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)

An approximately 8 year-old male orangutan named Siamang reacts under the influence of tranquilizer as it's being prepared to be released into the wild at a rehabilitation center in Kuta Mbelin, North Sumatra, Indonesia, Friday, July 10, 2015. The orangutans at the center were mostly rescued from palm oil plantations or confiscated from homes where they were kept as pet animals. Orangutan populations in Indonesia's Borneo and Sumatra island are facing severe threats from habitat loss, illegal logging, fires and poaching. Conservationists predicted that without immediate action, orangutans are likely to be the first great ape to become extinct in the wild. (Photo by Binsar Bakkara/AP Photo)

Students wearing masks rest amid the coronavirus disease (COVID-19) pandemic in Seoul, South Korea, August 25, 2020. (Photo by Kim Hong-Ji/Reuters)

A Sri Lankan elephant, accompanied by his mahout, browse through a roadside fruit stall in Colombo on January 19, 2015. The Sri Lankan elephant is listed as endangered by the International Union for Conservation of Nature (IUCN) as the population has declined by at least 50 percent over the last three generations, with the species threatened by habitat loss, degradation and fragmentation. (Photo by Lakruwan Wanniarachchi/AFP Photo)

People walk with their arms raised as security forces restore order in Nice, France on July 14, 2016. (Photo by SIPA Press/Rex Features/Shutterstock)

Rabbits are seen in a cage, which is placed by authority as a test of the living conditions near the site of last week's blasts at Binhai new district in Tianjin, China, August 19, 2015. According to local media, the animals were alive after being placed near the blasts site for two hours. Four new fires have broken out at the site where two huge blasts last week killed 116 people, Chinese state media reported Friday soon after officials said safety hazards were found at almost 70 percent of firms handling dangerous chemicals in Beijing. (Photo by Reuters/Stringer)

A Sotheby's employee holds a rare 52.82-carat white diamond ring at Sotheby's auction house on April 12, 2010 in London, England. Price: 7 million USD. (Photo by Dan Kitwood/Getty Images)

A barber cuts hair of his client at a shuttered market during the countrywide traders strike in Lahore on October 29, 2019. Pakistani traders have joined hands to observe a nationwide shutterdown strike against the government over its “anti-business” policies, seeking to bring trade and economic activities across the country to a standstill on October 29 and 30. (Photo by Arif Ali/AFP Photo)