Naturally occurring ice caves are dotted across Europe (Iceland is home to the beautiful ice cave of Vatnajokull) and a number of spectacular ice caves are found in Russia, Central Asia and North America. This incredible phenomena draws in gobs of tourists, with many wondering what keeps these natural freezers so cold?

While this may be a plausible explanation for some ice caves, scientists studying the Ningwu cave at the Chinese Academy of Geological Sciences beg to differ. Yaolin Shi points out that while geothermal heat does vary in places, these often influence surface temperatures too. Meaning that if it is colder underground because of a lack of geothermal heat, it will be colder at the surface.



Ningwu cave, however, acts differently. In this particular location, summer temperatures at the surface can reach 62°F even when the cave temperature hovers at around 32°F. Clearly, there is quite a discrepancy between the two.