A 42-Meter-Deep Lake Once Existed in the Middle of the Arabian Desert, Study Reveals

For a long time, the Rub’ al-Khali—known as “The Empty Quarter”—has been synonymous with extreme aridity, endless dunes, and a relentless climate that makes this vast expanse in the southern Arabian Peninsula one of the most inhospitable regions on Earth. Covering nearly 650,000 square kilometers, primarily within Saudi Arabia, this desert has been viewed as a domain of eternal sands. However, a recent scientific study offers a surprising perspective: several millennia ago, this region was a green and fertile ecosystem, shaped by deep lakes and river systems.

The research, published in the journal Communications Earth & Environment, is the result of collaborative work by internationally renowned universities, including the University of Geneva (UNIGE), King Abdullah University of Science and Technology (KAUST), the California Institute of Technology, Griffith University in Australia, and other institutions from Canada and the United States.

Scientists managed to reconstruct the ancient landscape of the Rub’ al-Khali, providing evidence of the existence of an extinct hydrographic network and a large lake that transformed this desert into a hospitable environment for several millennia.

Desierto Arabia rios lago 42 metros — Geomorphic indicators of breach-driven floods. Credit: A.S. Zaki et al.

A 42-Meter-Deep Lake in the Heart of the Desert

According to the authors, this lake developed during a climatic period known as the Green Arabia, characterized by a regime of intense rainfall that occurred between approximately 11,000 and 5,500 years ago, at the end of the Quaternary period. The rainfall, driven by the northward expansion of the African and Indian monsoons, gave rise to a surprisingly fertile ecosystem.

Researchers estimate that this lake, whose existence is inferred from sediment analysis and terrain features across more than a thousand kilometers, came to cover an area of about 1,100 square kilometers, nearly twice the size of today’s Lake Geneva. It reached a depth of up to 42 meters and, at its peak expansion, overflowed its margins, generating a flood that carved an impressive 150-kilometer-long valley into the desert floor.

Our study highlights not only the existence of this lake but also of a complex fluvial system and a large watershed shaped by water, says Abdallah Zaki, lead author of the research and currently a distinguished postdoctoral researcher at the University of Texas. Zaki emphasizes how these elements construct a paleogeographic narrative that contradicts the current image of the Rub’ al-Khali as a desolate territory.

Arabia desert lake — Inferred palaeolake levels based on geomorphic observations. Credit: A.S. Zaki et al.

The desert’s ecological transformation had significant consequences for the human populations that inhabited or passed through this region. The abundance of water, together with the emergence of savannas and grasslands, fostered the settlement of human groups engaged in hunting, gathering, and later, herding. Archaeological evidence found at various points in the Rub’ al-Khali—including lithic tools and occupation remains—supports this hypothesis.

The formation of this lacustrine and fluvial landscape would have been fundamental in enabling the expansion of nomadic human groups into areas that are now completely uninhabitable, explains Michael Petraglia, professor at the Australian Research Centre for Human Evolution at Griffith University. Nevertheless, this flourishing period was short-lived: about 6,000 years ago, a drastic climatic change marked the end of this humid phase. The rains ceased, the lakes dried up, and the desert regained its dominance, forcing populations to migrate to more hospitable regions.

The findings of this study not only allow for the precise reconstruction of past climatic episodes but also offer a valuable lesson about the close relationship between climate and human dynamics. The cycles of moisture and drought, in this case linked to orbital variations of the Earth, had a direct impact on the landscape and settlement patterns.

Understanding how past climate changes shaped both the physical environment and the distribution of human populations is essential to interpreting today’s challenges, adds Sébastien Castelltort, professor of Earth surface dynamics at UNIGE and co-author of the study. According to him, the story inscribed in the rocks and landforms of the Rub’ al-Khali could serve as a warning about the effects of contemporary climate change.

SOURCES

Université de Genève

Zaki, A.S., Delaunay, A., Baby, G. et al. Monsoonal imprint on late Quaternary landscapes of the Rub’ al Khali Desert. Commun Earth Environ 6, 255 (2025). doi.org/10.1038/s43247-025-02224-1