Murdoch Mysteries - Season 1 Episode 3
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00:00:00Across the globe lie mysterious hidden deathtraps, ready to strike without warning.
00:00:12Their name? Sinkholes.
00:00:16Sinkholes are really scary. They are terrifying. An abyss which seems to be never-ending.
00:00:25Over thousands of years, ancient civilization feared their awesome power.
00:00:30They thought this was punishment from the gods.
00:00:33And revered their life-giving properties.
00:00:36They are portals to the underworld.
00:00:39Now, these ticking time bombs are swallowing buildings.
00:00:43Once a sinkhole is formed, it changes everything.
00:00:45The floor has collapsed in the back area.
00:00:49And ruining lives.
00:00:51All I was thinking was, like, I have to get myself out, like, I have a child.
00:00:55But while many spell death and destruction,
00:00:58groundbreaking new research shows sinkholes can also be gateways to hidden worlds.
00:01:05From never-before-seen living environments.
00:01:08A forest ecosystem, wonderful.
00:01:10It is one of the most amazing things in the world.
00:01:14Subterranean adventure spots.
00:01:16You've got no idea, it's epic.
00:01:19And archaeological wonders.
00:01:22I'm standing on limestone right now and started picking up flakestone artifacts.
00:01:27Rewriting everything we thought we knew.
00:01:30There's something ever so mysterious about them.
00:01:34Can mankind ever learn to live with sinkholes?
00:01:39THE UNDERWORLD
00:01:47Cefna, USA, February 2013.
00:01:52A quiet town of around 8,000 people, located in the state of Florida.
00:01:58And one fateful day, this small community was suddenly shaken to its core.
00:02:04It was just a normal day.
00:02:07Everything was normal down here.
00:02:09Then it happened.
00:02:16The call came in as a structural collapse of some sort
00:02:20with somebody in a hole inside of a house.
00:02:24You get the adrenaline rush, the adrenaline starts flowing,
00:02:27and your mind starts racing as to what could potentially be happening in that emergency.
00:02:33I told my wife I thought we was going to have a fire
00:02:36because there was a lot of fire engines out.
00:02:40I come out, and that's when they told me there was a sinkhole over there.
00:02:47A sinkhole had appeared underneath the bedroom of 37-year-old Jeffrey Bush.
00:02:54The ground beneath him had given way without warning in the middle of the night.
00:03:00Swallowing up the room's entire contents, including Jeffrey himself.
00:03:05I heard him yell when I heard a noise,
00:03:08and then when I ran in there and jumped in the hole and I was screaming his name,
00:03:13I could swear I heard him hollering my name to help him.
00:03:17I just couldn't do nothing.
00:03:21Captain Adam Brown was sent to help.
00:03:25It seemed like it had the potential where we actually get to use our skill set
00:03:30to make a difference and to hopefully save somebody.
00:03:32The bedroom door was open, and I had to stop myself
00:03:36because I noticed that the entire concrete flooring of that bedroom was no longer there.
00:03:42There was a hole in the ground, in the earth, below the concrete slab of the residence.
00:03:49Almost like it was cut away, you know, like a human did it.
00:03:53I was expecting to look down there and see chunks of concrete, furniture, a bed, a dresser.
00:04:01I didn't see any of that. There was obviously no human that I could see.
00:04:06There was nothing but dirt.
00:04:08Jeffrey Bush was nowhere to be seen.
00:04:12But with the 20-foot deep hole still unstable, Adam quickly evacuated the rest of the house.
00:04:20We moved our operations to the backyard of the house.
00:04:25The hole was moving periodically down to the center point.
00:04:29It was still taking dirt into it.
00:04:32We made the decision to put a listening device through the window down into the hole
00:04:40and listen to hear sounds of life.
00:04:43Despite the best efforts of the emergency services, Jeffrey could not be saved.
00:04:50His body was never recovered.
00:05:00Nobody slept.
00:05:03Officers everywhere, ambulance everywhere, news people everywhere.
00:05:10I don't think nobody around here hardly got any rest.
00:05:14Because I was worried about if we had to move.
00:05:18This was one of those calls that you never forget.
00:05:21I think about it constantly.
00:05:23I can imagine how quickly it must have taken place
00:05:27and what it was like for the gentleman that went down in the hole.
00:05:31One man died.
00:05:34But for the surviving residents, it became a living nightmare.
00:05:39You never know when they're going to pop in and pop out.
00:05:43You know, it comes and goes.
00:05:51What had caused this devastation?
00:05:54For many, Florida is a paradise known as the Sunshine State.
00:06:01But beneath its sunny exterior lies a landscape plagued
00:06:06by one of the world's most terrifying phenomena, sinkholes.
00:06:10A sinkhole is basically a cavity where material has been removed
00:06:14and then causes the layers above to collapse into it.
00:06:18They can be as small as a dinner plate or be as large as a football field.
00:06:23And they can cause all sorts of problems all over the planet.
00:06:28The town of Cefna sits in a sinkhole epicentre.
00:06:32With over 20,000 cases reported,
00:06:35this area accounts for nearly 75% of incidents in Florida.
00:06:40The occurrences of sinkholes are so frequent, it's known as Sinkhole Alley.
00:06:46They are incredibly unpredictable, and this is what makes them so dangerous.
00:06:51Sinkholes appear all over the planet, and over time,
00:06:55experts have come up with all manner of strange explanations for their existence.
00:07:04On the Mediterranean island of Malta sits a 700-year-old sinkhole,
00:07:10measuring 50 metres wide and 15 metres deep.
00:07:15This thing was a monster.
00:07:18The sinkhole is called Il Macluba, which translates as the Upside Down.
00:07:26Local legends claimed that the sinkhole came to punish a local community of wrongdoers.
00:07:34The sinkhole dates to 23 November 1343,
00:07:38and the story goes that a woman from a nearby chapel warned the people of this village
00:07:44that their ways were despicable, that they were behaving in an ungodly fashion,
00:07:49and that God would have his vengeance.
00:07:51But unfortunately, she could not save them,
00:07:54for the sinkhole appeared and engulfed the entire village and everybody with it.
00:07:59For centuries, the giant crater continued to serve as a cautionary tale for nearby communities,
00:08:06a useful piece of religious propaganda.
00:08:10People would use them as a way to ensure that the population behaved themselves,
00:08:14otherwise the gods would punish them by using sinkholes.
00:08:18And what better way to keep people behaving by threatening them that unless they're pious,
00:08:22unless they follow a good path, the path beneath them will vanish.
00:08:28Meanwhile, on the northernmost tip of Scotland,
00:08:32a sinkhole formed long ago in the legendary Smoo Cave,
00:08:38which local folklore claims was once the living quarters for the devil.
00:08:45Caves and sinkholes have often been associated with the entrance to hell itself.
00:08:53They're cold, they're dark, they were just scary places that you didn't know where they led.
00:09:01So of course, people are going to start making stories.
00:09:06Who would live in such a horrible, desolate place that goes into the earth?
00:09:11I know the devil.
00:09:15Whether it's ancient Rome, where myths tell of a soldier jumping into a giant pit
00:09:21to save the city from the gods of Hades,
00:09:24or the indigenous communities of Australia,
00:09:28who thought sinkholes were connected to a subterranean deity called the Rainbow Serpent.
00:09:35The origins of these strange structures have intrigued humanity for thousands of years.
00:09:42Sinkholes are very much in the fabric of human history.
00:09:45So even though they appear as a modern problem,
00:09:48the truth is they've been around for a very long time.
00:09:55A crucial clue to the formation of sinkholes
00:09:58could come from deep within the jungles of the Yucatan Peninsula in Mexico.
00:10:04It was here that the Maya, another great ancient civilization,
00:10:09lived near water-filled sinkholes named cenotes.
00:10:15Derived from the Yucatec Maya word sonot,
00:10:18cenote literally means a hole in the ground that is filled with water.
00:10:23The Yucatan Peninsula has very few freshwater sources.
00:10:26It doesn't have rivers, for example.
00:10:28So cenotes, being a source of freshwater, were a magnet for human occupation.
00:10:34Cenotes were incredibly sacred places
00:10:37because they were literally seen as portals to a different world.
00:10:42In times of drought or hardship,
00:10:44the communities would cast precious objects, jewels and gold,
00:10:49into this gaping chasm in the ground
00:10:51in hopes that the rains would come and that rain god Chark would bless them.
00:10:57Chichen Itza was a prominent Mayan city,
00:11:00likely attracting its first settlers in the 6th century AD.
00:11:05The spring water in the cenotes helped the people here to thrive,
00:11:09but it also served a far darker purpose.
00:11:18Archaeologists have discovered an amazing array of items
00:11:22hidden in the depths of the sacred cenote in Chichen Itza.
00:11:26But the most significant finds were not precious metals or gemstones,
00:11:31but the bones of over hundreds of men, women and children.
00:11:35The gods expected certain kinds of offerings
00:11:38and certain kinds of behaviour from humans
00:11:40in order to provide them with rains, with food, with corn.
00:11:44Of the bones analysed by archaeologists,
00:11:4780% belonged to children between 3 and 11 years old.
00:11:53The tears that parents shed when they offered their children in sacrifice
00:11:57were an important part of the magic of those rituals.
00:12:00It was a way to draw water and rain to the land.
00:12:04This was a desperate act from their parents to cast into their cenotes
00:12:09the most valuable and precious thing that they had in their lives,
00:12:13their own flesh and blood.
00:12:15This research helps us understand the role
00:12:18these ancient water-filled sinkholes played in ancient life on the Yucatan.
00:12:23But a critical question still remains.
00:12:26What created them?
00:12:29Scientists have found an even more shocking revelation.
00:12:34Many of Mexico's cenotes were formed thanks to arguably
00:12:39the most seismic event in the history of planet Earth,
00:12:43an event that wiped out the dinosaurs.
00:12:48Over 65 million years ago, an asteroid about 10km wide
00:12:53crashed into the Earth and caused a cataclysmic event.
00:12:59The asteroid hit just off the coast of the Yucatan Peninsula
00:13:04with a force of over 4 billion atomic bombs,
00:13:09triggering the mass extinction of three-quarters of the Earth's plant and animal species.
00:13:18But it also transformed the topography of the landscape itself in the Yucatan Peninsula.
00:13:24It left these fissures, these cracks in the limestone,
00:13:28which then ended up being places where limestone was weak,
00:13:31collapsed and filled with water.
00:13:33So this cataclysmic event which actually killed off the dinosaurs
00:13:37was the birth of a beautiful ring of cenotes in the Yucatan Peninsula.
00:13:43Today, 900 cenotes have been found in this ring,
00:13:47helping us to understand how some ancient sinkholes were formed.
00:13:53But there are many that weren't created by space debris hitting the Earth.
00:13:58Some sinkholes can open up without warning in seconds.
00:14:03Not all sinkholes, of course, are formed by huge asteroid collisions.
00:14:07There must be other factors at play.
00:14:16Lando Lakes, Florida, July 2017.
00:14:20Right in the heart of Sinkhole Alley, this epidemic struck again.
00:14:29This time, two homes were taken out, with seven condemned.
00:14:36Well, there's a lot of individuals over there that are scared.
00:14:39Well, it's a nice neighborhood, basically,
00:14:42but I don't know what's going to happen after all of this.
00:14:46Scientific studies show that somehow sinkhole formation in Florida is increasing.
00:14:54And its 23 million residents are quickly losing hope.
00:15:01David Wilshaw is a Florida-based geologist
00:15:04with over 20 years of experience dealing with this state-wide menace.
00:15:09I'm a first responder for sinkholes.
00:15:11When a hole in the ground opens up, I get the phone call
00:15:14and I have to be there as quickly as possible to make sure that it's a safe environment.
00:15:20One of the problems with a hole in the ground is people love to look into it.
00:15:23And that's one of the worst things you can do,
00:15:25because the hole that you see at the surface
00:15:27is much, much smaller than the hole that sits below it.
00:15:30Well, good morning. What's going on?
00:15:34What have we got?
00:15:36Sinkholes are the biggest ground hazard that we work with.
00:15:40They're a constant threat to all built development.
00:15:43Any part of Florida can be susceptible to sinkholes.
00:15:47But why is Florida such a danger zone?
00:15:50A clue comes from the type of rock that dominates underground.
00:15:55Florida is a relatively simple geology.
00:15:57There's only really one rock, and that is limestone.
00:16:02Rainwater mixes with CO2, carbon dioxide in the atmosphere.
00:16:07It forms carbonic acid.
00:16:09And that acid trickling down into the limestone literally dissolves the limestone.
00:16:15The soft makeup of limestone rock makes it highly susceptible to dissolving.
00:16:21Meaning over millions of years, the ground beneath Florida has been transformed into a death trap.
00:16:29It's had time for a lot of voids, caverns, caves to form.
00:16:34And we have a mixture of sand and clays that can collapse down into those void spaces.
00:16:42It's almost like a fuse on a time bomb.
00:16:44Because once the soil starts to move into the holes in the limestone, then time is against us.
00:16:51The more dramatic ones are where the clay that sits on top of the limestone hangs on for a day of life.
00:16:57It hangs on for as long as it can.
00:16:59And then it suddenly fails and collapses and takes a whole column of soil with it.
00:17:05And the most terrifying part, because it's nearly impossible to detect weak areas without high-tech monitoring equipment,
00:17:12these sinkholes often occur without warning.
00:17:16Where the next one will form is extremely difficult to predict.
00:17:23But in the U.S., sinkholes aren't just a Florida problem.
00:17:28Around 20% of the country's surface land is at risk.
00:17:32That's an area roughly the size of Mexico.
00:17:38On February 12th, 2014, Bowling Green in Kentucky joined the sinkhole casualty list.
00:17:46A city famed for the National Corvette Museum and its prized collection of vintage cars.
00:17:52Or at least, it was.
00:17:54911, what is your emergency?
00:17:56This is the National Corvette Museum.
00:17:58Yes, ma'am.
00:18:00The floor has collapsed in the back area.
00:18:07Eight Corvettes, and with it, over a million dollars, had almost disappeared.
00:18:14But what had caused this catastrophic collapse?
00:18:18Limestone on the ground dissolved over time.
00:18:21Limestone on the ground dissolved over time to form a giant cavern.
00:18:26Over 60 meters long, almost 12 meters wide, and over 25 meters deep.
00:18:33When the cavern's roof catastrophically gave way, it took the museum's cars with it.
00:18:40No one was sure what would happen next.
00:18:42But a huge salvage mission was able to rescue the submerged vehicles.
00:18:47Some were no more than scrap.
00:18:49Others, miraculously...
00:18:54still roadworthy.
00:18:58The sinkhole has since been covered.
00:19:01Costing 3.2 million dollars, it shows the heavy financial cost this mysterious natural phenomenon puts on local communities.
00:19:12But there are other sinkholes out there that are a little harder to explain.
00:19:20Guatemala City
00:19:26Guatemala City, a Central American metropolis, crammed with cafes, cars, and over 2 million citizens.
00:19:37And in May 2010, that city was turned upside down.
00:19:43Right in the middle of the town, at a road junction, huge hole.
00:19:4820 meters wide and reported 90 meters deep.
00:19:52Happened instantaneously. Spectacular. You can't get much more spectacular than that.
00:19:58Panic spread on the ground, as electricity poles were dragged down into the abyss, along with a three-story factory.
00:20:08Within one minute, the whole lot would have gone.
00:20:12The sinkhole that formed was one of the larger depressions that has occurred in historical time.
00:20:21For residents, it was a living nightmare, with one man reported dead.
00:20:25Nearby residents who have no other place to go fear another collapse...
00:20:29Many abandoned their homes, while others dared to take a peek into a sinkhole, deep enough to fit the Statue of Liberty inside it.
00:20:38We can probably see the bottom on that thing.
00:20:40Oh, yeah, you can.
00:20:43Hey, but now, this is crazy, though. This is really something.
00:20:46Yeah, man.
00:20:48But was it natural forces, or something more alarming?
00:20:53At the time, Guatemala had been hit by a brutal tropical cyclone, which spread floods across Central America,
00:21:01meaning a lot of additional moisture in the earth.
00:21:03But while investigating the sinkhole site, geophysicists found another crucial piece of evidence, a leaking sewage system.
00:21:13So it's a natural feature induced and accelerated by man.
00:21:18It turns out, a common trigger for the sudden and deadly appearance of sinkholes is us.
00:21:25The water flowing out of that leaking pipe moved the loose sediment, presumably deeper into the ground,
00:21:32and that created a void, which later collapsed.
00:21:37Thankfully, Guatemala City has not seen a sinkhole this size since the 2010 incident.
00:21:44But as long as there is human-made infrastructure underground, the threat of a sinkhole may never go away.
00:21:51This is a thing which can happen almost anywhere.
00:21:54Once you've got a leaking drain, you've got a problem.
00:21:58March 2023.
00:22:01Fifteen miles northwest of London, in the UK town of Watford,
00:22:06Laura Gerber, a 23-year-old personal assistant and mother of one, was returning home with her friends and partner.
00:22:14We were having a night out.
00:22:15It was just a completely normal night.
00:22:17It wasn't anything special.
00:22:20But a human-made sinkhole was about to change her life forever.
00:22:27This is the first time Laura has agreed to be interviewed about her experience.
00:22:32It was the middle of the night.
00:22:35It was completely dark.
00:22:36I was completely sober.
00:22:38Everyone was chatting inside the car.
00:22:41And as I've gotten out of the car, I've stepped backwards.
00:22:47I've disappeared, literally, into the road.
00:22:52What looked like a small puddle on a residential street was actually a flooded road.
00:22:58The road was completely flooded.
00:23:01What looked like a small puddle on a residential street was actually a flooded, three-metre-deep sinkhole,
00:23:09triggered by a burst pipe underground.
00:23:12Everything happened so quickly.
00:23:16All that kept going through my head, like, what is this? Like, what's around me?
00:23:20Because my eyes were open, so I could just see the brown water.
00:23:27It turns out it was actually sewage water.
00:23:30So I then, obviously, panicked.
00:23:33I've gone to then shout and actually swallowed water, which was even worse.
00:23:41Laura was completely submerged, unable to breathe, and no one had realised that she was missing.
00:23:49If she had sank any deeper into the sinkhole, a current at the bottom would have swept her away for good.
00:23:55All I was thinking was, like, I have to get myself out.
00:23:58Like, I have a child, I can't leave my child with no mum.
00:24:01I have to get out of the sinkhole.
00:24:05So I kind of put my arms up and grabbed them to the side.
00:24:09As you do in a swimming pool, when you pull yourself up, that's what I did.
00:24:14Using all her strength, Laura was finally able to pull herself out.
00:24:20I just stood there for a good few minutes, just frozen.
00:24:24Didn't know what to do, didn't really say anything.
00:24:27Kind of in shock, just stood there.
00:24:35The area was quickly cordoned off before it claimed any more victims.
00:24:40But for a bruised and shaken Laura, her sinkhole nightmare was just beginning.
00:24:46What I was in was actually the sewage water.
00:24:49I'd swallowed loads of that.
00:24:51Went in my system and that's when I started feeling sick.
00:24:57Rushed to hospital, Laura was urgently treated for leptospirosis,
00:25:02an illness stemming from water that's been contaminated by rat urine.
00:25:08Leptospirosis basically eats you from the inside out.
00:25:12So it starts off, you can be completely fine, and because it's eating you from inside out,
00:25:17you don't notice it until you're practically dying.
00:25:22It was a race against time, not just for Laura, but also potentially for her unborn child.
00:25:31I found out I was actually pregnant with our second child.
00:25:36So I was very worried that there was going to be long-term health problems for not only me,
00:25:42but also the unborn child.
00:25:44As Laura's condition worsened, things did not look good.
00:25:49I'd been wheeled into this ward and looked around and was kind of like,
00:25:53oh, I know people come on this ward and die.
00:25:57I saw all these people who were on their deathbeds
00:26:02and I kind of panicked that it was going to be me next, which was very scary.
00:26:08After an anxious wait involving several days of treatment,
00:26:12Laura eventually began to recover.
00:26:18Months later, her new baby boy was safely born.
00:26:22Now, her family of four are all doing well.
00:26:28But there are some scars that have still not healed.
00:26:32I feel very lucky to be here.
00:26:34But in the long term, it's really badly mentally affected me.
00:26:40I spoke to my doctors and spoke to someone because of PTSD
00:26:47because I was really struggling day to day.
00:26:50And there's a lot of times where I've smelt sewage smell
00:26:55and people can just see me go completely white.
00:26:58My daughter's at the age now where she loves jumping in puddles.
00:27:01And there's been times where I've seen a puddle that she's gone to jump in
00:27:05and I've just grabbed her hand just in case the floor opens up underneath her.
00:27:10It will always be in the back of my mind.
00:27:15Laura's harrowing experience joins an ever-growing list of incidents
00:27:21as sinkholes leave their psychological mark across the globe.
00:27:32In the heart of Dazhou city, China, tragedy struck on October 7th, 2018.
00:27:39CCTV captured the moment the ground suddenly gave way under a busy footpath
00:27:46sending five people plunging down into a three meter wide sinkhole.
00:27:52It's absolutely terrifying.
00:27:55People wanting to go into town and suddenly something's gone wrong.
00:27:59You're fighting for your life because a hole has opened up underneath your feet.
00:28:06Rescue efforts were immediately launched with one person saved.
00:28:11But the unstable sinkhole continued to widen,
00:28:14nearly swallowing two firefighters as they desperately tried to reach those buried deep below.
00:28:20Two of the victims, believed to be newlyweds, were retrieved hours later
00:28:24and rushed to hospital where they tragically died upon arrival.
00:28:28A father and son were also swallowed up
00:28:31and by the time rescuers found them in a cavern ten meters down, it was already too late.
00:28:39The incident claimed four lives,
00:28:42a chilling reminder of the threat sinkholes pose in heavily populated cities.
00:28:55But another sinkhole mystery has recently emerged across an entire county.
00:29:01Known as the Garden of England,
00:29:04Kent could be sitting on hundreds or even thousands of ticking time bombs
00:29:09capable of shutting down motorways and swallowing victims whole.
00:29:14In 1967, in Finsbury, England,
00:29:17a sinkhole opened up and a lady and a child fell into the hole, which was 90 foot deep.
00:29:22Her body was never recovered.
00:29:25No warning whatsoever, no warning.
00:29:28You would have gone in with a collapse.
00:29:31You would have disappeared in the soil.
00:29:34You would not survive that.
00:29:37Where are these hidden treasures?
00:29:40What are they?
00:29:41Pete Burton is a member of the Kent Underground Research Group, or KERG,
00:29:46a volunteer force who map out dangerous sites like sinkholes in the area.
00:29:52It's important to survey them because sometimes they go underneath roads, into people's gardens.
00:29:58It's very important to know what's underground.
00:30:01It's important to know what's underground.
00:30:04It's important to know what's underground.
00:30:06It's important to know what's underground.
00:30:09I personally know of four that have opened in the last year.
00:30:13I personally know of four that have opened in the last year.
00:30:16And there's an awful lot of them out there that we don't really know about.
00:30:21For decades, KERG has regularly assessed one hole in a front garden near Faversham.
00:30:29Tucked away under a manhole cover,
00:30:31it's been cleared out and kept safe by the local Lees Court Estate.
00:30:37We need a certain amount of oxygen to be able to survive.
00:30:40We don't know how good the air quality is. It's not been open since last year.
00:30:45So we could have what we class as dirty air.
00:30:48If the alarm goes off, it will flash and we would hear the siren.
00:30:55Oxygen is 20.8, so the air's good.
00:31:01Analysing this subterranean site holds the key to the origin of Kent's sinkholes.
00:31:09Because down the nine-metre shaft lies a secret human man-made structure
00:31:14that's littered across the Kent countryside.
00:31:19And they're named Deanholes.
00:31:23An ancient mine built to extract chalk for the local community.
00:31:28Most sinkholes that have opened up in Kent in the recent past
00:31:33would have been from Deanholes.
00:31:36And it's because they were never fully backfilled.
00:31:39Sometimes in the past they would just chuck a few tree roots down there
00:31:43and they would block part of the shaft.
00:31:45And after a few hundred years, the tree roots will rot away
00:31:49and the thing will open up.
00:31:51They can open very suddenly.
00:31:54Anything can cause it. Some heavy rain, heavy tractors.
00:31:57You could be walking through a field and just the weight of a human body
00:32:01could cause them to open.
00:32:05But despite triggering deadly sinkholes at ground level,
00:32:09these massive underground structures may actually unlock
00:32:13mysteries buried in Britain's past.
00:32:16With large, carved chambers that could date back thousands of years.
00:32:23Romans mentioned the fact that we were digging holes.
00:32:25It may be that we were doing it well before the Romans ever came here.
00:32:30So we could have been doing it through the Neolithic.
00:32:33It's just extraordinary. It's not like anything else.
00:32:37For centuries, the true purpose of these structures remained a mystery.
00:32:42There's one theory that the Danes have come over to create these holes originally.
00:32:47In the 1800s, a lot of people thought they were where the Druids might have lived.
00:32:53But for Pete, the answer is still etched into the walls themselves.
00:32:59People in the past may have considered that this was an altar.
00:33:04It's the right sort of shape and size.
00:33:08But what we're standing on is a stepped workbench.
00:33:11The reason they've kept this bench here is so that it can reach the roof.
00:33:15It's just stepped so you can start at the roof with a narrow roof
00:33:18which is much more solid.
00:33:21There's no signs of any collapse in it.
00:33:24And then just cut back and push forward.
00:33:27We can see chalk marks here where they've been chopping down.
00:33:32It's part of a working method.
00:33:36The point of digging Dean holes rather than quarrying chalk
00:33:41is that in the old days, roads were in a dreadful state.
00:33:44It would be easier to dig a hole than try and bring some chalk
00:33:48from half a mile away from a quarry.
00:33:51Ancient chalk mines like this may be triggering sinkholes,
00:33:55but their white walls were once a valuable resource
00:33:59for the people living here in Kent,
00:34:02used to fertilise soil and make bricks and mortar for local homes.
00:34:06Today, thanks to the assessments made by the Kent Underground Research Group,
00:34:11the site is being preserved by the steward of Lee's Court Estate,
00:34:17American-born Countess Saunds.
00:34:20I have no frame of reference for anything on this scale
00:34:27with this kind of history, the cathedral-like quality of it.
00:34:34It actually makes, in its own way, makes me quite emotional.
00:34:38This suggests that for every new sinkhole in the county,
00:34:42there could be a beautiful human-made structure underneath,
00:34:46just waiting to be found.
00:34:49To bring it to life now is a way of seeing that history continue.
00:35:01But other places in the UK are dealing with a far more aggressive situation.
00:35:06Rippon is a historic city in North Yorkshire,
00:35:10known for its medieval buildings, Market Square,
00:35:14and a mysterious sinkhole epidemic that stretches back centuries.
00:35:20Rippon has been referred to as the sinkhole capital of the UK,
00:35:25and it certainly has more natural sinkholes than anywhere else in the UK.
00:35:29It's something people don't like to speak about.
00:35:33It's a bit like the spectre at the feast.
00:35:37In November 2016, 12 homes were evacuated in the north of Rippon.
00:35:43It started with one lady's back garden falling away
00:35:47into a hole of about 30 feet in depth,
00:35:50and it eventually spread to the north of Rippon.
00:35:54It's a bit like the Spectre at the Feast.
00:35:56It started with one lady's back garden falling away
00:36:00into a hole of about 30 feet in depth,
00:36:03and it eventually spread across 65 feet wide,
00:36:07which impacted neighbouring gardens.
00:36:10One particular resident had a very lucky escape.
00:36:14She managed to cling on to a post where her washing line was attached to
00:36:19and managed not to fall into the huge hole
00:36:22which happened almost instantaneously in her back garden.
00:36:28Rippon sinkholes have triggered at least 30 major ground collapses
00:36:34in 150 years, affecting countless properties.
00:36:38Empty plots where buildings once stood have become a common sight.
00:36:43But the biggest mystery is, why here?
00:36:48The widespread nature of Rippon's sinkhole problem
00:36:52is a direct consequence of the rock the city was largely built on,
00:36:57gypsum.
00:36:59If you thought limestone was a problematic rock
00:37:02in terms of the creation and evolution of sinkholes,
00:37:06gypsum is on a whole other level.
00:37:09Limestone dissolves on a timescale of thousands to maybe millions of years.
00:37:15Gypsum can dissolve on a scale of a matter of years to hundreds of years.
00:37:22It dissolves very quickly.
00:37:24Imagine a sugar cube on your tongue.
00:37:27As it dissolves, your saliva literally transports that liquid away.
00:37:31And this is what's happening to the gypsum deep underground.
00:37:35Due to this process, the caves expand rapidly,
00:37:39bringing the high-speed sinkholes to life.
00:37:42In some ways, what we're seeing in Rippon is sinkholes on steroids.
00:37:47With three rivers and a canal,
00:37:49there are a series of collision points for water and gypsum.
00:37:53And one man who's found himself at the sharp end of the problem
00:37:58is Matt Pritchard, who first moved to the city centre in 1996.
00:38:06I thought, this is great. I've got myself a flat.
00:38:10My family's grown up here.
00:38:12I've got a base in Rippon.
00:38:14This is good. Life is good.
00:38:18But in 2008, a series of cracks began to appear.
00:38:23As these grew over time, it became clear to Matt
00:38:27that a sinkhole was slowly tearing his home apart.
00:38:32It sort of looked a little bit like the building had twisted
00:38:36and the bricks had cracked and kind of moved apart from each other.
00:38:42One of the most worrying things about it, in the flat at that point,
00:38:47was becoming very obvious that the north-west corner was dipping.
00:38:53You could actually feel it.
00:38:55If you dropped a tennis ball somewhere,
00:38:57it would start to roll towards the north-west corner of the house.
00:39:01When I went to Matt's house, it was quite a terrifying experience
00:39:05because I stood in it and I could hear it creaking.
00:39:09And that's perhaps the most unnerving experience I've ever had as a journalist,
00:39:14to be inside a house that you think could fall down at any minute.
00:39:19After being embroiled in a battle with the insurers,
00:39:22a structural engineer eventually deemed the property unsafe to live in.
00:39:27When the structural engineer said,
00:39:29look, as far as I'm concerned, it could collapse.
00:39:31It could collapse right now.
00:39:33We just don't know.
00:39:35So we came to the conclusion that we had no choice.
00:39:38We had no choice but to demolish it.
00:39:45There should be a building there.
00:39:47There should be my home there.
00:39:50Now it's just a bunch of rubble and a hole in the ground.
00:39:57The insurance company refused to accept Matt's claim.
00:40:01And to make matters worse,
00:40:03he and his fellow apartment owners were forced to foot the £100,000 bill
00:40:08to demolish their own property.
00:40:09It took the house.
00:40:11It took my financial stability.
00:40:13It took a huge hole in my mental health.
00:40:15You know, I just, I feel, just the feelings well up inside me.
00:40:20I just, I've cried.
00:40:23I could almost cry again.
00:40:29In Ripon, a single sinkhole has forced the evacuation of Matt's family.
00:40:35In Ripon, a single sinkhole has forced the evacuation of 12 properties in one go.
00:40:42Incredibly, for some other parts of the world, this is just a drop in the ocean.
00:40:55The sleepy town of Bayou Corn, Louisiana,
00:40:59sits on top of a giant subterranean salt dome,
00:41:02a remnant of an ancient ocean long since dried up.
00:41:07For decades, this salt had been extracted by machines drilling deep into the ground
00:41:13and flushing the salt out with fresh water.
00:41:16However, on August 3rd, 2012, a cavern collapsed with dramatic consequences.
00:41:23Opening up, a huge sinkhole that sucked in whole trees and swathes of vegetation into a void.
00:41:33It was 2.5 acres across and growing.
00:41:40There are a number of houses around there.
00:41:43It's in a community.
00:41:45And obviously, when the hole got progressively larger,
00:41:48you were threatening the people living nearby.
00:41:52350 nearby Bayou Corn locals were evacuated
00:41:57as the sinkhole continued expanding to 37 acres in size,
00:42:02transforming the entire area into a toxic swamp that residents may never return to.
00:42:10We'll never feel safe there again.
00:42:12They can never say that it will be safe there again.
00:42:14They can never say that it will be safe there again.
00:42:17The sinkhole is still growing today.
00:42:19Eventually, it will stop, but no idea when.
00:42:23And really, very sad indeed.
00:42:37Sinkholes have opened up across our planet.
00:42:41From gaping chasms to tiny hidden depressions.
00:42:46You could lose your family, your car, your house, friends into a sinkhole,
00:42:52and no one really knows how dangerous they are until it's too late.
00:42:58Their sudden and lethal formation has plagued humanity for thousands of years.
00:43:04Whether it's limestone, gypsum, or even old mines,
00:43:08where there is a cavity deep underground, a sinkhole can appear at any time.
00:43:13These geological phenomena are always changing and shifting
00:43:20in ways that we're still researching and trying to get to grips with.
00:43:25But as we move beneath the surface
00:43:28and investigate these subterranean structures firsthand,
00:43:31we don't just find death and destruction.
00:43:34In fact, it's becoming clear there are many mysteries
00:43:39that sinkholes can actually help solve.
00:43:42They give us an insight into a subterranean world
00:43:46that is largely inaccessible to humans.
00:43:49Only when you start to either go into them, dive into them,
00:43:53understand what's under there,
00:43:55do you start to get an appreciation for how complex they are,
00:43:58that they were places where people not only lived but also conducted ritual,
00:44:03so many different things that aren't apparent from the surface.
00:44:06Through understanding this human connection to rock and to landscape
00:44:11is bringing sinkholes to life.
00:44:182024, the Peak District.
00:44:21Sitting in the centre of the UK,
00:44:24it's one of the world's most popular national parks.
00:44:28With over 13 million visitors a year.
00:44:32Underneath the rollicking green hills,
00:44:35cavities in the limestone rock make sinkholes a common occurrence.
00:44:40And below those depressions are thousands of caves.
00:44:45Hidden worlds just waiting to be explored
00:44:48by the Eldon Pothole Club, a local group of friends and cavers.
00:44:59Cave exploration takes you back to the old days of exploration.
00:45:03You can dig into the cave and no-one alive knows what's around that corner.
00:45:08It's epic.
00:45:10Our ambition is to try and find a new cave,
00:45:13but that's really hard in the Peak District.
00:45:15It's really hard in the UK or even, like, western civilisation world.
00:45:22But in April 2024, on a secluded hill,
00:45:25the team found a small, mysterious sinkhole.
00:45:29Tracking the path of the water flowing into the void,
00:45:33they realised it was travelling underground to springs
00:45:36around four kilometres downstream.
00:45:39Raising the question,
00:45:41had this sinkhole revealed an undiscovered labyrinth
00:45:45of interconnected caves?
00:45:47Sinkholes are the front doors.
00:45:50They're the entrance into this underworld of magical things
00:45:53to explore or fun trips to have with your friends, whatever.
00:45:57The sinkholes are your way into the caves.
00:46:00So if you can go to where the water sinks in a sinkhole up on the hill
00:46:05and you can see where it comes out at the resurgence,
00:46:09you know there's a cave passage between those two points.
00:46:14The team had located an entrance point
00:46:17halfway down the hill at a hole named Cossipot,
00:46:20allowing the opportunity to find the underground river
00:46:24and, with it, the extended cave network.
00:46:27Cossipot was a crazy thing to explore.
00:46:30We only spotted it because there's wind coming out of the ground.
00:46:35If there's wind coming out of something,
00:46:38it generally means there's a cave that goes a long way.
00:46:41So we started pulling out these rocks to see what was the cause of this wind
00:46:46and got into the top, like a 20-metre pitch down.
00:46:48into a completely new cave system,
00:46:51directly in line between the sinkhole and the spring.
00:46:55And it's just like, you know, we're off.
00:46:58Having secured the entrance, the team began their sinkhole exploration,
00:47:03but conditions were far from easy.
00:47:06This is definitely not for everyone.
00:47:09Most people's idea of fun is very different to what we do.
00:47:12You've got no phone signal, you've got no GPS,
00:47:15you've just got your friends, your mates,
00:47:18to help you out.
00:47:20You're a team and it puts an edge on what you do
00:47:24because the consequences of getting things wrong are serious.
00:47:28One piece of bad luck and you could be in deep trouble.
00:47:33In September 2023, emergency workers in Turkey
00:47:38rescued an experienced American caver from the Morkar sinkhole.
00:47:43The man had fallen seriously ill
00:47:45and spent 12 days trapped over 1,000 metres underground.
00:47:53Rob and his team know the potential risks
00:47:56when exploring these deep underground structures.
00:48:01There was a downward pile of boulders that we're going down the side of
00:48:06and we're putting scaffold in to try and hold these boulders back.
00:48:09So I slid down through this gap to try and see what the way on was
00:48:12and as I turned round, it was just boulders all around me
00:48:16and they didn't look like they were being held up by anything.
00:48:19That's looking straight up.
00:48:22This rock here is bad.
00:48:27Those rocks there, a lot of pressure holding that up.
00:48:32Rob had seconds to react.
00:48:35I really don't like this. I'm coming out.
00:48:39All these boulders all around me and they started to move.
00:48:42I was like, nope, got to get out straight away.
00:48:45This is not a good place to have rocks falling on you.
00:48:48Despite the odd setback, progress was good.
00:48:52But the problem with entering structures like sinkholes
00:48:55is that key access points underground,
00:48:58which were previously dry, can flood without warning.
00:49:02Next time we went, it was full of water.
00:49:04We had to either go for it and hold our breath and go through
00:49:08or we had to just cancel, cancel exploration.
00:49:11The sinkhole exploration was in trouble
00:49:14because now the best chance of reaching the subterranean river
00:49:19and with it, the extensive cave network
00:49:22was a free dive 80 metres below ground.
00:49:26I'd never free dived anything like that before,
00:49:29but I've got to go, I've got to try it.
00:49:31Hold my breath and feel my way through.
00:49:40Oh, that's cold.
00:49:42You slop into it and it's really cold.
00:49:44You can't turn round, it's too small, constricted to do anything
00:49:47to change your mind.
00:49:49You committed, 100% committed.
00:49:55It was a tight squeeze, but Rod made it through.
00:49:59As soon as you're through, you're just elation.
00:50:02You know, you feel great.
00:50:05After an anxious wait, Rod's colleague follows
00:50:10and the sinkhole exploration could move on to its final obstacle.
00:50:15But it wasn't pretty.
00:50:17Collaborating with a team of experts to survey the remaining route
00:50:21revealed a tight tunnel of mud extending 120 metres.
00:50:26You've got to move your body in the right ways.
00:50:29You've got to stay really cool
00:50:31or else you just get bigger and you get stuck.
00:50:34This is a weird one.
00:50:36It's like, this is almost as good as it gets
00:50:38and totally awful all at the same time.
00:50:41Like, you just switch into a different gear
00:50:43of not minding how muddy you are, not minding how cold you are.
00:50:46You've got that fever for exploration, but we're mad, maybe.
00:50:50Or just, you know, we were all the same.
00:50:52We just love that sort of thing.
00:50:53After a slow crawl through the mud-filled caverns,
00:50:59the team finally made it to a master cave.
00:51:03And with it, the river.
00:51:06Their sinkhole exploration had succeeded.
00:51:11And because of that, around two and a half kilometres
00:51:15had been mapped out for a brand new cave system
00:51:19that others can visit.
00:51:20It's one of the reasons we like doing it at home,
00:51:23is, you know, people, our friends can go and see it.
00:51:26Our mates are literally going to explore what we found.
00:51:29But there's so much more to do
00:51:31and there's so many other hills in the Peak District
00:51:34where the master cave hasn't been found yet.
00:51:36There's so much more to explore.
00:51:39Caving provides an opportunity
00:51:41to flip the sinkhole narrative on its head.
00:51:45Unlocking subterranean mysteries
00:51:47and turning a dark, muddy hole in the ground
00:51:50into something exhilarating.
00:51:54When I actually started caving, I was terrified.
00:51:58I hated caving.
00:52:00I hated it so much.
00:52:02There was this rush of anxiety,
00:52:05of feeling this fight or flight all the time
00:52:08when I was underground.
00:52:10It felt like when I started to come back over ground again,
00:52:13things weren't so scary.
00:52:15Because I'd been to some scary places underground,
00:52:19I had won over myself
00:52:21because I knew I could face any challenge.
00:52:24And what an amazing feeling that is.
00:52:34Exploring sinkholes can reveal new hidden worlds.
00:52:37But they are also helping us discover
00:52:39old mysteries from ancient human civilizations.
00:52:47From the Cenotes of Mexico,
00:52:49where the legendary Maya benefited from their fresh water,
00:52:53all the way to Florida, on mainland USA.
00:52:59Indigenous peoples view nature through a lens of oneness.
00:53:03They look at sinkholes with a sense of unity.
00:53:05Indigenous peoples view nature through a lens of oneness.
00:53:08They look at sinkholes, mountains, rivers,
00:53:11through a lens of animacy,
00:53:13where they are alive with a spirit.
00:53:17I think we can learn a lot about how to understand sinkholes today
00:53:21from thinking about the way that indigenous people used them in the past.
00:53:26The reason sinkholes are a tragedy today
00:53:29is often because we've built in places that are geologically unstable.
00:53:32Ancient people worked more with what they were already given from the environment
00:53:36rather than trying to manage it so much as we are today.
00:53:41Tracy Ardren is a professor of anthropology at the University of Miami,
00:53:46who specializes in prehistoric cultures.
00:53:49She spent the last 23 years studying at an ancient sinkhole
00:53:54called Little Salt Spring,
00:53:56which was first donated to the University of Miami in 1982.
00:54:01At the end of the last ice age, when the sea levels rose in Florida,
00:54:05a lot of the state was submerged,
00:54:08and Little Salt Spring turned into the type of sinkhole that we see today,
00:54:11which is water-filled to the ground surface.
00:54:14In the past, during the ice age, the water levels were much lower.
00:54:18Florida was much drier, there were fewer water sources,
00:54:22and so a sinkhole like this that was filled with fresh water was a very important resource.
00:54:27While many people understandably see sinkholes as a threat in the modern day,
00:54:32new research is making it clear that these ancient sinkholes were places of congregation.
00:54:39This is an hourglass-shaped sinkhole,
00:54:42which in the narrow part of the hourglass has a shelf
00:54:46where there's been evidence of human occupation or use.
00:54:49That would have been the ground surface in the last ice age,
00:54:53when the water level was much lower.
00:54:54This water that bubbles up from the limestone has a very low oxygen content
00:55:00and a very particular combination of chemicals that help organic things preserve,
00:55:05which generally don't preserve in Florida because we have very acidic soils, tropical soils,
00:55:10but in this particular context have survived.
00:55:13The unique preservative qualities of freshwater sinkholes
00:55:17provide a fascinating snapshot of prehistoric life.
00:55:20Dr Andy Hemmings is an archaeologist who specializes in underwater exploration
00:55:26and regularly dives into Florida's sinkholes.
00:55:29As near as I can tell, I'm the only living archaeologist
00:55:33actually related to the fictional Indiana Jones.
00:55:38Sean Connery, either his mother or grandmother
00:55:42would have been a sister to my great-grandmother.
00:55:46There's a critical difference between Indiana Jones and me.
00:55:48I do my own stunts, and that's why I have 85 stitches on my face.
00:55:55Today, Andy is heading to the Wasilla River,
00:55:59a tributary of the larger Orsilla River.
00:56:02His diving spot is a group of sinkholes
00:56:05hidden beneath the surface of the Wasilla waters, known as the Blue Springs.
00:56:12We have two divers today. We're going to go downstream
00:56:15into a fairly clear area with a nice deep hole.
00:56:19We're just sort of speculating right now, or prospecting in a way,
00:56:23just taking a look at what we think might be there
00:56:26and if it's worth trying to pursue in terms of finding more out.
00:56:30Permission to come aboard, sir?
00:56:3315,000 years ago, the sinkhole Andy is exploring
00:56:37would have been surrounded by dry land and over 300 kilometres from the coast.
00:56:41But as the water levels rose, the Wasilla and Orsilla Rivers
00:56:46began connecting various sinkholes
00:56:49that had once stood isolated from one another.
00:56:53He's still small enough he can cuddle.
00:56:56Diving alone in gator-infested water can be extremely dangerous.
00:57:01Roll it in.
00:57:03So Andy is joined by colleague Tom Haran.
00:57:12The Wasilla is a relatively low-energy or slow-moving river,
00:57:17so sediment on the riverbed tends to remain undisturbed
00:57:21rather than being washed away.
00:57:24When this sediment is disturbed, it disperses into the water,
00:57:29making navigation almost impossible.
00:57:32But it's actually the slow-moving nature of this river
00:57:36that lets the water flow through it.
00:57:38It's actually the slow-moving nature of this river
00:57:41that means ancient fossils stay put here,
00:57:44frozen in time, until they are discovered.
00:57:49What have you got?
00:57:51Landed right on the edge of the margin.
00:57:53I'm standing on limestone right now
00:57:55and started picking up flakestone artefacts.
00:57:57No!
00:57:59That one's definitely a human-made artefact.
00:58:02Andy discovers Shards of Chert,
00:58:04a hard sedimentary rock prized by a prehistoric man
00:58:08for its ability to be flaked into sharp tools.
00:58:11These flakestone artefacts show that humans
00:58:15once inhabited the area around the sinkhole,
00:58:17suggesting potential for further discoveries.
00:58:21Greatly encouraged about the possibilities here.
00:58:24I'm sliding around right now on my feet.
00:58:26We're both standing here feeling with our feet while we're talking
00:58:29because we're cold and we're going to get out,
00:58:31but we still want to know what's here.
00:58:33These Floridian waterways are just beginning to reveal their secrets.
00:58:38Exploring an Orsillo River sinkhole,
00:58:41researchers from Florida State University
00:58:44found stone tools alongside mastodon bones
00:58:47that appear to date back 14,500 years.
00:58:53If true, it would be the oldest known site of human life
00:58:58in the southeastern USA,
00:58:59meaning that ancient people could have spread throughout the Americas
00:59:031,500 years earlier than previously thought.
00:59:08Elsewhere, diving into sinkholes
00:59:11is taking us even further back in time
00:59:14to the hidden history of life itself.
00:59:17Two miles off the coast of Michigan in the US,
00:59:20and over 20 metres underwater,
00:59:22the Middle Island sinkhole has become a rich resource
00:59:26for scientific study.
00:59:27Because the water at this spot is rich in sulphur and low in oxygen.
00:59:32The bacteria that thrives here is a great proxy
00:59:35for the early microbial life that first formed on Earth billions of years ago.
00:59:42But lately, some of the most striking historic mysteries
00:59:46have been uncovered by sinkholes on dry land.
00:59:58In Rome, Italy, at the height of the COVID-19 pandemic,
01:00:03a chasm burst into life on the streets of the Eternal City.
01:00:10It was 10 square feet wide and nine square feet deep,
01:00:14right next to the Pantheon in Piazza della Rotonda,
01:00:17which is usually one of the busiest parts of Rome.
01:00:20Fortunately, it occurred during the pandemic
01:00:23because at any other time,
01:00:24something like that could have proved absolutely disastrous.
01:00:28Instead, this sinkhole led to the unlikely discovery
01:00:32of a hidden artefact from the days of ancient Rome.
01:00:39Historian Alexander Mariotti has been exploring
01:00:43this unlikely connection between sinkholes and the past for over a decade.
01:00:48They discovered that the sinkhole was in fact a glimpse
01:00:51into the pavement of the Pantheon.
01:00:54We're talking about travertine slabs that date between 25 to 27 BC.
01:01:00This is the original paving that was built by Marcus Agrippa,
01:01:03one of Rome's great generals.
01:01:05The stones date back over 2,000 years,
01:01:09and it could be just the tip of a very impressive iceberg.
01:01:14The truth is that when you come to Rome, you find out
01:01:17only 20% of the ancient city is actually visible.
01:01:20The other 80% is underneath the very squares, piazzas and fountains
01:01:24that you so enjoy walking around.
01:01:26And then when these sinkholes appeared,
01:01:28they're almost like a glimpse into an old friend,
01:01:31into another realm, another dimension.
01:01:35That hidden history has been revealing itself all over the city.
01:01:40With as many as 170 sinkholes reported in a year,
01:01:44Rome has now been branded the sinkhole capital of Europe.
01:01:49The question might be, why do these sinkholes keep appearing in Rome?
01:01:52And there's a very simple answer.
01:01:54Rome is a city of layers.
01:01:56And in fact, it's not a singular city.
01:01:58It is multiple cities, one built right on top of the other.
01:02:02Many of the lower layers are made up of old tunnels and aqueducts,
01:02:06creating gaps that are vulnerable to pressure from the new infrastructure above.
01:02:12The top layer is the heaviest layer,
01:02:15and slowly but surely, all the modernisation of the city
01:02:18is leading the city underneath to crumble
01:02:20and reveal itself through these sinkholes.
01:02:24What else could these voids reveal?
01:02:28For Alexander, Rome's most important sinkhole opened up almost a century ago,
01:02:35because it revealed a site that's connected to a truly seismic event in human history.
01:02:42When they went down further to inspect,
01:02:44what they discovered was nothing less than the 55 BC stone theatre of Pompeii.
01:02:51This is a structure that is tied to one of the greatest historical moments of Roman history,
01:02:56of Western civilisation, the assassination of Julius Caesar.
01:03:07Caesar was stabbed 23 times in the very same complex that this structure once belonged to.
01:03:15A significant piece of history, first found thanks to a tiny sinkhole.
01:03:20And Alexander has gained special entry to the site,
01:03:24which remains hidden from the public today.
01:03:27Access to it can only be done through the back of a shop and a broom cupboard of all places.
01:03:32And when you open this small door, all of a sudden,
01:03:35you get to walk back almost 2,800 years in time
01:03:38into a building that most people will tell you doesn't actually exist.
01:03:42It really gives you goosebumps.
01:03:44With the sinkhole now covered up,
01:03:47these ancient walls of the Pompeii theatre from 55 BC
01:03:52secretly sit below the busy streets of Italy's capital city.
01:03:58It's hard to believe that there's people walking up and down,
01:04:01unbeknownst to them that this gigantic piece of history is right beneath their feet.
01:04:05These walls are built out of opus reticulum.
01:04:08It's a crisscross style of building built out of volcanic ash tufa brick.
01:04:12But you see the problem with Rome.
01:04:15Here, very visibly, we have the layers.
01:04:18And this wall isn't very well built at all.
01:04:20It wasn't meant to withstand the centuries that it has.
01:04:23It's just bits of rock, bits of leftover marble, and a little bit of mortar.
01:04:28But it's holding up something that's built 1,600 years later.
01:04:32But you can see what happens.
01:04:34Traffic, trains, pedestrians.
01:04:36That vibrations, eventually something gets loose,
01:04:38and if something was to fall out, it would collapse.
01:04:41That's where you're getting your sinkholes from.
01:04:44This gateway to the past suggests
01:04:47that there may be another unexpected silver lining to sinkholes,
01:04:51providing an unprecedented opportunity for historians across the world.
01:04:58I know I might get in trouble for saying this,
01:05:01because sinkholes generally are a problem.
01:05:04But in this case, I have to say that I am eternally grateful for this sinkhole,
01:05:06because without it, we would never have had the discovery of a lifetime.
01:05:15Ever since man first invented the shovel,
01:05:18we have been exploring the ground beneath our feet,
01:05:21and sinkholes are no exception,
01:05:24with many of them repurposed as tourist destinations.
01:05:33In the late 19th century,
01:05:34a large cavity in South Australia
01:05:37was converted by a local farmer named James Umphiston.
01:05:42His work transformed it into a paradise called the Sunken Garden,
01:05:48once a limestone cave that formed a sinkhole when its chamber roof collapsed.
01:05:54It's now a public park that year-round plays host to sightseers and local wildlife.
01:06:01It looks so iconic, so amazing,
01:06:04but you can also get other trips that are a little more adventurous.
01:06:12In the vast Karakum Desert in Turkmenistan,
01:06:15some visitors have been drawn to one of the most mysterious
01:06:19and awe-inspiring sinkholes in the world.
01:06:22Known as the Gates of Hell,
01:06:25this flaming phenomenon has been spitting fire for over 50 years.
01:06:28Reaching reported temperatures of up to 1,000 degrees Celsius.
01:06:35It's easy to see why people often associate these spaces
01:06:40with being the entrance to hell itself.
01:06:44But the question for many tourists is, how did this happen?
01:06:49The story goes that in 1971,
01:06:52Soviet scientists were searching for oil in the desert.
01:06:55When they came across a large natural gas field,
01:06:58the ground beneath their heavy drilling rig collapsed into a huge pit.
01:07:03And in order to prevent the dangerous methane
01:07:06from being released into the atmosphere,
01:07:09the decision was made to set the gas on fire and burn it off.
01:07:14Something they thought would take around two weeks.
01:07:17Half a century later, the sinkhole is still ablaze,
01:07:21scorching anything that comes near it.
01:07:23And showing no signs of slowing down.
01:07:33But the most mysterious sinkholes for tourists to explore are in China.
01:07:38Home to over a billion people,
01:07:41it's regularly hitting the headlines
01:07:44for deep chasms appearing in built-up cities.
01:07:48However, out in the mountains,
01:07:50is a whole different world.
01:07:53Because the sinkholes up there are big.
01:07:56Really big.
01:07:58China has got the biggest and the best.
01:08:01There are probably more sinkholes in China
01:08:04than the rest of the world put together.
01:08:07You've got giant caves, giant sinkholes, giant collapses.
01:08:11It's spectacular.
01:08:13When a cave collapsed in the municipality of Chongqing,
01:08:16it created Xiaozhai Tiankeng,
01:08:19also known as the Heavenly Pit.
01:08:22At over 640 metres deep,
01:08:25this site is thought to be the world's deepest sinkhole.
01:08:29And it's helped to create an unexpected tourism boom in this region.
01:08:34Some of these things get millions,
01:08:37literally millions of visitors a year
01:08:40because they are mind-bogglingly spectacular.
01:08:43There are now 30 or 40 of them, I think,
01:08:46which have been found in this one region in China.
01:08:52Online content creators have flocked to these giant sinkholes
01:08:57across south-western China.
01:09:05Finding in their interiors swathes of lush vegetation
01:09:09that's flourishing in peaceful,
01:09:11that's flourishing in peaceful isolation,
01:09:14unlocking a world that was previously unknown to us.
01:09:33Researchers have speculated that some of these primitive forests
01:09:38could be home to plant and animal species
01:09:41that we didn't even know existed.
01:09:44It is its own ecosystem because it is isolated from everything else
01:09:49and therefore you get different things in it.
01:09:51Others have hosted animals and even humans.
01:10:11There are two theories about this wood.
01:10:14One is that it supports the mountain and prevents it from collapsing.
01:10:18The other is that there are elderly people living here
01:10:21and if you plant a piece of wood under the mountain,
01:10:24their back won't hurt and they will recover.
01:10:27Isn't that amazing?
01:10:32But how were these large-scale, spectacular sinkholes formed?
01:10:37China is special.
01:10:40It has 3 million square kilometres of limestone
01:10:44and a lot of it has caves.
01:10:47There's a passage going underneath
01:10:50and it's simply collapsed progressively up to the surface
01:10:54and as it collapses, the river washes it away.
01:10:57And that's how all these big ones are formed.
01:11:00You need a special geological situation
01:11:04where you've got soluble limestone which will dissolve
01:11:11but will also be strong enough to stay up and form your cavity.
01:11:16With so much soluble rock and a network of river caves below,
01:11:22it seems that China's mega sinkholes will remain a tourist attraction
01:11:27and stunning eco-lodge for some time.
01:11:35China's mega sinkholes
01:11:41Wild sinkholes have helped provide ground-breaking answers to several mysteries.
01:11:47For many, they remain a destructive force.
01:11:50New studies have revealed that for every 0.1 degree Celsius rise in global temperatures,
01:11:56the number of sinkholes will increase by up to 3%,
01:12:00which brings up arguably the biggest mystery of all.
01:12:04Can exploring their depths teach us how to live with them?
01:12:11A clue may come from investigating a series of sinkholes
01:12:15located deep underwater, known as blue holes.
01:12:20These previously unexplored realms have only recently begun to reveal their secrets.
01:12:28The blue holes that we're looking at were really mostly found by old fishermen in the area.
01:12:34There were reports of congregations of fish in certain areas.
01:12:38There were also reports of some areas even almost like bubbling up out of the water,
01:12:42which would be like a spring bubbling up to the surface.
01:12:46Dr. Emily Hall is a senior scientist at Mote Marine Laboratory,
01:12:52a marine research organization based in Sarasota, Florida.
01:12:57A blue hole is an old spring or sinkhole that we find anywhere up to 50, 60 miles offshore.
01:13:04They were old springs and sinkholes that were formed actually when that part of the land,
01:13:08especially in the state of Florida, was above the sea level.
01:13:11And as sea levels rose, these springs and sinkholes stayed.
01:13:15They kept their shape and their formation offshore.
01:13:18So now when you dive something like 100 feet down below the surface of the water,
01:13:23you'll find all of a sudden this big hole open up. That's what we call blue holes.
01:13:27The blue hole where Emily has conducted much of her research is called the green banana.
01:13:32It's a silly name for a blue hole.
01:13:35And I should mention that a lot of these blue holes were named by fishermen.
01:13:39I believe a green banana peel was floating by when the fishermen saw it,
01:13:44and he just named it green banana after it.
01:13:46The first explorations of the green banana revealed sea life,
01:13:50not just living with this underwater sinkhole, but thriving.
01:13:55It is one of the most amazing things in the world.
01:13:59You're going down the diver down line, and it just keeps going and going and going.
01:14:04And finally, you're in this blue water, open water,
01:14:07and all of a sudden this black, dark hole opens up.
01:14:10Biological activity all around you. The fish are circling you.
01:14:14They're looking at you. They're curious. They're not swimming away scared.
01:14:17These species, I think, are coming to these areas because it's a food source.
01:14:21Think about in a desert when you have an oasis out there
01:14:24of a little bit of fresh water and some vegetation growing.
01:14:28It's similar, but in the bottom of the Gulf of Mexico.
01:14:33The underwater sinkhole provides an all-you-can-eat buffet for local marine life.
01:14:40But could they also be harboring some of the ocean's most destructive organisms?
01:14:46One recent theory sheds new light on a phenomenon called red tide,
01:14:51a harmful algal bloom that may be connected to these underwater sinkholes.
01:14:57Our red tide in Florida is driven by blooms of Karenia brevis.
01:15:01It's a naturally occurring organism, but when it's in bloom,
01:15:05it produces a lot of toxins that are harmful to humans, harmful to other organisms.
01:15:09It can wreak havoc economically on the coastline of Florida.
01:15:13When blooms are really bad, we'll see a lot of dead fish, for example, along the beaches.
01:15:20This fish was killed by something called a red tide.
01:15:22That's a tiny organism that comes in in huge concentrations and suffocates sea life.
01:15:27We don't want anybody out here today. People come here to be on the beaches,
01:15:31and they don't want to be coming down here to be exposed to red tide.
01:15:35I can't describe this, man. It's just, like, unbelievable.
01:15:38Yeah, it's like, it makes you throw up.
01:15:42The cleanup goes on, and no one here is even guessing when the red tide will go away.
01:15:47The outbreaks have been known to kill 100 tons of fish in a single day,
01:15:53and it may even cause illness in people.
01:15:57If scientists are able to pinpoint the connection between red tide and blue holes,
01:16:03there will be one step closer to safeguarding our ecosystems.
01:16:09We have found, through opportunistic sampling, the presence of some of the Karenia species
01:16:14that forms red tide blooms along the coast of Florida.
01:16:18This was brand-new information for us to see Karenia cells hanging around some of these holes.
01:16:24It might provide more information for management of red tide
01:16:28or for understanding how red tide blooms are formed.
01:16:31We're just scratching the surface, and we're starting to ask more and more questions.
01:16:35You know, the more we're there, the more we find.
01:16:38Blue holes could reveal a fragile coexistence between living organisms
01:16:42and sinkholes.
01:16:44But these chasms are now starting to form in all sorts of unexpected and terrifying ways.
01:16:55Indiana, USA, July 2013.
01:16:59Six-year-old Nathan Weissner is on a group trip visiting Mount Baldy,
01:17:04a 38-meter-tall sand dune that sits on the southern shore of Lake Michigan.
01:17:11As a small child innocently played in the sand, the ground beneath him suddenly opened.
01:17:18The six-year-old boy was literally swallowed up by a sand dune
01:17:23when he fell into a sinkhole that was about three meters deep.
01:17:28Nathan was buried alive.
01:17:29Friends and family desperately called emergency services, but they faced a race against time.
01:17:36911.
01:17:38Yes, I'm at the Mount Baldy beach.
01:17:42And my friend's son, he got stuck in a sand dune,
01:17:47and he's, like, under the sand, and they can't get him out.
01:17:52It's terrifying to even think about.
01:17:55It's terrifying to even think about a situation,
01:17:59being on a beach, such an idyllic place, such calm and serenity,
01:18:04when suddenly everything flips on its head, and you're in danger.
01:18:09Okay, can anybody see him, or is he completely covered by sand?
01:18:14Yes, my husband and his dad are trying to dig him out.
01:18:18For over three hours, six-year-old Nathan remained trapped in the sand.
01:18:22For over three hours, six-year-old Nathan remained trapped.
01:18:25And despite the efforts of everyone around, some feared the worst.
01:18:31As a parent myself, I can't even imagine the horror his parents must have felt
01:18:37when they were desperately trying to search for him,
01:18:39when all the time he was at the bottom of this sinkhole, in the middle of this sand dune.
01:18:45Eventually, rescue workers successfully found Nathan,
01:18:48unconscious, but still breathing, thanks to a tiny air pocket on the ground.
01:18:56He was rushed to hospital, and made a full recovery.
01:19:01Fortunately, after many hours, he was pulled out alive,
01:19:05but the question remained, how did he end up there?
01:19:08With no limestone, or any other soft bedrock in sight, this was no ordinary sinkhole.
01:19:15But investigations beneath the surface found a surprising origin.
01:19:20Small tubes, which were remnants of rotted oak trees.
01:19:25Mount Baldy formed about four and a half thousand years ago,
01:19:29and is gradually migrating inland.
01:19:32And as it does so, it's beginning to swallow up a forest of trees.
01:19:37Usually, the trees would just rot away to nothing.
01:19:40But at Mount Baldy, it appears that a fungus, in the decaying process,
01:19:45had actually preserved some of the trees, outer walls, creating a unique kind of sinkhole.
01:19:53As the fungi began to decompose the organic matter of the wood,
01:19:58there was a chemical reaction at that interface between the wood and the sand,
01:20:02and it created a cementing process, whereby a cavity would be formed right in the middle of the sand dune.
01:20:10And this poor, unsuspecting child that was walking across the surface of the sand dune would fall into that cavity.
01:20:18With an unknown number of ancient trees hidden under the sand, the dunes were close to the public.
01:20:26It's just one of the many sinkholes that have been opening up suddenly, and without warning on dry land.
01:20:40In 1988, Norwich in the UK came face to face with a monster sinkhole that hit the most unexpected of victims.
01:20:50It was like any other normal day in Norwich.
01:20:54People getting on the bus, wanting to go into town, only today is a very different day,
01:21:00because it's the 3rd of March, 1988, and you're on the number 26 bus.
01:21:05This passenger route, up Earlham Road, was abruptly turned on its head.
01:21:11An ancient chalk mine collapse triggered a chasm 8 metres deep that swallowed up the double-decker bus.
01:21:19I would be terrified. You can't predict what's going to happen. Nobody really can.
01:21:28The driver ordered everyone on board to evacuate.
01:21:31But looking below the surface, the incident had exposed a gas main.
01:21:36Imagine being trapped in a tin can that's gone into a sinkhole, and suddenly you smell gas.
01:21:45What are you thinking? The bus might explode.
01:21:49We need to get out of here, and we need to get out fast.
01:21:53Fortunately, everyone on board got out safely.
01:21:57But the incident is a stark reminder of the threat sinkholes pose to our daily lives, even today.
01:22:05On June 26th, 2024, a sinkhole dramatically opened up on a local sports field in Alton, Illinois.
01:22:14Reports state that the field sits above a limestone mine, which created a hole through the ground.
01:22:20It sits above a limestone mine, which created a hole 30 metres wide and 9 metres deep.
01:22:27On this occasion, no one was hurt.
01:22:30But in the US alone, the damage from sinkholes is thought to cost at least $300 million a year.
01:22:39But while living with this enemy might seem like a dire situation,
01:22:44exploring the ground beneath sinkholes has given us the ability to fight back.
01:22:51GeoInvestigate is a company which specialises in geological surveying,
01:22:57using cutting-edge techniques to uncover any potential hazards lying beneath the ground.
01:23:03Today, they are on the outskirts of Ripon, known as the sinkhole capital of the UK.
01:23:11Most experts will tell you sinkhole activity in Ripon is unpredictable.
01:23:16It's going to happen, it's just a question of where and when.
01:23:19Company founder, Ross Nicholson, is surveying land that has been earmarked for a new Kebel housing development.
01:23:26What we have across there is a micro-drill. They're high-speed, safe, sinkhole-probing machines.
01:23:33They can drill three holes to 50 metres in a day.
01:23:37And in this business, looking for sinkholes, it's vital that you have as many boreholes as you can have.
01:23:43So by observing how the machine behaves and feeling how the machine behaves,
01:23:48the driller can get a good indication of the ground conditions they're going through.
01:23:52So on this site, so far, with the two holes we're drilling today,
01:23:57that will be 40 holes we've drilled here to 50 metres,
01:24:01looking for caves and caverns that could possibly collapse.
01:24:06As the drill plunges into the ground, it uses water to flush out the borehole.
01:24:12The colour of the water that spurts out indicates the type of material being drilled through.
01:24:18Brown through the soil, grey through limestone, and red through mudstone.
01:24:24Thankfully, there's been no cause for alarm on this site.
01:24:28But drilling boreholes is just one of the techniques used to interrogate the land.
01:24:33This is a magnetic system, so there's a number of sensors on here,
01:24:37and they pick up changes in the magnetic properties of the soils.
01:24:39All soils have a certain amount of iron in them. Tiny amounts, but all soils have it.
01:24:45When a soil is exposed to the air, the iron in the soil becomes oxidised,
01:24:49and basically it just becomes more magnetic.
01:24:51So if we've had a sinkhole that's appeared and created a hole,
01:24:55it then gets filled in over time with the soil.
01:24:57The soil that's filling it in is more magnetic than the surrounding soil,
01:25:01so it has a stronger magnetic response.
01:25:03The magnetic scanner can cover acres of land in the time it takes to drill one borehole,
01:25:09and as such provides an invaluable starting point for sinkhole detection.
01:25:14So this is the magnetic data plot.
01:25:16So on this site, all we can see is some very faint lines going in that direction,
01:25:20and that's evidence of the old medieval agriculture on this site.
01:25:23Certainly nothing in the data there that's telling us there's been any sinkholes that appeared in the past,
01:25:28or anything that's likely to turn into a sinkhole.
01:25:30The scanner, accompanied by drone imagery, picks up evidence of ridge and furrow farming,
01:25:37a medieval practice to help drainage.
01:25:41Reassuringly, there is no evidence of sinkholes,
01:25:44but the scanner's reach is limited to two metres below the surface.
01:25:48A more in-depth subterranean examination is achieved using a technique called window sampling.
01:25:54Taking soil samples around five metres below the surface.
01:25:58What we have in the tube, you can see the cord that's laid out.
01:26:02This is the topsoil here, yep, with grass.
01:26:06We can see a little bit of stone.
01:26:09So this material is typical of undisturbed boulder clay.
01:26:12It's strong, it's hard, and it's fairly consistent in its appearance.
01:26:18If there was evidence of disturbance,
01:26:20caused by sinkholes, we might expect this material to contain sands and gravels,
01:26:24loose materials, to be mixed up,
01:26:28and also it may contain organic material like peat.
01:26:32The combined techniques indicate that there has been no significant ground movement for hundreds of years,
01:26:38and therefore Ross and his team are satisfied that construction on this site can begin
01:26:44with low risk of sinking.
01:26:47With new investigations taking the fight to sinkholes every day,
01:26:51technology is allowing us to live with these unpredictable threats.
01:26:57For thousands of years, sinkholes have puzzled humanity.
01:27:02They've triggered death and destruction across the globe.
01:27:06And now we're faced with a new challenge.
01:27:09For thousands of years, sinkholes have puzzled humanity.
01:27:13They've triggered death and destruction across the globe.
01:27:17But exploring them has also led to groundbreaking discoveries,
01:27:22both in ancient history and modern science.
01:27:26And with more sinkholes continuing to open up beneath our feet,
01:27:31offering new access points to hidden worlds,
01:27:34the truth about deciphering the mysteries of sinkholes is that we're just getting started.
01:28:04What should we throw down?