The landscape of Afar in Ethiopia (pictured) is tortured, because underlying tectonic plates are pulling apart from each other. Such rifting can lead to continental break-up, and is often accompanied by voluminous magmatism — the production of large amounts of melt. In this issue, Ferguson et al. report the cause of this magmatism in Afar (D. J. Ferguson et al. Nature 490, 70–73; 2013).

The authors developed a model of magmatism in the region using geochemical data from lavas that erupted along the rift. They conclude that melting is generated at great depths — 80 kilometres or more — and is driven by an unusually hot region of the mantle.


Using another model, Ferguson and colleagues tracked the development of melting at the rift, and found that thinning of the tectonic plate over the past 30 million years has been much less than expected. This suggests that an abrupt phase of plate thinning during the final stages of break-up would be required for an ocean basin to form in Afar.