A family tries to cross a flooded road amid gushing water in Kolkata, India on August 17, 2019. Heavy rain continues for a second day in Kolkata, which contuinued to flood many streets all around the city. Authorities are working overtime to clear the roads. (Photo by Debarchan Chatterjee/Zuma Wire/Rex Features/Shutterstock)

This Thursday, April 30, 2015 photo shows Lebanese citizens walking on the Corniche, or waterfront promenade in Beirut, Lebanon. This photo was shot through the lowered veil of a niqab, which is worn by some conservative Muslim women. The cloth allows women to follow a strict interpretation of their religious beliefs by preventing others from seeing their faces. (Photo by Hassan Ammar/AP Photo)

A picture made available on 17 July 2015 shows the bright line of the Milky Way above the old oaks at the Rogalin landscape Park in Rogalin village, near Poznan, on the night of 16 July 2015. (Photo by Lukasz Ogrodowczyk/EPA)

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)

Italy's Mount Etna, Europe's tallest and most active volcano, spews lava as it erupts on the southern island of Sicily, Italy, February 28, 2017. (Photo by Antonio Parrinello/Reuters)

Eddie Ladd and Gwyn Emberton perform as Dylan and Caitlin Thomas in “Caitlin” at the Lauriston Hall, Edinburgh, Scotland on August 25 2017. (Photo by Mary Turner/Reuters)

A worker spreads paddy crop for drying in a rice mill complex on the outskirts of Ahmedabad February 3, 2011. (Photo by Amit Dave/Reuters)

Elderly women wait for customers as they sell their self-made food products at a street market, with a graffiti depicting Russian President Vladimir Putin on the wall of a house seen in the background, in the town of Kashira, outside Moscow, Russia on October 10, 2017. (Photo by Andrey Volkov/Reuters)