By Jan Zalasiewicz
Volcanoes can take one by surprise. That was the case with Mount St. Helens, that famously erupted sideways rather than upwards, and it was certainly so, two millennia back, when sleeping Vesuvius awoke to bury Pompeii and many of its citizens. Eyjafjallajokull may not have been quite so dramatic, but its effects, in tearing a large hole in our complex and delicate network of global airline communication, certainly rippled around the world.
To a geologist, the presence of a volcano on Iceland isn’t at all surprising. After all, Iceland is literally, and continuously, splitting apart, as this island sits exactly on the Mid-Atlantic Ridge. That mighty planet-sized fracture is continuously oozing magma, as the Americas pull ever farther apart – by a couple of centimeters a year, maintained for over a hundred million years – from Africa and Europe.