Tassili n’Ajjer, Algeria
Meaning “Plateau of the Rivers” in Berber, Tassili n’Ajjer is a mountain range and vast plateau in southeast Algeria near the border of Libya and Niger. Part of the Sahara Desert, the area has a bone-dry climate with scant rainfall yet does not blend in with Saharan dunes. Instead, the rocky plateau rises above the surrounding sand seas, covering an area of 72,000 square kilometers. Made from multiple Landsat 7 observations from 2000, the image highlights the area’s various rock types. Sand appears in shades of yellow and tan, granite rocks appear brick red, and blue areas are likely salts.
Over billions of years, alternating wet and dry climates have shaped these rocks in multiple ways. Deep ravines are cut into cliff faces along the plateau’s northern margin. The ravines are remnants of ancient rivers that once flowed off the plateau into nearby lakes.
Where those lakes once rippled, winds now sculpt the dunes of giant sand seas. In drier periods, winds eroded the sandstones of
the plateau into “stone forests” and natural rock arches.
Humans have also modified the park’s rocks. Some 15,000 engravings have so far been identified in Tassili n’Ajjer. From about 10,000 B.C.E. to the first few centuries C.E., successive populations also left the remains of homes and burial mounds. Rich in geologic and human history, Tassili n’Ajjer is an UNESCO Biosphere Reserve and World Heritage Site.