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Cave Weather


Cave Weather
Cut off from the Sun, rain and wind that we experience on the surface, you might assume meteorological conditions in caves never change. However, the reality is that their climates do vary signifi cantly – not only from location to location, but within individual caves over time. Indeed, some examples, like the Er Wang Dong cave system in Chongqing Province, China (main picture), even host their own weather.

Ultimately this is because very few caves are 100 per cent cut off from their surroundings. In the case of Er Wang Dong, it all comes down to an imbalance in the local topology. There are several tunnels around the cave system’s perimeter where wind can blow in. Once trapped underground air from outside gains moisture, pooling into huge chambers like Cloud Ladder Hall – the second-biggest natural cavern in the world with a volume of 6 million cubic metres (211.9 million cubic feet).
Once in an open chamber this humid air rises. While there are numerous entrances into this subterranean complex, the exits are few and far between. In Cloud Ladder Hall’s case, it’s a hole in the roof some 250 metres (820 feet) above the floor, leading to a bottleneck effect. As the damp air hits a cooler band near the exit, tiny water droplets condense out to create wispy mist and fog. In the other chambers plants and underground waterways can also contribute to underground weather.
Even caves without any direct contact with the outside world can still experience climatic variations, as they are subject to fluctuations in atmospheric pressure and geothermal activity, where the heat from Earth’s core emanates through the rocky floor. However, in such caves, changes are more evenly distributed so take place over longer time frames.

Cave Weather