A woman smokes a mask bong on the final day of Hempfest, Seattle's annual gathering to promote the legalization of marijuana, on August 17, 2014. (Photo by Jordan Stead/Seattlepi.com)

A photo taken on August 29, 2014, shows Mount Tavurvur erupting in eastern Papua New Guinea, spewing rocks and ash into the air, forcing the evacuation of local communities and international flights to be re-routed. Mount Tavurvur, which destroyed the town of Rabaul when it erupted simultaneously with nearby Mount Vulcan in 1994, rumbled to life early in the morning on the tip of the remote island of New Britain. (Photo by Oliver Bluett/AFP Photo)

In this Monday, September 22, 2014 photo provided by the Utah Division of Wildlife Resources, a young cougar is released back into Utah's mountains by the Utah Division of Wildlife Resources in an undisclosed site in central Utah. State wildlife officials received reports of the cougar roaming Sunday afternoon in a residential area of the city's eastern flank, a few miles from the base of the Wasatch Mountains. Authorities say cougars generally avoid humans but sometimes enter neighborhoods close to their mountain habitats. (Photo by Steve Gray/AP Photo/Utah Division of Wildlife Resources)

Dhruva Aliman does a back somersault as he dismounts from a slackline on the beach at Santa Monica, California on October 19, 2014. Slackline is a balance sport where a line of webbing is adjusted at different levels of tension between two anchor points and participants (called slackers) perform tricks and stunts including somersaults. (Photo by Mark Ralston/AFP Photo)

A P-51 Mustang named “Charlotte's Chariot” from the Southern Heritage Air Foundation flies past a cloud of smoke and fire from a nearby battle reenactment during the Wings Over Houston Airshow in Houston, on Saturday, November 1, 2014. Battle reenactments are part of the yearly show held at Ellington Airport. (Photo by Kar Hlava/AP Photo/Bay Area Citizen)

West Berliners crowd in front of the Berlin Wall as they watch East German border guards demolish a section of the wall on November 11, 1989. (Photo by Gerard Malie/AFP Photo)

Revellers wearing lanterns parade through the streets during the carnival procession of Basel, Switzerland, 15 February 2016. The traditional Morgestraich starting Monday morning after Ash Wednesday at 4 a.m. marks the kick-off of the Carnival of Basel. (Photo by Patrick Seeger/EPA)

A model presenting a creation from Andres Sarda's Fall/Winter 2016 collection prepares to pose for a portrait backstage during the Mercedes-Benz Fashion Week in Madrid, Spain, February 21, 2016. (Photo by Susana Vera/Reuters)