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 hyper realistic drawings are so lifelike they could pass for photographs. The incredibly detailed works of art were created by self-taught artist Ivan Hoo, from Singapore, who earns a living from his realistic drawings and paintings. The 31-year-old takes up to three days to complete the impressive pieces, which include animal portraits and still life drawings of everyday items such as a Starbucks cup. The A3 sketches are completed using a range of soft pastel pencils and are drawn from still life, or a photograph taken by Ivan himself. Here: Ivan Hoos drawing of a pug. (Photo by Ivan Hoo/Caters News)

Reuters photographers Carlos Barria and Bobby Yip photographed protestors and details of life on the barricades, asking demonstrators what their role was in the movement, and what they wanted to happen. Here: Crystal, 15, a part-time boutique sales assistant, poses on Nathan Road in Mongkok shopping district in Hong Kong October 7, 2014. Holding a walkie talkie for fast communication with other supporters, Crystal said, “I am not demanding Chief Executive Leung Chun-ying to quit, but (want) to protect protesters from being threatened badly by opponents and the police”. (Photo by Bobby Yip/Reuters)

Tao Xiangli gets out of his homemade submarine after operating it in a lake on the outskirts of Beijing September 3, 2009. Amateur inventor Tao, 34, made a fully functional submarine, which has a periscope, depth control tanks, electric motors, manometer, and two propellers, from old oil barrels and tools which he bought at a second-hand market. He took 2 years to invent and test the submarine which costs 30,000 yuan ($4,385). (Photo by Christina Hu/Reuters)

A Russian air force technician reports to a pilot that a bomber is ready for a combat mission at Hemeimeem air base in Syria Wednesday January 20, 2016. Russian warplanes have flown over 5,700 combat missions since Moscow launched its air campaign in Syria on September 30, 2015. (Photo by Vladimir Isachenkov/AP Photo)

The Lamb National takes place for the racegoers at Ascot Racecourse on April 2, 2017 in Ascot, England. (Photo by Alan Crowhurst/Getty Images)

Autos sit on top of each other in a washed out section of Dog Track Road in the Millview community as Gulf Coast residents continue cleaning up from damage caused by torrential rains in Pensacola, Fla., Thursday, May 1, 2014. The National Weather Service, estimated 15-20 inches of rain has fallen in the Pensacola area in the past 2 days. (Photo by G. M. Andrews/AP Photo)

Brian Skerry can be called many things – explorer, journalist, conservation advocate – but he is first and foremost a photographer. His journeys to capture amazing underwater photographs have taken him across the world’s oceans. Photo: This Bahamian oceanic whitetip shark, known for the distinctive coloring on its white-tipped, rounded extremities, is part of a globally threatened species due to overfishing demands, primarily for its fins. (Photo by Brian Skerry)