Original subtitles

NARRATOR: A burning giant, torching everything in its path.

- What has created this flaming cloud of oblivion?

NARRATOR: Disaster strikes a treasured forest

near a mythical mountain lake.

- This landscape looks apocalyptic!

NARRATOR: A threatening radioactive area comes back to life.

- This does not make sense.

NARRATOR: And an ancient icon disappears.

- It looks like it was just vaporized.

NARRATOR: Everywhere we look on our planet,

there's evidence of the past.

In nature...

in buildings...

in relics.

Each holds a mystery that technology now allows us to see from above.

What new secrets are revealed?

Since time began, disasters are something that human civilizations

have always struggled to comprehend.

But sometimes, the best way to understand a disaster

is to decipher it from above.

Nestled in the shadow of Northern California's mountains,

just outside city of Redding,

the view from above reveals a terrifying sight.

MAN: (on video) Oh my God!

- It honestly looks like the gates of hell have opened.

- It looks like the earth is opening up and it's barfing out fire.

NARRATOR: But there's something strange about this fire.

- The flames and smoke are behaving in a way that are very peculiar.

- I'm absolutely terrified.

It's literally spiralling out of control.

- What on earth has created this flaming cloud of oblivion?

NARRATOR: In July of 2018,

just 20 kilometres west of Redding, California,

a massive wildfire broke out and bore down on the city.

- The fire was burning for three or four days.

It was around 20,000 acres when it finally hit Redding.

NARRATOR: The colossal blaze burned through the west side of Redding

to the edge of the Sacramento River.

High winds sent embers flying across the water,

spreading the fire before many of the residents could escape.

RALEY: The fire spread was so rapid

that it made it difficult for residents to get out in time.

And very quickly became apparent

that we were, sort of, in a grave situation.

KOUROUNIS: Inside Redding, the massive wall of flames

created temperatures up to 2,700-degrees Fahrenheit,

hot enough to melt steel.

NARRATOR: Even more incredible, a churning vortex of fire appeared,

1,000 feet wide and towering almost 18,000 feet into the dark sky.

- The size of this blaze is mind-blowing.

But it's twisting. So, what's happening here?

- When I see a fire of this size with these immense plumes of smoke,

my first thought is, was this some kind of explosion?

NARRATOR: Could an explosion be behind

this terrifying tower of flame?

Perhaps there's a clue thousands of kilometres away in Beirut, Lebanon,

where a massive blast shook the city in 2020.

Here, a port storing almost 3,000 tonnes of ammonium nitrate

caught fire, triggering a disaster.

- The fire apparently spread to some fireworks

that were being stored on the site

and then there was this huge explosion...

..that resulted in massive plumes of smoke that stretched

more than 700 metres into the air.

GUY: The shockwave caused over 200 casualties

and was felt over a hundred miles away.

- Who can forget that explosion?

I mean, after that blast, that whole area looked like hell on earth.

YATES-ORR: Images of the explosion show

that this happened in an industrial area.

NARRATOR: Could the fiery vortex in Redding

been produced by an explosion?

- But where would the explosives come from?

- In the suburbs, it's not likely that you're gonna have

huge amounts of flammable or explosive materials.

KOUROUNIS: I doubt this fire is the result of some kind of an explosion.

- So what could be causing this massive fire?

NARRATOR: Perhaps the answer lies in the enormous columns of smoke.

- The shape kinda reminds me of the huge columns of ash

you see from erupting volcanoes.

YATES-ORR: There are 20 volcanoes in California,

and seven of them are likely to erupt again.

NARRATOR: The most recent eruption was less than

75 kilometres from Redding.

- The last substantial eruption in California was Mount Lassen,

and that was all the way back in May 1915.

That was a disaster.

KOUROUNIS: Over four days, the volcano spews molten lava and rock,

destroying everything in its path.

- The effects of Mount Lassen's eruption

were felt for hundreds of miles, including in Redding.

NARRATOR: Geologists still believe the chances of another eruption

at Mount Lassen are high.

Could the volcano be the source of Redding's mysterious vortex of fire?

- If we compare volcanic ash columns to the giant plumes of smoke

seen in Redding, they may seem similar.

But when you take a closer look, it doesn't look like ash

filtering in from a nearby volcano.

NARRATOR: And the view from above reveals the vortex of fire's path

is coming from the opposite direction of Mount Lassen.

- So, what could be causing this massive fire?

- When you look closely at the footage,

you can't help but notice this extraordinary thing.

It seems there's a rotation in the flames.

- I've seen spinning activity like this many times.

It reminds me of the rotation you'd see in tornadoes,

waterspouts, and even dust devils.

- California definitely has the right conditions

to produce dust devils. So, could this fire be the result

of two converging phenomena, a dust devil and a fire?

KOUROUNIS: Dust devils are vortices that form when rising pockets of air

above a hot and dry ground create an updraft that begins to rotate.

NARRATOR: And devils like these aren't always made of dust.

- Back in 2019, a huge "coal devil" was captured on video

at a coal mine in Elkhorn, West Virginia.

KOUROUNIS: The vortex acts as a low-pressure centre,

drawing in warm air,

including debris like dust, coal, or even hay,

and then spitting it up and out.

- While they rarely do any real damage,

the winds in these devils can reach more than 100 kilometres an hour

and they could be 300 metres tall. That's like 1,000 feet!

- A thousand-foot-tall spinning cloud of anything

is not my idea of a good time.

- But none of these so-called devils contained any fire within it,

which is what we see in the Redding disaster.

So, could this be the result of something else?

NARRATOR: Perhaps there's a clue on the other side of the country,

in Lexington, Kentucky, where a bourbon distillery

faces a sudden disaster of its own, a lightning strike.

- In July of 2019, thunderstorms hit Lexington.

And in the middle of the night, the nightmare began.

- Nine million litres of bourbon spilled out onto a retaining pond

and that mixture of fire, water, and alcohol on the surface,

created what's called a fire whirl.

- Nine million litres of bourbon going up in flames.

Now, I call that a tragedy beyond words.

NARRATOR: A fire whirl is a lot like a "devil",

but the fire creates its own whirlwind,

spawning flaming vortices.

- A fire whirl can grow much taller than a devil,

up to 3,000 feet in height.

- That's monstrous!

NARRATOR: Does this explain what the fiery vortex in Redding really is?

- It's all about the height.

The Empire State building is over 1,450 feet high.

What we're seeing in Redding is way taller than that,

almost 18,000 feet!

That is the equivalent of almost 12 and a half Empire State Buildings!

- Way too tall to just be a fire whirl.

NARRATOR: So, what strange forces can be conjuring

this gigantic twisting pillar of smoke and flame?

- In terms of its size and its rotation,

what it most resembles, of course, is a tornado.

But what I know about tornadoes is that they're not usually flaming.

KOUROUNIS: A tornado starts up in the atmosphere where a violent storm

forms a condensation funnel made of water, dust, and debris.

Winds can move up to 250 miles per hour

and these monstrous storms can tower at 80,000 feet.

Whereas, a fire whirl begins on the ground

when a whirl of wind combines with a fire and moves up.

NARRATOR: Perhaps the answer can't be found from above,

but rather, with a closer look from within?

RALEY: I was helping evacuate two subdivisions.

I'd say 40% of the homes were on fire.

It was very windy. It was dark, very smoky.

Visibility was terrible.

I could barely see ten feet in front of my truck.

My vehicle started to get struck with debris

and it was shaking pretty violently.

It was pushed off the road and all the windows blew out.

That's when I felt like something was different.

I've been firefighting for 28 years,

and I had absolutely no idea what was happening.

NARRATOR: What was it that stunned the desperate firefighters

in Redding?

- It's possible that a fire whirl could grow so tall

that it's able to reach into the clouds and create a storm.

What we could be looking at...

is a firenado.

NARRATOR: Over 12,000 kilometres away, in Canberra, Australia,

an eerily similar swirling cloud of smoke and fire

is filmed in 2003.

KOUROUNIS: It started out as a blazing brush fire

that developed a windstorm within it.

The Canberra fire whirl got so big,

it generated a convective system

that moved up into the clouds and produced tornado-like winds

at 250 kilometres an hour.

It was called a fire tornado, or a firenado.

- (dramatic music)

NARRATOR: Like a tornado, the phenomenon in Canberra

ripped apart the landscape, but it also burned everything in its path.

- The destruction was unparalleled,

and it was the only firenado ever recorded.

- Could this be what we're seeing in Redding, California?

KOUROUNIS: In Redding, buildings were demolished

and trees were uprooted.

RALEY: All the bark was stripped off of the trees,

in a specific path,

all the gravel on the shoulder of the roads was stripped.

Large power poles were sheared off.

It was a terrifying moment for sure.

Winds inside the burning funnel were estimated to be

more than 230 kilometres per hour,

making it equivalent to an EF3 tornado.

NARRATOR: And that can mean only one thing...

What we're looking at here in Redding is a firenado.

- The firenado put it on everybody's radar

that these things are very possible and they're real.

It was an eye-opener for everybody.

- It's hard to imagine combining two of the world's most destructive

natural disasters into one event,

but this actually happens.

A raging forest fire can actually spawn and create a tornado of fire.

NARRATOR: The fire in Redding was finally contained

at the end of August 2018, five weeks after it started.

230 acres were destroyed,

costing $1,600 billion in damages.

- A firenado is very powerful, and very destructive.

I probably won't see anything like that, ever again.

At least I hope I don't.

NARRATOR: But the Redding fire would not be the last.

In 2020 alone, there were three wildfire firenadoes,

and there may be more to come.

- Since the Earth's temperatures are increasing, so will the chances

of more firenadoes forming and wreaking serious havoc.

- So, if you ever find yourself near a large, out-of-control fire

and it gets extremely windy, you've got two choices,

excuse yourself quickly

or pull out your camera and start filming.

But I suggest the former.

NARRATOR: From fiery disasters to the mysterious forces of the ocean,

sometimes the disaster isn't what you can see, but what you can't.

Like here, roughly 10,000 kilometres away

in the Mediterranean Sea.

This is Malta's Azure Window

a 28-metre-tall limestone arch located on the island of Gozo,

- It's absolutely stunning.

NARRATOR: First appearing in the early 1800s

after the collapse of a sea cave, this natural formation

has since become a major attraction for millions of tourists.

- It became almost an emblem of the Maltese islands.

NARRATOR: But on this day, it has completely vanished.

- Poof!

BELLINGER: Now you see it. Now you don't.

- I mean, it looks like it was just vaporized.

NARRATOR: What could have triggered this massive arch of rock

to collapse into the waters of Dwerja Bay?

BELLINGER: How does a giant stone arch just disappear like that?

And who or what could be responsible?

- It would have to be really, pretty powerful,

because the history of Malta has never been short

of explosive conflict.

NARRATOR: Over the centuries, the Azure Window

has survived countless disasters.

- Malta's location makes it a strategically crucial site,

and throughout its history, huge battles have been fought

for control of the island.

NARRATOR: And few were more destructive

than during the Second World War,

when Axis Forces attacked the island nation.

- At the time, Malta was the most bombed area on the planet.

NARRATOR: Despite these massive bombardments,

the Azure Window survived.

- If it could survive the Axis attacks,

what could possibly take it out?

- Whatever happened had to be powerful enough

to crumple a massive piece of rock

that years of direct threats did not.

NARRATOR: Perhaps the answer lies

with another nation's beloved symbol almost 9,000 kilometres away,

in Brazil, where a familiar figure stands above Rio De Janeiro.

KOUROUNIS: The statue of Christ the Redeemer

is recognizable around the world.

YATES-ORR: The 30-metre statue has been standing for almost 100 years.

- And one of the key things it faces being so high?

Lightning.

It's hit around 3 to 5 times every year.

- And it's not the only one.

Many other landmarks around the world are regularly hit

with the blasts from above.

NARRATOR: Could a lightning strike be behind

the sudden disappearance of the Azure Window?

KOUROUNIS: Malta is a country with a consistently hot climate,

so thunderstorms are a regular occurrence.

The main island of Gozo was once walloped

with over 200 lightning strikes in one day.

NARRATOR: A closer look at the images of the Azure Window,

reveals another clue.

GUY: Looking closer at the rock,

I can see what would appear to be a large crack.

Could that be a mark left by a lightning strike?

- When a lightning bolt strikes rock, it can sometimes leave behind

strange formations known as fulgurites,

glassy scars that look like tubes.

NARRATOR: There doesn't appear to be any evidence

of fulgurites in the limestone rock.

So, a lightning strike is clearly not responsible.

- What else can cause this kind of colossal destruction

in such a localized place?

- It's like something fell from the sky and smashed it to pieces.

Could the Azure Window have been taken out by a meteorite?

- It wouldn't be the first time.

One of the oldest rogue meteorites on record

was the Peekskill meteorite that crashed into a parked car in 1992.

- Every year in Malta, the Perseid meteor shower hits Dwerja,

known locally as the Tears of Saint Lawrence.

GUY: But the Perseid meteor shower happens in August

and the Azure Window was destroyed in March.

NARRATOR: Meteorites fall throughout the year.

In fact, some 17,000 hit Earth annually.

Could one of these have levelled the Azure Window?

YATES-ORR: In the meteor calendar for Malta

there was no known meteor activity in Dwerja Bay on March 8, 2017.

NARRATOR: So, if not from above,

is it possible that disaster struck from below?

- Just after 8:30am on the day of the Azure Window's disappearance,

a seismic signal was recorded... on Gozo.

- Does that mean that a sudden earthquake

is behind the disappearance?

NARRATOR: 8,000 kilometres away in Puerto Rico,

a 2020 earthquake may provide a hint.

- On January 6, 2020, a 5.8 magnitude quake hit,

with an epicentre only 6 kilometres away from the island.

NARRATOR: And here, another natural landmark took a major hit.

- Puerto Rico is home to a rock formation

similar to the Azure Window,

known as Punta Ventana, or "Window Point".

- You'd think something like this would be around forever,

but the quake was too much for it to handle.

NARRATOR: Just like the Azure Window,

Punta Ventana vanished.

So, could an earthquake be the culprit on Gozo?

- Malta isn't an earthquake hotspot,

but it's still very susceptible to large quakes.

The earliest recorded earthquake happened in 1693

with an estimated magnitude of 7.4.

NARRATOR: That quake struck Sicily,

170 kilometres away from the Azure Window.

- There are records of landslides and building collapse

from the shockwaves that hit Malta.

- And in more recent times, a magnitude 3.0 earthquake

hit 120 kilometres off the coast of Malta.

YATES-ORR: The Azure Window withstood those quakes,

but could another be behind its disappearance?

NARRATOR: A seismic signal recorded the day the arch disappeared

reveals another clue.

- That signal had a magnitude of approximately 1.5.

- That's not a very big quake.

- That's what we call a microearthquake,

you'd barely feel it.

It doesn't seem possible that something so small

could take out a massive rock formation.

NARRATOR: What else could be behind the disappearance

of the Azure Window?

Perhaps another view from above can reveal other clues.

GUY: About 90 metres away from where the Azure Window was

is the blue hole.

A sinkhole measuring 10 metres wide.

NARRATOR: And it's not the only one.

RISKIN: When you take a wider view of the area,

you notice another nearby sinkhole,

a huge lagoon known as the Inland Sea.

CARUANA: When you look at it from the air,

it has this almost perfectly circular shape

that is really quite striking.

You can't appreciate it the same way

when you look at it from the ground.

NARRATOR: Could a sinkhole be the cause

of the Azure Window's disappearance?

GUY: A sinkhole is the result of erosion.

Water seeps into the bedrock and dissolves it,

creating these cavities and caves which cause collapse

from the surface above.

RISKIN: They can be big enough to draw in a vehicle

or even swallow huge sections of forest.

- Sinkholes can also happen underwater.

It's plausible that an underwater sinkhole opened up

and the Azure Window was sucked in.

- I mean, this sounds like an underwater black hole.

NARRATOR: Has the Azure Window collapsed into a hidden sinkhole

in the seabed?

A closer view from above reveals

the base of the pillar is still quite visible,

lying just beneath the ocean waves.

With the remains of the arch so close to the surface,

a hidden sinkhole is clearly not the source of the collapse.

So, what did lead to the demise of this famed Maltese icon?

To solve the mystery, we must investigate the view from above,

below.

- The initial idea was to gather a little bit of an understanding

of what had happened to try and make sense

of the collapse event itself.

NARRATOR: Is it possible the secret to solving this mystery

lies just beneath the ocean's surface?

- It was breathtakingly beautiful,

the rock was still quite fresh, so it was almost shining underwater

with this really bright white colour.

The base of the pillar had collapsed,

but for the most part, it was still there.

It was really quite eroded towards the top close to the surface.

You could see that it was tapered.

NARRATOR: To discover what happened here, Dr Caruana's team

employs a technology known as photogrammetry.

WOOD: The process involves taking many, many photographs,

which overlap one across the other to create the 3D model.

- It was quite a challenge to do

because the site is really quite large.

But over the months and years, we managed to do just that.

NARRATOR: And the 3D model reveals a crucial clue.

WOOD: The base of the column was suffering

from some rather serious erosion.

This was demonstrated very, very clearly through the 3D model.

You could see the tapering of the base of the arch

until it reached the surface. It was maybe, at the surface,

not more than a couple of metres wide, if that.

NARRATOR: The model also reveals how the arch met its demise.

- The collapse took a matter of seconds.

The bridge of the arch collapsed vertically downwards

upon losing support from the pillar.

The bridge just fell right where it was,

vertically downwards,

and it's now dispersed underneath the cliff.

- It's the inevitable process of nature.

It's the constant pounding of the north-westerly winds and seas,

which can be very, very violent on this part of the island.

- On the day of the collapse, there were reports of high winds

around Gozo.

NARRATOR: Wind speeds over 70 kilometres per hour,

and waves 3 metres high were reported.

This battering of wind and sea coupled with a weakened structure

lead to the arch's collapse.

- The Azure Window wasn't destroyed by a literal storm,

but it was destroyed by a perfect storm of unfortunate circumstances.

- In other words, it collapsed because of a combination of wind,

waves, and erosion.

NARRATOR: But what about the mysterious earthquake signal?

- The timing is so close to the Azure Window's disappearance,

it makes a lot of sense to think they've got to be connected.

NARRATOR: And they are.

In 2018, researchers proved that the signal was indeed

the result of the Azure Window hitting the sea floor.

YATES-ORR: That signal was the voice of the Azure Window as it fell.

NARRATOR: After falling prey to decades of erosion,

what does the future hold for the Azure Window?

BELLINGER: An iconic feature, beloved above the waters,

will soon take on a new purpose below.

- As a reef, the Azure Window will become an important feature

in sustaining the underwater life in Dwerja Bay.

- It'll also become a different type of attraction

for a different type of tourist.

CARUANA: Every time I dive the Azure Window remains,

I'm left in awe at the beauty

that nature can craft as it continues to mould the landscape.

It is a continuous process.

It has found new life under the sea.

NARRATOR: While some disasters hide beneath the waves,

others are unseen and present unthinkable dangers.

Chernobyl, Ukraine,

the site of the world's most infamous man-made disaster.

- The explosion was the largest uncontrolled radioactive release

into the environment ever recorded.

- To this day, it is the world's worst nuclear disaster.

NARRATOR: Now, more than 35 years after the catastrophe,

the reactor is in ruins, and the surrounding land, abandoned.

- I have been to Chernobyl and it is hands down

the creepiest place that I have ever experienced.

Everywhere you look, the buildings are crumbling and decaying.

NARRATOR: And now, startling new research from above

reveals a lethal threat.

A drone measuring radiation around the site

discovers something frightening. - What is that?

- We were able to detect a very highly localized

and intensely radioactive area.

- Finding a spike like this decades after the explosion is alarming.

NARRATOR: And even more unsettling, its location.

An abandoned village called Kopachi.

- Kopachi wasn't an area where we were expecting to see anything.

You would think all the high levels of radiation

would be close to the reactor.

- I wanna know, why is there radioactivity right there?

- Could this radioactive hotspot in Kopachi

be a contaminated fragment thrown from the original explosion?

NARRATOR: Perhaps we can find a clue 6,500 kilometres away

and over 100 years in the past.

- Before the nuclear age, human beings were still perfectly capable

of causing sudden mass destruction.

And one of the biggest disasters was in Halifax, Nova Scotia.

HOFFMAN: During the First World War, a munitions ship

carrying almost 3,000 tonnes of explosives,

collided with another in the harbour.

The resulting blast was the largest human-made explosion

up until that time.

- It was the equivalent of about 3 kilotons of TNT.

The shockwave was just huge,

it shattered windows up to 100 kilometres away,

and the anchor from the exploding ship

actually flew 4 kilometres before it hit the ground.

NARRATOR: Is it possible a piece of debris from the Chernobyl explosion

is the source of the mysterious radioactive hotpot near Kopachi?

- The explosion was incredibly powerful.

I mean, it was like nothing the world had ever seen before.

- It was a moment that changed history.

NARRATOR: On April 26th, 1986,

two massive explosions blasted the 1000-tonne roof

off nuclear reactor number 4.

- The explosion blew radioactive fuel particles into the air

in every direction, and then caused a massive fire

of radioactive materials at the site.

NARRATOR: But was the explosion big enough to be the source

of the mysterious radioactivity.

- Given that Kopachi is more than 4 kilometres from the epicentre

of Chernobyl, it's pretty unlikely that the hotspot we are seeing

comes from that explosion.

- But it could be possible.

Because that's almost as far the Halifax explosion

threw that massive anchor.

What we need is more information.

NARRATOR: Another view from above reveals another clue,

a former secret Soviet installation just south of Kopachi.

- What we know is at the time of the explosion, the Chernobyl area

was actually the site of two military installations.

NARRATOR: One of these was a missile defence station,

the other, a secret military base.

According to one news report, at least three rockets

armed with nuclear warheads were present.

But after the Chernobyl explosion, they had to be moved... and quickly.

HOFFMAN: We know from previously classified Soviet records

that dozens of missiles were quickly loaded onto trucks.

- Could it be possible that during the chaos after the explosion,

some of the nuclear warheads were moved to Kopachi?

NARRATOR: And if so, why would the Russians hide them there?

- Perhaps it's not the Soviets hiding nukes in Kopachi.

NARRATOR: When the Soviet Union fell in 1991,

just 5 years after the Chernobyl disaster, it left Ukraine

with the world's third largest arsenal of nuclear weapons.

It's believed they surrendered all of these

in return for security from the west.

- But did the Ukrainians return everything?

Could they have kept some weapons-grade materials

for themselves?

- This might explain why the Russians have showed this,

kind of, bizarre interest in Chernobyl when they invaded Ukraine.

NARRATOR: In the spring of 2022,

Chernobyl was occupied by the Russians, and no one knows why.

- Russian soldiers have been seen digging trenches there.

It's hard to understand why they would want to gain access

to an abandoned nuclear power plant.

Why would the soldiers take such a daunting risk?

- One possibility is that they're searching for hidden

and highly valuable radioactive material.

NARRATOR: What nuclear secrets were the Russian soldiers hoping to find?

- Plutonium is the primary element used to produce nuclear weapons.

Is it possible that this valuable resource

can still be found at Chernobyl?

- The possibility that somebody could be making bombs from this

is really frightening.

- Now if that were true, that of course,

could lead to a third World War.

NARRATOR: Could this really be the source

of the radioactive readings near Kopachi?

- Whatever it is, its obviously not supposed to be there.

NARRATOR: So, how did it get there, and what is it?

- Could this hotspot be the indication

of leftover weapons-grade plutonium?

- An RBMK reactor such as Chernobyl

is primarily for breeding weapons plutonium.

NARRATOR: Is this why the Russians occupied Chernobyl

in the early days of their invasion of Ukraine?

- If someone's trying to create bombs from plutonium,

the world needs to be paying attention.

- The first nuclear bombs were dropped in 1945 in Japan,

killing tens of thousands of people and devastating two entire cities.

It's the only time that nuclear weapons have been used in warfare,

and hopefully the last.

NARRATOR: After a thorough scan over the entire area

surrounding the hotspot,

results from the research drone are encouraging.

There are no signs of plutonium.

- That's a relief. But we still don't know

what the Russians wanted with Chernobyl.

NARRATOR: Could it simply be a question of location?

- Chernobyl sits right on the shortest route

between Belarus and Kiev.

That, of course, is Ukraine's capital.

Now, that makes a potentially useful line of attack

for invading Russian forces.

NARRATOR: Their presence at Chernobyl

may have nothing to do with nuclear materials,

but what does that mean for the hotspot?

- Since there's no rogue plutonium in Kopachi,

what else is there that could create so much radiation

35 years after the explosion was cleaned up?

NARRATOR: Maybe the second worst nuclear disaster in history

can offer a clue?

Almost 8,000 kilometres away, in Fukushima, Japan.

WALTERS: In 2011, there was this massive tsunami

which completely overwhelmed the Fukushima Nuclear Power Plant,

and that caused three nuclear meltdowns,

three hydrogen explosions,

and as a result, it released a huge amount of radiation.

- A 20-kilometre radius around the site was evacuated,

but some people had to remain in and around the plant

to stabilize the disaster site.

NARRATOR: To manage radioactive debris,

remote control machinery was used to find

and store the deadly material.

- Over $150 billion has been spent on the containment efforts

at Fukushima, and there's hope that that site

will be completely decontaminated by the year 2050.

- Chernobyl, frankly, was not so lucky.

You know, scientists say that it's gonna take at least 20,000 years

before the site becomes habitable again.

- And that's partly because the cleanup at Chernobyl

was not nearly as organized as Fukushima.

KOUROUNIS: The immediate aftermath of the Chernobyl explosion

was a time of intense chaos and fear.

The cleanup has been massive, but it was not entirely well-managed,

given the emergency circumstances.

- Evacuations weren't immediately ordered,

and so thousands of people unknowingly went about their days

while being exposed to really dangerous levels of radiation.

NARRATOR: When evacuation orders finally went out,

panic set in.

- People left so fast, you can still see items sitting

where they were dropped haphazardly over three decades ago.

GUY: It looks like time just stopped.

NARRATOR: With the residents fleeing to safety,

the deadly site of the disaster had to be fought with full force.

WALTERS: After the explosion, you have thousands of people,

who risked their lives working as what was known as "liquidators".

And their job was to clean up all those deadly materials.

The most disturbing thing for me about the Chernobyl disaster

wasn't just the kind of reckless managerial incompetence

that led to it.

It was the bravery of those who had to clean it up,

who knew that this was going to lead to their deaths.

MARTIN: Due to the magnitude of the accident and the haste in which

the liquidation activities were performed,

no actual records were able to be kept.

There are so many unknowns.

- Given that the Chernobyl cleanup was such a mess,

could this hotspot be the result of a long-forgotten pile

of radioactive waste?

NARRATOR: To solve the mystery, researchers have little choice

but to continue their investigation... on the ground.

- We couldn't just leave it. We had to go in as scientists

to work out what was causing this kind of anomaly to exist.

- For me, studying and collecting the radioactive data

from the distance of a flying drone is good enough.

NARRATOR: Soon, the team makes a dangerous discovery.

MARTIN: Our personal dosimeters started to go off.

The beeping starts, everything starts flashing.

- I'm not so sure how much farther I'd walk

once all the radiation alarms go off.

- It was only then we actually realized,

"Ah, this is the radioactive hotspot that we had seen from above."

NARRATOR: So what deadly force continues to lurk

in this forbidden landscape?

- We saw this kind of bowl-shaped depression

and some large metal structures

inside three large, metallic, iron hoppers.

As you then get progressively closer,

your dosimeter starting to flash red, everything started to beep.

Your Giger counter starting to find radiation that are too high

for it to actually measure.

And that's when we actually found this hotspot.

NARRATOR: What are these strange metal structures,

and why are they giving off so much radiation?

- Kopachi was a small farming village outside of Chernobyl.

These metal hoppers would normally have been used to bag animal feed,

but were most likely sequestered by the liquidators

for their radioactive dirty work.

NARRATOR: Readings indicate that it's nuclear fuel waste,

radioactive material left accidentally in the hoppers

for over 35 years.

The discovery solves the mystery of the hotspot,

but the researchers still have more ground to cover.

- This site of nuclear material was formerly unknown

to almost all of the authorities within the zone.

Hence, there is now an even more pressing need to get back out there.

- Mapping the Chernobyl site is important,

because with this information,

local authorities can accurately isolate these dangerous no-go zones,

making the area safer for future researchers,

tourists, and even redevelopment.

NARRATOR: Experts may have deemed the exclusion zone unliveable

for 20,000 years, but it could have a surprisingly "clean" future.

- By utilizing the areas already-built power network,

Ukrainian officials are considering the construction

of solar energy farms on the least radioactive areas

of the exclusion zone.

- So, because of the deadly environmental disaster at Chernobyl,

a newer and cleaner energy source

may find itself a permanent home there.

- Here's hoping.

NARRATOR: From a barren man-made disaster zone

to pristine alpine slopes,

some catastrophes seem to come out of the blue.

In the Italian alps, nestled beside the Dolomites,

lies the idyllic Lake Carezza.

- Crystal clear waters, stunning mountain views.

I mean, this place is absolutely gorgeous.

NARRATOR: But in the fall of 2018,

the surrounding woodlands were transformed

into a disaster beyond comprehension.

- My God, these trees have been massacred.

It looks like a crime scene.

- It's like a graveyard of trees.

There's something really eerie about this place.

- This landscape looks apocalyptic.

NARRATOR: And the view from above reveals something strange

about the destruction.

- Huge swaths of trees have been flattened,

but right beside them, are others completely untouched.

- When you look at the live trees versus the dead trees,

it almost seems like someone or something

is choosing what to destroy.

NARRATOR: What powerful force could be so destructive

and yet so selective?

- Could it be some kind of disease?

I mean, that might explain why only some sections of trees

have collapsed but not others.

NARRATOR: How did a disease make its way into this remote forest?

Perhaps there's a clue in Italy's past.

- Researchers believe that one possibility reached Italy

by accident in the 1940s.

RISKIN: There's a fungus called Heterobasidion annosum.

NARRATOR: In the United States, this tree killer

causes $1 billion in damages every year.

But what is it doing in Italy?

- Genetic analyses showed this probably came over from the US,

most likely with troops during the Second World War

hidden within their wooden equipment.

It spread throughout coastal Italy since.

Sometimes fungi aren't that fun.

NARRATOR: But these trees are in the mountains,

far from Italy's coast.

So, what else could be behind this obliteration?

Over 8,000 kilometres away, another tree killer could provide a clue.

- For decades, one tiny little creature

has been devastating the forests of the American West.

RISKIN: Bark beetles. Since 2005,

they've destroyed millions of acres of forest.

- We're talking up to 100,000 trees a day

getting taken out by these little insects.

They're really small, but they can cause seriously big problems.

- Talk about an ecological nightmare.

- And it could be getting a lot worse.

- Climate change has led to an increase in the populations

of bark beetles, so it's indirectly responsible

for what many people call the biggest insect outbreak

in the history of the planet.

- Could a tiny insect be responsible for a disaster of this size?

NARRATOR: A closer look from above reveals that this is unlikely.

- These trees look like they were healthy before they were flattened.

KOUROUNIS: There's no evidence of insect infestation.

So what's going on here?

- What on earth could have done this?

NARRATOR: Perhaps the answer is not on earth,

but rather, in the skies?

- When you look closely, there appears to be

some kind of smoky haze in the air.

NARRATOR: What is this mystery mist?

A few hundred kilometres away, in another part of northern Italy,

there may be a clue.

HOFFMAN: In 2017, the town of Turin, Italy,

suffered an enormous fire that burned over 1600 hectares of forest.

- That's over 3,000 football fields.

The smoke from the fire lingered in the air for weeks

as the fire burned itself out.

- Could this be the source of all that destruction at Lake Carezza?

Is it possible that this could simply be the aftermath

of a raging forest fire?

- You know what they say? When there's smoke, there's fire.

- But it doesn't look like a forest fire.

When you look at it from above, it doesn't show any individual trees

that are burnt or burning.

GUY: Whatever is creating that smoky substance,

it's not the trees themselves.

NARRATOR: So what is creating the haze above the forest?

- There have been rare circumstances in the past where smoke exists

without any evidence of fire, at least not any fire above ground.

NARRATOR: Could the secret to solving this mystery

lay buried deep below the Earth's surface?

Perhaps the key to solving this mystery is not from above

but below.

A disaster from the past, almost 7,000 kilometres away,

could hint at the answer.

HOFFMAN: In 1962, the town of Centralia, Pennsylvania,

tried to clean up a landfill by setting fire to it.

It didn't go exactly as planned.

The fire was not properly extinguished,

and it travelled into the unsealed opening of a strip mine.

NARRATOR: Centralia once boasted 14 active coal mines,

interconnected by a labyrinth of tunnels.

- At the time of the fire, people thought the blaze

would burn out quickly, but it spread to all of Centralia's mines.

All the trees in the town died.

The ground turned to ash

and people left for fear of carbon monoxide poisoning.

HOFFMAN: Now, Centralia is almost a ghost town.

NARRATOR: 15 square kilometres in size, and at points, 90 metres deep,

the fire proved impossible to put out.

GUY: Six decades later, the fires are still burning.

- And experts believe that the coal supply there is so large

that it could take another 250 years for it to burn out.

But is that what is happening around Lake Carezza?

- Unlike Pennsylvania, the smoke near Carezza

is not escaping from exit points in the ground.

KOUROUNIS: And looking closer at the smoky haze,

the way it's hanging in the air, makes me question something.

Carezza is a mountainous region, and the weather can change rapidly.

The haze is most likely not smoke, but mountain fog.

Obviously, fog can't do damage to mountain forests,

so what other options do we have?

- When I think of other disasters in the mountains,

I think of violent acts of nature, avalanches, landslides.

- Mountain landslides can cause a massive death and destruction.

NARRATOR: Disasters like landslide 8,500 kilometres away

hit rural Washington.

- In 2014, the Oso landslide in Washington State

propelled mud and debris over 2.6 kilometres.

- This disaster came thanks to a deadly combination

of unstable land and a massive amount of rain.

KOUROUNIS: An estimated 10 million cubic metres of material

turned into a tsunami of mud.

In some places, the slide was over 21 metres deep.

- The sudden slide hit an unsuspecting neighbourhood below,

killing 43 people.

- A landslide could explain why some trees have fallen

while other ones haven't,

and there's evidence of soil and rocks around the broken trees.

NARRATOR: But the mountains around Lake Carezza show no sign

of a typical landslide carnage,

so what other forces could be at play?

- Perhaps the pattern of destruction,

the way the trees have collapsed, can offer a clue.

- Seeing so many trees toppled like this, I can't help but wonder

if a tornado is responsible.

They're certainly capable of colossal damage like this.

NARRATOR: Tornadoes are uncommon in Italy,

but one touched down in Venice in 2015.

And in 2021, 12 twisters were reported in Sicily.

- Typically, when most people think of tornadoes,

they think of flat ground, like Kansas,

but they actually can happen almost anywhere.

In some cases, mountains may actually help tornadoes form.

NARRATOR: Just like in Virginia in 2011,

when two tornadoes formed at elevation on Draper Mountain.

- You've really gotta wonder how a tornado could really get moving

with all these big mountains in the way.

- Some scientists believe that the change in elevation

due to the storms crossing the ridge,

may have caused the updraft to rotate even faster.

It's called vorticity stretching.

- Super tornadoes, is that what could have happened to Carezza?

That would explain why the trees look like scattered matchsticks.

NARRATOR: But this destruction doesn't match

the pattern usually associated with tornadoes.

KOUROUNIS: Typically, with a tornado, there's a single funnel

coming from the base of the storm that travels along one path.

- There's no single path of destruction here.

What we're seeing is large swaths of trees torn out in multiple areas.

- It's almost like several tornadoes descended all at once.

- When I think about it, there is another extreme weather event

that is a possibility.

We could be looking at the aftermath of a cyclone.

Unlike a tornado, which is tall and contains a funnel cloud,

a cyclone is a wider, rapidly rotating low-pressure storm system.

NARRATOR: A cyclone contains a spiral of high winds

and multiple storms which carve numerous paths of devastation.

- This may explain why the destruction was in

several different sections in the forest.

- To know for sure, we'd need to see what the weather was like

in and around Carezza at the time of the disaster.

NARRATOR: In 2018, Cyclone Vaia struck northeast Italy,

including Lake Carezza.

Wind gusts reaching almost 200 kilometres per hour

and destroyed 8 million cubic metres of trees.

- That's equivalent to Italy's entire harvest of wood for a year.

It's incredibly scary that in almost an instant

so much was lost by an unusual

and incredibly rare extreme weather event.

- Experts say it's gonna take 150 years or more

for Lake Carezza's forests to reach their former glory,

but Italy has vowed to protect them.

NARRATOR: Cyclone Vaia has altered the face

of this once pristine forest for decades to come.

- Anything with that kind of power deserves a mark of respect.

NARRATOR: Tornadoes of fire, vanishing icons,

infamous nuclear accidents and killer cyclones.

Sometimes a disaster's devastating power

can only truly be revealed by a view from above.

Subtitles by Sky Access Services