The Eye of the Sahara (a Richat Structure), Mauritania: This enormous depression, circular in shape and stretching 25 miles wide, is like a bull’s-eye mark in the middle of an otherwise flat and featureless area of Mauritania desert. Visible from space, it has been a landmark for astronauts since the earliest missions. The Eye isn’t the result of any target practice by aliens; rather, it formed as winds eroded the different layers of sediment, quartzite, and other rocks at varying depths.
Sailing Stones on Racetrack Playa, Death Valley, California, USA: No one has ever seen one of the “sailing stones” on Death Valley’s Racetrack Playa move, but evidence of their travels is visible in the long track marks that trail behind them in the dusty ground. Scientists aren’t sure exactly how the rocks—which can weigh hundreds of pounds—make their way across the dry lake bed. The prevailing theory is that when the rocks are wet or icy, they’re pushed along the flat playa by strong winds. The deep groove marks they leave behind indicate they may travel up to 700 feet from their point of origin.
The Stone Forest (Shilin) in Yunnan Province, China: Many of the trees within the forest in China’s remote Yunnan Province are rock hard, literally. The area, which spans nearly 200 square miles, was underwater 270 million years ago, and the sea floor was covered with limestone sediment. Gradually, the seabed rose and the water dried up. As rain and wind eroded the weaker rock, the stronger limestone spires began to take shape. Now they rise skyward, surrounded by leafy trees.
Salar de Uyuni, Bolivia: When a prehistoric lake dried up about 30,000 years ago, it left an endless expanse of white hexagonal tiles that stretch to the horizon. Welcome to the world’s largest salt flat, stretching for 4,000 square miles—25 times the size of Utah’s Bonneville Salt Flats. The site provides more than 25,000 tons of salt per year to local miners, supports a thriving community of thousands of flamingos, and attracts tourists who can check into the Palacio de Sal, a 16-room hotel made entirely from salt blocks.
Spotted Lake, British Columbia, Canada: It looks almost as if you could play Twister on Spotted Lake near Osoyoos, less than a mile from the Washington State border. Each summer, most of the water in this mineral-rich lake evaporates, leaving behind large concentrations of salt, titanium, calcium, sulfates, and other minerals that form a polka-dot pattern in shades of green, yellow, and brown circles of varying size. The lake is a sacred site to the First Nations of the Okanagan Valley, and the land on which it sits is private property owned by the Indian Affairs Department. You won’t actually be able to get up close to the lake, but you can get a good look from the nearby road.
The Silfa Rift at Thingvellir National Park, Iceland: The shifting of the tectonic plates that fit together like puzzle pieces on the earth’s crust (a.k.a. continental drift) is more visible in southwest Iceland’s Þingvellir National Park than anywhere else. In the park’s ever-widening Almannagjá canyon, you can walk in the seam of the Eurasian and North American plates as they slowly move apart—or you can dive into the crack between continents in the Silfra Rift in Lake Þingvellir. It takes nearly a century for glacier ice to melt and filter through lava into the lake, but once the water gets there, it’s so clear that visibility underwater is nearly 1,000 feet.
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