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We are entranced by the beauty of our planet.
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Just take in this view for a moment.
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00:00:34,480 --> 00:00:39,560
Lush green meadows, thick forest,
jagged mountain peaks -
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00:00:39,560 --> 00:00:41,280
it's magnificent.
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00:00:46,200 --> 00:00:48,640
But whilst we appreciate that beauty,
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I think sometimes we forget that all
of this is so fleeting.
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For the last four-and-a-half billion years,
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our Earth has been a constantly
changing ball of rock,
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transforming itself over and over again.
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00:01:05,800 --> 00:01:09,440
It's more fragile than we like to acknowledge.
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00:01:09,440 --> 00:01:12,880
It's more indifferent to us than we
care to admit.
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00:01:16,200 --> 00:01:20,120
Now, thanks to pioneering new science,
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00:01:20,120 --> 00:01:25,640
we can explore our planet's
four-and-a-half-billion-year story
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00:01:25,640 --> 00:01:27,120
like never before.
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00:01:30,200 --> 00:01:34,800
In this series, we'll witness five
pivotal moments
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in Earth's history...
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..moments of drama...
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00:01:43,080 --> 00:01:44,600
..of crisis...
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00:01:45,920 --> 00:01:48,200
..and of rebirth...
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00:01:51,920 --> 00:01:55,760
..events that shaped the planet we
live on.
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00:01:58,400 --> 00:02:03,280
Wherever you are, you have beneath
your feet the most precious object
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in the universe -
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a living, breathing, life-sustaining world.
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And this is its story.
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00:02:48,440 --> 00:02:54,200
It can feel as if our living world was
somehow inevitable...
26
00:03:00,480 --> 00:03:04,120
..that ours is a planet with all the
right ingredients
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00:03:04,120 --> 00:03:06,680
for a rich assortment of life...
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..not only to arise, but to flourish
and endure.
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00:03:15,000 --> 00:03:20,360
But, in fact, it's death that is the
only true inevitability.
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00:03:21,640 --> 00:03:25,680
There's an uncomfortable truth about
life on Earth.
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You see, this great diversity, this
weird, wonderful
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and beautiful mix of species, of
plants, animals and fungi
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00:03:33,600 --> 00:03:38,480
are all only here because something
else has died -
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00:03:38,480 --> 00:03:43,640
in fact, because an enormous number of
other things have died.
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00:03:43,640 --> 00:03:47,880
If we were to take the sum total of
every living thing
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00:03:47,880 --> 00:03:53,120
on our planet today, it would add up
to less than 1% of those
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that have ever existed on Earth.
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00:03:56,200 --> 00:04:01,080
But this colossal loss of life is not
a tragedy.
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00:04:01,080 --> 00:04:04,440
Extinction is a vital part of
evolution.
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00:04:07,760 --> 00:04:10,160
If nothing ever went extinct,
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00:04:10,160 --> 00:04:13,520
there would be no room for new species
to evolve.
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00:04:14,880 --> 00:04:19,960
Over time, extinction helped create
our rich living world.
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00:04:21,400 --> 00:04:24,240
But our planet walks a tightrope.
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00:04:26,040 --> 00:04:28,760
If extinction goes unchecked,
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the complex web of life crumbles.
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Imagine 90% of species suddenly dying
-
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not just a few endangered plants or
animals becoming extinct,
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00:04:46,600 --> 00:04:49,200
or a handful of ecosystems
disappearing,
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00:04:49,200 --> 00:04:54,520
but nine out of ten living things
wiped off the face of the Earth.
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00:04:59,080 --> 00:05:03,800
Imagine what that Earth would look
like in the aftermath -
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00:05:03,800 --> 00:05:08,320
shattered, broken, bereft of the
beautiful complexity
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00:05:08,320 --> 00:05:10,280
that we take for granted today.
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00:05:13,640 --> 00:05:19,080
We may think modern climate change is
our planet's darkest hour,
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or the loss of the dinosaurs,
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but the Earth has seen worse.
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00:05:26,200 --> 00:05:30,480
This is the story of the greatest mass
extinction event
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in Earth's history.
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00:05:36,960 --> 00:05:42,880
Something caused our planet's
life-support systems to fail,
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00:05:42,880 --> 00:05:47,640
wiping out most of the species on Earth.
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00:05:49,040 --> 00:05:52,040
And this is not an apocalyptic vision,
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not a doomsday prophesy.
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This actually happened.
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00:05:56,560 --> 00:06:00,200
252 million years ago,
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the Earth turned on the life that it
had nurtured for so long.
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00:06:09,480 --> 00:06:14,720
What does it take to destroy almost
all life on Earth?
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00:06:18,560 --> 00:06:20,560
And could it happen again?
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00:06:26,200 --> 00:06:29,760
Well, the answer lies in Earth's deep history...
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00:06:36,000 --> 00:06:40,640
..in a time long before humans
transformed the planet's surface...
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00:06:46,200 --> 00:06:48,800
..before the last Ice Age...
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00:06:53,560 --> 00:06:57,680
..before the asteroid impact wiped out
the dinosaurs...
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..in fact, back to a time before
dinosaurs
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00:07:07,600 --> 00:07:09,680
even existed at all.
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00:07:28,920 --> 00:07:35,080
From space, the Earth in the Late
Permian is a strange sight.
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00:07:35,080 --> 00:07:38,440
From one side, a water world,
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no land in sight.
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00:07:45,680 --> 00:07:50,960
But as the planet turns, something
else creeps into view...
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00:07:54,360 --> 00:07:59,200
..all the Earth's major landmasses
clustered as one.
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00:08:01,000 --> 00:08:03,800
This is Pangea...
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..a supercontinent rich with life.
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00:08:19,080 --> 00:08:23,640
Coastal waters teem with weird and
wonderful creatures.
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At once both alien,
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yet eerily familiar.
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00:08:35,320 --> 00:08:41,880
And in lush forests, a cacophony of
animal cries fill the air.
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00:09:09,680 --> 00:09:13,040
In many ways, the Earth in the Late Permian
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00:09:13,040 --> 00:09:15,320
was like the Earth we have today -
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00:09:15,320 --> 00:09:18,480
millions of species of plants and
animals, living together
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00:09:18,480 --> 00:09:20,920
in complex, interconnected webs
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which are nurturing and
self-sustaining.
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00:09:24,200 --> 00:09:28,800
But in other ways, it was a very alien world.
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00:09:28,800 --> 00:09:35,720
This was a time long before mammals or
even dinosaurs walked the Earth.
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But life was no less remarkable.
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Scuttling around in the scrub of the
Late Permian,
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you might have found one of these.
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00:09:44,720 --> 00:09:49,240
This is the cast of a beautiful fossil
of Nycteroleter.
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00:09:49,240 --> 00:09:54,120
It's part of an extinct group of
reptiles, and fed on things
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00:09:54,120 --> 00:09:57,720
like proto-cockroaches, dragonflies, millipedes.
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It's got quite large eyes,
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suggesting that it might have been nocturnal,
99
00:10:01,160 --> 00:10:05,160
and we also know that it had really
good hearing -
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00:10:05,160 --> 00:10:07,840
something quite unique for animals of
that time.
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00:10:09,000 --> 00:10:11,240
But then, look at this chap.
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00:10:11,240 --> 00:10:12,960
It's Dvinia.
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00:10:12,960 --> 00:10:14,880
It would've grown to about 50
centimetres.
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00:10:14,880 --> 00:10:17,040
Looked like a small dog.
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00:10:17,040 --> 00:10:21,120
Neither a mammal, nor a reptile, it's
got forward-facing eyes.
106
00:10:21,120 --> 00:10:23,960
It was perhaps a predator of some kind.
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00:10:23,960 --> 00:10:27,560
But, look, from the top, you can see
it's got really wide cheeks,
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00:10:27,560 --> 00:10:30,880
and the remains here of perhaps a
sagittal crest,
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suggesting that it had very powerful
muscles, a powerful bite.
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00:10:34,480 --> 00:10:38,480
In fact, it might have been fishing
for shellfish down on the beach
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00:10:38,480 --> 00:10:42,280
and crunching them up with its
powerful jaws.
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00:10:42,280 --> 00:10:45,360
But last, and perhaps most impressive,
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this is a magnificent specimen of a
super predator, Inostrancevia.
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00:10:51,960 --> 00:10:53,320
What an animal.
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00:10:53,320 --> 00:10:56,640
Just look at those sabre-tooth teeth
there.
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00:10:56,640 --> 00:10:58,240
Now, those are slashing tools.
117
00:10:58,240 --> 00:11:02,080
Those are for wounding prey, waiting
for it to bleed to death,
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00:11:02,080 --> 00:11:06,520
and then catching up with it and
swallowing large chunks whole.
119
00:11:06,520 --> 00:11:09,360
This animal would've grown to about 3
metres in length
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00:11:09,360 --> 00:11:11,240
and very fast-moving
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00:11:11,240 --> 00:11:15,320
and been terrorising the large
herbivores of its time.
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00:11:15,320 --> 00:11:18,080
What a fantastic beast it must have
been.
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00:11:20,760 --> 00:11:22,680
But by the end of the Permian,
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00:11:22,680 --> 00:11:26,280
along with nearly every other living
thing on Earth,
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00:11:26,280 --> 00:11:28,480
they would be dead.
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00:11:50,240 --> 00:11:53,120
We're not certain how it started,
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00:11:53,120 --> 00:11:56,560
but deep inside the ancient Earth,
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00:11:56,560 --> 00:11:59,800
superheated rock is rising...
129
00:12:02,080 --> 00:12:05,720
..pushing upwards against the solid
outer crust...
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00:12:09,520 --> 00:12:12,840
..until it can take no more.
131
00:12:17,440 --> 00:12:19,400
The crust fails.
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00:12:29,960 --> 00:12:33,360
The landscape physically torn apart,
133
00:12:33,360 --> 00:12:35,800
as lava floods onto the surface...
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00:12:37,000 --> 00:12:40,120
..forming great curtains of fire.
135
00:12:45,240 --> 00:12:50,080
This is just the beginning of the most
deadly volcanic event
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00:12:50,080 --> 00:12:51,480
in Earth's history.
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00:13:01,920 --> 00:13:05,760
We can get clues to what these ancient
eruptions were like
138
00:13:05,760 --> 00:13:08,200
by studying modern volcanoes.
139
00:13:16,320 --> 00:13:20,080
This is Tajogaite Volcano, in the
Canary Islands,
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00:13:20,080 --> 00:13:24,000
and in September of 2021, the ground
here split
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00:13:24,000 --> 00:13:28,560
and tonnes of lava, ash and toxic
gases exploded,
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00:13:28,560 --> 00:13:31,160
shaking the entire island.
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00:13:40,200 --> 00:13:41,960
Over three months,
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00:13:41,960 --> 00:13:48,920
170 million cubic metres of lava
poured onto the surface.
145
00:13:51,320 --> 00:13:55,240
It was the first eruption on the
island in 50 years.
146
00:14:03,160 --> 00:14:07,560
More than 7,000 people had to flee
their homes.
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00:14:20,000 --> 00:14:23,400
This volcano spewed out enough lava to
fill around
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00:14:23,400 --> 00:14:26,400
70,000 Olympic-sized swimming pools,
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00:14:26,400 --> 00:14:30,360
and that lava covered an area around
ten square kilometres -
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00:14:30,360 --> 00:14:32,480
which sounds pretty impressive,
151
00:14:32,480 --> 00:14:38,520
but it's just a teaspoon compared to
those at the end of the Permian.
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252 million years ago,
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around four million cubic kilometres
of lava, ash and toxic gases
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00:14:47,720 --> 00:14:51,360
erupted in a series of volcanic explosions
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00:14:51,360 --> 00:14:55,400
that went on for 2 million years.
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00:14:55,400 --> 00:14:59,960
The Permian eruptions were 1,000 times
greater than
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any witnessed by humans.
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And the ancient lava is still with us.
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00:15:07,600 --> 00:15:09,720
In Northwestern Siberia,
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00:15:09,720 --> 00:15:14,000
beneath a landscape of swamps and
flood plains,
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00:15:14,000 --> 00:15:18,640
scientists have discovered a colossal
lava field,
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dated a little over 250 million years old...
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..lava that covers over two-and-a-half million
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00:15:29,000 --> 00:15:30,520
square kilometres...
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..enough to bury the entire continent
of Australia
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hundreds of metres deep.
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00:15:46,560 --> 00:15:53,800
252 million years ago, Northern Pangea
was hell on Earth.
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00:15:58,000 --> 00:16:03,200
Fire fountains blast volcanic material
over six miles up
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00:16:03,200 --> 00:16:04,560
into the atmosphere...
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00:16:08,400 --> 00:16:12,240
..burning millions of square miles of forests.
171
00:16:21,880 --> 00:16:25,920
And clouds bloom high into the atmosphere,
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00:16:25,920 --> 00:16:27,600
blocking out the sun.
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00:16:32,560 --> 00:16:35,160
Plants wilt and die...
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00:16:40,400 --> 00:16:42,840
..ash falls like snow...
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..as vast swathes of Northern Pangea
lie in ruins.
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00:17:01,920 --> 00:17:06,520
These eruptions are on a scale almost
beyond imagination.
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00:17:08,760 --> 00:17:15,720
But lava still only covers less than
1% of Pangea's surface.
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00:17:15,720 --> 00:17:20,120
And elsewhere, something curious is happening.
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00:17:24,880 --> 00:17:28,560
A strange haze hangs in the air.
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00:17:35,080 --> 00:17:38,920
Nutrient-rich volcanic ash and sulphur,
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00:17:38,920 --> 00:17:44,600
transported thousands of miles,
reflect the sun's rays...
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00:17:46,200 --> 00:17:49,400
..pushing global temperatures down...
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00:17:56,400 --> 00:18:01,520
..and in places, causing a surge of
plant life to flourish.
184
00:18:07,680 --> 00:18:10,240
But death is coming.
185
00:18:26,320 --> 00:18:29,640
I've come to an outcrop in Northern
Italy,
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made of rock that formed at the same
time as those ancient eruptions.
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It's a fossilised crime scene
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00:18:41,680 --> 00:18:44,600
with a chilling tale to tell.
189
00:18:46,800 --> 00:18:52,720
Look at this thin, black seam that
runs all the way down here.
190
00:18:55,520 --> 00:18:57,760
It looks like coal to me,
191
00:18:57,760 --> 00:19:00,600
which would indicate that at one point...
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00:19:02,440 --> 00:19:04,000
..it was full of plant life.
193
00:19:04,000 --> 00:19:06,080
Probably full of lots of other life, too.
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00:19:08,000 --> 00:19:11,360
Coal is little more than ancient
organic matter
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00:19:11,360 --> 00:19:14,960
that's been subjected to extreme
temperatures and pressures
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00:19:14,960 --> 00:19:17,280
over millions of years.
197
00:19:17,280 --> 00:19:19,800
So, where we find coal today,
198
00:19:19,800 --> 00:19:22,720
we know there was once life.
199
00:19:22,720 --> 00:19:26,640
But the rocks above it here tell an
altogether different story.
200
00:19:33,120 --> 00:19:36,240
They're grey, dull, look a bit boring,
201
00:19:36,240 --> 00:19:38,760
a bit of a geological mush.
202
00:19:38,760 --> 00:19:40,920
But that's the point -
203
00:19:40,920 --> 00:19:45,040
because, aside from a few fossil microorganisms,
204
00:19:45,040 --> 00:19:50,720
scientists have found very little
evidence of life in these rocks.
205
00:19:50,720 --> 00:19:56,280
So, what they are telling us is that
252 million years ago,
206
00:19:56,280 --> 00:20:00,040
the landscape here was almost devoid
of life.
207
00:20:02,560 --> 00:20:09,120
In a geological blink of an eye,
almost all life here vanished.
208
00:20:09,120 --> 00:20:12,960
You can't help but feel a certain
sense of sadness.
209
00:20:12,960 --> 00:20:16,400
Holding this makes it so tangible.
210
00:20:19,440 --> 00:20:23,720
This was death on an unimaginable scale.
211
00:20:25,360 --> 00:20:29,480
But there's no evidence of lava here at all.
212
00:20:31,160 --> 00:20:34,680
When these rocks were laid down in
this part of Italy,
213
00:20:34,680 --> 00:20:38,560
they were thousands of miles away from
the eruptions in the north -
214
00:20:38,560 --> 00:20:42,240
certainly too far away for any direct impacts.
215
00:20:42,240 --> 00:20:44,880
But what's interesting is that geologists
216
00:20:44,880 --> 00:20:49,600
have found this line of death all over
the planet -
217
00:20:49,600 --> 00:20:52,600
China, Australia, South Africa.
218
00:20:52,600 --> 00:20:56,280
And no matter how far away from the
lava fields,
219
00:20:56,280 --> 00:20:58,960
there's a deathly silence in the
fossil record.
220
00:21:01,360 --> 00:21:07,200
The question is, what could have
killed this many creatures?
221
00:21:07,200 --> 00:21:12,200
What could have wiped out almost all
life on Earth?
222
00:21:31,800 --> 00:21:35,640
Something more than lava was emerging
from the Earth
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00:21:35,640 --> 00:21:37,360
in Northern Pangea.
224
00:21:42,160 --> 00:21:47,560
Billions of tonnes of gases are
injected high into the atmosphere.
225
00:21:56,400 --> 00:21:59,560
Water vapour, sulphur dioxide...
226
00:22:01,360 --> 00:22:06,360
..but primarily a gas we all know too
well -
227
00:22:06,360 --> 00:22:10,080
the greenhouse gas carbon dioxide.
228
00:22:30,320 --> 00:22:33,680
We're all becoming depressingly
familiar with what happens
229
00:22:33,680 --> 00:22:39,400
when you pump huge quantities of
carbon dioxide into the atmosphere.
230
00:22:39,400 --> 00:22:41,720
It's an experiment we've been running ourselves
231
00:22:41,720 --> 00:22:43,800
for more than 100 years.
232
00:22:43,800 --> 00:22:48,160
And the more the CO2, the more the
heat is locked in,
233
00:22:48,160 --> 00:22:51,080
and the hotter our Earth becomes.
234
00:22:52,160 --> 00:22:55,720
Global warming isn't a localised effect.
235
00:22:55,720 --> 00:22:58,280
The whole planet feels the burn.
236
00:22:59,520 --> 00:23:01,120
Here we are, yeah, dead ahead.
237
00:23:01,120 --> 00:23:03,160
No creature is safe.
238
00:23:03,160 --> 00:23:06,480
You've got a little feeding party
taking place here at the moment.
239
00:23:06,480 --> 00:23:08,680
Oh, look at that!
240
00:23:09,680 --> 00:23:12,080
Oh, yes, yes!
241
00:23:15,440 --> 00:23:18,560
Sorry to be a child, but it's always...
242
00:23:18,560 --> 00:23:21,080
Oh, oh, oh, oh!
243
00:23:21,080 --> 00:23:23,480
Oh, I just saw it catch a fish!
244
00:23:23,480 --> 00:23:24,560
Oh!
245
00:23:26,080 --> 00:23:28,440
There are several species here.
246
00:23:28,440 --> 00:23:29,880
Bottlenose...
247
00:23:32,080 --> 00:23:36,120
..common, rough tooth, spotted.
248
00:23:37,720 --> 00:23:41,880
And dolphins, of course, can live in
much warmer waters than these.
249
00:23:41,880 --> 00:23:44,480
So, you might imagine they're not the
sorts of creatures
250
00:23:44,480 --> 00:23:47,600
that would be harmed by global warming.
251
00:23:47,600 --> 00:23:51,800
But sadly, I've got to tell you, these
dolphins are in trouble.
252
00:23:58,160 --> 00:24:02,920
It's not always the temperature that
poses a danger to life.
253
00:24:02,920 --> 00:24:06,280
In fact, for some, the heat is a blessing.
254
00:24:08,520 --> 00:24:11,200
Let's see what I've managed to catch.
255
00:24:12,640 --> 00:24:14,960
Wow, rather a lot.
256
00:24:14,960 --> 00:24:19,200
This mass of detritus here is plankton,
257
00:24:19,200 --> 00:24:22,360
much of it phytoplankton, algae.
258
00:24:22,360 --> 00:24:25,760
Now, most of the organisms wouldn't
hurt anything,
259
00:24:25,760 --> 00:24:29,200
but there is one species, Karenia Brevis -
260
00:24:29,200 --> 00:24:31,960
well, that's an algae with a superpower.
261
00:24:31,960 --> 00:24:34,440
You see, when the water warms up here,
262
00:24:34,440 --> 00:24:37,840
it goes into a reproductive frenzy,
263
00:24:37,840 --> 00:24:41,480
producing blooms many hundreds of
times greater
264
00:24:41,480 --> 00:24:43,360
than it normally would.
265
00:24:43,360 --> 00:24:45,640
But what's good for the algae, it
turns out,
266
00:24:45,640 --> 00:24:48,160
is not so good for the dolphins.
267
00:24:48,160 --> 00:24:52,960
Because recent research has shown that
this is extremely toxic.
268
00:24:52,960 --> 00:24:55,360
So, the small fish eat the algae,
269
00:24:55,360 --> 00:24:57,440
the bigger fish eat the small fish,
270
00:24:57,440 --> 00:25:00,040
the dolphins the larger fish.
271
00:25:00,040 --> 00:25:03,280
And this organism has been implicated
272
00:25:03,280 --> 00:25:06,160
in the deaths of dozens of dolphins,
273
00:25:06,160 --> 00:25:08,600
found dead floating in the sea here.
274
00:25:10,560 --> 00:25:15,000
Rising temperatures affect different
parts of the food chain
275
00:25:15,000 --> 00:25:17,120
in different ways,
276
00:25:17,120 --> 00:25:20,960
throwing ecosystems out of balance...
277
00:25:20,960 --> 00:25:23,760
..often with deadly results.
278
00:25:25,240 --> 00:25:27,560
You see, when it comes to global warming,
279
00:25:27,560 --> 00:25:30,680
it's not the actual heat that kills
those creatures.
280
00:25:30,680 --> 00:25:34,880
It's the increases or decreases in
plant or animal populations
281
00:25:34,880 --> 00:25:40,680
which disrupt those long-evolved,
stable, beautiful ecosystems.
282
00:25:40,680 --> 00:25:46,320
Death by global warming is not short,
sharp, and painless.
283
00:25:46,320 --> 00:25:49,080
It's prolonged and torturous.
284
00:26:07,040 --> 00:26:10,080
As the temperatures rise across
Pangea...
285
00:26:16,720 --> 00:26:18,800
..trees begin to die.
286
00:26:33,840 --> 00:26:37,600
Holes appear in the once-thick canopy,
287
00:26:37,600 --> 00:26:40,640
bathing the ground in sunlight.
288
00:26:45,960 --> 00:26:48,560
For some, it's an opportunity.
289
00:26:49,560 --> 00:26:51,600
Weed-like plants flourish,
290
00:26:51,600 --> 00:26:53,880
like spore-bearing lycophytes.
291
00:26:57,240 --> 00:26:59,720
No longer struggling in the shadows,
292
00:26:59,720 --> 00:27:02,440
in times of stress, they thrive.
293
00:27:06,280 --> 00:27:09,080
And foreign species appear.
294
00:27:09,080 --> 00:27:13,680
Woody, seed-bearing cycads that once
only grew in the tropics
295
00:27:13,680 --> 00:27:16,440
are now abundant closer to the Poles.
296
00:27:21,560 --> 00:27:26,200
Surprisingly, some areas are now more
diverse
297
00:27:26,200 --> 00:27:28,480
than before the warming began.
298
00:27:29,720 --> 00:27:34,040
But this is an ecosystem out of
balance.
299
00:27:37,280 --> 00:27:39,440
A few more degrees' warming,
300
00:27:39,440 --> 00:27:42,160
and the living world will crumble.
301
00:27:57,320 --> 00:28:01,000
But then something strange happens.
302
00:28:03,560 --> 00:28:06,760
Red hot rivers of lava...
303
00:28:06,760 --> 00:28:09,400
..turn to solid rock.
304
00:28:11,360 --> 00:28:14,160
Just as quickly as they started,
305
00:28:14,160 --> 00:28:17,320
the eruptions fall silent.
306
00:28:30,440 --> 00:28:33,600
The CO2 released from the Permian lavas
307
00:28:33,600 --> 00:28:36,920
likely dwarfed human emissions to date.
308
00:28:39,280 --> 00:28:43,560
But even that may have been just part
of the story.
309
00:28:47,440 --> 00:28:49,240
These eruptions would have produced
310
00:28:49,240 --> 00:28:51,920
an inordinate amount of carbon dioxide
-
311
00:28:51,920 --> 00:28:53,520
gigatons of the stuff,
312
00:28:53,520 --> 00:28:56,360
certainly enough to manifest some
global warming,
313
00:28:56,360 --> 00:29:00,440
perhaps in the realm of an increase of
5 or 6 degrees Celsius,
314
00:29:00,440 --> 00:29:02,280
something like that.
315
00:29:02,280 --> 00:29:05,320
Now, that's a substantial amount of heating,
316
00:29:05,320 --> 00:29:08,960
but it's not significant enough to
account for all of the deaths
317
00:29:08,960 --> 00:29:11,360
that we see in the fossil record.
318
00:29:11,360 --> 00:29:13,640
Yes, there would have been extinctions,
319
00:29:13,640 --> 00:29:17,360
but not 90% of all life on Earth.
320
00:29:29,200 --> 00:29:33,160
The effects of carbon dioxide can be
lethal.
321
00:29:33,160 --> 00:29:36,720
But some scientists think there was
another killer.
322
00:29:39,960 --> 00:29:42,920
The volcanism hadn't stopped.
323
00:29:42,920 --> 00:29:47,040
It had just entered a terrifying new phase.
324
00:29:49,920 --> 00:29:52,520
Beneath the desolate lava field...
325
00:29:53,520 --> 00:29:57,280
..hot magma still flows,
326
00:29:57,280 --> 00:30:00,920
forming great reservoirs
underground...
327
00:30:00,920 --> 00:30:05,120
..and slowly baking the Earth's crust.
328
00:30:18,120 --> 00:30:20,680
The rocks underground were older -
329
00:30:20,680 --> 00:30:24,600
hundreds of millions of years older
than the land above.
330
00:30:24,600 --> 00:30:26,840
And amongst them,
331
00:30:26,840 --> 00:30:30,000
there was plenty of this stuff -
332
00:30:30,000 --> 00:30:33,480
coal and other rocks rich in carbon.
333
00:30:33,480 --> 00:30:36,600
Now, what happens when magma meets coal?
334
00:30:36,600 --> 00:30:42,480
Well, the coal burns, releasing yet
more dangerous carbon dioxide.
335
00:30:42,480 --> 00:30:44,440
But that was just the half of it.
336
00:30:44,440 --> 00:30:47,040
You see, it wasn't just coal.
337
00:30:47,040 --> 00:30:50,720
There was also lots of salt.
338
00:30:50,720 --> 00:30:56,960
And salt like this can form when
ancient lakes and seas dry up.
339
00:30:56,960 --> 00:31:00,080
And when magma comes into contact with
salt,
340
00:31:00,080 --> 00:31:02,360
things get really nasty.
341
00:31:05,040 --> 00:31:07,320
The salt begins to bake,
342
00:31:07,320 --> 00:31:12,720
releasing toxic halogen gases rich in
bromine and chlorine -
343
00:31:12,720 --> 00:31:17,560
archenemies of the Earth's fragile
ozone layer,
344
00:31:17,560 --> 00:31:24,080
that thin layer that protects us from
the sun's most harmful rays.
345
00:31:24,080 --> 00:31:28,400
So, what I'm trying to say here is
that the magma had found its way
346
00:31:28,400 --> 00:31:32,880
into the worst possible place on the
planet.
347
00:31:32,880 --> 00:31:35,440
It had created a time bomb.
348
00:31:41,720 --> 00:31:45,640
That magma begins to heat up the coal
and salt
349
00:31:45,640 --> 00:31:49,240
to a temperature of 800 degrees Celsius.
350
00:31:53,520 --> 00:31:56,760
A poisonous cocktail of gases begins
to build...
351
00:32:03,720 --> 00:32:07,440
..until the land above can take no more.
352
00:32:40,640 --> 00:32:43,560
More CO2 floods the atmosphere,
353
00:32:43,560 --> 00:32:46,320
pushing global temperatures even higher.
354
00:32:48,520 --> 00:32:54,000
But this time, there were also those
toxic halogen gases.
355
00:33:01,600 --> 00:33:06,760
We've seen the Earth's ozone layer
damaged in recent history,
356
00:33:06,760 --> 00:33:11,760
when artificial chemicals created a
so-called ozone hole.
357
00:33:13,200 --> 00:33:16,280
But in the Permian, the halogens may
have eroded
358
00:33:16,280 --> 00:33:19,040
the ozone layer away entirely...
359
00:33:21,680 --> 00:33:26,520
..bathing all life in deadly UV
radiation.
360
00:33:28,520 --> 00:33:32,240
Scientists have noticed something
strange going on with the pollen
361
00:33:32,240 --> 00:33:34,520
at the end of the Permian.
362
00:33:34,520 --> 00:33:36,240
Take a look at this.
363
00:33:36,240 --> 00:33:42,200
This is a highly-magnified image of a
modern pine pollen grain.
364
00:33:42,200 --> 00:33:44,960
And you can see it's got two essential
parts to its structure -
365
00:33:44,960 --> 00:33:47,760
the central circular part here, the
corpus,
366
00:33:47,760 --> 00:33:50,040
and then these winged sacchi.
367
00:33:50,040 --> 00:33:54,000
These are wind-pollinated pollen species,
368
00:33:54,000 --> 00:33:56,520
and these help it float through the air.
369
00:33:56,520 --> 00:33:58,840
But have a look at this.
370
00:33:58,840 --> 00:34:02,360
This is an image of a fossilised
coniferous pollen grain
371
00:34:02,360 --> 00:34:04,480
from the time of those eruptions.
372
00:34:04,480 --> 00:34:08,200
It's got three of these wing
structures.
373
00:34:08,200 --> 00:34:11,120
This one has four.
374
00:34:11,120 --> 00:34:15,240
These pollen grains are malformed,
misshapen and, in fact,
375
00:34:15,240 --> 00:34:17,280
if you look at this last one,
376
00:34:17,280 --> 00:34:21,160
this appear to have been in the
process of dividing,
377
00:34:21,160 --> 00:34:23,600
but somehow it's failed.
378
00:34:23,600 --> 00:34:26,640
These are mutant pollen grains,
379
00:34:26,640 --> 00:34:29,960
and it's thought that the mutation was
caused by
380
00:34:29,960 --> 00:34:32,760
the excessive UV radiation -
381
00:34:32,760 --> 00:34:39,000
evidence that those gases had really
damaged the Earth's ozone layer.
382
00:34:39,000 --> 00:34:41,160
Now, other theories are available.
383
00:34:41,160 --> 00:34:43,720
Others believe that, in fact, it was
acid rain
384
00:34:43,720 --> 00:34:48,400
that caused these mutations, or merely
the extreme heat.
385
00:34:48,400 --> 00:34:50,480
But whatever the cause,
386
00:34:50,480 --> 00:34:55,240
what's clear is that at this point,
life was on the brink.
387
00:35:10,640 --> 00:35:15,360
At first glance, it seems nothing has
changed.
388
00:35:15,360 --> 00:35:18,680
But this already fragile ecosystem
389
00:35:18,680 --> 00:35:23,520
has taken a lethal dose of UV radiation.
390
00:35:23,520 --> 00:35:27,240
Healthy-looking plants are now sterile.
391
00:35:29,760 --> 00:35:33,640
As individuals die, they aren't
replaced.
392
00:35:38,200 --> 00:35:42,760
Once-lush forests become ravaged wastelands.
393
00:35:49,800 --> 00:35:54,480
The collapse in the oceans is even
more dramatic.
394
00:35:54,480 --> 00:35:57,440
Carbon dioxide reacts with sea water,
395
00:35:57,440 --> 00:35:59,800
which begins to turn to acid.
396
00:36:04,720 --> 00:36:07,640
And oxygen levels plummet -
397
00:36:07,640 --> 00:36:10,880
in some places, dropping to zero.
398
00:36:13,760 --> 00:36:16,360
Algae blooms across the planet.
399
00:36:18,080 --> 00:36:21,320
As it decomposes, it poisons the ocean
400
00:36:21,320 --> 00:36:24,280
with toxic hydrogen sulphide...
401
00:36:34,200 --> 00:36:40,640
..until the seafloor becomes a foetid
bed of slime.
402
00:36:44,440 --> 00:36:47,920
Sulphurous tides lap barren shores,
403
00:36:47,920 --> 00:36:51,320
and a smell like rotten eggs hangs in
the air.
404
00:36:53,600 --> 00:36:58,400
The Earth's rich complexity has vanished,
405
00:36:58,400 --> 00:37:00,640
seemingly for good.
406
00:37:13,720 --> 00:37:15,800
It's been called many things -
407
00:37:15,800 --> 00:37:20,200
the Great Dying, the mother of all
mass extinction events
408
00:37:20,200 --> 00:37:24,200
or, simply, when life nearly died.
409
00:37:24,200 --> 00:37:27,320
The details are still a bit hazy.
410
00:37:27,320 --> 00:37:31,040
Was it a single short, sharp, giant catastrophe,
411
00:37:31,040 --> 00:37:34,400
or a wave of smaller catastrophes?
412
00:37:34,400 --> 00:37:37,560
To what extent did the extinctions
occur on land
413
00:37:37,560 --> 00:37:40,680
versus extinctions in the water?
414
00:37:40,680 --> 00:37:42,920
The fossil record is patchy,
415
00:37:42,920 --> 00:37:45,200
so there's plenty of room for academic debate.
416
00:37:45,200 --> 00:37:49,360
But the one thing that almost everyone
agrees upon
417
00:37:49,360 --> 00:37:53,200
is that these ancient eruptions caused extinctions
418
00:37:53,200 --> 00:37:56,120
on an unprecedented scale.
419
00:37:56,120 --> 00:38:02,000
Figures frequently cited suggest that
70% of land vertebrates
420
00:38:02,000 --> 00:38:06,240
and 96% of marine life
421
00:38:06,240 --> 00:38:09,920
vanished off the face of the Earth forever.
422
00:38:12,360 --> 00:38:15,720
By the time the eruptions finally stop,
423
00:38:15,720 --> 00:38:20,960
the average global temperature has
risen by over 10 degrees Celsius.
424
00:38:23,600 --> 00:38:30,000
Vast areas of the Earth's surface are
completely uninhabitable,
425
00:38:30,000 --> 00:38:33,600
and nearly all species are gone.
426
00:38:42,200 --> 00:38:47,440
The End-Permian extinction has a
virtually undisputed claim
427
00:38:47,440 --> 00:38:52,040
to being the worst moment in the
history of the Earth.
428
00:38:53,160 --> 00:38:57,840
But from the ashes, there was a
glimmer of hope,
429
00:38:57,840 --> 00:39:00,720
because life had survived somewhere.
430
00:39:00,720 --> 00:39:05,120
It must have. Otherwise, we wouldn't
be here.
431
00:39:06,600 --> 00:39:11,360
In a way, we are all survivors of the
Great Dying.
432
00:39:11,360 --> 00:39:17,880
You see, every living organism on the
planet has an ancient ancestor,
433
00:39:17,880 --> 00:39:21,560
perhaps millions, perhaps billions of
generations back,
434
00:39:21,560 --> 00:39:25,000
that not only survived that mass
extinction event
435
00:39:25,000 --> 00:39:28,760
but then went on to prosper in the
aftermath
436
00:39:28,760 --> 00:39:31,840
and then to repopulate the Earth.
437
00:39:34,840 --> 00:39:38,600
The Great Dying may have been the end
of one world,
438
00:39:38,600 --> 00:39:42,440
but it was also the beginning of a new
one.
439
00:39:53,320 --> 00:39:57,440
The Triassic Earth is a shadow of its
former self.
440
00:40:02,160 --> 00:40:05,280
Many creatures seek refuge underground...
441
00:40:11,200 --> 00:40:14,080
..sheltering from blistering temperatures
442
00:40:14,080 --> 00:40:16,440
and lethal UV radiation.
443
00:40:21,800 --> 00:40:27,160
Above ground, a single plant species
dominates the landscape.
444
00:40:28,360 --> 00:40:32,640
Pleuromeia - a weed-like plant lucky
enough to make it
445
00:40:32,640 --> 00:40:37,280
through the apocalypse and find itself
with few competitors.
446
00:40:41,240 --> 00:40:44,240
It helps provide sustenance for the cockroaches,
447
00:40:44,240 --> 00:40:47,080
who also made it through unscathed.
448
00:40:52,040 --> 00:40:55,320
But just because the eruptions have stopped
449
00:40:55,320 --> 00:40:59,400
doesn't mean that life's troubles are over.
450
00:41:12,320 --> 00:41:16,000
The Early Triassic was dominated by
extreme heat.
451
00:41:16,000 --> 00:41:19,400
The fossil record shows us that ocean
temperatures could have been
452
00:41:19,400 --> 00:41:22,200
up to 14 degrees centigrade warmer
453
00:41:22,200 --> 00:41:24,560
than they were prior to the eruptions.
454
00:41:24,560 --> 00:41:28,920
In some places, the water was as warm
as it is in a hot tub -
455
00:41:28,920 --> 00:41:31,880
too extreme for most marine organisms.
456
00:41:35,680 --> 00:41:39,160
And on land, things weren't faring
much better.
457
00:41:39,160 --> 00:41:43,240
There were probably heatwaves of up to
60 degrees centigrade -
458
00:41:43,240 --> 00:41:47,680
a temperature that would have
seriously inhibited photosynthesis.
459
00:41:47,680 --> 00:41:53,280
In fact, for the 10 million years
following the mass extinction event,
460
00:41:53,280 --> 00:41:58,520
we see no significant coal reserves
laid down anywhere on Earth.
461
00:41:58,520 --> 00:42:02,600
There simply weren't enough trees.
462
00:42:02,600 --> 00:42:07,640
For life to bounce back, the planet
needed to cool down.
463
00:42:15,120 --> 00:42:19,000
In normal times, the Earth can cool itself -
464
00:42:19,000 --> 00:42:22,320
over thousands of years, removing
carbon dioxide
465
00:42:22,320 --> 00:42:26,680
from the atmosphere, in part through
reacting with rainwater.
466
00:42:27,960 --> 00:42:32,160
But vast areas of Pangea are desert.
467
00:42:32,160 --> 00:42:33,800
Little rain falls.
468
00:42:37,040 --> 00:42:41,640
So, it takes millions of years for
temperatures to drop.
469
00:42:53,080 --> 00:42:57,080
And even then, recovery is slow.
470
00:43:01,120 --> 00:43:06,160
The living world's struggling to
regain the diversity it once knew.
471
00:43:17,160 --> 00:43:19,760
But salvation was coming.
472
00:43:25,320 --> 00:43:31,600
High in the Dolomite Mountains is
evidence for a bizarre event,
473
00:43:31,600 --> 00:43:35,200
one that may have helped life rebound.
474
00:43:38,520 --> 00:43:40,440
Look at this.
475
00:43:40,440 --> 00:43:43,480
Absolutely stunning.
476
00:43:43,480 --> 00:43:49,280
And these mountains were formed very
shortly after the extinction event,
477
00:43:49,280 --> 00:43:52,640
and they're made up of sedimentary
rock -
478
00:43:52,640 --> 00:43:55,520
layers of sediment on top of one
another,
479
00:43:55,520 --> 00:43:59,200
each corresponding to a time in the
Earth's history.
480
00:43:59,200 --> 00:44:01,480
The oldest rocks are at the bottom,
481
00:44:01,480 --> 00:44:03,720
around 238 million years old.
482
00:44:03,720 --> 00:44:05,520
The youngest at the top,
483
00:44:05,520 --> 00:44:08,440
about 200 million years old.
484
00:44:08,440 --> 00:44:11,600
Now, you might imagine that if we
wanted to uncover the secrets
485
00:44:11,600 --> 00:44:14,400
in these rocks, we'd take some, break
them open
486
00:44:14,400 --> 00:44:17,320
and look for some details - but not
here.
487
00:44:17,320 --> 00:44:22,120
The secrets in these rocks are held in
plain view.
488
00:44:22,120 --> 00:44:25,520
The key is the shape of the mountains.
489
00:44:25,520 --> 00:44:30,480
It hints at a planetary intervention
that, just a few decades ago,
490
00:44:30,480 --> 00:44:33,640
we had no idea happened.
491
00:44:33,640 --> 00:44:38,680
Look, it starts steep at the bottom,
rises sharply,
492
00:44:38,680 --> 00:44:40,960
and then there's a shallow shelf,
493
00:44:40,960 --> 00:44:44,640
and then it rises steeply again to the peak,
494
00:44:44,640 --> 00:44:46,680
currently in the clouds.
495
00:44:46,680 --> 00:44:51,200
But the bit that we're interested in
is that shallow slope,
496
00:44:51,200 --> 00:44:56,600
which corresponds to about 2 million
years in the Earth's history,
497
00:44:56,600 --> 00:44:59,520
and to a very strange period of time.
498
00:45:01,240 --> 00:45:05,720
This shallow slope is evidence of a
softer rock type
499
00:45:05,720 --> 00:45:08,120
that's been eroded over the years.
500
00:45:10,520 --> 00:45:11,840
Here we go.
501
00:45:15,880 --> 00:45:18,600
This is a lump of sandstone.
502
00:45:18,600 --> 00:45:21,400
It's a soft sedimentary rock.
503
00:45:21,400 --> 00:45:23,520
The key is in the name.
504
00:45:23,520 --> 00:45:27,880
It's made up of sediments, like sand,
which wash off of the land,
505
00:45:27,880 --> 00:45:31,360
down into the rivers and then down
into the sea.
506
00:45:31,360 --> 00:45:34,880
So, what I'm holding here is evidence
of rain -
507
00:45:34,880 --> 00:45:36,480
rather a lot of rain,
508
00:45:36,480 --> 00:45:41,120
because in places, this layer is about
80 metres deep.
509
00:45:42,800 --> 00:45:45,040
Sandstone is a common rock,
510
00:45:45,040 --> 00:45:48,080
but scientists have discovered similar layers
511
00:45:48,080 --> 00:45:50,480
right across the planet,
512
00:45:50,480 --> 00:45:55,520
leading some to think this was the
result of a global deluge.
513
00:45:57,000 --> 00:45:59,880
Now, we're not precisely sure why it started.
514
00:45:59,880 --> 00:46:02,800
It could have been underwater volcanic activity
515
00:46:02,800 --> 00:46:04,840
disrupting the water cycle.
516
00:46:04,840 --> 00:46:07,360
But at some point in the Triassic,
517
00:46:07,360 --> 00:46:12,080
a time famed for being excruciatingly
hot and arid,
518
00:46:12,080 --> 00:46:14,240
it started to rain.
519
00:46:14,240 --> 00:46:17,840
And, boy, did it rain - because that rain
520
00:46:17,840 --> 00:46:23,080
defined the Earth's climate for almost
2 million years.
521
00:46:36,640 --> 00:46:41,160
18 million years after the mass extinction,
522
00:46:41,160 --> 00:46:42,880
the heavens open...
523
00:46:45,200 --> 00:46:49,120
..a sudden increase in rainfall across Pangea.
524
00:46:51,640 --> 00:46:54,280
The rain causes more extinctions...
525
00:46:56,160 --> 00:46:58,560
..but the planet is reborn.
526
00:47:07,040 --> 00:47:10,000
Where arid shrub land once stood...
527
00:47:11,520 --> 00:47:14,200
..lush forests now grow.
528
00:47:15,800 --> 00:47:20,040
It's been called the greening of
Triassic Earth,
529
00:47:20,040 --> 00:47:24,640
and it marked the beginning of much of
the life we know today.
530
00:47:36,600 --> 00:47:39,040
There were new species of crocodiles...
531
00:47:41,160 --> 00:47:43,120
..amphibians...
532
00:47:46,280 --> 00:47:49,880
..even early ancestors of modern mammals.
533
00:48:00,200 --> 00:48:03,560
But the mammals would have to wait in
the wings.
534
00:48:03,560 --> 00:48:07,840
Other creatures were set to inherit
this renewed world.
535
00:48:15,040 --> 00:48:16,360
Look at this.
536
00:48:18,000 --> 00:48:19,720
See this impression in the rock here?
537
00:48:19,720 --> 00:48:24,880
Look, there are one, two, three toes.
538
00:48:24,880 --> 00:48:27,640
This is a dinosaur footprint,
539
00:48:27,640 --> 00:48:31,280
and I love the fact that I can put my hand
540
00:48:31,280 --> 00:48:34,280
where a dinosaur once put its foot.
541
00:48:34,280 --> 00:48:37,880
Now, whether dinosaurs existed before
the rains, we can't be sure.
542
00:48:37,880 --> 00:48:41,160
If they did, it was only as an obscure group
543
00:48:41,160 --> 00:48:42,920
in the south of Pangea.
544
00:48:42,920 --> 00:48:45,560
But in the millions of years after the rains,
545
00:48:45,560 --> 00:48:47,040
they certainly prospered.
546
00:48:47,040 --> 00:48:53,360
In some places, 90% of the vertebrate
fossils are dinosaurs.
547
00:48:53,360 --> 00:48:55,560
Why did they suddenly do so well?
548
00:48:55,560 --> 00:48:57,200
Well, it could be down to the food.
549
00:48:57,200 --> 00:49:01,320
They could use it more efficiently to
grow bigger more quickly.
550
00:49:01,320 --> 00:49:03,440
But whatever the reason,
551
00:49:03,440 --> 00:49:06,560
dinosaurs went on to dominate the Earth.
552
00:49:07,640 --> 00:49:08,840
I love this!
553
00:49:15,480 --> 00:49:17,720
By the end of the Triassic,
554
00:49:17,720 --> 00:49:21,920
the stage is set for the reptiles to
rule supreme.
555
00:49:26,240 --> 00:49:32,280
This will be their world for the next
140 million years.
556
00:49:35,720 --> 00:49:38,800
The age of the dinosaurs is dawning.
557
00:49:51,680 --> 00:49:55,240
In one way, the End-Permian extinction
558
00:49:55,240 --> 00:49:59,600
exposed the fundamental fragility of life.
559
00:49:59,600 --> 00:50:02,720
Countless species of plants and
animals were wiped out
560
00:50:02,720 --> 00:50:04,640
by those volcanic eruptions,
561
00:50:04,640 --> 00:50:07,800
and it took millions of years to recover.
562
00:50:07,800 --> 00:50:11,640
But perhaps the event also taught us
another lesson
563
00:50:11,640 --> 00:50:14,160
about the tenacity of life -
564
00:50:14,160 --> 00:50:18,560
because the living world did bounce
back, to be just as complex
565
00:50:18,560 --> 00:50:22,960
and just as beautiful, in fact, maybe
even more so.
566
00:50:29,680 --> 00:50:33,480
But there's a big unspoken question here.
567
00:50:33,480 --> 00:50:37,360
For over 100 years, we've been pumping
carbon dioxide into
568
00:50:37,360 --> 00:50:41,960
the atmosphere and watching as global
temperatures creep up.
569
00:50:43,640 --> 00:50:50,080
So, what can the mass extinction 252
million years ago teach us
570
00:50:50,080 --> 00:50:53,040
about our own climate change event?
571
00:50:58,760 --> 00:51:03,560
I think the big lesson we've just
learned is that the living world
572
00:51:03,560 --> 00:51:05,920
will ultimately be fine.
573
00:51:05,920 --> 00:51:10,080
Even if we don't address our climate
and biodiversity crisis,
574
00:51:10,080 --> 00:51:13,760
if we burn every last lump of coal and
drop of oil,
575
00:51:13,760 --> 00:51:17,280
if we leave this place as a complete hellscape,
576
00:51:17,280 --> 00:51:21,680
whilst we might perish, life will
bounce back,
577
00:51:21,680 --> 00:51:25,840
and this will all be beautiful again -
578
00:51:25,840 --> 00:51:27,560
which begs the question,
579
00:51:27,560 --> 00:51:31,360
"Should we bother to preserve and
protect it?"
580
00:51:31,360 --> 00:51:36,000
Well, that extinction event 252
million years ago
581
00:51:36,000 --> 00:51:38,080
was part of a planetary process.
582
00:51:38,080 --> 00:51:40,760
It was a chance volcanic eruption.
583
00:51:43,680 --> 00:51:45,600
Think of all of that suffering.
584
00:51:45,600 --> 00:51:47,720
Think of all of that wastage.
585
00:51:50,320 --> 00:51:54,680
Do we want those sorts of extinctions
on our conscience?
586
00:51:56,320 --> 00:51:57,560
I don't think so.
587
00:52:16,680 --> 00:52:21,320
In this episode, we saw how an
Earth-shattering eruption
588
00:52:21,320 --> 00:52:24,600
destroyed almost all life on Earth.
589
00:52:29,440 --> 00:52:32,160
- This is the closest our planet has
ever been
590
00:52:32,160 --> 00:52:33,840
to going back to square one.
591
00:52:36,040 --> 00:52:38,200
- To understand the scale of the event,
592
00:52:38,200 --> 00:52:41,760
scientists mapped the Permian lava
fields of Russia -
593
00:52:41,760 --> 00:52:44,800
known as the Siberian Traps.
594
00:52:46,640 --> 00:52:50,400
- I have actually been to the Siberian Traps
595
00:52:50,400 --> 00:52:53,200
and flown helicopters.
596
00:52:54,560 --> 00:52:58,920
The helicopter is right, mm...there.
597
00:52:58,920 --> 00:53:02,960
Floated on boats, hiked,
598
00:53:02,960 --> 00:53:07,720
ridden on trains all over Arctic Siberia,
599
00:53:07,720 --> 00:53:11,000
looking for remnants of the Siberian Traps.
600
00:53:12,320 --> 00:53:18,000
And these lava flows go distances that
boggle the mind.
601
00:53:18,000 --> 00:53:23,640
The 1 million cubic miles that we have
is probably a minimum number,
602
00:53:23,640 --> 00:53:26,800
and it's a minimum because not all of
the rocks
603
00:53:26,800 --> 00:53:28,920
are exposed at the surface.
604
00:53:28,920 --> 00:53:32,280
We also sampled the rocks of the
Siberian Traps
605
00:53:32,280 --> 00:53:35,360
with sledgehammers and rock hammers
606
00:53:35,360 --> 00:53:37,160
and a lot of hard work.
607
00:53:39,200 --> 00:53:42,120
- The rock samples were key to
understanding
608
00:53:42,120 --> 00:53:46,120
why the Earth's climate changed so dramatically.
609
00:53:46,120 --> 00:53:49,240
- When magma comes up from deep within
the Earth,
610
00:53:49,240 --> 00:53:52,280
it has gases dissolved in it,
611
00:53:52,280 --> 00:53:56,160
gases like carbon dioxide and sulphur dioxide.
612
00:53:56,160 --> 00:53:59,240
These gases come out into bubbles,
613
00:53:59,240 --> 00:54:04,120
a bit like when you take the lid off a
soda bottle and it fizzes.
614
00:54:04,120 --> 00:54:08,920
- But these gases told a contradictory story.
615
00:54:08,920 --> 00:54:12,480
- Sulphur dioxide and carbon dioxide
have opposite effects
616
00:54:12,480 --> 00:54:14,320
on the Earth's atmosphere.
617
00:54:14,320 --> 00:54:17,960
Sulphur dioxide reflects sunlight back
into outer space,
618
00:54:17,960 --> 00:54:19,560
causing global cooling,
619
00:54:19,560 --> 00:54:22,120
whereas carbon dioxide is a greenhouse gas
620
00:54:22,120 --> 00:54:23,720
and can lead to global warming.
621
00:54:26,160 --> 00:54:29,720
- It turns out that different volcanic
gases hang around in our atmosphere
622
00:54:29,720 --> 00:54:31,240
for different amounts of time
623
00:54:31,240 --> 00:54:35,560
because of their different chemical properties.
624
00:54:35,560 --> 00:54:37,840
- Sulphur dioxide tends to stay in the atmosphere
625
00:54:37,840 --> 00:54:40,040
for a shorter period of time,
626
00:54:40,040 --> 00:54:41,960
because it can get rained out.
627
00:54:43,040 --> 00:54:46,240
- But carbon dioxide can stay in the
Earth's atmosphere for hundreds,
628
00:54:46,240 --> 00:54:47,720
if not thousands of years.
629
00:54:49,160 --> 00:54:53,120
- Scientists think that heat-trapping
carbon dioxide
630
00:54:53,120 --> 00:54:57,000
would have built up in the atmosphere,
warming the planet.
631
00:54:59,640 --> 00:55:03,920
And there were other clues in the
fossil record.
632
00:55:03,920 --> 00:55:06,680
- So, we can measure what temperatures
were like in the past
633
00:55:06,680 --> 00:55:08,400
by the study of fossils,
634
00:55:08,400 --> 00:55:10,720
and particularly fossil bone material.
635
00:55:10,720 --> 00:55:12,320
So, when the bone is formed,
636
00:55:12,320 --> 00:55:14,840
it's partly controlled by the temperature.
637
00:55:14,840 --> 00:55:17,320
And so by studying these bones, we're
able to see
638
00:55:17,320 --> 00:55:19,800
what the temperatures were like back
in the past.
639
00:55:23,600 --> 00:55:30,000
- Temperature rises of up to 7 degrees
brought a deluge of rainfall.
640
00:55:30,000 --> 00:55:33,320
Known as the Carnian Pluvial Episode,
641
00:55:33,320 --> 00:55:37,280
some scientists think these conditions
were essential
642
00:55:37,280 --> 00:55:39,480
to the success of the dinosaurs.
643
00:55:40,800 --> 00:55:46,120
- My research suggests that more rain
means it's better for the plants.
644
00:55:46,120 --> 00:55:51,520
This era of warm, wet conditions
really boosted plant diversity.
645
00:55:51,520 --> 00:55:54,800
More plants equals more insects, more plant-eaters,
646
00:55:54,800 --> 00:55:57,480
and then you get more meat-eaters as well,
647
00:55:57,480 --> 00:55:59,440
and dinosaurs are part of that growth.
648
00:56:01,840 --> 00:56:03,360
So, this is Herrerasaurus.
649
00:56:03,360 --> 00:56:05,960
This is one of the first dinosaurs to appear.
650
00:56:05,960 --> 00:56:08,680
And as you can see by the sharp teeth here,
651
00:56:08,680 --> 00:56:12,440
this was a meat-eater, one of the top predators.
652
00:56:12,440 --> 00:56:16,960
- The evidence for this growth is
written in the rock record.
653
00:56:16,960 --> 00:56:20,280
- The success of the dinosaurs after
this event is seen in
654
00:56:20,280 --> 00:56:24,000
just an abundance of their fossils,
but also in their sort of indirect
655
00:56:24,000 --> 00:56:27,800
records that they leave in the forms
of their footprints as well.
656
00:56:27,800 --> 00:56:30,080
- Before the Carnian Pluvial Episode,
657
00:56:30,080 --> 00:56:33,120
dinosaurs and their relatives only
made up around 5% of the footprints
658
00:56:33,120 --> 00:56:35,520
at these different fossil sites.
659
00:56:35,520 --> 00:56:39,000
After the Carnian Pluvial Episode, we
see a big increase -
660
00:56:39,000 --> 00:56:40,800
it jumps up to 70%.
661
00:56:42,400 --> 00:56:45,680
- The explosion in the population of dinosaurs
662
00:56:45,680 --> 00:56:49,120
is a brand-new area of research.
663
00:56:49,120 --> 00:56:52,120
- We can see that the ecosystems were changing,
664
00:56:52,120 --> 00:56:54,280
but what actually would've affected
the dinosaurs,
665
00:56:54,280 --> 00:56:56,680
what would've caused them to be successful,
666
00:56:56,680 --> 00:56:58,480
we don't know yet.
667
00:56:58,480 --> 00:57:00,480
This is why there's so many palaeontologists
668
00:57:00,480 --> 00:57:02,240
doing active research.
669
00:57:08,680 --> 00:57:10,000
- Next time...
670
00:57:13,400 --> 00:57:17,160
..we journey deeper into the past,
671
00:57:17,160 --> 00:57:20,960
to witness one of the strangest
moments in history...
672
00:57:22,840 --> 00:57:25,760
..a global deep freeze..
673
00:57:27,400 --> 00:57:30,320
..that transformed the Earth...
674
00:57:30,320 --> 00:57:32,200
..into an ice world.
675
00:57:37,400 --> 00:57:40,320
If the Earth could talk, what would it
tell us?
676
00:57:40,320 --> 00:57:42,880
Well, the Open University imagine how
it might answer
677
00:57:42,880 --> 00:57:44,360
some of our questions.
678
00:57:44,360 --> 00:57:46,960
To experience this interactive presentation,
679
00:57:46,960 --> 00:57:49,520
go to the website on the screen and
follow the links
680
00:57:49,520 --> 00:57:51,400
to The Open University.
55697
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