Episode 2 Nature's Weirdest Events

We live in the age of information.

Events are transmitted to the palms of our hand 24 hours a day.

Events which surprise us,

occasionally even frighten us.

We're going to bring you some of the most bizarre

and mysterious natural phenomena on the planet.

From the sea that turns to cappuccino

to the massive holes that open and swallow buildings.

To an avian apocalypse on New Year's Eve.

What makes that happen,

for them just to drop out of the sky like that?

Using eyewitness accounts, news footage and experts and scientists,

we are going to try and explain what on Earth is going on.

For our first set of weird events, we're going to be looking

at stories that had people quaking in their boots.

When animals die in strange ways, superstitions can run wild.

And some are left fearing the end of the world is nigh.

From the old wives' tales of rains of fish,

to the weird and spooky event in the American Deep South.

But first, we're travelling to California,

where on 8th March, 2011, the locals awoke to something fishy.

As the sun came up over Redondo harbour, an ominous scene was revealed.

Overnight, the entire marina had become choked with death.

Californian authorities are carrying out a large-scale clean-up

after a million dead sardines were found floating in a marina just south of Los Angeles.

In some parts of King Harbour,

the water was half a metre thick with dead fish.

The carnage was incredible.

There was the odd survivor making a bid to escape a grisly fate.

But it was creepy, to say the least.

Soon, a worried crowd gathered to view this tragedy.

It's sad. It's really sad.

I can't believe how big these sardines are.

It makes me wonder what's in the water.

We're used to seeing fish hauled in by a trawler,

but for more than a million just to die spontaneously,

that's totally out of the ordinary.

Speculation ran riot as to the cause of these alien scenes.

I didn't think schools of fish could be this big.

There was way over a million.

It's pretty mind-boggling, I think.

So why had so many fish swum into the harbour

and then, what could have killed them?

Mass gatherings of fish are not unusual.

In fact, this is exactly what sardines are known for.

They shoal in their millions, following colder currents,

rich in plankton.

As the fish feast on this plentiful food,

they, in turn, become dinner,

as predators flock from miles around to feast on them.

Sharks cut through the shoal, which twists and turns like one giant organism.

Dolphins join in, herding the fish to the surface,

where the sardines have nowhere to go

and they are attacked from every angle.

So, had the fish at Redondo been chased into the harbour by hungry predators?

Or had the sardines come into the marina to shelter from the storm

that had blown up over the ocean that night?

Well, when they actually tested the fish, they found another,

more likely, culprit.

The sardines' last supper had been toxic algae.

Their bodies were full of a poisonous acid.

Scientists believe the effects of these toxins disorientated the fish,

leading them to accidentally swim into this dead end.

Once there, local experts say a more obvious danger awaited them.

Huge numbers of fish here in the harbour.

The sun goes down, so there's no photosynthesis going on, there's no oxygen being created,

there's just the fish consuming oxygen, so when they consume it all,

it's all gone and then they basically suffocate.

Whatever brought them into the harbour,

the nail in their coffins had been the lack of oxygen.

Death by suffocation. Not a pleasant way to die.

And as 75 tons of fish started to rot,

the smell wasn't very pleasant either.

But their deaths weren't entirely in vain.

The circle of life was completed, as more than a million sardines were sent to be used as fertiliser.

Our next story involves tales that go back to ancient times.

Worldwide, events have taken place that left eyewitnesses gazing skyward and asking, "How?"

So we're off to London in search of answers

to a very strange rain indeed.

According to the expression, "it's raining cats and dogs".

But, of course, that never really happens.

'Yet tales of animals falling from the sky is a phenomenon

that spans the centuries

and one particular creature is mentioned time and time again.

Fish - falling from the heavens like rain.

Surely fiction, not fact.

But Oliver Crimmen, the fish curator of the Natural History Museum,

believes these tall tales might actually have flesh on the bones.

In 1984, I was sitting at my desk in the museum,

I got a call from somebody

who said that fish had fallen from the sky in London.

Now, we do get some fairly unusual calls,

and I had heard of this phenomenon before.

But the caller was doubting that they would be taken seriously at all.

Mr Ron Langton had actually left the fishes lying in his garden,

and a reporter went and took some from the roof,

and from the yard outside his house, and brought them back to the museum.

But come on! Could this really be true?

Did these very fish really fall from the sky,

or is this some fanciful tale, no more than an elaborate hoax?

It's not impossible that somebody scattered fish around.

In this case, they didn't bother making them look very pretty,

and they carefully chose species which would be found nearby from the river.

It all looks pretty feasible.

So, the species lived in the Thames.

The river is, after all, where the fish belong,

but how could they find their way into the sky in order to fall from it?

Well, there is one potential explanation.

We don't associate fish with aerial transport at all,

but if we look for a natural phenomenon that could really account

for fish landing on the ground, really, the best going is a waterspout.

Now, a waterspout is similar to something you'd find on land.

Just as tornadoes can pick up trees and houses,

a waterspout could suck up fish.

These are then carried along in the storm

until it loses its energy, and its aquatic load is deposited on land.

Like fish out of water.

It all looks pretty feasible,

and I think if we take the number of reports,

and their varying quality,

then I think the phenomenon definitely occurs.

So it seems that science has an explanation

for these somewhat fanciful tales.

That said, the theory's constantly being tested by new events.

In Australia in 2010, fish fell from the sky in the middle of a dry red desert, miles from any water.

That must have been quite a waterspout.

But let's hope, in this age of communication and better technology,

that we finally get some photographic evidence of fish raining from the sky.

Then we can transform this phenomena from myth into scientific fact.

But when something totally out of the ordinary happens,

the fact doesn't always seem like the most believable explanation.

For our next story,

we head over the Atlantic to the American state of Arkansas,

where something quite incredible, and some might say, apocalyptic, took place.

The small city of Beebe, in the American Deep South,

home to 5,000 people, and 1.5 million red-winged blackbirds.

People and birds live side by side - the roost is set among the houses.

And as the sun goes down,

Beebe's noisiest residents paint the sky black, as they come in for the night.

But on New Year's Eve 2010,

the evening display got the attention of not just the locals,

but media all around the world.

Just before folks in Beebe rang in the new year, many witnessed

an uncanny resemblance to the Hitchcock movie The Birds.

As midnight approached, it wasn't fireworks falling through the sky in Beebe,

it was blackbirds - in their thousands.

They're everywhere. I'm not sure what's going on.

As 911 calls flooded in, the authorities swung into action.

'Yes, ma'am, I was wondering why the birds were just...'

Being New Year's Eve, I thought it might be some prank,

somebody calling me in, or somebody taking some drugs

and was seeing things.

I was coming down this road here,

and I started seeing the blackbirds all in the road

and it really hit me that this was a real call

and it wasn't bogus.

For the residents of Beebe, there was absolutely no doubt

this was really happening, as birds lay dead and dying right in their backyards.

I heard a thump, portico backs out of the house,

I thought it was someone IN the house,

then the thumps came a bit faster, so I walked outside,

that's when I saw the birds, scattered on the ground as far as I could see.

They were just everywhere.

I looked down the street, and it looked like... I would describe it as a war-zone.

It looked like...

somebody came out with heavy artillery and just blew these birds out of the sky.

To be honest, the birds had never been the most popular neighbours.

They were said to be noisy, smelly and their mess was everywhere.

The town had long wanted the roost gone,

but dead on their doorsteps on New Year's Eve?

This was more like a nightmare than a wish come true.

It really is like something out of a horror film.

Every yard in the area looks a lot to like this one.

Dozens of birds litter the ground and the scariest part is,

no-one knows how they got here.

I thought, "Well, someone has finally poisoned the birds."

Obviously, suspicion and rumour were rife.

How could 5,000 blackbirds just fall from the sky?

The people of Beebe needed answers and they needed them quick.

It was time to call in the experts.

Karen Roe is a state ornithologist.

She returned home from a New Year party

to find her phone full of panicked messages.

I called Robbie and he informed me

that there were birds all over Beebe.

The birds are going to hold the answer.

If a bird is dead, he'll tell you why he died.

I said, "Pick up a variety of birds.

"If you see different species, pick them up and wear gloves,

"because we don't know what happened."

By the morning, Robbie had been joined by a clean-up team,

kitted out in full hazard suits.

Surreal scenes to wake up to,

which did little to calm the locals' fears.

There were guys in white suits walking around like spacemen

picking up dead birds.

I'm wondering, do we need the same thing?

Because what makes that happen

for them to just drop out of the sky like that?

But before the scientists could even test the birds,

the story had started to take on its own momentum.

More questions tonight as to what caused thousands of blackbirds

to fall from the sky.

There's several opinions of what happened that night.

It was the government, it was aliens,

it was the sign of the end of times.

I've heard that it was the Lord's doing.

That this was a punishment and a warning to us - and maybe it was.

One online commentator suggests the most likely explanation

is that the blackbirds simply collided mid-air

with an invisible UFO.

Why did they choose this particular year to fall out of the sky?

The massive amount of public and media attention to this event

really heightened our awareness to the fact,

that we had to go the extra mile.

Rather than relying on just one laboratory,

we used three to conduct the test

so that we made sure all the laboratory tests concurred,

and there were no possibilities of someone having an unusual result

that we might need to further look at.

Kevin Keal was one of the pathologists

charged with finding the answers.

In this case, most of the birds were in good, nutritional condition.

They seem to be fairly healthy,

but they did have a lot of traumatic lesions

and this bird that I have here actually has a broken wing.

The birds that we received

consistently had lots of haemorrhaging in the body cavities.

These things suggest to us

that there's a blunt force trauma to the birds.

They suggest that they flew into something or something hit them.

There were so many birds,

it's unlikely that something hit 5,000 of them all at one time.

And all of the labs agreed.

The birds had flown into stationary objects and died.

But that wasn't the end of the story.

They may have found the cause of death,

but why had so many birds, 5,000 of them,

flown into things at the same time?

Well, the numbers can, in part, be explained

by the flocking nature of these birds.

You see, they're very much like a species of bird

we get here in the UK -

starlings.

Both flock in a huge numbers, creating incredible aerial displays.

Just look at this. A murmuration of starlings.

It really is one of the wonders of nature.

Beautiful.

But if some of the birds make a mistake,

they can all wind up in trouble.

And every now and again,

groups of starlings fall dead, right here in the UK.

Birds, like this starling,

have eyesight that is perfectly adapted for seeing in daylight.

Their eyes are on the sides of their head, so they can see all around,

but inside that eye, the cornea is packed with cone cells

and these are what give it its colour vision,

perfect for finding prey and keeping on the look-out for predators.

Cone cells might be great for the day,

but they're as good as useless in the dark.

At night time, Beebe's blackbirds are pretty much blind.

So when they took to the air,

crashing into things was an inevitable consequence.

But it was still a mystery as to why thousands of blackbirds

would be flying around at night in the pitch black,

-when normally they would be asleep.

We've talked to everyone we could in the city

and got numerous reports of an extraordinary loud noise.

Some said a propane cannon, some said surface-to-air missiles,

some said professional, not normal, selected grade fireworks,

that shook their windows, causing them to wake up, children to wake up.

That night I had heard approximately 13-14 loud booms,

kind of like what a sonic boom would be.

I'd say two minutes after that I started receiving calls

about blackbirds that were falling out of the sky.

So, finally, they had a culprit.

They weren't poisoned, they hadn't been shot down,

it wasn't even a UFO.

It was loud bangs, perhaps New Year fireworks

which had scared the birds out of their roost

and unable to see at night,

the blackbirds crashed into the nearby houses and died.

The problem was it was such an extraordinary event,

the explanation was almost too simple.

I've even heard this referred to as "The a-flock-alypse".

Of course, nothing brings out people worried about the end of the world

than something happening at New Year's Eve,

the dawn of the New Year.

Suddenly, I had people calling me

because they found one dead cedar wax wing under their window

and they thought that it was part of the apocalyptic bird mortality

happening around the world.

I'm sure if I walked outdoors

and saw birds falling out of the sky, I'd be a little disturbed, too.

But as biologists, one of the most disturbing things

is the fact that we deal in facts.

If we're not dealing in facts, we'll tell you, this is a hypothesis.

We were telling the truth and it wasn't necessarily being accepted.

You see, sometimes, people just don't want fact

to get in the way of the good story.

Beebe was just the start of a spate of bird deaths around the globe

that some people thought was a sign that the end of the world was nigh.

But the doomsayers needn't have worried,

because events like this have been taking place for generations.

What all these weird deaths show is nature's power to spook us.

From the fish that use up all their oxygen and suffocate,

to the waterspouts that supposedly sprinkle fish from the sky

and the unfortunate birds who flew to their deaths on New Year's Eve.

When animals die in strange circumstances,

some people are left fearing the apocalypse has come.

Next, we go in hunt of stories that will chill you to the bone.

As residents of this fair land,

we know only too well about the perils of ice,

but I'm going to tell you about ice on an altogether grander scale.

From the mysterious lumps that fall from the sky,

to the herd of creatures that were very much

in the wrong place at the wrong time.

For that story, we travel to America's frozen state.

HELICOPTER BLADES WHIRR

March 2011 in Alaska, just on the edge of the Arctic Circle.

Flying over the region was a team

from the National Park Service, tracking a herd of musk oxen with satellite tags.

As they scoured the snowy tundra, they spotted an eerie scene below.

There appeared to be something sticking out of the ice

and on closer inspection they saw the horns and fur

and what was attached to them was truly shocking.

The bodies of 55 musk oxen frozen solid to the spot.

So what terrible tragedy could have befallen these animals?

How could they have ended up entombed in ice?

Musk oxen are incredibly hardy creatures,

one of the few large mammals capable of living

year-round in the inhospitable Arctic environment.

They're protected from the bitter weather by two layers of fur.

But no amount of insulation could save them

from what fate was sending their way.

You see, the herd had been crossing a frozen bay

to reach feeding grounds on the other side.

But out at sea, a storm was brewing up.

The frozen platform they were stood on disintegrated,

as a tidal surge pushed from under the ice

and the herd were plunged into the freezing water.

Many of them probably drowned in the panic and confusion that ensued.

But if that wasn't enough to contend with,

trapped in the water, any survivors had to face the cold

and with air temperatures at minus 30 it didn't take long to re-freeze

and their spine-chilling demise was frozen for posterity.

Next, we're travelling home to the great British Isles,

far from the Arctic Circle, but not a stranger to the cold.

But then what happened one July day in 2009

was even quite extraordinary for a British summer.

We're all familiar with this weather phenomenon,

balls of ice pelting down on the earth.

Hail can even get rather large, so much so it becomes like missiles.

Ow! Wow!

Woo-hoo!

This is awesome!

But imagine if something like this fell out of the sky.

A grandfather has been hit by a big block of ice

which fell from the sky while he was in his garden.

It's true!

Enjoying a sunny day in Bristol, David Gammon

thought he'd had his bacon.

It's now down to about the size of an orange

but travelling at 120 miles an hour or so, it comes as quite a shock.

It's rather like being hit by a fast bowler with a cricket ball.

And that would be painful,

but where in the heavens had this single block of ice come from

in the middle of a summer's day?

Could it in some way be a mega-sized relation to hail?

For hail to form, you need one of these - cumulonimbus,

giant storm clouds that climb to enormous heights.

At the top, the air temperature is cold enough for ice crystals to form

and as these are jostled around inside the cloud, they grow and grow

until eventually, they're forced down to earth,

either because they've got too heavy

or a strong downdraught from the storm pushes them out.

Darren Bett is one of the BBC's weather forecasters.

There are cases of hailstones the size of golf balls,

hailstones even the size of a grapefruit.

But what fell on a car in Florida in 2007 was way bigger

than a grapefruit.

What started as a 45-centimetre block of ice

not only took out the back windscreen,

but also sent the car a metre into the air with the impact.

These larger chunks of ice are very, very heavy.

I don't know of any updraughts that can keep them up in the air

and grow them in the same way that a hailstorm can.

Also, they seem to be coming from cloudless skies.

Not only are they too heavy to be hail,

but without a cloud to have formed them,

the hail theory is, frankly, out the window.

So where could the finger point next?

If you look up, you're likely to see one potential culprit flying by.

Could they have fallen from a plane?

Padhraic Kelleher is the Head of Airworthiness

at the Civil Aviation Authority.

If the ice is completely clear,

then we are pretty sure it's most likely not an aviation source.

But sometimes we have reports of ice that's coloured.

That usually suggests there is chemical content,

which we do use in treating toilet waste.

So, beware of blue ice. Its origins could be somewhat unsavoury.

But then only 5% of reported cases in the UK

can be linked to planes, anyway.

So that leaves us scratching our heads about the other 95%.

Experts have named these unidentified falling objects as megacryometeors

and with a name like that, it would suggest they came from space.

But on closer inspection, they don't have enough dust or iron content

to be typical meteors.

For now, the scientists are actually out of ideas.

So, for the moment, large chunks of ice falling to Earth

remain a mystery, but there is one thing that's certain -

if one hits you, it's going to hurt you.

The largest ever recorded weighed 90 kilograms, that's 200lbs.

When that reached terminal velocity, at a speed of around 100mph,

well, that would be like being hit by an African elephant.

Not good.

Indeed.

All these stories remind us

that nature can do the most unexpected of things,

from the spine-chilling end that befell a herd of musk oxen,

to the mysterious chunks of ice that leave the scientific world flummoxed.

So much of the natural world can not only shock us,

but also leave us searching for answers.

Next, we're taking to the oceans

where the sea can do the most alien of things.

A phenomenon that makes the night sea glow so bright

it's visible from space.

And a natural event that's fatal to thousands of seabirds.

But we start Down Under,

where otherworldly scenes pulled in a big crowd.

Australia, the epitome of beach culture - sand, sea and surf.

But what happens when this...

turns to this?

Overnight the ocean had been whipped up into something quite extraordinary.

When the waves pushed in it would push the foam up real higher.

When it hit Yamba in New South Wales on 24 August, 2007,

it smothered everything.

Locals flooded to the beach to join in the foam party.

The waves were lifting the foam, but you couldn't see breaking waves.

We even had one member of my wife's family disappear in it

and it took us quite a while to find him.

The site was so spectacular

it didn't take long for images of people coated in foam

to flash around the world.

Yamba became known as the "Cappuccino Coast".

But what was going on? Why had the sea whipped up like cream?

To find out, we're heading to the National Oceanography Centre,

in Southampton, where Dr Simon Boxall is a coastal expert.

Over the last few years, we've seen some fantastic sea foam events.

A lot of people assume it's caused by pollution. In actual fact, it's not.

It's caused by these things.

It's caused by plankton - phytoplankton, primarily.

And plankton is the basis of much of the life in the sea,

the bottom link in the food chain,

feeding everything from tiny fish to the giants of the ocean.

And plankton supports us, too.

Much of the Earth's oxygen is produced by these tiny organisms.

As the phytoplankton die, they release various compounds.

When these things are agitated, they create sea foam.

They act like surfactants, almost like washing up liquid, in some ways.

This combination of strong blooms and strong wave activity

produces the most spectacular sea foam shows on the planet.

In the case at Yamba, the event happened after inland floods

washed nutrients from farmland soil out to sea.

These enriched waters are the perfect habitat

for a massive bloom of plankton.

Now, when the plankton was healthy, nothing happened.

But when the bloom started to die a surfactant was given off

which, when whipped up by a storm, produced foam on a gigantic scale.

Right, whilst on one side of the world

the Cappuccino Coast is a tourist attraction,

we travel next across the Pacific to the Washington coastline,

where, in November 2009, the foam that whipped up

had altogether more serious consequences.

A full-blown wildlife crisis tonight on the north-west coastline.

Thousands of seabirds are dying from a slimy foam

that stretches from Washington's Olympic coastline

all the way to the Northern Oregon coastline.

Foam on the beach is not unusual,

but this foam was killer foam.

This was ugly smelling, ugly looking

and incredibly tall.

Thousands of seabirds, dead and dying,

along 300 miles of the American West Coast.

Offshore species showing up on land,

in scenes reminiscent of a man-made disaster.

The scope of the situation is hard for even the scientists to grasp.

The Wildlife Centre Of The North Coast, near Astoria,

-is flat-out overwhelmed.

-Even though I've been picking them up,

I go back to the same place, there's more birds.

The birds in the foam were offshore species - murres, grebes and loons -

only seen on the beach when they're really in trouble.

So, volunteers started getting themselves organised

to head out and rescue them.

Typically, when I come out here and walk on the beach,

I could walk for a mile or two and see one or two dead birds.

On this day, obviously, there were literally hundreds you could see.

They were wet, sandy. It was really a mess.

I've never seen anything like that.

Wildlife centres cleared the decks,

but they simply couldn't keep up with the deluge.

Every little available space we could find

we walled off to make an enclosure. We had kennels up on the counters.

Just about any available space we could find.

As the rescue effort struggled to keep up,

even the scientists were overwhelmed by this event.

Julia Parrish is an ornithologist at the University of Washington.

I've been a seabird biologist for about 25 years

and I've seen a lot of death.

This event was huge. I've never seen anything like it.

I hope never to see anything like it again.

So, what was causing such an enormous and devastating event?

Well, as the scientists looked to figure it out,

they came across something in the archives that might help them.

Two years earlier, 800 miles down the coast at Monterey Bay,

in California, seabirds had died in their thousands.

Raphe Kudela, at the University of Santa Cruz,

is an ocean ecologist and he was involved in unravelling the mystery.

Initially, when the birds started coming in,

it was assumed it was from an oil spill.

But as soon as they tested them,

they realised there was no petroleum products on the birds.

At that point, it gets classified as something called a mystery spill.

At the time, there was a natural event happening out at sea

that's known as a red tide,

a mass of algae that group together in huge numbers.

Some of these can be very toxic.

But this particular dinoflagellate algae

had never been recorded causing any harm before.

We were trying to work out the link between the dinoflagellates,

that are supposed to be harmless, and what's happening to these birds.

We had this red tide offshore,

but on the beach there was this foam piling up.

We assumed the foam had something to do with the algae.

But we didn't know exactly what was going on.

The birds in the foam looked bedraggled.

And these are species

that spend much of their time diving underwater,

almost swimming, to catch their prey.

To stay warm, they rely on their terribly efficient down layer,

which is not only insulating but, vitally, waterproof,

keeping the cold water away from their skin.

Yet, the birds on the beach were freezing.

So Raphe and his colleagues began experimenting,

to see what was happening to their feathers.

If you dip feathers into normal water...

I just dipped that in and nothing happens.

The feather is still nice and fluffy.

But when we dip it into the foam...

..instead of popping back out, it's just all clodded down.

So the top of the feather is completely covered

in this sort of nasty goo.

Eventually, all that down is going to be collapsed

all the way against the quill, the feather.

and it's no longer waterproof, at all.

It's as if you went swimming in the cold ocean, in a wetsuit,

and all of a sudden your wetsuit dissolved.

You wouldn't last very long.

And that's exactly what happened to the birds.

The result was the largest known mortality of marine birds

anywhere in the world ever, due to an algal bloom.

8,000 bodies washed up in this event.

It's thought many thousands more died out at sea.

But for the rescued birds, there was hope,

as the scientists found a relatively simple fix.

One of the things that came out of our study is,

they very quickly realised that, if you get to the birds

before they actually die, all you need to do is put them in clean water

and keep them warm and they can clean themselves.

It's just a matter of getting rid of this foam

and keeping them from going into hypothermia.

At the rescue centres, this was encouraging news.

But the birds were in such poor condition,

it was a fight against the clock.

To get the birds back to being waterproof again

and getting the toxic algae off of them, we would swim them.

So we would get as many as we could in here at one time.

They'd be in here just a very short period.

And the water, of course, would turn just yellow-green.

It was pretty horrible to see.

It took more than one washing to get that algae off of them.

By about three days of washing, three or four,

we started noticing the difference.

For the lucky ones,

intensive care from the volunteers restored them to health.

And with their waterproofing back, many were capable of returning home.

Scientists think that this incident didn't have any long-term effects

on the seabird populations.

You see, nature is terribly resilient.

It always seems to bounce back,

even when it's been faced with what appears to be total devastation.

Nevertheless, it is surprising that an organism as small as algae

can cause so much trouble around the world.

But it's not all death and destruction.

Algal blooms can play host

to something altogether more spectacular.

For this story, we're travelling to the Indian Ocean,

where a phenomenon took place that was nothing short of magical.

In 1982, Hywel Phillips was the captain of a tanker

crossing the Persian Gulf

when his ship sailed into what looked like another planet.

A dull green glow is the only way I can explain it.

And it was a weird, a really weird feeling,

because you felt as if you were in a sphere

of light green translucence,

which stretched from horizon to horizon.

You couldn't tell the difference between the sky and the sea.

There was enough light given off by this glow to see objects

very clearly on the bridge.

A most spectacular, spectacular sight.

So, what on Earth could this spectacular sight be?

What could make the ocean glow so bright you lose all sense of space?

Well, actually, the ability to give off light

is one of the great wonders of the natural world.

You might be familiar with fireflies,

tiny insects that can glow in the dark.

But bioluminescence is mostly found in the seas,

where a plethora of living things,

from octopus and fish, down to single-cell bacteria and algae,

have the incredible power to emit their own light.

It's all down to chemical reactions.

When these take place inside the creature or organism,

the result is a burst of energy,

appearing in the form of photons, which makes visible light.

But emitting light so the entire sea glows from horizon to horizon?

Is bioluminescence really capable of such incredible scale?

Well, Steve Haddock is a bioluminescence specialist

from the Monterey Bay Research Institute in California.

It's one of the legends of bioluminescence.

If you work in the field, it's one of the stories people always tell,

but rarely witness themselves.

This legend has evolved through history,

with ships reporting bioluminescent oceans for centuries.

The folklore of what's become known as "milky seas"

captured the imagination of a satellite meteorologist

at the Naval Research Lab in California.

Using satellites,

Steve Miller decided to go in search of a milky sea,

to move these tall tales from legend to reality.

It was an exciting idea for us to go after this with satellite imagery,

because it's never been done before.

The question was, are these ocean surfaces glowing bright enough

for the satellites to see?

Well, to find out, he first needed a sighting to investigate.

He came across a report from 1996, off the coast of Somalia.

A ship, the SS Lima, had reported crossing a sea of milky white.

So, Steve trawled through the archives of satellites

until he found one that matched.

We brought up the satellite imagery,

we saw what appeared to be a smudge on the screen.

But it wouldn't go away when we moved the screen around

and it wouldn't go away when we wiped.

So when we started to enhance this satellite image,

the smudge just got brighter and brighter.

"OK, that's interesting."

But then when we overlaid the points where the steamship Lima

had first crossed the water and exited the glowing waters,

those points lined up exactly with the boundaries of this smudge.

The hair on the back of my neck just rose up.

It was one of those Eureka moments in science, that we have something here.

It's almost like having an image of Bigfoot or the Loch Ness Monster.

Finally, there was photographic proof

that this legend was, in fact, true.

And, for the first time,

scientists could actually see its staggering scale.

What we're talking about here is a patch of sea

the size of the US state of Connecticut.

And it's emitting light so bright that it was visible from space.

Now, normally bioluminescence is small-scale,

intermittent bursts of light.

So how could hundreds of square miles glow continuously?

Well, the scientists believe it all begins with an algal bloom which,

in its dying phase, is colonised by huge numbers of bacteria.

Then, a very special phenomenon called quorum sensing is triggered,

resulting in this spectacular light show.

Quorum sensing is this requirement for the bacteria to get together

and detect that I'm existing with a bunch of similar bacteria

in a very high concentration right now.

They signal with chemical cues to each other.

That actually turns on the pathway that starts light production.

So, the numbers of bacteria that we estimated for this event

were 4 x 10 of the 22nd.

If you can imagine trying to count to a trillion

and then do that 40 billion times, it's an unimaginably large number.

So, it's likely the milky sea grew from trillions of bacteria

feeding on dying algae.

But until they can get out there to experience one first-hand,

much of this is just hypothesis.

It's been my dream ever since we saw one on satellite

to actually be able to go out and get into one of these things.

I've joked with Steve Haddock a couple of times

about us forming a SWAT team

and just being able to see one of these happening from the satellite

and then fly out there really quick and get into one.

I would love to get out to sample it, see how deep it is.

We're just speculating on how far below the surface this layer is.

Who wouldn't want to be in that sort of situation,

where you could experience something so surreal, so incredible,

that it just defies your imagination?

I consider myself extremely lucky with what I have seen at sea.

This magical phenomenon looks set to remain a mystery.

70% of the world's milky seas occur off of the coast of Somalia.

With all of the pirate activity there,

there's little likelihood of much further exploration

in the near future.

But I like the fact that on our tiny planet

nature still has plenty of secrets for us to decipher.

From the fun foam that whips up in Australia,

to the killer foam of the American West Coast.

To the pure magic of the glowing ocean.

All of these stories show us that even the smallest things in nature,

tiny organisms, have the power of shock and awe.

Our next weird events might shake you to your very foundations.

When things happen deep in the earth,

they can have devastating effects on the surface.

From the school playground that disappeared in China,

to the houses that were wiped from a suburban street.

But we start in America's Sunshine State,

where something altogether larger was at the mercy of the Earth.

Large parts of Florida provide a wetland paradise for wildlife.

And Lake Jackson was no exception.

This pristine, six-square-mile freshwater lake

absolutely teamed with wildlife.

It was home to dozens of species of bird,

including snowy egrets and little blue herons.

American alligators swam in its crystal clear waters.

It really was a wildlife haven

and a much loved natural resource for local residents.

But in 1999, Florida was hit by a terrible drought.

For months on end, no rain fell and Lake Jackson got lower,

and lower, and lower.

Michael Hill from the Wildlife And Fish Commission

records water levels in the region.

And his gauge was showing him something quite extraordinary.

I monitored the water levels pretty often, every few days.

And there's one particular day, just in early September,

I saw it go down a couple of feet in one day.

I came back and it had gone down another two feet.

The lake was disappearing faster than anyone could have predicted.

And it was beyond anything you'd expect to see from a drought.

For the creatures of the lake, the situation was becoming critical.

Water management expert Tyler McMillan could not believe

what was happening.

The water was swirling and draining very quickly.

There were so many fish in the pool

that it was almost boiling with fish.

Look at this. No need for a rod and line,

these opportunists were hauling out fish by the armload.

It was incredible that people were standing in these muddy creeks,

looking like bears, that you'd see in Alaska.

They were feeling the bass hit their feet

and they were throwing it up on the bank.

But it wasn't just the fish that were quickly running out of water.

Other lake residents, like terrapins, were desperately trying to escape

as the rapidly dwindling lake reached an all-time low.

With nowhere else to go,

some of these desperate animals went for any water they could find.

Are you videoing it?

I am video-taping everything right now.

Let me go down to the water

and look at the alligator in our pool...

..that Daddy is about to lasso.

Yeah, we'll see!

But you guys sit.

You fall in there and I'll kill you.

Oh, my. All right, kids.

Back this way.

How cool was that?

Meanwhile, back at the lake,

the last of the water was rapidly draining away.

On the 16th of September 1999,

this was revealed.

There was a gaping hole in the bottom of the lake.

It was, quite literally, as if someone had pulled the plug

out of a giant bathtub.

And Lake Jackson disappeared.

And with it, sadly, went much of its wildlife.

But how could a huge hole open up in the bottom of the lake?

And where had it taken all the water and all of the creatures?

It was time to call in the experts.

Harley Means is a geologist who spent his career studying the area.

Beneath us here, at some depth, is limestone.

And this limestone is very porous and full of cavities.

Through geologic time,

these cavities can become enlarged due to acids in groundwater.

At some point, when the conditions are appropriate,

you can have a collapse.

The mysterious hole that the water had disappeared into

was what's known as a sinkhole.

The limestone beneath the lake

had gradually dissolved away from underneath

until it reached the surface, and then the hole opened up.

With the water gone, Harley and his team of geologists

had a unique opportunity to find out more about this special sinkhole.

We could crawl down underground a good 20 to 25 feet

and then laterally another 20 to 50 feet in several directions.

For the first time,

they could see the full extent of the hole beneath the lake

and it was clear that any wildlife sucked down here

sadly wouldn't have survived.

It was dark and it was full of organic material

that had drained through it.

It didn't smell very good.

Really, it was a very slimy endeavour to get down there

and get into this cave system.

But it gave us information, information as geologists that we could utilise.

Harley and his team were able to confirm

their suspicions about the hole.

It had actually been there for a very long time,

maybe hundreds of years.

So, how had the lake managed to form above it?

Well, over the years, the hole had silted up with mud and debris.

This had formed a sort of plug.

The drought in '99 had triggered its collapse.

Limestone is like a sponge full of holes.

When those holes have water in them, they're able to actually provide

a little support to the ground over the top of them.

But when the water is drawn out, those holes are now full of air

and not as capable of supporting the load on top of them -

in this case, the plug in the bottom of the sinkhole -

and the water finally just rushed out in one final big pulse.

All seemed lost.

The lake was gone and, in its place, was grass and scrub.

Where turtles and fish had swum, now rabbits and deer were grazing.

But Tyler McMillan hadn't given up on the lake.

The legend has it that the original Native American name of this lake

is Okeeheepkee, which means "disappearing waters".

If the natives were calling it that many hundreds of years ago,

this event has been going on many, many times over the centuries.

So, if it had drained away before,

surely this could mean that it might refill again?

Florida's drought finally broke in 2001.

Sediment, washed by rainwater, replugged the sinkhole,

whilst the groundwater levels rose below it.

Insects buzzed, fish grew large with an abundance of new food,

encouraging once familiar bird species to return.

Lake Jackson was reborn.

The regular drying out and refilling of the lake seems catastrophic.

But local ecologist Matt Aresco

is strangely unconcerned about the impact of this cycle.

It's going to keep drying and refilling.

And it's good that it does that.

It's part of the ecology of the lake.

It's good for the species that live in the lake

and it's a really unique ecosystem that you don't find anywhere else.

Lake Jackson was once again bursting with life.

Let's hope it's a while before the plug gets pulled again.

An incredible story from America there.

But, you know, the UK does have its own fair share of sinkholes.

Ripon is a city built partially on gypsum

and it has at least 40 of these things.

In 1997, a sinkhole appeared on the edge of town

and a building collapsed into it.

But if you thought things were bad in Ripon,

wait until you see the devastation sinkholes have caused

in other parts of the world.

What happened in Guatemala City was quite unlike anything.

In June of 2010, a massive hole opened up

in the middle of a suburban street, swallowing a three-storey building.

Terrified local residents had a lucky escape and were evacuated

when the 60-metre deep chasm appeared suddenly during the night.

In southern China, a school playground suffered a similar fate.

This time the hole was 80 metres wide

and continued to grow for almost six months.

A little closer to home,

this time a small town in central Germany

suffered a devastating collapse.

Houses nearby had to be evacuated, and two car owners,

well, they were left with a bit of a conundrum.

British geologist Tony Cooper is an expert

in these terrifying sinkholes.

What has happened is that material has gradually washed away underground

and the cavity has got very large at depth.

And then the material has continued to wash away

and collapse over that cavity.

And that cavity has worked its way up to the surface.

At the surface,

especially in towns and suchlike,

you will have things like roads, concrete structures and so on.

These can actually bridge quite significant holes in the ground

until it gets to a point where it is so large

that nothing will bridge it, and then you'll get a catastrophic collapse.

In Guatemala, floodwater from a recent tropical cyclone

had washed away rock and sediments under the city.

It was a remarkably rapid process, with devastating consequences.

China has huge areas of limestone.

And, although no-one knew it,

the school playground that collapsed was right on top of a massive cave.

And in Germany?

Well, this time it was the dissolving of gypsum

that caused the land to give way.

But, whatever the rock, however the holes formed,

the consequences are the same.

For all of these sinkholes,

their power lies in the element of surprise.

Each of these holes appeared without warning

and it's impossible to predict

where the next one will open up.

But, wherever it happens, we will be left standing in awe

at the unpredictable and destructive side of nature.

Whether they're weird or wonderful,

events like these still have the power to shock and confuse us.

And no matter how much we think we know about all the living things,

nature still has the capacity to keep us in check

with its many mysteries that even the best brains struggle to explain.

And we can only imagine what incredible events

and weird phenomena there are yet to be discovered.

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