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)

These stunning images document the everyday lives of the men, women and children of the Mentawai tribe. The Mentawai people, a native population in Indonesia, are famous for their decorative tattoos and for living a semi-nomadic life on the Mentawai Islands in West Sumatra. Shot by professional photographer Mohammed Saleh Bin Dollah, the series captures a glimpse of life on the island as the Mentawai men smoke and hunt for food and the children play in the river. Here: A young boy helps a woman to prepare food taken on July 19, 2014 on the Mentawai Islands, Indonesia. (Photo by Muhamad Saleh Dollah/Barcroft Media)

Nikolai Vasilyev, 62, dressed as Father Frost, Russian equivalent of Santa Claus, water-skis along the Yenisei River outside Siberian city of Krasnoyarsk, Russia, December 10, 2015. Vasilyev, a teacher of the Krasnoyarsk Aerospace Academy, constructed the self-made water skis to travel on the water surface. The skis are made of plastic foam and the sticks are designed to propel him forward. (Photo by Ilya Naymushin/Reuters)

A damaged traffic signal is pictured along a street at a residential area flooded by the Kinugawa river, caused by typhoon Etau in Joso, Ibaraki prefecture, Japan, September 11, 2015. Unprecedented rain in Japan unleashed heavy floods on Friday that tore houses from their foundations, uprooted trees and forced more than 100,000 people from their homes. (Photo by Issei Kato/Reuters)

Master of throat singing (or Khoomei) Aikhan Orzhak (L) and model Choigana Kertek, dressed in traditional costume, perform during sunset at the Aldyn Bulak area on the bank of the Yenisei River outside the village of Ust-Elegest in Tuva region, Southern Siberia, Russia, October 7, 2015. The region is inhabited by Tuvans, historically cattle-herding nomads, who nowadays practise two main confessions – Buddhism and Shamanism. (Photo by Ilya Naymushin/Reuters)

A view shows “The Farnese Bridge”, a participatory monumental cardboard installation by French artist Olivier Grossetete, over the Tiber river in front of the Palazzo Farnese, the seat of the French embassy in Italy, during its inauguration in Rome on July 13, 2021. A French Embassy project, the Farnese bridge is the realization of the dream of Cardinal Farnese, who wished to build a bridge over the Tiber to connect Palazzo Farnese to the gardens of the Villa Farnesina. A project, at the time, entrusted to Michelangelo, but that remained unfinished. (Photo by Filippo Monteforte/AFP Photo)

A man in Yakutsk, the capital of the Sakha Republic (Yakutia) in the Russian Far East on November 23, 2021. Located in Tuimaada Valley on the Lena River, Yakutsk is the largest city in the permafrost zone. On 23 November 2021, the daytime temperature ranged between –35 and –31 degrees Celsius in Yakutsk. On the night between 22 and 23 November, the temperature went down to –37 degrees Celsius. (Photo by Vadim Skryabin/TASS)

Frost covers part of the face of University of Minnesota student Daniel Dylla during a morning jog along Mississippi River Parkway Tuesday, January 29, 2019, in Minneapolis. Extreme cold and record-breaking temperatures are crawling into parts of the Midwest after a powerful snowstorm pounded the region, and forecasters warn that the frigid weather could be life-threatening. (Photo by David Joles/Star Tribune via AP Photo)