Original subtitles

Narrator: One phantom signal has been broadcasting

24 hours a day,

Seven days a week for the last 40 years.

And we don't know why it exists.

Dr. Kislenko: If the signal suddenly stops...

We will all be dead inside a few minutes.

Narrator: 2003, china sends their first person into space.

Yang liwei is only in space for 21 hours

And is completely alone -- and then...

Suddenly there's a knock.

I would have been scared out of my mind.

Narrator: Did yang liwei have a visitor?

An international team of earth scientists

Are studying ice cores taken from antarctica and greenland.

They make a startling discovery --

A strange signal buried deep in an ice core.

There had been a large eruption of a volcano

That hadn't been documented.

The vast majority of people who actually witnessed an event

Of that scale were likely killed.

Narrator: Endless streams of data,

Information bombarding the planet from within

And from the furthest stretches of the universe.

What messages do these phantom signals hold?

-- Captions by vitac -- www.Vitac.Com

Captions paid for by discovery communications

Some signals are temporary -- quick blips on the radar,

Hums is that last minute then fade into the ether.

But one phantom signal has been broadcasting for 24 hours a day,

Seven days a week for the last 40 years...

But no one knows why.

Uvb 76 is affectionately known as "the buzzer."

It is an a.M. Signal. [ radio buzzes ]

It's mostly a hum. It's mostly a buzzing noise

That emanates, as one would expect from,

Let's say, a radio transmitter

That has emanated out of the soviet union and russia.

And we don't know why it exists,

But we know that it came out around the cold war.

Narrator: Russia has stayed silent about the buzzer,

Never stating its purpose or even admitting to its existence.

But the buzzer has a huge following

Trying to interpret its random signals

With the growth of the internet,

We have people that are actively monitoring

This thing all the time.

People have cataloged all the little changes

That have happened through the years on this thing.

But at its very core, it's this buzzing noise that turns on,

Turns off...

Frequently intermixed with unusual

And frankly really creepy commentary all in russian.

[ male voice speaking in russian ]

And human voices have been heard

In the background saying different things.

And it's that kind of creepiness which has allowed us

To entertain all sorts of possibilities.

Narrator: Is this phantom signal a meaningless remnant

From a cold war system,

Or does this simple tone foretell

Something far more sinister?

When it comes to the buzzer,

There are four prevailing theories.

The first one is really that

This is a ionospheric scientific test.

Not a lot of people buy it because that's not consistent

With scientific protocols at that time,

And that doesn't seem to be a logic behind it.

The second one is the idea

That this is what's called a numbers station,

Which is an intelligence term to describe

How intelligence agencies would communicate with spies.

Third possibility about the buzzer,

What's often referred to as a placeholder,

Meaning that the russian military reserves

Various radio frequencies for emergency,

Whether it's civil or military.

And then, of course,

The one that I think most people are interested in

When it comes to the buzzer is a possible fourth explanation,

And that's what's often referred to as the dead hand signal.

Narrator: The dead hand was a fabled automated destruct system.

In the case of a nuclear war,

If the dead hand did not detect any remaining member

Of the russian military hierarchy,

It would trigger a full scale missile launch against the west.

Nass: So if that buzzer stops for x-plus minutes,

It would start world war three and the soviets

Would start launching their missiles

At the united states or everywhere.

Narrator: The russians claimed it was dismantled in the 1980s.

Is the buzzer proof that the dead hand is still in operation?

So the question is why?

What's the purpose to keep it

Going for 40 years, to keep it powered?

We don't know.

Narrator: Uvb 76 first came on the air waves

In the wake of the cold war in 1982.

Though it seems to be coming from a military base,

Why does its signal intensify after aggressions have cooled?

This is the era of ronald reagan,

Who, of course, beefs up the u.S. Military,

Invests heavily in existing systems

And then non-existent systems --

Things like the strategic defense initiative, sdi,

Predicating anti-missile defense is on satellites in space.

So if you frame it in that light,

The construction of a dead hand signal,

Sadly, it kind of "makes sense"

From a russian perspective.

Narrator: But what if the buzzer has a simpler, more direct purpose?

In 2010, the fbi announced the breakup of a secret

Russian intelligence ring operating via shortwave radio.

The use of shortwave for spies is really important

Because of the distances it covers, the accuracy,

The sort of stability of the signal.

Nass: It bounces off of the atmosphere,

So we get an enhanced propagation

By using the atmosphere in the ionization therein

To extend our signal out.

Dr. Kislenko: It is generally not detectable, meaning that it can be operated

From outside a particular country

And broadcast inside a country.

That's imperative

So that the enemy doesn't come after you.

So it has been the medium of choice

For a lot of intelligence networks throughout history,

Including today.

And that's important because in today's world

Of particularly computer-based technology,

We often forget everything can be hacked.

So to some degree, you're kind of going back

To old-school stuff, which makes it more problematic

To intercept communications like this.

So there's an idea that the buzzer is actually

What's often referred to as a numbers station,

Which is an intelligence term.

The way you receive numbers stations is

You just turn your radio,

Likely just a little hand-held shortwave receiver,

To that frequency at the right time of day,

And you will hear a human being come over the line

And just say numbers and those numbers can get decoded

To display a message.

Narrator: Is uvb 76 a secret russian numbers station

Communicating sensitive intelligence

That could affect the world,

And how is it managing to do this under everyone's nose?

Most people have this idea when it comes to anything

Intelligence that is this world of james bond and secret devices

And super sexy women and guys with fancy cars.

And that's quite laughable, right?

Anybody who's worked inside the intelligence community

Knows that's not the reality.

Intelligence sometimes functions really simply.

It's not as high tech as you imagine.

And when it comes to shortwave, that's particularly true.

It's the cheapest, most efficient way to communicate.

Nass: The important thing to remember with radio

Is as long as you're supplying power to the transmitter

And the antenna system, it'll keep working.

What's nice about that is even though everyone can hear it,

It's robust.

It doesn't depend on the internet.

It doesn't depend on a complicated scheme

Of being able to send data back and forth.

Narrator: The fact that radio is so easy to receive really is the secret

To a numbers station's effectiveness

As an espionage tool.

Because they're using these one-time pads.

Dr. Kislenko: Which are uniquely constructed

Alphanumeric sequencing

That's literally used once.

Narrator: The one-time pad is known

As the only mathematically unbreakable system.

The letters of a message are converted into numbers

And added to other numbers in a process called false addition.

The recipient uses the same page from his own one-time pad

With false subtraction to translate the message.

There is nothing to crack.

There is no aspect of it that we can figure out and get it

And then we will now be able to crack all these messages.

No, they'll just make a different one-time pad

And give that to the next person.

And then we've lost the trail.

Dr. Kislenko: So it's like you and I speaking a new language every single day.

And that's why in the world of cryptology,

It's almost impossible to break them.

Narrator: Is the russian military still sending out messages

Encoded using a one-time pad?

If so, what could these messages have said,

And who were they meant for?

So, I'm listening to buzzer.

Mikhail. Demetri. Zhenya. [ indistinct ]

Mikhail. Demetri. Zhenya. [ indistinct ]

Three numbers. 25.

[ man speaking in russian ]

919.

[ man speaking in russian ] zero, zero.

So he said three times [speaks in russian]

[ man speaking in russian ]

Which is "cancel, cancel, cancel."

And then he says, "over."

The tone of his voice doesn't change.

It's probably a list that he's reading off.

It does sound like it's a communication

That is destined for someone.

Narrator: Though it's possible russia is transmitting coded messages

To russian intelligence abroad via uvb 76,

That doesn't explain the constant buzz and the tones.

Do these noises also serve a purpose?

Some think so.

The big speculation, of course,

Is that the buzzer is a dead hand switch.

Narrator: The dead hand is a legendary russian detonation signal

Meant to launch a full scale nuclear attack on the west.

So if the signal suddenly stops,

There's going to be one of two reasons.

Narrator: Is the buzzer proof that the dead hand signal is real?

Dr. Kislenko: Let's all pray to whatever you believe in

That they've dismantled it altogether.

The other option is we will all be dead inside a few minutes.

♪♪

Narrator: A series of buzzers and tones has been broadcasting

At 4,625 hertz

For 24 hours a day for nearly 40 years.

Though we know the station broadcasting the signal

Is somewhere in russia near estonia,

The content of the messages

And the significance of the tones remains unknown.

While some speculate the station is a relic from the cold war,

A numbers station barely in use,

Its continued activity raises questions.

This is what's fascinating to me about the buzzer

Is it's not like a traditional numbers station.

The buzzer doesn't seem to be sending any information.

It's not imparting data

Because there's not a lot of characteristic changes to it.

And it's not varied in the noise.

The noise is consistent and the same.

So the question is why? We don't know.

Narrator: Though some say the importance of this station

Is in the numbers broadcast on the station...

Others contend the mere activity of the station itself

Has significance.

The big speculation, of course, is that the buzzer

Is a dead man switch --

That if the buzzer were to stop, it would start world war three.

Narrator: At the height of the cold war, the russians believed

America's nuclear arsenal was so extensive

That it could wipe out russian leadership in one fell swoop,

Cutting off any possible retaliation from the kremlin.

To prevent this from happening,

The soviets created what is called a dead hand signal.

Dr. Kislenko: In the 1970s, the soviet union had spent most of the cold war

Trailing the united states, right,

Playing catch up in terms of its nuclear capacity.

If you're russian, there is a sort of they've got a gun

To my hand kind of, you know, proposition constantly.

And that would in part explain their desire

To develop the system.

If the buzzer is a dead hand signal,

Then fundamentally its job

Is to keep the computer thinking that life exists in russia,

Because the moment that it thinks that it doesn't,

It activates and it has one mission,

Which is entirely unstoppable once it's active,

Which is to retaliate with a full scale nuclear attack

On presumably the united states.

Narrator: Nicknamed the doomsday device, the dead hand signal

Would almost guarantee mutual annihilation

In the advent of a nuclear bomb detonation in soviet russia.

Most experts suspect is that it has been designed

To detect a mass of seismic activity,

I.E., an explosion that can't be explained,

And there has been an inordinate light flash,

Which is consistent with a nuclear attack

And that all communications as it knows them,

Both military and civilian, have collapsed.

Because those are the hallmarks of a major nuclear attack.

I'm not scared by the buzzer from a couple of reasons.

It's already stopped and then restarted.

Narrator: There have been two instances of the buzzer

Going completely silent.

One was on June 5, 2010,

And again in August of that same year.

So is it also a psi ops campaign

That's not connected to anything?

The mere fact that it's there is to mess with people like me

That that search about it online and try to pick it up at home?

Narrator: If uvb 76 is not, in fact, a dead hand signal,

Then does it serve other military purposes?

Dr. Kislenko: I think the vast majority of intelligence scholars

Believe that this is a military placeholder,

That basically this is the military testing

Its own capacity for alertness, for readiness,

Narrator: Whether it's transmitting messages to foreign spies

Or serving as a silent alarm ahead of nuclear annihilation,

Uvb 76 is doing something.

This one is definitely going to continue to be a mystery

Because until we are provided some kind of new evidence,

Things can keep changing

And we're not getting a larger picture of why it exists.

♪♪

Narrator: 2003, china sends their first person into space,

An accomplishment that the world is watching.

Yang liwei is only in space for 21 hours

And is completely alone in a way that very few people

Can say they have ever been.

And then, while orbiting earth,

He hears someone knocking on the body of the spaceship.

Dr. Proctor: Space is a vacuum and it's not supposed to make sound.

Something knocking on the outside of a spacecraft,

It just doesn't make sense.

Narrator: Sound travels by vibrations of molecules

Through a medium like air.

In space, there is only one way

For yang liwei to hear the banging.

It takes physical contact between objects in space

To transmit sound energy.

So if I'm, you know, one inch away from the spacecraft

And I yell as loud as I can, you won't be able to hear me.

But if I bang on the outside of it,

Then I create a resonance in the structure

Which is transmitted

Via sound through the atmosphere in the structure.

Narrator: Could a meteorite or other space debris be hitting the ship?

Most objects traveling in space

Are traveling at enormous speeds.

We're talking tens of thousands of miles per hour.

Objects traveling at this speed don't tend to bounce off objects

And make knocking sounds.

They tend to go through the object like a bullet.

Dr. Williams: If you look at the starboard radiator on endeavor

After we landed, it looks more like a gunshot

Went through the thing.

And that's not surprising

Because a piece of debris in space

Is traveling in a ballistic trajectory.

Needless to say, larger debris would just be catastrophic.

Narrator: Damage to the ship means that yang liwei could lose atmosphere

And consciousness very quickly.

As an astronaut, if I hear a sound I'm not familiar with,

I'm going to very quickly try and figure out what that sound

Is because I want to be here tomorrow.

Narrator: Yang liwei didn't admit that he heard the knocking

Until 13 years after his space flight.

The one thing that an astronaut is not going to do

Is generally report something weird happening in space.

You don't want people to think you're crazy and not fit to fly.

♪♪

Narrator: China launches its first manned spacecraft in 2003,

Making it the third nation after russia

And the usa to send a man into space.

Former fighter pilot, astronaut yang liwei,

Is manning the inaugural mission.

Everything is going like clockwork

Until he hears strange banging against the ship.

It sounded like a wooden mallet hitting a bucket.

[ clanging ]

Narrator: In an interview in 2016,

Yang liwei admitted that the knocking made him nervous,

So he cautiously looked out the porthole window and saw nothing.

No space debris.

Our job is to be able to function flawlessly

In that environment,

Deal with those unforeseen circumstances

And document what is actually happening

So that others can learn from the experience.

We can prepare for future missions.

Narrator: He checked everything thoroughly.

There was no damage to the cabin.

Yet the knocking continued.

[ clanging ]

The whole idea of being isolated

And just being a human being

Means that your willpower and your ability to stay calm,

It can have ebbs and flows.

Every time we're in space,

We're learning more about the body, about the brain

And how it interacts with space.

How does it change our perception

Of the world around us?

Narrator: It is well known that sailors can experience hallucinations

After long periods in the middle of the ocean

With no land in sight.

Does being in space produce the same effect?

We live our daily lives knowing we're attached to the earth

Because we feel gravity.

So imagine losing all the cues that place you

And keep your upright stance or lying down

Or whatever position you want to leave your body --

And all of that's gone both from gravity

And from vision around you.

You've got to feel a bit lost,

A bit dislocated from the world.

Arama: I'd like to think maybe he actually heard something

That was really there.

I would say that's as plausible as the other side of the coin,

That he was hallucinating and panicking

In a state of isolation, being alone.

Viggiani: With respect to astronauts,

They're probably the most highly trained aviators on the planet.

There are no other better in terms of physical endurance

And visual acuity and just overall intelligence.

Dr. Proctor: Astronauts are like the solid rock.

When we think of neil armstrong and landing on the moon,

They are technically ready, they're emotionally equipped.

And so something like this

Makes you think something weird was going on here.

The only thing that we're left with

Is that somehow there are beings that can

Be on the outside of a craft.

Narrator: Yang liwei isn't the only astronaut

To experience strange phenomena in space.

98% of these astronauts have expressed

That they were followed by craft of unknown origin.

Delaney: As he flew his capsule through orbital sunrise,

He noticed that it looked like a whole series of fireflies

Were surrounding the capsule.

♪♪

Narrator: Astronaut yang liwei is piloting

The first manned space mission launched by china.

While orbiting earth, he hears a strange banging sound

Coming from outside his shenzhou 5 spacecraft.

It makes a visual check inside and out

And can find nothing making the noise.

It is mind boggling to me that you could be

In a spacecraft orbiting our planet

And after years of training,

You know everything about the spacecraft,

And suddenly there's a knock,

A knock that appears

To be coming outside the craft.

How could you not freak out?

Narrator: Being alone in places as vast as the ocean

Or space can exacerbate stress and feelings of isolation,

Even cause hallucinations.

Was this what was happening to yang liwei?

These are the most expensive machines that mankind

Has ever assembled to go into space.

If you put an astronaut in charge of one of those craft,

You better be darn sure that you got the right guy there.

And 98% of the situations that involved astronauts,

They were the right people.

They had, as the vernacular goes, they had the right stuff.

Narrator: Yang liwei spent 21 hours in space.

After returning to earth, he spoke openly

About the noises he heard

And soon discovered that he was not alone.

A lot of the research that I've done,

98% of these astronauts have expressed

That they were followed by craft of unknown origin.

Narrator: In 1962,

John glenn becomes the first american to orbit the earth

And the mercury friendship 7 capsule.

While in space, he sees mysterious lights twinkling.

As he flew his capsule through orbital sunrise,

He noticed that it looked like a whole series of fireflies

Were surrounding the capsule.

It was a little bit disconcerting.

Viggiani: What john glenn saw in space

Where the effluent discharge of, I guess, liquid, urine

Or whatever it happens to be,

And in the the cold environment of space,

These things light up as crystals.

And as you move them out there,

There's no telling how these things diffused themselves.

And it's very easy to see a conglomeration

Of these things doing strange things.

Narrator: John glenn's fireflies had a rational explanation,

But other astronauts have not been able to explain

Their strange encounters in space.

Viggiani: One of the astronaut stories that we have on record

Is a shot of the earth.

And then we see a trail of a ufo and going this way.

This particular instance has been described by the air force

And by other pilots as something very significant.

But as it would be told by nasa,

It was water coming off the spacecraft.

But it doesn't explain how this ufo -- what looked to be --

Just shot off into the distance at blinding speed.

I think a lot of people at nasa and in the general public

And in the government completely discount this.

So as soon as you start talking about ufos, you're nuts.

The one thing that an astronaut is not going to do

Is generally report something weird happening in space

Because you want to go up again.

You don't want people to think you're crazy and not fit to fly.

Narrator: Perhaps that's why yang himself didn't talk about the incident

Until 2016,

13 years after he heard the strange knocking in space.

Do space agencies have a vested interest

In keeping these strange sightings quiet?

In the last 20 years,

We've really learned through great pieces of equipment

Like the hubble space telescope and the spitzer space telescope

That a large percentage of the star systems

In our universe have planets.

We're starting to get to the point where now we can see

It's likely there's life in other parts of the universe,

But the distances are so vast,

It's just really unlikely that some alien's

Going to come up and bang on our door.

Dr. Fallah: Any alien who could reach our spaceship doesn't need to knock.

I fall on the rational.

I think that if it's not something expanding or shifting

Due to temperatures going on in space,

Then it's going to be something very physical.

And when you're in an earth orbit, low earth orbit,

Every 90 minutes is one day. That means every 45 minutes

You're going through sunrise and sunset.

The side of a spacecraft facing the sun

Can experience temperatures of hundreds of degrees.

The side facing away from the sun will drop

To temperatures approaching 100 degrees below freezing.

There are many, many opportunities

For the spacecraft to be creaking, shall we say.

Narrator: Thermal expansion is a well known phenomenon.

It's hard to believe that an astronaut

Would not have known about it,

Or at least considered the possibility.

We can't prove that's happening.

But I'd be very surprised if there was no sort of noise

At all just from the material changes in spacecraft

As they're exposed to light and dark.

Narrator: With a lack of concrete evidence,

We may never know what exactly knocked on the outside

Of yang liwei's ship in 2003.

You know, I think we would be very naive

To assume that we understand

All of the elements of exploring space,

Particularly as we go farther away from the earth.

There's going to be unexplained things

That will happen to individuals

As they go back to the moon and ultimately explore mars.

And whether it's exploring space or exploring

The underwater world, you still bump into the new,

The unforeseen, the inexplicable,

And that's the excitement of doing what we do.

Narrator: In 2009, an international team of earth scientists

Are studying ice cores taken from antarctica and greenland.

They make a startling discovery.

A discovery was made that basically showed us

There had been a large eruption of a volcano

That hadn't been documented.

This deposit was substantial.

There was enough material

That had obviously been produced by a volcano

For scientists to say, "hmm, this probably correlates

With a pretty major eruption."

Moore: When a volcano erupts, there's a huge amount of energy.

So you can see all these kind of big cloud of gray ash

Kind of being ejected vertically right into the stratosphere.

It's likely that this eruption occurred in the early

1800s, so not a time when we had

A lot of very good monitoring of worldwide events.

Narrator: By counting backwards through the layers of ice in the sample,

Scientists were able to estimate that this mega volcano

Erupted some time during 1808 and 1809

With enough massive force that the ash it produced

Travels all the way to greenland and antarctica.

Volcanic eruptions can put tens,

Hundreds of cubic kilometers of material into the atmosphere.

Moore: The stratosphere, it's about 10 or 12 miles

Up in the atmosphere.

And if you can inject particles into the stratosphere,

They will live there for months or even years.

Over time, that single source of ash will be distributed

All the way around the globe.

Phoenix: A volcanic eruption of this size could very well

Alter global effects that people are experiencing with weather.

It could essentially blanket the planet for a period of time

And actually help cool

The planet for a couple of years.

Narrator: A volcano that catastrophic would be the largest

Ever seen in human history.

And up until 2009,

There was only one volcano that held that title.

There was a volcanic eruption at tambora,

And that was a pretty large one.

It's absolutely cataclysmic.

Narrator: In 1815,

Mount tambora in indonesia goes full mega volcano

And erupts with a force of 20,000 little boy atomic bombs.

The blast has heard all the way in java, 1,600 miles away.

10,000 islanders are killed instantly.

When we're talking about putting material into the atmosphere,

We're talking about fine grain material.

Heavy stuff, you know, like if you're blasting boulders

Out of a volcano's caldera,

Then that's going to fall to the ground pretty quickly.

But the vast majority of material

Which is being launched at phenomenal velocities

Out of a caldera,

That material is very, very fine-grained stuff.

And that will be carried to high altitudes

And then carried by the jet stream.

Narrator: The eruption of mount tambora was powerful enough

To change the earth's climate for several years.

This volcanic eruption has been linked now

To starting what we call the little ice age.

Narrator: In 2009, an international team

Of earth scientists

Make expeditions to antarctica and greenland

To collect ice cores.

Ice cores are a direct archive of the earth's history

Captured in layers of glacier ice.

The long cylinders of ice

That geologists collect hold a record of what the earth

Was like hundreds of thousands of years ago.

The team from the university of south dakota

Make a startling discovery

From just 200 years ago.

A discovery was made

That basically showed us there had been a large eruption

Of a volcano that hadn't been documented.

Moore: When a volcano erupts, there's a huge amount of gray ash

Ejected vertically right into the stratosphere.

So over time, these particles will then be rained out

Or snowed out onto the ice.

So what you'll find on the ice core

Is that within a year or two of the volcanic eruption,

You will find a signature

Of that volcanic eruption in the ice core.

It's likely that this eruption occurred in the early 1800s,

So not a time when we had

A lot of very good monitoring of worldwide events.

That's the big problem.

So we pretty much know

All the volcanic eruptions going back

To probably about 1,000 a.D.

But there are events --

We see signals in the ice core

That have no known record to them.

And those are these kind of mysterious events

That we don't know what actually happened.

Narrator: In 1815, mount tambora erupts in indonesia.

At the time, it's the most massive volcano

In recorded history,

Killing 10,000 islanders instantly.

Anybody in the path of the ash that blows

Is going to be covered in -- ash is not fireplace soot.

It's not what happens when you burn wood.

Volcanic ash is made of pulverized rock fragments,

And that pulverized rock, if you breathe it in,

It will shred your air passageways.

Narrator: Tsunamis are triggered in rivers of volcanic rock

And ash rains down from the skies, burying entire villages.

Over 100 million tons of sulfuric acid and ash

Fill the earth's stratosphere, blocking out the sun.

Those are super volcanic eruptions,

And they drop the global temperature

For a couple of years.

You're talking about a lot of material

Being thrown into the atmosphere to the jet streams

That is changing the atmosphere

And that changes the quality of sunlight.

There's a kind of a rapid cooling,

And that's because as soon as you shut down the sun,

You can really cool the planet down.

And it doesn't take much to produce crop failures because,

Again, crops are kind of tuned to a certain temperature range.

Narrator: The year after tambora, 1816,

Was dubbed the year without a summer.

Crop failures and food shortages

Led to rioting in britain and France.

Dr. Kislenko: We talk about a dense fog.

The skies become a dark blue,

And for weeks and months afterwards,

There is fundamental climate change in europe,

Tremendous agricultural collapse and the freezing of waters

And things that are abnormal.

It gets woven into the tapestry of european history.

Narrator: The effects were felt as far away as america's eastern shore,

Where in may 1816, snow and frost killed off crops

In massachusetts, new hampshire and vermont

And continued through the summer.

The famine was soon followed by outbreaks of typhus and cholera

In many parts of the world.

In this instance, with this volcanic eruption,

It is -- has been linked now

To starting what we call the little ice age.

Narrator: The little ice age was a period of significant climate change

That happened between 1810 and 1819.

The mount tambora eruption has long been considered the cause,

But scientists had never understood what caused the dip

In temperatures before tambora's eruption in 1815.

But now evidence of a volcano potentially bigger

Than tambora cemented in an ice core.

How could it be that no one witnessed

An eruption so catastrophic?

It's even more complicated because we lack,

Especially going back far enough in time,

We lack historical documentation for even major events,

Which, of course, in our time and place is mystifying.

It's very possible that this volcano

Erupted very far from europe

Or where centers of the written word where at the time.

So we need to look to what we're seeing

Preserved in the geologic record

And what people on the ground at the time experienced.

The other option, of course, is that it was noted and again,

Those records have been lost

Or have been sitting in some archive,

In some basement of some, you know, library

Which haven't actually been looked at yet.

Delaney: We have figured out so much based upon the records

That go back literally 10,000 years.

Our forebears from all around the planet figured out

When we hear stories from all sorts of indigenous cultures,

They are talking to us about a lot of events

That might sound almost mythical,

But they invariably have a basis in fact.

And so there is pieces of that tapestry

That are literally woven together by people passing

That information on down in the form of stories.

Narrator: And are there other clues

To this mysterious volcano's origins?

Phoenix: To find this eruption,

I would first look at the coastal areas of south america

And then I would probably look all along the ring of fire,

As the pacific region is often known

For its earthquake and volcanic activity.

So those are prime suspects in my mind.

Narrator: Could these mega volcanoes ever come back to life?

This isn't a forest fire.

This isn't a storm on the horizon.

This is something distinctly different.

We don't like to say a volcano is ever extinct extinct.

A lot of times we can say we believe

With all available evidence

That a volcano most likely will not erupt again.

But you never really want to write them off.

♪♪

Narrator: Ice core evidence has convinced earth scientists

That a mega volcano erupted in 1809,

Plunging the world into a little ice age.

It's not hard to imagine a situation

Where you've got volcanic eruptions

Accumulating material in our atmosphere

That really does change the balance of temperature

On our surface.

Narrator: This mysterious mega volcano erupted six years

Before the catastrophic mount tambora blast.

But mount tambora had witnesses

And the mystery eruption did not.

The problem is, is that most first-hand experience

For things like volcanic eruptions,

The vast majority of people who actually witnessed an event

Of that scale were likely killed in it

Or shortly thereafter in a tsunami or in some,

You know, atmospheric condition.

Finding the clues that will allow us to understand

This mystery eruption is actually very important.

Narrator: If such a cataclysmic eruption happened now, could it disappear

Without a trace?

A v.E.I. 8-level eruption in an area

That was densely populated would kill millions of people.

We need to look at the recent past for an example

Of what a very large eruption can do.

Narrator: The volcanic explosivity index was developed in the early '80s

After the eruption of mount st. Helens in oregon.

It measures the ejection volume of a volcano,

With each step increasing by 10 times.

A lot of people think that a mount st. Helens-type eruption

Is basically the biggest thing that a volcano could produce,

And that's not the case.

To measure the volume of volcanic eruptions,

Scientists use something called the volcanic

Explosivity index -- the v.E.I. Scale.

Mount st. Helens is a five on the explosivity index.

Narrator: On may 18, 1980, mount st. Helens

Erupted with eight times the force of every bomb

Dropped during world war two, including the two atomic bombs.

A lateral blast released a toxic spew that traveled down

The side of the volcano at 300 miles per hour

And obliterated everything in its path.

Thousands of wildlife were decimated.

57 people were killed.

Hundreds of miles of road and railways were destroyed.

Then, 11 years later, mount pinatubo

Erupts in the philippines.

It is v.E.I. 6 --

10 times more powerful than mount st. Helens.

722 people died and 200,000 were made homeless.

Even with such widespread devastation,

Pinatubo is 20 times

Less powerful than the estimated size of the mystery eruption.

Could it happen again?

Vulcanology is a relatively young science.

The modern era of vulcanology only started

40 years ago this year

With the eruption of mount st. Helens.

Before then, we were monitoring volcanoes around the world,

But it wasn't quite so systematic.

So it's super important for geologists to add this eruption

To our catalog of knowledge about vulcanology

Because it helps us understand the frequency

A big eruption like this --

The frequency with which it could occur.

Oftentimes, we don't see big eruptions like this.

Yellowstone hasn't erupted for 640,000 years

Not in a big way.

I don't think there's anything on the planet

With the possible exception of the seas,

That generates more human history, mythology,

Belief systems, religion, if you like,

Than volcanoes do.

You have volcanoes shaping --

Profoundly shaping the history and cultures

Of the so-called ring of fire, which is almost

All of the expanse of the pacific ocean.

Narrator: The ring of fire traces the 25,000 mile outline

Around the pacific ocean

That is home to 75% of the world's volcanoes

And 90% of the earthquakes.

It is ground zero for tectonic shifts in the earth's crust.

This is where you have one tectonic plate

Diving under another.

As the plate that is diving gets deeper,

It gets hotter and the material melts.

So that rock, that previously ocean floor rock, is melting,

And hot stuff rises.

That's basic physics.

So as the melting stuff rises back to the surface,

A lot of times it forces its way through the crust.

That's like a massive volcanic eruption.

Narrator: With no eyewitness accounts

And only ice core samples as geological evidence,

Earth scientists can only speculate

The mystery eruption of 1809

Happened somewhere in the ring of fire.

Regardless of where this eruption occurred,

This is one of the events that really shows us

The true nature of volcanoes.

They are forces of incredible creation

And terrible destruction.

The earth is actually creating new earth.

That's what it's doing. It's giving birth to itself.

But in the process, it often destroys lives.

In the 1800s,

Astronomy was beginning to really come into its own.

We had a telescope courtesy of galileo for about 200 years,

And by the time we got to the turn of the 19th century,

Instrumentation, observatories around the planet,

They were really making some pretty neat observations.

And so there were a lot of really good observers out there

Monitoring many aspects of the night sky.

Narrator: In 2014, over two centuries

After the devastating mystery eruption,

A team of earth scientists unearth a journal

From a long forgotten observatory in bogota, colombia,

Describing a strange cloud

That blocked out the sun at the end of 1808 into early 1809.

Which is on possibly the other side of the world

From where this volcano may be, that described

The sun taking on a silvery color, almost like the moon.

And of course, there was also a description of the weather

Being colder and frost appearing when they wouldn't expect it.

It's echoed by [indistinct],

Physician, an amateur astronomer,

And almost in the same time frame, separate,

They are talking about, you know,

This tremendous agricultural collapse.

Narrator: Though science may have advanced tremendously since

The 1809 eruption,

It's still difficult to predict volcanoes.

The ability to identify events today anywhere on the planet

Is certainly much easier than it has at any time in the past.

Not only do you have satellite assets at all

Differing distances above the surface of the earth,

Completely encircling the planet so that,

You know, you've got a 24/7,

365 vantage point of anything happening on the earth

And with terrific resolution.

You would think the volcanoes are easy to identify,

But they are not just this v-shape that everyone thinks --

This inverted v.

A lot of times volcanoes

Take the shape of a caldera,

Which is essentially a giant bowl-shaped area.

So the really, really biggest volcanoes,

They're the ones that can erupt the largest.

Narrator: There are 1,500 active volcanoes

On the planet right now.

169 of them are in the u.S.

We do have potentially active super volcanoes

And other very large volcanoes around the world.

So it's something that scientists need to understand.

So that's why a lot of us do what we do.

It's all about saving lives.

It's all about putting pieces into the puzzle

That is our planet.

You know, we're humans.

We're tiny little creatures on this great big living rock.

And we're trying to understand why it ticks, what makes it --

What makes it change and evolve the way it does,

And how can we learn to live alongside gigantic hazards

Like a massive volcanic eruption?

♪♪