All language subtitles for The Great Rift (2010) - S01E02 - Water (1080p BluRay x265 Silence)_track3_[eng]

It's raining... again.

2.5 miles up in Africa's Virunga mountains

the weather is mostly miserable.

There's no point looking for shelter.

The resident gorillas' fur

is thick enough to keep them warm,
even when it's wet.

For sun lovers,

the Virungas wouldn't rate high
as a holiday destination.

But without this rain,

the gorillas wouldn't have food
in such abundance.

And there would be no grass
on the plains below.

Across Africa's vast Rift Valley,

it's where the rain falls
and how it interacts with the landscape

that determines who will prosper
and who will die.

Spanning 3,000 miles along the length
of East Africa,

the Great Rift is a complex of enormous
valleys, volcanoes and grassy plains.

The Great Rift was created

when a plume of super-hot lava
pushed up beneath Africa

over millions of years.

But once the whole area had been lifted
more than a mile high,

cracks appeared around the margins...

...creating the Eastern Rift
on one side...

...and the Western Rift on the other.

In the giant clefts of the Rift Valley,

water collects in vast lakes,

home to dazzling arrays
of colourful fish.

The Rift's rain-drenched mountains
in turn feed Africa's mightiest rivers,

whose tributaries provide a lifeline
for thirsty game in times of drought.

But not all the freshwater here
is good for life.

Ash from volcanic eruptions turns
the shallow lakes of the Eastern Rift

into caustic death traps.

At its northern end,
the Great Rift plunges into the Red Sea,

creating a dazzling world of coral

and ocean trenches hiding deep secrets.

Few places on Earth
provide such a range of aquatic habitats.

So how has wildlife adapted

to the challenges and opportunities
of the Great Rift's watery worlds?

All the water in the Rift begins as rain.

Converging trade winds
create cloud masses

which move up and down
the length of Africa,

producing two rainy seasons each year,

bringing the landscape to life.

At the end of the long wet season,
the Rift's rivers are brimful of water.

There's abundant food for the hippos
and other riverside residents.

But the good times won't last for long.

As the rains retreat northwards
and the grasslands dry and wither,

drinking water becomes
increasingly scarce

for the Great Rift's wild inhabitants.

In the savannas,
lakes and pools evaporate

until only the rivers remain.

The increasingly arid landscape
poses a problem for these African buffalo.

Because dry grass is difficult to digest,

each buffalo needs to drink
34 litres a day.

As the grazing close to the river
is used up,

they face a longer and longer daily trek

between their feeding grounds
and watering places.

Buffaloes can smell water
from a long way off

and follow established trails
through the bush

which lead to favourite drinking spots.

As the buffaloes drink,
fluttering oxpeckers get a chance

to remove ticks and other parasites
from their faces.

It's the only time they will tolerate

sharp beaks picking around
sensitive eyes and ears.

Elephants are even more dependent
on the river.

In this hot climate, an adult elephant

needs to drink a staggering
200 litres a day just to survive.

This family share their favourite
drinking spot with other elephants.

So as well as slaking their thirst,

the river provides
a focus for their social life.

River mud provides excellent protection
against the African sun.

With a belly full of water
and a coat of sunscreen,

the elephants head off
towards the blistering savanna.

While the falling water level
is bad for elephants and buffaloes,

it's just what these bee-eaters need.

They dig their nesting burrows in the
vertical banks of Rift Valley rivers,

which are only exposed in the dry season
once water levels have fallen.

Three months ago,
this entire nesting site was under water

and the birds were far away
in the jungles of the Congo.

Nesting on an exposed mud cliff
makes the bee-eaters nervous.

And with good reason.

An African fish eagle
has taken up residence on the bank-top.

But it's not here to admire the view.

Fish eagles' huge feet

are designed to grab slippery fish
from the water surface,

but they are good for other prey too.

The shrinking rivers create a serious
problem for another Rift resident.

Hippos' dependence on water is absolute -
they only feel safe

where it's deep enough
for them to submerge completely.

Hippos feed at night

and spend the day digesting their dinner
in the safety of the river.

While the grown-ups snooze...

...the youngsters play.

Young hippos are very curious.

As the river shrinks,

the hippos crowd together
in the few remaining deepwater pools.

Each stretch of river
is controlled by a dominant bull,

who tolerates other hippos in his patch

so long as they behave themselves
and defer to him.

Keeping your head down and bottom up
while spraying dung in all directions

counts as good manners in hippo society.

But jostling your neighbour
is considered very bad behaviour.

Any ruckus in such crowded conditions
spreads like a shock wave,

causing a multiple pile-up
of grumpy hippos.

It's bad news for the hippo at the end

who gets pushed into the path
of the resident bully.

Once the pecking order has been restored,
everyone can settle down.

But there's a darker side
to life in the Rift's river world.

At the peak of the dry season,

an anthrax epidemic
sweeps through the crowded colony,

killing dozens of hippos.

The smell of death
carries in the current.

Within a few hours, the hippo carcass

has attracted more than a hundred
crocodiles from far downstream.

Crocs' ultra-efficient immune system

allows these reptiles to eat diseased meat
without getting sick.

The smaller crocs hang back
while their elders guzzle and gulp...

...shadowed by a hopeful heron
on the lookout for fish.

But it's the crocs' day.

Life and death are never far apart
in the waters of the Great Rift.

But not every lake or river

is at the mercy of the seasons
and the sun.

Beneath the Great Rift's rolling hills,

porous volcanic rocks
channel water deep underground,

sometimes for many miles.

The subterranean water
eventually pops out as a spring,

like this one at Mzima
in southern Kenya,

feeding an oasis of crystal-clear
streams and lakes.

Because it's supplied from
a large underground reservoir,

a volcanic spring like Mzima
continues to flow

even at the height of the dry season...

...providing a year-round haven
for wildlife.

And the Rift's unique geology

has produced another kind
of water supply

that's equally immune from drought.

Plunging six miles deep,

Lake Tanganyika
is Africa's greatest natural reservoir.

It contains 30 trillion litres
of water...

...and stretches 400 miles
along the Western Rift Valley.

Its sister lake, Malawi,
has a similar profile.

Lake Malawi is famous for its
extraordinary diversity of cichlids.

More than a thousand unique varieties
found nowhere else on Earth.

All are believed to be descended from
just a handful of species

which have evolved a dazzling array
of shapes, colours and behaviours.

The key to this explosion of evolution

lies in the cichlids'
peculiar breeding behaviour.

Unlike most fish,
which release their eggs into open water,

cichlids take great care of their young.

Some sandy bottom species
build volcano-shaped nests

where the male courts his female,

then guards her brood

until they have grown big enough
to look after themselves.

Other baby cichlids have a truly bizarre
relationship with their mother.

When threatened,
they take shelter in her mouth.

She then carries them around,
waiting until the coast is clear

before releasing them
back into open water.

Such intensive parenting

means cichlids often stay in one spot
throughout their lives,

forming inbred communities
which turn into unique local species.

And that explains why Lake Malawi
is filled with so many different cichlids.

For little fish, the rocky lake margin
is a dangerous place.

A family group
of African spot-necked otters

sets out to hunt along the shoreline.

As night falls,
the lake's fish face a formidable enemy.

Pack-hunting nyanda fish,
1.5m long, behave like sharks,

using an electrical sense

to home in on the life signs
of smaller fish hiding among the rocks.

It's thought they can even communicate
with electrical signals,

to synchronise their feeding
in the dark.

For their prey,
there's little chance of escape.

Further from shore,

Lake Malawi plummets
into permanent darkness

beyond the reach of human divers.

Until now, no-one has seen
what lives down there.

A remote-controlled sub,
armed with camera, lights and fish bait,

provides the first glimpse
of what lies below.

Over 100m down, the fish bait
attracts deepwater cichlids...

...but their teeth can't get through
its armoured skin.

Attracted by the smell of food -
a lake crab.

In the background,
a short-bodied synodontis catfish

uses its whiskers
to investigate the bait.

Now it's the turn of bathyclarias,

a deepwater catfish,
filmed here for the first time.

At this depth,
the fish bait provides a rare treat.

The catfish is frantic to feed.

As the smell of dead fish
spreads along the lake bed,

more crabs are drawn to the scene.

Eventually the crabs close ranks,
forming a barricade of legs and claws...

...claiming the fish
exclusively for themselves.

Who would have guessed that
the Great Rift's lake depths

are ruled by scuttling crustaceans?

And what else could be down here?

Catfish and crabs are only minor players
in the Rift's freshwater economy.

But there's another resident
of Lake Malawi that plays a major role

in the fortunes of the entire region.

A few days after each new moon
during the northern winter months,

strange tornado-like clouds
condense over the lake.

The phenomenon happens
during periods of calm weather,

allowing the fragile spirals
to build hundreds of metres high.

They consist of vast numbers
of tiny midges.

There may be more midges
in a single cloud

than there are humans on Earth.

All are driven by a single purpose -
to breed.

Absorbed in their dance,
the midge clouds drift towards land.

Plants along the shore provide a resting
place after hours of constant flight.

But the vegetation harbours enemies.

Spiders live along the lake margins
in huge mixed colonies.

Some trap the midges in sticky webs.

Others use goggle eyes
to stalk their quarry,

pouncing like miniature tigers.

In spite of countless casualties
along the way,

the majority of the insects
eventually return to the lake

to fulfil their destiny.

The females lay their eggs
on the water surface.

Then they die.

The eggs sink...

...and hatch into
translucent aquatic larvae -

tiny predators which specialise
in feeding on lake plankton.

Enriched with minerals
from the surrounding volcanic rocks,

Lake Malawi's waters
support an abundance of plankton,

which is why the midges are here
in such spectacular numbers.

But the story doesn't end here.

Sardine-like usipa
are voracious predators of midges.

And these unassuming little fish

are the key to one last link
in this amazing food chain.

All around the lake,
fishermen are launching their dugouts

in anticipation of a nocturnal uprising.

Usipa fishing takes place
at the new moon,

when lamps are the only source
of light on the lake.

Divided between the two larger boats,
the net is paid out in a circle.

At the centre, the lamp-bearing boats
draw up the fish to the surface

like moths to a flame.

With the bottom rope pulled tight,
the trap is sealed.

Each haul may yield
just a few kilos of sardines,

but the fishermen will land
over a dozen catches before dawn.

On an island close
to the fishing grounds,

the fishermen grab some breakfast
before heading for home.

At 2m long, the Nile monitor
is Africa's largest lizard -

an ambush predator armed with
raking claws and powerful jaws.

But why bother to hunt
when there's free food on offer?

As the fishing boats near the shore,
a crowd gathers to meet them.

In Malawi's hot climate, it's hard
to get fresh fish to distant markets,

so most is spread out to dry in the sun.

Like this, they will keep for weeks
or even months.

Astonishingly, these tiny usipa
provide essential protein

for around 20 million people
in countries bordering the lake...

...and all this vast bounty
originates from tiny fluttering midges.

From Lake Malawi, the Shire River
flows into the mighty Zambezi,

which marks the southern limit
of the African Rift system.

Upstream, the Zambezi

slices through the volcanic rocks
of the Tonga Plateau

to crash down into
the narrow Batoka Gorge.

More than a mile wide,

with up to 10,000 tonnes of water
pouring over its lip every second,

this is the world's largest waterfall.

Its local name, Mosi-oa-Tunya,

translates as the "Smoke That Thunders".

In 1855, David Livingstone
renamed them Victoria Falls

in honour of his queen.

A thousand miles to the north-east,
the Rift has another quite distinct arm.

Here lie lakes very different

from the vast inland seas
of the Western Rift,

lakes that are hostile to life.

This is Lake Natron
in northern Tanzania,

sometimes known
as the Lake of Death.

Countless centuries of evaporation

have concentrated volcanic minerals
in its strangely coloured waters

to the point where they are so caustic
they can dissolve human skin.

However, there is one animal

that seems immune to this
cocktail of corrosive chemicals.

Each year, huge flocks of flamingos
converge on Lake Natron.

In the shallows,

the birds demonstrate
their unique feeding technique,

pumping water through
hair-fringed channels in their beak

to extract micro-organisms
called cyanobacteria

which flourish in the lake's
peculiar mineral cocktail.

The cyanobacteria contain a pigment
which colours the birds' feathers.

Adult flamingos only choose mates
with colourful plumage,

so the survival of their species

is linked to the peculiar chemistry
of the Rift's volcanic lakes.

The flamingos are able to
wade around in the caustic waters

because their legs are protected
by resistant scales.

In neighbouring Lake Magadi,
life faces an even tougher challenge.

Fed by volcanic springs,

Magadi's waters are not only caustic

but in places they're hot enough
to poach an egg.

Amazingly, there's a creature
that's able to survive

completely submerged
in this deadly brew.

It's a little fish
known as the alkaline tilapia.

And it's made its home
in the most extreme environment

in which fish life
has ever been recorded.

The algae on which the tilapia feed
grow best in the volcanic springs.

So each little fish
faces an agonising choice -

it can stay safe but hungry

or it can risk life and fin
in a dangerous game of chicken,

dashing into the hot spring,
snatching a mouthful of algae,

then dashing back into cooler water
before it cooks.

Most of the fish are content
to hang around the margins of the spring

but there's always one adventurous
or extra-hungry individual

prepared to go for the jackpot.

There's no question of the rewards,
but it's a hugely risky game.

140 miles further north
along the Great Rift,

Lake Bogoria is even more
volcanically active.

Its shores are fringed
by steam vents and gushing geysers.

As with Lake Natron,
volcanic minerals enrich Bogoria's waters,

providing an ideal environment
for even larger flocks of flamingos.

At the height of the season,
there may be over a million birds.

Flamingos are famous for their
extraordinary courtship rituals.

Flamingo migration

is one of the Great Rift's
most enduring mysteries.

They appear and disappear unpredictably
in response to fluctuating water levels.

Continuing northwards up the Great Rift,

a series of lakes
stretch up through Ethiopia

to Lake Assal,
the saltiest water body on Earth.

Lake Assal lies 153m below sea level,

making this the Rift's, and Africa's,
lowest point.

The lake's waters
are fed by seawater springs

which evaporate in the blistering heat
to leave huge salt pans.

Beneath its glistening crust,
the lake plunges over half a mile deep.

But it's not filled with water. It's
solid salt all the way to the bottom...

...the result of hundreds of
thousands of years of evaporation.

Immediately north of Lake Assal
is the Mandab Strait,

known to Arabs as the Gate of Tears.

It separates Africa from Arabia

and marks the junction
of the Indian Ocean and the Red Sea.

Here at Ghoubbet el Kharab,
barren lava flows

mark the point at which
the Great Rift finally meets the sea

and enters another world.

Offshore, the sea floor drops away
in spectacular underwater cliffs -

a submarine equivalent
of the Great Rift Valley.

Strong currents make these walls
ideal for filter-feeding corals

which provide a home
for more than a thousand species of fish,

including over a hundred
found nowhere else.

In the surface waters,

a school of Indian mackerel
trawl open-mouthed

through the rich plankton.

There are places off the Djibouti coast

where the Great Rift
plunges to unknown depths.

Exploring down here
takes specialised equipment.

This is the first time

light has shone in this corner
of the Great Rift's ocean depths.

Some of the creatures down here
may be completely unknown to science.

From the dark depths of the trench,

nutrient-rich currents
well up towards the surface...

...creating a plankton bloom
that attracts ocean giants.

Whale sharks
are the largest fish on Earth,

growing over 15m long.

Trawling the oceans with mouths agape,

their sieve-like gills sift out
the plankton and small fish

on which they feed.

Djibouti is famous for this
annual gathering of whale sharks

which migrate here each winter
from far across the Indian Ocean

to take advantage of
the Great Rift's fertile waters.

This extraordinary event
owes its existence

to volcanic forces
deep beneath the Red Sea floor.

Those forces are tearing
Africa and Arabia apart.

As the Great Rift lengthens and widens,

the Red Sea will eventually
join up with the Mediterranean,

making Africa
the world's largest island.

Meanwhile, the East African Rift
continues to spread ever wider,

gradually filling with lava and ash
from the surrounding volcanoes.

And where seasonal rains
refresh the landscape,

the Great Rift's lakes and rivers

will continue to sustain
an abundance of wildlife.

For this episode,
the crew discovered

how harsh the Great Rift can be.

They call this place
"hell on Earth",

so I guess that's why they send
the French Foreign Legion here to train.

It's a pretty nasty place.

Cameraman Gavin Newman
and director Ingrid Kvale

found themselves in one of
the Rift's hot spots.

Ow!

Seems to be the windiest place in Africa

and I'm having to hold on
to the tripod for dear life.

So on this side I'm in Africa,

and if I just hop across here,
I'm now in Asia.

No, I'm not. I'm the other way round.
Hang on.

Damn!

There's one here. Here, here, here.
Right beside us.

The team came here to film
what lives in the Great Rift,

where it plunges beneath the sea.

Gavin has brought his own specialist kit

out here to Djibouti
in the southern Red Sea.

Fingers crossed
everything does what it says on the tin.

Gavin has spent the last five years

perfecting a remotely operated
camera system, or ROV,

to film underwater
much deeper than divers can.

This is its maiden voyage

and everyone is understandably nervous.

You don't want to make a mistake
cos you'll pay for it later on.

I'm a bit of a toy freak at heart.

Lots and lots of wires, unfortunately.

Vincente, the boat's dive master,
can't wait to put it in the water.

I think we're going to see landscapes,
OK, seascapes,

that nobody has seen before.

Captain Amin is intrigued by the machine
Gavin has named Nemo.

How deep you can go with this?

This can go to about 300m.

Whoa.
- Yeah.

300m!
- A lot deeper than me.

Gavin finally fits the ROV
with its video camera.

The rest of it's a bit of a taxi
for this camera system.

All you have to do now
is throw it in the water.

Tomorrow is Nemo's big day

and the culmination
of Gavin's labour of love.

At first light, Gavin and the crew
head out to the Ghoubbet el Kharab

or Devil's Cauldron.

Here, the Great Rift plunges
deep below sea level.

We're at the edge
of the wall right now.

OK. So here it's a good place.

Jacques Cousteau is said to have
come here in search of sea monsters.

It's a place full of legends -

legends about spirits
living in the small cracks

that they have in the rocks.

When Cousteau came here,
they put a cage with a camel inside.

They put it down and when they took it
out, the cage was completely crushed,

no camel inside.

Did Cousteau say what happened
to the camel?

No explanation.

So you think this is a good place
to dive, then?

We have to try it.

It's time for Nemo to get wet.

Are you pleased
with that launch, Gavin?

It was a little bit chaotic but let's just
get in and see how it's floating.

- It's my baby.
- Oh, it's your baby.

It's looking good.

Nemo's ready to start exploring
the depths of the crack.

Go, go, go.

- Wow.
- OK. See where we are.

So far, so good.

It's finally under water
and it's finally filming images.

The beauty of what we're doing

is that we have no idea
what we're going to find anyway.

It could be we find a huge rift crack

with all sorts of interesting marine life

that nobody had any idea
was down there.

But Gavin senses
things aren't quite right.

OK. I think they're pulling me
on the cable.

Can you check what
they're doing with the cable?

They should still be feeding cable.

Yeah,
they are feeding you cable.

In that case, we've got a problem
and we're stuck.

At the moment,
we might have the cable

around some rocks on the bottom,
but I'm not entirely sure.

Gavin's suspicions are confirmed.

The cable is entangled
around some rocks.

Dropping the ROV isn't as straightforward
as we thought it'd be.

There's lots of gnarly bits
of volcanic formation

that could damage
or even destroy the ROV.

Gavin, what do you think?

Yeah, I'm just a little bit busy
right now.

Vincente dives in immediately
to sort the problem.

- Bring it up. Yeah, please.
- OK, hey!

Feed cable out.
Cable out, yes, into the water.

Stop. Stop.

This is not a place to be trifled with.

There we go. Whoa. That's better.

OK. We're now looking at
the very mouth of the crack here.

There's an amazing amount
of marine life down here.

It's very diverse as well.

There's soft corals and hard corals...

...and a lot of fish.

There's three cuttlefish here.

I think we've got
a discarded boat's anchor

that they've obviously lost in the crack.

A nice bunch of butterfly fish
hiding around it.

Maybe it's Cousteau's anchor -
who knows?

There's several sharks around.

- He was going towards the Rift.
- Towards the Rift. OK.

- So if you see something big...
- We know what it is.

Whale sharks have come here to feed
on the plankton at shallow depths.

This is not a job for Nemo.

Gavin can't miss out on a chance
to film the world's biggest fish

and puts the ROV filming on hold.

It's coming towards you.
It's there.

Up there, up there, up there, up there!

Not one, not two - three, four.

Whoo! Oh, there's one
here, here, here, right beside us.

- Go!
- I'm trying!

What's happening?
- It's quite big.

We've got a bunch of about
five whale sharks right ahead of us.

I think I got five in one shot
and you just kept turning around

and there was another one
right behind you.

There is two swimming side by side.

Maybe this is a mating ritual.

After successfully filming whale sharks,
Gavin's back with Nemo.

He's determined to take the ROV
deeper than anyone has been before.

Putting ROVs down holes
is never considered to be a great move,

but obviously you have to take risks
to get the sort of images that we want.

Just got to be careful
I don't get stuck here.

Aah!

Didn't really want it to end up
being Nemo's tomb.

Could this worry
be giving you grey hair?

Yes. I think it's ageing me
prematurely, definitely.

You can see the rift carries on
down there, way below us.

Ah! You've gone quite far
if you're down in the middle.

Yep.

Just got to hope
that I can manoeuvre myself out.

Ooh, there's a nice little moray eel
on the wall. It's beautiful.

If I turn the lights off altogether,
you'll see it's totally dark down here.

He wondered what happened
to the light.

We're now heading down
deep in the crack here.

It's like a sort of chasm
to the bottom of the world.

So I'll pretty much guarantee you,

80.3m is the deepest dive anyone
or anything has done in the Ghoubbet.

It's a very strange environment
down here

because most of the creatures
that we're looking at

probably never see light.

Never really seen anything
like this before.

Looks like lots of skeletal coral.

Quite pretty. Do you know what that is?

- This?
- Yes.

No.

Nemo's ROV technology
has finally revealed

the strange yet beautiful
underwater realm

that no human eyes
have ever seen before.