At school, we were all taught that volcanoes—just like the one rumbling away in Iceland—erupt when narrow jets of magma are forced outwards from the core of the Earth. It's a compelling enough story that it's appeared in textbooks for decades—but it's also, apparently, completely wrong. So, the theory we all know and love goes that these long, thin columns of magma—referred to by those in the know as mantle plumes—act a bit like pipes. There's a well of liquid rock close to the core of the Earth and, though we don't quite know how when they formed, these narrow outlets that are 2,000 miles long and less than 200 miles across allow it to vent out to just below the Earth's crust, in the mantle. Where those columns sit in the mantle there are hot spots—and when the Earth's stiff crust fractures slightly, the magma can burst up and out as a volcano. The problem is that such long, thin columns of magma aren't easily explained by basic physics. "Mantle plumes have never had a sound physical or logical basis," explains Don Anderson, Professor of Geophysics at Caltech. "They are akin to Rudyard Kipling's Just So Stories about how giraffes got their long necks." That may sound harsh, but he has evidence to back his point: despite scientists holding that the current volcano theory is accurate, seismological searches for the plumes—the only way to look that deeply into the planet—have yielded no trace of them. More via Gizmodo.