How the Earth Was Made

As continents shift and clash,

volcanoes erupt, glaciers grow

and recede, the Earth's crust

is carved in countless,

fascinating ways, leaving a

trail of geological mysteries

behind.

And one of the greatest is right

here, at Yellowstone National

Park in Wyoming.

This is one of the world's most

geologically active places,

shaken by up to 5,000

earthquakes every year, and

with more geysers and hot

springs than in the rest of the

world combined. Why is

Yellowstone so active? How did

it form? And why here in the

heart of the Rockies?

Scientists studying Yellowstone

are uncovering a violent past.

Carved by water, crushed by

ancient glaciers and blasted by

the biggest volcanic eruptions

ever known on the planet.

And even today, Yellowstone is

one of the most dangerous

places on Earth.

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

== sync, corrected by elderman ==

Yellowstone National Park is one

of the most amazing places on

Earth, and it's unique.

It contains some of America's

most stunning scenery and

wildlife that attracts three

million tourists a year.

To understand where Yellowstone

came from, and why it is so

active today, we need to take a

journey back into the distant

past of the North American

continent and deep into the

Earth's interior.

Yellowstone sits 8,000 feet up

on a remote mountain plateau,

primarily within Wyoming, but

stretching into parts of Idaho

and Montana.

The park covers 3,468 square

miles, 63 miles north to south

and 54 miles east to west.

And it's on top of one of the

world's most unusual and

deadliest geological structures.

>> What's unusual about the

park? Are the wildlife unusual?

No. Is the wide open space

unusual? No. You've got it all

over the western US. What's

unusual? It's a very unusual

geology that created the park.

Yellowstone was founded as the

world's first National Park

because of the geology.

>> It's this strange geology

that attracts teams of

scientists to the park.

Their task, to piece together

the story of the incredible

processes that built this

unique, extraordinary landscape

by digging deep into

Yellowstone's past.

>> The geologic history of

Yellowstone goes back to the

formation of the North American

continent. Some of the rocks in

Yellowstone are 2.8 to 3.2

billion year old rocks, some of

the oldest in North America.

>> Only by traveling back into

the past can we figure out why

in this particular location

there are 2,400 miles of

rivers, more than 300 waterfalls

and the world's greatest

concentration of 10,000 hot

water springs, bubbling

mud-holes, gas vents and

geysers. What do these features

reveal about this landscape, and

how it was formed?

The investigation begins at

Yellowstone's star attraction,

Old Faithful.

It's a key clue to what's going

on underneath the surface.

Located in the southwest of

Yellowstone Park, the geyser

puts on an explosive display

every 90 minutes or so, blasting

out thousands of gallons of

scalding hot water.

>> Yellowstone is like no other

place on Earth, there is so

much heat coming out here.

It's really a singular

phenomenon.

Well, after about a 90-minute

nap, Old Faithful has roared

back to life. It wasn't actually

napping, it was recharging, and

the temperature of the water was

increasing, the system was

pressurizing. Beneath Old

Faithful is a rather complex

plumbing system, filled with

caverns and conduits and

constrictions.

>> Rainwater saturating the

ground around the geyser slowly

fills its underground reservoir.

Hot rocks below ground heat the

water under pressure for around

90 minutes. Suddenly, some water

spurts through a tiny, five inch

wide crack in the rocks.

This causes a drop in the

pressure within the water

chamber. In an instant,

thousands of gallons of water

are turned to steam and blasted

up into the air.

>> When the pressure builds up

enough, steam bubbles start

rising to the surface, the

system depressurizes, and a

full eruption can occur.

>> Old Faithful shows that rocks

below the surface are very hot.

Scientists find clues to a

violent past 34 miles southeast

of the hot springs, on the

shores of a circular lake

called Indian Ponds.

>> As a field geologist, my job

is to basically be a rock

detective. And so I try to

determine what their origin is

and what the history is of that

particular rock. There we go.

OK, now, in this particular

case-- Let's look at this. This

rock, when it started, it was

just a loose sand, you could

just put your fingers through

it.

>> The solid boulder is formed

from millions of individual

grains of sand.

Microscopic analysis reveals the

grains have been cemented

together by chemicals and

pressure deep under the ground.

But how did the rock get to the

surface?

Morgan has chemically dated the

rocks and discovered that 3,000

years ago, the boulder was

blasted out of the ground by

the hot water explosion of a

gigantic geyser.

>> You would see boiling water,

rock fragments and fine muddy

material being ejected up into

the air as high as 3 to 5,000

feet. And then, at some point,

material would start raining

down from this explosion column.

Now, you wouldn't want to be

standing next to one of those.

>> Indian Ponds is the crater

that the geyser left behind.

But it is dwarfed by the crater

Morgan has found at Mary Bay in

Yellowstone Lake.

Morgan has dated this geyser

explosion to 13,000 years ago.

>> So here we are in the middle

of Yellowstone Lake, and it's,

as you can see, a beautiful day

and it's nice and placid, but on

the floor of Yellowstone Lake,

it's anything but quiet.

>> Morgan's research proves that

geysers were exploding around

the lake, and even under the

water, between 13,000 and 3,000