Rising hot material upset convection in Earth's core, says new theory

It was a dying on a scale never seen before or since on Earth. The slaughter was everywhere; the fertile ocean and balmy supercontinent Pangea were transformed into killing fields, littered with the bodies of ancient animals. By the time the dust had settled on the Permian-Triassic mass extinction 250 million years ago, 90 percent of life on the planet had been snuffed out.

Now a new theory suggests the catastrophe was set in motion 15 million years earlier, deep in the Earth. On the edge of the molten outer core, a plume of super-hot material began rising through the mantle, upsetting convection in the core and throwing the planet's magnetic field into disarray.

The weakening of Earth's magnetic field exposed the surface to a shower of cosmic radiation, …