The Red Sea went completely dry before being flooded by the Indian Ocean

Scientists at King Abdullah University of Science and Technology (KAUST) have provided conclusive evidence that the Red Sea completely dried out about 6.2 million years ago, before being suddenly refilled by a catastrophic flood from the Indian Ocean. The findings put a definitive time on a dramatic event that changed the Red Sea. 

Using seismic imaging, microfossil evidence, and geochemical dating techniques, the KAUST researchers showed that a massive change happened in about 100 000 years – a blink of an eye for a major geological event. The Red Sea went from connecting with the Mediterranean Sea to an empty, salt-filled basin. Then, a massive flood burst through volcanic barriers to open the Bab el-Mandab strait and reconnect the Red Sea with the world’s oceans. 

“Our findings show that the Red Sea basin records one of the most extreme environmental events on Earth, when it dried out completely and was then suddenly reflooded about 6.2 million years ago,” said lead author Dr. Tihana Pensa of KAUST. “The flood transformed the basin, restored marine conditions, and established the Red Sea’s lasting connection to the Indian Ocean.” 

How the Indian Ocean Flooded the Red Sea 

The Red Sea was initially connected from the north to the Mediterranean through a shallow sill. This connection was severed, drying the Red Sea into a barren salt desert. In the south of the Red Sea, near the Hanish Islands, a volcanic ridge separated the sea from the Indian Ocean. But around 6.2 million years ago, seawater from the Indian Ocean surged across this barrier in a catastrophic flood. The torrent carved a 320-kilometer-long submarine canyon that is still visible today on the seafloor. The flood rapidly refilled the basin, drowning the salt flats and restoring normal marine conditions in less than 100 000 years. This event happened nearly a million years before the Mediterranean was refilled by the famous Zanclean flood, giving the Red Sea a unique story of rebirth. 

Why the Red Sea Matters Geologically 

The Red Sea formed by separation of the Arabian Plate from the African Plate beginning 30 million years ago. Initially, the sea was a narrow rift valley filled with lakes, then became a wider gulf when it was flooded from the Mediterranean 23 million years ago. Marine life thrived initially, as seen by the fossil reefs along the northern coast near Duba and Umlujj. However, evaporation and poor seawater circulation increased salinity, causing the extinction of marine life between 15 and 6 million years ago. Additionally, the basin was filled with layers of salt and gypsum. This culminated in complete desiccation of the Red Sea. The catastrophic flood from the Indian Ocean restored marine life in the Red, which persists in the coral reefs to the present. 

All in all, the Red Sea is a natural laboratory for understanding how oceans are born, how salt giants accumulate, and how climate and tectonics interact over millions of years. The discovery highlights how closely the Red Sea’s history is linked with global ocean change. It also shows that the region has experienced environmental extremes before, only to return as a thriving marine ecosystem. 

“This paper adds to our knowledge about the processes that form and expand oceans on Earth. It also maintains KAUST’s leading position in Red Sea research,” said co-author KAUST Professor Abdulkader Al Afifi.