An international team of geologists has uncovered that the ancient predecessors of the Euphrates River did not flow into today’s Persian Gulf but instead emptied into a partially dried-up Mediterranean Sea approximately 5.35 million years ago, according to research published in Nature Geoscience on June 1.
The Euphrates, one of the world’s largest rivers in Western Asia with a length of about 3,000 kilometers, is believed to have formed roughly 10 million years ago during the Late Miocene epoch. Ancient Sumerian myths attributed its origin to Enki, the god of wisdom.
Using seismic exploration and topographic data, scientists from the United States, Great Britain, and France linked two sedimentary formations—Khandere and Nahr Menashe—to the ancestors of the modern river. The researchers named them the Great Karasu and Great Murat, drawing a parallel with the current Euphrates’ primary tributaries.
During the Messinian salt crisis—a period when the Mediterranean Sea was drastically shrinking and its water level dropped by 1.7 to 2.1 kilometers—both rivers flowed from the Anatolian Highlands toward the southwest, transporting vast quantities of precipitation into the drying basin.
“The results indicate that the modern Euphrates originated as two distinct river systems that briefly entered a marine environment, traversed four tectonic plates, merged, and ultimately began flowing into the Persian Gulf,” the study states.
Tectonic activity played a critical role in reshaping the rivers’ paths. Approximately 3.6 million years ago, reactivation of the East Anatolian Fault redirected the Great Murat toward the Arabian Plate. By about 2.8 million years ago, the Great Karasu joined it. The Euphrates finally adopted its current form around 1.6 million years ago.
The researchers also note that megaflows during the breakthrough of blocked mountain lakes likely triggered the formation of sedimentary deltas—a process comparable to hypothetical events on ancient Mars.
Probabilistic modeling reveals that during the Messinian crisis, the combined water flow in the Great Karasu and Great Murat surpassed the total discharge of today’s Tigris, Euphrates, and Nile rivers—even though their drainage basins covered less than one-tenth the area. This suggests significantly higher precipitation levels in the region about six million years ago.
