New research reveals multiple explosive events in Yellowstone super-eruptions.

New research suggests that the last super-eruption at Yellowstone volcano, which occurred 631,000 years ago, was not one huge explosion but a series of eruptions or multiple vents spewing volcanic material in rapid succession. Scientists have found four previously unrecognized ignimbrite units at Sour Creek, suggesting at least four eruptive pulses. The finding could give an idea of what to expect if and when Yellowstone does blow.