

463
00:18:53,928 --> 00:18:56,864
its source. The eruption must

464
00:18:56,931 --> 00:18:59,099
have been larger, far larger,

465
00:18:59,133 --> 00:19:02,469
than anything ever seen by man.

466
00:19:02,503 --> 00:19:05,572
So big that scientists now label

467
00:19:05,673 --> 00:19:08,909
it as a supereruption.

468
00:19:08,943 --> 00:19:11,011
>> We're looking at this deposit

469
00:19:11,045 --> 00:19:12,479
from a supereruption, and yet

470
00:19:12,580 --> 00:19:14,281
we're over 50 miles from the

471
00:19:14,315 --> 00:19:18,852
source of the--of the eruption.

472
00:19:18,920 --> 00:19:20,754
>> The geologists have recreated

473
00:19:20,822 --> 00:19:22,222
what must have happened here on

474
00:19:22,323 --> 00:19:23,590
the day that Yellowstone

475
00:19:23,658 --> 00:19:26,660
exploded. Incandescent

476
00:19:26,728 --> 00:19:28,462
avalanches of ash raced out of

477
00:19:28,496 --> 00:19:32,132
the park in all directions.

478
00:19:32,200 --> 00:19:33,300
So this is traveling

479
00:19:33,401 --> 00:19:35,102
at very high velocity, um,

480
00:19:35,136 --> 00:19:37,271
easily over 100 miles per hour,

481
00:19:37,305 --> 00:19:39,273
across the land surface

482
00:19:39,307 --> 00:19:40,841
and obliterating everything

483
00:19:40,909 --> 00:19:41,842
in its path.

484
00:19:41,910 --> 00:19:42,943
It was extremely hot

485
00:19:43,044 --> 00:19:44,011
when it arrived here,

486
00:19:44,045 --> 00:19:46,046
and--perhaps as hot as--as

487
00:19:46,114 --> 00:19:48,682
1,500 degrees Fahrenheit, two--

488
00:19:48,750 --> 00:19:50,484
twice a pizza oven, I mean, it's

489
00:19:50,551 --> 00:19:52,286
just very hot.

490
00:19:52,387 --> 00:19:53,654
>> So what would it have been

491
00:19:53,721 --> 00:19:55,022
like to be standing on this

492
00:19:55,123 --> 00:19:56,657
spot hundreds of thousands of

493
00:19:56,758 --> 00:19:59,393
years ago, on the day when the

494
00:19:59,494 --> 00:20:01,395
Yellowstone ash cloud roared

495
00:20:01,496 --> 00:20:03,931
over the horizon?

496
00:20:03,998 --> 00:20:05,299
>> The--the impact of this

497
00:20:05,400 --> 00:20:07,401
would--would be, uh, absolutely

498
00:20:07,468 --> 00:20:08,535
unimaginable. It would be--

499
00:20:08,569 --> 00:20:09,269
Yeah.

500
00:20:09,304 --> 00:20:10,003
>> I think you would be

501
00:20:10,038 --> 00:20:12,172
disarticulated, burned and--and!

502
00:20:12,206 --> 00:20:13,674
unrecognizable, and it would be

503
00:20:13,741 --> 00:20:15,575
very difficult to find any of

504
00:20:15,677 --> 00:20:19,546
you.

505
00:20:19,580 --> 00:20:21,181
>> All of the evidence about the

506
00:20:21,215 --> 00:20:22,749
size of the supereruption

507
00:20:22,817 --> 00:20:24,384
helped solve the mystery of the

508
00:20:24,485 --> 00:20:27,721
missing volcano. Scientists

509
00:20:27,755 --> 00:20:29,456
realized that the supereruption

510
00:20:29,490 --> 00:20:31,358
was so enormous that it must

511
00:20:31,392 --> 00:20:32,826
have blown the volcano to

512
00:20:32,860 --> 00:20:34,061
pieces.

513
00:20:39,467 --> 00:20:41,468
Swarms of mosquitoes show that

514
00:20:41,569 --> 00:20:43,036
explosive rhyolite lava

515
00:20:43,104 --> 00:20:45,672
underlies parts of the park.

516
00:20:45,740 --> 00:20:48,108
Obsidian glass 60 miles away

517
00:20:48,176 --> 00:20:49,743
reveals that ash flows spread

518
00:20:49,811 --> 00:20:52,713
for miles around Yellowstone.

519
00:20:52,747 --> 00:20:54,281
And thick layers of debris

520
00:20:54,382 --> 00:20:56,216
confirm how gigantic an

521
00:20:56,284 --> 00:21:00,487
explosion this must have been.

522
00:21:00,555 --> 00:21:02,122
The problem now is the explosive

523
00:21:02,190 --> 00:21:03,824
legacy that the supervolcano

524
00:21:03,891 --> 00:21:06,660
left behind. Because a deadly

525
00:21:06,761 --> 00:21:09,162
danger still lurks here, hidden

526
00:21:09,197 --> 00:21:11,278
deep under the ground.

527
00:21:17,988 --> 00:21:19,322
For nearly a century after

528
00:21:19,390 --> 00:21:20,957
Yellowstone National Park was

529
00:21:20,991 --> 00:21:23,059
established, nobody realized one

530
00:21:23,160 --> 00:21:27,163
astonishing fact.

531
00:21:27,231 --> 00:21:29,399
That the park is located inside

532
00:21:29,433 --> 00:21:30,800
one of the biggest volcano

533
00:21:30,868 --> 00:21:35,071
craters on Earth.

534
00:21:35,139 --> 00:21:37,140
It wasn't until the late 1960s

535
00:21:37,241 --> 00:21:38,608
that American geophysicist

536
00:21:38,676 --> 00:21:40,710
Robert Christiansen realized

537
00:21:40,778 --> 00:21:42,345
that rock formations he had

538
00:21:42,413 --> 00:21:44,514
been studying for several years

539
00:21:44,615 --> 00:21:45,615
all around the edges of the

540
00:21:45,683 --> 00:21:48,151
park in fact formed a giant

541
00:21:48,252 --> 00:21:52,422
circular ridge.

542
00:21:52,523 --> 00:21:53,756
He compared his findings on the

543
00:21:53,791 --> 00:21:55,592
ground with a series of NASA

544
00:21:55,659 --> 00:21:58,695
pictures taken between 1966 and

545
00:21:58,796 --> 00:22:02,966
1970, confirming that the ring

546
00:22:03,067 --> 00:22:05,435
was the rim of a giant crater,

547
00:22:05,503 --> 00:22:10,473
45 miles across.

548
00:22:10,508 --> 00:22:11,941
Parts of the crater rim are

549
00:22:11,976 --> 00:22:14,477
still clearly visible today,

550
00:22:14,512 --> 00:22:16,346
but the other edge is almost out

551
00:22:16,413 --> 00:22:23,419
of sight.

552
00:22:23,521 --> 00:22:25,388
Finding the crater coincided

553
00:22:25,422 --> 00:22:26,589
with another scientific

554
00:22:26,690 --> 00:22:28,124
discovery in a totally different

555
00:22:28,158 --> 00:22:32,595
part of the country.

556
00:22:32,663 --> 00:22:34,697
In California, scientists

557
00:22:34,765 --> 00:22:36,332
identified a strange, thin

558
00:22:36,400 --> 00:22:38,234
layer of ash buried underneath

559
00:22:38,335 --> 00:22:41,304
the modern-day soil.

560
00:22:41,338 --> 00:22:42,972
The ash matched material from

561
00:22:43,040 --> 00:22:45,875
the Yellowstone crater.

562
00:22:45,943 --> 00:22:47,610
Dating the soil layers proved

563
00:22:47,678 --> 00:22:50,146
that the ash arrived 640,000

564
00:22:50,214 --> 00:22:53,483
years ago. Scientists at last

565
00:22:53,551 --> 00:22:55,251
had a date for the Yellowstone

566
00:22:55,286 --> 00:23:03,359
supereruption.

567
00:23:03,394 --> 00:23:05,461
Ash was later found all over the

568
00:23:05,529 --> 00:23:07,997
western US, confirming the huge

569
00:23:08,098 --> 00:23:12,068
size of the eruption.

570
00:23:12,102 --> 00:23:13,903
At least 80 times the size of

571
00:23:13,938 --> 00:23:15,939
the 1883 explosion that

572
00:23:16,006 --> 00:23:17,440
destroyed the island of

573
00:23:17,474 --> 00:23:27,617
Krakatoa.

574
00:23:27,651 --> 00:23:30,353
And 2,500 times bigger than the

575
00:23:30,387 --> 00:23:32,555
1980 eruption of Mount St.

576
00:23:32,656 --> 00:23:37,727
Helens.

577
00:23:37,795 --> 00:23:39,796
The almost unimaginable size of

578
00:23:39,830 --> 00:23:41,264
the Yellowstone blast means

579
00:23:41,298 --> 00:23:43,366
that scientists now call it a

580
00:23:43,434 --> 00:23:50,473
supervolcano.

581
00:23:50,541 --> 00:23:51,641
But that creates another

582
00:23:51,709 --> 00:23:54,177
mystery. In this peaceful

583
00:23:54,244 --> 00:23:56,913
landscape, where is the steaming

584
00:23:57,014 --> 00:23:59,015
hot crater that the volcano must

585
00:23:59,083 --> 00:24:01,551
have left behind?

586
00:24:01,619 --> 00:24:03,086
>> Today, when you're looking

587
00:24:03,153 --> 00:24:04,554
out across the landscape, you

588
00:24:04,622 --> 00:24:06,723
see rolling hills and--and

589
00:24:06,790 --> 00:24:08,725
trees, so, obviously, there's

590
00:24:08,826 --> 00:24:10,426
not a big hole left in the

591
00:24:10,461 --> 00:24:12,261
ground, um, from the eruption of

592
00:24:12,329 --> 00:24:14,263
the--of the Yellowstone volcano.

593
00:24:14,331 --> 00:24:16,899
So something else has happened.

594
00:24:17,001 --> 00:24:18,835
One of the first processes was

595
00:24:18,902 --> 00:24:20,470
infilling with all sorts of

596
00:24:20,537 --> 00:24:22,905
volcanic lava flows, and if you

597
00:24:23,007 --> 00:24:24,007
look just down from the

598
00:24:24,074 --> 00:24:25,375
landscape toward those trees,

599
00:24:25,442 --> 00:24:27,443
you'll see one of the oldest

600
00:24:27,544 --> 00:24:30,179
lava flows that happened after

601
00:24:30,247 --> 00:24:33,916
the 640,000 year eruption.

602
00:24:33,984 --> 00:24:35,284
>> Over hundreds of thousands of

603
00:24:35,352 --> 00:24:36,986
years this flow has weathered

604
00:24:37,054 --> 00:24:38,888
into soil and been covered with

605
00:24:38,922 --> 00:24:42,925
trees.

606
00:24:42,993 --> 00:24:44,727
But elsewhere in the park are a

607
00:24:44,828 --> 00:24:47,096
different type of lava deposit,

608
00:24:47,164 --> 00:24:49,732
still bare of vegetation because

609
00:24:49,800 --> 00:24:51,467
this lava was still erupting up

610
00:24:51,535 --> 00:24:55,905
until about 100,000 years ago.

611
00:24:56,006 --> 00:24:57,440
The later lava was far less

612
00:24:57,508 --> 00:25:00,076
explosive and more runny, and

613
00:25:00,144 --> 00:25:03,813
cooled slowly.

614
00:25:03,881 --> 00:25:06,082
It smoothed the harsh, volcanic

615
00:25:06,183 --> 00:25:07,884
landscape into Yellowstone's

616
00:25:07,918 --> 00:25:16,025
softer countryside.

617
00:25:16,093 --> 00:25:17,994
That made Yellowstone, at first,

618
00:25:18,062 --> 00:25:22,899
more tranquil.

619
00:25:23,000 --> 00:25:24,267
But there's evidence here that

620
00:25:24,334 --> 00:25:25,802
the land was soon buried once

621
00:25:25,869 --> 00:25:28,538
again, this time by freezing

622
00:25:28,605 --> 00:25:30,807
snow and ice.

623
00:25:32,348 --> 00:25:34,197
The ice that polished the rocks,

624
00:25:34,222 --> 00:25:35,670
has a story to tell.

625
00:25:37,589 --> 00:25:38,789
It offers crucial evidence

626
00:25:38,814 --> 00:25:40,290
about volcanic forces

627
00:25:40,310 --> 00:25:41,420
still shaping the park

628
00:25:41,445 --> 00:25:42,645
to this day.

629
00:25:46,856 --> 00:25:48,389
Its tale unfolds through the

630
00:25:48,491 --> 00:25:51,459
tiniest of clues.

631
00:25:51,527 --> 00:25:53,161
Scratches on the rocks reveal

632
00:25:53,195 --> 00:25:57,799
which way the ice was moving.

633
00:25:57,833 --> 00:25:59,467
They show that glaciers always

634
00:25:59,535 --> 00:26:02,170
slid the same way, outwards

635
00:26:02,204 --> 00:26:04,105
and downwards from an icecap at

636
00:26:04,173 --> 00:26:08,076
the heart of the park.

637
00:26:08,110 --> 00:26:09,711
The only conclusion is that

638
00:26:09,745 --> 00:26:11,713
something pushed up Yellowstone

639
00:26:11,814 --> 00:26:13,548
Park so much higher than the

640
00:26:13,649 --> 00:26:15,283
surrounding hills that glaciers

641
00:26:15,351 --> 00:26:28,797
formed on the top.

642
00:26:28,864 --> 00:26:31,065
But what force could possibly be

643
00:26:31,133 --> 00:26:32,667
powerful enough to have raised

644
00:26:32,701 --> 00:26:34,502
Yellowstone's peaks up into the

645
00:26:34,603 --> 00:26:45,780
air?

646
00:26:45,848 --> 00:26:47,248
The first clue to help answer

647
00:26:47,316 --> 00:26:48,316
that question comes from

648
00:26:48,417 --> 00:26:49,684
Yellowstone's numerous

649
00:26:49,752 --> 00:26:52,120
earthquakes.

650
00:26:52,154 --> 00:26:53,955
>> When the ground deforms, it

651
00:26:54,056 --> 00:26:55,223
creaks and groans like a

652
00:26:55,291 --> 00:26:56,758
Stradivarius violin. And the

653
00:26:56,792 --> 00:26:57,759
creaks and groans are

654
00:26:57,793 --> 00:26:59,694
essentially earthquakes.

655
00:26:59,762 --> 00:27:00,962
>> The quakes are recorded by

656
00:27:01,030 --> 00:27:05,333
seismometers all over the park.

657
00:27:05,401 --> 00:27:06,701
>> The earthquake monitoring is

658
00:27:06,769 --> 00:27:08,036
a critical part of the picture

659
00:27:08,137 --> 00:27:09,871
because it's basically--it's the

660
00:27:09,972 --> 00:27:11,873
stethoscope that we have to

661
00:27:11,941 --> 00:27:14,309
really see and sense the--the

662
00:27:14,410 --> 00:27:22,350
heartbeat of the system.

663
00:27:22,384 --> 00:27:23,918
>> Smith is investigating a

664
00:27:23,986 --> 00:27:29,257
puzzling geological mystery.

665
00:27:29,291 --> 00:27:31,159
Yellowstone has up to 5,000

666
00:27:31,193 --> 00:27:33,661
earthquakes a year, even though

667
00:27:33,729 --> 00:27:35,296
it's in the stable heart of the

668
00:27:35,364 --> 00:27:38,800
North American continent.

669
00:27:38,868 --> 00:27:40,602
Scientists needed to know what

670
00:27:40,703 --> 00:27:42,170
was happening underground to

671
00:27:42,238 --> 00:27:46,241
shake the park so much.

672
00:27:46,308 --> 00:27:47,976
To find out, they plotted the

673
00:27:48,077 --> 00:27:49,878
precise locations and depths of

674
00:27:49,945 --> 00:27:57,852
earthquakes under the ground.

675
00:27:57,887 --> 00:27:59,587
So, why are there so many

676
00:27:59,622 --> 00:28:04,993
quakes?

677
00:28:05,060 --> 00:28:06,527
The answer had to wait until the

678
00:28:06,595 --> 00:28:08,796
mid-1980s, when ever more

679
00:28:08,898 --> 00:28:10,598
powerful computers first let

680
00:28:10,699 --> 00:28:14,936
scientists see into the Earth.

681
00:28:14,970 --> 00:28:16,771
Seismic waves spreading out from

682
00:28:16,805 --> 00:28:18,239
earthquakes travel rapidly

683
00:28:18,274 --> 00:28:20,575
through cold rock, but slow down

684
00:28:20,609 --> 00:28:23,144
when the rocks are hot.

685
00:28:23,212 --> 00:28:25,046
The varying wave speeds can be

686
00:28:25,147 --> 00:28:26,848
translated by computers into

687
00:28:26,882 --> 00:28:28,683
color 3D images, revealing

688
00:28:28,784 --> 00:28:30,952
exactly where hot rock lies

689
00:28:30,986 --> 00:28:32,487
under the ground.

690
00:28:33,135 --> 00:28:34,403
>> Seismic waves propagate

691
00:28:34,428 --> 00:28:35,957
through the Earth, just like

692
00:28:35,982 --> 00:28:37,636
X-rays go through a body.

693
00:28:38,032 --> 00:28:39,577
And so we the same physics

694
00:28:39,602 --> 00:28:42,441
to reconstruct the structure

695
00:28:42,466 --> 00:28:44,002
of the geology of the Earth

696
00:28:44,027 --> 00:28:45,074
beneath us.

697
00:28:45,075 --> 00:28:46,509
>> The seismic waves have

698
00:28:46,610 --> 00:28:48,177
outlined the park's underground

699
00:28:48,245 --> 00:28:50,346
structures, revealing a graphic

700
00:28:50,447 --> 00:28:51,781
history of what's happened

701
00:28:51,815 --> 00:28:55,051
under Yellowstone.

702
00:28:55,085 --> 00:28:56,853
They reveal this gigantic

703
00:28:56,887 --> 00:28:58,688
reservoir of molten rock which

704
00:28:58,789 --> 00:29:00,523
created Yellowstone's crater

705
00:29:00,591 --> 00:29:02,792
when lava erupted out, and the

706
00:29:02,860 --> 00:29:04,794
ground above collapsed into the

707
00:29:04,862 --> 00:29:08,698
space left behind.

708
00:29:08,765 --> 00:29:10,700
And the seismic waves still slow

709
00:29:10,767 --> 00:29:12,535
down under Yellowstone today,

710
00:29:12,603 --> 00:29:14,136
showing that the magma chamber

711
00:29:14,171 --> 00:29:16,873
still lurks under the park.

712
00:29:16,974 --> 00:29:19,609
It's more than 30 miles long, 25

713
00:29:19,710 --> 00:29:21,410
miles wide and ten miles in

714
00:29:21,512 --> 00:29:24,780
depth. But its size alters from

715
00:29:24,848 --> 00:29:26,682
year to year as it fills or

716
00:29:26,783 --> 00:29:28,818
empties with semi-liquid rock at

717
00:29:28,852 --> 00:29:31,020
an incredible 1,500 degrees

718
00:29:31,088 --> 00:29:33,856
Fahrenheit. This is the hidden,

719
00:29:33,924 --> 00:29:35,358
beating heart of Yellowstone

720
00:29:35,392 --> 00:29:38,027
Park. The way it moves deforms

721
00:29:38,095 --> 00:29:40,263
the ground above, explaining the

722
00:29:40,297 --> 00:29:41,831
fault lines and the earthquakes

723
00:29:41,899 --> 00:29:45,034
they produce. And its heat

724
00:29:45,102 --> 00:29:46,469
ultimately powers all of

725
00:29:46,537 --> 00:29:47,670
Yellowstone's hot water

726
00:29:47,738 --> 00:29:55,478
pools and geysers.

727
00:29:55,579 --> 00:29:57,647
Subterranean Yellowstone is

728
00:29:57,714 --> 00:30:00,182
giving up its secrets.

729
00:30:00,217 --> 00:30:02,084
Seismographs record thousands of

730
00:30:02,119 --> 00:30:04,854
earthquakes in the park. And the

731
00:30:04,922 --> 00:30:06,489
evidence of earthquake waves

732
00:30:06,557 --> 00:30:08,024
reveals a massive magma

733
00:30:08,125 --> 00:30:09,559
chamber miles under

734
00:30:09,626 --> 00:30:12,828
Yellowstone's surface.

735
00:30:12,896 --> 00:30:13,529
But the Yellowstone

736
00:30:13,564 --> 00:30:15,565
investigation is far from

737
00:30:15,632 --> 00:30:18,034
finished, because there's

738
00:30:18,101 --> 00:30:20,036
evidence of another, even more

739
00:30:20,103 --> 00:30:22,371
monstrous sized structure under

740
00:30:22,472 --> 00:30:23,874
the park.

741
00:30:31,716 --> 00:30:33,250
By the beginning of the 21st

742
00:30:33,351 --> 00:30:34,684
century, scientists

743
00:30:34,719 --> 00:30:36,319
investigating how Yellowstone

744
00:30:36,354 --> 00:30:38,522
was made had images of what lay

745
00:30:38,589 --> 00:30:41,625
under the park.

746
00:30:41,659 --> 00:30:44,027
But there was a problem.

747
00:30:44,095 --> 00:30:45,829
Technology only allowed a view

748
00:30:45,897 --> 00:30:46,930
of a few miles below the

749
00:30:46,998 --> 00:30:50,033
surface. Then, as more and more

750
00:30:50,101 --> 00:30:51,835
data was fed into more and more

751
00:30:51,936 --> 00:30:54,371
powerful computers, there was a

752
00:30:54,438 --> 00:30:57,107
breakthrough.

753
00:30:57,208 --> 00:30:59,543
In April 2006, geologists

754
00:30:59,577 --> 00:31:01,211
published new diagrams of

755
00:31:01,312 --> 00:31:03,914
hot structures, far deeper under

756
00:31:03,948 --> 00:31:06,917
the park, and computers painted

757
00:31:06,951 --> 00:31:09,386
more detailed pictures.

758
00:31:09,487 --> 00:31:14,191
The results were startling.

759
00:31:14,225 --> 00:31:16,026
Investigators saw for the first

760
00:31:16,127 --> 00:31:17,861
time the sleeping monster that

761
00:31:17,929 --> 00:31:24,467
lies below Yellowstone Park.

762
00:31:24,502 --> 00:31:26,570
Snaking down hundreds of miles

763
00:31:26,637 --> 00:31:29,206
into the Earth, far deeper than

764
00:31:29,273 --> 00:31:30,841
the relatively shallow magma

765
00:31:30,875 --> 00:31:33,677
chamber, is a colossal volcanic

766
00:31:33,778 --> 00:31:39,416
pipe.

767
00:31:39,483 --> 00:31:40,851
Nobody's certain how deep it

768
00:31:40,952 --> 00:31:43,119
goes, but they can picture it

769
00:31:43,221 --> 00:31:45,922
down to 400 miles or more -

770
00:31:45,957 --> 00:31:47,657
twice the distance between

771
00:31:47,692 --> 00:31:54,497
Washington and New York.

772
00:31:54,565 --> 00:31:56,433
Smith makes an educated guess

773
00:31:56,500 --> 00:31:57,701
about what the underground

774
00:31:57,768 --> 00:32:00,136
plume is like.

775
00:32:00,238 --> 00:32:01,938
>> Our best estimates now as we

776
00:32:01,973 --> 00:32:03,240
start doing the physics and the

777
00:32:03,307 --> 00:32:04,875
dynamics of these things, it's

778
00:32:04,942 --> 00:32:06,843
like a conduit of melted rock,

779
00:32:06,878 --> 00:32:09,145
like a chimney.

780
00:32:09,213 --> 00:32:10,614
>> That chimney, called a

781
00:32:10,681 --> 00:32:12,782
hotspot, pumped up enough heat

782
00:32:12,850 --> 00:32:14,751
to melt the rocks of the crust

783
00:32:14,819 --> 00:32:16,319
and fill the overlying magma

784
00:32:16,354 --> 00:32:19,222
chamber, which then erupted to

785
00:32:19,257 --> 00:32:21,258
blast out Yellowstone's vast

786
00:32:21,325 --> 00:32:27,264
crater.

787
00:32:27,331 --> 00:32:28,798
Understanding how the crater

788
00:32:28,866 --> 00:32:30,767
formed was an important moment

789
00:32:30,801 --> 00:32:35,038
for the investigation.

790
00:32:35,139 --> 00:32:36,806
Because there was evidence that

791
00:32:36,874 --> 00:32:38,174
similar eruptions had happened

792
00:32:38,242 --> 00:32:53,189
before. Many times before.

793
00:32:53,257 --> 00:32:55,325
Throughout the 1960s, various

794
00:32:55,359 --> 00:32:56,993
teams of geologists studied the

795
00:32:57,061 --> 00:32:58,428
Snake River Plain, to the

796
00:32:58,462 --> 00:33:00,363
southwest of Yellowstone Park,

797
00:33:00,464 --> 00:33:02,432
and found traces of ancient

798
00:33:02,466 --> 00:33:05,735
volcanic craters.

799
00:33:05,803 --> 00:33:07,470
The crater rims had long been

800
00:33:07,538 --> 00:33:09,272
eroded, but their outlines were

801
00:33:09,373 --> 00:33:11,007
confirmed by aerial pictures

802
00:33:11,075 --> 00:33:16,012
over the following decade.

803
00:33:16,080 --> 00:33:17,614
They ran in a straight line

804
00:33:17,648 --> 00:33:19,749
along the plain, heading for the

805
00:33:19,817 --> 00:33:22,452
heart of Yellowstone Park. On

806
00:33:22,520 --> 00:33:23,920
average, each crater was a

807
00:33:24,021 --> 00:33:25,555
couple of million years older

808
00:33:25,623 --> 00:33:28,024
than its neighbor.

809
00:33:28,092 --> 00:33:29,726
Investigators realized that

810
00:33:29,794 --> 00:33:30,927
these are the remnants of

811
00:33:30,995 --> 00:33:33,930
earlier supervolcano explosions,

812
00:33:33,998 --> 00:33:36,099
an unbroken chain stretching far

813
00:33:36,167 --> 00:33:44,174
back into geological history.

814
00:33:44,208 --> 00:33:46,209
It seemed clear that, time after

815
00:33:46,277 --> 00:33:47,911
time, the hotspohad blasted

816
00:33:47,979 --> 00:33:49,980
out a supereruption and then

817
00:33:50,047 --> 00:33:53,149
moved on. The hotspot appeared

818
00:33:53,184 --> 00:33:54,551
to have traveled hundreds of

819
00:33:54,618 --> 00:33:58,621
miles.

820
00:33:58,689 --> 00:34:00,190
But that posed yet another

821
00:34:00,257 --> 00:34:03,360
riddle. How could a hotspot

822
00:34:03,427 --> 00:34:04,461
anchored to the core of the

823
00:34:04,528 --> 00:34:15,472
planet be moving?

824
00:34:15,539 --> 00:34:17,374
An important clue had been found

825
00:34:17,475 --> 00:34:19,376
in 1985 by American

826
00:34:19,443 --> 00:34:23,913
volcanologist William Scott.

827
00:34:24,015 --> 00:34:25,281
He realized that plotting the

828
00:34:25,383 --> 00:34:27,450
location of 30,000 earthquakes

829
00:34:27,551 --> 00:34:29,452
around Yellowstone produced an

830
00:34:29,520 --> 00:34:32,922
amazing pattern.

831
00:34:32,990 --> 00:34:34,591
The quakes traced out a giant

832
00:34:34,625 --> 00:34:36,359
V-shape on the surface of the

833
00:34:36,427 --> 00:34:39,796
Earth.

834
00:34:39,897 --> 00:34:41,331
The V-shape wrapped around

835
00:34:41,432 --> 00:34:44,634
the hotspot's location. It

836
00:34:44,702 --> 00:34:46,169
seemed, at first, to confirm

837
00:34:46,270 --> 00:34:47,437
that the hotspot was still

838
00:34:47,538 --> 00:34:49,906
moving, rippling up the land

839
00:34:49,974 --> 00:34:51,541
around it with fault lines and

840
00:34:51,609 --> 00:34:52,609
tens of thousands of

841
00:34:52,643 --> 00:35:00,717
earthquakes.

842
00:35:00,785 --> 00:35:02,452
But the real answer lay with the

843
00:35:02,520 --> 00:35:04,988
theory of plate tectonics. It

844
00:35:05,089 --> 00:35:06,356
showed that it's the American

845
00:35:06,457 --> 00:35:08,625
continent, not the hotspot,

846
00:35:08,692 --> 00:35:12,195
that's moving.

847
00:35:12,263 --> 00:35:13,696
And the chain of craters on

848
00:35:13,731 --> 00:35:15,265
Snake River Plain is there

849
00:35:15,332 --> 00:35:17,634
because for millions of years,

850
00:35:17,701 --> 00:35:19,536
the moving American continent

851
00:35:19,637 --> 00:35:21,905
has continually pushed new land

852
00:35:21,972 --> 00:35:24,908
over the stationary hotspot.

853
00:35:25,009 --> 00:35:25,909
But, as the North

854
00:35:26,010 --> 00:35:27,644
American Plate moved across this

855
00:35:27,711 --> 00:35:30,380
source of heat, it pops through

856
00:35:30,448 --> 00:35:33,083
the lid and creates the hotspot

857
00:35:33,117 --> 00:35:34,918
track. That's the Snake River

858
00:35:35,019 --> 00:35:36,186
Plain. Yellowstone is just the

859
00:35:36,253 --> 00:35:38,888
active component today.

860
00:35:38,923 --> 00:35:40,123
>> The repeated hotspot

861
00:35:40,191 --> 00:35:41,658
explosions on land have made

862
00:35:41,759 --> 00:35:46,196
Yellowstone unique.

863
00:35:46,297 --> 00:35:47,397
Other hotspots have been

864
00:35:47,465 --> 00:35:49,632
identified around the world,

865
00:35:49,667 --> 00:35:51,034
like the one that has created

866
00:35:51,102 --> 00:35:53,203
the island chain of Hawaii, but

867
00:35:53,270 --> 00:35:55,538
Yellowstone is the only place

868
00:35:55,573 --> 00:35:57,373
where a hotspot has erupted in

869
00:35:57,441 --> 00:36:02,545
the middle of a continent.

870
00:36:02,580 --> 00:36:04,314
Each of the earlier explosions

871
00:36:04,381 --> 00:36:05,849
blew the original mountains to

872
00:36:05,916 --> 00:36:09,486
pieces. Then, the land smoothed

873
00:36:09,587 --> 00:36:11,287
over with later flows of more

874
00:36:11,388 --> 00:36:13,089
runny lava that was released

875
00:36:13,124 --> 00:36:14,090
from deep under the Earth's

876
00:36:14,125 --> 00:36:21,998
crust.

877
00:36:22,032 --> 00:36:23,466
Multiple strands of evidence

878
00:36:23,501 --> 00:36:25,301
combine to reveal Yellowstone's

879
00:36:25,402 --> 00:36:27,770
slumbering monster, the gigantic

880
00:36:27,838 --> 00:36:29,772
hotspot plume lying under the

881
00:36:29,840 --> 00:36:33,042
park. Earthquake maps show the

882
00:36:33,110 --> 00:36:36,312
hotspot's location.

883
00:36:36,380 --> 00:36:38,148
Seismic waves reveal the depth

884
00:36:38,215 --> 00:36:41,317
of the plume.

885
00:36:41,385 --> 00:36:43,153
And earlier craters prove

886
00:36:43,220 --> 00:36:44,954
regular supereruptions over

887
00:36:45,022 --> 00:36:48,158
millions of years. All of which

888
00:36:48,225 --> 00:36:49,592
leads to the most frightening

889
00:36:49,660 --> 00:36:52,328
question of all. When will

890
00:36:52,396 --> 00:36:54,597
Yellowstone erupt again?

891
00:37:06,792 --> 00:37:07,992
Measuring the amount and

892
00:37:08,060 --> 00:37:09,794
geographical spread of ashfall

893
00:37:09,862 --> 00:37:10,762
from Yellowstone's

894
00:37:10,863 --> 00:37:12,263
supereruptions produced some

895
00:37:12,331 --> 00:37:14,332
terrifying figures.

896
00:37:16,602 --> 00:37:19,437
640,000 years ago, the eruption

897
00:37:19,538 --> 00:37:21,806
poured out around 240 cubic

898
00:37:21,874 --> 00:37:25,443
miles of material - enough to

899
00:37:25,511 --> 00:37:26,611
bury the whole of New York

900
00:37:26,679 --> 00:37:30,882
State tens of feet deep in ash.

901
00:37:30,983 --> 00:37:32,984
If it happens again, thousands

902
00:37:33,052 --> 00:37:35,620
will die and vast areas of the

903
00:37:35,688 --> 00:37:37,055
United States will be buried in

904
00:37:37,156 --> 00:37:40,358
volcanic debris. But when will

905
00:37:40,426 --> 00:37:47,231
Yellowstone erupt again?

906
00:37:47,333 --> 00:37:48,967
One clue to when that next

907
00:37:49,034 --> 00:37:50,702
eruption will happen comes from

908
00:37:50,769 --> 00:37:52,303
investigating the eruptions of

909
00:37:52,338 --> 00:37:56,140
the past.

910
00:37:56,241 --> 00:37:57,508
The hotspot punches out a

911
00:37:57,576 --> 00:37:59,143
supereruption, on average,

912
00:37:59,244 --> 00:38:03,348
every 600,000 years.

913
00:38:03,415 --> 00:38:07,151
And the last one was 640,000

914
00:38:07,219 --> 00:38:10,154
years ago.

915
00:38:10,222 --> 00:38:11,789
But geologists expect that there

916
00:38:11,890 --> 00:38:13,424
will be warning signs before

917
00:38:13,492 --> 00:38:18,896
Yellowstone explodes again.

918
00:38:18,964 --> 00:38:20,498
Volcanic eruptions are usually

919
00:38:20,532 --> 00:38:21,966
preceded by an increasing

920
00:38:22,067 --> 00:38:25,603
number of earthquakes.

921
00:38:25,704 --> 00:38:27,071
The quakes are a sign that

922
00:38:27,139 --> 00:38:28,606
underground volcanic chambers

923
00:38:28,707 --> 00:38:30,408
are filling with molten rock and

924
00:38:30,442 --> 00:38:32,610
expanding to stretch and deform

925
00:38:32,711 --> 00:38:44,055
the land up above.

926
00:38:44,123 --> 00:38:45,423
Yellowstone Park usually

927
00:38:45,491 --> 00:38:47,325
experiences an average of 12

928
00:38:47,426 --> 00:38:48,960
tiny earthquake tremors every

929
00:38:49,061 --> 00:38:52,163
day. Most are too weak to be

930
00:38:52,231 --> 00:38:54,065
felt by tourists and register

931
00:38:54,133 --> 00:38:55,500
only on the most sensitive

932
00:38:55,601 --> 00:39:00,071
seismometers. But in early 2009,

933
00:39:00,139 --> 00:39:01,606
more than four times as many

934
00:39:01,673 --> 00:39:03,341
quakes started striking every

935
00:39:03,409 --> 00:39:06,210
day. Over one ten-day period,

936
00:39:06,245 --> 00:39:07,745
there were more than 500

937
00:39:07,780 --> 00:39:09,614
quakes, some of them up to

938
00:39:09,681 --> 00:39:12,417
magnitude 3.9, powerful enough

939
00:39:12,451 --> 00:39:13,785
to frighten the visitors and put

940
00:39:13,852 --> 00:39:16,954
the scientists on alert.

941
00:39:17,056 --> 00:39:18,489
There's a second indicator of

942
00:39:18,524 --> 00:39:22,493
increasing volcanic activity.

943
00:39:22,561 --> 00:39:24,862
If more molten rock does inflate

944
00:39:24,930 --> 00:39:27,432
the underground chamber, the

945
00:39:27,499 --> 00:39:33,304
ground above will rise.

946
00:39:33,338 --> 00:39:35,039
And that, too, seems to be

947
00:39:35,107 --> 00:39:40,144
happening right now.

948
00:39:40,245 --> 00:39:41,779
Unusual evidence to prove it

949
00:39:41,880 --> 00:39:44,148
comes from an unlikely source,

950
00:39:44,216 --> 00:39:48,519
the waters of Yellowstone Lake.

951
00:39:48,587 --> 00:39:50,755
Around 100 years ago, small

952
00:39:50,789 --> 00:39:52,590
steamships carried tourists on

953
00:39:52,658 --> 00:39:54,025
sightseeing trips across the

954
00:39:54,059 --> 00:39:55,927
lake. But one of the ships

955
00:39:55,961 --> 00:39:57,762
caught fire and sank forever

956
00:39:57,863 --> 00:40:01,499
below the surface of the lake.

957
00:40:01,567 --> 00:40:02,600
But now, Yellowstone's

958
00:40:02,668 --> 00:40:04,235
astonishing geological forces

959
00:40:04,303 --> 00:40:05,937
have resurrected the ship's

960
00:40:06,038 --> 00:40:09,373
remains from their watery grave.

961
00:40:09,408 --> 00:40:11,476
>> Here we have a boat which

962
00:40:11,510 --> 00:40:13,845
burnt down to water level and

963
00:40:13,879 --> 00:40:16,747
so this tells us something about

964
00:40:16,782 --> 00:40:20,118
the deformation of Yellowstone,

965
00:40:20,219 --> 00:40:21,853
and basically, what's happened

966
00:40:21,954 --> 00:40:23,688
is that the floor of the lake

967
00:40:23,755 --> 00:40:26,557
has risen, bringing the boat out

968
00:40:26,592 --> 00:40:28,860
of water.

969
00:40:28,927 --> 00:40:29,961
>> The reappearance of the wreck

970
00:40:30,028 --> 00:40:31,863
shows that land under and

971
00:40:31,930 --> 00:40:33,598
around the lake is rising

972
00:40:33,665 --> 00:40:35,299
because of the expansion of the

973
00:40:35,367 --> 00:40:39,303
magma chamber.

974
00:40:39,371 --> 00:40:40,938
>> Even more alarmingly, the

975
00:40:41,039 --> 00:40:42,640
rate at which it's rising seems

976
00:40:42,674 --> 00:40:46,110
to be increasing. In geological

977
00:40:46,145 --> 00:40:47,945
terms, a huge area of

978
00:40:48,046 --> 00:40:49,213
Yellowstone Park is

979
00:40:49,281 --> 00:40:50,681
positively soaring up into the

980
00:40:50,749 --> 00:40:52,316
air, faster than it's ever done

981
00:40:52,417 --> 00:41:03,394
before.

982
00:41:03,495 --> 00:41:05,196
The biggest uplift of all has

983
00:41:05,230 --> 00:41:07,031
been recorded just a few miles

984
00:41:07,099 --> 00:41:10,134
from the shore of the lake.

985
00:41:10,202 --> 00:41:12,203
There's a GPS system here,

986
00:41:12,271 --> 00:41:13,671
a much more sophisticated

987
00:41:13,739 --> 00:41:17,208
version of the one in your car.

988
00:41:17,309 --> 00:41:18,910
It measures not only its surface

989
00:41:18,944 --> 00:41:21,045
position, but also its exact

990
00:41:21,113 --> 00:41:22,680
altitude to within fractions of

991
00:41:22,748 --> 00:41:25,116
an inch.

992
00:41:25,184 --> 00:41:26,817
>> There's a small radio

993
00:41:26,852 --> 00:41:27,952
antenna, about the size of your

994
00:41:28,020 --> 00:41:29,654
thumb, that sits on top of this

995
00:41:29,755 --> 00:41:32,390
steel rod, and it is anchored in

996
00:41:32,491 --> 00:41:33,758
two to thr--about three or four

997
00:41:33,825 --> 00:41:35,927
feet, so if the ground moves up

998
00:41:35,994 --> 00:41:37,128
and down, the antenna moves up

999
00:41:37,229 --> 00:41:39,864
and down.

1000
00:41:39,932 --> 00:41:41,832
>> The GPS and the land on which

1001
00:41:41,867 --> 00:41:43,034
it's anchored are moving

1002
00:41:43,101 --> 00:41:45,203
upwards.

1003
00:41:45,270 --> 00:41:48,406
>> We're above the magma chamber

1004
00:41:48,473 --> 00:41:51,108
and, beginning in late 2006,

1005
00:41:51,176 --> 00:41:53,444
this whole area of ground

1006
00:41:53,478 --> 00:41:56,214
started to rise, uh, at the

1007
00:41:56,315 --> 00:41:57,915
order of two to three inches per

1008
00:41:57,950 --> 00:42:01,819
year. And as of today, this

1009
00:42:01,853 --> 00:42:03,521
whole system right here has

1010
00:42:03,555 --> 00:42:06,090
risen about that much, and it's

1011
00:42:06,191 --> 00:42:08,459
still moving today, and so we're

1012
00:42:08,527 --> 00:42:09,727
measuring and keeping close

1013
00:42:09,795 --> 00:42:11,462
track of the deformation,

1014
00:42:11,530 --> 00:42:12,797
the--of the uplift that we're

1015
00:42:12,864 --> 00:42:15,700
seeing at this station.

1016
00:42:15,734 --> 00:42:17,368
>> But does the uplift mean that

1017
00:42:17,436 --> 00:42:19,270
Yellowstone's supervolcano is

1018
00:42:19,371 --> 00:42:22,607
threatening to erupt once again?

1019
00:42:22,641 --> 00:42:24,976
>> The question of what lies in

1020
00:42:25,010 --> 00:42:27,178
Yellowstone's geologic future

1021
00:42:27,246 --> 00:42:32,083
is fascinating, and I and all of

1022
00:42:32,184 --> 00:42:33,784
my colleagues would love to

1023
00:42:33,819 --> 00:42:34,819
know the answer to that

1024
00:42:34,886 --> 00:42:36,621
question.

1025
00:42:36,722 --> 00:42:38,155
>> The scientists keep a careful

1026
00:42:38,223 --> 00:42:42,793
watch on the volcano's activity.

1027
00:42:42,894 --> 00:42:44,996
>> The idea of science is to

1028
00:42:45,063 --> 00:42:46,897
understand the process and so

1029
00:42:46,965 --> 00:42:49,433
we have a responsibility to see

1030
00:42:49,501 --> 00:42:50,801
how this system is deforming,

1031
00:42:50,902 --> 00:42:52,169
and how it's working, hence we

1032
00:42:52,271 --> 00:42:53,271
have to be aware there is still

1033
00:42:53,338 --> 00:42:55,072
a possibility of--of volcanic

1034
00:42:55,173 --> 00:42:56,807
eruptions or earthquakes. After

1035
00:42:56,908 --> 00:42:58,042
all, that's what made this

1036
00:42:58,076 --> 00:42:59,810
system, and, uh, there is no

1037
00:42:59,878 --> 00:43:01,412
reason to think that volcanism

1038
00:43:01,446 --> 00:43:04,348
has stopped.

1039
00:43:04,416 --> 00:43:05,783
>> The Yellowstone investigation

1040
00:43:05,817 --> 00:43:07,318
has shown that the park's

1041
00:43:07,352 --> 00:43:09,520
sleeping supervolcano is still

1042
00:43:09,588 --> 00:43:12,857
alive, and dangerous.

1043
00:43:12,891 --> 00:43:14,091
Old Faithful's underground

1044
00:43:14,159 --> 00:43:17,061
plumbing reveals volcanic heat.

1045
00:43:17,129 --> 00:43:18,796
Obsidian glass tells of a

1046
00:43:18,897 --> 00:43:21,766
massive eruption. Seismographs

1047
00:43:21,800 --> 00:43:24,769
record thousands of earthquakes,

1048
00:43:24,803 --> 00:43:26,237
while the earthquake waves

1049
00:43:26,338 --> 00:43:28,005
reveal terrifying underground

1050
00:43:28,073 --> 00:43:30,341
chambers. And the reappearance

1051
00:43:30,442 --> 00:43:32,410
of a sunken boat shows that the

1052
00:43:32,444 --> 00:43:35,780
land is rising.

1053
00:43:35,814 --> 00:43:37,515
And yet, the ultimate

1054
00:43:37,616 --> 00:43:39,350
Yellowstone geological question

1055
00:43:39,418 --> 00:43:42,787
remains to be answered. When

1056
00:43:42,854 --> 00:43:45,256
will the supervolcano erupt once

1057
00:43:45,324 --> 00:43:46,691
again?

1058
00:43:46,792 --> 00:43:47,525
We know there's

1059
00:43:47,592 --> 00:43:48,959
enough magma left, we know

1060
00:43:49,061 --> 00:43:50,394
there's enough heat, we know

1061
00:43:50,429 --> 00:43:51,896
that there will be future

1062
00:43:51,963 --> 00:43:54,532
eruptions in Yellowstone. But we

1063
00:43:54,599 --> 00:43:57,335
don't know if there will ever be

1064
00:43:57,436 --> 00:44:03,140
another catastrophic eruption.

1065
00:44:03,208 --> 00:44:04,942
>> So the investigation is left

1066
00:44:05,010 --> 00:44:08,012
with a deadly serious warning.

1067
00:44:08,046 --> 00:44:09,814
On the timescale that geologists

1068
00:44:09,848 --> 00:44:12,750
work to, a coming supereruption

1069
00:44:12,851 --> 00:44:14,919
in Yellowstone may well be right

1070
00:44:14,953 --> 00:44:17,488
around the corner. That corner

1071
00:44:17,556 --> 00:44:20,291
could be 10,000 or 100,000 years

1072
00:44:20,392 --> 00:44:22,493
in the future. Or it could be

1073
00:44:22,561 --> 00:44:26,664
tomorrow. A new and devastating

1074
00:44:26,732 --> 00:44:27,665
chapter in the ever-changing

1075
00:44:27,733 --> 00:44:30,981
story of how the Earth was made.

1076
00:44:30,985 --> 00:44:34,985
== sync, corrected by elderman ==