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)

A Dutch Military Policeman, left inside, guards part of the reconstructed cockpit, right, and forward section of the fuselage after the Dutch Safety Board presented it's final report into what caused Malaysia Airlines Flight 17 to break up high over Eastern Ukraine last year, killing all 298 people on board, during a press conference in Gilze-Rijen, central Netherlands, Tuesday, October 13, 2015. (Photo by Peter Dejong/AP Photo)

Revellers take part in the annual “Naval Battle” of Vallecas in Madrid, Spain July 19, 2015. The slogan for this year's water battle is “Get wet for Alfon, freedom for Alfon”, referring to Alfonso Fernandez Ortega, a Vallecas resident who was sentenced to four years in prison in June. The festival was started spontaneously in 1981 when some neighbours started to throw water at one another due to high temperatures during the Virgen del Carmen Festival. (Photo by Juan Medina/Reuters)

A swimmer stops short of a red algae bloom at Sydney's Clovelly Beach on November 27, 2012, which closed some beaches for swimming including Bondi Beach for a period of time. While the red algae, known as Noctiluca scintillans or sea sparkle, has no toxic effects, people are still advised to avoid swimming in areas with discoloured water because the algae, which can be high in ammonia, can cause skin irritation. (Photo by William West/AFP Photo)

In this photo released by Xinhua News Agency, a worker drinks at the construction site of the T3B terminal project of Chongqing Jiangbei International Airport in southwest China's Chongqing, July 11, 2022. Flooding and extreme high temperatures have caused multiple deaths in eastern China as summer heat descends earlier than usual. (Photo by Huang Wei/Xinhua via AP Photo)

A man walks near a boat which has capsized due to strong winds in Istanbul on November 30, 2021. Strong winds continue to blow across Istanbul where the Bosphorus strait is temporarily closed to boat traffic. Four people were killed and dozens injured on Monday in Istanbul, which was hit by high winds. (Photo by Yasin Akgul/AFP Photo)

A woman pushes a child aboard a plastic basin as they wade through floodwaters brought about by Super Typhoon Noru on September 26, 2022 in San Miguel, Bulacan province, Philippines. Super Typhoon Noru made landfall in the Philippines overnight, causing widespread flooding and leaving at least five dead. High winds and heavy rains have flattened villages and have increased the threat of landslides. (Photo by Ezra Acayan/Getty Images)

A child wades through floodwater brought about by Super Typhoon Noru on September 26, 2022 in San Miguel, Bulacan province, Philippines. Super Typhoon Noru made landfall in the Philippines overnight, causing widespread flooding and leaving at least five dead. High winds and heavy rains have flattened villages and have increased the threat of landslides. (Photo by Ezra Acayan/Getty Images)