Three Chinese soldiers at the time of a civil war in China. (Photo by General Photographic Agency/Getty Images). 1922

A man lays in front of a tank in the entrance to Istanbul's Ataturk airport, early Saturday, July 16, 2016. Members of Turkey's armed forces said they had taken control of the country, but Turkish officials said the coup attempt had been repelled early Saturday morning in a night of violence, according to state-run media. (Photo by Ismail Coskun/IHA via AP Photo)

U.S. Army soldiers with the 1st Battalion, 501st Infantry Regiment deployed to Combat Outpost Sabari, Afghanistan scan their area as they begin a multi-day air assault mission near the Pakistani border of eastern Afghanistan's Khost province May 2, 2012. (Photo by Staff Sgt. Joshua L. DeMotts/U.S. Air Force)

Kelimutu is a volcano, close to the small town of Moni about 50 km to the east of Ende, Indonesia in central Flores Island of Indonesia.

Students stand on the roof of a wooden boat as haze blankets the Musi River while they travel to school in Palembang, on Indonesia's Sumatra island, September 10, 2015. Indonesia is investigating 10 firms over worsening forest fires that have created a blanket of smog over Southeast Asia, threatening them with sanctions if they are found responsible, a government minister said on Tuesday. The thick haze from Indonesia's Sumatra and Kalimantan islands has forced the repeated cancellation of flights in the area and pushed air quality to unhealthy levels in neighbouring Singapore and Malaysia. (Photo by Reuters/Beawiharta)

Women take pictures between stone sculptures of half-buried people at the Lapindo mud field in Sidoarjo, October 11, 2015. Disaster tourism has become more common in Indonesia, where visitors are drawn to sites of earthquakes, floods and volcanic eruptions to witness the aftermath of catastrophes or simply do some soul-searching. (Photo by Reuters/Beawiharta)

The wreckage of a van is overgrown by plants in Simacem village in North Sumatra, Indonesia, November 16, 2015. The village was abandoned following the eruption of Mount Sinabung as it was considered too close to the still rumbling volcano. (Photo by Binsar Bakkara/AP Photo)

Indonesian rescuers search for victims of the crashed military airplane in Medan, North Sumatra, Indonesia, 30 June 2015. At least people 49 people were killed after an Indonesian military plane crashed in North Sumatra and burst into flames, officials said. Air Force chief Air Marshal Agus Supriatna said there were no survivors after the plane ploughed into houses and commercial buildings in Medan, the country's third largest city. The plane left Jakarta with 113 people aboard, including military personnel and their relatives, but it was not clear how many continued the journey to Medan after stopovers in Pekanbaru and Dumai, Agus said. (Photo by Dedi Sahputra/EPA)