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Speaker 1: Since the Earth was formed billions of years ago, it's

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been hit by a series of disasters. Two hundred and

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fifty million years ago, the largest volcanic eruptions the planet

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has ever seen nearly erased all life on Earth. It

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was the greatest mass extinction in the history of the planet.

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But without it, humans could never have evolved. This is

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the story of the Planet of Fire. Over the last

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four and a half billion years, life on Earth has

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lurched from one terrible disaster to the next. It's difficult

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to grasp the immense timescale of the events that shaped us,

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so imagine Earth's history compressed into the twenty four hours

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of a single day at ten forty in the evening.

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That's two hundred and fifty million years ago, all life

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on the planet faced extinction. The Earth was in a

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period of prehistory called the Permian, A cataclysmic event kick

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started a deadly chain reaction that wiped out nearly all

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animal and plant species on the planet. It was called

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the end Permian extinction and was the greatest die off

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in the history of the planet. Ninety five percent of

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all creatures around the globe were wiped out. According to

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South African paleontologist Roger Smith, it was earth darkest hour.

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Speaker 2: The income extinction was as dramatic as a mass extinction

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could be. Since the beginning of life on Earth, there

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has been no other one that has come close to

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the ninety five percent of species on Earth, both in

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land and sea, disappearing within a very short space of time.

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Speaker 1: It was a catastrophic wipebout and changed the course of evolution.

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We humans are only here today because of the five

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percent of creatures who survived.

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Speaker 2: Had it not been for those few survivors, those few

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animals which were preadapted or able to get through that

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great drought, we would not have had life on Earth.

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Speaker 1: What happened? How did it happen? It's a mystery that's

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puzzled scientist since evidence of the catastrophe was first discovered

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almost half a century ago. Figuring out what cause the

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extinction is a key element to understanding the evolution of

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life on Earth. In the Karoo basin, South Africa, Smith

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studies an area that was once teeming with animals that

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predate the dinosaurs.

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Speaker 2: But two hundred and fifty million years ago, this would

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have looked a very different place. Rainfall in the mountain

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areas were feeding Mississippi sized rivers, which meandered themselves slowly

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across the plains. This was a fully developed, stable ecosystem.

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Speaker 1: Small plant eating creatures called Dictodon thrived here, scurrying around

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in the vegetation. Huge herds of calcized herbivores called dicynodonts

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grazed on the plains, but a vicious killer stalked the herds.

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Over one hundred and fifty million years before, t Rex

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Gorgonopsian was Earth's deadliest carnivore. Armed with serrated, interlocking teeth,

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this ferocious animal was the ancient world's top predator. But

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all these creatures were doomed. None of them survived the

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mass extinction. What killed them clues to how the Permian

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world died. Lie buried in the rocks of South Africa's

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Karu Basin. Under this scrub, Paleontologists have unearthed layers of

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sedimentary rock from this turbulent time.

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Speaker 3: Now.

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Speaker 2: Sedimentary rocks like this are characterized by layers, each layer

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representing a point in time when deposition was taking place.

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The oldest layers are at the bottom and the youngest

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layers at the top.

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Speaker 1: These rocks are like a time machine, taking us back

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a quarter of a billion years one layer higher up.

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This formation offers clues to what ended the Permian world.

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Speaker 2: Here we're sitting at the very top of the Permian

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and this particular interval shows us something very dramatic in

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the rock record. Below me we have green and bluish

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gray rocks that pretty suggests that the environment was wet.

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Speaker 1: These rocks are littered with fossils. But just above this layer,

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it's a very different story.

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Speaker 2: Suddenly everything turns red, and that's reddening is an indication

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of drying, rapid drying and warming.

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Speaker 1: These red rocks reveal a sudden and dramatic rise in

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temperature and mark the point in time when life on

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Earth nearly died.

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Speaker 2: The fossils tell us at this point there is virtually

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nothing left on Earth, and we go into a dead zone.

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Speaker 1: Life had almost ceased to exist. And not just here.

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The dead zone of red rock is found all around

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the world. This meant that two hundred fifty million years ago,

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the climate change in mass extinction was global. Something huge

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on a planet wide scale pushed temperatures up by twenty

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degrees fahrenheit and killed virtually all life on Earth ten

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forty pm on our clock of the Earth's history. Two

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hundred and fifty million years ago, the planet was in

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climate free fall. Scientists have discovered the temperatures rose by

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about twenty degrees. The sudden and dramatic global warming changed

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the course of evolution on Earth. It caused a mass

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extinction so devastating that some scientists thought it must have

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been caused by something extraordinary, something extraterrestrial. Could it have

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been an asteroid strike? They knew a cosmic impact would

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have sent billions of tons of dust high into the atmosphere,

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blocking out the sun, stopping plant growth, reducing temperatures, and

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causing the food chain to collapse. An extinction from an

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asteroid strike would have happened within decades, but that's not

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the story the rock evidence is telling us. Over the

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last decade, Professor Paul Wignall and researchers at Leeds University

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in England have been examining rocks from the dead Zone

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around the time of the devastating mass extinction. They've collected

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thousands of samples and taken hours of video on their

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expeditions to Greenland. The rocks confirm a period of climate change,

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and much more. They record the story of mass extinction

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on land and sea and provide a clearer picture of

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the die off than ever.

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Speaker 4: The extinction is like the biggest fossil crime scene of

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all time, and so the great thing about Greenland is

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that we have such a great record at the crime scene.

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If you're like, there's just a huge amount of information

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to be collected. So it provides us with an extremely

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detailed record of what happened, probably one of the best

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records of that time interval.

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Speaker 1: What's more, these Greenland rocks build a solid case against

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the asteroid impact theory.

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Speaker 4: One of the most obvious clues would be that the

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extinction should go extremely fast, within sort of days and

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weeks of an impact, everything will just sassis drop dead

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in a matter of years, and so that should be

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raise a sharp when we see in a fossil record,

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we should see just an abrupt line or termination, and

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that's not what we see.

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Speaker 1: Instead, Wignoll's rock showed that the extinction happened over a

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period of one hundred thousand years, far too long to

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be the result of a meteor strike. The Greenland's team's

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discovery meant that something else must have caused the catastrophic extinction,

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and geologist Mike Benton thinks he knows what. He believes

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the disaster began deep beneath the Earth's surface.

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Speaker 5: If it is not impact, then the next most obvious

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dramatic instant kind of catastrophe is initiated by volcanic eruptions

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of some kind, so you obviously look for some center

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of volcanic eruptions.

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Speaker 1: Volcanoes are nature's ultimate destructive force. Fueled by unimaginable pressure

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deep within the planet, they shoot molten rock and toxic

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gases high into our atmosphere. In nineteen seventy five, the

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eruption of Mount Tobochik in Russia was so huge the

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plume of ash and debris was visible from space. But

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geologists know that volcanic eruptions were far bigger and more

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powerful two hundred and fifty million years ago, because they

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found the aftermath in eastern Russia. Today. Deep beneath the

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frozen wastes of one of the most remote corners of

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the Siberia is evidence of the catastrophe that nearly killed

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off life. A vast expanse of ancient lava flows forming

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a bleique landscape called the Siberian Traps.

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Speaker 4: The Siberian Traps are a style of volcanism which we

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don't see today. They represented the biggest style of vulcanism

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that the Earth ever experiences or produces.

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Speaker 1: Earth's ancient volcanic eruptions dwarf anything we might witness today.

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At the end of the Permian period, millions of cubic

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miles of magma built up beneath the Siberian crust. The

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entire region began to bulge upwards, and then like a

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giant blister, the Earth erupted, spewing out vast amounts of lava,

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flooding the area under a sea of molten rock. It

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was a type of volcanic eruption called a flood basalt.

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Here was the force behind the mass extinction two hundred

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and fifty million years ago. The Siberian flood basalt released

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enough lava to cover an area of the size of

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the United States under one mile of molten rock. Siberia

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has long since cooled, but Iceland is still one of

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the world's most geologically active places. Here, Mike Benton researches

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the terrible impact even a small flood basalt could have had.

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Speaker 5: We're here in the middle of a lava field in

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Lachee in Iceland, because this is a very well documented

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historical basalt eruption that can act as a good analogy

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for the Siberian traps. In seventeen eighty three, a vent

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eruption happened here which lasted for about eight months.

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Speaker 1: Seventeen mile long volcanic vents shot fountains of lava four

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thousand feet into the air, but it was tiny compared

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to the Siberian eruptions. Even so, it was a disaster.

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Speaker 5: Volcanoes produce three things. The lava is one that will

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kill things locally, but it produces ash and most importantly gas.

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Now the lava goes a relatively short distance, the ash

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will go further flying through the air. But what really

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kills are the gases.

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Speaker 1: The Larky eruption produced huge quantities of sulfur dioxide. It's

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a gas which has a deadly impact on the environment.

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When it mixes with water vapor in the atmosphere, it

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turns into sulfuric acid and falls to Earth as acid rain.

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Speaker 5: That has a terrible effect, as was recorded by the

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people at Lucky, where they reported that it burned people's eyeballs.

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It made it hard for them to breathe because it

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congested their lungs. Livestock suffered lesions and burning of their skin,

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and plants were killed off.

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Speaker 1: The whole food chain began to collapse, and that was

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just the start. Some sulfuric acid didn't fall back to

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earf It stayed in the atmosphere in small droplets. Question

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These reflected sunlight away from the planet, cooling its surface.

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Speaker 5: The cooling following the Lucky eruption was catastrophic. It killed

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more people than the immediate damage by sulfuric acid. It

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created very cold winters for two or three years after

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the eruption, not just on Iceland, but throughout much of

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northern Europe. People reported crop failures and death as a result.

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Speaker 1: Benton's analysis of the Larky eruption has shown that the

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cooling effect produced by volcanic sulfur dioxide is deadly and

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that the effects can be felt thousands of miles away.

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Imagine how devastating the Siberian traps must have been. Larkie

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spewed out gas and lava for eight months and covered

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an area of about two hundred square miles in molten rock.

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The Siberian traps erupted for nearly half a million years.

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They produced about two million square miles of lava that's

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two hundred thousand times larger than Larkie. Using Larkie as

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a model, Benton can begin to reconstruct the chain of

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events that turned the Siberian eruptions into a global killer.

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Speaker 5: The most likely sequence of events starts with these massive

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eruptions in Siberia, with lava spreading over thousands of square

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kilometers square miles of landscape and causing destruction and devastation

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wherever they went.

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Speaker 1: The eruptions released billions of tons of sulfur dioxide into

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Earth's atmosphere, which created acid rain and volcanic winters and

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scent global temperatures plummeting around the world. The climate change

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killed plants, and the food chain fell apart. The plants failed,

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herbivores like dicynodonts, starved, and where they starved, the carnivores

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that ate them died too. Ten per cent of species perished.

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But this was just the beginning. Another gas released by

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the Siberian traps was about to make things much much worse.

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Ten forty PM on Earth's evolutionary clock. Two hundred fifty

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million years ago, a series of giant volcanic eruptions have

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plunged the planet into chaos. The sulfur dioxide released by

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the Siberian traps has devastated animal and plant populations. In England,

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paleontologist Paul Wignall conducts post mortems on the victims of

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the Permian extinction, and these fossils he collected in Greenland

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definitely felt the effects of volcanic gases.

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Speaker 4: The first things that start suffering in the entire fossil

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record is the plant record. We start seeing a change

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in the composition of plants, and also we start to

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see the appearance of some very strange mutated sports.

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Speaker 1: The fossilized plants reveal a world struggling to adapt to

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climate change. They also record the effects of a second

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deadly volcanic gas, carbon dioxide.

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Speaker 4: Looking at the surfaces of leaves and the number of

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little holes that are in the sources of leaves is

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actually monitor of how much common dioxide there is.

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Speaker 1: Plants need carbon dioxide to create energy. They breathe it

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in through tiny holes on the back of their leaves.

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The more carbon dioxide in the atmosphere, the fewer holes

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the plant needs to absorb it. When scientists studied fossilized

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leaves dating back two hundred and fifty million years, they

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discovered a sudden, dramatic reduction in the number of breathing holes.

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It seemed that at the start of the extinction, levels

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of carbon dioxide surged, and that meant one thing. The

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Siberian trap eruptions must have released billions of tons of

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CO two. This greenhouse gas changed global cooling into global warming.

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Scientists calculate that the amount of carbon dioe oxide in

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Earth's atmosphere at the time of the eruptions was twenty

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times higher than it is today, more than enough to

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seriously affect the climate. It was global warming gone mad.

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Speaker 5: The result of these Siberian Trap eruptions was a rise

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in global temperature of at least five degrees centigrade, and

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they happened episodically, so that it may be there were

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pulses repeated and repeated off temperature rise.

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Speaker 1: A rise of five degrees centigrade that's about ten degrees

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fahrenheit may sound small to us, but it had a

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massive impact on the Earth's climate. Warming Earth's atmosphere affects

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how rain is generated and where it falls. By raising

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Earth's temperature, volcanic CO two altered global weather systems in

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equatorial regions, it simply stopped raining. In South Africa, the

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Karou Basin felt the full impact of this change in climate.

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Its lush floodplains became a scorched desert. Paleontologist Roger Smith

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studies how this rapidly changing landscape impacted the Careu's inhabitants,

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and he's just discovered one of the victims.

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Speaker 2: Here we have an instituted skull of Dasyanodon. It's one

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of the last of the big calcized herbivores of the

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Permian period, and at this level, which is just below

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the extinction, this represents probably the last gasp of the

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Permian herbivores.

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Speaker 1: The global warming marked and evolutionary watershed in Earth's history.

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Animals and plants suffered drought and starvation. Thirty five percent

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of them perished, But the fallout from the Siberian Traps

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was only just beginning. The rise in global temperatures triggered

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a domino effect and unleashed the next terrible phase of extinction.

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This time in the oceans ten forty pm on the

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Earth's clock. Two hundred and fifty million years ago, massive

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volcanic eruptions first released sulfur dioxide that cooled the planet,

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then carbon dioxide that heated it up. The sea sawing

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climate killed animals and plants. By the millions, Extinction ruled

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the land. It was the first terrible phase of the

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extermination of virtually all life on Earth, but a critical

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moment in the story of man's evolution. The future of

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life hung by a thread, but not everywhere. So far,

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the oceans had escaped unscathed.

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Speaker 5: The oceans at the end of the permie were teeming

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with life. There were quite complex reefs made up of

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corals and various other kinds of creatures that were fixed

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to the seabed. Those rich life there were sharks swimming

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in the shallows. The water would have been pale blue,

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like any typical tropical sea, so at a distance that

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it would have looked like a modern coral reef.

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Speaker 1: Perhaps climate change was about to end this. Paleontologist Paul

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Wignall has found evidence of the next deadly phase of

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the mass extinction, the death of the oceans.

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Speaker 4: This is a really nice example of blocks that we

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get from Greenland. The evidence is first of all, of

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a black which is typical when you have no oxygen around.

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But even more telltale is these these lovely sort of

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golden crystals which we can see on the surface, and

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this is pyrite or fool's gold, and we'd only find

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this if there was no oxygen around on the seafloor.

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Speaker 1: It's an important breakthrough. Fool's gold can only form in

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an environment that lacks oxygen. Its discovery in two hundred

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and fifty million year old rocks means only one thing.

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Somehow the Earth's oceans had lost their oxygen.

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Speaker 4: It was clear that there was something major going on

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which hadn't been discovered before. What we could see was

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it was sudden lack of oxygen at the end Permian

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mass extinction, as a completely new extinction phenomenon. It is

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then that we realized that we were now looking at

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a very different way of killing life in the seas.

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Speaker 1: But lower oxygen levels alone can't explain why so many

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species died in the oceans. It's a mystery that research

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00:26:38,279 --> 00:26:41,440
at Green Lakes National Park in Upstate New York has

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helped to solve. Marine geologist Lee Cump has discovered the

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process that he thinks was responsible for the extermination of

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nearly all marine life two hundred and fifty million years ago.

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Speaker 3: We're here at Green Lake because as we view this

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as a microcosm of the ocean that may have existed

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at the end of the Permian at the time of

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this great mass extinction. It's a really unique habitat here

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that's unusual in terms of most lakes. It's like a

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typical lake at the surface, but lurking down below is

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this poisonous water.

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Speaker 1: The lake looks normal, but under the surface it's dying,

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just like the ancient Permian oceans. The water is stagnating,

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its oxygen levels dropping. Over the past five years, comp

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and divers from Penn State University have been monitoring the

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lake's slow death. At the bottom, they found strange colonies

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of purple sulfur bacteria, an organism that only lives in

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water rich in a highly toxic gas called hydrogen sulfide.

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Hydrogen sulfide is a waste product produced by bacteria which

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thrive in water which has no oxygen.

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Speaker 3: Once the auction level drops then to the point where

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there's no oxygen left. Then organisms that can't stand oxygen

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being to thrive, and these organisms have a waste product,

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hydrogen sulfide that is poisonous to air breathing life.

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Speaker 1: Hydrogen sulfide is a vital ingredient in the formation of

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Fool's gold. The large amounts of Fool's gold discovered in

332
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the two hundred and fifty million year old Greenland rocks

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suggest that the same process that's happening in this lake

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was happening in the Permian oceans. Cump and his team

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research the rising levels of hydrogen sulfide in the lake.

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They do this by measuring the growth of purple sulfur

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00:29:00,960 --> 00:29:05,920
bacteria recording the changing depth at which it can be found.

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They know they found it when they pull out pink water.

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Speaker 3: We're looking for the pink water because that's indicative of

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where these purple sulfur bacteria live. So this is our

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00:29:18,759 --> 00:29:22,559
marker of where these organisms have a very large population density.

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There are so many there that they create this pink water.

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Speaker 1: Below this toxic layer of pink water, oxygen breathing animals

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cannot survive. Cump is charted the changing depths at which

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pink water can be found in Green Lake.

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Speaker 3: Oh yeah, that's rotten eggs. That's nasty stuff.

347
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Speaker 1: He's discovered that does oxygen levels in the lake drop,

348
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the amount of poisonous hydrogen sulfide increases, and the pink

349
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water can be found closer to the surface. It means

350
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that the poison is rising up through the water, killing

351
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all of the oxygen breathing animals who live there. The

352
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Green Lakes are just a small expanse of water, but

353
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imagine it on a global scale.

354
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Speaker 3: If we were to take a satellite picture of the

355
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Permian Ocean, the regions that are green today would have

356
00:30:27,319 --> 00:30:30,799
been pink when viewed from space because of the abundance

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of the purple sulfur bacteria.

358
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Speaker 1: Comes Green Lakes research gives us an insight into what

359
00:30:37,359 --> 00:30:40,119
was happening in the world's oceans at the time of

360
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the mass extinction. Rocks from the same period tell us

361
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that it was a global phenomenon. Oceans and seas were

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starved of oxygen and saturated with poison. Something major must

363
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have happened to trigger the removal of oxygen, But what

364
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In the Green Lakes. It's caused by stagnating water. The

365
00:31:10,160 --> 00:31:16,279
water has stopped circulating and Recently, researchers have discovered that

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00:31:16,400 --> 00:31:19,519
two hundred and fifty million years ago, the same thing

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happened on a global scale. Normally, oxygen dissolves into seawater

368
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at the surface. It's then transported by currents circulating between

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00:31:33,799 --> 00:31:40,160
the equator and the poles. Sunlight at the equator warms

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00:31:40,240 --> 00:31:45,759
the sea water. As this warm water moves towards the poles,

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00:31:45,960 --> 00:31:50,160
it cools and sinks, carrying its dissolved oxygen down with it,

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allowing the oceans and its inhabitants to breathe. This same

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00:31:58,000 --> 00:32:01,400
process was happening two hundred and fifty million years ago,

374
00:32:04,039 --> 00:32:07,640
but then the Siberian Traps came along and raised Earth's

375
00:32:07,640 --> 00:32:09,440
temperature by about ten degrees.

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Speaker 4: A significance of that for the world as a whole,

377
00:32:13,759 --> 00:32:16,000
and particularly the oceans, is the way it affects circulation

378
00:32:16,119 --> 00:32:19,519
in the world's oceans. It's a bit like leaving a

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00:32:19,559 --> 00:32:23,839
goldfish bowl in the window in bright sunshine. The water

380
00:32:23,920 --> 00:32:26,000
there it warms up, it loses its oxygen, and it

381
00:32:26,079 --> 00:32:28,480
essentially stagnates. And so if you magify that to an

382
00:32:28,480 --> 00:32:32,000
oceanic scale, then that's effectually what we think is happening

383
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in the oceans. At the end of the pomium.

384
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Speaker 1: The evidence suggests that two hundred and fifty million years ago,

385
00:32:42,240 --> 00:32:46,519
the rapid global warming created by volcanic gases warmed not

386
00:32:46,559 --> 00:32:53,680
only the atmosphere, it also warmed the oceans. They stopped

387
00:32:53,720 --> 00:32:58,920
circulating oxygen and stagnated, becoming breeding grounds for poisonous hydrogen

388
00:32:59,000 --> 00:33:00,680
sulfide producing bacteria.

389
00:33:04,839 --> 00:33:08,119
Speaker 3: We think that the warming then led to the development

390
00:33:08,359 --> 00:33:10,839
of the build up of hydrogen sulfide and the deep ocean.

391
00:33:11,119 --> 00:33:14,279
This built up to such large concentrations that it invaded

392
00:33:14,559 --> 00:33:18,440
into the shallow part of the ocean and displaced all

393
00:33:18,480 --> 00:33:21,960
of the air breathing organisms from those environments and eventually

394
00:33:21,960 --> 00:33:23,880
provided them no place of shelter.

395
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Speaker 1: Climate change triggered by the Siberian traps had already killed

396
00:33:32,319 --> 00:33:38,279
around a third of all species on land. By raising

397
00:33:38,319 --> 00:33:41,839
the temperature of Earth's oceans, it then caused the death

398
00:33:41,920 --> 00:33:46,240
of virtually all life in the sea. But the killing

399
00:33:46,480 --> 00:33:51,759
wasn't finished. Lurking at the bottom of the oceans was

400
00:33:51,839 --> 00:33:57,799
another killer, one that would wipe out practically everything else

401
00:33:57,960 --> 00:34:08,440
on Earth. Two hundred and fifty million years ago, the

402
00:34:08,559 --> 00:34:12,719
Siberian trap eruptions rocked the Earth and covered an area

403
00:34:12,760 --> 00:34:15,920
of the size of the United States in thick molten rock.

404
00:34:20,119 --> 00:34:22,400
They set in motion a chain of events that would

405
00:34:22,400 --> 00:34:29,719
wipe out virtually every species on Earth. Volcanic sulfur dioxide

406
00:34:29,760 --> 00:34:39,239
created acid rain and sudden winters. Next, carbon dioxide raised

407
00:34:39,239 --> 00:34:48,840
the planet's temperatures so high the food chain collapsed. Then

408
00:34:48,920 --> 00:34:57,000
the oceans warmed and the oxygen levels dropped. As a result,

409
00:34:57,079 --> 00:35:03,679
bacteria filled the water with lethal hydrogen sulfur, turning the

410
00:35:03,679 --> 00:35:09,679
planet seas into one big kill zone. Together, they cut

411
00:35:09,719 --> 00:35:13,920
global animal and plant populations by a staggering seventy percent

412
00:35:15,599 --> 00:35:20,920
in just fifty thousand years. Now, the animal and plant

413
00:35:20,920 --> 00:35:30,960
species that managed to survive suffered a final blow. In Iceland.

414
00:35:31,400 --> 00:35:34,840
Geologist Mike ben is searching for clues to this final

415
00:35:34,960 --> 00:35:37,079
deadly wave of extinctions.

416
00:35:39,280 --> 00:35:41,960
Speaker 5: There is a mystery to understand how the production of

417
00:35:42,039 --> 00:35:44,880
condoxide and a sudden rise in global temperature of about

418
00:35:44,920 --> 00:35:50,480
five degrees could have caused such a catastrophic event. A

419
00:35:50,519 --> 00:35:53,880
sudden rise in global temperature of about five degrees wouldn't

420
00:35:53,920 --> 00:35:57,000
in itself kill life in the catastrophic way we see.

421
00:35:57,639 --> 00:36:01,119
Something else must have caused that massive scale of extinction

422
00:36:01,199 --> 00:36:02,920
that we know happened that time.

423
00:36:06,360 --> 00:36:10,559
Speaker 1: The gases released from the Siberian traps triggered global warming

424
00:36:10,639 --> 00:36:13,880
that wiped out species, first on the land, then in

425
00:36:13,960 --> 00:36:23,599
the oceans. But then temperatures increased again by another ten degrees,

426
00:36:27,800 --> 00:36:32,039
the result a catastrophic second wave of extinction on the land.

427
00:36:34,760 --> 00:36:38,599
Scientists know that carbon dioxide released by the traps caused

428
00:36:38,599 --> 00:36:43,280
the first leap in global temperatures, but the second jump

429
00:36:43,360 --> 00:36:48,599
remained a puzzle. They needed to find something even stronger

430
00:36:48,639 --> 00:36:52,039
than CO two that could accelerate global warming on an

431
00:36:52,119 --> 00:37:00,840
unprecedented scale, and they found the answer to this mystery

432
00:37:01,159 --> 00:37:03,679
hidden in the depths of the ocean off the coast

433
00:37:03,719 --> 00:37:10,400
of Santa Barbara, California, About a mile off shore. Doctor

434
00:37:10,480 --> 00:37:14,960
Ira Leefer, a climatologist from the University of California, is

435
00:37:15,000 --> 00:37:21,239
on his way to monitor an unusual phenomenon. He's looking

436
00:37:21,320 --> 00:37:27,280
for another greenhouse gas, not carbon dioxide, but methane.

437
00:37:29,119 --> 00:37:33,519
Speaker 6: This area is where methane from deep within the Earth

438
00:37:34,079 --> 00:37:37,320
rises through the Earth's crust until it reaches the seabed

439
00:37:37,800 --> 00:37:40,719
and then through the water column to reach the sea

440
00:37:40,880 --> 00:37:42,239
surface as bubbles.

441
00:37:44,639 --> 00:37:47,679
Speaker 1: You can find these bubble seeps in coastal areas all

442
00:37:47,679 --> 00:37:53,599
over the planet. But this one's proximity to southern California

443
00:37:53,639 --> 00:37:58,000
has given scientists a unique opportunity to monitor one closely.

444
00:38:01,559 --> 00:38:05,599
Diving deep into the cold Pacific waters, Lifer's students collect

445
00:38:05,639 --> 00:38:10,760
methane samples straight from a vent in the seafloor. The

446
00:38:10,800 --> 00:38:14,239
sample showed that when it comes to global warming, methane

447
00:38:14,400 --> 00:38:15,639
is a supergas.

448
00:38:17,159 --> 00:38:21,119
Speaker 6: Methane is a very potent greenhouse gas, perhaps twenty to

449
00:38:21,159 --> 00:38:25,119
twenty five times more potent on a molecule per molecule

450
00:38:25,199 --> 00:38:29,079
basis than CO two. That means, if we add one

451
00:38:29,119 --> 00:38:32,360
molecule of CO two to the atmosphere one molecule of methane,

452
00:38:32,360 --> 00:38:34,599
that methane has twenty five times the effect.

453
00:38:36,039 --> 00:38:38,760
Speaker 1: The amount of methane released by seeps like this one

454
00:38:38,800 --> 00:38:42,000
in Santa Barbara is too small to explain the additional

455
00:38:42,079 --> 00:38:45,320
ten degree temperature rise recorded towards the end of the

456
00:38:45,360 --> 00:38:52,440
mass extinction. But there's another source of the gas that might.

457
00:38:54,960 --> 00:38:58,639
In the deep ocean, the most unexplored and least understood

458
00:38:58,639 --> 00:39:01,880
part of our world, there are vast quantities of a

459
00:39:01,920 --> 00:39:08,559
substance called methane hydrate. It's methane gas frozen in the

460
00:39:08,599 --> 00:39:13,079
cold water at the bottom of the sea. Today, there's

461
00:39:13,079 --> 00:39:16,559
an estimated thirty trillion tons of methane locked away in

462
00:39:16,679 --> 00:39:21,880
ice on the sea bend. If it turned into gas,

463
00:39:22,239 --> 00:39:27,679
there would be a global disaster. Lifer thinks that this

464
00:39:27,760 --> 00:39:31,480
may be what happened two hundred and fifty million years ago.

465
00:39:33,000 --> 00:39:37,519
Speaker 6: If we look at this massive extinction as comparable to

466
00:39:37,559 --> 00:39:42,000
a genocidal crime on an unimaginable scale, and we ask

467
00:39:42,079 --> 00:39:47,239
ourselves who are the criminal suspects, who's responsible? We'd look

468
00:39:47,239 --> 00:39:49,760
at the evidence and at the top of the short

469
00:39:49,760 --> 00:39:54,599
list is methane hydrates because of the vast size and

470
00:39:54,800 --> 00:39:56,679
they're known instability.

471
00:39:57,840 --> 00:40:03,280
Speaker 1: Frozen methane is ultrasensitive to heat. Raising its temperature by

472
00:40:03,320 --> 00:40:07,480
even a few degrees can destabilize it and trigger the

473
00:40:07,559 --> 00:40:09,920
release of this powerful greenhouse gas.

474
00:40:11,400 --> 00:40:15,800
Speaker 6: If the atmosphere warms for any particular reason, the ocean

475
00:40:15,800 --> 00:40:20,119
will methane hydrate will release methane. This will warm the atmosphere,

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leading to warmer temperatures and even more methane hydrate in

477
00:40:23,559 --> 00:40:27,760
the releasing its methane to the atmosphere, a positive feedback cycle.

478
00:40:30,440 --> 00:40:33,960
Speaker 1: Two hundred and fifty million years ago, billions of tons

479
00:40:34,000 --> 00:40:38,079
of volcanic gases produced by the Siberian traps triggered one

480
00:40:38,119 --> 00:40:45,239
of these cycles. The eruptions increased global temperature by ten degrees,

481
00:40:47,880 --> 00:40:51,000
enough to thaw the frozen methane hydrate at the bottom

482
00:40:51,039 --> 00:40:54,519
of the oceans and release billions of tons of potent

483
00:40:54,599 --> 00:41:06,360
greenhouse gas into the Earth's atmosphere. The temperature went up

484
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another ten degrees. The world was now twenty degrees hotter.

485
00:41:15,679 --> 00:41:18,639
Life couldn't adapt to the increase in heat and the

486
00:41:18,719 --> 00:41:23,840
sudden change in climate. Now nearly all life died out.

487
00:41:25,559 --> 00:41:31,320
First to go the remaining vegetation, next the few surviving herbivores,

488
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and with them the last of the carnivores vanished. Earth's

489
00:41:42,000 --> 00:41:48,480
food chain was more than broken. It hardly existed at all. Yet,

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in spite of the overwhelming series of catastrophes, new life

491
00:41:52,840 --> 00:41:58,719
and eventually humans, do evolve. We owe our existence to

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00:41:58,800 --> 00:42:07,400
an unlikely group of four legged heroes. Two hundred and

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fifty million years ago, the planet had been brought to

494
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its knees by savage volcanic eruptions. The toxic gases they

495
00:42:16,960 --> 00:42:24,000
released created worldwide climate chaos and wiped out most life

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00:42:24,039 --> 00:42:30,480
on Earth. For the planet's dominant species, there was no

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hope of survival.

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Speaker 4: For something like a gogonopsian, it would have seen a

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00:42:35,800 --> 00:42:40,400
world which would be changing. The very animals that it

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00:42:40,400 --> 00:42:43,320
was eating would were becoming rarer. It were getting a

501
00:42:43,360 --> 00:42:46,000
heck of a lot hotter, so terminal times for the

502
00:42:46,000 --> 00:42:48,320
gorgonopsians and all around it as well.

503
00:42:50,599 --> 00:42:54,239
Speaker 1: For these fearsome predators and for most living things, it

504
00:42:54,320 --> 00:42:59,280
was the end of the line. But in evolutionary terms,

505
00:42:59,360 --> 00:43:00,719
it was a new beginning.

506
00:43:02,440 --> 00:43:06,559
Speaker 5: Catastrophes can reset the evolutionary clock. That means that evolution,

507
00:43:06,800 --> 00:43:09,920
the whole direction of evolution, perhaps will change because the

508
00:43:09,960 --> 00:43:15,679
dominant species disappear, and then other species that were taking

509
00:43:15,679 --> 00:43:18,599
a less significant role before the event have their chance.

510
00:43:19,960 --> 00:43:23,199
Speaker 1: Two hundred and fifty million years ago, the mass extinction

511
00:43:23,360 --> 00:43:28,400
provided a priceless evolutionary opportunity to a small burrowing animal.

512
00:43:30,760 --> 00:43:36,320
These are cynodonts. They'd been a favorite snack for gerganopsians,

513
00:43:37,840 --> 00:43:41,480
but by burrowing underground, they'd stayed out of their predator's reach,

514
00:43:43,400 --> 00:43:45,920
and it proved to be a useful habit. When climate

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00:43:46,039 --> 00:43:52,119
change scorched the earth's surface, tubers and roots underground provided

516
00:43:52,159 --> 00:43:56,960
them with food and water. In South Africa's Careou Basin,

517
00:43:57,280 --> 00:44:00,880
paleontologist Roger Smith has made an important discovery.

518
00:44:01,480 --> 00:44:04,400
Speaker 2: We're looking at a burrow cast in the early Triassic,

519
00:44:04,559 --> 00:44:07,239
and we know from fossils that have been found in

520
00:44:07,320 --> 00:44:14,480
the ends of these casts that they are Cynodon. Cynodonts

521
00:44:14,519 --> 00:44:20,400
were digging burrows during the end perme extinction event, and

522
00:44:20,440 --> 00:44:23,719
it's very likely that that was one of the reasons

523
00:44:23,760 --> 00:44:26,599
why it was able to survive the great drought at

524
00:44:26,599 --> 00:44:27,159
that time.

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00:44:29,199 --> 00:44:32,599
Speaker 1: After the mouse extinction, these cynodonts went on to become

526
00:44:32,679 --> 00:44:38,079
one of the dominant species in the New World. Without them,

527
00:44:38,440 --> 00:44:40,760
we wouldn't be here today.

528
00:44:41,800 --> 00:44:45,000
Speaker 2: One of the cynodont line eventually became a mammal, and

529
00:44:45,280 --> 00:44:48,440
had it not been for the survivor through the cynodont line,

530
00:44:48,599 --> 00:44:52,639
mammals would not have existed and evolved, and nor would we.

531
00:44:52,880 --> 00:44:55,960
So we have a lot to thank the cynodonts for.

532
00:45:00,079 --> 00:45:03,440
Speaker 1: Quarter of a billion years ago. Life suffered a devastating blow,

533
00:45:06,239 --> 00:45:12,119
only to bounce back with new species and ecosystems. But

534
00:45:12,239 --> 00:45:15,639
the same kind of catastrophe that gave our earliest ancestors

535
00:45:15,639 --> 00:45:23,679
its chance could happen again. Eruptions like Iceland's Larkie come

536
00:45:23,760 --> 00:45:29,360
roughly every twenty million years. Gigantic ones like the Siberian

537
00:45:29,480 --> 00:45:35,440
Traps are rarer still they happen every few hundred million years,

538
00:45:36,119 --> 00:45:37,400
but they do happen.

539
00:45:38,280 --> 00:45:40,679
Speaker 5: It might shock be able to realize that the Earth

540
00:45:40,760 --> 00:45:44,239
can cause extreme devastation, and of course there's nothing that

541
00:45:44,320 --> 00:45:47,400
human beings with all their technology, could do to counter that.

542
00:45:47,960 --> 00:45:50,079
So that if there were to be an eruption today

543
00:45:50,679 --> 00:45:53,039
on the scale of Siberian Traps, it'd be hard to

544
00:45:53,079 --> 00:45:57,039
know how large numbers of human beings could protect themselves

545
00:45:57,119 --> 00:46:00,360
from it, So very likely that would be unbelievable death

546
00:46:00,360 --> 00:46:05,480
and destruction. Nobody would be safe.

547
00:46:06,880 --> 00:46:10,199
Speaker 1: But the biggest threat to mankind's future might not be

548
00:46:10,239 --> 00:46:14,960
a naturally occurring phenomenon. For the first time in history,

549
00:46:15,039 --> 00:46:19,039
the dominant species on Earth is upsetting the delicate balance

550
00:46:19,119 --> 00:46:25,199
of its own ecosystem. Our production of carbon dioxide is

551
00:46:25,280 --> 00:46:28,280
having a catastrophic impact on Earth systems.

552
00:46:31,440 --> 00:46:33,639
Speaker 3: We have the potential to release two or three thousand

553
00:46:33,679 --> 00:46:36,639
gigatons of carbon dioxide to the atmosphere in the next

554
00:46:36,639 --> 00:46:40,320
couple centuries. When we look at the Siberian Trap volcanism,

555
00:46:40,360 --> 00:46:43,880
we're talking about maybe similar quantities of carbon dioxide released

556
00:46:44,039 --> 00:46:47,159
but over millennia to maybe a million years, And so

557
00:46:47,440 --> 00:46:51,039
we're taking the whole Siberian Trap event and compressing it

558
00:46:51,119 --> 00:46:55,800
into the timescale of human activity one or two centuries,

559
00:46:56,079 --> 00:46:56,760
and that's scary.

560
00:46:58,599 --> 00:47:02,800
Speaker 1: It's already causing the plant to heat up, and scientists

561
00:47:02,880 --> 00:47:06,079
fear the runaway global warming of the past could happen

562
00:47:06,119 --> 00:47:11,360
again in the future. With more than thirty trillion tons

563
00:47:11,400 --> 00:47:14,639
of methane locked up as hydrates on the seafloor, the

564
00:47:14,679 --> 00:47:18,599
potential for another hydrate meltdown is as real today as

565
00:47:18,679 --> 00:47:23,480
it was two hundred and fifty million years ago, but

566
00:47:23,599 --> 00:47:26,119
this time we would have started it.

567
00:47:27,159 --> 00:47:28,760
Speaker 4: I'm sure that if you carry on what we're doing

568
00:47:28,760 --> 00:47:31,000
today in terms of pollution, we will cause a catastrophe.

569
00:47:31,039 --> 00:47:33,800
But how quickly is the big question.

570
00:47:35,679 --> 00:47:39,119
Speaker 1: The end Permian extinction was one of the most important

571
00:47:39,199 --> 00:47:43,079
chapters in the story of the evolution of life. It

572
00:47:43,199 --> 00:47:46,639
nearly wiped out life itself from the face of the planet.

573
00:47:48,639 --> 00:47:54,039
The few survivors became our direct ancestors. Without this mass

574
00:47:54,079 --> 00:47:57,639
extinction event, we probably wouldn't be here at all.

575
00:48:00,079 --> 00:48:00,119
Speaker 4: M