Original subtitles

[narrator] Could a Russian lake unknown until the 1920s

help answer one of history's greatest geological mysteries?

Upon investigating the lake,

a team of Italian researchers find further anomalies.

[narrator] A mysterious sight is discovered on a desolate Arctic island.

As they approach the island, they see what looks like tall, curved posts

pointing high out of the snow.

[Dr. Anthony Cantor] It's like stepping into a place of great significance

that's been undisturbed for centuries.

[narrator] New information attempts to solve

the infamous mystery of the sinking of the Titanic.

If this photo is of the actual iceberg, it confirms the size of it.

[Dr. Alison Leonard] If the black mass was the iceberg,

then why did they see it higher in the sky instead of directly on the horizon.

[narrator] These are the strangest mysteries

trapped in the coldest places.

Lost relics...

forgotten treasures...

dark secrets...

locked in their icy tombs for ages.

But now, as ice melts around the world,

their stories will finally be exposed.

The North Atlantic ocean is well known for its frigid seas.

Even in spring,

water temperatures off Newfoundland on Canada's east coast

often hover just below zero.

The North Atlantic is ferocious.

Huge storms and towering waves constantly threaten ships that sail its waters.

But more than just that,

thick layers of fog can limit visibility

while menacing icebergs drift down from the Arctic seas.

[narrator] Billed as the world's most unsinkable ship,

In April 1912, The Titanic struck an iceberg on her maiden voyage

sinking in less than three hours with 1,500 lives lost.

[Cantor] In 2002, a previously unreleased photo is exhibited to the world.

It's a picture of an iceberg

taken by a crew member of a rescue ship called the Bremen.

just days after the disaster.

There are a few photos out there,

that experts think might be pictures of the iceberg

that the Titanic hit,

but this one is special.

[Anthony Morgan] The picture matches a famous description of this iceberg.

It's like the mirror image of the Rock of Gibraltar.

[Leonard] This is an amazing picture.

Part of the iceberg is higher than the rest of it,

which makes it look a lot like the Rock of Gibraltar.

It also shows compelling evidence

of damage on one side.

[man] If this photo is of the actual iceberg,

it confirms that the size of it is at least 65 feet tall and some 400 feet long,

and as with all icebergs, we know that it's far bigger underwater.

[narrator] But the photo also reopens a mystery

that has haunted the disaster for over 100 years.

Why didn't the crew spot the large iceberg in time to prevent the collision?

[Cantor] It's a clear, frigid night with no wind.

And still they hit the iceberg even though the sea is completely calm.

It should've been easy for the lookouts to spot hazards from miles away.

Could the iceberg have drifted further south than they expected?

[Leonard] The captain had received reports of a huge ice field

in the middle of the planned route.

So, as a precaution, he changed course and headed further south.

[narrator] Photos from rescue ships The Carpathia and The Frankfurt,

both document large icebergs and a huge ice field that stretched for 30 miles.

We know that icebergs float south from Greenland

and then are pushed down by currents

along the East Coast of Canada towards Newfoundland.

Some last the entire journey while others melt a little earlier.

It depends on how big they are and how cold the water and the air are along the way.

[Mike MacFerrin] Of the tens of thousands of icebergs

that drift down from the Arctic,

only about 1% of them make it as far south as Newfoundland.

So, it's strange how many icebergs there were that night.

[Cantor] One theory is that that evening the moon was at its closest to the Earth

and that proximity can affect tidal forces.

So, maybe, those tidal forces pushed the iceberg further south than normal.

[narrator] Meteorological records show that the sun and moon

had lined up months before to create a rare astronomical event

known as a spring tide,

which resulted in a far greater number of icebergs

reaching the North Atlantic shipping lanes.

So, if the captain knew there were more icebergs in the area,

why were they traveling so fast?

[Cantor] The Titanic was traveling at her maximum cruising speed

of 22 knots that's about 25 miles per hour.

And we know that the captain was under orders to make good time.

[Leonard] They thought they had avoided the danger

of the ice fields further north,

so they just kept going at full speed.

[Cantor] Because the Titanic was taller than most cruise liners,

men in the lookout sat 95 feet above the deck

and this allowed them to see out 12 miles.

So this should have provided them plenty of time

to spot the iceberg beforehand.

[Leonard] But it's generally accepted that the Titanic had about one minute to react

after having spotted the iceberg.

So, that puts them at only half a mile away when they see it.

It makes no sense.

[narrator] To try and further understand exactly what occurred

on the Titanic that night,

researchers pour over log books of the other ships in the area looking for clues.

Just before the accident,

a ship near by called the Californian

actually saw the Titanic in the distance.

The crew members thought it looked too small and too close to be her.

The captain of the Californian testified that they repeatedly signaled the ship

by Morse lamp trying to identify them,

but the Titanic never responded.

[MacFerrin] The Titanic claimed she tried to signal the Californian by Morse lamp,

but they received no response.

Why didn't they receive each other's messages?

If you can see the ship, you should be able to see the flashing lamps.

[Morgan] At sea level, the ocean can be littered with weather anomalies.

Like low clouds that can affect visibility.

But that night, the visibility was great.

[narrator] If other ships were experiencing strange visual anomalies,

did the Titanic experience something extraordinary

that they were completely unaware of?

Normally, where the sky meets the sea,

the stars are blurred and dimmed.

This is because the humid air distorts the contrast.

It's such a low angle

the light has to pass through miles and miles of atmosphere.

This interferes with how the stars look to us.

[Cantor] But in testimony given

by the Titanic's spotting officer, Frederick Fleet,

he reported seeing a strange clarity in the stars

and a weird haze like a black mass

floating above, not at the horizon.

Fleet sees this black mass, which also has a strange gray peak,

a full ten minutes before they hit the iceberg.

If the black mass was the iceberg,

then why did they see it higher in the sky

instead of directly on the horizon?

[narrator] In 2021, a photographer on England's coast

captured this astounding photo of a daytime mirage.

[MacFerrin] So the ship looks like it's hovering high in the sky

when it's actually just floating on the distant water.

This illusion is easier to see during the day.

[narrator] Could a similar phenomenon,

have been the cause of all the confusion that fateful night?

When they checked the meteorological records for the area,

they found that the water had two radically different readings.

[Cantor] The SS Minion, a cable ship that helps collect bodies,

reports in her log book,

"The Northern edge of Gulf Stream is well defined.

Water changed from 36 to 56 degrees Fahrenheit in half a mile."

On this incredibly clear night,

there was a sudden change in temperature

where two of the Atlantic currents meet.

[MacFerrin] The Gulf Stream from the South usually keeps this area warmer.

But all the icebergs from the Labrador Current

chill the air down to freezing from sea level to a height of 65 yards.

But above that,

the warmer air from the Gulf Stream was still there.

[narrator] The conditions were perfect

for an extremely rare visual anomaly called a super-refraction.

Cold air is denser than warm air

and this causes light to bend or refracts before it reaches our eye

changing how far away objects appear.

The difference in temperature between the two ocean currents

was radically affecting how distant objects were seen.

[MacFerrin] During this phenomenon,

ships can actually appear to be high above their actual position on the water.

Sometimes objects even below the horizon

like stars can get refracted higher into the sky.

[narrator] Could this mysterious sub-zero phenomenon,

have caused the Titanic to hit an iceberg?

[narrator] After uncovering an unpublished photo

of the iceberg that the Titanic struck in 1912,

researchers investigate new information

looking for clues as to why the crew didn't see the iceberg

until it was too late.

A sub-zero phenomenon known as a super-refraction may have played a role.

At night, this kind of mirage can also appear

like a thin bank of haze on the horizon.

[MacFerrin] So even though the night was exceptionally clear,

the Titanic's lookout, Frederick Fleet,

noticed a black haze on the horizon.

He claims to have seen the iceberg

appear out of this black haze at the last moment.

The angle and the height of the lookout points on the Titanic

might have given a false impression of the distance to the horizon.

[narrator] By the time officer Fleet calls the bridge

and they make an immediate hard turn, it's too late.

[Morgan] Ironically and tragically,

if the ship had done nothing and not turned,

she might not have hit the iceberg.

[Cantor] And even if the ship had crashed into the iceberg head on,

it might only have breeched the two to four safety compartments

designed to contain a flood and keep her afloat.

But instead, six compartments were flooded,

which as we know proved to be too many.

[Leonard] This sub-zero atmospheric anomaly at sea level

had hidden the true distance of the iceberg until it was too late.

[narrator] The Titanic and her passengers could never have known

that calm, clear night

was leading them towards one of the great tragedies of modern times.

Even today,

her many secrets still lie hidden in the icy depths of the North Atlantic.

In the Bering Sea on the frozen edge of the Arctic circle,

sits the remote island of Yttygran.

Situated off Russia's eastern most point lies the Chukchi Peninsula.

The island is just over eight miles long and three miles wide

with a mountainous interior.

It's hidden under a thick blanket of snow and ice for most of the year.

[narrator] In 1976, researchers stumble across something out of the ordinary.

[Amma Wakefield] As they approached the island from a distance,

they see what looks like tall, curved posts

pointing high out of the snow.

[Leonard] The landscape in the Arctic is normally pretty flat and barren.

So, it's highly unusual to see anything this tall.

[narrator] Once on the island, they discover something they have never seen before.

Strange, curved poles that seem to be planted in pairs.

There's an eerie feeling to this island.

It's like stepping into a place of great significance

that's been undisturbed for centuries.

[narrator] Closer examination of the poles

leads to a startling discovery.

They are actually giant bones.

[narrator] The scattered remains once formed a long broken avenue,

roughly 1,800 feet in length.

[Jamie Clarke] There seems to be some kind of special geometry to the site

which is quite rare in Siberia.

There's nothing like it in the Arctic.

What is this place?

[Wakefield] These bones are enormous.

What animal could even be this big?

[Leonard] There are examples of early humans using gigantic mammoth bones,

to build large structures that are somewhat similar to this,

but none of the bones on Yttgran island appear to be ivory tusks.

So it's highly unlikely these are mammoth bones.

[narrator] As researchers inspect the base of the structures,

they uncover groupings of giant skulls.

[Cantor] Massive bones like this could only come from a whale,

and upon closer inspection, it's revealed that these are the bones of a bowhead whale.

[narrator] The bowhead whale lives in the Arctic,

it is considered the longest living mammal on Earth,

with a life span of over two hundred years.

It's distinctive triangular head is an enormous skull,

designed to smash through sea ice up to two feet thick.

[Wakefield] The Yttgran site is strewn with weathered remains

of bowhead whale skulls,

and jaw bones of up to sixty other whales.

The 16 feet tall arches are made of over 34 jaws.

[narrator] The avenue follows a man-made gravel spit along the shore.

Extending from the center of the alley,

a stone path branches off for 50 yards towards rocks and the hillside.

[Leonard] This is a truly remarkable site,

these bones just didn't wash up on shore,

they've all been brought here, deliberately arranged and planted into the ground,

but why choose whale bones to built such a place?

[Cantor] In the Arctic, wood is very scarce,

so local people often used animal bones as building materials.

So these could be the bones of beached whales,

but to find this many seems unlikely.

[narrator] Experts believe whale hunting has been practiced in the Arctic,

for many centuries.

This was the result of larger boats called, umiaks being built.

The use of stronger harpoons and an Arctic culture

of feeding a huge amount of people with just one kill.

[Wakefield] The whales can grow up to 65 feet, and weigh 220,000 pounds.

It would've been a highly-valued harvest.

[narrator] The whale bone samples have been carbon dated to the 1600s.

A time when Russian explorers began making contact with the indigenous Chukchi people,

who inhabit the peninsula.

As they continue to investigate the ruins,

researchers find several rings made of smaller stones.

[Cantor] They look like rings,

used by the Inuit and Siberian peoples to anchor tent skins.

And the bone formation sticking out of the permafrost,

may have been substitutes for lumber,

used as posts for small huts.

[Leonard] But looking for further evidence of a settlement,

such as house foundations and tools, the dig comes up empty-handed.

It would appear that no community ever lived here.

[Cantor] This site shows evidence,

of having been designed for a specific purpose,

but it doesn't have any of the usual markers of a significant human presence.

[narrator] When researchers investigate a location at the end of a smaller avenue,

they find something remarkable.

120 conical shaped pits,

up to six feet deep and walled by rocks.

At the bottom of these strange pits,

they discover layers of whale blubber and frozen meat.

[Leonard] Permafrost stays at a near freezing temperature all year round.

In the Arctic, food can be scarce,

so preserving it underground is a great way to ensure that one has provisions,

throughout what can be a long and grueling winter.

[Clarke] This find is highly unusual,

it was able to contain tons of meat,

it's a massive amount of storage in a place where no one actually lived.

Could whale bone alley be more than just a place to store food?

[narrator] On the remote island of Yttgran,

high in Russia's Arctic circle,

a team of researchers investigate a strange alley made of bones.

An incredible 50 bowhead whale skeletons were used in its construction.

The largest of the whale bones weigh between 500 and 650 pounds.

It would've taken a lot of people to carry or transport these bones to the area.

Serious effort went into building this site,

and that could suggest that it was a site of spiritual significance.

[Clarke] Other locations around the world with strange geometric features like,

Stonehenge for instance, also have a tradition of being a gathering place

for now long forgotten ceremonies.

And they are places where people come from miles to feast.

[narrator] The discovery of the hidden meat pits,

leads researchers to believe that whale bone alley,

may have been built to honor the whales.

[Leonard] Hunting a bowhead whale

in a small group of umiaks, powered only by paddles, could be extremely dangerous.

and the hunters who did it and provided for their communities were revered.

But among high Arctic peoples, so are the whales.

They believe the hunter and the hunted are spiritually connected.

The Chukchi performed very specific rituals,

in order to prepare for and perform the hunt,

and then afterwards to honor the whale that they caught.

This included praying, singing and feasting.

[Wakefield] We don't know for sure but they may have brought the whale meat,

up through the archway and then stored them in the pits for later use.

[Leonard] The whale bones used to build this site were believed to help,

the slaughtered whale's soul return to the sea, unharmed.

[narrator] But when they studied the meat pits,

researchers discovered something unusual.

Carbon dating reveals that they were created in the 1300s

This pre-dates whale bone alley by 300 years.

So the meat pits may have been there before whale bone alley.

It could be that the people wanted to pay their respect to the whales,

and honor their importance to their lives,

so maybe they built the site as a kind of shrine or temple.

[Clarke] Maybe in the beginning whales were plentiful,

so they only needed storage pits but if something changed about the hunt in the area,

they may have felt they needed to find a way,

to talk to the whales to ensure a good harvest.

[narrator] When they compare samples of bowhead genetics over time,

with bones found across the Arctic,

something strange comes up.

Their genetic diversity has radically decreased over the last 500 years,

which includes the time that whale bone alley was created.

This indicates their migration patterns could have been altered.

[Leonard] But something called the Little Ice Age,

may have hindered this traditional migration,

thereby shrinking the Chukchi's food supply.

[Cantor] The Little Ice Age was a period of colder temperatures,

that gripped parts of the world from the 1300s to the 1800s,

causing drought, crop failures and famine.

What this did to the bowhead whales was reduce their summer habitat,

where mothers would bring their calves.

If the surface ice was thicker they could have had a hard time finding breathing holes,

and just stopped coming.

So is it possible whale bone alley was built to bring them back?

They definitely stored meat there but if the whales stopped coming

it's likely the site was abandoned for a better hunting ground.

[narrator] Over the years whale bone alley stopped being used,

but the site at Yttgran island remains an ancient pathway to the spirit world,

frozen in time.

The Ural's are a long and narrow mountain range,

that runs 1,550 miles south from the Arctic ocean,

deep into Russia.

The southern Ural's often experience brutal winters,

that can plunge inhabitants into a deep freeze for up to six months of the year.

[narrator] In the winter of 2013,

over a million people are thrown into a state of emergency,

when out of nowhere a massive explosion rocks the city of Chelyabinsk, Russia.

[explosion]

Then compelling dash cam footage is released that stuns the world.

It shows an object speeding across the sky, glowing brighter than the sun.

[Dr. Kim Tait] Locals discover a giant hole in the ice, covering lake Chebarkul.

When they dive the lake, they find a huge metallic rock sunk in the bottom.

It's over five feet long,

three feet wide and weighs an astounding 1,300 pounds.

[narrator] It's one of the largest meteor fragments

ever recovered in modern history.

Scientists studying the meteor discover its unique striations and ancient scars

tell an epic tale.

This meteor has been bouncing around the universe

for over four billion years.

Could this incident help shed light on one of the most mysterious

meteor events in modern history?

[narrator] When a meteor crashes to Earth

near the Russian city of Chelyabinsk in 2013,

researchers wonder if it could help solve another mysterious event

that occurred more than 100 years earlier.

In the year 1908, in Central Siberia,

farmers near the remote Tunguska River,

hear an intense crackling sound in the sky.

They look up to see a bluish pipe-shaped object

moving across the sky.

A series of blasts that sound like cannon fire

echoes across the landscape.

[Leonard] Then a massive explosion blows the farmers off their feet,

slamming them to the ground.

What could have caused such a devastating concussion,

as well as that fire in the sky?

[narrator] Since 2013,

researchers have discovered 17 deep holes

in the Siberian permafrost they cannot explain.

[Cantor] They don't know how they form.

And because the area is so remote,

they've never actually witnessed one forming in real time.

[narrator] Two-thirds of Siberia is permafrost

and permafrost is a natural reservoir of methane.

Could the Tunguska event be a rare geological explosion?

[narrator] A phenomenon caused in part by massive methane build-ups

under the permafrost have resulted in explosions,

leaving large craters pocketing the tundra.

But no such methane explosion has ever been witnessed.

Nor have there been reports of any loud explosions in the area.

[Wakefield] It's not until 1927,

19 years after the explosion

that Russian mineralogist Leonid Kulik

decides that someone needs to conduct an investigation.

After interviewing locals,

Kulik focuses on finding the epicenter.

He climbs a ridge and observes toppled trees,

as far as the eye can see.

[narrator] The trees aren't bent over.

They're snapped off by a very powerful force.

This indicates that the blast must have come from a central location.

[Tait] The blowdown is so massive

he is unable to estimate just how much forest is destroyed.

[Wakefield] But when he arrives at the epicenter, he is mystified.

There is no impact crater.

[narrator] The epicenter of the blast contains upright trees,

but with their branches stripped and burnt.

Kulik even drains some marshes which he suspects might be impact craters,

made by smaller meteor fragments.

But he finds nothing.

[narrator] Modern researchers now know that

80 million trees were flattened in a strange butterfly-like pattern.

They estimate the explosion was roughly forty times larger

then the 2013 Chelyabinsk meteor

that leveled over 830 square miles of forest.

[Cantor] Is there something else

that could have destroyed a massive wilderness like this?

[narrator] Largely made of dust and ice,

comets travel through the frozen void of other space

at thousands of miles per hour.

But they burn up in a very dramatic fashion and then explode.

As they enter the Earth's atmosphere,

temperatures of comets can reach an astounding 3,000 degrees Fahrenheit.

[Tait] If Tunguska was a comet,

the ice could have been vaporized and released into the upper atmosphere.

Maybe that's why there is no obvious crater.

Days after the explosion, before anyone knew what happened,

skies all over Europe

were filled with a strange luminescence.

London's newspapers reported

that it was bright enough to play tennis at midnight.

Maybe the additional ice in the atmosphere reflected light from the sun

down on to Europe and created a sort of glow effect that night.

[narrator] But the comet theory only supports the lack of an impact crater.

A large object made of ice would have entered the atmosphere,

then exploded and vanished almost immediately.

It couldn't have travelled as long,

nor as far across the sky as was reported.

[Wakefield] There also would not have been a light brighter than the sun.

Nor would there have been a sequence of smaller explosions.

[Leonard] Scientists have found meteor fragments

frozen in peat bogs and even embedded in trees.

But there is no way to tell whether or not

the fragments are from some smaller or more ancient meteor.

[narrator] Then in the 1990s,

Italian researchers noticed something strange on an old map.

[Cantor] A body of water called Lake Cheko,

just four miles from the epicenter of the Tunguska blast,

does not exists on any map prior to 1928.

[Wakefield] It is a remote location

and maybe not all the lakes were mapped.

But it is still very strange.

[narrator] Could this previously unknown lake be a flooded impact crater

created by the Tunguska explosion?

[narrator] In a remote Russian wilderness,

researchers investigate a strange lake that didn't exist on any map before 1928.

Could the bottom of this lake hold clues to the mysterious Tunguska explosion of 1908?

Upon investigating the lake, a team of Italian researchers find further anomalies.

Echo soundings reveal it has a rare conical bottom,

rather than the flat bottoms of the other lakes in the area.

[Wakefield] And they discover what they think are half-buried tree trunks,

submerged at the bottom of the lake.

[narrator] Is Lake Cheko evidence

of the missing impact crater made by the Tunguska meteor?

Unfortunately, researchers have not

been granted additional access

to the bottom of the lake.

Limiting their ability to find new evidence to support their theory.

[narrator] But in 2020,

a new team of researchers claim that they have made a breakthrough.

By studying the more recent 2013 Chelyabinsk meteor

recovered from a frozen lake in the Urals

[Tait] They realize new data about the meteor

gives them the ability to simulate

what happens when a very large meteor,

made of iron, hits the Earth.

[narrator] Based on cutting edge computer simulations,

they concluded that the Tunguska meteor

was the size of a football stadium

and weighed 220 million pounds when it entered Earth's atmosphere.

It travelled across the sky at a speed of 30,000 miles per hour.

[Cantor] Temperatures on the comet

would have been about 3,000 degrees Fahrenheit

as it entered the Earth's atmosphere.

And if a meteor of that size

had hit the Earth at that speed,

the impact crater would have been about 2 miles wide.

[Wakefield] It could have plunged the entire planet into turmoil.

Thrusting up tons of debris that would have shrouded the Earth.

Causing millions of deaths and devastating Earth's wildlife.

It had the potential to trigger another ice age almost overnight.

[narrator] But if the Tunguska meteor did crash to Earth,

why wasn't the planet thrown into chaos?

[Cantor] Experts believe something incredible happened

that gave life on Earth a second chance.

Our atmosphere is made of gases.

And when a meteor enters the atmosphere,

these gases act like a protective shield.

[narrator] The scientists suggest that the Tunguska meteor

encountered a monumental amount of friction

and push-back from Earth's atmosphere.

This then caused it to change course

veering into and through the stratosphere,

and back out into space.

Traces of this immense explosion

would be hard to detect on the ground.

'Cause this type of asteroid is made up of sulfur compounds,

which are readily found on Earth.

[narrator] But a near miss could still hold

dark implications for humanity.

[Cantor] Once inside our solar system,

meteors are usually drawn to the sun

by its immense gravitational force.

They then start orbiting the sun until they hit something.

Could that something, one day, be the Earth?

[Wakefield] The good news is, our atmosphere protects us from certain sizes of meteors.

The bad news is, the Tunguska meteor...

may still be out there, and it could possibly return in the future.

[narrator] The Pacific Ocean, the largest ocean on Earth,

at over 14,000 feet deep,

its frigid waters are one of the Earth's last unexplored frontiers.

[Clarke] It's so huge, it's like another world.

Only about 20% of the Pacific floor has even been mapped.

There's still so much we don't know

about what's down there.

[narrator] In 1997, researchers looking for underwater volcanoes,

hear a strange sound, on their hydrophones,

over 1,500 miles, off the coast of Chile.

[Tait] The sound went on for almost a minute.

It sounded like a low frequency, underwater roar.

[Morgan] This sound was louder than a rocket launch.

It's the loudest sound we've ever recorded underwater.

[narrator] The ocean is filled with constant sounds of creatures, geology, and ships.

And experts know their sound signatures.

But, they had never heard anything like this before.

[Morgan] They replayed the sound over and over,

trying to figure out what it could be,

and finally, when they sped it up 16 times,

it sounded like "bloop".

I mean, what is that?

[mysterious sound playing]

[narrator] Hydrophones are special microphones,

used to detect sound underwater.

Sound waves travel over four times faster in water,

and hydrophones are designed to pick up sound waves

that move through the unique high pressure of underwater atmospheres.

By playing sounds at different speeds,

experts can often gain valuable clues as to their origins.

[mysterious sound playing]

[narrator] But, initial investigations into the sound, have researchers baffled.

The first hydrophone network was called SOSUS,

short for the sound surveillance system.

It was built by U.S. scientists,

to act as surveillance microphones during the cold war.

[narrator] During the 1960s,

the U.S. navy had placed a number of listening devices around the Pacific,

as a new form of defense, hoping to hear enemy submarines,

before they could spot them.

But, by the time, they recorded this bloop sound decades later,

they had a network of scientific hydrophones across the Pacific,

some up to 2,000 miles away that also picked up the strange sound.

For the sound to travel that far, whatever made it, had to be huge.

[narrator] In 1997, researchers studying underwater volcanic activity,

picked up a strange sound on their hydrophones.

over 1,500 miles, off the coast of Chile.

They searched for, not just where the sound came from,

but what the sound came from.

A lot of the sounds, in the ocean is made by machines.

So it's possible that the sound could be man-made.

Maybe from a large ship, or a plane, or even a rocket crashing into the water.

[narrator] The ocean is made up of layers of water,

of different temperature, and salinity.

Sound waves travel faster in warm, salt water, and under high pressure.

One layer, the worlds oceans, known as the deep sound channel,

contains prime conditions.

It's located between 300 to 1,000 yards below the surface.

Sound waves can travel through this layer for thousands of miles.

The deep sound channel is an excellent conductor for low frequency sound waves,

which is why the researchers put the hydrophones there, in the first place.

[MacFerrin] But, even in perfect conditions like this,

noises from ships and other man-made objects,

wouldn't be able to travel across 2,000 miles.

[Tait] And these man-made sounds tend to occur closer to the ocean surface,

and therefore, generally travel in the upper layers of the ocean,

while the sound of the bloop was recorded considerably deeper in the Pacific.

[narrator] Because hydrophones had originally been set up

to detect enemy submarines, researchers wonder

have they now detected a new top secret military technology.

The scientists reach out to U.S. Navy intelligence officers,

to see if they can identify the sound,

or maybe shed light on any new technology that was being used in the oceans.

But, they deny any knowledge of potential operations, that could've caused it.

[narrator] Researchers of the National Oceanic and Atmospheric Administration,

or NOAA,

analyzed the visual representation of the bloops audio frequency,

and then compared it to other marine sounds that have been identified,

to see if they can find a match.

But, when they look at the spectrograms, side by side,

the bloop appears to resemble sounds made by marine mammals underwater.

But, what animal would be large enough to create such a loud sound?

[narrator] The Blue Whale is the biggest mammal to have ever lived.

They can grow up to 100 feet long,

and their calls can reach 188 decibels.

That is loud enough to burst a human eardrum,

and their calls have been heard and recorded from hundreds of miles away.

[Clarke] But, the bloopers recorded by hydrophones that were thousands of miles apart.

By using Blue Whale sound production dimensions,

researchers discovered, for an animal to make a sound that could travel that distance,

the creature would have to have been over 250 feet long.

If the sound was made by an animal, it was something bigger than a Blue Whale.

[narrator] Each year, new deep sea creatures are being discovered,

and the researchers wonder, was the bloop made by an undiscovered marine species?

It's entirely possible. We're learning more about new marine life all the time.

For example, there are only a few giant squid,

that have ever been seen reaching 60 feet in length.

[narrator] But, without any more evidence,

the researchers start to consider supernatural theories.

[Morgan] They wonder if they have discovered the legendary kraken

or the colossal Megalodon.

[MacFerrin] Finding something like that would be amazing.

It's every scientist's dream.

But, there's really no evidence to support these wild theories.

But, if it wasn't the mysterious creature, then what could it be?

[narrator] In 2010,

scientists doing an acoustical survey in waters near the South pole,

take another look at the source of the mysterious bloop.

NOAA researchers reanalyze the hydrophone data,

and are able to triangulate the bloops origin, to Antarctica.

[Clarke] Researchers from the Pacific Marine Environmental laboratory

have been recording underwater sounds regularly in Antarctica since 2005.

So, now there's a new, huge database of sounds, they can use to compare with the bloop.

When they slow the bloop down to real-time speed,

researchers feel like, maybe we've got a match here.

[narrator] In the Southern ocean, the main source of underwater sound, is ice.

crashing, breaking up, and collapsing from the huge ice shelves

and glaciers, that surround Antarctica.

We now know that there's tens of thousands of these ice quakes that happen every year.

They didn't know this when the bloop was first recorded.

And, when they're played in real-time, not sped up,

these icy audio signals appear very similar, to the bloop.

[narrator] The bloop was most likely created, somewhere between the Bransfield Strait,

and the Ross Sea.

At the right frequency, and perhaps along the deep sound channel in the Pacific,

the bloop travelled thousands of miles, and was just by fluke,

recorded for the first time.

[Morgan] So, scientists think that this bloop sound was actually,

thousands of gigatons of ice, crashing explosively, into the sea,

but sped up 16 times, that enormous, thunderous roar,

sounds just like a big drop of water.