All language subtitles for How the Earth Was Made HC 720p HDTV S01E13 The Alps EN OK

Earth, a 4.5- Billion-year-old planet,
still evolving.

As continents shift and clash, volcanoes
erupt, and glaciers grow and recede,

the Earth's crust is carved
in countless, fascinating ways,

leaving a trail
of geological mysteries behind.

In this episode, Europe's greatest
mountain chain, the Alps, is explored.

Home to some of Europe's
highest peaks, longest glaciers

and sheerest rock faces,
the Alps are one of the most

dynamic and dangerous
mountain ranges on the planet.

A mysterious land where whole
mountains collapse in on themselves,

and where its rocks once lay entombed
at the bottom of the sea.

Scientists have been hunting for clues
hidden inside the rocks,

deep within the ice, and upon some of
the most famous summits in the world

to understand how the Alps formed
and continue to evolve.

Clues which also provide a window

into the formation of the Earth itself.

With more than 100 peaks
rising higher than 12,000 feet,

the majestic Alps tower over Europe.

The mountains
are a huge physical barrier.

750 miles long, 125 miles wide,
and spanning seven countries,

the Alps divide Northern
and Southern Europe.

Home of the iconic Matterhorn and
Western Europe's tallest mountain,

Mont Blanc, the Alps are one of the
world's highest mountain ranges.

But the majority of these peaks
formed only 30 million years ago,

making it one of the youngest
mountain ranges on Earth.

And for centuries, geologists have pored
over these fabulous rock formations

to figure out how mountains are made.

But the first person to uncover
a crucial clue to the Alps' formation

was, surprisingly, a 16th-century
Renaissance man, Leonardo da Vinci.

He was not only a great artist,
he also had a brilliant scientific mind.

Da Vinci was a natural detective
who saw the world around him

as a huge mystery waiting to be solved.

He focused his inquisitive,
scientific mind on the Alps

at a time when most scholars
believed the Earth was flat.

Da Vinci had heard tales
of an extraordinary discovery

embedded in the rocks,

and in 1510, he trekked high
into the mountains to take a look.

At 7,000 feet,
he found what he'd been looking for.

Fossils.

He knew these creatures
came from the sea,

that they could not have lived in the Alps.

So how did they get there,

more than 100 miles
from the nearest ocean

and thousands of feet above sea level?

The 16th-century explanation provided
by the powerful Catholic Church

decreed that the marine fossils
must have been washed up

during the time of Noah in 2300 BC.

The holy scriptures describe how God,

sickened by the wickedness
of mankind,

inflicted a terrifying deluge of water
upon the Earth.

All forms of life were annihilated,
except those sheltering on Noah's Ark.

(THUNDER)

The great torrent of water
that flooded the Earth

must have washed some of the
sea creatures 100 miles inland.

But da Vinci did not believe
this explanation

and continued his investigation
as to how the fossils got there.

In the S�ntis Mountains,
northern Switzerland, 500 years later

and 7,000 feet above sea level, it's still
possible to see the fossilised remains

of sea creatures
that so intrigued da Vinci.

Here we have a rock
which is almost covered with fossils,

for example, here,
a cross-section of a clam.

Here below,
we have the skeleton of a coral.

Poring over the fossils, da Vinci carried
out an ingenious piece of detective work.

He found the fossilised remains
of two-shelled creatures

that amazingly still had
both halves intact.

If the Church's explanation
of a cataclysmic flood were true,

then the torrent of water would have torn
these delicate creatures apart.

Da Vinci proposed that these fossils
had formed under the ocean,

and that some other force had
brought them high into the mountains.

Modern-day scientists have identified
the species fossilised in these rocks,

and can accurately pinpoint
when they lived.

The fossils we see here
actually lived 100 million years ago

in a warm, tropical sea.

This ancient, tropical sea
teemed with life and rich coral reefs.

The sea floor was covered in urchins,
clams and other species,

many now extinct.

Just as da Vinci had imagined,

when some of these creatures died,
they were preserved intact.

Their shells then became buried in
the sediments at the bottom of the sea

and preserved as fossils
when the sediment turned to rock.

But what could these fossils reveal
about the formation of the Alps?

Again, it was da Vinci's
exceptional powers of observation

that helped unravel the mystery.

He noticed that the spectacular
fossil-bearing rock,

known as limestone, was laid down
in layers several thousand feet deep.

400 years later, it was discovered
that, along with the fossils,

hidden in the microscopic structure
of limestone is an essential clue

to solving the mystery
of how the Alps formed -

remains of trillions upon trillions
of seashells.

Limestone forms as tiny sea creatures
sink to the bottom of the ocean.

Piling on top of one another,

they compact together under
their vast accumulated weight,

forming layer upon layer
of sedimentary rock.

The S�ntis Mountains,
like large areas of the Alps,

are made almost entirely of the shells
of dead sea creatures.

Beds of limestone here are
several thousand feet high -

evidence of the extraordinary amount
of sediment

that was laid down
on the ancient sea floor.

We have here
a massive package of limestone,

layer above layer of sea floor,

and this was brought up
in an upright position

during the building
of the Alpine mountain chain.

Ancient clues reveal the origin
of the Alps.

Marine fossils are evidence that
these rocks were once covered

by a tropical sea.

And rocks made from trillions
of microscopic seashells

reveal how entire mountains formed
from sediments laid down in the ocean.

Da Vinci suspected that part of the Alps
had formed beneath the ocean,

but how had these originally flat layers
been upended?

Leonardo's explanation
was that some kind of force

have brought the fossils
high up to the mountains.

But he actually couldn't explain then
the driving forces of this movement.

After da Vinci, it would take
scientists another 400 years

before that part of the mystery
was solved.

The Alps.

This jagged backbone of Europe was
lifted thousands of feet above sea level

and 100 miles inland.

Many of the Alpine rocks
once lay flat on the sea floor.

An extraordinary force twisted,
folded and turned this land upside down.

But what was this force and how could
it move great swathes of solid rock?

In the 1870s, Swiss geologist Arnold
Escher and his student Albert Heim

were drawn to a strange line etched
in the Tschingelhorn mountain.

They traced the line for 30 miles.

Out of reach for most of its range,
they found one location

where this line can be examined
in close-up

near the village of Elm,
Eastern Switzerland.

The dark line can clearly be seen here
beneath this strange overhang.

Above it, Escher and Heim identified
a layer of ancient sedimentary rock.

But strangely, beneath the line they
found a layer of much younger rock.

Underneath we have here

the flysch, these are slates

which are about 35 million years old.

And on top we have the Verrucano,

which has formed about
260, 270 million years ago.

Escher and Heim were confused.

The rock formations
simply did not make sense.

If both layers were formed
by the build-up of sediments,

how could older rock
lie above the younger one?

Studying the twists and folds
in the surrounding mountains,

Escher and Heim came up with a theory
as to how these rocks switched places.

Just imagine we have
one big sheet of sediments.

And one part of the sediment of
this sheet is pushed over the others.

That's the way we get older sediments
on younger sediments.

A gigantic horizontal force pushed these
older rocks a distance of 30 miles

over the younger layers.

The line between them,
where the rocks scrape over each other,

is called an overthrust.

Escher and Heim's discovery
revolutionised our understanding

of how mountains are made.

This outcrop, actually it's a close-up

of maybe the most famous overthrust
in the world,

the so-called Glarus Overthrust.

And there are only a few places
where you can go... uh, go so close to it.

This site is merely a close-up
of a massive geological phenomenon

that created the Alps.

Sitting above the Glarus Overthrust
is a mountain range

with peaks over 11,000 feet high.

It's a reminder that some
awesome power created the Alps,

a force that can literally
move mountains.

But what has the power to push
billions of tons of rock?

Scientists now know that such
a colossal process can only happen

when two continents collide,
driven by the forces of plate tectonics.

Plate tectonics is the process
by which giant plates of the Earth's crust

move slowly across the planet's surface,
propelled by vast currents of molten rock

deep within the Earth.

As this happens over millions
of years, continents collide

and split apart
and oceans form and disappear.

But if the Alps formed as a result
of a massive collision,

what continent
had crashed into Europe?

The answer lies entombed in one
of the Alps' most famous landmarks.

Hidden by clouds,
it's frequently hard to see.

There it is, finally.

The Matterhorn's unique shape

has made it one of the best-known
mountains in the world.

At 14,692 feet, it's one
of the Alps' highest peaks.

Hidden within the body of this mountain
is another major overthrust.

Here, rocks from the sea floor
lie above the European bedrock.

Taking a closer look at the layers
formed under the sea,

Dr Hellwig finds a green-tinged rock.

The rocks we're looking at here
are called green schists.

These coarse crystals reveal
that this rock erupted as lava

at the bottom of the ocean,
100 million years ago.

But in the early 20th century,

scientists discovered something
even stranger.

An unusual layer of rock
caps the mountain.

This upper layer is a grey rock
called gneiss.

But when geologists
traced the origin of this rock,

they found it did not come from Europe,

and was 200 million years older
than rocks from the sea floor.

This rock belonged to
a two-billion-year-old continent

600 miles to the south - Africa.

The upper section
of this Alpine sandwich,

it consists of rock
which come from Africa.

The middle part, um, are the rocks
from the oceanic crust

and the lower part, then,
are the European rocks.

This is evidence that the Alps formed

because ancient Africa
collided with Europe.

The result?

This whole mountain is composed
of three rock types.

From a geological standpoint,

it nicely combines the whole
Alpine story, so it shows all the...

...shows the most important aspects
of the Alpine history,

right there within one mountain.

But how exactly did rocks
from the sea floor get sandwiched

between two continents?

Detailed studies and dating
of the Alpine rocks

have revealed that, 90 million years ago,

Africa pushed
towards Europe,

squashing an ancient sea,

the Tethys Ocean,
that lay between them.

As Africa ploughed
into Europe,

it first destroyed the ocean

that lay between them

and... and piled it up
in... in thin slices,

much as a bulldozer
tears up

the ground in front of it.

These slices were then piled
in front of the, uh... the bulldozer

that makes up Africa.

So we began to develop this
large pile of deformed rock

that is what today forms the Alps.

The ocean floor was crumpled in front
of the advancing African continent,

bending, folding
and breaking as it went.

30 million years ago, the Alps
were literally pushed up onto Europe.

Africa was thrust over
and above the other layers,

to form the sandwich of rocks
that would become the Matterhorn.

A jumble of rocks had been folded
and moulded by violent processes,

and uplifted 22,000 feet,
as high as the Himalayas today.

Scientists investigating how
the Alps rose up off the ocean floor

have uncovered a 30-mile line
in the rocks,

the boundary between older rocks
thrust above younger ones.

And grey gneiss rocks
at the top of the Matterhorn

prove that Africa collided with Europe,
creating the Alps.

But for the last 30 million years, some
other monumental force has eaten away

these great peaks.

What has caused this entire mountain
range to lose nearly half its height?

30 million years ago, the Alps' highest
peaks towered 22,000 feet into the air.

Today, the tallest peaks
are almost half this height.

Unravelling the mystery of why and how
the Alps are disappearing

is important to the 14 million people
who live in and around them.

Illhorn mountain,
an extraordinary peak in the Swiss Alps,

provides an essential clue.

This mountain is almost 9,000 feet tall,
but hollow at its centre.

Illhorn is rotten to the core.

This massive hole is forming
as the mountain collapses in on itself.

But what monumental force
is pulling this mountain down?

It's made of a loose, unstable
mixture of rock and mud

that originally came from the ocean floor.

In winter, this mixture of rock
is glued together by ice,

but in the spring thaw, it becomes loose.

Here you can see the fact
that the rocks are very highly weathered,

you can easily, uh, in fact
by hand, pull them apart,

you can imagine that, uh...

...in winter when the ice,

when the water goes behind the rocks
and freezes,

that it could actually mechanically,
uh, loosen the rocks,

and in the spring they fall down.

The whole mountain
is composed of these rocks,

it's basically just falling apart.

A combination of weak rocks and the
natural action of freezing and thawing

has resulted in a crumbling mountain.

In the last 10,000 years, 100 million tons
of Illhorn mountain has eroded

and in the process hollowed out
a vast new valley, the lllgraben.

But where has all the rock gone?

Dr McArdell has come to explore
a deep, seemingly dry riverbed,

which runs down from the heart
of the mountain

and into the river Rhone.

The evidence is hidden beneath
the village and vegetation -

a large, fan-shaped platform of rubble,

1,500 feet deep
and over one mile square.

This structure is built from the sediment
delivered by the lllgraben catchment.

All the sediment that you see
has come down from the mountain.

But this dry riverbed
presents a mystery.

How did vast amounts of debris get
transported down from the mountain?

The Swiss village of Susten,
ground zero for the investigation,

is in a constant state of alert.

A few times a year,
the ground shakes here

as if a gigantic freight train
is thundering through the village.

(RUMBLING)

(SIREN WAILS)

In a flash, this dry channel
is flooded by a river of rock.

Thousands of tons of debris flow
down from the Illhorn mountain.

McARDELL: Anywhere between
three and five times a year,

there's a large wave of sediment
moving downstream

at anywhere
from 10 to 20 miles an hour,

with a flow depth on the order
of up to 10 feet.

And it moves down the channel rapidly
and anyone who's in the channel,

of course, is in danger.

Every time it rains,
debris cascades down the mountainside,

making this one of the most
active debris flow zones on Earth.

The Alps are basically being
washed down from the mountains,

through the rivers and into the lakes,
into the valleys further downstream.

Illhorn is an extreme case of an entire
mountain in the process of decay,

resulting in one of the most dangerous
mountain terrains on the planet.

But inherently unstable rocks
are found right across the Alps,

and have created some of
the Alps' best beauty spots.

Oeschinensee lake is a mile
above sea level and half a mile square.

But in theory, this lake shouldn't be here.

The streams
that pour off the mountain

should run straight down
the valley unobstructed.

A clue to what created this
high-altitude lake can be found

1,000 feet up on the surrounding slopes.

As we look up on the hill slopes,

we see these very large
fans of debris

that are coming down off
of these unstable slopes.

Where we see this sort of smooth
bedrock that's dipping towards us,

this is prime territory for landslides.

When these mountains formed,

flat sheets of sedimentary rock
were thrust up to rest at extreme angles.

The joins between these stressed
and fractured rock layers frequently fail,

causing huge layers of rock
to shear off the cliff faces.

Much of these open slopes are
probably the result of sheets of rock

peeling off and forming large landslides.

It was a catastrophic landslide

that caused this lake
to form 15,000 years ago.

The entire side of the mountain
sheared off, blocking the valley

and causing stream water to back up

and create one of the Alps'
most breathtaking landscapes.

It's all about gravity,

gravity is what ultimately
brings down mountains.

Rivers come in, debris flows form,
landslides form,

and this sort of process is very common
throughout the Alps.

Steep slopes and unstable rocks
have created a mountain range

that is ever-changing.

In only a few thousand years,

gravity will also destroy Oeschinensee
lake, as debris flows fill it up.

Over the last 30 million years, the Alps
have fallen down on a massive scale,

in places decreasing
in height by 10,000 feet.

So what has happened
to those thousands of feet

and billions of tons of missing rock?

A clue can be found in the rolling hills
a few miles north of the Alps.

At Eggiwil, this rock outcrop contains
an extraordinary collection of stones.

These are large cobbles, stones
that have come from all over the Alps,

so if I look at some of these, for
example, this small white and black rock,

this is a granitic rock that comes
from the centre of the Alps,

somewhere very close to the Matterhorn.

And we see, throughout this outcrop,

rocks that come from different parts
of the Alps.

Rocks from hundreds of
different scattered locations

have travelled over 150 miles

before being dumped
in this geologic rock graveyard.

But it's the amount of material
here that's mind-boggling.

These hills are made entirely of
rock debris from the nearby Alps.

At 100 miles wide and 500 miles long,
they stretch in an arc round the Alps,

running through France,
Switzerland and Germany.

There's enough material here to cover all
of North America in 100 feet of rubble.

Could this be where the thousands of
feet of missing Alpine rock have gone?

A big mountain
range like the Alps is heavy,

and it weights down the crust,

forming a depression all the way
around the mountain range.

A multi-trillion-ton mass of rock
was pushed up on land

as Africa collided with Europe,
creating the Alps.

The weight of the rock caused
the European crust to sink,

making a huge depression, in places
over two and a half miles deep -

the Molasse basin.

Now, the importance of this depression
is it's a trap,

all the sediment that we see
eroding off of the Alps

is trapped in this basin
and ends up sitting there.

Dating of these pebbles has revealed
that, ever since the Alps were created,

rivers have washed Alpine debris
hundreds of miles downstream,

dumping the rocks in this gigantic basin.

So these rocks that we're
looking at here are the debris,

the detritus that's come off of the Alps
over the last 20, 30 million years,

these particular rocks
are almost 25 million years old.

And what we see are cobbles, we see
little pieces of all the different rocks

that we see throughout the Alps.

For 30 million years, the debris eroded
from the Alps has been dumped

in a 30,000-square-mile bowl,
creating this rolling chain of hills

to the north of the Alps.

This is where
the missing mountain rock is.

Put it all back together and once again,

there'd be mountains
as high as the Himalayas.

Scientists have discovered how
the Alps have almost halved in height

and where the missing rocks
have disappeared to.

The clues are, inherently
unstable mixtures of rock,

resulting in whole mountains falling
apart, debris flows on steep cliffs,

proof that weakened layers of rock
shear off from the mountainsides,

and a graveyard of pebbles
from all over the Alps,

evidence that these mountains
have been washed away.

But then, two million years ago,
the landscape changed dramatically.

Vertical cliffs were carved into the Alps

and giant spikes of rock
poked through the clouds.

Another mighty force
had begun to resculpt the Alps.

Over the last two million years,
a blink in geologic time,

something has rapidly
and radically transformed the Alps,

gouging giant peaks
and sheer rock faces.

The most notorious rock formation
being the Eiger, in southern Switzerland.

The infamous north face of the Eiger
is a 6,000 foot vertical climb.

It's a terrifying, unrelenting ascent.

Climbers face gale-force winds,
freezing fog, rockfalls and avalanche,

giving the Eiger the reputation as one of
the most formidable climbs in the world.

Nicknamed the Murder Wall,

since 1935, more than
60 climbers have died here.

How giant climbing walls like this were
formed had been a mystery to geologists

until 1837, when Swiss scientist
Louis Agassiz noticed similar cliffs

at lower altitudes, known to have been
made by a colossal force - glaciers.

Over 1,000 glaciers wind their way
through the Alpine valleys.

Imperceptible to the naked eye, these
giant rivers of ice slowly flow downhill.

This time-lapse of the Aletsch glacier,
taken over a period of three years,

reveals how glaciers
can move tens of feet a year.

And where two glaciers meet,
a stripe of rock sits on the surface,

proof that something extraordinary
is happening beneath the ice.

A force which can transform jagged rock
into a surface as smooth as glass.

We see here a smooth rock face
which was formerly covered by ice.

Underneath the ice, there is this
rocks and sand, and it carries...

...the ice carries this stuff with it

and it acts like sandpaper
and polished this rock.

But polishing alone cannot account for
the formation of the Alps' jagged peaks

and the north face of the Eiger,

where the sides of entire mountains
have been ripped off.

More evidence of the awesome power
of glaciers

can be found on these granite slabs.

Deep cracks penetrate
the body of the rock.

The ice was flowing over this rock face
and the ice could enter this crack.

Meltwater forming beneath the glacier
seeps into the cracks,

refreezes and splits open the rock.

Weakened and fractured, huge chunks
of stone are ripped from the bedrock.

Vast amounts of rock are plucked
and ground from the mountainsides

and dumped in the lower,
warmer valleys when the ice melts.

So here we are at the end,
the snout of the glacier.

And here debris, water,
and rock boulders.

This has been eroded by the glacier,
transported and moved to this place

and this is the essential process,
how glaciers form the landscape.

But how could glaciers have carved
the north face of the Eiger,

and other mighty peaks
which rise thousands of feet

out of reach of the abrasive ice below?

Agassiz came up with a radical theory.

He noticed these high rock faces
were scarred and gnarled.

They had clearly been gouged by ice,

like the glaciated valleys
he'd found at lower altitudes.

Piecing the evidence together,

he concluded towering cliffs
like the 6,000-foot Eiger

were the handiwork
of ancient, gigantic glaciers.

But if Agassiz was right, where
did the huge glaciers come from?

The evidence lies locked inside
Europe's biggest river of ice,

the Aletsch glacier.

A massive 14 miles long, it covers
an area of more than 45 square miles

and is up to 3,000 feet deep.

The Aletsch glacier
in southern Switzerland

has helped scientists understand
how all Alpine glaciers form.

The source of the glacier
is high up in the mountains,

where altitude brings freezing
temperatures and heavy snowfall.

To explore how delicate snowfall
becomes a giant slab of ice,

Dr Bauder ventures
deep into the heart of the glacier.

This frozen passageway, 32 degrees
Fahrenheit and 60 feet deep,

offers tourists and scientists
a unique window

into the formation of a glacier.

Here we can see
the inside of a glacier.

We can see inside the ice.
We see here layers of air bubbles.

And there are different,
distinct layers visible here, here, here,

and they represent individual years
when this ice has been formed.

The glacier grows by the build-up
of layer upon layer of snow.

The newly fallen snow traps pockets of
air between the individual snowflakes,

forming layers of bubbles.

As more snow settles,
the flakes beneath become squashed,

making them stick together to form ice.

Forming over thousands of years,

the amount of ice contained in
a single glacier can be staggering.

It's been estimated that the Aletsch
glacier holds 27 billion tons of water,

enough to provide every human on
Earth with two pints of water a day

for the next six years.

It's the air bubbles, trapped
inside the ice thousands of years ago,

that hold the key to what carved
the Alps' distinctive shape.

In the air bubbles,

air is stored from the time when
the air bubbles have been formed.

So we can analyse
the chemical composition inside there

and learn about the climatic condition
at that time.

When scientists analysed
miniature time capsules like these,

they found air over 12,000 years old,

with surprisingly low levels of
the greenhouse gas carbon dioxide.

This meant that more heat was
escaping from the Earth's atmosphere,

causing global temperatures
to plummet.

Similar studies have revealed
that, for the last two million years,

the Earth has been gripped
by a series of ice ages.

Agassiz' theory was confirmed.

Two million years ago,

an enormous ice sheet engulfed
the Earth's northern hemisphere.

The Alps were buried in ice
almost two miles thick.

It was so deep that
only the tips of the mountains

poked out above the ocean of ice.

As the ice moved,
it whittled lone peaks

and tore steep rock faces
high in the Alps,

leaving its legacy on the landscape.

It was during this time

that giant glaciers carved
the infamous north face of the Eiger.

In their mission to discover how
the Eiger and other great peaks

in the Alps formed, scientists
have found cracks in granite bedrock,

evidence that glaciers cleave masses
of rock from the mountainsides,

and low levels of carbon dioxide,
trapped inside ice bubbles,

prove that giant glaciers once carved
immense rock walls and pinnacles,

which now tower over the landscape.

10,000 years ago,
the great ice sheets melted,

leaving their mark on the Alps.

But today, the Alps are falling down
at a phenomenal rate.

Something has propelled them into a
new and violent phase of their evolution.

The Alps are falling down
at an accelerated rate.

And millions of tons of rock
are crashing to Earth.

A clue to what strange force
is at work here

can be found high up in the mountains,

where the remnants
of the last ice age lurk.

Alpine glaciers physically prop up
mountains, binding the rock together.

But these icy rivers are changing shape.

Well, what we see in the background
here are glaciers

which are separated, uh, by rocky
surfaces which are looking very fresh

because they have been ice covered
in the last, uh, few hundred, uh, years.

Uh, if you look across here
to Theodul glacier, we can see

that actually, right next to the ice, uh,
there is some, uh, greyish material

next to the brownish material.

That's exactly the limit up to where
the glacier was, uh, in 1874.

So you see how much of this ice has
melted down in these 130, uh, years.

Scientists believe global warming
is melting the ice

faster than at any other time
in the Alps' history.

And as the glaciers shrink,
they expose steep, unsupported cliffs

that are prone to fall down,
increasing the risks of landslides.

But scientists have discovered

another way melting glaciers
are weakening the Alps.

When these frozen reservoirs melt,

millions of gallons
of water gush downhill,

feeding the great rivers of Europe.

Like liquid sandpaper,
this torrent scrapes over the rocks,

hollowing out the land
at an accelerated rate.

The dramatic evidence of this
dynamic process can be found

in the valley of Lauterbrunnen.

Echoing through this valley
is the sound of one of the loudest

and most spectacular water features
in the Alps, Tr�mmelbach Falls.

You can just feel
the pulsing of the water.

This is... the name Tr�mmelbach

actually means drum sound,

and this is reflecting this, this pulsing,
throbbing that we can hear and feel

from the water flowing down
through these caves.

Tr�mmelbach
is a spectacular glacial waterfall.

Over 5,000 gallons of meltwater
a second hurtle down from glaciers

on the nearby Eiger
and Jungfrau mountains.

Over hundreds of years,
this abrasive jet-stream

has sliced through the mountain,
creating a narrow canyon.

Each year, from the Swiss Alps alone,
there's enough rock removed

by the glacial meltwaters to create
a mountain more than half a mile high.

But Tr�mmelbach, like other Alpine
waterfalls, is living on borrowed time.

As meltwater thunders down
the waterfalls,

it cuts into the rock, weakening it.

Over time, these steep cliffs
left by the glaciers crumble,

replaced by ever deepening river valleys.

WILLOTT: Today,
the rivers that are now returning

are trying to carve a river valley,

which has a very different shape and
different form, changing this landscape.

All of these processes
come in and destroy that high relief

that the glaciers have left behind.

Very dynamic processes,
very rapid erosion, very rapid processes

that cannot be sustained
over geologic time.

For the last 150 years, global warming
and the resulting glacial melt

has caused a huge amount of erosion.

Experts warn,
if this warming trend continues,

the Alps will be ice free
by the end of the century

and fear these great mountain peaks
will tumble down even faster.

Weakened rocks and the increased risk
of catastrophic landslides

could spell disaster for villages
and resorts high up in the Alps.

But a look back to ancient times

reveals that the Alps
have been in meltdown before.

In the autumn of 218 BC,

the mighty Hannibal led an army
of 50,000 men and 40 elephants

across the Alps to attack the Romans.

An arduous 15-day trek across
the most treacherous terrain in Europe.

Many men fell to their deaths
along the perilously narrow tracks.

But Hannibal's audacious plan paid off.

His army pushed on through Italy
to defeat the Romans.

Today, Hannibal's route
is virtually impassable,

blocked by ice and deep snow.

Scientists realised that
when Hannibal crossed the Alps,

the mountain passes
must have been ice free

and the glaciers must have retreated
further back than they are today.

It may have been a bit of a walk through
the forest for him,

at least much of the way,
and certainly a... an easier time

to travel through the Alps than
we would have today, for example.

Past changes
in the Earth's tilt towards the sun

have caused glaciers
to melt and refreeze

in response to a fluctuating climate.

If history repeats itself, glaciers
will, sometime in the distant future,

naturally return to the Alps.

WILLOTT: These advances
and retreats of the ice

are very important to the overall rate
at which the Alps are being eroded.

It's this natural cycle from glaciers
carving cliffs, to rivers cutting valleys,

and back again, that has created
a mountain range that is ever-changing.

And it's this natural process

that will ultimately destroy the Alps
as we know them.

The Alps are
slowly being destroyed.

We'll probably see more glacial
advances and retreats

that will begin to erode them down.

So, if we were to come back
in 10, 20, maybe 100 million years,

we would still find a mountain range
here today.

The Appalachians of Eastern U.S.,
for example,

remain a... at least a small,
subdued mountain range,

and that will be the future of the Alps.

The Alps will shrink to half its size

and become a mountain chain
less than 6,000 feet high.

Stunted in height, no glaciers
will cap these mountains,

nor feed the great rivers of Europe.

Millions of years from now,
the vast lowlands of France,

Germany and Eastern Europe
could one day be barren and parched.

Scientists have discovered
how the Alps formed

and why they're tumbling down.

Marine fossils and limestone made
from trillions of seashells are proof

that Alpine rocks formed
at the bottom of the sea.

Grey gneiss rocks at the top
of the Matterhorn are evidence

that Africa collided with Europe,
forming the Alps.

Landslides are proof
that sedimentary layers,

and sometimes whole mountains,
are inherently weak and collapsing.

Gases trapped in ancient
ice bubbles reveal

that giant glaciers carved out
the rugged landmarks of the Alps.

And shrinking glaciers and waterfalls are
weakening the Alps, creating a skyline

which is constantly changing.

Since they were created,
the Alps have continued to evolve.

One of the most varied,
spectacular

and intensely studied
mountain ranges on Earth,

understanding how the Alps were made

has unlocked deep secrets

of the powerful forces
that shape our planet.