Four days that shook the world.

The argument over what killed the dinosaurs has raged for 25 years, and has polarised into two opposing camps, a meteorite impact, or a prolonged bout of mega-volcanism called a continental flood basalt. But now a team from Geomar, an earth sciences institute at Kiel University in Germany, has come up with a completely new type of geological catastrophe to explain the death of the dinosaurs, as well as three previous mass extinctions. If they are right the culprit was neither a meteorite nor a flood basalt, but a colossal underground explosion called a Verneshot. As yet the idea is in its infancy. But the Verneshot hypothesis has one big advantage over its rivals. It explains a mystery that haunts the debate over mass extinctions, why the extinctions always seem to coincide with both continental flood basalts and meteorite impacts when the odds of these happening simultaneously are vanishingly slim.