Inside the Afar Triangle in Ethiopia’s Danakil desert, camel caravans are used to carry salt. For centuries, the essential mineral has been mined by the Afar people, known for their ability to withstand extremes. The terrain is rugged, travelers are scarce and so are motor vehicles, where the average annual temperature is the highest in the world, and can rise to 122 degrees Fahrenheit, 50 degrees Celsius. (Photo by Ziv Koren/Polaris)

A gold prospector is detained by agents of Brazil’s environmental agency on the Uraricoera River during an operation against illegal gold mining on indigenous land, in the heart of the Amazon rainforest, in Roraima state, Brazil April 15, 2016. At over 9.5 million hectares, the Yanomami territory is twice the size of Switzerland and home to around 27,000 indians. The land has legally belonged to the Yanomami since 1992, but illegal miners continue to plague the area, sawing down trees and poisoning rivers with mercury in their lust for gold. (Photo by Bruno Kelly/Reuters)

A truck carrying iron ore moves along a road at the Fortescue Metals Group (FMG) Christmas Creek iron ore mine located south of Port Hedland in the Pilbara region of Western Australia, November 17, 2015. (Photo by Jim Regan/Reuters)

A model walks the runway during the Di$count Universe show at Mercedes-Benz Fashion Week Resort 17 Collections at Carriageworks on May 18, 2016 in Sydney, Australia. (Photo by Stefan Gosatti/Getty Images)

Fireworks light up the skyline over Sydney Harbour during the midnight fireworks session as Sydney Celebrates New Year's Eve with the theme of “Time To Dream” on on January 1, 2012 in Sydney, Australia. (Photo by Ryan Pierse/Getty Images)

Martin Garwood prepares to release baby penguins at Sydney Aquarium on January 18, 2012 in Sydney, Australia. Three baby penguins were released into the aquarium and reunited with their parents for the first time since birth. (Photo by Lisa Maree Williams/Getty Images)

Stefan Libon proposes to girlfirend Jess McGarrity in front of a banner message “Marry Me Jess?” on the deck of the Queen Mary 2, at Mrs Macquarie's Chair on Valentines day, February 14, 2012 in Sydney, Australia. (Photo by James Morgan/Carnival Australia via Getty Images)

A bodyboarder rides a wave at Mackenzies Bay on May 1, 2011 in Sydney, Australia. A strong east-south-east swell has developed along the NSW coastline with waves between 6ft and 8ft expected to hit the coast for much of the weekend and into next week. (Photo by Cameron Spencer/Getty Images)