Permafrost Underground: The Mystery of Ice Caves (11 photos + 1 video)

Deep in the mountains of China's Shanxi Province lies a phenomenal natural cryochamber. This is Ningwu Cave, China's largest underground ice cave.





This cavity extends 85 meters into the rock face, and its shape resembles a giant stone bowling pin. Another world reigns within: multilayered ice deposits adorn the walls and floor, and colossal ice stalactites hang in clusters from the ceiling vaults, interlocking with stalagmites that have grown to meet them.



Ningwu Ice Cave

Ningwu's main mystery is its resilience. At the height of the summer heat, when the surface air temperature reaches well over twenty degrees Celsius, the temperature remains below freezing, and the ice cover remains intact.





These underground kingdoms of eternal cold are scattered across the maps of various continents. They can be found in Europe, Asia, and North America. Many, as expected, are located in harsh northern latitudes—in Alaska, Iceland, or Siberia, where the climate itself favors the preservation of ice. But the most astonishing are those that exist in warmer regions, defying the laws of seasonality.



The secret to their longevity lies in their unique architecture, which turns the cave into a natural cold trap. The specific arrangement of the entrance holes and vertical channels acts as a valve. In winter, dense, frosty air moves freely downward, filling the cave and pushing out the lighter, warmer air.



With the arrival of summer, the situation changes: now the cold air mass trapped at the bottom of the stone chamber becomes heavier than the warm outside air and does not rise, while the warm air cannot descend to replace it.



The ice mass inside acts as a thermostat. Warm currents penetrating in the summer instantly lose their energy, melting the microscopic ice layer, preventing the cave's air from warming up. It works the other way too.



For such a cave to form, nature must maintain a balance. Heavy snowfalls are needed, which in winter will cover the slopes with a thick blanket. In spring and summer, it must be warm enough for the snow to melt actively, but not so warm that the air at the entrance becomes too warm. The meltwater must seep in and turn into ice, replenishing the reserves. Disrupting this cycle threatens the collapse of the fragile ecosystem.



Eisriesenwelt in Austria

Among all the ice caves on the planet, Austria's Eisriesenwelt stands out. This gigantic system, stretching over 40 kilometers in the Tennengebirge massif south of Salzburg, is considered the longest in the world.



Decora Cave in Iowa, USA

In the US state of Iowa, Decorah Cave is famous for its reverse life cycle. In the fall and winter, it is empty, and its rocky interior gradually cools. In the spring, meltwater penetrates the rock and, meeting the frozen walls, crystallizes, building up a layer of ice several centimeters thick by early summer. This ice often survives the August heat, while on the surface, the thermometer can rise above 35 degrees Celsius.



Coudersport Ice Mine is an ice cave located in Sovereign, Pennsylvania.

A similar paradox is demonstrated by the Coudersport Ice Mine in Pennsylvania. It is a man-made or natural sinkhole where ice stubbornly grows during the warm season and completely disappears with the arrival of frost.



Booming Ice Cave

A true acoustic marvel is the Booming Ice Cave in the Canadian Rockies (Alberta). Its main feature is the deafening, amplified echo generated by rocks falling to the bottom of the 140-meter-deep chasm. This hidden cavity was only discovered by science in the 21st century thanks to the analysis of satellite images.