Blue Planet Page #2

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...great sheets office

advanced and retreated several times...

...burying Northern Europe

and much of North America.

This is the Hubbard Glacier in Alaska.

Trapped deep inside these frozen walls...

...is a record of climate change...

...going back thousands of years.

By analyzing samples of the ancient ice...

...we may learn to predict

our future climate.

Ten thousand years from now...

...perhaps the sites of Montreal,

Detroit and Copenhagen...

...will again lie buried

beneath a mile office.

And it's moving. Looks good.

To observe large-scale changes

on the Earth...

...we use satellites.

The TDR satellite will act as a relay...

...linking scientists

with dozens of spacecraft...

...watching different parts of the globe.

Kathy, it looked like we had

a good deploy on time.

Everything looks good.

Some study ocean currents...

...others monitor the health of crops.

They also warn us when storms develop.

Of all the storms...

...the most dangerous

and unpredictable are hurricanes.

Without help from satellites...

...we could not prepare ourselves

for the onslaught.

We are under a hurricane warning.

Officials of Civil Defense

are advising voluntary evacuation...

...of the Berry Islands.

Hurricane Hugo,

after ravaging Puerto Rico...

...tore into South Carolina.

What was once a national forest...

...is now a heap of kindling.

Where once there was a house...

...only the front steps remain.

Overnight...

...nature's fury

has devastated entire communities.

But, then, as quickly as it struck...

...the storm vanishes...

...and the eastern seaboard

is calm once more.

There are, however, other catastrophic

events affecting our planet.

They are far more violent than any storm.

The Earth is continually pelted

by a hail of objects from space.

Most are tiny

and burn up in the atmosphere.

But, every now and then,

a big one gets through.

Some 30,000 years ago,

a piece of an asteroid...

...weighing perhaps 300,000 tons...

...slammed into Arizona.

It blasted out a crater

almost 600 feet deep.

As collisions go, it was a small one.

From space, we can see the scars

from much bigger impacts on Earth.

This one in Canada is 60 miles across.

The effects of a similar collision

may have wiped out the dinosaurs.

The young Earth was once

completely covered by impact craters.

But most have been erased...

...by the powerful forces

which keep changing the face of our planet.

From orbit, we see evidence

for the most astonishing...

...geological discovery of our time:

The Earth's crust is broken

into about a dozen moving plates.

Here, a giant crack extends out

to the right...

...from the Sinai Peninsula

through the Dead Sea.

In a closer view...

...you can see how the Sinai,

shaped like a triangle...

...has wrenched away from Saudi Arabia,

on the far right.

The rift that opened between them

lies under the Gulf of Aqaba.

Most of the rifts are on the sea floor.

To search for them,

we need vehicles similar to spaceships.

We are on a journey, two miles down...

...to the very bottom of the ocean.

We will enter a world

that has never seen sunlight.

And yet, the ocean floor

is alive with exotic creatures.

They thrive on nutrients in the water...

...which is heated

by the Earth's great furnace beneath.

Here, in mid ocean,

at the boundary between two plates...

...molten rock pushes up from the interior.

These lava chimneys

are actually miniature volcanoes.

Just as one of the Earth's systems

recycles water...

...another recycles rock.

As new crust

is added to the Earth's surface here...

...the other edge of the plate...

...perhaps thousands of miles away...

...sinks back into the Earth's interior.

As it melts...

...volcanoes erupt.

This is Sakura-jima Volcano, in Japan.

You can see its smoke

all the way from space.

Here, two great plates

are slowly crushing together...

...pushing up the Himalayas...

...the highest mountain range on Earth.

From just beneath us,

the snow-capped peaks...

...stretch over a thousand miles

towards the horizon on the left.

Almost all of North America,

here on the right...

...lies upon a single plate.

On the left, the Pacific plate

is sliding northward past it...

...at the stately pace of a halfinch per year.

The Gulf of California, in the center...

...marks the boundary

between the two plates.

Along this boundary...

...the infamous San Andreas Fault

runs northward.

Using satellite pictures...

...a computer can take us on

an imaginary flight along the San Andreas.

The actual height of the terrain

has been exaggerated...

...to accent the network of valleys

formed by the fault's many traces.

As the two plates slide past one another...

...they lock together in some places.

The strain builds.

Near San Francisco,

the strain reaches the breaking point.

Something has to give...

...and when it does,

we are rocked by an earthquake.

Magnified by the computer...

...first a sharp wave,

traveling at 10,000 miles an hour...

...moves out from the epicenter.

Then comes a series of rolling waves.

These inflict most of the damage.

It is impossible to know yet

how many more fatalities there are...

...following this earthquake, which hit at

5:
04 yesterday, in the middle of rush hour.

The earliest efforts to rescue

came last night from all sorts of people:

Cops, firemen, people right here

in the neighborhood who...

...risked their lives to rescue strangers.

Everything started shaking.

I started running.

I didn't know where to run 'cause...

...l was getting too scared...

...and my mom couldn't get me

because the floor was moving too hard.

Some buildings, though still standing,

had to be demolished.

In time, the houses and highways

are rebuilt...

...better designed to withstand

the next earthquake.

People will always be subject

to nature's powerful whims.

In Japan, another fault zone...

...millions live with the same uncertainty.

One day, almost certainly...

...we'll learn to predict earthquakes.

But, in the meantime,

we try to live in harmony...

...with our sometimes turbulent planet.

After each assault, we pick up the pieces,

and carry on.

And sometimes, we wonder

if there could be any other place...

...as wonderful in all the universe.

But, now, a new force...

...as threatening as any in nature...

...has begun to change the Earth.

We are that force.

To our ancestors,

only a few centuries ago...

...the forests, oceans and skies...

...seemed vast and almost limitless.

But all that has changed.

It is only now that we can see it

from space...

...that we realize the magnitude

of what we are doing to the Earth.

As settlers cleared land to create

the great farms of the American Midwest...

...more and more valuable topsoil...

...eroded into the Mississippi.

Flowing southward down this great river...

...the silt is carrying pesticides.

They are pouring into the Gulf of Mexico.

The Yangtze River in China...

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