All language subtitles for Earth s01e02.eng

Just look at that.

It's awesome, isn't it?
If not a little terrifying.

A massive tsunami of ice,
cascading down the valley.

Try to imagine that, though,
not just happening here,

but happening all over the world.

Well, 700 million years ago...

..that's exactly what did happen.

Ferocious forces...

..created a climate emergency.

And from pole to pole, across
all of the lands and oceans...

..our world...

..froze.

The story of this extraordinary time
is written in the rocks,

and as the latest evidence helps us
piece together what happened...

..we know this disaster
hit at the worst possible time.

Just as the earliest forms of animal
life were evolving, the ice

threatened to destroy them, and
the world as we know it, forever.

The thing is, this moment
in our planet's history is also

a story of resilience,
because this climatic

and environmental catastrophe lead
to something miraculous.

You see, this new life on Earth
didn't just survive the ice

and its aftermath, it thrived.

The deep freeze saw a new age
on Earth,

an age of complex life,

of a greater size
and diversity than ever seen before.

Life that would go on to
dominate the oceans

and the land to this very day.

Our story begins in Earth's ancient
past...

..850 million years ago...

..when the face of our planet
was unrecognisable.

Almost all the land that existed
was gathered into one,

giant continent, called Rodinia.

Thousands of kilometres,
coast to coast,

this rocky landmass
dominates the planet.

For all its scale,
from its jagged peaks...

..across its desolate plains...

..there are no plants

and no animals.

But there is life here.

In shallow, coastal waters...

..bacteria clump together

into living mats that
cover the seafloor.

For nearly three billion years, this
has been the limit of life on Earth.

A planet that couldn't be more
different from the world we live in.

Even in Iceland, with its harsh
winters, so hostile to life...

..once the warmth returns,
so do a host of plants and animals.

It's honestly hard to imagine
that up until very recently,

this was a dark, desolate and frigid
place, because now look at it.

It's bright, it's busy, it's warm,
it's busy with life doing

what it needs to do at this time
of year, which is flower and fruit.

And look at this lovely,
delicate little harebell here.

And these are the fruits
of the crowberry.

And they're meant to be edible.

Best left for the birds.

But aside from the taste, look at
that, it's a perfect little package.

It's exquisite. But what interests
me more, what's more incredible,

more important, is how this fits
into the grander scheme of things.

All the life here has
evolved in partnership

with everything around it.

Each individual is just one
strand in an intricate web of life.

Every part connected to, and reliant
upon, all the others to survive.

Large, complex life in the
modern world can only really make it

if it's part of a bigger,
interconnected ecosystem, like

this one here, an ecosystem which is
as complex as the life it supports.

But the staggering thing is,
the truly staggering thing is,

that until recently,
none of this existed.

You see,
for over four billion years,

that's pretty much our entire
planet's existence, large,

intricate life like this
was nowhere to be found.

All the animal life that now
exists in the world can

trace its origin back to what
was happening off the shores

of Rodinia, 850 million years ago.

In the coastal waters,
amongst the bacteria,

something new has appeared.

Giant cells tower over
the living mats.

These strange microbes are the
distant ancestors of animal life.

They're not bacteria,
but eukaryotes - bigger,

more complicated...

..the first cells with a nucleus.

The bacterial mats here get their
energy from sunlight, but like

you and me, they eukaryotes rely
on food from their surroundings.

And in this basic ecosystem,
there were slim pickings,

bacteria floating in the water,

and the slow flow of minerals
from the eroding land.

Enough to survive,

but far from
what they need to thrive.

These new life forms seem destined
to live out a meagre existence

stuck on the sidelines...

..never able to evolve into the
vibrant ecosystems of today.

But the planet was about to deliver
a colossal shock to the system...

..thanks to powerful forces
that are still at work today...

..and can be witnessed in places
like Thingvellir,

on the western coast of Iceland.

Walking through here,
I get a real sense of raw, primal,

brutal forces at play, and those
forces certainly are at play.

You see, every year,

the walls of this chasm move
apart by one centimetre.

Now, I know it doesn't
sound like much, but that's

because we've got to start thinking
about this in geological time,

so that's hundreds of millions
of years, not hundreds of years.

The rock beneath my feet is quite
literally splitting in two,

along a fracture which
runs for thousands of kilometres.

Iceland sits on a boundary
between two giant

chunks of the Earth's crust,

known as tectonic plates.

Heat churning within the
mantle of our planet

is driving these plates apart.

As they spread...

..the land above stretches

and then tears...

..creating great rifts
through the landscape.

These forces have been moving
the world's greatest landmasses,

creating and destroying them, for
more than three billion years, and

nothing can resist them, not even
a giant supercontinent like Rodinia.

Deep beneath Rodinia...

..swirling currents of heat cause
tectonic plates to shift.

They begin to move apart...

..and great chasms gape
open across the landscape.

This great continent is ripping
itself apart.

Earth is the only planet
in the solar system to have active

tectonic plates.

And they're constantly
reshaping our world and its life.

In many ways, we can
think of the history of our Earth

as about the interplay
between life and geology,

and sometimes, the great planetary
process have given life

a bit of a leg up.

On others, they've knocked it right
back down again.

One of these moments
was about to play out,

and what happened next would
ultimately defy the entire

living world that we
experience today.

As the rifting continues
for millions of years...

..it creates deep valleys...

..powerful rivers...

..and hundreds of kilometres
of new coastline...

..all greatly increasing erosion,

and causing a flood of minerals to
pour from the land into the oceans.

Thanks to this boost in minerals,
the eukaryote population explodes.

They build numerous colonies,

a crucial step towards forming
multi-celled animals.

And some organisms now
have enough energy

to produce protective spikes...

..built from all those
minerals washed off the land...

..and vital defences,

as there were now predators taking
advantage of the boom in numbers...

..in this newly energised ecosystem.

We've witnessed this dramatic change
with our own eyes,

thank to recent discoveries made

in 700 million year-old rocks
from the Grand Canyon.

Scientists have discovered these...

..tiny micro-fossils of marine life,
each smaller than a grain of sand.

What shocked them were the holes
in the outer shell,

most likely created when they
were attacked and eaten.

Now, the predators
weren't preserved,

but the best guess is that they
were something like...

..this...

..a single celled amoeba called
Vampyrella.

This predator punches holes
in its victims

before sucking
out their inners...

..leaving behind holes
near identical

to those found on the
micro-fossils.

This is the earliest evidence
of predators and prey ever found.

That element of everyday life,
so key to our modern world.

The vast tectonic processes at work
provided complex life with

the spark that it needed,

an environmental revolution
which allowed it to move towards

the interconnected ecosystems
that we see around us today.

But just as life was taking
this great leap forwards,

disaster struck.

The forces tearing the ancient
supercontinent apart were about

to plunge the entire world into a
seemingly endless, desolate winter.

On Rodinia, events take
a catastrophic turn for the worse.

Superheated magma bursts
through the surface,

as rifting thins
the crust in multiple places.

Molten rock swamps two million
square kilometres

of the continent...

..one of the largest
outpourings in Earth's history.

The lava cools
and forms the dark rock basalt...

..creating a vast black stain
across the heart of the continent.

You see, the great freeze begins
not with ice...

..but with fire.

Fresh basalt is quite
incredible stuff.

This is about ten months old.

Now, it's not terribly easy to walk
over, and you certainly

wouldn't want to stumble.

It's extremely jagged,
ripping your boots to pieces,

and you wouldn't
want to fall on that, would you?

But what's really incredible
about this rock is that it has

the capacity to
change our planet's atmosphere.

As rain forms, it absorbs carbon
dioxide gas from that atmosphere.

When that rain flows over basalt,
there's a chemical reaction

that draws carbon dioxide
out of the water

and binds it to the surface
of the rock, locking it away.

We know that carbon dioxide is
a very potent greenhouse gas,

has the capacity to lock
lots of heat into our atmosphere,

and the more of it that we
pump into the air,

the more we see our global
temperatures rising.

But then, I don't need to tell
you about global warming.

What's interesting is that
the reverse is also true.

If we take carbon dioxide out of the
atmosphere, temperatures fall.

The erosion of millions upon
millions of tons of basalt,

spewed up when Rodinia broke apart,
sucked that warming

blanket of carbon dioxide
out of the atmosphere.

And it flicked the
Earth's thermostat

from a comfortable stasis to chill.

Falling levels of carbon dioxide...

..pushed down temperatures...

..awakening a sinister force.

Ice...

..something not seen here on the
planet for a billion years.

For now, it's limited to the poles.

But it's spreading.

Whether you're a microscopic
or more human-sized,

most life loves the warmth...

..especially here in Iceland, where
the winters are so harsh.

Summers here are truly amazing -
look how verdant, how green,

how lush it is.

And there's also a tremendous
diversity of plants -

flowers, mosses, dwarf trees.

And, of course, on a day like today,
blue sky, sunshine - it's lovely.

But the lingering cold of winter
is never too far away.

Venture up into that
lingering cold...

..and it's possible to see how life
suffers as temperatures fall.

I've only travelled about a mile,
but I've climbed in altitude,

and the difference in the landscape
is really rather stark.

Look at it.

It's principally barren rock

and the plants here are scattered
few and far between.

You see, up here,
the temperature only

gets above five degrees Centigrade
for a few weeks of the year,

and when the temperature
drops below that,

plants can't produce
structural tissues.

You can give them all the water,
all the nutrients they want,

but at lower temperatures, they just
can't build their own bodies.

Across the world, whenever
temperatures drop low enough,

for long enough,

plants and life slowly fade away.

Temperature is the natural limiter
for complex life in our world,

and those rich,
interconnected ecosystems,

which can thrive down there
can't even survive up here.

When it gets cold,
the web of life unravels.

On the ancient Earth,
as temperatures continue to fall,

the cold advances on early
life from all sides.

Armadas of sea ice march out from
the North and South Poles...

..as on land, immense glaciers surge
forth from the mountains.

The places life can
hold on are rapidly shrinking.

The ancient Earth teeters on the
edge of a climate catastrophe,

as the ice tightens its grip.

Today, ice covers a tenth of
all the land on the planet.

Vast sheets blanket the poles...

..and the high mountains of
all of the continents.

Nearly 10% of Iceland is
covered by a single sheet of ice.

The icecap here is vast.

It stretches for 100 kilometres in
that direction.

It's 140 kilometres wide and nearly
a kilometre thick in some places.

But in the modern world, ice
is limited.

It comes to a grinding
stop down there.

And that's not just because of
human-induced climate change.

The world is simply too warm.

The idea that ice could
smother the whole world

seems incomprehensible.

But just over 710 million years ago,

the Earth was a much more
vulnerable place,

and when the ice started marching,
there was very little to stop it.

We now know just how far it reached.

Look under the leading
edge of this icecap

and you can see the evidence
of its raw power in the countless

chunks of rock ripped up
and dumped by the ice.

Glaciers are so destructive,
they leave scars in the rock record.

Like these stones and boulders,

a completely different type or
rock to the layers around them.

Called drop stones, the flowing ice
picked them up and dropped them

hundreds of kilometres
from where they originated.

Scientists have found these in rock
layers that were sat over

the equator 700 million years ago...

..hinting at an event
of an astonishing scale and reach.

The ice is winning.

A band of warmth still holds
out around the equator...

..the last refuge for life.

But as the white expanse spreads,

more and more heat is
reflected back into space...

..and the
freeze becomes a runaway process.

Ice surges over almost
all of the remaining oceans.

Even at the equator,
hope slowly fades.

And finally,
this last stretch succumbs...

..leaving the planet a frozen,
white marble...

..floating in the darkness of space.

Ice had claimed the world...

..in an event known
as Snowball Earth.

It's almost impossible to imagine,

but pretty much all of the planet
was just like this.

The whole world was plunged into
a deep Ice Age, wrapped in sheets

of ice sometimes kilometres thick,
choking our land and our oceans.

It was a global winter
with no end in sight.

Modelling suggests that it was

minus 70 degrees Centigrade
at the poles...

..that it never got above
freezing anywhere on the planet.

It would have been pretty sterile.

It would have stressed or stalled
the water cycle.

There would have been little
or no evaporation...

..hence no rain,

no snow,

very few clouds.

If there were clouds, some would
have been clouds of carbon dioxide.

This was an incredibly
hostile place.

It couldn't have been more different
than the beautiful, vibrant,

dynamic planet that we have today.

The triumph of the ice
is a disaster for life.

The ocean is almost entirely
cut off from the atmosphere.

It's dark, cold.

And the flow of minerals
from the land slows to a trickle.

The food web begins to fall apart.

And the predecessors
of animal life...

..falter.

A mass dying is under way.

This was no short cold snap
life could easily ride out.

OK, the ice would have waxed
and waned a little,

with the changing of the seasons,
but the cold persisted,

unending,
for millions upon millions of years,

with no hope of release.

I know it looks like a massive,
muddy field,

but I'm actually walking on top
of a glacier, albeit a dirty one.

And out here, in the biting
face of the cold, it's easy to

imagine that the endless winter put
pay to complex life on Earth.

But of course, it didn't.
Live survived.

You and I are living,
breathing proof of that.

But when it comes to looking
for the clues that might tell us

how it pulled off its great
survival trick, these wild,

frozen places are a top
place to look.

You see, even on the exposed
top of the glacier, it's possible

to find chinks in the ice's armour,

just big enough for life to exploit.

Here we are. This is what
we're looking for.

This, we think,

is very similar to what might
have formed way back then.

Some dust blew out onto the glacier,
was warmed up by the sun,

it melted the surface of the
ice and formed this puddle.

They're called cryoconites, and it's
this simple combination of dust

and water which proved
to be life's saviour.

Now, I know it doesn't look
like much, but this is, in fact,

a beautiful little oasis out
here on top of this vast glacier.

Yes, in this one small
pool of water, there's abundant

minerals from the dust, and plenty
of exposure to the air and sunlight.

As astonishing as it sounds,

that means it's possible
to find life

in muddy puddles like this.

The simplest would be single celled
algae and bacteria,

but there are others.

These are images that have
come from an actual cryoconite.

You've got things
like this rotifer here,

and here, our favourite little water
bear, the tardigrade.

And they would be feeding on those
smaller organisms.

And, all together,
a soup here of different animals

and plants in a simple food web.

Now, I've got to tell you, I've
seen life in some pretty amazing

places in my time, but the idea
that there could be a functional

ecosystem living in a puddle,
on top of Europe's largest glacier?

Well, that is quite extraordinary.

It's thought that during Snowball
Earth, there would have been

enough patches of exposed rock
and land to generate dust.

Not as much dirt as this, but enough
to create many similar puddles.

And, what's more, scientists have
exposed these tiny oases

in the laboratory to conditions
found on Snowball Earth...

..and the life inside survived.

For no less than 50 million years,
50 million years, that's

a long time, life clung on in such
places throughout the deep freeze.

Let's be clear,
this was a tough place to exist,

but if life wanted to do more
than survive, if it wanted to

flourish, then the Earth would
have to escape its icy prison.

There was no easy route out.

The ice prevented almost
any change on the planet...

..with one exception.

Even an endless winter can't stop
the planet creating volcanoes.

Each eruption punching through
the planet's frozen shell.

Ever since our planet first formed,

the heat in its mantle
has fuelled volcanoes.

Today, there are over 1,000 active
across the world.

And there would have been at least
as many during Snowball Earth.

But even the ferocious heat of
all that molten rock was too

fleeting to break
the grip of the global Ice Age.

What did offer a slim
chance of escape was something else.

Something invisible that
came with each eruption.

As each eruption tore
through the ice,

it released a great slug
of volcanic gases,

including the carbon
dioxide stripped from the atmosphere

all those years ago.

With the land and ocean covered
in ice, there's nothing to stop

the slow build up of this
powerful greenhouse gas.

And it begins to finally bring some
warmth to the frozen planet.

The world stood on a knife edge.

If enough carbon dioxide
could build up, there was

a chance of breaking the freeze.

What would finally decide
the planet's fate is a process

we're all too familiar with today.

This glacier has been
melting for the last 130 years,

and the evidence of that melt
is all around us.

Look at this vast,
glacial lagoon here, full of bergs

and brash ice, and there's meltwater
draining out into the sea.

This is global warming.

And the key thing is that this

process has accelerated
in the last 30 years.

You see, just as freezing is a
runaway process, so too is melting.

Rising temperatures drive more water
vapour into the atmosphere.

It has a powerful
greenhouse effect.

And, as ice melts,

the exposed dark surfaces absorb
yet more warmth from the sun.

Changes like these
feed into each other

and create tipping points, beyond
which warming becomes explosive.

To limit climate change today,

we must avoid reaching
these tipping points.

But for Snowball Earth,
they couldn't have come soon enough.

What started as a trickle...

..has become a torrent.

As the ice starts to melt,
the exposed dark surfaces

suck in ever more warmth
from the sun.

The melt becomes unstoppable.

A runaway train that releases
a staggering deluge of water.

Sea levels rise two metres
every decade,

swallowing great
chunks of coastline.

After a total of over 50 million
gruelling years in deep freeze...

..the world is finally reborn.

Snowball Earth was an unprecedented
assault on our planet.

An astonishing moment that left no
corner of the world unscathed.

You and I are here because,
through it all, life survived.

But as tenacious as it was,
that life was still single-celled

and still trapped
in the microscopic world.

But this is more than just
a tale of simple survival.

In the shattered remains
of the great freeze, the stage was

set for a revolution that would
change beyond all recognition.

It's easy to assume that life
progresses in a straight line,

steadily becoming more complex,
more advanced.

But in reality, it's often not like
that. Often it relies upon a great

shock to the system, a state change,
to flip life onto another path.

After which, that life
and the world in which it lives,

are never the same again.

Snowball Earth was
just such a moment.

The ice of the great freeze

had shredded the surface
of our planet...

..ripping up millions upon
millions of tons of rock

and dumping it into the oceans.

This sudden flood of resources
causes single-celled algae

and bacteria to flourish throughout
the waters of the world.

Their vivid blooms so large they're
visible from space...

..stretching across entire oceans.

Growth on such a staggering scale
has the power to change

the entire ecosystem.

All this photosynthesising
greatly increases

levels of oxygen in the water,

an element vital for complex life.

When the algae and bacteria
eventually die, billions upon

billions drift down to the bottom,

a rain of organic matter...

..adding to millions of years
worth of dead things that have built

up over the history of the oceans.

And bacteria living at the
bottom of the ocean gorged

themselves on this dead matter...

..reprocessing it and releasing
a steady stream of minerals

back into the water column...

..giving our ancient ancestors
a plentiful, sustained source

of food, oxygen and nutrients,

all supplied by life itself.

At this moment, for the first
time ever, life and the planet

come together to become
complimentary cogs spinning in

a great nutrient recycling machine,
which is providing life with

exactly what it wants in quantities
that it's never had before.

And as a consequence,
life explodes.

And after around half a billion
years of struggle,

Earth's fledgling spring is
set to become a glorious summer.

In shallow coastal waters
across the planet, life blossoms.

These may look like plants,
but they are the first animals.

Leaf-shaped Charnia
feed on passing nutrients...

..whilst Attenborites float
freely on the tides.

They're the descendants of those
first tiny eukaryote pioneers,

now evolved into myriad
strange forms,

all of which have finally broken
free of the microscopic world.

These are creatures of a complexity
and size that we could see,

could reach out and touch.

All living with,
and supported by, an ecosystem

just as intricate and remarkable
as any on Earth today.

These first truly complex
living creatures

are now long gone.

But they were the first to take
this great leap,

and once they had, for life,
there was no looking back.

All thanks to Snowball Earth
lighting the fuse.

Snowball Earth was
an astonishing period,

when life, land and the climate
were in conflict like never before.

When that long winter ended,

the stage was set for evolution
to run riot.

And finally, it's created
all of the fantastic scale, the

remarkable diversity and the amazing
beauty of life on Earth today.

How do scientists study the bizarre
animal life of the Ediacaran,

which lived more
than 500 million years ago?

So, this is a wonderful fossil from
Charnwood Forest in Leicestershire

in the UK, and it was found by
schoolchildren in the '50s.

While it looks
superficially like a plant,

because it lived in very deep water,
we know it can't have lived

off the light, been photosynthetic.
Instead, it fed from the little

bacteria and the dissolved organic
carbon that were floating past it.

These creatures are so unusual,

understanding how they interact
with each other can be difficult.

Now, thanks to advanced laser
technology,

scientists can learn more about them
than ever before.

So, by laser scanning these fossils,
we've got

a three-dimensional surface,
and what this means is, you have

essentially a snap-shot of Ediacaran
life captured on the rock surfaces.

To date, we have over 20,000 fossils
that we've laser scanned,

and using different
sorts of statistics

and mathematical approaches,
we can then work out what

they were doing and how they were
interacting with each other.

And analysing spatial patterns
within the scans has revealed

why some of these creatures
grew so big.

For a long time, we thought that
the reason they got large

and grew things like stems was to
get food without having to compete,

and what we found is that, actually,
competition's very, very rare.

Being big wasn't
an advantage for getting food,

but what it was
an advantage for was ensuring

that your offspring got to go as far
as possible, because the taller

you are, the further your offspring
will travel in the water column.

And the scans have also led to the
discovery that some organisms

had unexpected behaviours.

We actually found something rather
surprising. They don't always

reproduce sexually. Instead,
some of them reproduce little clones

of themselves that are attached
by filaments or runners, a bit like

strawberry plants or spider plants,
and so the fossils you see are

actually clones of their parents,
and even grandparents sometimes.

After Snowball Earth,
the evolution of complex life

occurred at a rate
never seen before.

We've gone from these tiny,
microscopic, little fossils,

that we can only see with
microscopes, all the way to these

large, complex organisms which show
signs of having animal features.

There's always a possibility that
without Snowball Earth,

life wouldn't have
evolved into the complex,

large organisms that we
see around us today.

Next time...

The story of how the Earth
turned green,

as plants rose from the oceans...

..to conquer a hostile land...

..but whose domination almost
wiped out all life on the planet.

If the Earth could talk,
what would it tell us?

Well, the Open University imagined
how it might answer

some of our questions. To experience
this interactive presentation, go to

the website on the screen and follow
the links to the Open University.

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