Inside Planet Earth Page #2

that the Earth is made of--

space junk glued together.

4.6 billion years ago,

the molten Earth grew

as a continual rain

of mega-meteorites

pummeled it

on its orbit around the sun.

Each strike brought with it

raw rock,

the material

from which Earth could grow.

It also brought

explosive energy,

raising the surface temperature

of the primitive planet

to over 1,800 degrees.

A vast ocean of molten rock

100 miles deep

covered the globe.

Internal radioactivity raised

the temperature even further.

Earth became a melting pot.

The meteoric iron

began to sink to the center,

dragged by the relentless tug

of gravity.

A kilometer sphere of molten

iron would make the journey

from the surface

to the center of the Earth

in less than a million years--

a blink of geological time.

The constituents of the Earth

were forming.

It had an iron core

surrounded by molten rock.

On the surface,

a thin crust was developing.

It behaved

like these lava ponds.

And the turbulent forces beneath

began to fracture the crust.

These are the tectonic plates--

vast sheets

of the Earth's crust,

tearing and crashing

over the planet's surface.

They drift endlessly around the

globe like giant bumper cars,

joining and separating,

carrying with them

all the continents and oceans.

There are 9 huge ones,

many thousands of miles wide.

And it's at their boundaries

that catastrophes occur.

When they clash,

new landscapes are created.

Oceans shift.

And mountains soar into the sky.

Montserrat sits on the boundary

of the Caribbean

and North American plates,

where volcanoes erupt

and earthquakes shudder.

The actual fabric

of the land itself is made here.

Where the tectonic plates

that form the ocean floor

are torn apart,

new lava continually emerges,

and new volcanoes are born.

In 1963, this act of creation

could be seen by all.

Some 10 billion square feet

of lava

erupted off the coast of Iceland

to form the new island

of Surtsey.

It emerged in a matter of days,

just like volcanic islands

on the primitive Earth.

All over the planet,

these islands appeared.

And in time, they were to form

the first continents.

Clues as to how this happened

are found in

the Canadian Rocky Mountains.

The outer shell of Earth--

the lithosphere--

carries the continents.

It's made up of great stratas

of different rocks

extending 60 miles down

into the earth.

Most of its structure

is unknown.

The deepest man has ever drilled

is 9 miles.

Exploring deeper

needs a different approach.

To discover just how

their land was formed,

a team of 700 scientists--

the modern equivalents

of early mapmakers--

are charting

this invisible territory.

They use shock-wave detectors--

geophones--

which the teams are placing

all over the landscape.

This is the world's biggest

subsurface exploration

experiment-- the Lithoprobe.

In the Yukon province, the chief

scientist is Charlie Roots.

Geologists who work

in sedimentary rocks

are used to continuity,

both in oldest rocks

to youngest rocks,

as well as being able to take

the same rock formation

for a long distance.

You can't do it

in these mountains.

The rocks on the surface

indicate a large platform

of limestone,

and the surrounding areas

are rocks

that have no relation to that.

They are bits that are

not part of the continent,

that appear to have come

from somewhere else.

These canyons show the folds

and the twists

that the rocks have undergone

as they've been pushed up

against the ancient continent.

The problem is that

you only get to see the rocks

that are at the surface.

And in an area where rocks

are steeply dipping,

there is far more of the story

buried beneath our feet.

To send shock waves

deep into the crust,

200 pounds of explosive

are buried in the ground.

We're digging 3 holes

for the geophones that we're

going to be putting in here

so that we can have

a 3-component

orientation system

to measure the seismic wave

that comes in.

We have a vertical geophone

which will measure the vertical

component of the arriving wave.

There is a north-south geophone

that will measure

the north-south component

of the incoming wave.

And we have

an east-west geophone

to measure

the east-west component

of the incoming seismic wave.

10, 9,

8, 7,

6, 5,

4, 3,

2, 1.

As the shock wave races down

through the ground,

they hit something hard--

much harder

than the surrounding rock.

The shock waves are reflected

and speed back to the surface,

taking their precious

information to the geophones.

Analysis of the result

shows that under the Rockies

are the buried remains

of ancient volcanic islands.

Over the last 200 million years,

hundreds of these islands

were grafted

onto the North American

continent.

They form much of the land

west of the Rockies,

stretching from Mexico

to Alaska.

This is a clue as to how the

first landmasses were created.

But until very recently,

science was at a loss

to say just when it happened.

Then, one day,

prospecting for minerals

in northwestern Australia,

Roger Buick made

a startling discovery.

This rock is part of the oldest

land surface on Earth.

It has miraculously survived

the never-ending cycle

of formation and destruction

of the crust.

The vertical stripes

have endured

for over 3.6 billion years.

At the same time,

the Earth began to cool.

condensing in pockets,

but not enough

to create oceans or rivers.

There was no oxygen in the air.

It was inhospitable,

with no trace of life.

A new theory suggests that,

in time, water--

maybe enough

to fill the world's oceans--

arrived from deep space,

brought on ice comets.

Cosmic rain continues today with

small, 20-to-40-ton ice comets

striking the Earth's atmosphere

once ever 3 seconds.

They add one inch of water

over the entire surface of

the globe every 20,000 years.

When the atmosphere was

saturated, the rain began.

An endless ocean grew.

And when the skies

finally cleared,

the Earth had been transformed

into a watery globe.

This is the time when life

is thought to have begun.

Echoes of those beginnings

can still be heard today.

Our most ancient ancestors,

the most resilient creatures

ever evolved,

have survived unchanged

for billions of years

living in solid rock.

Drilling to great depths

into the rocks at Idaho Falls,

Princeton microbiologist

Tullis Onstott

is hoping to take a closer look

at their descendants.

Hey, thanks.

What I find truly remarkable

is that within this core barrel

is a massive piece of rock

from 200 feet below the surface,

and yet it contains

as many bacteria in it

as there are

people on this planet.

Now, these are living bacteria.

And they live at temperatures

approaching the boiling point

of water.

They live at pressures that are

100 times of atmosphere.

They live in a salty, briny

solution that's alkaline.

It contains gases

that are toxic to us.

And yet they still manage

Rate this script:0.0 / 0 votes