“Kilauea Rules”. The most extreme place we put ours kayakers to paddle till now. Photo location: Big Island, Hawaii. (Photo and caption by Alexandre Socci/National Geographic Photo Contest)

Ramoncito Campo kisses his wife Hernelie Ruazol Campo on a flooded street during a southwest monsoon that battered Manila August 8, 2012. The newly-wed couple pushed through with their scheduled wedding despite severe flooding that inundated wide areas of the capital and nearby nine provinces. (Photo by Reuters/Courtesy of Ramoncito Campo)

Masooma Alizada (L) and Frozan Rasooli (R), members of Afghanistan's Women's National Cycling Team prepare a bicycle before training on the outskirts of Kabul February 20, 2015. Afghanistan's Women's National Cycling Team has been breaking new ground for women's sports and pushing the boundaries of what is – and is not – acceptable for young women in the conservative Muslim country. (Photo by Mohammad Ismail/Reuters)

In this February 2, 2015 photo, tourists jump as they pose for a picture, after disembarking from the Ocean Nova cruise ship, on King George Island, Antarctica. This tourist season, which runs November through March, more than 37,000 visitors are expected to walk on the coldest continent on Earth, about 10 percent more than the year before. (Photo by Natacha Pisarenko/AP Photo)

Iranians flash the victory sign from their car while celebrating on a street in northern Tehran, Iran, Thursday, April 2, 2015, after Iran's nuclear agreement with world powers in Lausanne, Switzerland. The United States, Iran and five other world powers on Thursday announced an understanding outlining limits on Iran's nuclear program so it cannot lead to atomic weapons, directing negotiators toward achieving a comprehensive agreement within three months. (Photo by Ebrahim Noroozi/AP Photo)

A dog sits in the shade of a mangrove tree as a woman uses a fork to dig for shellfish on the reef-mud flats of a lagoon located at South Tarawa in the central Pacific island nation of Kiribati May 23, 2013. Kiribati consists of a chain of 33 atolls and islands that stand just metres above sea level, spread over a huge expanse of otherwise empty ocean. With surrounding sea levels rising, Kiribati President Anote Tong has predicted his country will likely become uninhabitable in 30-60 years because of inundation and contamination of its freshwater supplies. (Photo by David Gray/Reuters)

A female Kurdistan Workers Party (PKK) fighter stands near a security position in Sinjar, March 13, 2015. Women fighters at a Kurdistan Workers Party (PKK) base on Mount Sinjar in northwest Iraq, just like their male counterparts, have to be ready for action at any time. Smoke from the front line, marking their battle against Islamic State, which launched an assault on northern Iraq last summer, is visible from the base. Many of the women have cut links with their families back home; the fighters come from all corners of the Kurdish region. (Photo by Asmaa Waguih /Reuters)

A visitor poses for a photo with a Crayon Shin-chan model during an exhibition at Joy City in Beijing May 5, 2015. The exhibition, which showcased fifty models of the Japanese cartoon character in different poses and expressions, will run from April 18 to June 22. (Photo by Jason Lee/Reuters)