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Searing hot, windy or entirely made of ice — caves have many different climates

Luray Caverns in Virginia is a constant, cool 58 degrees. (Karen Bleier/AFP/GettyImages)

The dog days of summer are upon us. It’s the time of year when we descend into our cool basements and laze. It’s too hot to even float around in your neighborhood pool. But there are other kinds of caves with similarly cool climates that, at the very least, might encourage you to get out of the house.

Everyone thinks that caves are chilly and damp, but there are actually many different types of cave climates. Some are windy, some can be boiling hot, and yet others are completely made of ice. Luray Caverns in Virginia — a two-hour drive west of Washington — is 167 feet below the surface and a constant, cool 58 degrees.

Wind Cave in South Dakota is known to “breathe,” unlike many cave climates that are static. Air moves from high pressure to low pressure, so when the barometric pressure outside the cave drops because of an approaching storm, air rushes outside of the cave to equalize itself. As the storm moves away and high pressure builds outside, the reverse happens and air rushes back into the cave. In extreme cases, wind speeds can hit 70 mph.

Perhaps one of the most bizarre cave climates on Earth is found in the Cueva de los Cristales (Cave of Crystals) in Mexico. In this deep cave 980 feet below the surface, air temperatures can hit 136 degrees and humidity can top 90 percent. The cave gets its name from the giant, science-fiction-like crystals of gypsum that form; one has been measured at 39 feet long, 12 feet in diameter and weighing an estimated 55 tons.

Cueva de los Cristales’s heat comes from a magma chamber below the cave. Because it’s so hot, spelunkers can spend only about 10 minutes in the cave. In 2006, Italian scientists were able to document portions of the cave by wearing refrigerated suits. But this cave will soon be inaccessible — the chambers will fill with water when the nearby underground gold and silver mine shuts off the water pumps that make the cave accessible.

While most caves develop underground in formations of limestone, others form in the belly of glaciers. Some of the largest cold, icy caves in the contiguous 48 states are found on the slopes of volcanic Mount Hood, Oregon’s highest mountain and home to 12 named glaciers and snowfields. Mount Hood’s caves form “from the melting caused by hot springs and fumaroles that are heated by magma,” according to Andreas Pflitsch of the University of Ruhr-Bochum in Germany, a world expert on cave climatology.

Pflitsch is part of a team of scientists studying what the atmospheric conditions are like inside these rarely seen icy cold cave environments. They want to understand how hot and abundant the glacier meltwater is, what impact steam has on the temperature of the caves and how it changes over the seasons, and what the wind currents are and how they affect the shape of the ice caverns (wind ablates and re-contours the walls of ice).

We still have several weeks of meteorological summer to go. So to beat the heat, go subterranean and cool off in a cave.