[Music] it's easy to forget when you're somewhere like this but the world has suffered from a series of global catastrophes disasters that have wiped out 99% of all the species that have ever lived but the forces that wiped out many of our ancestors are still at work today all we have to protect us is a wisp of atmosphere that all we have to stand on is a thin crust mankind could be the next dominant species to face extinction this is the story of how vulnerable we really are [Music] our planet has been shaped by an endless cycle of destruction and renewal the result 99% of all the species that have ever lived and now extinct but we tend to forget that the very forces that created all this havoc are just as powerful as ever we've been lucky so far we humans haven't been confronted by a truly global crisis yet but history reveals that we're much more at risk than we might think another big one could be just around the corner to understand the sheer scale of Earth's 4 and 1/2 billion year history imagine it as for 24 hours on a clock earth formed at midnight just 9 minutes later disaster struck our planet collided with another but earth survived and life evolved then at 8:30 p.m. another disaster the entire planet froze over 10:40 p.m. massive volcanic eruptions poisoned the planet life was nearly wiped out and at 11:38 p.m. a giant asteroid killed off the dinosaurs leading to the rise of the mammoths it was only in the closing minutes of the day that our planet became a place we'd recognized finally and under a minute to midnight a tough new species marched towards world domination they spread rapidly adapting to every challenge this new species was Homo sapiens us 85,000 years ago we were just heading out of Africa today we're everywhere this is the story of what happened since humans walk the planet and it shows just how vulnerable we really are again and again our ancestors confronted catastrophes all of them were different but any one of them could have stopped human civilization in its tracks the first disaster struck India 74 thousand years ago today evidence for this event can be found in the most unlikely place inside the cells of our bodies the story of the human race is written in our genes our genes control not only what we look like they also record evidence of past disasters for geneticists stephen oppenheimer it's a crucial clue as you move away from Africa the overall genetic diversity reduces in different populations until you get to the Native American populations which have the least diversity of of all but there is one place where there's an anomaly that's India in India genetic diversity is much much lower than it should be Oppenheimer believed some kind of disaster must have struck India's early settlers something so severe that their descendants genetic diversity is still affected today whatever it was this ancient disaster came close to wiping out the whole subcontinent it's difficult to estimate the size of reduction but it might have been down to about 600 people in the whole of India whatever struck India it was absolutely devastating something powerful enough to wipe out most of the population there is of course a very obvious catastrophe which is clearly dated in in the right time zone and that is Toba Toba is an Indonesian supervolcano it's last eruption is described by volcanologists as mega-colossal that's as big as it gets the date 74,000 years ago the estimated time of the Indian disaster was it a coincidence or was it the catastrophe that nearly killed off India's people on our clock of the Earth's history it's less than 2 seconds to midnight 74 thousand years ago the Indonesian supervolcano Toba erupted our ancient ancestors were faced with a terrifying threat volcanoes are one of the most powerful forces on the planet they can devastate whole regions and even affect global climate this is Mount Augustine off the coast of Alaska it's not a super volcano but it does illustrate the raw power of even a fairly small eruption it last blew in 2006 volcanologists John Power is monitoring how it's changed since then during the last eruption here Augustine blasted out 65 million cubic meters of rock so much debris that the summit grew by around 70 meters [Music] the eruption here was big though it was nothing compared to the power that could be unleashed by a supervolcano but studying smaller eruptions like Augustine give scientists an insight into the incredible power of the Toba eruption 74,000 years ago we're sitting on Augustin Island which is the home of Augustine volcano which you see behind us we are at the very northern end of what's called the Ring of Fire the Ring of Fire is the chain of volcanoes that surrounds the Pacific Ocean it's the world's most volcanically active region Mount Toba lies in Indonesia at its western edge here at many of these volcanoes in the Ring of Fire you have very explosive types of eruptions very powerful things that throw ash and so on out and very high elevation in the atmosphere there's no place where things are as quite as active as Indonesia Indonesian volcanoes have produced some of the most violent explosions on the planet the Toba eruption was the biggest on earth for two million years the forces are quite extreme during one of these large explosive volcanic eruptions that magma that's coming up underneath the volcano inside that magma you have a lot of gas and so on that's absorbed inside the magma itself and it's really this gas pressure that is driving a lot of the eruption an average volcano might contain enough gas and magma for the eruption to last for hours tober must have erupted for days but while such eruptions are rare disturbingly the volcanoes that cause them aren't 47 supervolcano sites have been discovered worldwide many are no longer active but a few are and they pose a real threat to human society the most famous one of all lies in the United States [Music] Yellowstone this bizarre landscape attracts over 3 million visitors every year [Music] they come here to witness the raw power of the parks famous geezers [Music] [Music] Yellowstone has the largest collection of such hydrothermal features anywhere on earth two-thirds of the world's geezers are in this one park that takes a lot of heat in fact it takes a super volcano like Toba only hidden below ground the last super-eruption here was 640 thousand years ago long before humans ruled the planet but even after all this time you can still see evidence of this ancient blast and the volcano itself remains active one day it will erupt again for geophysicists like Bob Smith Yellowstone is a vital Research Center for decades Smith has been studying the Yellowstone Caldera the giant volcanic crater in the center of the park his work reveals just how devastating the eruption of Toba would have been we're standing here on the east side of Yellowstone Lake and the sharp hill in front of us is actually the caldera boundary and the caldera essentially occupies this entire expanse of the landscape that we can see this whole system exploded out during the last giant eruption this is a giant felled air probably one of the biggest in the world that's known and this is active the sheer size of the Yellowstone system makes it a key location for the study of the ancient Toba super eruption the Yellowstone Caldera compares the Toba roughly in the same dimensions of about 50 kilometers by 40 kilometers dopa has a large lake occupying the caldera as you know stone lake so it's very similar in size these hills and rocks were sculpted by immense forces the whole landscape has been shaped by the giant volcanic furnace below the magma chamber this is the zone where molten rock gathers under immense pressure deep below the caldera the bigger the magma chamber the deadlier the eruption [Music] Smith's work here at Yellowstone shows Tobi's magma chamber would have been huge this is his laboratory [Music] we're here at a site the east side of the caldera where we have a seismograph which records ground motions that relate to the vibrations of the earth when they have the passage of seismic waves so we record two to three thousand earthquakes a year here by mapping his seismic data Bob can estimate the size of the magma chamber his results are stunning this simulation shows the whole United States Yellowstone Park lies near the middle its boundary marked in green Yellowstone Lake is marked in blue the edge of the volcanic caldera in red [Music] Bob seismic data plotted below the surface shows the enormous size of the magma system beneath the caldera Yellowstone's magma chamber is an astounding 16 miles wide 31 miles long and five miles deep that's 500 times the size of the city of London that's an awful lot of magma scientists now believe that topaz magma chamber was roughly the same size and the scary thing is that if that amount of magma erupted again it would be absolutely devastating and the aftermath would affect us all [Music] but the problem wouldn't be the red-hot magma the real killer would be volcanic ash when the magma actually finally makes it to the surface the gas pressure will drive that magnet fractured pulverize it into what a volcanologist would call ash this is pulverized rock and minerals all ground up together by the explosive forces that stuff can be thrown out into the atmosphere to a great altitude it's thought that Tobi's eruption column reached the very edge of space this footage from the Space Shuttle and the Russian volcano mount whose chefs go erupting shows how high ash can be blasted into the atmosphere talk about 74,000 years ago this was just the beginning as all those gases and and pulverized rock rise up it's hot very hot about 1,100 degrees centigrate when it comes out it'll rise up first buoyantly under its own heat and as it begins to cool it will become too heavy for the atmosphere to support and it will rush back down the sides of the volcano this creates a very hazardous phenomenon that we refer to as a pyroclastic flow these superheated ash flows can be immense at Ober they buried the landscape up to 200 metres deep any humans nearby would have been annihilated but even those outside this initial danger zone weren't safe Tobi's volcanic ash traveled for thousands of miles there was a massive release of ash and that ash went Northwest in the Indian Ocean and covered India 12 and a half million square miles of the Earth's surface were covered in ash anyone living in the Fallout faced starvation the tober ash fall would have affected the vegetation in a big way in India and the immediate effect of that would be this the game that humans relied on didn't have any vegetation to eat and then of course the human predators being at the top of the chain suffer much more the ash was deadly but volcanoes have an even deadlier weapon in their arsenal the gas sulfur dioxide towba may have released as much as 3 billion tons of it volcanologist bill mcguire has studied how sulphur dioxide can affect the entire planet when sulfur dioxide gets into the atmosphere which it does with a big volcanic eruption it combines with water vapor and it forms a fine mist of sulfuric acid billions of these tiny little sulfuric acid droplets in the atmosphere that act like tiny mirrors so they reflect solar radiation back into space the result the planet cools down and enters a volcanic winter [Music] there's some debate about how much of a temperature fool Toba actually led to but in the extreme case it would have reduced global temperatures by five to six degrees centigrade for a period of several years and that would have literally caused most of the worlds of vegetation to die off the effects of another super eruption today hardly bear thinking about starvation would wipe out huge numbers of people if we saw a super eruption today that resulted in that same temperature drop then we would experience global harvest fail you know I can't see any way that that can that cannot result in billions of deaths if another of Earth's active super volcanoes does what Tober did 74 thousand years ago it would be a disaster for us all but super-eruptions on average seemed to occur about every 50,000 years or so but of course yes doesn't operate to a timetable so when the next one's going to occur we really haven't a clue the Toba supervolcano affected vast numbers of people in India but 70,000 years ago the survivors faced a new threat this time one that would affect the whole planet a global big freeze you half a second to midnight on our clock of world history 21,000 years ago the planet was in the middle of an ice age throughout history ice sheets have helped form the story of the earth the biggest one was six hundred and fifty million years ago when the planet was virtually engulfed in ice and we had a lucky escape when volcanoes broke through it and warmed the planet again in the millions of years since that big one my sheets have frequently returned just as they will again one day in the future twenty-one thousand years ago earth was gripped by the most recent of these big freezes glaciers steadily advanced across the northern hemisphere for our ancestors there was no escape [Music] glaciations occur on a regular cycle caused by variations in Earth's movement through space sometimes earth moves further from the Sun so the planet cools and the ice caps expand the glaciers of the last ice age reached their farthest point south 21,000 years ago a period known as the last glacial maximum the last glacial maximum in in Europe was about as bad as it can get and that meant an ice cap three miles thick which covered half of Britain and around that ice cap to the south was a polar desert which didn't have ice on it but also didn't have much vegetation or people [Music] our ancestors it was migrate or perish they didn't return until the big Thor began around 7,000 years later and when the glacier has retreated it changed everything [Music] released from the grip of the ice civilization was finally free to begin agriculture cities the Industrial Revolution banks you get the picture the end of the Ice Age made it all possible but the irony is our civilization is now so complex that we'd be helpless if the glacier is advanced again and if there's one thing that's certain it's the one day the ice will return even now Earth's orbit is taking it further from the Sun another glacial advance is due any time the return of the ice would be a brutal shock in 1998 we got a glimpse of just how brutal [Music] a nice storm hit the city of Montreal freak weather conditions created a relentless buildup of ice 1,000 electricity pylons collapsed under its weight the power supply failed millions of inhabitants were left without heating and the temperature continued to fall the Montreal ice storm exposed our society's Achilles heel our reliance on near-perfect conditions if the glaciers were to advance once again there's not much we could do to protect ourselves inevitably a new Ice Age if it occurred very rapidly would lead to complete social and economic breakdown people would move towards equator from northern countries like the United States the UK Europe that would be a recipe for for war and conflict without any doubt the civilization that makes our lives so comfortable also makes us vulnerable but 13,000 years ago that's less than a second to midnight on our clock our Stone Age ancestors were luckier they had simply migrated south and survived off the land humans had now made it through a super-eruption and an ice age the risk of lightning striking a third time seems remote sadly it wasn't the planet had done its worst but there was still space to be reckoned with asteroids have struck earth throughout history in the ancient past they even caused mass extinctions and scientists are now beginning to wonder if humans could also have been affected by a cosmic catastrophe this is Ohio in the USA this is the site of a major catastrophe something happened which had a profound effect on the life of the times archaeologist Ken Tankersley believes that at the end of the last ice age 13,000 years ago this region suffered a catastrophe that originated in space these days most of Ohio is farmland but one small area of marsh remains it's just as it was thirteen thousand years ago except for these back then the area was home to an impressive collection of beasts there were mega mammals roaming this area which included mammoths and mastodons [Music] these mega mammals were food for the continents top predators humans the people who lived here we refer to as Clovis they were Stone Age hunter gatherers they were hunting wild game and gathering wild plant foods and living in extended families these people had successfully adapted to the landscape for thousands of years and then came a catastrophe the mega mammals went extinct their livelihood was gone forever clues to the cause of this catastrophe my 10 meters below ground this is Sheridan cave it's a natural time capsule its secrets might solve the mystery of the missing mega mammals tankers live work in the cave has unearthed a treasure trove of archaeological remains all of them dating to the time of the disaster it's a long descent down to the bottom of the cave and a journey back in time recent excavation has revealed a dull red layer which marks the exact moment that the mega mammals vanished from the fossil record it's known as the Clovis layer we're looking at the Clovis layer it's a very distinct layer here in the cave beneath it we have mega mammal remains above the layer there are no more mega mammals this literally represents the extinction event and you can find the same thing at more than twenty other sites across America the sediment layer marks the exact moment the mega mammals disappeared one of the things that intrigues me about this time period and about this site is we have no clear-cut answer as to what caused the extinction of these mega mammals overhunting people killing these animals just does not fit and when we look at all the other ice ages which came to an end these mega mammals did not go extinct so why now and why here this is one of the most intriguing questions that I've ever faced excavation here continues even after a decade they're still digging up bones even though this bone looks fresh is actually thirteen thousand years old it dates to the extinction event and it suggests a violent death what's really exciting about this particular specimen is there's clear evidence of burning literally a blackened color this is the tibia of a now extinct pig-like creature the size of a modern-day wild boar in order to burn the flesh off of an animal the size of a European wild boar we're talking about temperatures between 300 and 600 degrees centigrade this is not an animal that was subjected to a cooking fire this animal was incinerated and so was the entire landscape we're talking about a massive fire almost an explosion of heat and pressure the question is why you it's nearly midnight on our clock of the Earth's history 13,000 years ago a disaster struck America the mega mammals were wiped out and the people who hunted them lost their main food source the cause of this disaster has long been a mystery but deep in these Ohio caves archaeologist Ken Tankersley has discovered something which might provide the answer this is a meter which measures the magnetism the amount of iron the higher the iron content the greater the magnetic susceptibility of this layer I'll first put the probe in this gray area below the clovis layer is a perfect spot and we check the magnetism we see that it has a magnetism of eight now what we're going to do is compare that with the layer above it the reading is 50 times the iron content in other words the magnetic susceptibility is 50 times higher than the area that's gray a basic experiment reveals just how rich in iron the clovis layer really is a magnet dragged across the surface is left covered with iron particles it's a simple test with an astonishing implication it suggests this region was hit by an asteroid this suggests that there was some type of catastrophic explosion one which not only deposited meteoric iron but one that was also intense in temperature and pressure an asteroid strike meant North America's mega mammals were doomed they couldn't adapt to the challenging conditions that followed the disaster but humans could and the survivors flourished it's a controversial theory but it wouldn't be the first time that death had come from space scientists believe that 65 million years ago an asteroid wiped out the dinosaurs leaving behind a giant crater the trouble is for the Clovis event no crater exists but one man has a theory which might explain why there isn't one planetary geologist Peter Schultz has come to this NASA Research Center in California to conduct an experiment with this giant gun [Music] it's so powerful it can fire projectiles at over 15 times the speed of sound this is one of the big guns the fastest gun in the West this is where we have a chance to actually fire small bullets small bb's at very high speed shoots and his team will be firing the gun to find out if an object from space could strike the earth without leaving a crater Schultz is testing a theory that glaciers could have protected the Earth's surface during the Clovis era much of North America was covered by a vast ice sheet up to a mile thick a remnant of the last big freeze shoots hopes a scale experiment will show whether glaciers could have prevented an asteroid from leaving a crater in the underlying rock the question we really want to address is will the ice actually protect the earth below this is our projectile it's just an eighth of an inch about three millimeters or so and we're gonna be firing this at a speed of about five kilometers per second the team prepares the gun for firing a number of ultra high speed cameras will film the impact for later analysis inside the impact chamber Schultz prepares the target the red sand represents the surface of the earth add some color at least to the surface layer and this way we can tell whether or not we punch it through the surface or not so we have loose sand underneath that we have the red layer on top we're going to do one experiment when we slam just into this target like we have it and the other one where we put a thin layer of ice and the idea behind that is with them off this ice will act as a flak jacket now we just have to go ahead let's see what happens the gun is raised into the firing position and the countdown begins the team waits in a sealed bunker well away from the gun itself Wow now that that did some damage so this is big so forget it I'm going to slow this up now and take a look at the slow-mo Kapow so this is now the entire impact with the streak through and the impact stuff that's going downrange of extremely high speed that cares away and we have the crater forming and now the critter just grows and grows and grows and grows and keeps growing high-speed footage shows the devastating impact on the exposed sand surface but the best evidence is inside the impact chamber itself so this this impact was it was a good sized impact this was hyper velocity has slammed in it excavated stuff from below we scaled this up to a big crater on the earth it would last for millions of years so the next stage is to repair this target make it look like it was before we have the impact but this time let's put down a slab of ice kind of resembling what might have been on the earth when there were glaciers now we have the ice on top of the target and what we want to know is whether or not this ice actually buffers or protects the underlying target from the impact suite and we see that the vapor expands and we're seeing a little bit of ice come out and the ice clears away and the real question for the extras to see if it's without me reproduce the Creator right now I don't see a critter oh man that's remarkable the ice was here and it really protected the target underneath and that's just simply loose and so with time these pieces disappear they melt away it only has it has a tiny little crater and if this were the earth it could be a really easily eroded away and so when that ice disappears there's just nothing left it's the perfect crime it's only a scale model but it shows an ice sheet could have masked the evidence of a powerful impact 13,000 years ago maybe the mega mammals were wiped out by a cosmic catastrophe one day we may face a similar disaster advanced warning will be essential for our survival something astronomers in Arizona are working to provide this is Mount Lemmon station part of the Steward Observatory here asteroid hunter ed be sure cone space for near-earth objects any OS there are millions out there right now and not surprisingly governments worldwide consider them a real threat well the earth traveling around the Sun is much like a race car traveling around a circular track and a neo collision might be very much like a car coming suddenly out of the pits in front of the race cars representing an immediate impact threat and of course the consequences of a collision would be devastating each night the Shaw's team photographed the skies searching for anything that moves hey Andre have a look at this yeah it's quite bright its 19th magnitude and it's got a Digest score of a hundred let's check if it is norm yeah there's no ID on this this object isn't there the team have found an nao it's painstaking but vital work we take four images over it's pasted over about 45 minutes about ten minutes apart so here you see four images being shown in sequence our computers register the images so that the stars don't move but any object which is moving on the sky is revealed like you see the object here fortunately this near-earth object is probably harmless this object is in fact what's called a virtual impactor which means that there is a small very small probability that there might be an impact in the future it's big but luckily it poses little risk but for every large object in space there are many thousands of smaller ones and they can pose a real threat of asteroids are like gravel if you pick up a handful of gravel you're gonna find that there's a few large objects in there but there's a whole lot more smaller objects and it may be these smaller objects that in fact might be on a collision course with the earth and you don't have to look far to see what even a small asteroid can do this is meteor crater in Arizona 50000 years ago this impact devastated hundreds of square miles and the asteroid that did it was just 50 metres across but if you think 50 metres is small check this out this is the aftermath of a large explosion in the remote Tunguska region of Siberia in 1908 fallen trees fanned out from a central blast point for hundreds of miles there could be only one cause an asteroid exploding with the power of a nuclear bomb and it's estimated size just 10 meters across [Music] Tunguska is the only hard evidence we have of a recent impact on planet Earth so we can look at that and say that's pretty scary if that was a city underneath there it would be completely obliterated and it's quite interesting that if you look at the area that was destroyed and superimpose it on London for example virtually the entire area of Greater London would be wiped out this catastrophe shows just how vulnerable we are Tunguska sized projectiles strike earth roughly once a century the last one was a hundred years ago another deadly asteroid could turn up any day the history of our planet is an endless cycle of extinction and rebirth so it should come as no surprise that we humans are as vulnerable as our predecessors who are long extinct we've suffered disasters but not on a global scale if we had we wouldn't be here at all it's not that we've been lucky it's just that we haven't been unlucky yet you can find out more about how the evolution of life on Earth has been shaped by catastrophe at channel 4 comm slash science tomorrow at 9 another couple need cash flow to save their family heritage a country-house rescue from the Scottish Borders the next tonight a father Ted Christmas you
