Summary
Highlights
On September 14, 2005, an earthquake in Afar, Ethiopia, was followed by numerous smaller quakes. On September 26, the Dabbahu volcano erupted, creating a 60-kilometer-long and up to eight-meter-wide crack in only ten days. This event, while not causing significant harm, captured the attention of geologists worldwide.
The crack was a symptom of an ongoing seismic shake-up in Africa, where tectonic plates are pulling apart in a process called rifting. A magma plume from deep within the mantle is forcing the African and Arabian plates apart, forming the Great Rift Valley, which stretches over 3000 kilometers.
Scientists have studied the Great Rift Valley since the early 20th century. It is a system of fractures with significant seismic activity, including earthquakes and volcanic eruptions, caused by rising magma. A 2018 study used seismic networks in Ethiopia and Eritrea, recording almost 5,000 earthquakes in two years, and the region has also seen numerous volcanic eruptions.
While rifting is common at the ocean floor, the activity in Africa allows geologists to study the process directly. The 2005 event, where a large section of the rift cracked open all at once, was unexpected, as scientists previously believed such cracks opened incrementally.
Eventually, the Horn of Africa will split from the continental plate, and as many parts of the Great Rift Valley are below sea level, seawater will flood in, creating a new ocean and turning the Horn of Africa into an island. This process has been ongoing for about 30 million years, widening at a rate of a couple of centimeters annually, meaning it will be tens of millions of years before the new ocean fully forms.