Africa is splitting apart at the seams – literally. From the southern tip of the Red Sea southward through Eritrea, Ethiopia, Kenya, Tanzania and Mozambique, the continent is coming unstitched along a zone called the East African Rift.

Like a shirtsleeve tearing under a bulging bicep, the earth's crust rips apart as molten rock from deep down pushes up on the solid surface and stretches it thin – sometimes to its breaking point. Each new slit widens as lava fills the gap from below. This spectacular geologic unravelling, already under way for
millions of years, will be complete when saltwater from the Red Sea floods the massive gash.

This is all happening in north-eastern Ethiopia where one of the earth's driest deserts is making way for a new ocean. This region of the African continent, known to geologists as the Afar Depression, is pulling apart in two directions – a process that is gradually thinning the earth's rocky outer skin. The continental crust under Afar has been thinning out while low hills to the east are all that stops the Red Sea from encroaching.

In 2005, a rift opened up 35 miles (56 kilometres) of land in a mere two days. At the time, geologists suspected this might be the start of a new ocean, but until recently they weren't sure. A new study in Geophysical Research Letters confirms that a volcano called Dabbahu erupted, forcing magma through the rift and ripping apart the land a gaping 20 feet wide.

The research is useful for people who live near such volcanic rifts, but it also shows us something of a process that we can't really see otherwise. How do seas form? It's hard to monitor seafloor ridges because they're, well, under the ocean. The Ethiopian rift offers a potential test case in seafloor spreading and the formation of ocean basins – and this one's above ground and easy to keep tabs on.

Ten million years from now the entire rift may be submerged and a new ocean will be born. Future
generations will look at a globe and see not seven but eight seas – the Arctic, North and South Atlantic, North and South Pacific, Indian and Southern Oceans... and what do you think they'll name the new one?