From dangerous animals to toxic gases and unpredictable flood waters, the world’s caves demand our respect. Here are ten of the deadliest.
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Deadliest caves on the planet
Eagles Nest Sinkhole, USA
There’s a sign, just under the surface of the lake that leads into the system of underwater chambers and tunnels known as Eagles Nest Sinkhole. Cemented to the rock, it features the grim reaper, surrounded by the skeletons of human divers, with the words, “STOP, PREVENT YOUR DEATH! GO NO FARTHER.’
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From the surface, this pine-fringed lake in Florida’s Chassahowitzka Wildlife Management Area looks benign. Under the surface, however, it’s shaped like a sink, with a long rocky, drain that lead into a series of confusing, tight, silty passages stretching 100 metres down.
Even the most experienced cave divers struggle here, so much so, it has been called the Mount Everest of cave diving. At least 10 people have died here since 1981, so the sign doesn’t mince it’s words. It adds, “THERE’S NOTHING IN THIS CAVE WORTH DYING FOR! DO NOT GO BEYOND THIS POINT.”
Movile Cave, Romania
Before it was discovered 40 years ago, by engineers drilling an exploratory borehole, the Movile Cave had been sealed off from the outside world for 5 million years. Few, if any ‘above-ground’ organisms could survive here. Buried under an 18 metre-thick slab of clay and limestone, this sprawling system of tunnels and chambers has low levels of oxygen and elevated levels of carbon dioxide. The air is also heavy with hydrogen sulphide, methane and ammonia.
Collectively, these gases make it almost impossible for ‘regular’ life to survive. If a person was to enter the cave without specialist breathing equipment, they wouldn’t last long. Yet, the cave contains many weird and wonderful creatures, including worms, crustaceans and bacteria, which can live here because they have evolved the ability to survive in these extreme conditions.
Mossdale Caverns, UK
Mossdale Caverns in the Yorkshire Dales National Park, is one of the UK’s most dangerous and challenging cave systems. It contains over 6 miles of complex, flood-prone passages, that were first explored over 50 years ago. A return trip to the far end takes about eight to ten hours.
In 1967, six cavers lost their lives here, after water levels rose following a thunderstorm. It was the worst caving disaster in British history. The rescue mission, which involved over 300 people, was one of the biggest ever mounted in Britain.
When the bodies were found, the coroner determined it was too dangerous to retrieve them, and the entrance was sealed. Four years later, the bodies were moved to a different chamber inside the system, which lies above the flood level. They remain there to this day.
Devils Hole, USA
The Devils hole is a deep, geothermal water-filled cavern in the Ash Meadows National Wildlife Refuge in Nevada’s Death Valley National Park. It gets a mention on the list, because the branching caverns are hard for any diver to navigate and because the bottom of the hole, some 130 metres underground, is an unexplored abyss.
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The cavern also acts as a natural seismometer. Ripples in the tepid water trace the marks of earthquakes that happen thousands of miles away. The caves formed over half a million years ago, and many species live here, including beetles, snails and the totally unique Devils Hole pupfish.
This little fish, which lacks pelvic fins, is only found here. Males are bright metallic blue. Females are more yellow. The last population count recorded just 38 individuals, making this one of the most endangered species on the planet.
Rising Star Cave, South Africa
Not so much deadly, as full of the dead, the Rising Star Cave contains the fossil remains of an extinct type of human called Homo naledi. The sprawling network was explored in 2013 by a hand-picked group of ‘underground astronauts.’
They were chosen for their expertise in caving and palaeontology, and for their slender frames that could squeeze through the system’s pinch points. This included a passage called ‘Superman’s Crawl’ which is seven metres long and, in some parts less than 25 centimetres high. All six had to crawl through on their bellies, with one arm pressed tightly against the body and the other extending above the head – just like a flying Superman.
The move paid off. More than 1,200 fossils were recovered, representing at least a dozen individuals. Since then, more fossils have been found, and their deposition, at the ends of chambers, suggests that the individuals could have been deliberately placed there after their death. Homo naledi lived around 300,000 years ago, so if these ancient hominins did bury their dead, this would make the Rising Star Cave the oldest known human burial site.
Natural Trap Cave, USA
Picture the scene. The last Ice Age is drawing to a close, and on the edge of a plateau in Wyoming’s Bighorn Mountains, a dire wolf is closing in on its prey. Then all of a sudden, the apex predator is gone. It falls 26 metres through a hole in the ground, and lands at the bottom of a big, bell-shaped cave. There is no way out.
Scientists who have used ropes to carefully lower themselves down and study the cave, have since realised that this place was a literal death trap. The fossilised remains of many prehistoric species, including mammoths, short-faced bears, cheetahs, bison, horses and wolves, have been found here, making it an important paleontological site. Now, the entrance has been sealed with a metal grate, so nothing else can fall in, and scientists are still actively researching the cave’s contents.
Cave of Crystals, Mexico
The aptly named Cave of Crystals, in Chihuahua, Mexico, is buried around 300 metres underground and contains giant gypsum crystals up to 11 metres long. Some are big enough to walk on and are so impressive they earned the cave its alternative moniker, the ‘Sistine Chapel of crystals.’
The cave sits on a fault line above a chamber of magma. Millions of years ago, scorching magma forced mineral-rich ground water up through the rock. This created caverns in the limestone and formed deposits which then slowly began to cool and crystallise. Eventually, the temperature stabilised at around 58 degrees Celsius, creating the perfect conditions for the crystals to grow…but deadly conditions for people.
Whilst 58 degrees isn’t necessarily a dealbreaker, the high level of humidity is. It stands at 90%, which means the human body is unable to cool itself down by sweating. Without specialist equipment, any person in the cave would quickly overheat, so this is one place best viewed in a photograph.
Krubera and Veryovkina Caves, Georgia
Po-tay-toe. Po-tar-toe. Krubera. Veryovkina. Both of these caves, located in Georgia’s Gagra Mountain have vied for the title of ‘world’s deepest cave’. At 2,197 metres deep, the Krubera cave thought it had it in the bag, then in 2018, cavers exploring the Veryovkina Cave reached a terminal sump at a water table, 2,212 metres down.
It took them four days to get there, but when they made camp at 2,200 metres, their breakfast was interrupted by a powerful surge of floodwater. Robbie Shone, who photographed the expedition for National Geographic, told the magazine, “I just thought, ‘Oh my goodness. We have to leave right now. If we just hang around, we’re all going to die.’” The team managed to escape after a hair-raising climb through powerful torrents of water.
Now, Guinness World Records say that Veryovkina is the deepest cave, whilst Wikipedia says it’s Krubera. Po-tay-toe. Po-tar-toe. One thing’s for sure however, neither cave is to be messed with, and both are incredibly dangerous.
Cave of Dogs, Italy
If you are reading this list to your dog, stop now. For the Grotta del Cane near Naples, has not been kind to their species. The cave is located in an area of geothermal activity. Volcanic gases, such as carbon dioxide, seep up through the rocks and into the cave. Then, because carbon dioxide is heavier than normal air, it accumulates in a layer at the bottom. Any animal that breathes it in, starts to suffocate.
In Roman times, the cave was known to renowned author, Pliny the Elder, who described a location near Pozzuoli where animals died from poisonous fumes. In the seventeenth century, German polymath Athanasius Kircher performed an experiment where he tied a dog to a stick and held it in the cave until the animal passed out.
Moving towards the nineteenth century, the Cave of Dogs became a go-to destination for wealthy European tourists. Visitors paid to watch dogs walk into the low-lying cloud of gas and then be carried out by the guides who orchestrated the stunt. The unconscious canines were then thrown into nearby Lake Agnanno to try to revive them, but it didn’t always work. Many dogs died. So, hold yours close, ruffle their ears, and never tell them of this place.
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