Caves are often thought of as little more than empty holes in the ground, but this is only half right; they’re holes with things in them. Far from being just a hollow space, caves are full of curiosities – unusual rock formations, prehistoric artwork and, frequently, hard-hatted men who need rescuing.
Here are five things you can find in a cave:
Crystals | Mexico
Scottish geologist Iain Stewart says that we know more about the outer edges of the solar system than we do about the Earth’s crust. This is nonsense, obviously, but the TV professor is right to think that there are some unexpected things hidden beneath our feet. Discovered by accident in the year 2000, Mexico’s Cueva de los Cristales (cave of the crystals) is one of our planet’s most amazing underground sights.
The miners who first discovered the cave must’ve been delighted – either they were going to be very rich or they were about to meet Superman. Sadly for the excited Mexicans, however, they were wrong on both counts. The crystals are made of gypsum and, despite being up to 12 metres long, are worthless compared to the lead and silver being mined nearby. If you want to see the cave of the crystals, get your protective suit and breathing apparatus out now – as soon as the mine closes, the cave will be flooded and the crystals will be lost again.
Lakes | Kefalonia
Most caves are wet – a bit damp, at least – but relatively few have a whole lake in them. Of those that do, one of the most impressive is the Melissani Cave on the Greek island of Kefalonia.
Visitors can take a boat trip around the two chambers of the Melissani Cave. In the first chamber part of the ceiling has collapsed, allowing the sun to reflect in the clear blue water. This illuminates the lake and fills the cave with light; a contrast to normal caves which (I’m sure they won’t mind me saying) are often a bit dingy. The second chamber remains covered and, although not as visually stunning, the shade beneath the rock is a blessing to any tourist foolish enough to have got extremely sunburnt on the very first day of his holiday.
Bats | Texas
People who claim that the UK is too populated might be interested to hear about Bracken Cave, Texas, where over 20 million bats cling to the walls. The bats migrate here each year, some from up to 1,000 miles away, spending March to October in the cave. Over 500 baby bats have been counted on a single square foot of cave ceiling – a similar level of overcrowding can only be found in the UK by going to IKEA on Boxing Day.
Every night, millions of Mexican free-tailed bats emerge from the single entrance to Bracken Cave. This swarm has been described as one of nature’s great spectacles, but for some people it probably sounds horrific. It’s easy to see why bats have such a poor reputation (it’s mostly to do with the fangs and claws and bloodsucking) but this is undeserved. The Bracken Cave bats eat up to 200 tons of flying insects per night, which is nice of them, and their dung makes an excellent fertilizer. Perhaps this explains why Texas has chosen the Mexican free-tailed as its official state bat – although why it felt the need to choose a state bat at all is a bit of a mystery.
Stalactites | Lebanon
Stalactites (with a C) hang from the ceiling, while stalagmites (with a G) stand on the ground. I don’t know if they considered this when they were naming them, but it certainly helps when trying to remember which is which. Stalactites are formed when water drips from the ceiling of a cave and leaves behind a small mineral deposit. Over time, these deposits grow and grow, until giant daggers of rock are left hanging directly above the head of any caver silly enough to walk under them.
The longest stalactite in the world can be found in Jeita Grotto, Lebanon. This massive rock-cicle measures 8.2 metres which, given an average rate of 0.13mm per year, must have taken absolutely ages to grow.
Paintings | Argentina
One sleepless night, I pulled open my bedroom curtains and looked out onto the deserted street below. As I stared into the darkness I realised that my breath was visible on the cold window and, in the middle of the breath patch, there was a child’s handprint. At first I thought this was utterly terrifying and that I was flat-sharing with a little ghost but, by morning, I had convinced myself that it was more likely to be the handprint of a previous resident. This gave me a sense of my place in the building’s history and, eventually, I began to find it reassuring – people had lived in my horrible flat long before me, and they hadn’t cleaned the windows either.
Cueva de las Manos, in Argentina, has handprints on the wall that are between 9,500 and 13,000 years old (far older than the one on my window). Rather than dipping a hand in mud then splodging it around the cave, which would’ve been one method, the images instead are stencilled outlines, made by placing one hand on the wall then blowing colour around it. Somehow this technique makes the pictures seem more three dimensional – it’s easy to visualise a caveman’s hand in the space left behind, pushed against the wall as he made one of these basic self-portraits.
Analysis of the hands suggests that they are mostly from teenage boys, possibly created as part of a coming of age ritual. There are also some outlines of the feet of American Ostriches, made using the same technique (presumably by people rather than the ostriches themselves). These aren’t the only type of painting in the cave; in common with other examples around the world, Cueva de las Manos also has drawings of animals and hunting scenes. Experts believe that these were not made just for decoration, but as messages for other people – the caveman equivalent of a shopping list pinned to the fridge.