Pro-Russian rebels stand near a monument during a ceremony to honour the World War Two defenders of Donetsk from Nazi forces, in Donetsk, in this September 8, 2014 file photo. (Photo by Marko Djurica/Reuters)

Mount Sinabung volcano erupts, as seen from Tiga Pancur village, Karo Regency in Indonesia's North Sumatra province, in this October 8, 2014 file photo. (Photo by Y. T. Haryono/Reuters)

“Diver in Magic Kingdom”. Green Lake (Grüner See) is located Tragöss Austria. In spring snowmelt raises the lake level about 10 meters. This phenomenon, which lasts only a few weeks covering the hiking trails, meadows, trees. The result is magical to watch diving landscapes. Photo location: Grüner See at Tragöss, Austria. (Photo and caption by Marc Henauer/National Geographic Photo Contest)

“The Net thrower”. The fisherman are conducting activities on Situgunung Lake. Photo location: Situgunung lake, Sukabumi, West Java, Indonesia. (Photo and caption by Dody Kusuma/National Geographic Photo Contest)

Actress Frederique Bel attends the Opening ceremony and the “Grace of Monaco” Premiere during the 67th Annual Cannes Film Festival on May 14, 2014 in Cannes, France. (Photo by Pascal Le Segretain/Getty Images)

A female bodybuilder apples oil to another performer backstage before an amateur competition in the Israeli city of Dimona, in this April 3, 2014 file photo. (Photo by Finbarr O'Reilly/Reuters)

A prisoner from the Pedrinhas prison is carried to receive medical help after he was injured during a fight between rival gangs inside the jail, in Sao Luiz, capital of Maranhao state, January 8, 2014. The recent posting on a major Brazilian news website of a video filmed last December 17 by Pedrinhas prisoners of the decapitated and tortured bodies of rival inmates inside the jail has highlighted some of the problems present in the country's prison system which houses nearly twice as many prisoners as its capacity, according to official statistics. (Photo by Douglas Cunha/Reuters/O Estado do Maranhão)

In this undated photo made available by journal Nature on January 15, 2014, a northern bald ibis (Geronticus eremita) flies in Tuscany, Italy. A new study released Wednesday, January 15, 2014 says the birds choreograph the flapping of their wings, getting a boost from an updraft of air in the wake of the flapping wings by flying behind the first bird and off to the side. When a flock of birds take advantage of these aerodynamics, they form a V. (Photo by Markus Unsöld/AP Photo)