Ancient Drying of the Red Sea: A Prehistoric Desert Reborn
New research reveals an astonishing chapter in Earth’s history: about 6.2 million years ago, the Red Sea basin dried completely, turning a once liquid valley into a vast, salty desert. This extreme environmental event ended with a rapid reflood from the Indian Ocean, leaving a lasting geological imprint that may have sculpted a 200-mile-long submarine canyon on the sea floor. The findings, reported in Communications Earth & Environment, illuminate how dramatically our planet can transform on geologic timescales and how such shifts ripple through ocean connectivity and life.
How the Team Reconstructed a Dried-Up Sea
Led by Tihana Pensa of King Abdullah University of Science and Technology, the researchers pieced together multiple lines of evidence to reconstruct this ancient episode. They studied rock layers beneath the Red Sea and combined this with seismic data that reveals sediment and salt deposition over millions of years. A key clue is an unconformity: a break in the sediment record where older tilted layers are suddenly overlain by a flat, newer layer. This pattern points to a period when the basin dried out, then was covered by fresh material as conditions shifted back to marine life-supporting waters.
To date the desiccation and reflood, the team used radiogenic strontium isotopes, which vary in well-understood ways in seawater over time. They also examined fossil evidence: microfossils largely vanished between 14 million and 6.2 million years ago, consistent with hypersaline or arid conditions, and then reappeared after the flood. The fossil record’s return of sea snails and bivalves around 6.2 million years ago marks the restoration of marine life in the basin.
From Desert to Channel: The Flood That Rewired the Basin
The study proposes that the Indian Ocean breached a volcanic ridge known as the Hanish Sill, a line of volcanic mountains and seamounts that separates the Red Sea from the Gulf of Aden. This breakthrough would have allowed ocean water to surge into the Red Sea relatively quickly—likely in less than 100,000 years—reinstating marine conditions and restarting the basin’s connection to the Indian Ocean. The process was so vigorous that it could have carved a submarine canyon approximately 200 miles long and up to 5 miles wide on the seabed, a feature that persists to the present day.
Implications for Oceanography and Earth History
The event paints a picture of the Red Sea as a dynamic, episodically isolated system. During the salinity crisis, the sea’s salinity soared and life receded; the subsequent reflood reestablished an open ocean gateway to the Indian Ocean, reshaping regional circulation and biodiversity patterns. The researchers estimate the desiccation and refilling occurred during a single, extended phase of drying and a relatively swift, powerful marine influx that reset the basin’s ecological clock. This narrative adds a dramatic data point to debates about how tectonics, sea level changes, and ocean ridges influence regional climates, marine chemistry, and life’s resilience during extreme climatic shifts.
A Longer View: How This Fits Into Our Understanding of Ancient Earth
While the Exodus story has long captured imaginations as a miraculous event, the modern science here tells a namingly older, physically bound tale of the Red Sea’s infancy and subsequent maturation. The Red Sea began forming tens of millions of years earlier as African and Arabian plates pulled apart; the Mediterranean’s historic connection, the early sea’s volcanic and salty phases, and this dramatic desiccation/reflood cycle collectively underscore the region’s role as an arena for dramatic geological and oceanographic change. The discovery also highlights how modern techniques—rock and sediment analysis, seismic stratigraphy, and isotope dating—can unlock deep-time events that altered habitats, steered geochemical cycles, and left lasting features on the ocean floor.
What This Means Today
For scientists, the Red Sea episode provides a natural laboratory for studying how seas respond to extreme climatic stress and tectonic activity. It also cautions about the potential pace of sea-level and salinity fluctuations—factors with contemporary relevance as climate and ocean chemistry continue to evolve. In the end, the ancient desiccation and rapid reflood not only rewrote the Red Sea’s past but left an enduring canyon and a paleoclimatic record that informs how similar processes may unfold in other basins around the world.
