A Lake Materializes in the Sahara Desert, Offering a Glimpse Into Africa’s Past

Behold Sebkha el Melah, an ephemeral water successful Algeria, seen from space.

The water formed aft a cyclone walloped parts of bluish Africa successful September, causing immense amounts of rainfall successful the Sahara Desert. And now, it’s helping researchers survey what the Sahara whitethorn person looked similar thousands of years ago—perhaps not a jungle, but a overmuch wetter situation than it is today. Deserts mostly get little than 4 inches of rainfall per year, according to the National Science Foundation, indicating however important an ephemeral water tin beryllium for beingness successful the world’s largest non-polar desert.

You tin spot the portion of Algeria arsenic it appeared successful August and September 2024 below. There is 1 evident dark-green difference. The rainfall came successful earlier September and soaked parts of Morocco, Algeria, Tunisia, and Libya.

The images were taken by the Operational Land Imager-2 (OLI-2) aboard NASA’s Landsat 9. As of past week, the water was astir 33% afloat and covered an country of 74 quadrate miles (191 quadrate kilometers) to a extent of astir 7.2 feet (2.2 meters), according to Moshe Armon, a researcher astatine the Hebrew University of Jerusalem, who reviewed outer images of the lake.

Between 11,000 to 5,000 years ago, a wobble successful Earth’s orbit turned the Sahara into a lusher situation than it is today. It was the African Humid Period, during which past humans painted animals and hunting scenes successful caves and connected rocks crossed now-dried-up swaths of countries including Egypt, Chad, and Sudan. Lake levels crossed bluish Africa were overmuch higher than they are today, and the portion overmuch much verdant. But immoderate geologists reason that clime conditions during that play could not person generated capable rainfall to capable the fig of lakes researchers estimation existed successful what is present the Sahara.

“We’re proposing a 3rd option: that utmost rainfall events, similar the 1 successful September successful the northwestern Sahara, mightiness person been much predominant successful the past,” Armon said successful the Earth Observatory release. “Given however agelong it takes lakes to adust up, these events could person been communal capable to support lakes partially filled implicit agelong periods—even years oregon decades—without predominant rainfall.”

Sebkha el Melah could enactment filled for years. When the salty lakebed filled successful 2008, the h2o didn’t wholly evaporate until 2012, according to a NASA Earth Observatory release. “If we don’t get immoderate much rainfall events,” Armon said, the water “would instrumentality astir a twelvemonth to evaporate completely.”

The summertime tends to beryllium a wetter clip of twelvemonth for the Sahara. Of 38,000 recorded dense precipitation events successful the the desert, astir 30% occurred during the summer, according to an earlier Earth Observatory release.

Eyes from the entity progressively assistance scientists show Earth’s water. In 2022, NASA and France’s CNES launched the Surface Water and Ocean Topography (SWOT) mission, a three-year task that collects information connected h2o measurement and question from orbit. Other spacecraft, similar NASA’s Deep Space Climate Observatory (DSCOVR), keep way of atmospheric clime events.

Whether the water stays filled for months oregon years, it serves arsenic a reminder of however dramatically landscapes—and our knowing of them—can displacement with the planet’s changing climate.