Final answer:
The East African Rift system is slowly separating the Somali Plate from the Nubian Plate, and it is expected to form a new ocean over tens of millions of years. This is comparable to the rate of seafloor spreading observed at mid-ocean ridges, like the mid-Atlantic Ridge.
Step-by-step explanation:
The East African Rift (EAR) system is undergoing a geological process which is expected to result in the formation of a new ocean as the Somali Plate and Nubian Plate continue to diverge. This complex process of continental rifting will, over the course of millions of years, cause a narrow seaway to materialize between the separating plates. This tectonic activity occurs very slowly, and the rift is widening at an average rate somewhat comparable to the spreading seen at mid-ocean ridges.
Analogously, the mid-Atlantic Ridge sees the separation of Europe and North America at about 5 centimeters per year, and with the known global rift lengths and rates, we can estimate that the entire oceanic crust is renewed roughly every 100 million years. Therefore, the full rifting of the East African system into a seaway, being a similar process, might expect to be on a time scale of tens of millions of years into the future. This is estimated from the current rifting rates observed and geological models predicting continental movement.