Earth () - full transcript

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.