A visitor passes behind the sculpture “Puma-Dentist” made with plastic, wax and original heads of a puma and a hind by Austrian artist Deborah Sengl during an exhibition at the art gallery Deschler in Berlin April 15, 2008. (Photo by Fabrizio Bensch/Reuters)

A round circle of smoke coming from the mouth of the Etna volcano is seen in the sky during an eruption on the southern Italian island of Sicily April 11, 2013. Mount Etna is Europe's tallest and most active volcano. (Photo by Antonio Parrinello/Reuters)

A visitor looks at a sculpture entitled “Couple Under an Umbrella, 2013” by artist Ron Mueck during the press day for his exhibition at the Fondation Cartier pour l'art contemporain in Paris April 15, 2013. (Photo by Charles Platiau/Reuters)

Migrants ride on top of a northern bound train toward the US-Mexico border in Juchitan, southern Mexico, Monday, April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. (Photo by Eduardo Verdugo/AP Photo)

A girl jumps to touch cherry blossoms in full bloom in Fussa, outskirts Tokyo, Japan, 05 April 2014. Temperatures being very constant made blossoms to keep full bloom for holiday makers. (Photo by Kimimasa Mayama/EPA)

Myouchin Munehisa, 44, as he finishes Hibashi iron bells made of iron on a production line at Myochin Honpo shop on April 25, 2014 in Himeji, Japan. Myochin family's iron business, started in the Heian period (794-1185) of Japan as an armor and helmet maker, shifted as the needs of people changed in the course of history. (Photo by Buddhika Weerasinghe/Getty Images)

A Nepalese boy gets ready to perform a stick dance during a rally held to pay tribute to the victims of an earthquake, in Bhaktapur, Nepal, Wednesday, September 2, 2015. Two powerful earthquakes in April and May devastated the Himalayan nation killing more than 8,800 people. (Photo by Niranjan Shrestha/AP Photo)

Firefighters pull a pig as they try to rescue it from a well at a pig farm in Huanghua township of Leqing, Zhejiang province, China, April 25, 2014. Seven local firefighters successfully rescued the 300 kg (661 lbs) pig, local media reported. (Photo by Reuters/China Daily)