A resident carries a gas canister as an ash cloud hovers above during an eruption of Mount Sinabung volcano at Tiga Serangkai village in Karo Regency, North Sumatra province, Indonesia June 24, 2015. More than 10,000 people from 12 villages, who are living around the slopes of Mount Sinabung, left their homes and moved to refugee camps, local media reported. (Photo by Reuters/Beawiharta)

Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)

Tourists gather to watch Mount Agung at Amed beach in Karangasem on Indonesia' s resort island of Bali on November 30, 2017. Thousands of foreign tourists were expected to leave Bali by plane on November 30 following a nearly three- day airport shutdown sparked by a rumbling volcano on the Indonesian holiday island. (Photo by Juni Kriswanto/AFP Photo)

Miners pulling up lazy tourists to the rim of Kawah Ijen (Ijen Volcano), East Java, Indonesia on September 21, 2017. They will earn as much as they would bring down a load of sulfur. Nomadic Explorer, Cultural Lifestyle Photographer Claudio Sieber captured striking images of miners working at Ijen volcanic range in East Java, Indonesia. The sulphur miners risk their lives daily as they climb the active volcano carrying heavy loads, which they sell to sugar refineries. (Photo by Claudio Sieber/Barcroft Images)

Nelson Hernandez flashes the victory sign as he shows off one of the voodoo dolls that he is selling at El Viejo Lazaro Botanica to try and help the Miami Heat fans root their team on against the Dallas Mavericks in the NBA finals on June 9, 2011 in Miami, Florida. The dolls made from cotton come in white or black and they are all the same size. The user of the doll must have the name of the player attached to the doll, which is filled with cotton, herbs, sticks and a special powder. (Photo by Joe Raedle/Getty Images)

A screen shows the new Automated Target Recognition software as a TSA employee, who couldn't provide her name, waits to walk into the advanced imaging technology unit to demostrate the new software that has been installed at Miami International Airport on August 23, 2011 in Miami, Florida. The new software is designed to enhance passenger privacy by eliminating passenger-specific images and instead auto-detecting potential threat items and indicating their location on a screen which shows a generic outline of a person. (Photo by Joe Raedle/Getty Images)

Gina Labianca (L) tries on a super woman outfit as Charlie Lucas tries a snow white Costume at the Halloween MegaStore Miami Beach on October 21, 2011 in Miami Beach, Florida. The megastore is a temporary location for the store which opened for the holiday to sell costumes, masks and other items to people needing to dress up for the evening of October 31 when costumed people around the world observe the day. (Photo by Joe Raedle/Getty Images)

“For most Londoners, the most common view they enjoy as they trudge to work is the back of another commuter's head. But now, thanks to the Streetmuseum app, anyone traipsing through the capital's streets can step back in time to see what London looked like in the 19th and 20th century compared with today – all in the same image”. – Joe Krishnan via The Independent. Photo: A street scene in London’s Covent Garden with the underground station and a horse and cart in the background in c.1930 and the same street in 2014. (Photo by Museum of London/Streetmuseum app)