A gold mine worker displays gold in a local mine in Al-Ibedia locality at River Nile State, July 30, 2013. (Photo by Mohamed Nureldin Abdallah/Reuters)

Merit: A Night at Deadvlei. The night before returning to Windhoek, we spent several hours at Deadveli. The moon was bright enough to illuminate the sand dunes in the distance, but the skies were still dark enough to clearly see the milky way and magellanic clouds. Deadveli means “dead marsh. The camelthorn trees are believed to be about 900 years old, but have not decomposed because the environment is so dry. (Photo and caption by Beth McCarley/National Geographic Traveler Photo Contest)

American students going wild during their Spring Break week-long recess in Cancun, Mexico on March 10, 2007. (Photo by Keystone USA/ZUMA Press/Rex Features/Shutterstock)

A crocodile at a zoo in the southern Taiwan city of Kaohsiung holds the forearm of a zoo veterinarian in its teeth, April 2007. Surgeons in Taiwan have reattached a vet's arm, after it was bitten off by a crocodile as he tried to give it an anaesthetic injection. His attacker is one of a pair of Nile crocodiles kept at Shoushan zoo. Nile crocodiles are known to be man-eaters, but are also listed as an endangered species. (Photo by Frank Lin/Reuters)

Cole Yeoman steps over a large crack along River Road, Avonside on February 25, 2011 in Christchurch, New Zealand. The death toll has risen to 113 and the hope for finding survivors is fading as rescuers search through debris for over 200 still missing following a 6.3 magnitude earthquake that struck Christchurch on Tuesday. The quake, which was an aftershock of a 7.1 magnitude quake that struck the South Island city on September 4, 2010, has seen damage and fatalities far exceeding those of the original. (Photo by Martin Hunter/Getty Images). CHRISTCHURCH, NEW ZEALAND – FEBRUARY 25

Young Slovaks dressed in traditional costumes throw a bucket of water at a girl as part of Easter celebrations in the village of Trencianska Tepla, Slovakia, April 9, 2012. Slovakia's men splash women with water to symbolize youth, strength and beauty for the upcoming spring season. (Photo by Samuel Kubani/AFP)

In this June 29, 2016 file photo, boats docked at Central Marine in Stuart, Fla., are surrounded by blue green algae. The 153-mile-long Indian River Lagoon has been plagued by harmful algae blooms. Water quality testing data analyzed by the AP showed the average phosphorous level – a byproduct of fertilizers and human waste that algae thrive on, rose nearly 75 percent between 2000 and 2016. (Photo by Greg Lovett/The Palm Beach Post via AP Photo)

A pale tussock moth (Calliteara pudibunda) larva or caterpillar just after moulting on heather on Hankley Common, Surrey, England on April 30, 2019. (Photo by Gillian Pullinger/Alamy Stock Photo)