Inside Planet Earth Page #3

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

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