>> 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 rock
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.
S01x13 The Alps Original Air Date on May 12, 2009
== sync, corrected by elderman ==
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 red 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.
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 Säntis Mountains,
northern Switzerland, 500 years
later and 7,000 feet above sea
level, it's still possible to
see the fossilized 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 fossilized 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
fossilized 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 Säntis 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 closeup 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 buildup 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
revolutionized our
understanding of how mountains
are made.
>> This outcrop, actually it's a
closeup 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
closeup 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 gray 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 molded 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 gray 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.
Unraveling 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 Illgraben.
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
Illgraben 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.
In a flash, this dry channel is
flooded by a river of rock.
Thousands of tons of debris flow
down from the Illhorn mountain.
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--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 center 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 traveled 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 tether,
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,
erm, ice has been formed.
>> The glacier grows by the
buildup 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 analyze the chemical
composition inside there and
learn about the climatic
condition at that time.
>> When scientists analyzed
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,
grayish 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
fast than at any other time in
the Alps' history. And as the
glaciers shrink, they expose
steep, unsupported cliffs that
are prone to fall do,
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,
Trümmelbach Falls.
>> You can just feel the pulsing
of the water. This is--the name
Trümmelbach 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.
>> Trümmelbach 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 Trümmelbach, 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.
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 lead 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
realized 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.
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 ten, 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. Gray 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.