On the western side of Mount Hood lies the longest glacier cave system in the contiguous United States. In 2012, these caves were mapped to a combined length of 7,166.8 feet by cave explorers Brent McGregor and Eddy Cartaya. Currently, the total passage length is hundreds of feet less. Glaciers are frozen rivers; they are always moving and changing... (Photo and caption by Josh Hydeman)

Actors perform the living Nativity biblical scenes in Postojna cave in Postojna, Slovenia, December 22, 2015. (Photo by Srdjan Zivulovic/Reuters)

This photographer is walking on thin ice after taking stunning photographs inside an Alaskan ice cave that could collapse at any moment. With it's dazzling turquoise walls and and huge open spaces, it's hard to imagine that this incredible frozen cavern was only formed at the beginning of 2012. But despite it's seemingly mystical allure, the fascinating natural phenomena is at risk of collapsing in on itself without warning. (Photo by Ron Gile/Caters News)

These stunning photographs really do show a land of fire and ice! The frozen landscape of the Olkhon Islands, Russia, appears to be ablaze in some of these pictures as the icy sheets of the glaciers reflect the early morning suns rays. (Photo by Vladimir Ryabkov/Caters News Agency)

These frozen caves seem almost otherworldly as they daylight illuminates them. Matej Kriz’s shots reveal the beauty of the brilliant caves, but he’s also very aware of how deadly they can be. The photographer captured the amazing shots in the Vatnajokull National Park on the Breidamerkurjokull glacier tongue. Here: The ice caves, taken in the Vatnajokull National Park in Iceland, on November 11, 2017. (Photo by Matej Kriz/Caters News Agency)

An English Bulldog plays with its owner during a parade where more than 900 English Bulldog participate to set the Guinness World Records for the largest Bulldog walk in Mexico City, Mexico February 26, 2017. (Photo by Carlos Jasso/Reuters)

Russian President Vladimir Putin, center, uses a binocular, as Defense Minister Sergei Shoigu, left, and chief of Russia's military's General Staff Valery Gerasimov, right, observe military exercises near the Baikal Lake on Wednesday, July 17, 2013. (Photo by Alexei Nikolsky/AP Photo/RIA Novosti/Presidential Press Service)

Steam enthusiasts demonstrate their engines at the Great Dorset Steam Fair, the biggest event of its kind in Europe on September 2, 2011 in Tarrant Hinton, near Blandford, England. Over 200,000 people are expected to attend the 600 acre event, which is in its 43rd year and includes displays and demonstrations of steam and vintage machinery over five days. (Photo by Matt Cardy/Getty Images)