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Ready for some desert?
Spanning more than 3,000 miles, the Sahara dominates northern African and is the worlds largest desert.
The name may bring to mind an endless wash of sand, but in fact dunes only cover about 15 percent of the desert. Sprawling rock plateaus cover 70 percent; mountains and patchy spots of water account for the rest. Pictured here is a vivid stretch of the desert that spans about 50 kilometers near the Terkezi Oasis in Chad.
The Sahara hosts one of the harshest climates in the world. During the day, the desert can reach temperatures exceeding 130 degrees Fahrenheit, although cool -- even freezing -- nights are common in some months. And the region is positioned in the trade winds belt and is constantly blasted by strong winds from the northeast. Still, more than 2 million people brave living in the harsh Saharan environment.
Just 10,000 years ago, the region was grassy and occupied by mammals like lions and elephants. Now, only two percent of the Sahara is covered by oases-- the only patches of land where crops will grow. Nearly all of the Sahara's population lives in these areas.
The Nile and Niger Rivers, both fed by rains outside the desert, are the region's only waterways. But in some places, water is present at or just below the surface gravel in aquifers that are believed to be filled with water dating from the Pleistocene epoch, when the Sahara was much wetter than it is today.