All language subtitles for The Living Planet - 1x01 - The Building of the Earth

THE LIVING PLANET

A PORTRAIT OF THE EARTH

Our planet, the earth, is, as far
as we know, unique in the universe.

It contains life. Even in its most
barren stretches, there are animals.

Around the equator, where
those two essentials for life,

sunshine and moisture, are most
abundant, great forests grow,

and here plants and animals
proliferate in such numbers

that we still have not even
named all the different species.

Here, animals and plants,
insects and birds, mammals and man

live together in intimate
and complex communities,

each dependent on one another.

Two thirds of the surface of this
unique planet are covered by water,

and it was here indeed
that life began.

From the oceans, it has spread even to
the summits of the highest mountains,

as animals and plants have responded
to the changing face of the earth.

THE BUILDING OF THE EARTH

This river, the Kali Gandaki, has cut
its way, in the most remarkable fashion,

right through the highest range of
mountains in the world, the Himalaya.

To the east of me rises Annapurna,
over 26,000 feet high.

To the west, Dhaulagiri,
even higher.

Their two summits are
a mere 22 miles apart,

and I am four vertical
miles below them.

And that makes this the
deepest valley in the world.

At this altitude,
about 7,000 feet, it's quite warm,

and animal and plant life on the flanks
of the valley is both rich and abundant.

The blossoms on these trees
may well look familiar.

Flowers like them grow in
gardens all over the world.

But these are wild plants and this is
their original home. They're rhododendrons.

And here they are food for monkeys,
grey langurs,

reminders that the hot plains of
Southern Nepal and the tropics

are not far away to the south.

But they aren't just monkey food. They
are the rhododendrons' advertisements,

attracting birds and insects which will
sip their nectar, gather their pollen,

and so bring about
their fertilisation.

The ring-necked parakeet
also comes from the tropics.

Here, it's at the top of its range. Any higher
and the weather will be too cold for it.

Beneath the rhododendrons
live several species

of those most splendid of
Asia's birds, the pheasants.

The blood pheasant, for all its delicate
beauty, is a plainer member of the family.

The cock Tragopan is surely
the most magnificent.

Until, that is,
you see a cock Impeyan pheasant,

with the coronet of a
peacock and the burnished,

metallic iridescence of
a tropical butterfly.

The Impeyan's hen, like those of all
pheasants, is comparatively dull.

This deepest of all valleys in the world
enables you to walk within a few days

from the tropics,
in its lower reaches,

to the equivalent of the poles
on the slopes high above,

and to see as you make the journey

how closely animals and plants are
matched to the changing circumstances.

As you walk higher, the rhododendron forest
gets thinner and becomes hung with moss.

The air is still moist and it
can be quite warm during the day.

And now, in summer,
there are orchids here.

On the ground beneath, flowers
appear in close-packed bunches,

protecting one another
from the night frosts.

The little Himalayan panda is certainly
very well protected against the cold.

Not only does it have warm,
dense fur, but, like many animals

that spend some of their time in the snow,
it has hair on the soles of its feet.

That not only keeps its feet warm on the
snow but stops it from sliding around on ice.

Now, in the summer, it also helps in
getting a grip on wet, slippery branches.

It's primarily a vegetarian,
collecting buds and leaves and fruit,

but it also takes eggs from a
bird's nest, if it can find one.

On the ground,
and scarcely bigger than the panda,

one of the shyest animals of the
Himalayan forests, a musk deer.

In these tangled trees, antlers
would be a considerable handicap,

and the musk deer
doesn't develop them.

A male fights instead with the
short sharp tusks in his upper jaw.

They feed on moss,
lichen and leaves,

and are so agile and
well-adapted to a mountain life

that they can climb steep
cliffs in search of food.

When a musk deer or any other animal
of any size dies, the vultures come.

These are griffons, very similar
to those that circle the skies

above Indian villages
down in the hot foothills.

They are common in this forest
up to 7,000 or 8,000 feet.

So the lives of all these
creatures are connected,

one with the other,
either directly or indirectly,

and all are ultimately
dependent upon the vegetation.

But of course,
both animals and plants

are also greatly affected
by the physical environment.

I've climbed several thousand feet now
and things are beginning to change.

It's getting colder, and the
rhododendrons are giving way to fir trees,

and that will mean a change
in the animals that live here.

The yellow-throated martin has
a fairly broad taste in food.

It takes fruit on occasion, catches
the few insects now and then,

but it relishes above all small
rodents, like mice and squirrels,

and there are quite a
lot their found here.

Even when winter comes, when the forests
are deep in snow, it will remain active.

But it's a great traveller, and if
the weather becomes very cold indeed,

it will descend to lower
altitudes for a spell.

The Himalayan bear is capable
of living very high indeed.

Its thick fur protects it
against really severe cold,

but its range is not limited by
temperature so much as by food supply.

In spite of its huge size, it seldom
tackles any animal bigger than a mouse,

and it lives for most of the time on
just ants, grubs, nuts and leaves,

so it seldom goes any higher
than the forest can grow.

And now, getting on for 10,000 feet
up, the forest is beginning to thin.

In summer, there's not much rain here,
for it most has fallen at lower altitudes.

In winter, it gets extremely cold.

Those conditions don't suit rhododendrons.
Here only conifers flourish in large numbers.

High though we are, the Kali
Gandaki is still a very broad river.

Remarkably,
and indeed mysteriously,

it doesn't rise from the flanks of these
giant mountains but cuts right through them.

The people of the foothills
have long since recognised

the value of this extraordinary corridor
that leads right through the Himalayas,

and all summer trains of
mules trudge up the valley,

taking barley and buckwheat to trade
with Tibetans for wool and salt.

All the way up the valley there are villages
where the muleteers can stay and rest,

but during the summer few do so.

Most trudge tirelessly upwards
for as long as there's daylight.

A lammergeier, the bearded vulture,
a mountain bird

that soars around the high valleys of Asia
and still in a few remote parts of Europe,

but nowhere higher than this.

And a sign that now we are
getting really high: Snow cock.

Its dappled white plumage gives it
good camouflage against the broken snow

that even now, in summer,
can fall at these altitudes.

They forage for seeds and
rootlets in the thin turf.

There are no trees now, just a few
small shrubs and dry, withered grass.

But that's enough for the tahr.

It is neither a true sheep nor a true
goat, but related equally to them both.

It will eat almost anything that's green, and
is grateful to find it in this bleak land.

Another typically mountain creature:
The red-billed chough, a kind of crow.

They search the rocks for insects, grubs,
odd seeds. They will take most things.

Their cousins, yellow-billed choughs,
go as high as any bird in the world,

riding the rising wind currents to the
height of the snow peaks themselves.

Flowers at this altitude can only
come from small cushion plants,

huddled together against the cold.

Higher still,
little can grow except lichens.

Now it's so cold that growth may only
be possible for a few days in the year.

And yet, in these bleak regions,
people live.

To help plough the fields,
they use the yak,

a domesticated creature that once
roamed wild on the plains of Tibet,

the only large mammal that lives
permanently as high as man.

The people, Bhotias and Sherpas,
grow not only barley but potatoes,

a crop that was first cultivated
by the Incas in the Andes

and was introduced here
a century or so ago.

These highland people are well-adapted
to life at these altitudes.

Their blood contains a particularly
high number of red corpuscles

and so can carry more oxygen
in it than a lowlander's can.

Certainly, when it comes to
walking at these high altitudes,

they're very much better
adapted than I am.

So, all the living creatures
in these high valleys

are adapted to their environment,
both their biological environment

and their physical environment. And
yet, in terms of biological history,

those adaptations are
very recent indeed.

These immense mountains,
the eternal hills,

are in fact far from eternal.

They are younger than the
plains of India to the south

or the plateau of
Tibet to the north.

They were raised to their present
height about 65 million years ago

from the bottom of the sea.

And what is the evidence for
that extraordinary statement?

It can be found all over the place,
just up here.

These slopes are littered

with fragments like these.

This is obviously a shell that's
been turned to stone, a fossil.

Although there are no molluscs
alive today exactly like this one,

there are some which are sufficiently similar
for us to be sure that it lived in water.

And if we analyse the rock
in which it's embedded,

it's clear that that was mud
laid down at the bottom of a sea.

But I am about as far as possible
is it's to be from the sea.

Not only am I in the middle of Asia,
hundreds of miles from the sea,

but I am over two vertical
miles above it's level.

What forces could possibly have
raised the seabed to these heights?

We now know that those
forces are still in action,

that these mountains are still rising
and that land is still being created.

I'm in Iceland.
This fantastic fountain of fire

rising 200 feet or so into the
air behind me is molten rock.

Fine ash is falling all around, there
are gusts of choking, poisonous gas,

and it's so hot that this is just
about as close as I can get to it.

The sheer weight of these
molten ingots of rock

prevents them being swept away
from the vent by the gale,

so there's little danger of
them suddenly coming our way.

Less dramatic than the fire
fountain but perhaps more sinister

is this tide of black slag that is slowly
creeping over the surface of the land.

In parts it's red-hot and
molten and flows like treacle,

but on the edges it's cooled enough
for me to be able to handle it.

It's black,
it's heavy and it's called basalt.

Basalt like this has been welling
up from deep in the earth's crust

ever since the beginning of
the history of our planet.

A flow may travel for
as much as 25 miles.

Sometimes it moves no
faster than a man can walk,

but sometimes it races along
at an extraordinary speed,

40 miles an hour, and nothing...
nothing... can stop it.

Sometimes so much lava is produced

that it accumulates in
flows 100 feet or so thick.

Then the centre layers of it cool
exceptionally slowly and very evenly,

and this is the result.

Here, at the Giant's Causeway island, the
top of the lava flow has been eroded away,

for the eruptions took
place 50 million years ago.

The cooling contractions have produced the
effect you can sometime see in drying mud,

though here the cracks extend
to a much greater depth

to produce six-sided columns
about a foot and a half across.

Over the sea, in the Hebrides,
there's another lava flow

that erupted at about the same
time and formed Fingal's Cave.

The blanceting layer of lava that slowed down
the cooling of the interior is still uneroded,

and beneath it the near-perfect basalt
columns rise almost 20 feet high.

Basalt that doesn't contain very much
gas wells out from below almost quietly.

But if the lava has been
extruded under great pressure,

it may be full of gas, and then
it behaves very differently.

Sometimes a flow sweeps down over a
forest, incinerating the trees in its path.

Most dramatic of all, the lava sometimes wells
up inside the deep crater and can't escape.

Then it forms that most fearsome of
nature's spectacles, a lava lake,

like this one in
Nyiragongo in Africa.

This lava is over 1,000 degrees
centigrade, 2,000 degrees Fahrenheit.

The bubbles of gas that burst from
its surface may be 50 feet across.

Sometimes, having got rid of much of
its gas, like beer losing its fizz,

it sinks back down the
vast pipe up which it roses

and returns to the lava
chamber a mile or so below.

But lava lakes fed by
pipes are not common.

Basalt more usually comes to the surface
of the Earth in a rather different way.

These Icelandic volcanoes erupt
from huge cracks or fissures

which regularly open up in a line which
runs right across the width of the island.

But that line itself is only the
northern end of a huge line of weakness

that runs for thousands of
miles southwards from Iceland

right round the side of the globe.

Iceland lies between Norway and
Greenland, south of the Arctic Circle.

The crack, ridged over by lava,
is mostly underwater,

which is why its existence wasn't known
until the beginning of this century.

From Iceland it runs midway between
Europe and Africa to the east

and the Americas to the west. In
places, it rises above the sea

to form volcanic islands:
The Azores, the Cape Verdes,

Ascension, St Helena,
Tristan da Cunha.

But below the surface the lava
is also continually erupting,

unseen by human eyes until
only a few years ago.

The clouds of gas come
from the lava itself.

They're not steam. The pressure of the
water prevents that from being produced.

The heat is rapidly absorbed by
the vastness of the ocean itself

so that the lava cools and congeals much
more quickly than it would do in the air.

Eruptions like these, at great
depths, built the Atlantic ridge.

But the basalt forms not only the ridge
itself but the sea floor on either side.

By dating it chemically,
we know that the farther way it is

from the centre of the ridge,
the older it is.

This means that basalt is welling
up in a molten state at the ridge

and then, as it solidifies,
is moving away on either side.

We still don't fully understand
the forces that power the process,

but it seems that 50 to 60
miles below the earth's surface

it's so hot that
the rocks are molten

and currents in them are welling up
beneath the ridge, causing eruptions,

and then flowing
away on either side,

pulling the great plates of
the ocean floor with them.

It was this movement that dragged
apart Africa and South America

and created the Atlantic Ocean.

Similar things have
happened in the Pacific.

The great plate that forms the
eastern part of the ocean floor

is moving towards the
west coast of America.

But where it meets the continent,
it dives downwards,

perhaps pulled by the descending
current in the crust below,

producing a deep trench
in the ocean floor.

As it goes down, it takes
with it some of the sediments

that accumulated of the bottom
of the ocean and also some water.

These new ingredients melt with
the basalt as they get deeper

and interact with the rocks of
the interior to produce a mixture

that is crucially different from the
lava that erupted at the ocean ridge.

For one thing, it contains much
more dissolved gas and steam.

As it rises up in the cracks
on the edge of the continent,

it cools and solidifies,
choking the vents.

The effect is like screwing down
the safety valve of a boiler.

Mount St Helens on the Pacific
coast of North America.

On May 18th 1980,

with an explosion 500 times as powerful
as the atomic blast at Hiroshima,

it blew away three-quarters
of a cubic mile of rock.

The forests around the mountain
were totally destroyed.

Trees 200 feet tall lay
scattered like matchsticks.

Geologists, weeks beforehand,

watching a huge bulge develop
on the side of the mountain,

had warned of the
coming catastrophe.

Even so, over 60 people
stayed and were killed.

On the northern side of the volcano,
there were not even trees to be seen.

A huge avalanche of rock,
blown out by the blast,

had slid for 15 miles down the side
of the mountain, burying everything.

Behind it,
Mount St Helens lay wrecked.

Its summit was over
1,000 feet lower,

and at the back of a huge amphitheatre,
a mile wide from which the rock had come,

another ominous bulge was
developing, swathed in jets of steam.

Almost a century earlier, on the
opposite side of the Pacific,

another catastrophic eruption had taken
place on the tiny island of Krakatau,

in the straits between Java to
the east and Sumatra to the west.

In 1883 it was an island five
miles long and three miles wide,

with three volcanic peaks on it, the
highest of which rose to almost 3,000 feet.

But those peaks were dormant. There had been
no sign of any volcanic activity on Krakatau

within living memory.
But then, in August of that year,

people on the coast of Java began
to hear series of explosions.

A great column of smoke
rose above Krakatau.

Pieces of lava the size of a house
were being thrown high into the air.

The explosions
continued day after day.

The column of smoke rose up until it
was five miles or so up into the sky.

Ships that were sailing nearby had
their decks covered in ash and pumice,

and at night electric flames
played over the rigging.

Day after day this continued.
And as it was doing so,

it was emptying the lava chamber
deep in the crust beneath the sea,

and that was the cause of the
greatest catastrophe of all.

Because on the morning of August
27th, Monday, at 10 o'clock,

the roof of that lava
chamber collapsed.

Millions of tons of sea water
poured onto the red-hot lava.

So did millions of tons of rocks.

And this produced a
titanic explosion.

The noise was almost
certainly the loudest noise

that has ever echoed round
the earth in recorded history.

It was heard 2,000
miles away in Australia.

3,000 miles away on the small island
of Rodriguez in the South Atlantic,

the commander of the garrison heard it
and thought it was distant gunfire at sea.

The explosion also
produced a tempest of wind,

which swept out entirely round
the globe seven and a half times

before it finally died away.

But most catastrophic of all, the
explosion produced a tidal wave.

It swept towards the
coasts and as it approached

it became a wall of
water over 100 feet high.

It crashed into the
harbours of little villages,

it picked up a naval
gunboat with a crew of 28

and lifted it bodily for over a mile
inland and dumped it on the top of a hill.

And it overwhelmed
village after village.

Over 36,000 people were killed.

The pall of ash brought darkness

over an area of 100 miles
or so for several days.

But when it cleared away, they found that
the island of Krakatau was unrecognisable.

Three-quarters of the main
island had disappeared.

The two nearby islets were buried
beneath massive deposits of ash.

And where the tallest peak had
stood, the sea was 900 feet deep.

But not for long. 44 years later another
island rose from the boiling sea.

They called it Anak Krakatau:
The child of Krakatau.

Compared with the
explosions of its parent,

its eruptions are still
trivial bubblings.

Now, after more than 50
years of fitful activity,

Krakatau's child has
built itself a new cone.

It's still not very big,
less than 1,000 feet high.

Sporadically, it explodes. But often
it's easy enough to walk round its rim.

The fumes that boil up from its crater are
partly steam and partly sulphurous gas,

and the sulphur condenses on
the rocks, coating them yellow.

All volcanic eruptions spew out
sulphur in one form or another,

including those underwater.

Here it doesn't form
yellow crystals,

but reacts with the sea water to
produce clouds of black sulphides.

These smokers, nearly two miles
deep on the floor of the Pacific,

are one of the most extraordinary
scientific discoveries of recent years.

The sulphides they produce are
food for microscopic bacteria.

They, in turn, are consumed by a
group of creatures, quite unlike any

that have been seen before.

These are giant
tube-worms 11 feet long.

They have neither mouth nor gut but
absorb bacteria through their thin skin.

And these are clams, two feet across.
They too consume the bacteria.

The heated water rising
above the smokers

causes currents along the sea bottom that
sweep small particles towards to the vents

so there's a whole community
of creatures feeding on them.

Small, white, blind crabs.
Strange fish, hitherto unknown.

Until this bizarre
colony was discovered,

we had believed that
all creatures on earth

derived their energy
through plants from the sun.

Even the deep sea creatures we knew of fed
on fragments falling from the sunlit surface.

But here were animals that
owed nothing to the sun

and were sustained through bacteria
by the chemical energy of volcanoes.

But volcanoes don't
remain active for ever.

Eventually, there is some
shift deep in the earth's crust

and the focus of the intense
heat moves away slightly

and the eruptions come to an end.

But if water should percolate down
from the surface through the rocks

and approach to the magma chamber,
it's still so hot

that the water is superheated
and forced up again,

like water in the spout
of a boiling kettle.

On the way, it may well dissolve minerals
from the rocks through which it passes,

and then, as it emerges as hot springs,
the minerals will be deposited in terraces,

like these in Rotorua,
in New Zealand.

In some parts, the superheated
steam on its way to the surface

has dissolved the softer rocks
through which it is passes

and brings them up as boiling mud.

Elsewhere, the boiling water shoots
spasmodically into huge fountains,

and the whole area
is wreathed in steam.

Such a place is typical parts of land
where volcanic fires are on the wane.

The famous hot springs of Yellowstone
in the Rocky Mountains of North America

are also heated by a vast
chamber of molten rock

some distance down
beneath the surface.

The water welling up from these
crystal-clear, chemically rich pools

is so scaldingly hot that no
creature can live in them.

But when they trickle over
the brim, they begin to cool,

and there rich colonies of bacteria
and mats of algae begin to grow.

In places they flourish so thickly
that they break the surface

and divert the flow of water so that in parts
they're cool enough to allow brine flies.

The flies come to
feed on the algae.

And here, too, they mate.

They lay their eggs directly
in the warm mat of the algae.

Each has a long white thread
to its case, like a seed.

The eggs, however,
are far from safe.

They're seized by mites that
clamber about over the algae.

Spiders, too,
prowl around the grazing herds.

A slightly larger fly moves
among the brine flies.

It too is a killer,
devouring the grubs.

So the algal mats support a
closely-knit interdependent community,

all nourished by chemicals in the water
and energised by the volcanic heat.

But in the end it's
destroyed by its own success.

Increasing numbers of grubs munch away
the algae and begin weaken the mat.

Eventually it gives way, the channel clears
and lethal scalding water gushes down,

killing an entire generation of grubs and
many hunters and parasites that live on them.

Now the process has to
start all over again.

The hot volcanic springs of
the Rift Valley in Africa

also support their own crops of bacteria and
the small floating algae that feed on them.

But here the creatures that come
to harvest them are much bigger.

Flamingoes, sometimes as many as a
million of them on this one lake.

These lesser flamingoes feed
entirely on single-celled algae

that proliferate in vast quantities
in these steaming soda-rich waters.

Flocks like these remove 150 tons

of these microscopic plants
from this lake every day.

Their bills have sieves inside
them which strain off the algae

as the water passes through them.

It's easy to see how living
creatures can benefit

from the chemical riches of volcanoes when
thay dissolved in the waters of hot springs.

It's more difficult to
imagine how any living thing

could derive nourishment
from a basalt lava flow.

Its surface in many places is
as smooth and as hard as glass,

and neither frost nor roots of plants
can initially make any impression on it.

Centuries may pass
after an eruption

before there's any sign of the surface
of such a flow beginning even to weather.

This flow for example on the flanks of Mount
Kilauea in Hawaii is some 3,000 years old,

and yet still it shows the rippled, ropy
surface that formed when it was liquid.

But in the end the surface does erode and
plants do manage to get root in the cracks.

They in turn can support
all kinds of other life,

and so the lava flow is
eventually colonised,

not only on its surface
but in its depths.

For these basaltic lava flows are
often not as solid as they seem.

When the lava first flows
out of the vent like a river,

that on the outside of the flow
will cool quicker and solidify,

forming walls on either
side of the flow.

The top too cools quicker, and that
causes a crust to form over the flow,

so that eventually the lava
is flowing down a long tunnel.

When that happens, the walls and
ceiling of the tunnel act as insulation,

keeping the heat in, so that
the lava flow remains liquid

and so continues
for mile after mile.

When eventually the
supply of lava stops,

that tunnel may drain, leaving
a long cavern like this one.

Out of the reach of rain
and frost and even dust,

the surface of the lava looks
exactly as it must have done

when the last trickle was draining
away and the floor was so hot

that anything touching it
would be turned to a cinder.

Molten lava had dripped from the
ceiling, it had swilled round the sides

and spurted out in little dribbles from
cracks in the newly congealed walls.

But living organisms
have already moved in.

These roots belong to trees that are
growing on the surface of the lava flow.

They've found their way down through
the cracks, and here they dangle,

catching water as it percolates through
the lava and trickles down them.

Among the rootlets, there are animals
that live nowhere else in the world.

Normally, these creatures
are in total darkness.

Nearly all of them, like this
cricket, have lost their pigment.

Many of them have also lost
their wings and their eyes.

In the blackness,
they find their way about by touch,

and, like many cave insects
elsewhere in the world,

have consequently developed
long legs and antennae.

Some, like this bug,
are scavengers.

Others, like the centipede, hunt.

And the millipedes
feed on the roots.

So, in these extraordinary
lava caverns,

there is yet another community
of interdependent creatures

that have come into existence
since the volcanoes erupted.

The colonisation of volcanic
ash presents different problems.

The difficulty here is not the
glassy hardness of the rock

but quite the reverse,
its insubstantial dustiness.

Mount St Helens is
still a wasteland.

It's now, as I speak,
some two and a quarter years

since the volcano erupted.

I'm some three miles
from the crater,

and still the scene is one
of devastation and sterility.

It's not just that this unweathered
ash is not very fertile,

but it's also so loose that it's
difficult for plants to get root.

But that possibility
is always here.

Here, for example, in this crevice,
there are the seeds of the willow herb,

or, as they call it in these parts,
fireweed,

that have been blown up
from the valleys below.

I don't suppose these particular
ones will manage to get root here,

but in the end some plant will,

and in the end the process
of colonisation will begin.

Krakatau's child is
just 57 years old.

Its flanks too are covered
for the most part with ash,

and they're still being buried regularly
with new layers from fresh eruptions,

yet the process of colonisation
is already under way.

Not only are there giant grasses,
like this wild sugar cane,

but trees: A casuarina.

If you want to see what a whole century
of colonisation by plants can bring about,

have a look at that fragment
of old Krakatau over there.

We know from first-hand
reports that 100 years ago

there was nothing here at all
but sterile ash many feet deep.

Within three years, 34 different
species of plants had reappeared.

Ten years later there
were twice that number,

and over 100 species of
birds and insects as well.

Some seeds must have floated here
from Java, some 20 miles away,

and they still continue to do so.

Other smaller ones were
probably carried here by birds,

either on their feet
or in their stomachs.

But the ash is still here beneath the
lattice of roots of the jungle trees.

Somehow or other, rats and lizards
and pythons have all reached here.

There are now many hundreds of
different species of plants,

and the winds have assisted the passage
of great number of flying insects,

whose descendants now form
large and permanent populations,

pollinating the flowers,
feeding on their fruits,

collecting their rotting leaves
and indeed feeding on one another.

As yet there are no larger mammals,
no monkeys or squirrels,

no hunting cats or mongoose,
as there are in Java or Sumatra.

But as far as smaller
creatures are concerned,

the number of species is
increasing all the time.

And on the flanks of
volcanoes all round the world,

men clear fields and plant crops,

even though they know they
may be sitting on a time bomb.

These rice fields lie on the flanks
of one of Krakatau's near neighbours,

Gunung Agung in Bali.
Only 20 years ago it erupted,

killing 2,000 people and
leaving 150,000 homeless.

But the Balinese will not leave
fields that are so fertile

they can produce two or three
rich harvests of rice every year.

Gunung Agung, Krakatau and the rest of the
long line of violently explosive volcanoes

that run in a chain along Sumatra and
Java and rest of the Indonesian islands

stand on the line of the
crack in the earth's crust

where the basalt plate forming
the floor of the Indian Ocean

meets the partly submerged
edge of the continent of Asia.

This junction already
existed 65 million years ago,

when India was an isolated island
in the middle of that ocean.

Since then, as the ocean
floor has continued to spread,

the continents have shifted and
India has moved towards Asia.

As the two continents approached,
the sediments between them crumpled

and eventually piled
up over the junction,

so instead of the line between them
being marked by chain of volcanoes,

it's buried deep beneath an immense
range of mountains, the Himalaya.

So these great peaks of sandstone and
limestone rising five miles into the sky

are not only the highest mountains
in the world, but among the youngest.

What is more, the process
has not yet come to an end.

India is still moving north at the
rate of about two inches a year,

compacting itself ever more tightly
against the great continental mass of Asia,

and the Himalaya are, infinitesimally,
getting higher and higher.

And that is how this ammonite,
this sea-living creature,

came to rest over two
miles high in the Himalaya.

That too is the explanation
of how the Kali Gandaki river

managed to cut its way clean through the
highest range of mountains in the world.

It was flowing south from
the ancient plateau of Tibet

even before the great mass
of India collided with Asia.

As the sediments between the two land masses
buckled and rose over millions of years,

the river maintained its course,

cutting down through the
rocks as swiftly as they rose.

And so now it still flows
south to the plains of India,

and does so through the
deepest gorge in the world.

Mountain ranges have been created in this
way several times during history the Earth.

The Himalaya are
just the most recent.

As they are worn down, so they
create different environments

in which animals
and plants can live.