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Mega Disasters Volcanic Winter Decimates Civilization (S3, E5)
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00:00The biggest volcanic eruption of the past 2 million years.
00:06It would have been the mother of all explosions.
00:1175,000 years ago, the supervolcano Toba
00:14threw the planet into climatic chaos.
00:17There was this huge climate effect
00:19that made it so devastating around the world,
00:21not just where the volcano erupted.
00:25Temperatures across the planet dropped.
00:27The world entered into a volcanic winter,
00:30and the human race was pushed to the brink of extinction.
00:34For a person living after this eruption,
00:38really only the strong would have survived.
00:40Could one eruption have caused such apocalyptic destruction?
00:44And what will happen if and when this type of mega disaster
00:48happens again?
01:0673,000 BC, Sumatra, Indonesia.
01:10A sleeping giant named Toba awakens from a 700,000-year slumber.
01:19It unleashes the most explosive volcanic eruption
01:22of the past 2 million years.
01:25It would have been the mother of all explosions.
01:28People could hear it from thousands of kilometers away.
01:32Toba was 40 times larger than the largest eruption in recorded history.
01:36And it probably had 40 times the impact.
01:39And that was disastrous.
01:423,000 times more powerful than Mount St. Helens,
01:46Toba sends volcanic debris flying through the air at speeds of up to 60 miles an hour.
01:52Everything within 500 miles is doomed.
01:56It's a very violent, fast process.
01:59Anything in that area, any form of life would have been annihilated.
02:05The eruption continues for an entire week.
02:09Toba blasts 2,800 cubic kilometers of sizzling magma 30 miles into the atmosphere.
02:16You know the Beltway around Washington, D.C.?
02:18It's about 60 miles around.
02:20If we wanted to fill that up with all this rock and ash,
02:23it would make a disk a mile high, covering the inside of the Beltway.
02:29The ash spreads for more than 2,000 miles
02:33and buries everything in its path in up to 20 feet of debris.
02:38The dust seems to have traveled about two-thirds of the way across the Indian Ocean
02:42to the west and as far as almost to Taiwan on the east.
02:48The ash begins to block the sun.
02:52You were completely isolated from the sun.
02:55You didn't know whether the sun was up or not
02:56because there was this very thick cloud of ash in the atmosphere.
03:03With a typical volcano like Mount St. Helens, the effects are felt locally.
03:08The initial eruption and the ash it releases are what caused the destruction.
03:13But Toba also releases something more deadly.
03:17Massive amounts of invisible sulfur gases.
03:21These gases reach the uppermost layer of the atmosphere,
03:25which enables them to travel around the world,
03:28setting the stage for this one volcanic eruption to unleash a global catastrophe.
03:33The amount of sulfur dioxide that comes out of the volcano
03:37is very important in terms of its impacts.
03:39If it's a relatively small amount,
03:41it's the kind of thing that the Earth system can deal with and absorb.
03:44But if it's a huge amount, then you're talking about major problems.
03:50Major problems like instantaneous and drastic temperature changes.
03:55These sulfur gases converted into particles.
03:58We call them sulfuric acid aerosols.
04:00And these cloud of particles was blown around the world by the wind
04:03and stayed there for several years,
04:05blocking out the sun and making it cold and dark at the Earth's surface.
04:11The sulfate particles that are in the stratosphere
04:14act as a kind of a sunshade to reflect sunlight away from the Earth
04:18and cause cooling.
04:19With the Earth's rays being deflected back to space,
04:23global temperatures plummet by as much as 25 degrees Fahrenheit.
04:28The entire planet spirals into perpetual winter.
04:32It was this huge climate effect that made it so devastating around the world,
04:36not just where the volcano erupted.
04:39Toba has unleashed a worldwide catastrophe,
04:42a phenomenon scientists call a volcanic winter.
04:47A volcanic winter has got such extreme cooling,
04:51it goes throughout the entire year
04:52and can go on for several years or decades, potentially.
04:56Toba's volcanic winter will be more severe than a nuclear winter
05:00produced by 20,000 atomic weapons.
05:04The drop in temperature quickly turns lush rainforests into dry wastelands
05:09and arid deserts into frozen tundras.
05:14You can imagine a place like Nairobi,
05:17snow and frosts throughout most of the year.
05:26Vegetation, unable to adapt to the sudden shift,
05:29quickly dries up or freezes.
05:32Animals who can't find enough nourishment to sustain themselves,
05:36perish.
05:38With the food chain crumbling,
05:40prehistoric humans who rely on hunting and gathering begin to die.
05:45You're sort of living on the edge anyway.
05:47You don't have a way to store food.
05:48You don't have a supermarket when you run out of milk.
05:50You're working with your environment,
05:52and if the balance goes haywire
05:54and the normal food supplies disappear or die,
05:59then what do you do?
06:00You're in trouble.
06:03At the time of Toba's eruption,
06:05there may have been as few as 1 million people
06:08inhabiting the planet in parts of Africa and Asia.
06:11There were at least two kinds of people alive
06:15at the time of the Toba eruption.
06:18There were people who looked under the skin
06:20very much like everybody else alive today,
06:23and we call them anatomically modern humans.
06:26In Western Eurasia,
06:27there were people who we call Neanderthals.
06:30But as the planet slips deeper
06:32into several years of volcanic winter
06:35and temperatures plummet,
06:36they begin to succumb to starvation and disease.
06:40So there would have been generations
06:41of people who had lived in a relatively warm global climate
06:46for 50,000 years,
06:48suddenly plunged into an ice age in just a few years.
06:53And the cataclysmic impact on human beings
06:5675,000 years ago may have had a permanent effect
07:00on every human being today.
07:03If you look at the genetic diversity of people,
07:05it's surprisingly small,
07:07which basically implies that at some point in the time,
07:10the population just crashed.
07:13Maybe our population,
07:15our species nearly got wiped out
07:17by the eruption of Mount Toba.
07:19The global storm set off by Toba
07:23may have crippled the planet
07:24and pushed humans to the brink of extinction.
07:27But how do we know that this apocalyptic event
07:30happened 75,000 years ago?
07:33Could a single volcanic eruption
07:36have unleashed a worldwide catastrophe
07:38that caused temperatures to plummet
07:40and early humans to be nearly wiped out?
07:46For thousands of years,
07:48all evidence of this ancient storm remained hidden.
07:52But in the early 1990s,
07:55a hint of this prehistoric megadisaster
07:57would be unearthed at the very bottom of the ocean.
08:02While digging for sediment,
08:04scientists make an astounding discovery.
08:07Scientists can reconstruct
08:09what the temperature of the ocean was like in the past.
08:13It works amazingly well
08:14and with tremendous accuracy
08:15by looking at different kinds of sediments
08:18pulled out from the bottom of the ocean.
08:22When scientists analyze the ocean cores
08:25from about 75,000 years ago,
08:28they notice something unusual.
08:30For some reason,
08:31ocean temperatures drop by 10 degrees Fahrenheit.
08:36Generally speaking,
08:37the ocean's temperature will often be fairly steady
08:40over 100,000 years or more.
08:42But every once in a while
08:44when the scientists look through
08:45these old core samples,
08:47they will see some indication
08:49of a very abrupt change.
08:51When that shows up,
08:53it's an important clue
08:54that something must have happened
08:56to change the amount of heat
08:59that was suddenly coming
09:00into the Earth's environment at that time.
09:03A 10-degree drop is a sign
09:05of a huge impact on the world.
09:07But what could have caused
09:09such a big drop in ocean temperature?
09:13In terms of natural disasters,
09:15there are only two that we know of
09:17that would have such a devastating effect.
09:19One is a super volcanic eruption,
09:21and the other is an asteroid
09:22smashing into the Earth.
09:25But there's no evidence
09:27that an asteroid crashed into the Earth
09:2975,000 years ago.
09:31There's only one event
09:33that might fit the bill.
09:36The eruption of a supervolcano.
09:41Supervolcanoes are characterized
09:43as volcanoes that erupt
09:45over 1,000 cubic kilometers of magma.
09:48They're basically humongous eruptions.
09:51Anything that we've seen
09:52in historical times
09:53doesn't even compare.
09:55Vesuvius wiping out Pompeii
09:57in AD 79, nothing.
10:00Tambora erupting in 1815,
10:03nothing at all.
10:05Supervolcanoes can drive
10:07catastrophic climate change globally.
10:09These are a whole order
10:10of magnitude larger.
10:13For tens of thousands
10:15of years at a time,
10:16the world's handful
10:17of supervolcanoes lies dormant.
10:20But beneath their seemingly
10:21peaceful exterior,
10:23they're building up
10:24a vast arsenal
10:25of deadly magma and gases.
10:29But where is
10:30the cataclysmic volcano
10:31that exploded 75,000 years ago
10:34in this apocalyptic eruption?
10:37On the island of Sumatra
10:39in Indonesia
10:40is Lake Toba.
10:43This lake is 60 miles long,
10:4620 miles wide
10:47and over a mile deep.
10:49It is so massive
10:51it can be seen from space.
10:54The lake, it turns out,
10:55is no ordinary body of water.
10:57It is the biggest volcanic crater
11:00in the world.
11:03Scientists discovered
11:04this lake's secret
11:05when they uncovered
11:06massive amounts
11:07of volcanic debris
11:08at the bottom of the lake
11:10and for miles around its shore.
11:12There are several lines
11:14of evidence
11:14that tell us
11:15that Toba erupted
11:1775,000 years ago
11:19in this cataclysmic eruption.
11:21The thick deposits
11:23of ignimbrite pumice
11:26and ash
11:27that are found
11:28for 20,000 square kilometers
11:31around Lake Toba.
11:33Are the remnants Toba
11:35left behind
11:36enough to prove
11:37that it unleashed
11:38a volcanic winter
11:40that crippled the planet?
11:43And could this type
11:45of catastrophe happen today?
11:47As scientists search for clues,
11:50they start to piece together
11:52a picture of apocalyptic change
11:54and one of the largest storms
11:57the world has ever seen.
12:0675,000 years ago
12:08on the Indonesian island
12:10of Sumatra,
12:11a supervolcano
12:12named Toba
12:13violently erupts.
12:18Toba would have been
12:19such an enormous event
12:21and that was the largest eruption
12:22of the last 2 million years.
12:24With a supervolcano,
12:26you see the potential
12:28really to affect
12:28the entire world
12:30and that's rare
12:31with natural disasters.
12:32Most of them affect
12:33a localized area.
12:35With the supereruption,
12:36it really can affect
12:38world weather.
12:43Toba sets off
12:44a worldwide storm
12:46that will block out the sun,
12:48throw the global climate
12:49into chaos,
12:50and bring the human race
12:52to the brink of extinction.
12:54The sun was just not
12:55warming the world.
12:56Within a few days
12:57to a few weeks,
12:59people would have started
13:00to feel the effects
13:01of the cold.
13:02The plants would have
13:03started dying.
13:05And then the animals
13:06and the people
13:07that feed off of those plants
13:08would have started dying as well.
13:10But how could one eruption
13:11have had such an apocalyptic impact
13:14on the entire planet?
13:17A supervolcano, it seems,
13:19carries the trigger
13:20for worldwide destruction.
13:22A regular volcano
13:24is really a pipe of magma
13:25running up from the mantle.
13:28But with a supervolcano,
13:30you see this huge reservoir
13:32of magma sitting right
13:34below the crust
13:35that actually dimples
13:36the earth above it.
13:37The pressure beneath
13:38the earth grows
13:39as the magma chamber fills.
13:42And when a supervolcano
13:43like Toba erupts,
13:44it doesn't just send magma
13:46through a single vertical vent
13:48like a normal volcano.
13:49It explodes in every direction,
13:52sending destructive gases
13:53into the uppermost layers
13:55of the atmosphere.
13:56In its wake,
13:58Toba leaves behind
13:59a unique footprint,
14:01a gigantic volcanic crater
14:03called a caldera.
14:04Toba collapsed
14:05and formed this huge hole
14:07in the ground
14:07that is there.
14:09It wasn't there before
14:10because all that stuff
14:10is now in the atmosphere.
14:14But what kind of evidence
14:16could the supervolcano
14:18have left behind?
14:20Scientists need to determine
14:21just how destructive
14:22all of the ash and gas
14:24would have been on the planet.
14:26In the early 1990s,
14:29sediment from 75,000 years ago
14:31reveals that there is
14:32a dramatic drop
14:33in ocean temperatures.
14:36But if this is a sign
14:38of a catastrophic event,
14:39where is the evidence on land?
14:42What happened
14:43to air temperatures?
14:46Scientists finally discover
14:48the clue they need
14:49more than 7,000 miles
14:50from Sumatra,
14:52buried deep within
14:53the ice sheets of Greenland.
14:54Ice cores are important
14:56for studying how climate change
14:58is because they can give
15:00a record of what was happening
15:02in the atmosphere
15:03year by year
15:04as the snow falls.
15:06It's basically collecting
15:08everything that's in the atmosphere
15:09at that time.
15:10The ice cores are
15:12a virtual database
15:13of the weather on Earth.
15:14With each year that passes,
15:16a layer of ice forms.
15:18That layer preserves
15:20the annual climatic patterns.
15:22When you look
15:23at the individual years
15:24available in the ice core,
15:26it's very similar
15:27to a tree ring.
15:29You can count each year
15:30because there are
15:31different characteristics
15:32that happen.
15:34It's a very detailed record
15:36of the climate
15:37of the last 125,000 years.
15:40Over two miles of ice
15:42has accumulated
15:43in that time.
15:44And so it's justifiably
15:45called the two-mile time machine.
15:47Could evidence
15:48of this global disaster
15:50be locked within
15:51these ice sheets?
15:54When climatologist
15:56Greg Zielinski
15:57and his team
15:57begin to analyze
15:58the ice cores
15:59from 75,000 years ago,
16:02they find some astonishing data,
16:04something that they've
16:05never seen before.
16:07We found that there
16:09was this very, very large
16:11increase in the sulfate.
16:14Sulfate is a signature
16:15of volcanic eruptions.
16:17When volcanoes erupt,
16:19they emit sulfur gases
16:20along with ash and rock.
16:22Small sulfate peaks
16:24in the ice usually indicate
16:25a typical volcanic eruption
16:27somewhere in the world.
16:28But the sulfate levels
16:30Zielinski finds
16:31from 75,000 years ago
16:33are simply off the charts.
16:36There's like three orders
16:37of magnitude greater
16:39than anything else
16:40we had seen.
16:41Really a fantastic discovery.
16:43We've never seen anything
16:45that really perturbed
16:47the atmosphere
16:47to this extent.
16:49Levels of sulfate
16:50this extreme
16:51can only mean one thing.
16:54A super volcano.
16:56We were very aware
16:57that back around
16:5975,000 years ago
17:00was this huge
17:01tobo eruption,
17:02so our first thought
17:04was that could easily
17:05be the tobo eruption.
17:09During a typical
17:10volcanic eruption,
17:11when sulfur is released
17:13into the air,
17:13it only has enough
17:15explosive energy
17:16behind it
17:16to make it into
17:17the lower layer
17:18of the atmosphere,
17:19called the troposphere.
17:21There, it will form
17:22acid rain.
17:24But the effects
17:25of acid rain
17:26are localized
17:27and temporary,
17:28and the sulfuric acid
17:30falls out of the atmosphere
17:31in a matter of weeks.
17:34But if the volcano
17:36is massive enough,
17:37the sulfur gases
17:38will travel 15 miles
17:40into the uppermost layer
17:41of the atmosphere,
17:43called the stratosphere.
17:44There, they will make
17:46their way around the globe
17:47and take on
17:48a whole new level
17:49of destruction.
17:50They can unleash
17:52a volcanic winter.
17:53It's a really
17:54explosive volcano.
17:56That sulfur dioxide
17:57goes up into
17:58the stratosphere
17:58and it causes
17:59these sulfur particles
18:00that reflect
18:01the sun's heat away
18:02and that causes cooling.
18:07Scientists have seen
18:08the effects
18:09of this sulfur dioxide
18:10in recent history.
18:12In 1815,
18:13the eruption
18:15of Mount Tambora
18:16in Indonesia
18:17killed more than
18:1810,000 people
18:19and caused
18:20a year-long
18:21volcanic winter
18:22that we now call
18:23the year without a summer.
18:26The Mount Tambora
18:27eruption sent
18:28400 million tons
18:30of sulfur dioxide
18:30into the atmosphere.
18:33In the next summer
18:34in 1816,
18:36in June,
18:38snow fell
18:39in New England,
18:41harvest failed
18:42in America
18:43and Europe.
18:44Agricultural production
18:45crashed.
18:46A bushel of wheat
18:47suddenly went through
18:48the roof
18:49and went up to $2.50,
18:50which wasn't reached again
18:51until 1972.
18:53Hundreds of thousands
18:53of people died
18:54from starvation
18:55and you saw
18:56an incipient outbreak
18:58of cholera
18:59actually widen
19:00into a world epidemic
19:02simply because
19:03of this one eruption.
19:05The drastic climate change
19:07would make an impact
19:08on works of literature
19:09as well.
19:10Author Mary Shelley
19:12is so captivated
19:13by these sudden
19:14and extreme changes
19:15in climate,
19:16she produces
19:17her masterpiece,
19:18an iconic horror story
19:20during the summer
19:21of 1816.
19:23She wrote
19:24Frankenstein,
19:25inspired by the climatic effects
19:27of a volcanic eruption.
19:28At the beginning
19:29of the book,
19:30the monster is climbing
19:31over the ice.
19:32These cold, icy images
19:34were inspired
19:35by the weather outside.
19:37They didn't know
19:38it was caused
19:38by a volcanic eruption.
19:39They just knew
19:39how cold and gloomy
19:40that was.
19:41But as devastating
19:43as Tambora's eruption
19:44is on the planet,
19:46it would have paled
19:47in comparison
19:48to the volcanic winter
19:49unleashed by Toba.
19:51Tambora was probably
19:52at least 10 times
19:54smaller than Toba.
19:55If an eruption
19:56the size of Tambora
19:58caused the year
19:58without a summer,
20:00then Toba could have
20:01easily caused
20:02the decade
20:03without a summer.
20:09After Toba erupted
20:10and these aerosols
20:12were up there
20:12for 6 to maybe 15 years,
20:15during that time
20:15you certainly
20:16would have seen
20:17much cooler conditions
20:18on the Earth's surface.
20:20A prolonged
20:21volcanic winter
20:22would have catastrophic
20:23effects on any ecosystem
20:25and could send
20:26the global climatic balance
20:28into chaos.
20:30Potentially what could
20:31have happened
20:31following that
20:32is that you start
20:33cooling major parts
20:35of the Earth's surface
20:35and especially the oceans,
20:37the sea surface temperatures.
20:39As sea surface
20:40temperatures drop
20:41ice begins to expand
20:43and with the ice growth
20:45comes continually
20:47lower temperatures
20:48and drought.
20:50Suddenly early humans
20:52are seeing temperatures
20:53plummet by as much
20:55as 25 degrees Fahrenheit.
20:5725 degrees Fahrenheit,
20:59that means the whole world
21:00was below freezing.
21:01Once that cooling
21:03starts taking place globally
21:04you start to see
21:05the ice expand
21:06both on the ocean
21:07and on land
21:08and once you have
21:09that kind of cooling effect
21:10could start off,
21:12kick off a process
21:13that's a self-reinforcing cycle
21:14that could cause
21:15more cooling.
21:17Could this storm
21:18have impacted the planet
21:19so severely
21:20that it permanently
21:21changed the global climate?
21:24Did the world's worst
21:25volcanic winter
21:26send the planet spiraling
21:28into an ice age?
21:29The world wasn't ready
21:30for an ice age
21:31but it was pushed into one.
21:38When the supervolcano Toba erupts
21:41on the Indonesian island of Sumatra
21:43it unleashes a worldwide catastrophe.
21:47The planet is plunged
21:49into several years
21:50of perpetual winter.
21:52Animals and humans
21:53are pushed to the edge
21:54of extinction.
21:56The volcanic winter
21:57from Toba
21:58is the worst that we know of
21:59in the last 100,000 years.
22:00It has huge implications
22:02for how you can survive.
22:04You can't put enough
22:05food resources away
22:06to survive.
22:07Very hard to plan
22:08for those of the big events.
22:11But after several years
22:13of volcanic winter
22:14the debris
22:15and lethal gases
22:16released by Toba
22:17finally begin to fall out
22:19of the atmosphere.
22:20The sun once again
22:22returns to the horizon
22:23but the frigid temperatures
22:25gripping the earth
22:26do not retreat.
22:27In fact
22:28geological records
22:30extracted from the ice cores
22:32in Greenland
22:32show that shortly
22:34after Toba's volcanic winter
22:35comes to a close
22:36the world plunged
22:38into a new climatic state
22:40a 1,000 year ice age.
22:48Pretty soon after Toba
22:49for the next 1,000 years
22:51ice sheets began
22:51to build up
22:52over North America
22:54and over Europe.
22:55And so people have suggested
22:57maybe Toba caused
22:59an ice age
23:00because it occurred
23:01right when this ice advance
23:02took place.
23:04Could the mega disaster
23:06triggered by Toba
23:07have unleashed
23:08a worldwide climate shift?
23:13When global temperatures
23:15drop by just a few degrees Celsius
23:17there can be
23:18quite a few effects
23:20around the planet.
23:21Glaciers that are retreating
23:23could advance instead.
23:25An ice age
23:26is when the earth's
23:27temperatures decrease
23:28for an extended period of time.
23:30The global temperature
23:32is about 9 degrees Fahrenheit
23:33colder than normal.
23:35This temperature change
23:36can result in the expansion
23:37of ice sheets
23:38over entire continents.
23:40An ice age
23:41has the effect
23:42of capturing more
23:43and more water
23:44in big sheets of ice
23:46that then start
23:46to extend out
23:47as big glaciers
23:48and ice sheets
23:49across the land.
23:52A destructive cycle
23:54takes over.
23:55As ice sheets expand
23:56and sea levels go down
23:58sunlight is reflected
24:00back into space
24:01and temperatures
24:02continue to drop.
24:03And what happens
24:04when you get an expansion
24:05of snow and ice
24:06is you make the earth
24:07whiter and more reflective
24:08so it reflects away
24:10more of the sun's heat
24:11which will cause it
24:12to get even colder.
24:14Could a single
24:15volcanic eruption
24:16have triggered
24:17an ice age?
24:21The timing
24:22of the Toba eruption
24:23with the development
24:24of ice sheets
24:25on the continents
24:26seemed to coincide
24:28very well.
24:29At the time
24:30Toba erupted
24:31it looks like
24:33we were starting
24:33to see the development
24:35of large ice sheets
24:36on the continents
24:37and so that leads
24:38to the question
24:39that did Toba
24:40actually cause
24:41a glacial period?
24:50Meteorologist
24:50Alan Roebach
24:51has created
24:52computer models
24:53to measure
24:53the potential
24:54climate effects
24:55unleashed by volcanoes.
24:58What we can do
24:59is we can use
24:59climate models.
25:00We can calculate
25:01how much the temperature
25:02would change.
25:05We use them
25:06to forecast the weather
25:07every day.
25:08But there is
25:09no concrete weather data
25:10from 75,000 years ago.
25:13In order to simulate
25:15the impact
25:15of a volcanic winter
25:16like Toba's
25:17on the planet
25:18and determine
25:19whether it triggered
25:20an ice age
25:21Roebach has to draw
25:23upon the closest
25:23modern counterpart.
25:31The 1991 Mount
25:33Pinatubo eruption
25:34in the Philippines.
25:36The most destructive
25:37explosion
25:38of the last 100 years.
25:41Pinatubo was
25:42the largest eruption
25:43of the 20th century
25:45in terms of the amount
25:46of sulfur it put
25:46in the atmosphere.
25:48When Mount Pinatubo erupted,
25:50this sulfuric acid haze
25:51caused a significant decline
25:53in the amount of sunlight
25:55hitting the Earth
25:55and it stopped global warming
25:57for a year.
25:58Using modern
25:59satellite technology,
26:01scientists are able
26:02to gather data
26:03about the amount
26:04of sulfuric acid
26:05that Pinatubo releases
26:07into the atmosphere.
26:08We can then go
26:10to see how much
26:11ended up falling out
26:12in Greenland.
26:13We didn't have satellites
26:14for in Toba.
26:15We know how much
26:16fell in in Greenland
26:17because we have the,
26:18it's been preserved
26:19there for us.
26:19We can just look
26:20at how much there is
26:21compared to Pinatubo.
26:22And it was about
26:23100 to 300 times more
26:24than Pinatubo.
26:26Knowing how much
26:27sulfur dioxide
26:28Pinatubo put
26:29into the atmosphere
26:30and knowing that Toba
26:31is at least 100 times
26:33bigger than Pinatubo,
26:35Roebach can use
26:36computer models
26:37to determine
26:37what may have happened
26:3975,000 years ago.
26:41So we will do something
26:43like put 100 times
26:44Pinatubo,
26:45put 100 times
26:46the amount of sulfur
26:47that Pinatubo generated
26:48and calculate
26:49the climate response
26:50and just see
26:50how cool it would get.
26:51This graph shows
26:53that it would get
26:5515 degrees Celsius,
26:56almost 30 degrees Fahrenheit,
26:58colder than normal
26:59for several years.
27:00So this would be
27:01a global winter
27:03and also a drop.
27:05But did this extreme
27:07temperature drop
27:08this volcanic winter
27:09then cause an ice age
27:11to begin?
27:12In order for it
27:13to form an ice age,
27:14it would have to cool
27:15the earth for a long
27:16period of time.
27:16So we were trying
27:17to figure out
27:17how could Toba
27:20have caused the earth
27:21to cool for a long
27:22period of time.
27:23No matter how much
27:24it puts in the atmosphere,
27:25it's still going to fall out
27:26because of gravity.
27:27We can get a volcanic
27:28winter, we can make
27:30it very cold
27:31and very hard to live
27:32for several years,
27:34up to 10 years,
27:34but then it gradually
27:35starts to warm up.
27:37What Robach's models
27:39reveal is that
27:40this cooling effect
27:41from Toba's sulfur gases
27:42could not have lasted
27:44forever.
27:45After Toba's volcanic
27:47winter, the planet
27:48should have warmed up
27:49and temperature should
27:51have returned to normal.
27:52But geological records
27:54show that the earth
27:55stays cold
27:56for another 1,000 years.
27:58This leads Robach
28:00to believe that Toba
28:01erupts at a time
28:02when an ice age
28:03is already on its way.
28:05It could have brought it
28:06on a little bit faster.
28:07We know that ice ages
28:09occur without volcanic eruptions.
28:11We know that
28:12this large eruption
28:14occurred just before
28:15an ice advance.
28:17I believe what may have
28:18happened is that
28:19as the overall climate
28:21of the earth
28:22was starting to shift
28:23into one of these
28:241,000-year periods
28:24of cooling, Toba erupted.
28:26And I think
28:27those volcanic aerosols
28:28helped to cool
28:30sea surface temperatures.
28:31And what it did,
28:32it looks like it may have
28:33really enhanced
28:34that initial couple
28:35hundred years
28:36of cooling.
28:42Although Toba
28:43may not have been
28:44the trigger
28:45for a 1,000-year ice age,
28:47its aftermath
28:48could be responsible
28:49for something
28:50far more devastating,
28:52the near extinction
28:53of humanity.
28:54could Toba have nearly
28:56wiped out
28:57all human beings
28:58on the planet?
28:59The clues to this
29:00global disaster
29:01may be found
29:02within the DNA
29:04of each living person
29:05today.
29:13The storm that ravages
29:15the planet
29:16after the eruption
29:17of the supervolcano Toba
29:18is unlike anything
29:20the world has ever seen.
29:23It sets off
29:24a volcanic winter
29:25that causes temperatures
29:27to plummet
29:28by as much as 25 degrees
29:30and cripples
29:31the food chain.
29:32Plants and animals
29:34struggle to adapt
29:35to the frigid conditions.
29:37But it's early humans
29:38who face the greatest threat
29:40of all,
29:41the threat of extinction.
29:43Imagine you're sitting
29:44in front of your cave
29:45and all of a sudden
29:46in the distance
29:47the sky starts getting dark
29:48and the sun gets blocked out
29:50and it starts getting
29:51colder and colder
29:52and you say,
29:53what have I done
29:53to annoy the gods?
29:54What's happening?
29:59The people at this time
30:00really were suffering
30:02some serious climatic change,
30:05really cold conditions,
30:07unlike anything
30:08that they had experienced.
30:10It doesn't take long
30:11for disease, famine,
30:13and death to set in.
30:15For a person living
30:17after this eruption,
30:18really only the strong
30:19would have survived.
30:22As this cooling occurred,
30:25you can imagine populations
30:27would start to crash.
30:29We're talking about generations
30:30being decimated.
30:36From what scientists can tell,
30:39before the Toba eruption,
30:40a small but growing population
30:42of early humans
30:43inhabits Africa
30:44and possibly parts of Asia.
30:47There were people
30:48who looked under the skin
30:49very much like everybody else
30:51alive today.
30:53Their hunter-gatherer
30:54way of life
30:55means they depend
30:56on their local habitat
30:57and stable climate conditions
30:59to sustain themselves.
31:01But as the volcanic winter
31:03sets in
31:04and temperatures
31:05remain frighteningly low
31:06year after year,
31:08early humans
31:09struggle to survive.
31:10So you have to imagine
31:11a landscape populated
31:12by small groups
31:13of hunter-gatherers
31:14living at low population densities.
31:17And when this disaster struck,
31:18people who were not
31:20in the best environments
31:22would have been unable
31:24to feed themselves.
31:26The questions scientists
31:28have to answer
31:29so many thousands
31:30of years later are,
31:32how dramatic
31:33is the impact
31:34of this storm
31:34on these early humans?
31:36How many are able
31:37to survive?
31:39The answers, it seems,
31:41can be found
31:42inside all of us.
31:44The geneticists
31:45have ways
31:46of analyzing
31:47the modern populations
31:49to reconstruct
31:50the past population sizes.
31:52Today, scientists
31:54can determine
31:54every person's
31:55genetic heritage
31:56by mapping
31:57the human genome,
31:59which is made up of DNA.
32:01There's a part
32:02of the DNA
32:02that only is transmitted
32:04from females to females.
32:06It's called
32:07mitochondrial DNA.
32:08So it's a perfect
32:09marker of inheritance.
32:12By examining
32:13mitochondrial DNA,
32:14scientists are able
32:16to trace
32:16every single human being's
32:18genetics
32:18for thousands of years,
32:20and it tells
32:21an intriguing story.
32:23Despite millions
32:24of years of evolution,
32:26there is very little
32:27variation
32:28among the 6 billion
32:29people living
32:30on Earth today.
32:32Humans are very unusual
32:33in the world
32:34in their genetic composition
32:36compared to
32:37most other species.
32:39People as far apart
32:40as the Eskimos
32:41and the Australian
32:41Aborigines
32:42and the southern tip
32:43of Africa
32:44are genetically
32:45more similar
32:46to each other
32:46than two chimpanzees
32:49from the same
32:50social group
32:51in West Africa.
32:56What could cause
32:58such limited
32:58genetic diversity?
33:00As scientists
33:01analyze modern human
33:03beings' genetic history,
33:04they find a sudden
33:06decrease in the population
33:07about 70,000 years ago.
33:10There weren't
33:10very many different
33:11sources of these genes
33:13going back
33:13to that time period.
33:14It had to have been
33:16a massive catastrophe
33:17to cause such
33:18widespread death.
33:20Could Toba
33:21be the culprit?
33:22When the geneticists
33:23found out
33:24that there had been
33:24this huge
33:25environmental catastrophe
33:26at that time,
33:27then it made sense.
33:28The volcanic winter
33:29and its consequences
33:31for global climate
33:33and food supply
33:34caused the human
33:34population to crash.
33:37Anthropologist
33:38Stanley Ambrose
33:39has been studying
33:40the effects of Toba's
33:41aftermath on early
33:42human beings
33:43for more than a decade.
33:44He believes
33:46this prehistoric event
33:47caused such an abrupt
33:48drop in the human
33:49population,
33:50it changed the genetic
33:52destiny of humanity.
33:55Before Toba,
33:57there may have been
33:57a million people
33:58alive in Africa.
34:00But after Toba,
34:01scientists believe
34:02the entire human population
34:04crashed to as few
34:05as 30,000 people.
34:07In the aftermath
34:08of one storm,
34:10the world's population
34:11dropped from the number
34:12of people living in Detroit
34:13to the number of seats
34:15in Fenway Park.
34:16Geneticists have
34:17reconstructed a population
34:19size of about 5,000
34:21breeding age females.
34:22Everybody alive on Earth
34:24today can trace themselves
34:25back to one of these
34:27breeding age females.
34:29This rapid decrease
34:30in population
34:31is what scientists call
34:33a genetic bottleneck.
34:35A genetic bottleneck happens
34:37anytime something eliminates
34:39most members of a species
34:42so that any future generations
34:44are descended from a very small population.
34:47It's kind of like
34:49some sort of disaster happened
34:50and the only people left
34:52to repopulate the world
34:54were the ones in your neighborhood.
34:55As diverse as your neighborhood
34:57might be,
34:58it doesn't represent
34:59all the different kinds
35:00of traits that you would find.
35:02So certain kinds
35:03of genetic traits,
35:04maybe red hair,
35:06for example,
35:07would suddenly vanish
35:08from all subsequent generations.
35:10The genes that you see today
35:11really came from
35:12a small group
35:13of original ancestors
35:15and it's possible
35:17to tie this in
35:18to the Toba eruption
35:19that if it killed
35:20a huge enough subset
35:22of human ancestors
35:24that maybe it did just leave
35:25this small core
35:27of humans to survive
35:28and repopulate the Earth.
35:32And human beings
35:33are not the only species
35:34who experience a bottleneck
35:36during this relentless disaster.
35:38The groups of animals
35:40struggling to survive
35:41also show signs
35:43of their own dramatic shift
35:44in population.
35:46Chimpanzees in Africa,
35:48orangutans in Borneo
35:50seem to have gone through
35:52a population crash.
35:53Every tiger alive
35:55on Earth today
35:55can trace its maternal ancestry
35:58back to about 73,000 years ago.
36:01There's all kinds of things
36:02happening around the world
36:03at about this time
36:05that suggests that
36:06populations of many species
36:08underwent some dramatic changes.
36:12It seems that the Toba eruption
36:14and its aftermath
36:15don't just throw the planet
36:17into climatic chaos.
36:19They very likely killed
36:21the majority of life on Earth.
36:23These are the supervolcanoes
36:25who are almost like
36:25the doomsday scenario.
36:27We nearly got snuffed out
36:28by a supervolcano.
36:31The geneticists have shown
36:32that everybody alive on Earth today
36:34has an ancestry in Africa
36:37of less than 70,000 years ago.
36:39Where are all our missing genes?
36:42Our genes are missing
36:44because the people
36:45who carried them died out
36:46and all of the people alive on Earth
36:49come from a very small number
36:51of individuals
36:52that survived this disaster.
36:55A single volcanic eruption
36:57changes the course
36:59of human history.
37:01But what would happen
37:02if a supervolcano
37:03the size of Toba
37:05erupted today?
37:06Would it trigger
37:07another volcanic winter?
37:10And would the modern world
37:12be able to survive?
37:2275,000 years ago
37:24on the Indonesian island
37:25of Sumatra,
37:27the supervolcano Toba erupts,
37:29sending the entire planet
37:31into climatic chaos.
37:33It unleashes a volcanic winter
37:35that may have pushed the planet
37:37into a thousand-year ice age
37:39and brought human beings
37:40to the brink of extinction.
37:43But could this type
37:44of mega-disaster happen today?
37:47Is there another sleeping giant
37:50out there waiting to erupt
37:52and wreak havoc?
37:53And could our modern world
37:55and race survive?
37:57You can't stop volcanoes.
37:59Disasters of that scale
38:00are beyond human control.
38:05What could we do
38:07to prevent another
38:08volcanic winter?
38:09Well, nothing.
38:10You really can't.
38:11Nature has a way
38:12of doing what it wants.
38:13And really, humans
38:15just have to adapt
38:16to what nature
38:17throws at them.
38:19Today,
38:20the site where Toba erupted
38:21is showing signs
38:22of increased volatility.
38:26Workers are keeping
38:27a watchful eye
38:28on the seismic activity
38:29in the area.
38:33In the last million years,
38:35Toba has erupted
38:37four times.
38:38Could it erupt again?
38:39We believe there is magma
38:42still beneath Lake Toba.
38:43There are small volcanoes
38:45inside the Toba caldera,
38:47and there are hot springs
38:50in there.
38:51For the time being,
38:53Toba does not seem
38:54to be an imminent threat.
38:56But elsewhere around the globe,
38:58supervolcanoes are growing.
39:00From Italy to Japan
39:02to New Zealand,
39:03they erupted
39:04in prehistoric times,
39:06and they will erupt again.
39:08When that happens,
39:09they will trigger disasters
39:11that could cripple
39:12modern society.
39:13If an eruption
39:14the size of Toba
39:16erupted today or tomorrow,
39:18anywhere in the world,
39:19there's nothing you can do.
39:20Most people would die.
39:21It's hard to imagine
39:23people that would survive.
39:24If you had a fallout shelter
39:26with 10 years' worth of food
39:28and enough weapons
39:29to keep all the other
39:29hungry people out,
39:30you could probably live
39:32if you'd call that living.
39:33What most people
39:34don't realize is
39:36that some of the largest
39:37supervolcanoes in the world
39:38are actually forming
39:40in our very own backyard.
39:43There are regions
39:45in the western U.S.
39:46that have the potential
39:48for mega eruptions.
39:52In California,
39:54the Long Valley caldera
39:55sits just next
39:56to Mammoth Mountain,
39:57a popular ski resort.
39:59When Long Valley erupted
40:01750,000 years ago,
40:04its ash covered everything
40:06as far south as Texas
40:07and as far east as Nebraska.
40:12In northern New Mexico,
40:14the Valles caldera erupted
40:16more than 1 million years ago
40:18and devastated the land
40:20as far east as Iowa.
40:23But the most notable
40:25and active supervolcano
40:26is actually one of America's
40:28favorite family destinations,
40:31Yellowstone National Park
40:32in Wyoming.
40:34The entire park
40:35is a gigantic caldera
40:37with boiling magma pulsing
40:39just beneath visitors' feet.
40:43The magma that forms
40:45the supervolcano in Yellowstone
40:47is actually what heats the geysers
40:49and the mud pools
40:52and the other natural formations
40:53you see.
40:55Scientists believe
40:56that an eruption at Yellowstone
40:58and its aftermath
40:59would be comparable to Toba.
41:01Well, the interesting aspect
41:03about Yellowstone
41:04is that when it erupts,
41:06it looks like it erupts big,
41:08real big.
41:09A Yellowstone has had
41:10two supervolcano eruptions
41:12in the past few million years.
41:14In fact, it seems that Yellowstone
41:16is on a 600,000-year cycle.
41:19The last time Yellowstone erupted?
41:21650,000 years ago.
41:25What would happen
41:26to modern society
41:28if one of these supervolcanoes
41:29in the western United States erupted?
41:31If the same amount of ash
41:33from the Toba eruption
41:35were to, say, erupt
41:37from Yellowstone,
41:38that would cover
41:40the continental United States
41:42in about four inches of ash.
41:45Imagine the effects
41:46that that would have.
41:47It would just be horrible.
41:49Just as with Toba,
41:51the area closest
41:52to the supereruption
41:53would face
41:54the most immediate devastation.
41:57Although Wyoming
41:59is a relatively rural state,
42:01there are urban centers
42:02like Las Vegas
42:04within striking distance.
42:05If a supervolcano
42:07were to erupt
42:08in the western United States,
42:10the odds of surviving
42:11in Las Vegas
42:12would really be against you.
42:14Massive amounts of ash
42:15would be only the first obstacle
42:17to overcome.
42:18Las Vegas would be
42:20under inches
42:21of this really, really thick ash,
42:23and it's heavy.
42:24So it can collapse roofs,
42:26it can bury animals,
42:28it can bury people,
42:29it can bury cars.
42:31As the ash spreads
42:33across the country,
42:34the air would be
42:35too toxic to breathe.
42:37People would be forced
42:38to wear protective masks
42:39over their eyes and mouths.
42:43Crops would fail
42:44and water sources
42:46would become polluted.
42:47Car engines would clog
42:49and any plane flying
42:51would come hurtling
42:52to the ground
42:52as the engines
42:53stopped working.
42:56Jets can't handle
42:58that volcanic glass.
42:59It causes the engines
43:00to flame out,
43:01especially the bigger jets,
43:03747s.
43:04But the ash fall
43:05would be just the beginning.
43:06As we saw with Toba,
43:08while the ash settles,
43:10the destructive sulfur gases
43:12would be making their way
43:13into the stratosphere
43:14and circling the rest
43:15of the world.
43:17It wouldn't just be
43:18a case of, oh,
43:19poor America suffers,
43:20the world would suffer.
43:21The devastation
43:23of a natural disaster
43:24like a hurricane
43:25or a tsunami
43:26or an earthquake
43:28can be dealt with
43:29because even though
43:30the people there
43:30are shocked,
43:32we can bring in food
43:33from other places
43:34in the world.
43:34We can bring in
43:35medical supplies.
43:36If a supervolcano erupted
43:38today, there wouldn't be
43:39anybody from anyplace else
43:40that would come help us,
43:41like in these
43:42smaller-scale disasters.
43:43It would affect
43:44everybody in the world.
43:46Scientists agree
43:48it's not a question
43:49of if another supervolcano
43:51will erupt.
43:51It's a question of when.
43:54There's really no way
43:55to prepare for the eruption
43:57of a supervolcano.
43:58They're just so massive
44:00that this is not a power
44:02that we can contain
44:03with any known technology.
44:06The Earth will survive.
44:08I'm not sure that humanity
44:10would bounce back
44:11from such a tragic kind
44:14of event,
44:14such a dramatic
44:15and catastrophic kind
44:16of event.
44:17So Earth, it turns out,
44:19is fairly resilient.
44:20It's the conditions
44:21for human life
44:21that may be more at risk.
44:24Supervolcanoes
44:25do not just erupt.
44:26They are catalysts
44:27for global climate change
44:29and devastation.
44:30Unlike other natural disasters
44:32that are often localized
44:34and even avoidable,
44:35a natural disaster
44:37like the one unleashed
44:38by the Toba eruption
44:39is inescapable.
44:41These volcanic winters
44:43and the consequences
44:44of such apocalyptic change
44:46may only happen once
44:47every 100,000 years,
44:49but when they occur,
44:51the planet and its inhabitants
44:53are never the same.
45:11We are inescapable.
45:11We are inescapable.
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