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 define 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 100km in that direction.
It's 140km 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 ch*nk 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 t*rd.
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 expl*sive.
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
as*ault 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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