How did the Red Sea form between Africa and Arabia?

The Red Sea formed as a result of tectonic divergence between the African and Arabian plates, creating a large rift valley in the continental crust. This process is part of a complex rift system that includes the East African Rift System and the Gulf of Aden.1

The development of the sea occurred in two primary phases:
* Initial Phase: The separation of Africa and Arabia began approximately 55 million years ago. The Gulf of Suez opened about 30 million years ago, followed by the northern Red Sea roughly 20 million years ago. During the late Oligocene and early Miocene, a fault-bounded trough formed, allowing the Mediterranean Sea to flood the rift.12
* Second Phase: Beginning 3 to 4 million years ago, this phase created the trough in the Gulf of Aqaba and the southern Red Sea. During this time, the subsidence of an isthmus between Djibouti and Aden allowed the Indian Ocean to flow into the basin.12

This tectonic movement continues today at a rate of approximately 0.6 inches per year, evidenced by ongoing seismic activity and volcanism.1