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)

Former Vice President Joe Biden, 2020 Democratic presidential candidate, right, watches as his wife Jill Biden, center, blocks a protester from arriving on stage during an primary night rally in the Baldwin Hills neighborhood of Los Angeles, California, U.S., on Tuesday, March 3, 2020. The biggest day of the presidential primary calendar will define the nomination fight for Bernie Sanders and Biden and determine whether Michael Bloomberg and Elizabeth Warren have a rationale for carrying on their campaigns. (Photo by Patrick T. Fallon/Bloomberg via Getty Images)

A Palestinian man demonstrates his parkour skills on a beach as the coronavirus disease (COVID-19) restrictions ease in Gaza City on July 10, 2020. (Photo by Mohammed Salem/Reuters)

Nepalese army personnel pay tributes before the body of a person who died of COVID-19 before cremating the same in Kathmandu, Nepal, Monday, August 17, 2020. (Photo by Niranjan Shrestha/AP Photo)

Turkana tribesmen walk with guns to protect their cattle from rival tribes near Baragoy, Kenya August 4, 2017. (Photo by Goran Tomasevic/Reuters)

Empty gloves are seen at the side of a tray of Maryland Blue Crabs at Maine Avenue Fish Market which is the United States oldest fish market in continual operation since 1805, in Washington, U.S., May 6, 2019. (Photo by Clodagh Kilcoyne/Reuters)

A Palestinian man bathes his camel in the sea during a dust storm in Gaza City on March 23, 2021. (Photo by Mohammed Abed/AFP Photo)

Workers fold up a billboard to prepare for the coming of typhoon Vongfong, in Manila, Philippines on Thursday May, 14, 2020. The first typhoon to hit the country this year roared toward the eastern Philippines on Thursday as authorities work to evacuate tens of thousands of people while avoiding overcrowding in shelters that could spread the coronavirus. (Photo by Aaron Favila/AP Photo)