Today’s story is the answer to the November 2024 puzzler.
Towering over the desert in southwestern Libya, the Messak Settafet plateau resembles the wall of a giant fortress, with its dark, erosion-resistant sandstone separating the Ubari Sand Sea to the north and the Marzūq Sand Sea to the south.
The Operational Land Imager-2 (OLI-2) on Landsat 9 captured these images of the plateau on November 17, 2024. The large outcrop of Cretaceous rock features a sharp escarpment on its north side. The cliff, some 300 meters (1,000 feet) high in places, is lined with a thin dark shadow in the top image above. Dark debris from rockfalls is visible to the north. Note that an optical illusion called relief inversion can make high-elevation areas appear low and vice versa when shadows appear on the northern side of a feature.
Although the plateau now receives less than 10 millimeters (0.4 inches) of rain annually, clues in the landscape make clear it was once much wetter. Deeply incised dried stream valleys, or wadis, crisscross the plateau, indicating significant past water flow. The small, bright features scattered across the plateau are sand and silt deposits left where water once pooled.
A dusty road winds its way up the escarpment’s edge near the center of the image and runs along the plateau’s top. The second image above shows where that road leads—to the El-Feel oil field in the middle of the plateau. Secondary roads lead to rows of oil wells, power lines, pipelines, office buildings, and a runway. The faint grid-like pattern of lines around the oil field is a remnant of seismic surveys used to determine the best places to drill. Oil was discovered here in 1997, and the oil field began producing in 2004.
Oil companies are not the first to exploit Messak Settafet’s resources. Archaeologists have unearthed evidence that hominins—a taxonomic group that encompasses Homo sapiens and other extinct species such as Homo neanderthalensis and Homo erectus—have mined the plateau for quartzite to make tools since the Stone Age.
Signs of ancient toolmaking cover much of the plateau’s surface. According to one archaeological survey, people discarded so many stone tools and rock fragments on the plateau over hundreds of thousands of years that roughly 75 artifacts per square meter now carpet the surface. That makes this one of the earliest known examples of hominins modifying an entire landscape, according to the University of Cambridge archaeologists who conducted the survey.
Other signs of ancient activity include the bright spots that dot the image. These areas were likely quarrying pits where people dug up rocks and crafted them into tools, the archaeologists reported. Since these depressions would have retained extra water after rains, they left these sandy and silty deposits. They also likely attracted game. Based on the density of notched “tethering” stone artifacts found within the deposits, they were likely used as hunting and trapping sites.
Archaeologists have also documented large amounts of petroglyphs, cave paintings, and other rock art on and around the plateau, though such works are too small to be seen in these images. For instance, Wadi Mathendous, a prehistoric archaeological site located in the southern part of the plateau, contains engravings of rhinoceroses, crocodiles, hippopotamuses, fighting cats, giraffes, long-horned buffaloes, and elephants. The art is thought to be about 8,000 years old.
NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.
