Evrim Yazgin
Cosmos science journalist
Researchers have revealed the Arabian Peninsula’s green past. Though a desert today, ancient Arabia had lakes and rivers due to high rainfall.
Geological evidence even points to a mass flooding event which carved out a 150km-long valley.
The research comes out of fieldwork done in the Rub’ al Khali, or “Empty Quarter” – one of the largest and driest deserts in the world. Rub’ al Khali makes up most of the southernmost third of the peninsula.
Results of the expeditions are published in the Communications Earth & Environment journal.
Other recent studies have hinted at Arabia’s wetter past. One published earlier this year shows that the peninsula was dominated by savannah grasslands up until as recently as 200 years ago.
But the new findings go further into the past and reveal an even wetter, greener ancient Arabia.
They show that a massive lake once existed where today there is only desert. The lake was about 1,100km² (110,000 hectares) and 42m deep. Its area is about the same as Lake Michigan-Huron – the second largest lake in the world today after the Caspian Sea.
Radiocarbon dating of samples from around the massive depression that has been left behind reveals the age of the lake.
“Based on a series of ages, it appears the lake peaked about 9,000 years ago during a wet Green Arabia period that extended between 11,000 to 5,500 years ago,” says first author, Abdallah Zaki from the University of Geneva in Switzerland.
“Owing to increased rainfall, the lake eventually breached, causing a great flood and carving out a 150 km–long valley in the desert floor,” adds senior author Sébastien Castelltort, also from the University of Geneva.
Illustrates how precipitation patterns have changed over the 5 past ~24,000 years across the Saharo-Arabian Desert. Credit: Communications Earth & Environment (2025). DOI: 10.1038/s43247-025-02224-1
The lake likely formed due to rains from the African monsoon.
Such rains would have been strong, leaving lasting effects on the landscape and ecosystems. These changes would also have impacted ancient human groups who lived in the area. The region is not far from the “Fertile Crescent” of the Middle East, North Africa and Levant which saw the birth of human agriculture about 12,000 years ago.
“The formation of lake and riverine landscapes, together with grasslands and savanna conditions, would have led to the expansion of hunting and gathering groups and pastoral populations across what is now a dry and barren desert,” says Michael Petraglia, Director of Griffith University’s Australian Research Centre for Human Evolution.
“This is borne out by the presence of abundant archaeological evidence in the Empty Quarter and along its ancient lake and river networks.
“By 6,000 years ago, the Empty Quarter experienced a strong decline in rainfall, which would have created dry, arid conditions, forcing populations to move into more hospitable settings and changing the lifestyle of nomadic populations.”
