At the end of the Cretaceous era, a large meteorite ploughed into what is now Mexico's Yucatan Peninsula. The collision set off a chain reaction of environmental calamities that likely contributed to the demise of the dinosaurs. New research is now adding to the list of ensuing catastrophes, suggesting the collision cracked our planet's seafloor like an egg, forcing magma to pour out along the ocean's tectonic ridges.