0:00:09 > 0:00:13We live in the age of information.
0:00:13 > 0:00:18Events are transmitted to the palms of our hand 24 hours a day.
0:00:18 > 0:00:21Events which surprise us,
0:00:21 > 0:00:24occasionally even frighten us.
0:00:25 > 0:00:28We're going to bring you some of the most bizarre
0:00:28 > 0:00:31and mysterious natural phenomena on the planet.
0:00:35 > 0:00:38From the sea that turns to cappuccino
0:00:38 > 0:00:42to the massive holes that open and swallow buildings.
0:00:43 > 0:00:47To an avian apocalypse on New Year's Eve.
0:00:47 > 0:00:49What makes that happen,
0:00:49 > 0:00:52for them just to drop out of the sky like that?
0:00:52 > 0:00:58Using eyewitness accounts, news footage and experts and scientists,
0:00:58 > 0:01:03we are going to try and explain what on Earth is going on.
0:01:24 > 0:01:27For our first set of weird events, we're going to be looking
0:01:27 > 0:01:32at stories that had people quaking in their boots.
0:01:32 > 0:01:36When animals die in strange ways, superstitions can run wild.
0:01:37 > 0:01:41And some are left fearing the end of the world is nigh.
0:01:44 > 0:01:48From the old wives' tales of rains of fish,
0:01:48 > 0:01:51to the weird and spooky event in the American Deep South.
0:01:57 > 0:02:00But first, we're travelling to California,
0:02:00 > 0:02:05where on 8th March, 2011, the locals awoke to something fishy.
0:02:07 > 0:02:11As the sun came up over Redondo harbour, an ominous scene was revealed.
0:02:13 > 0:02:19Overnight, the entire marina had become choked with death.
0:02:19 > 0:02:22Californian authorities are carrying out a large-scale clean-up
0:02:22 > 0:02:27after a million dead sardines were found floating in a marina just south of Los Angeles.
0:02:27 > 0:02:29In some parts of King Harbour,
0:02:29 > 0:02:31the water was half a metre thick with dead fish.
0:02:33 > 0:02:35The carnage was incredible.
0:02:35 > 0:02:40There was the odd survivor making a bid to escape a grisly fate.
0:02:41 > 0:02:44But it was creepy, to say the least.
0:02:44 > 0:02:48Soon, a worried crowd gathered to view this tragedy.
0:02:49 > 0:02:52It's sad. It's really sad.
0:02:52 > 0:02:55I can't believe how big these sardines are.
0:02:57 > 0:03:00It makes me wonder what's in the water.
0:03:00 > 0:03:03We're used to seeing fish hauled in by a trawler,
0:03:03 > 0:03:07but for more than a million just to die spontaneously,
0:03:07 > 0:03:09that's totally out of the ordinary.
0:03:09 > 0:03:15Speculation ran riot as to the cause of these alien scenes.
0:03:15 > 0:03:18I didn't think schools of fish could be this big.
0:03:18 > 0:03:21There was way over a million.
0:03:21 > 0:03:23It's pretty mind-boggling, I think.
0:03:26 > 0:03:30So why had so many fish swum into the harbour
0:03:30 > 0:03:32and then, what could have killed them?
0:03:37 > 0:03:39Mass gatherings of fish are not unusual.
0:03:42 > 0:03:46In fact, this is exactly what sardines are known for.
0:03:46 > 0:03:49They shoal in their millions, following colder currents,
0:03:49 > 0:03:51rich in plankton.
0:03:53 > 0:03:56As the fish feast on this plentiful food,
0:03:56 > 0:03:58they, in turn, become dinner,
0:03:58 > 0:04:02as predators flock from miles around to feast on them.
0:04:03 > 0:04:08Sharks cut through the shoal, which twists and turns like one giant organism.
0:04:10 > 0:04:13Dolphins join in, herding the fish to the surface,
0:04:13 > 0:04:17where the sardines have nowhere to go
0:04:17 > 0:04:19and they are attacked from every angle.
0:04:24 > 0:04:29So, had the fish at Redondo been chased into the harbour by hungry predators?
0:04:30 > 0:04:34Or had the sardines come into the marina to shelter from the storm
0:04:34 > 0:04:37that had blown up over the ocean that night?
0:04:40 > 0:04:43Well, when they actually tested the fish, they found another,
0:04:43 > 0:04:46more likely, culprit.
0:04:46 > 0:04:49The sardines' last supper had been toxic algae.
0:04:49 > 0:04:52Their bodies were full of a poisonous acid.
0:04:53 > 0:04:58Scientists believe the effects of these toxins disorientated the fish,
0:04:58 > 0:05:02leading them to accidentally swim into this dead end.
0:05:02 > 0:05:07Once there, local experts say a more obvious danger awaited them.
0:05:07 > 0:05:10Huge numbers of fish here in the harbour.
0:05:10 > 0:05:15The sun goes down, so there's no photosynthesis going on, there's no oxygen being created,
0:05:15 > 0:05:18there's just the fish consuming oxygen, so when they consume it all,
0:05:18 > 0:05:21it's all gone and then they basically suffocate.
0:05:22 > 0:05:24Whatever brought them into the harbour,
0:05:24 > 0:05:27the nail in their coffins had been the lack of oxygen.
0:05:29 > 0:05:32Death by suffocation. Not a pleasant way to die.
0:05:32 > 0:05:35And as 75 tons of fish started to rot,
0:05:35 > 0:05:38the smell wasn't very pleasant either.
0:05:39 > 0:05:42But their deaths weren't entirely in vain.
0:05:42 > 0:05:48The circle of life was completed, as more than a million sardines were sent to be used as fertiliser.
0:05:51 > 0:05:57Our next story involves tales that go back to ancient times.
0:05:57 > 0:06:02Worldwide, events have taken place that left eyewitnesses gazing skyward and asking, "How?"
0:06:02 > 0:06:05So we're off to London in search of answers
0:06:05 > 0:06:07to a very strange rain indeed.
0:06:12 > 0:06:15According to the expression, "it's raining cats and dogs".
0:06:15 > 0:06:17But, of course, that never really happens.
0:06:19 > 0:06:22'Yet tales of animals falling from the sky is a phenomenon
0:06:22 > 0:06:24that spans the centuries
0:06:24 > 0:06:28and one particular creature is mentioned time and time again.
0:06:30 > 0:06:33Fish - falling from the heavens like rain.
0:06:33 > 0:06:35Surely fiction, not fact.
0:06:38 > 0:06:42But Oliver Crimmen, the fish curator of the Natural History Museum,
0:06:42 > 0:06:47believes these tall tales might actually have flesh on the bones.
0:06:47 > 0:06:51In 1984, I was sitting at my desk in the museum,
0:06:51 > 0:06:55I got a call from somebody
0:06:55 > 0:06:59who said that fish had fallen from the sky in London.
0:06:59 > 0:07:01Now, we do get some fairly unusual calls,
0:07:01 > 0:07:04and I had heard of this phenomenon before.
0:07:04 > 0:07:08But the caller was doubting that they would be taken seriously at all.
0:07:11 > 0:07:16Mr Ron Langton had actually left the fishes lying in his garden,
0:07:16 > 0:07:20and a reporter went and took some from the roof,
0:07:20 > 0:07:24and from the yard outside his house, and brought them back to the museum.
0:07:26 > 0:07:30But come on! Could this really be true?
0:07:30 > 0:07:33Did these very fish really fall from the sky,
0:07:33 > 0:07:37or is this some fanciful tale, no more than an elaborate hoax?
0:07:37 > 0:07:41It's not impossible that somebody scattered fish around.
0:07:41 > 0:07:45In this case, they didn't bother making them look very pretty,
0:07:45 > 0:07:50and they carefully chose species which would be found nearby from the river.
0:07:50 > 0:07:51It all looks pretty feasible.
0:07:54 > 0:07:56So, the species lived in the Thames.
0:07:56 > 0:07:59The river is, after all, where the fish belong,
0:07:59 > 0:08:04but how could they find their way into the sky in order to fall from it?
0:08:07 > 0:08:10Well, there is one potential explanation.
0:08:10 > 0:08:15We don't associate fish with aerial transport at all,
0:08:15 > 0:08:19but if we look for a natural phenomenon that could really account
0:08:19 > 0:08:24for fish landing on the ground, really, the best going is a waterspout.
0:08:25 > 0:08:30Now, a waterspout is similar to something you'd find on land.
0:08:30 > 0:08:34Just as tornadoes can pick up trees and houses,
0:08:34 > 0:08:36a waterspout could suck up fish.
0:08:37 > 0:08:40These are then carried along in the storm
0:08:40 > 0:08:45until it loses its energy, and its aquatic load is deposited on land.
0:08:45 > 0:08:48Like fish out of water.
0:08:49 > 0:08:52It all looks pretty feasible,
0:08:52 > 0:08:54and I think if we take the number of reports,
0:08:54 > 0:08:56and their varying quality,
0:08:56 > 0:09:02then I think the phenomenon definitely occurs.
0:09:05 > 0:09:07So it seems that science has an explanation
0:09:07 > 0:09:10for these somewhat fanciful tales.
0:09:10 > 0:09:14That said, the theory's constantly being tested by new events.
0:09:14 > 0:09:23In Australia in 2010, fish fell from the sky in the middle of a dry red desert, miles from any water.
0:09:23 > 0:09:25That must have been quite a waterspout.
0:09:25 > 0:09:29But let's hope, in this age of communication and better technology,
0:09:29 > 0:09:35that we finally get some photographic evidence of fish raining from the sky.
0:09:35 > 0:09:41Then we can transform this phenomena from myth into scientific fact.
0:09:41 > 0:09:45But when something totally out of the ordinary happens,
0:09:45 > 0:09:50the fact doesn't always seem like the most believable explanation.
0:09:50 > 0:09:51For our next story,
0:09:51 > 0:09:55we head over the Atlantic to the American state of Arkansas,
0:09:55 > 0:10:00where something quite incredible, and some might say, apocalyptic, took place.
0:10:10 > 0:10:14The small city of Beebe, in the American Deep South,
0:10:14 > 0:10:19home to 5,000 people, and 1.5 million red-winged blackbirds.
0:10:21 > 0:10:27People and birds live side by side - the roost is set among the houses.
0:10:29 > 0:10:31And as the sun goes down,
0:10:31 > 0:10:37Beebe's noisiest residents paint the sky black, as they come in for the night.
0:10:37 > 0:10:39But on New Year's Eve 2010,
0:10:39 > 0:10:43the evening display got the attention of not just the locals,
0:10:43 > 0:10:47but media all around the world.
0:10:47 > 0:10:51Just before folks in Beebe rang in the new year, many witnessed
0:10:51 > 0:10:54an uncanny resemblance to the Hitchcock movie The Birds.
0:10:54 > 0:11:00As midnight approached, it wasn't fireworks falling through the sky in Beebe,
0:11:00 > 0:11:03it was blackbirds - in their thousands.
0:11:03 > 0:11:06They're everywhere. I'm not sure what's going on.
0:11:06 > 0:11:12As 911 calls flooded in, the authorities swung into action.
0:11:14 > 0:11:17'Yes, ma'am, I was wondering why the birds were just...'
0:11:20 > 0:11:23Being New Year's Eve, I thought it might be some prank,
0:11:23 > 0:11:29somebody calling me in, or somebody taking some drugs
0:11:29 > 0:11:31and was seeing things.
0:11:31 > 0:11:33I was coming down this road here,
0:11:33 > 0:11:36and I started seeing the blackbirds all in the road
0:11:36 > 0:11:41and it really hit me that this was a real call
0:11:41 > 0:11:43and it wasn't bogus.
0:11:43 > 0:11:47For the residents of Beebe, there was absolutely no doubt
0:11:47 > 0:11:52this was really happening, as birds lay dead and dying right in their backyards.
0:11:52 > 0:11:55I heard a thump, portico backs out of the house,
0:11:55 > 0:11:57I thought it was someone IN the house,
0:11:57 > 0:12:02then the thumps came a bit faster, so I walked outside,
0:12:02 > 0:12:07that's when I saw the birds, scattered on the ground as far as I could see.
0:12:07 > 0:12:09They were just everywhere.
0:12:09 > 0:12:13I looked down the street, and it looked like... I would describe it as a war-zone.
0:12:13 > 0:12:15It looked like...
0:12:15 > 0:12:19somebody came out with heavy artillery and just blew these birds out of the sky.
0:12:19 > 0:12:25To be honest, the birds had never been the most popular neighbours.
0:12:25 > 0:12:29They were said to be noisy, smelly and their mess was everywhere.
0:12:29 > 0:12:31The town had long wanted the roost gone,
0:12:31 > 0:12:33but dead on their doorsteps on New Year's Eve?
0:12:33 > 0:12:36This was more like a nightmare than a wish come true.
0:12:36 > 0:12:39It really is like something out of a horror film.
0:12:39 > 0:12:41Every yard in the area looks a lot to like this one.
0:12:41 > 0:12:45Dozens of birds litter the ground and the scariest part is,
0:12:45 > 0:12:46no-one knows how they got here.
0:12:46 > 0:12:51I thought, "Well, someone has finally poisoned the birds."
0:12:51 > 0:12:55Obviously, suspicion and rumour were rife.
0:12:55 > 0:12:59How could 5,000 blackbirds just fall from the sky?
0:12:59 > 0:13:04The people of Beebe needed answers and they needed them quick.
0:13:04 > 0:13:07It was time to call in the experts.
0:13:07 > 0:13:09Karen Roe is a state ornithologist.
0:13:09 > 0:13:12She returned home from a New Year party
0:13:12 > 0:13:15to find her phone full of panicked messages.
0:13:15 > 0:13:18I called Robbie and he informed me
0:13:18 > 0:13:21that there were birds all over Beebe.
0:13:21 > 0:13:22The birds are going to hold the answer.
0:13:22 > 0:13:25If a bird is dead, he'll tell you why he died.
0:13:25 > 0:13:27I said, "Pick up a variety of birds.
0:13:27 > 0:13:30"If you see different species, pick them up and wear gloves,
0:13:30 > 0:13:32"because we don't know what happened."
0:13:32 > 0:13:36By the morning, Robbie had been joined by a clean-up team,
0:13:36 > 0:13:39kitted out in full hazard suits.
0:13:39 > 0:13:41Surreal scenes to wake up to,
0:13:41 > 0:13:45which did little to calm the locals' fears.
0:13:45 > 0:13:48There were guys in white suits walking around like spacemen
0:13:48 > 0:13:50picking up dead birds.
0:13:50 > 0:13:52I'm wondering, do we need the same thing?
0:13:52 > 0:13:55Because what makes that happen
0:13:55 > 0:13:58for them to just drop out of the sky like that?
0:13:59 > 0:14:03But before the scientists could even test the birds,
0:14:03 > 0:14:07the story had started to take on its own momentum.
0:14:07 > 0:14:12More questions tonight as to what caused thousands of blackbirds
0:14:12 > 0:14:13to fall from the sky.
0:14:13 > 0:14:16There's several opinions of what happened that night.
0:14:16 > 0:14:19It was the government, it was aliens,
0:14:19 > 0:14:21it was the sign of the end of times.
0:14:21 > 0:14:24I've heard that it was the Lord's doing.
0:14:24 > 0:14:29That this was a punishment and a warning to us - and maybe it was.
0:14:29 > 0:14:33One online commentator suggests the most likely explanation
0:14:33 > 0:14:36is that the blackbirds simply collided mid-air
0:14:36 > 0:14:38with an invisible UFO.
0:14:38 > 0:14:44Why did they choose this particular year to fall out of the sky?
0:14:44 > 0:14:47The massive amount of public and media attention to this event
0:14:47 > 0:14:49really heightened our awareness to the fact,
0:14:49 > 0:14:52that we had to go the extra mile.
0:14:52 > 0:14:55Rather than relying on just one laboratory,
0:14:55 > 0:14:57we used three to conduct the test
0:14:57 > 0:15:00so that we made sure all the laboratory tests concurred,
0:15:00 > 0:15:04and there were no possibilities of someone having an unusual result
0:15:04 > 0:15:07that we might need to further look at.
0:15:08 > 0:15:11Kevin Keal was one of the pathologists
0:15:11 > 0:15:13charged with finding the answers.
0:15:15 > 0:15:19In this case, most of the birds were in good, nutritional condition.
0:15:19 > 0:15:22They seem to be fairly healthy,
0:15:22 > 0:15:24but they did have a lot of traumatic lesions
0:15:24 > 0:15:27and this bird that I have here actually has a broken wing.
0:15:27 > 0:15:29The birds that we received
0:15:29 > 0:15:32consistently had lots of haemorrhaging in the body cavities.
0:15:32 > 0:15:34These things suggest to us
0:15:34 > 0:15:38that there's a blunt force trauma to the birds.
0:15:38 > 0:15:42They suggest that they flew into something or something hit them.
0:15:42 > 0:15:43There were so many birds,
0:15:43 > 0:15:47it's unlikely that something hit 5,000 of them all at one time.
0:15:48 > 0:15:50And all of the labs agreed.
0:15:50 > 0:15:55The birds had flown into stationary objects and died.
0:15:55 > 0:15:57But that wasn't the end of the story.
0:15:57 > 0:15:59They may have found the cause of death,
0:15:59 > 0:16:02but why had so many birds, 5,000 of them,
0:16:02 > 0:16:05flown into things at the same time?
0:16:07 > 0:16:10Well, the numbers can, in part, be explained
0:16:10 > 0:16:13by the flocking nature of these birds.
0:16:23 > 0:16:26You see, they're very much like a species of bird
0:16:26 > 0:16:28we get here in the UK -
0:16:28 > 0:16:29starlings.
0:16:29 > 0:16:34Both flock in a huge numbers, creating incredible aerial displays.
0:16:34 > 0:16:37Just look at this. A murmuration of starlings.
0:16:37 > 0:16:39It really is one of the wonders of nature.
0:16:43 > 0:16:44Beautiful.
0:16:52 > 0:16:54But if some of the birds make a mistake,
0:16:54 > 0:16:57they can all wind up in trouble.
0:16:57 > 0:16:59And every now and again,
0:16:59 > 0:17:02groups of starlings fall dead, right here in the UK.
0:17:09 > 0:17:10Birds, like this starling,
0:17:10 > 0:17:15have eyesight that is perfectly adapted for seeing in daylight.
0:17:15 > 0:17:18Their eyes are on the sides of their head, so they can see all around,
0:17:18 > 0:17:23but inside that eye, the cornea is packed with cone cells
0:17:23 > 0:17:25and these are what give it its colour vision,
0:17:25 > 0:17:30perfect for finding prey and keeping on the look-out for predators.
0:17:33 > 0:17:35Cone cells might be great for the day,
0:17:35 > 0:17:38but they're as good as useless in the dark.
0:17:38 > 0:17:43At night time, Beebe's blackbirds are pretty much blind.
0:17:43 > 0:17:44So when they took to the air,
0:17:44 > 0:17:48crashing into things was an inevitable consequence.
0:17:48 > 0:17:51But it was still a mystery as to why thousands of blackbirds
0:17:51 > 0:17:54would be flying around at night in the pitch black,
0:17:54 > 0:17:56- when normally they would be asleep.
0:17:56 > 0:17:59We've talked to everyone we could in the city
0:17:59 > 0:18:04and got numerous reports of an extraordinary loud noise.
0:18:04 > 0:18:08Some said a propane cannon, some said surface-to-air missiles,
0:18:08 > 0:18:13some said professional, not normal, selected grade fireworks,
0:18:13 > 0:18:17that shook their windows, causing them to wake up, children to wake up.
0:18:17 > 0:18:23That night I had heard approximately 13-14 loud booms,
0:18:23 > 0:18:25kind of like what a sonic boom would be.
0:18:25 > 0:18:28I'd say two minutes after that I started receiving calls
0:18:28 > 0:18:31about blackbirds that were falling out of the sky.
0:18:33 > 0:18:36So, finally, they had a culprit.
0:18:36 > 0:18:39They weren't poisoned, they hadn't been shot down,
0:18:39 > 0:18:41it wasn't even a UFO.
0:18:41 > 0:18:45It was loud bangs, perhaps New Year fireworks
0:18:45 > 0:18:48which had scared the birds out of their roost
0:18:48 > 0:18:50and unable to see at night,
0:18:50 > 0:18:53the blackbirds crashed into the nearby houses and died.
0:18:55 > 0:18:58The problem was it was such an extraordinary event,
0:18:58 > 0:19:01the explanation was almost too simple.
0:19:05 > 0:19:08I've even heard this referred to as "The a-flock-alypse".
0:19:08 > 0:19:11Of course, nothing brings out people worried about the end of the world
0:19:11 > 0:19:14than something happening at New Year's Eve,
0:19:14 > 0:19:16the dawn of the New Year.
0:19:16 > 0:19:18Suddenly, I had people calling me
0:19:18 > 0:19:22because they found one dead cedar wax wing under their window
0:19:22 > 0:19:26and they thought that it was part of the apocalyptic bird mortality
0:19:26 > 0:19:28happening around the world.
0:19:29 > 0:19:31I'm sure if I walked outdoors
0:19:31 > 0:19:34and saw birds falling out of the sky, I'd be a little disturbed, too.
0:19:34 > 0:19:37But as biologists, one of the most disturbing things
0:19:37 > 0:19:39is the fact that we deal in facts.
0:19:39 > 0:19:42If we're not dealing in facts, we'll tell you, this is a hypothesis.
0:19:42 > 0:19:45We were telling the truth and it wasn't necessarily being accepted.
0:19:47 > 0:19:51You see, sometimes, people just don't want fact
0:19:51 > 0:19:53to get in the way of the good story.
0:19:57 > 0:20:02Beebe was just the start of a spate of bird deaths around the globe
0:20:02 > 0:20:06that some people thought was a sign that the end of the world was nigh.
0:20:06 > 0:20:09But the doomsayers needn't have worried,
0:20:09 > 0:20:12because events like this have been taking place for generations.
0:20:15 > 0:20:20What all these weird deaths show is nature's power to spook us.
0:20:20 > 0:20:23From the fish that use up all their oxygen and suffocate,
0:20:23 > 0:20:27to the waterspouts that supposedly sprinkle fish from the sky
0:20:27 > 0:20:32and the unfortunate birds who flew to their deaths on New Year's Eve.
0:20:32 > 0:20:35When animals die in strange circumstances,
0:20:35 > 0:20:39some people are left fearing the apocalypse has come.
0:20:42 > 0:20:46Next, we go in hunt of stories that will chill you to the bone.
0:20:46 > 0:20:49As residents of this fair land,
0:20:49 > 0:20:51we know only too well about the perils of ice,
0:20:51 > 0:20:57but I'm going to tell you about ice on an altogether grander scale.
0:20:57 > 0:21:01From the mysterious lumps that fall from the sky,
0:21:01 > 0:21:04to the herd of creatures that were very much
0:21:04 > 0:21:08in the wrong place at the wrong time.
0:21:08 > 0:21:12For that story, we travel to America's frozen state.
0:21:12 > 0:21:15HELICOPTER BLADES WHIRR
0:21:15 > 0:21:21March 2011 in Alaska, just on the edge of the Arctic Circle.
0:21:21 > 0:21:24Flying over the region was a team
0:21:24 > 0:21:30from the National Park Service, tracking a herd of musk oxen with satellite tags.
0:21:30 > 0:21:34As they scoured the snowy tundra, they spotted an eerie scene below.
0:21:36 > 0:21:39There appeared to be something sticking out of the ice
0:21:39 > 0:21:43and on closer inspection they saw the horns and fur
0:21:43 > 0:21:47and what was attached to them was truly shocking.
0:21:47 > 0:21:51The bodies of 55 musk oxen frozen solid to the spot.
0:21:57 > 0:22:01So what terrible tragedy could have befallen these animals?
0:22:01 > 0:22:04How could they have ended up entombed in ice?
0:22:11 > 0:22:14Musk oxen are incredibly hardy creatures,
0:22:14 > 0:22:17one of the few large mammals capable of living
0:22:17 > 0:22:20year-round in the inhospitable Arctic environment.
0:22:23 > 0:22:28They're protected from the bitter weather by two layers of fur.
0:22:28 > 0:22:31But no amount of insulation could save them
0:22:31 > 0:22:35from what fate was sending their way.
0:22:36 > 0:22:40You see, the herd had been crossing a frozen bay
0:22:40 > 0:22:43to reach feeding grounds on the other side.
0:22:43 > 0:22:46But out at sea, a storm was brewing up.
0:22:48 > 0:22:52The frozen platform they were stood on disintegrated,
0:22:52 > 0:22:55as a tidal surge pushed from under the ice
0:22:55 > 0:22:59and the herd were plunged into the freezing water.
0:22:59 > 0:23:04Many of them probably drowned in the panic and confusion that ensued.
0:23:04 > 0:23:06But if that wasn't enough to contend with,
0:23:06 > 0:23:11trapped in the water, any survivors had to face the cold
0:23:11 > 0:23:15and with air temperatures at minus 30 it didn't take long to re-freeze
0:23:15 > 0:23:20and their spine-chilling demise was frozen for posterity.
0:23:24 > 0:23:28Next, we're travelling home to the great British Isles,
0:23:28 > 0:23:32far from the Arctic Circle, but not a stranger to the cold.
0:23:32 > 0:23:36But then what happened one July day in 2009
0:23:36 > 0:23:39was even quite extraordinary for a British summer.
0:23:39 > 0:23:42We're all familiar with this weather phenomenon,
0:23:42 > 0:23:45balls of ice pelting down on the earth.
0:23:45 > 0:23:49Hail can even get rather large, so much so it becomes like missiles.
0:23:49 > 0:23:52Ow! Wow!
0:23:52 > 0:23:53Woo-hoo!
0:23:55 > 0:23:57This is awesome!
0:23:57 > 0:24:02But imagine if something like this fell out of the sky.
0:24:04 > 0:24:07A grandfather has been hit by a big block of ice
0:24:07 > 0:24:10which fell from the sky while he was in his garden.
0:24:10 > 0:24:12It's true!
0:24:12 > 0:24:15Enjoying a sunny day in Bristol, David Gammon
0:24:15 > 0:24:18thought he'd had his bacon.
0:24:18 > 0:24:21It's now down to about the size of an orange
0:24:21 > 0:24:25but travelling at 120 miles an hour or so, it comes as quite a shock.
0:24:25 > 0:24:31It's rather like being hit by a fast bowler with a cricket ball.
0:24:31 > 0:24:33And that would be painful,
0:24:33 > 0:24:37but where in the heavens had this single block of ice come from
0:24:37 > 0:24:39in the middle of a summer's day?
0:24:39 > 0:24:44Could it in some way be a mega-sized relation to hail?
0:24:44 > 0:24:49For hail to form, you need one of these - cumulonimbus,
0:24:49 > 0:24:53giant storm clouds that climb to enormous heights.
0:24:53 > 0:24:57At the top, the air temperature is cold enough for ice crystals to form
0:24:57 > 0:25:02and as these are jostled around inside the cloud, they grow and grow
0:25:02 > 0:25:05until eventually, they're forced down to earth,
0:25:05 > 0:25:08either because they've got too heavy
0:25:08 > 0:25:11or a strong downdraught from the storm pushes them out.
0:25:13 > 0:25:18Darren Bett is one of the BBC's weather forecasters.
0:25:20 > 0:25:24There are cases of hailstones the size of golf balls,
0:25:24 > 0:25:27hailstones even the size of a grapefruit.
0:25:27 > 0:25:31But what fell on a car in Florida in 2007 was way bigger
0:25:31 > 0:25:33than a grapefruit.
0:25:33 > 0:25:36What started as a 45-centimetre block of ice
0:25:36 > 0:25:39not only took out the back windscreen,
0:25:39 > 0:25:43but also sent the car a metre into the air with the impact.
0:25:43 > 0:25:46These larger chunks of ice are very, very heavy.
0:25:46 > 0:25:50I don't know of any updraughts that can keep them up in the air
0:25:50 > 0:25:53and grow them in the same way that a hailstorm can.
0:25:53 > 0:25:57Also, they seem to be coming from cloudless skies.
0:25:57 > 0:26:01Not only are they too heavy to be hail,
0:26:01 > 0:26:03but without a cloud to have formed them,
0:26:03 > 0:26:07the hail theory is, frankly, out the window.
0:26:07 > 0:26:09So where could the finger point next?
0:26:09 > 0:26:14If you look up, you're likely to see one potential culprit flying by.
0:26:14 > 0:26:17Could they have fallen from a plane?
0:26:20 > 0:26:23Padhraic Kelleher is the Head of Airworthiness
0:26:23 > 0:26:25at the Civil Aviation Authority.
0:26:25 > 0:26:28If the ice is completely clear,
0:26:28 > 0:26:32then we are pretty sure it's most likely not an aviation source.
0:26:32 > 0:26:36But sometimes we have reports of ice that's coloured.
0:26:36 > 0:26:40That usually suggests there is chemical content,
0:26:40 > 0:26:43which we do use in treating toilet waste.
0:26:45 > 0:26:49So, beware of blue ice. Its origins could be somewhat unsavoury.
0:26:49 > 0:26:53But then only 5% of reported cases in the UK
0:26:53 > 0:26:55can be linked to planes, anyway.
0:26:57 > 0:27:01So that leaves us scratching our heads about the other 95%.
0:27:01 > 0:27:07Experts have named these unidentified falling objects as megacryometeors
0:27:07 > 0:27:11and with a name like that, it would suggest they came from space.
0:27:11 > 0:27:15But on closer inspection, they don't have enough dust or iron content
0:27:15 > 0:27:17to be typical meteors.
0:27:17 > 0:27:22For now, the scientists are actually out of ideas.
0:27:22 > 0:27:27So, for the moment, large chunks of ice falling to Earth
0:27:27 > 0:27:31remain a mystery, but there is one thing that's certain -
0:27:31 > 0:27:33if one hits you, it's going to hurt you.
0:27:33 > 0:27:38The largest ever recorded weighed 90 kilograms, that's 200lbs.
0:27:38 > 0:27:43When that reached terminal velocity, at a speed of around 100mph,
0:27:43 > 0:27:47well, that would be like being hit by an African elephant.
0:27:48 > 0:27:50Not good.
0:27:50 > 0:27:52Indeed.
0:27:52 > 0:27:53All these stories remind us
0:27:53 > 0:27:57that nature can do the most unexpected of things,
0:27:57 > 0:28:01from the spine-chilling end that befell a herd of musk oxen,
0:28:01 > 0:28:05to the mysterious chunks of ice that leave the scientific world flummoxed.
0:28:05 > 0:28:09So much of the natural world can not only shock us,
0:28:09 > 0:28:13but also leave us searching for answers.
0:28:17 > 0:28:19Next, we're taking to the oceans
0:28:19 > 0:28:22where the sea can do the most alien of things.
0:28:24 > 0:28:29A phenomenon that makes the night sea glow so bright
0:28:29 > 0:28:30it's visible from space.
0:28:30 > 0:28:35And a natural event that's fatal to thousands of seabirds.
0:28:36 > 0:28:38But we start Down Under,
0:28:38 > 0:28:41where otherworldly scenes pulled in a big crowd.
0:28:43 > 0:28:48Australia, the epitome of beach culture - sand, sea and surf.
0:28:48 > 0:28:50But what happens when this...
0:28:50 > 0:28:53turns to this?
0:28:58 > 0:29:03Overnight the ocean had been whipped up into something quite extraordinary.
0:29:03 > 0:29:07When the waves pushed in it would push the foam up real higher.
0:29:11 > 0:29:17When it hit Yamba in New South Wales on 24 August, 2007,
0:29:17 > 0:29:18it smothered everything.
0:29:18 > 0:29:23Locals flooded to the beach to join in the foam party.
0:29:23 > 0:29:27The waves were lifting the foam, but you couldn't see breaking waves.
0:29:27 > 0:29:31We even had one member of my wife's family disappear in it
0:29:31 > 0:29:34and it took us quite a while to find him.
0:29:34 > 0:29:37The site was so spectacular
0:29:37 > 0:29:40it didn't take long for images of people coated in foam
0:29:40 > 0:29:43to flash around the world.
0:29:43 > 0:29:46Yamba became known as the "Cappuccino Coast".
0:29:48 > 0:29:52But what was going on? Why had the sea whipped up like cream?
0:29:52 > 0:29:56To find out, we're heading to the National Oceanography Centre,
0:29:56 > 0:30:00in Southampton, where Dr Simon Boxall is a coastal expert.
0:30:01 > 0:30:05Over the last few years, we've seen some fantastic sea foam events.
0:30:05 > 0:30:09A lot of people assume it's caused by pollution. In actual fact, it's not.
0:30:09 > 0:30:11It's caused by these things.
0:30:11 > 0:30:14It's caused by plankton - phytoplankton, primarily.
0:30:14 > 0:30:18And plankton is the basis of much of the life in the sea,
0:30:18 > 0:30:20the bottom link in the food chain,
0:30:20 > 0:30:25feeding everything from tiny fish to the giants of the ocean.
0:30:26 > 0:30:28And plankton supports us, too.
0:30:28 > 0:30:32Much of the Earth's oxygen is produced by these tiny organisms.
0:30:33 > 0:30:38As the phytoplankton die, they release various compounds.
0:30:38 > 0:30:42When these things are agitated, they create sea foam.
0:30:42 > 0:30:46They act like surfactants, almost like washing up liquid, in some ways.
0:30:46 > 0:30:50This combination of strong blooms and strong wave activity
0:30:50 > 0:30:54produces the most spectacular sea foam shows on the planet.
0:30:56 > 0:31:01In the case at Yamba, the event happened after inland floods
0:31:01 > 0:31:04washed nutrients from farmland soil out to sea.
0:31:04 > 0:31:08These enriched waters are the perfect habitat
0:31:08 > 0:31:10for a massive bloom of plankton.
0:31:11 > 0:31:14Now, when the plankton was healthy, nothing happened.
0:31:14 > 0:31:19But when the bloom started to die a surfactant was given off
0:31:19 > 0:31:22which, when whipped up by a storm, produced foam on a gigantic scale.
0:31:32 > 0:31:34Right, whilst on one side of the world
0:31:34 > 0:31:36the Cappuccino Coast is a tourist attraction,
0:31:36 > 0:31:41we travel next across the Pacific to the Washington coastline,
0:31:41 > 0:31:44where, in November 2009, the foam that whipped up
0:31:44 > 0:31:47had altogether more serious consequences.
0:31:47 > 0:31:51A full-blown wildlife crisis tonight on the north-west coastline.
0:31:51 > 0:31:55Thousands of seabirds are dying from a slimy foam
0:31:55 > 0:31:58that stretches from Washington's Olympic coastline
0:31:58 > 0:32:01all the way to the Northern Oregon coastline.
0:32:01 > 0:32:03Foam on the beach is not unusual,
0:32:03 > 0:32:04but this foam was killer foam.
0:32:06 > 0:32:09This was ugly smelling, ugly looking
0:32:09 > 0:32:11and incredibly tall.
0:32:11 > 0:32:14Thousands of seabirds, dead and dying,
0:32:14 > 0:32:18along 300 miles of the American West Coast.
0:32:18 > 0:32:20Offshore species showing up on land,
0:32:20 > 0:32:24in scenes reminiscent of a man-made disaster.
0:32:24 > 0:32:28The scope of the situation is hard for even the scientists to grasp.
0:32:28 > 0:32:32The Wildlife Centre Of The North Coast, near Astoria,
0:32:32 > 0:32:35- is flat-out overwhelmed.- Even though I've been picking them up,
0:32:35 > 0:32:38I go back to the same place, there's more birds.
0:32:38 > 0:32:43The birds in the foam were offshore species - murres, grebes and loons -
0:32:43 > 0:32:47only seen on the beach when they're really in trouble.
0:32:47 > 0:32:51So, volunteers started getting themselves organised
0:32:51 > 0:32:53to head out and rescue them.
0:32:53 > 0:32:55Typically, when I come out here and walk on the beach,
0:32:55 > 0:32:58I could walk for a mile or two and see one or two dead birds.
0:32:58 > 0:33:02On this day, obviously, there were literally hundreds you could see.
0:33:02 > 0:33:07They were wet, sandy. It was really a mess.
0:33:07 > 0:33:10I've never seen anything like that.
0:33:10 > 0:33:13Wildlife centres cleared the decks,
0:33:13 > 0:33:15but they simply couldn't keep up with the deluge.
0:33:15 > 0:33:18Every little available space we could find
0:33:18 > 0:33:22we walled off to make an enclosure. We had kennels up on the counters.
0:33:22 > 0:33:24Just about any available space we could find.
0:33:25 > 0:33:28As the rescue effort struggled to keep up,
0:33:28 > 0:33:32even the scientists were overwhelmed by this event.
0:33:32 > 0:33:37Julia Parrish is an ornithologist at the University of Washington.
0:33:37 > 0:33:40I've been a seabird biologist for about 25 years
0:33:40 > 0:33:42and I've seen a lot of death.
0:33:42 > 0:33:48This event was huge. I've never seen anything like it.
0:33:48 > 0:33:51I hope never to see anything like it again.
0:33:52 > 0:33:57So, what was causing such an enormous and devastating event?
0:33:57 > 0:34:00Well, as the scientists looked to figure it out,
0:34:00 > 0:34:05they came across something in the archives that might help them.
0:34:07 > 0:34:12Two years earlier, 800 miles down the coast at Monterey Bay,
0:34:12 > 0:34:16in California, seabirds had died in their thousands.
0:34:16 > 0:34:19Raphe Kudela, at the University of Santa Cruz,
0:34:19 > 0:34:23is an ocean ecologist and he was involved in unravelling the mystery.
0:34:24 > 0:34:27Initially, when the birds started coming in,
0:34:27 > 0:34:29it was assumed it was from an oil spill.
0:34:29 > 0:34:32But as soon as they tested them,
0:34:32 > 0:34:35they realised there was no petroleum products on the birds.
0:34:35 > 0:34:39At that point, it gets classified as something called a mystery spill.
0:34:41 > 0:34:44At the time, there was a natural event happening out at sea
0:34:44 > 0:34:48that's known as a red tide,
0:34:48 > 0:34:52a mass of algae that group together in huge numbers.
0:34:52 > 0:34:54Some of these can be very toxic.
0:34:54 > 0:34:57But this particular dinoflagellate algae
0:34:57 > 0:35:00had never been recorded causing any harm before.
0:35:02 > 0:35:06We were trying to work out the link between the dinoflagellates,
0:35:06 > 0:35:10that are supposed to be harmless, and what's happening to these birds.
0:35:10 > 0:35:12We had this red tide offshore,
0:35:12 > 0:35:14but on the beach there was this foam piling up.
0:35:14 > 0:35:17We assumed the foam had something to do with the algae.
0:35:17 > 0:35:20But we didn't know exactly what was going on.
0:35:23 > 0:35:25The birds in the foam looked bedraggled.
0:35:27 > 0:35:29And these are species
0:35:29 > 0:35:32that spend much of their time diving underwater,
0:35:32 > 0:35:35almost swimming, to catch their prey.
0:35:37 > 0:35:41To stay warm, they rely on their terribly efficient down layer,
0:35:41 > 0:35:44which is not only insulating but, vitally, waterproof,
0:35:44 > 0:35:47keeping the cold water away from their skin.
0:35:53 > 0:35:56Yet, the birds on the beach were freezing.
0:35:56 > 0:35:58So Raphe and his colleagues began experimenting,
0:35:58 > 0:36:01to see what was happening to their feathers.
0:36:02 > 0:36:04If you dip feathers into normal water...
0:36:06 > 0:36:09I just dipped that in and nothing happens.
0:36:09 > 0:36:11The feather is still nice and fluffy.
0:36:11 > 0:36:13But when we dip it into the foam...
0:36:16 > 0:36:20..instead of popping back out, it's just all clodded down.
0:36:20 > 0:36:23So the top of the feather is completely covered
0:36:23 > 0:36:24in this sort of nasty goo.
0:36:24 > 0:36:27Eventually, all that down is going to be collapsed
0:36:27 > 0:36:29all the way against the quill, the feather.
0:36:29 > 0:36:32and it's no longer waterproof, at all.
0:36:32 > 0:36:36It's as if you went swimming in the cold ocean, in a wetsuit,
0:36:36 > 0:36:38and all of a sudden your wetsuit dissolved.
0:36:38 > 0:36:40You wouldn't last very long.
0:36:40 > 0:36:42And that's exactly what happened to the birds.
0:36:42 > 0:36:48The result was the largest known mortality of marine birds
0:36:48 > 0:36:52anywhere in the world ever, due to an algal bloom.
0:36:54 > 0:36:578,000 bodies washed up in this event.
0:36:57 > 0:37:00It's thought many thousands more died out at sea.
0:37:00 > 0:37:03But for the rescued birds, there was hope,
0:37:03 > 0:37:05as the scientists found a relatively simple fix.
0:37:07 > 0:37:10One of the things that came out of our study is,
0:37:10 > 0:37:13they very quickly realised that, if you get to the birds
0:37:13 > 0:37:17before they actually die, all you need to do is put them in clean water
0:37:17 > 0:37:21and keep them warm and they can clean themselves.
0:37:21 > 0:37:23It's just a matter of getting rid of this foam
0:37:23 > 0:37:25and keeping them from going into hypothermia.
0:37:25 > 0:37:29At the rescue centres, this was encouraging news.
0:37:29 > 0:37:32But the birds were in such poor condition,
0:37:32 > 0:37:34it was a fight against the clock.
0:37:36 > 0:37:38To get the birds back to being waterproof again
0:37:38 > 0:37:42and getting the toxic algae off of them, we would swim them.
0:37:42 > 0:37:45So we would get as many as we could in here at one time.
0:37:45 > 0:37:47They'd be in here just a very short period.
0:37:47 > 0:37:50And the water, of course, would turn just yellow-green.
0:37:50 > 0:37:52It was pretty horrible to see.
0:37:52 > 0:37:56It took more than one washing to get that algae off of them.
0:37:56 > 0:37:59By about three days of washing, three or four,
0:37:59 > 0:38:01we started noticing the difference.
0:38:05 > 0:38:07For the lucky ones,
0:38:07 > 0:38:11intensive care from the volunteers restored them to health.
0:38:11 > 0:38:15And with their waterproofing back, many were capable of returning home.
0:38:20 > 0:38:24Scientists think that this incident didn't have any long-term effects
0:38:24 > 0:38:26on the seabird populations.
0:38:26 > 0:38:28You see, nature is terribly resilient.
0:38:28 > 0:38:30It always seems to bounce back,
0:38:30 > 0:38:34even when it's been faced with what appears to be total devastation.
0:38:34 > 0:38:39Nevertheless, it is surprising that an organism as small as algae
0:38:39 > 0:38:42can cause so much trouble around the world.
0:38:44 > 0:38:47But it's not all death and destruction.
0:38:47 > 0:38:49Algal blooms can play host
0:38:49 > 0:38:52to something altogether more spectacular.
0:38:52 > 0:38:55For this story, we're travelling to the Indian Ocean,
0:38:55 > 0:39:00where a phenomenon took place that was nothing short of magical.
0:39:03 > 0:39:07In 1982, Hywel Phillips was the captain of a tanker
0:39:07 > 0:39:09crossing the Persian Gulf
0:39:09 > 0:39:11when his ship sailed into what looked like another planet.
0:39:13 > 0:39:18A dull green glow is the only way I can explain it.
0:39:18 > 0:39:23And it was a weird, a really weird feeling,
0:39:23 > 0:39:28because you felt as if you were in a sphere
0:39:28 > 0:39:33of light green translucence,
0:39:33 > 0:39:36which stretched from horizon to horizon.
0:39:36 > 0:39:40You couldn't tell the difference between the sky and the sea.
0:39:40 > 0:39:45There was enough light given off by this glow to see objects
0:39:45 > 0:39:47very clearly on the bridge.
0:39:47 > 0:39:50A most spectacular, spectacular sight.
0:39:52 > 0:39:55So, what on Earth could this spectacular sight be?
0:39:55 > 0:40:00What could make the ocean glow so bright you lose all sense of space?
0:40:02 > 0:40:05Well, actually, the ability to give off light
0:40:05 > 0:40:08is one of the great wonders of the natural world.
0:40:08 > 0:40:11You might be familiar with fireflies,
0:40:11 > 0:40:14tiny insects that can glow in the dark.
0:40:15 > 0:40:18But bioluminescence is mostly found in the seas,
0:40:18 > 0:40:20where a plethora of living things,
0:40:20 > 0:40:25from octopus and fish, down to single-cell bacteria and algae,
0:40:25 > 0:40:28have the incredible power to emit their own light.
0:40:31 > 0:40:33It's all down to chemical reactions.
0:40:33 > 0:40:37When these take place inside the creature or organism,
0:40:37 > 0:40:38the result is a burst of energy,
0:40:38 > 0:40:43appearing in the form of photons, which makes visible light.
0:40:46 > 0:40:51But emitting light so the entire sea glows from horizon to horizon?
0:40:51 > 0:40:55Is bioluminescence really capable of such incredible scale?
0:40:55 > 0:40:59Well, Steve Haddock is a bioluminescence specialist
0:40:59 > 0:41:02from the Monterey Bay Research Institute in California.
0:41:02 > 0:41:05It's one of the legends of bioluminescence.
0:41:05 > 0:41:09If you work in the field, it's one of the stories people always tell,
0:41:09 > 0:41:12but rarely witness themselves.
0:41:13 > 0:41:15This legend has evolved through history,
0:41:15 > 0:41:20with ships reporting bioluminescent oceans for centuries.
0:41:20 > 0:41:23The folklore of what's become known as "milky seas"
0:41:23 > 0:41:27captured the imagination of a satellite meteorologist
0:41:27 > 0:41:29at the Naval Research Lab in California.
0:41:32 > 0:41:33Using satellites,
0:41:33 > 0:41:37Steve Miller decided to go in search of a milky sea,
0:41:37 > 0:41:40to move these tall tales from legend to reality.
0:41:41 > 0:41:44It was an exciting idea for us to go after this with satellite imagery,
0:41:44 > 0:41:47because it's never been done before.
0:41:47 > 0:41:52The question was, are these ocean surfaces glowing bright enough
0:41:52 > 0:41:54for the satellites to see?
0:41:54 > 0:41:59Well, to find out, he first needed a sighting to investigate.
0:41:59 > 0:42:04He came across a report from 1996, off the coast of Somalia.
0:42:04 > 0:42:09A ship, the SS Lima, had reported crossing a sea of milky white.
0:42:09 > 0:42:12So, Steve trawled through the archives of satellites
0:42:12 > 0:42:15until he found one that matched.
0:42:17 > 0:42:19We brought up the satellite imagery,
0:42:19 > 0:42:21we saw what appeared to be a smudge on the screen.
0:42:21 > 0:42:24But it wouldn't go away when we moved the screen around
0:42:24 > 0:42:27and it wouldn't go away when we wiped.
0:42:27 > 0:42:29So when we started to enhance this satellite image,
0:42:29 > 0:42:31the smudge just got brighter and brighter.
0:42:31 > 0:42:33"OK, that's interesting."
0:42:33 > 0:42:39But then when we overlaid the points where the steamship Lima
0:42:39 > 0:42:43had first crossed the water and exited the glowing waters,
0:42:43 > 0:42:47those points lined up exactly with the boundaries of this smudge.
0:42:47 > 0:42:51The hair on the back of my neck just rose up.
0:42:51 > 0:42:55It was one of those Eureka moments in science, that we have something here.
0:42:55 > 0:42:58It's almost like having an image of Bigfoot or the Loch Ness Monster.
0:43:00 > 0:43:02Finally, there was photographic proof
0:43:02 > 0:43:05that this legend was, in fact, true.
0:43:05 > 0:43:06And, for the first time,
0:43:06 > 0:43:10scientists could actually see its staggering scale.
0:43:10 > 0:43:13What we're talking about here is a patch of sea
0:43:13 > 0:43:16the size of the US state of Connecticut.
0:43:16 > 0:43:20And it's emitting light so bright that it was visible from space.
0:43:21 > 0:43:24Now, normally bioluminescence is small-scale,
0:43:24 > 0:43:26intermittent bursts of light.
0:43:26 > 0:43:31So how could hundreds of square miles glow continuously?
0:43:31 > 0:43:35Well, the scientists believe it all begins with an algal bloom which,
0:43:35 > 0:43:40in its dying phase, is colonised by huge numbers of bacteria.
0:43:40 > 0:43:44Then, a very special phenomenon called quorum sensing is triggered,
0:43:44 > 0:43:47resulting in this spectacular light show.
0:43:48 > 0:43:52Quorum sensing is this requirement for the bacteria to get together
0:43:52 > 0:43:56and detect that I'm existing with a bunch of similar bacteria
0:43:56 > 0:43:58in a very high concentration right now.
0:43:58 > 0:44:00They signal with chemical cues to each other.
0:44:00 > 0:44:05That actually turns on the pathway that starts light production.
0:44:05 > 0:44:09So, the numbers of bacteria that we estimated for this event
0:44:09 > 0:44:14were 4 x 10 of the 22nd.
0:44:14 > 0:44:16If you can imagine trying to count to a trillion
0:44:16 > 0:44:21and then do that 40 billion times, it's an unimaginably large number.
0:44:22 > 0:44:26So, it's likely the milky sea grew from trillions of bacteria
0:44:26 > 0:44:29feeding on dying algae.
0:44:29 > 0:44:32But until they can get out there to experience one first-hand,
0:44:32 > 0:44:35much of this is just hypothesis.
0:44:35 > 0:44:39It's been my dream ever since we saw one on satellite
0:44:39 > 0:44:44to actually be able to go out and get into one of these things.
0:44:44 > 0:44:47I've joked with Steve Haddock a couple of times
0:44:47 > 0:44:50about us forming a SWAT team
0:44:50 > 0:44:53and just being able to see one of these happening from the satellite
0:44:53 > 0:44:56and then fly out there really quick and get into one.
0:44:56 > 0:45:00I would love to get out to sample it, see how deep it is.
0:45:00 > 0:45:04We're just speculating on how far below the surface this layer is.
0:45:04 > 0:45:07Who wouldn't want to be in that sort of situation,
0:45:07 > 0:45:12where you could experience something so surreal, so incredible,
0:45:12 > 0:45:14that it just defies your imagination?
0:45:14 > 0:45:19I consider myself extremely lucky with what I have seen at sea.
0:45:26 > 0:45:31This magical phenomenon looks set to remain a mystery.
0:45:31 > 0:45:3670% of the world's milky seas occur off of the coast of Somalia.
0:45:36 > 0:45:39With all of the pirate activity there,
0:45:39 > 0:45:43there's little likelihood of much further exploration
0:45:43 > 0:45:44in the near future.
0:45:44 > 0:45:47But I like the fact that on our tiny planet
0:45:47 > 0:45:51nature still has plenty of secrets for us to decipher.
0:45:53 > 0:45:56From the fun foam that whips up in Australia,
0:45:56 > 0:46:00to the killer foam of the American West Coast.
0:46:02 > 0:46:05To the pure magic of the glowing ocean.
0:46:05 > 0:46:09All of these stories show us that even the smallest things in nature,
0:46:09 > 0:46:14tiny organisms, have the power of shock and awe.
0:46:16 > 0:46:20Our next weird events might shake you to your very foundations.
0:46:20 > 0:46:23When things happen deep in the earth,
0:46:23 > 0:46:26they can have devastating effects on the surface.
0:46:26 > 0:46:29From the school playground that disappeared in China,
0:46:29 > 0:46:32to the houses that were wiped from a suburban street.
0:46:35 > 0:46:38But we start in America's Sunshine State,
0:46:38 > 0:46:42where something altogether larger was at the mercy of the Earth.
0:46:47 > 0:46:51Large parts of Florida provide a wetland paradise for wildlife.
0:46:51 > 0:46:53And Lake Jackson was no exception.
0:46:56 > 0:47:00This pristine, six-square-mile freshwater lake
0:47:00 > 0:47:03absolutely teamed with wildlife.
0:47:03 > 0:47:07It was home to dozens of species of bird,
0:47:07 > 0:47:11including snowy egrets and little blue herons.
0:47:13 > 0:47:17American alligators swam in its crystal clear waters.
0:47:17 > 0:47:20It really was a wildlife haven
0:47:20 > 0:47:24and a much loved natural resource for local residents.
0:47:29 > 0:47:35But in 1999, Florida was hit by a terrible drought.
0:47:35 > 0:47:39For months on end, no rain fell and Lake Jackson got lower,
0:47:39 > 0:47:41and lower, and lower.
0:47:43 > 0:47:45Michael Hill from the Wildlife And Fish Commission
0:47:45 > 0:47:48records water levels in the region.
0:47:48 > 0:47:51And his gauge was showing him something quite extraordinary.
0:47:53 > 0:47:57I monitored the water levels pretty often, every few days.
0:47:57 > 0:48:00And there's one particular day, just in early September,
0:48:00 > 0:48:03I saw it go down a couple of feet in one day.
0:48:05 > 0:48:08I came back and it had gone down another two feet.
0:48:10 > 0:48:14The lake was disappearing faster than anyone could have predicted.
0:48:14 > 0:48:18And it was beyond anything you'd expect to see from a drought.
0:48:22 > 0:48:26For the creatures of the lake, the situation was becoming critical.
0:48:28 > 0:48:31Water management expert Tyler McMillan could not believe
0:48:31 > 0:48:32what was happening.
0:48:34 > 0:48:37The water was swirling and draining very quickly.
0:48:37 > 0:48:40There were so many fish in the pool
0:48:40 > 0:48:43that it was almost boiling with fish.
0:48:43 > 0:48:46Look at this. No need for a rod and line,
0:48:46 > 0:48:49these opportunists were hauling out fish by the armload.
0:48:51 > 0:48:54It was incredible that people were standing in these muddy creeks,
0:48:54 > 0:48:57looking like bears, that you'd see in Alaska.
0:48:57 > 0:48:59They were feeling the bass hit their feet
0:48:59 > 0:49:02and they were throwing it up on the bank.
0:49:02 > 0:49:07But it wasn't just the fish that were quickly running out of water.
0:49:07 > 0:49:10Other lake residents, like terrapins, were desperately trying to escape
0:49:10 > 0:49:14as the rapidly dwindling lake reached an all-time low.
0:49:14 > 0:49:16With nowhere else to go,
0:49:16 > 0:49:20some of these desperate animals went for any water they could find.
0:49:22 > 0:49:24Are you videoing it?
0:49:24 > 0:49:27I am video-taping everything right now.
0:49:27 > 0:49:28Let me go down to the water
0:49:28 > 0:49:31and look at the alligator in our pool...
0:49:33 > 0:49:36..that Daddy is about to lasso.
0:49:36 > 0:49:38Yeah, we'll see!
0:49:38 > 0:49:40But you guys sit.
0:49:41 > 0:49:44You fall in there and I'll kill you.
0:49:49 > 0:49:50Oh, my. All right, kids.
0:49:50 > 0:49:52Back this way.
0:49:55 > 0:49:56How cool was that?
0:50:01 > 0:50:02Meanwhile, back at the lake,
0:50:02 > 0:50:05the last of the water was rapidly draining away.
0:50:05 > 0:50:08On the 16th of September 1999,
0:50:08 > 0:50:10this was revealed.
0:50:13 > 0:50:16There was a gaping hole in the bottom of the lake.
0:50:16 > 0:50:20It was, quite literally, as if someone had pulled the plug
0:50:20 > 0:50:21out of a giant bathtub.
0:50:23 > 0:50:25And Lake Jackson disappeared.
0:50:25 > 0:50:28And with it, sadly, went much of its wildlife.
0:50:30 > 0:50:35But how could a huge hole open up in the bottom of the lake?
0:50:35 > 0:50:39And where had it taken all the water and all of the creatures?
0:50:39 > 0:50:41It was time to call in the experts.
0:50:41 > 0:50:46Harley Means is a geologist who spent his career studying the area.
0:50:46 > 0:50:49Beneath us here, at some depth, is limestone.
0:50:49 > 0:50:52And this limestone is very porous and full of cavities.
0:50:52 > 0:50:54Through geologic time,
0:50:54 > 0:50:59these cavities can become enlarged due to acids in groundwater.
0:50:59 > 0:51:02At some point, when the conditions are appropriate,
0:51:02 > 0:51:04you can have a collapse.
0:51:04 > 0:51:07The mysterious hole that the water had disappeared into
0:51:07 > 0:51:09was what's known as a sinkhole.
0:51:09 > 0:51:11The limestone beneath the lake
0:51:11 > 0:51:14had gradually dissolved away from underneath
0:51:14 > 0:51:18until it reached the surface, and then the hole opened up.
0:51:21 > 0:51:25With the water gone, Harley and his team of geologists
0:51:25 > 0:51:29had a unique opportunity to find out more about this special sinkhole.
0:51:30 > 0:51:33We could crawl down underground a good 20 to 25 feet
0:51:33 > 0:51:37and then laterally another 20 to 50 feet in several directions.
0:51:37 > 0:51:39For the first time,
0:51:39 > 0:51:42they could see the full extent of the hole beneath the lake
0:51:42 > 0:51:45and it was clear that any wildlife sucked down here
0:51:45 > 0:51:47sadly wouldn't have survived.
0:51:47 > 0:51:49It was dark and it was full of organic material
0:51:49 > 0:51:51that had drained through it.
0:51:51 > 0:51:54It didn't smell very good.
0:51:54 > 0:51:58Really, it was a very slimy endeavour to get down there
0:51:58 > 0:52:00and get into this cave system.
0:52:00 > 0:52:04But it gave us information, information as geologists that we could utilise.
0:52:04 > 0:52:07Harley and his team were able to confirm
0:52:07 > 0:52:09their suspicions about the hole.
0:52:09 > 0:52:12It had actually been there for a very long time,
0:52:12 > 0:52:14maybe hundreds of years.
0:52:14 > 0:52:17So, how had the lake managed to form above it?
0:52:19 > 0:52:24Well, over the years, the hole had silted up with mud and debris.
0:52:24 > 0:52:25This had formed a sort of plug.
0:52:25 > 0:52:29The drought in '99 had triggered its collapse.
0:52:30 > 0:52:33Limestone is like a sponge full of holes.
0:52:33 > 0:52:36When those holes have water in them, they're able to actually provide
0:52:36 > 0:52:39a little support to the ground over the top of them.
0:52:39 > 0:52:42But when the water is drawn out, those holes are now full of air
0:52:42 > 0:52:45and not as capable of supporting the load on top of them -
0:52:45 > 0:52:48in this case, the plug in the bottom of the sinkhole -
0:52:48 > 0:52:51and the water finally just rushed out in one final big pulse.
0:52:54 > 0:52:55All seemed lost.
0:52:55 > 0:52:59The lake was gone and, in its place, was grass and scrub.
0:53:00 > 0:53:04Where turtles and fish had swum, now rabbits and deer were grazing.
0:53:06 > 0:53:08But Tyler McMillan hadn't given up on the lake.
0:53:10 > 0:53:14The legend has it that the original Native American name of this lake
0:53:14 > 0:53:17is Okeeheepkee, which means "disappearing waters".
0:53:17 > 0:53:21If the natives were calling it that many hundreds of years ago,
0:53:21 > 0:53:25this event has been going on many, many times over the centuries.
0:53:26 > 0:53:28So, if it had drained away before,
0:53:28 > 0:53:32surely this could mean that it might refill again?
0:53:37 > 0:53:41Florida's drought finally broke in 2001.
0:53:41 > 0:53:45Sediment, washed by rainwater, replugged the sinkhole,
0:53:45 > 0:53:48whilst the groundwater levels rose below it.
0:53:48 > 0:53:53Insects buzzed, fish grew large with an abundance of new food,
0:53:53 > 0:53:57encouraging once familiar bird species to return.
0:53:57 > 0:53:59Lake Jackson was reborn.
0:54:04 > 0:54:09The regular drying out and refilling of the lake seems catastrophic.
0:54:09 > 0:54:11But local ecologist Matt Aresco
0:54:11 > 0:54:15is strangely unconcerned about the impact of this cycle.
0:54:15 > 0:54:18It's going to keep drying and refilling.
0:54:18 > 0:54:20And it's good that it does that.
0:54:20 > 0:54:23It's part of the ecology of the lake.
0:54:23 > 0:54:25It's good for the species that live in the lake
0:54:25 > 0:54:30and it's a really unique ecosystem that you don't find anywhere else.
0:54:30 > 0:54:33Lake Jackson was once again bursting with life.
0:54:33 > 0:54:38Let's hope it's a while before the plug gets pulled again.
0:54:39 > 0:54:41An incredible story from America there.
0:54:41 > 0:54:46But, you know, the UK does have its own fair share of sinkholes.
0:54:46 > 0:54:49Ripon is a city built partially on gypsum
0:54:49 > 0:54:53and it has at least 40 of these things.
0:54:53 > 0:54:56In 1997, a sinkhole appeared on the edge of town
0:54:56 > 0:54:58and a building collapsed into it.
0:54:58 > 0:55:01But if you thought things were bad in Ripon,
0:55:01 > 0:55:04wait until you see the devastation sinkholes have caused
0:55:04 > 0:55:06in other parts of the world.
0:55:06 > 0:55:11What happened in Guatemala City was quite unlike anything.
0:55:15 > 0:55:19In June of 2010, a massive hole opened up
0:55:19 > 0:55:23in the middle of a suburban street, swallowing a three-storey building.
0:55:23 > 0:55:29Terrified local residents had a lucky escape and were evacuated
0:55:29 > 0:55:33when the 60-metre deep chasm appeared suddenly during the night.
0:55:35 > 0:55:39In southern China, a school playground suffered a similar fate.
0:55:39 > 0:55:42This time the hole was 80 metres wide
0:55:42 > 0:55:45and continued to grow for almost six months.
0:55:47 > 0:55:49A little closer to home,
0:55:49 > 0:55:52this time a small town in central Germany
0:55:52 > 0:55:54suffered a devastating collapse.
0:55:54 > 0:55:59Houses nearby had to be evacuated, and two car owners,
0:55:59 > 0:56:01well, they were left with a bit of a conundrum.
0:56:03 > 0:56:05British geologist Tony Cooper is an expert
0:56:05 > 0:56:07in these terrifying sinkholes.
0:56:11 > 0:56:16What has happened is that material has gradually washed away underground
0:56:16 > 0:56:18and the cavity has got very large at depth.
0:56:18 > 0:56:21And then the material has continued to wash away
0:56:21 > 0:56:23and collapse over that cavity.
0:56:23 > 0:56:26And that cavity has worked its way up to the surface.
0:56:26 > 0:56:27At the surface,
0:56:27 > 0:56:30especially in towns and suchlike,
0:56:30 > 0:56:34you will have things like roads, concrete structures and so on.
0:56:34 > 0:56:38These can actually bridge quite significant holes in the ground
0:56:38 > 0:56:40until it gets to a point where it is so large
0:56:40 > 0:56:44that nothing will bridge it, and then you'll get a catastrophic collapse.
0:56:45 > 0:56:50In Guatemala, floodwater from a recent tropical cyclone
0:56:50 > 0:56:53had washed away rock and sediments under the city.
0:56:53 > 0:56:58It was a remarkably rapid process, with devastating consequences.
0:57:01 > 0:57:03China has huge areas of limestone.
0:57:03 > 0:57:05And, although no-one knew it,
0:57:05 > 0:57:10the school playground that collapsed was right on top of a massive cave.
0:57:15 > 0:57:16And in Germany?
0:57:16 > 0:57:19Well, this time it was the dissolving of gypsum
0:57:19 > 0:57:22that caused the land to give way.
0:57:23 > 0:57:27But, whatever the rock, however the holes formed,
0:57:27 > 0:57:29the consequences are the same.
0:57:32 > 0:57:35For all of these sinkholes,
0:57:35 > 0:57:37their power lies in the element of surprise.
0:57:39 > 0:57:42Each of these holes appeared without warning
0:57:42 > 0:57:44and it's impossible to predict
0:57:44 > 0:57:46where the next one will open up.
0:57:46 > 0:57:50But, wherever it happens, we will be left standing in awe
0:57:50 > 0:57:53at the unpredictable and destructive side of nature.
0:57:57 > 0:57:59Whether they're weird or wonderful,
0:57:59 > 0:58:03events like these still have the power to shock and confuse us.
0:58:03 > 0:58:07And no matter how much we think we know about all the living things,
0:58:07 > 0:58:10nature still has the capacity to keep us in check
0:58:10 > 0:58:16with its many mysteries that even the best brains struggle to explain.
0:58:16 > 0:58:21And we can only imagine what incredible events
0:58:21 > 0:58:24and weird phenomena there are yet to be discovered.
0:58:50 > 0:58:51Subtitles by Red Bee Media Ltd
0:58:51 > 0:58:53E-mail us at subtitling@bbc.co.uk