Human beings venture into the highest parts of our planet at their peril.
Some might think that by climbing a great mountain,
they have somehow conquered it.
But we can only be visitors here.
This is a frozen, alien world.
This is the other extreme -
one of the lowest, hottest places on Earth.
It's over 100 metres below the level of the sea.
But here a mountain is in gestation.
Pools of sulphuric acid are indications
that, deep underground, there are titanic stirrings.
This is the Danakil Depression in Ethiopia,
lying within a colossal rent in the Earth's surface,
where giant land masses are pulling away from one another.
Lava rises to the surface through this crack in the crust,
creating a chain of young volcanoes.
This one, Erta Ale,
is today the longest continually-erupting volcano on the planet,
a lake of lava that has been molten for over 100 years.
These same volcanic forces also created Ethiopia's highlands.
70 million years ago,
this land was just as flat and as deep as the Danakil Depression.
Molten lava, rising from the Earth's core,
forced up a huge dome of rock 500 miles wide -
the Roof of Africa.
Over millennia, rain and ice carved the rock
into a landscape of spires and canyons.
These summits, nearly three miles up,
are home to some very remarkable mountaineers...
gelada baboons.
They are unique to the highlands of Ethiopia.
The cliffs where they sleep are for expert climbers only
and geladas certainly have the right equipment -
the strongest fingers of any primate and an utterly fearless disposition.
But you need more than a head for heights to survive up here.
A day in the geladas' life reveals how they have risen to the challenge.
For all monkeys,
morning is grooming time -
a chance to catch up with friends.
But unlike other monkeys,
geladas chatter constantly while they do it.
It's a great way to network while your hands are busy.
These socials can't go on for too long.
Geladas have a busy daily schedule and there is work to be done.
Most monkeys could not live up here.
There is no fruit and few insects to feed on.
But geladas are unique.
They are the only monkeys in the world
to live almost entirely on grass.
They live in the largest assemblies formed by any monkeys.
Some groups are 800 strong...
and they crop the high meadows like herds of wildebeest.
The geladas graze alongside Walia ibex,
which are also unique to these highlands.
These rare creatures are usually very shy,
but they drop their guard when the geladas are around.
You might expect that grazers would avoid each other's patch,
but this is a special alliance from which both partners benefit.
It's not so risky to put your head down...
if others are on the look-out.
Ethiopian wolves.
They won't attempt an attack in broad daylight.
But, at dusk, the plateau becomes a more dangerous place.
With the grazing largely over,
there is a last chance to socialise
before returning to the sleeping cliffs.
BABOONS HOWL
An early warning system puts everyone on the alert.
BABOONS HOWL
Their day ends as it began, safe on the steep cliffs.
The Ethiopian volcanoes are dormant,
but elsewhere, others still rage.
Volcanoes form the backbone
of the longest mountain chain on our planet -
the Andes of South America.
This vast range stretches 5,000 miles
from the equator down to the Antarctic.
It formed as the floor of the Pacific Ocean
slid beneath the South American continent, buckling its edge.
At the southern end stand the mountains of Patagonia.
It's high summer.
WIND WHISTLES
But the Andes have the most unstable mountain weather on the planet
and storms can erupt without warning.
Temperatures plummet and guanacos and their newborn young
must suddenly endure a blizzard.
Truly, all seasons in one day.
A puma...
the lion of the Andes.
Pumas are usually solitary and secretive.
To see a group walking boldly in the open is extremely rare.
It's a family - a mother with four cubs.
She has just one brief summer
in which to teach them their mountain survival techniques.
Rearing four cubs to this age is an exceptional feat,
but she does have an excellent territory, rich in food and water.
Although the cubs are now as large as their mother,
they still rely on her for their food.
It will be another year before the cubs can hunt for themselves.
Without their mother's skill and experience,
they would never survive their first winter.
Battered by hurricane-force winds,
these slopes are now lifeless.
Further north, they hold other dangers.
Moving at 250mph,
an avalanche destroys everything in its path.
In the American Rockies,
100,000 avalanches devastate the slopes every winter.
This huge mountain chain continues the great spine
that runs from Patagonia to Alaska.
The slopes of the Rockies, bleak though they are,
provide a winter refuge for some animals.
A mother grizzly emerges from her den
after six months dozing underground.
Her two cubs follow her
and take their first steps in the outside world.
These steep slopes provide a sanctuary for the cubs.
A male bear would kill and eat them, given the chance,
but big animals find it difficult to get about here.
Males may be twice the size of a female
and even she can have problems.
Her cubs, however, make light of the snow...
and of life in general.
But the mother faces a dilemma.
It is six months since she last fed
and her milk is starting to run dry.
She must soon leave the safety of these nursery slopes
and lead her cubs away from the mountain.
If she delays, the whole family will risk starvation.
Summer reveals the true nature of the Rockies.
Stripped of snow,
the peaks bare their sculpted forms.
Only now can mountaineers reclaim the upper reaches.
Two miles up,
the crumbling precipices seem devoid of life.
But there ARE animals here.
A grizzly bear.
It seems to be an odd creature to find on these high rocky slopes.
It is hard to imagine what could have attracted it here.
At this time of the year,
bears should be fattening up for the winter,
yet they gather in some numbers on these apparently barren slopes.
They are searching for a rather unusual food.
Moths!
Millions have flown up here to escape the heat of the lowlands
and they are now roosting among the rocks.
Moths may seem a meagre meal for a bear,
but their bodies are rich in fat
and can make all the difference in a bear's annual struggle for survival.
Another battle is being waged here,
but on a much longer timescale.
These loose boulders are the mountain's crumbling bones.
The Rockies are no longer rising, but slowly disintegrating.
All mountains, everywhere,
are being worn down by frost, snow and ice.
The Alps were raised some 15 million years ago
as Africa, drifting northwards,
collided with the southern edge of Europe.
These spires are the eroded remains of an ancient sea bed
that once stretched between the two continents.
But these are just the Alpine foothills.
The range at its centre rises to three miles high
and is crowned with permanent snows.
The Matterhorn - its summit too steep to hold a snowfield.
Mont Blanc - the highest peak in western Europe.
The distinctive jagged shapes of the Alps
were carved by those great mountain sculptors...the glaciers.
Immense rivers of moving ice, laden with rock,
grind their way down the mountains, gouging out deep valleys.
They are the most powerful erosive force on our planet.
A moulin - a shaft in the ice opened by melt water
as it plunges into the depths of the glacier.
Like the water running through it, the ice itself is constantly moving,
flowing down the valley with unstoppable force.
Alpine glaciers may seem immense,
but they are dwarfed by those in the great ranges
that divide the Indian sub-continent from Tibet.
This is the boulder-strewn snout of the giant Baltoro Glacier
in the Karakoram mountains of Pakistan.
It's the biggest mountain glacier on Earth,
43 miles long and over three miles wide.
This huge ice-filled valley is so large
it is clearly visible from space.
This is the greatest concentration of peaks over five miles high
to be found anywhere on Earth.
They are the most dangerous mountains of all.
K2 and her sister peaks
have claimed more lives than any others.
The peaks here rise so precipitously,
the glaciers are so steep and crevassed,
that few except the most skilled mountaineers
can penetrate these ranges.
Markhor gather for their annual rut.
Males must fight for the right to breed,
but on these sheer cliffs, any slip by either animal could be fatal.
A snow leopard -
the rarest of Himalayan animals.
It's a female returning to her lair.
These are the first intimate images
of snow leopard ever filmed in the wild.
She greets her one-year-old cub.
Her den is well chosen.
It has exceptional views of the surrounding cliffs.
On these treacherous slopes,
no hunter other than the snow leopard would have a chance
of catching such agile prey.
A female with young makes an easier target.
Her large paws give an excellent grip
and that long tail helps her balance.
Silently, she positions herself above her prey.
She returns...with nothing.
Golden eagles patrol these cliffs,
in search of the weak or injured.
With a two-metre wingspan,
this bird could easily take a young markhor.
Eagles hunt by sight
and the thickening veil of snow forces them to give up
For the leopard, the snow provides cover
and creates an opportunity.
The worsening weather dampens the sound of her approach,
allowing her to get within striking distance.
It was an act of desperation to try and catch such a large animal.
Wolves have made a kill,
giving other hunters a chance to scavenge.
The worst of the blizzard brings success for the snow leopard,
but having descended so far to make the kill,
she has a gruelling climb to get back to her lair.
The cub must be patient.
It will be a year before it has the strength and skill
to kill for itself on these difficult slopes.
The snow leopard is an almost mythical creature,
an icon of the wilderness,
an animal few humans have ever glimpsed
for its world is one we seldom visit.
The Karakoram lie at the western end of a range
that stretches across a tenth of our planet...
the Himalayas.
These, the highest mountains in the world, like other great ranges,
were created by the collision of continents.
Some 50 million years ago,
India collided with Tibet,
thrusting up these immense peaks which are still rising.
This vast barrier of rock and ice is so colossal,
it shapes the world's climate.
Warm winds from India, full of moisture,
are forced upwards by the Himalayas.
As the air rises, so it cools,
causing clouds to form and the monsoon is born.
At high altitudes, the monsoon rains fall as snow.
Here at the far eastern end of the range, in China,
one inhabitant endures the bitter winters out in the open.
Most other bears would be sleeping underground by now,
but the giant panda can't fatten up enough to hibernate.
Its food, bamboo, on which it totally relies,
has so little nutritional value
that it can't build up a store of fat like other bears.
Most of the creatures here move up or down the slopes with the seasons,
but the panda is held captive by its diet,
for the kind of bamboo it eats only grows at this altitude.
These forests hold fewer challenges for the more mobile.
The golden snub-nosed monkey, like the giant panda, lives only in China.
Their thick fur allows them
to survive at greater altitudes than any other monkey
and when the cold bites, they have these upper slopes to themselves.
Even if you have a warm coat,
it apparently helps to surround yourself
with as many layers as possible.
But at least these monkeys have a choice.
If they tire of tree bark and other survival food,
they can always descend to lower, warmer altitudes
and not return until spring.
As the snows retreat, trees come into bloom.
Cherry blossom.
Rhododendrons.
Here in their natural home, they form great forests
and fill the landscape with the colours of a new season.
These forests are host to a rich variety of springtime migrants.
Beneath the blooms, another display.
It's the mating season for oriental pheasants...
Himalayan monal...
..tragopan...
and blood pheasant.
Musk deer make the most of a short flush of spring foods.
This male smells a potential mate.
The red panda...
rarely glimpsed in the wild.
It was once considered a kind of raccoon,
but is now believed to be a small mountain bear.
By midsummer, its larger, more famous relative
has retreated into a cave.
A giant panda nurses a tiny week-old baby.
Her tender cleaning wards off infection.
She won't leave this cave for three weeks,
not while her cub is so utterly helpless.
Progress is slow,
for milk produced on a diet of bamboo is wretchedly poor.
Four weeks old and the cub is still blind.
Its eyes do not fully open
until three months after birth.
But the chances of the cub reaching adulthood are slim.
The struggle of a giant panda mother to raise her cub
is a touching symbol
of the precariousness of life in the mountains.
On the highest summits of our planet, nothing can live permanently.
The highest peak of all, Mount Everest,
five and a half miles above sea level and still rising.
The roof of our world.
Of those humans who have tried to climb it,
one in ten have lost their lives.
Those that succeed can stand for only a few moments on its summit.
The Nepalese call it "a mountain so high no bird can fly above it".
But each year,
over 50,000 demoiselle cranes
set out on one of the most challenging migrations on Earth.
To reach their overwintering grounds in India,
they must cross the Himalayas.
By late morning, ferocious winds are roaring past the peaks.
The cranes must gain height to avoid the building storm.
They've hit serious turbulence.
They must turn back or risk death.
A new day and a new opportunity.
The flock stay in close contact by calling to one another.
Weak from lack of food and water, they use thermals -
rising columns of warm air -
to gain height.
For many, this is their first journey across the Himalayas.
For some, it will be their last.
The golden eagles have been expecting them.
The eagles work in pairs to separate a young crane from the flock.
It escapes the clutches of one...
and is caught by another.
But even a young crane is a heavy prize
and the eagle has to struggle to control it.
The mother can wait no longer.
This is a desperate race against worsening weather.
The rest of the flock battle on.
In the final ascent,
every wing-beat becomes an exhausting struggle.
At last, they are over the highest barrier that lies in their way.
But, like all who visit the world of the high mountains,
they dare not linger.
It's not just the scale of mountains
that makes them a daunting place to work in.
The wildlife is scarce and extremely hard to find
and it doesn't come any harder than finding and filming the snow leopard.
Scientists can spend years in the field
with barely even a sighting of this rare creature.
Planet Earth sent one of the toughest cameramen in the business
to begin a three-year quest to film it.
So, I guess you could say this is where it really starts.
We're up here in snow leopard country.
You look around and anywhere, anytime,
you might just see it.
These are big, big mountains
and there are not many snow leopards.
There it is!
There's home entrance for the next wee while.
If I take you inside, I'll show you the amenities. Very much five star!
It's actually, I think, quite comfy.
There's the bed
and I've got pretty much everything I need.
I brought some water up from the river.
True, it's a little bit, er, cramped, but it's quite enough.
And, er, all I need know are one or two pussycats.
As an insurance policy,
the crew set up remote camera traps.
Yeah, that's good. OK, Doug.
These cameras are triggered by movement
and capture images of ANY passer-by.
Am I a good snow leopard?
Erm... No, but... LAUGHTER
If a snow leopard does what you did, that'll be jolly good.
But to stand a chance of filming any behaviour,
Doug just has to sit and hide... and wait.
HE EXHALES LOUDLY
This is tedious stuff.
This is the seventh session that I've done.
I do three hours in the morning, three hours in the late afternoon.
No' a sign!
If you got just a little bit of hint,
a wee bit of a sighting now and again,
your spirits would be lifted.
But right now, I'd swap a little bit of this animal's charisma
for a little bit more visibility.
Doug's hide is carefully positioned
to give him the best view of the valley
just in case a snow leopard should turn up.
Five days!
That's 35 hours of watching.
Nothing.
No cats.
Of course it's boring!
It's boring as hell!
After seven weeks of patiently sitting and waiting,
these distant shots are all that Doug managed to film from the hide.
But luckily, the remote camera's proved to be more successful.
Whilst even a few shots of snow leopard in the wild are thrilling,
the crew were still far from having a sequence of behaviour.
Planet Earth needed to take another risk
and move to a new location.
Unfortunately, where they hoped to search for snow leopard,
others were already searching for al-Qaeda.
REPORTER: This is THE location in the war against terror.
Only news crews were given access
until the political situation became more stable.
One year later, Planet Earth was finally allowed into Pakistan.
They faced a week-long trek through terrain
that was not only politically but geologically unstable.
Whoo!
The BBC has put us through two days of safety training.
It went from land mine clearing to hijack attempt
and having watched the markhor, which we're trying to film,
climb these cliffs that we're on today,
the most terrifying thing is these football-sized rocks
that keep flying past at head height.
You just think you actually can't prepare for that sort of thing,
getting knocked on the head by a big rock.
It's quite scary, really.
But it turned out to be worth all the risk.
The crew were in promising snow leopard terrain
and soon finding plenty of signs that they were around.
How old do you think that one is?
We just got a lot of snow and we'll be able to track the snow leopard.
So, we'll have a lot better chance of filming it.
It's just fantastic!
Good news for tracking,
but the snow would make it far harder to get around.
To increase their chances of finding a snow leopard,
the crew split up,
leaving Mark to spend Christmas on his own.
It's gonna be the first Christmas and New Year
I've spent away from my family.
I spoke to my kids last night
and they were just about to go out carol singing around the village.
It would have been nice to have been with them.
Erm... However, er...
Well, that's it, really.
Although Mark woke to a white Christmas,
there was no sign of the present that he had most been wishing for.
He had to wait five days before he heard any more news.
We just got a report that there's a snow leopard up on the ridge.
We were too low where we were before
so I'm just trying to get some height
to get a better view of it.
Hugh on the radio said it was just up the valley on the cliff
on the left here.
Finally, Mark was rewarded with his first ever glimpse.
I looked up onto the ridge.
I could see this leopard-shaped rock,
which I'd seen a million times before.
I looked through binoculars and there was a leopard just sat there.
I said, "Leopard, leopard!"
They went, "Mark..." "Look at it!"
It's perched just on top of a rock and it looked down at us
and it sort of sat down in a sphinx-like posture.
It came down very quickly and it's in a cave just up here,
about 100 metres away.
And, er, we've just gotta stake it out now and wait.
Mark's patience had paid off.
News of his success quickly reached the tracking team.
Snow leopard, snow leopard!
Hey! THEY CHEER
I can't tell you how relieved I am.
This is just the best news ever
and tomorrow's New Year's Eve so I think we're gonna party like there's no tomorrow!
No excuses, I think, on this one!
Ohhh! I just...
Unbelievable! I couldn't be happier!
The crew were lucky enough to spend two whole weeks
with this snow leopard and her cub,
capturing intimate details of their lives
in this extremely remote location.
But the final day of filming was to bring the best luck of all.
Planet Earth's three-year quest
ended with this extraordinary footage -
a wild snow leopard hunt,
something few humans have ever even seen.
Subtitles by Red Bee Media Ltd 2006
E-mail subtitling@bbc.co.uk