Not all volcanic eruptions are created equal, suggests a new report on supervolcanoes, the geologic monsters capable of spewing enough ash, pumice, and lava to create mass extinctions and mini ice ages. Bigger eruptions happen much less frequently than small ones, and different forces drive them upward through the Earth’s crust.
The volcanoes we’re familiar with, which regularly spit up smallish bits of lava – like’s Italy’s Etna and Alaska’s Pavlof – are triggered when semi-molten magma strains its earthen chamber to the point of cracking open, a process known as magma replenishment.
But a supervolcano – a volcano that spews at least 240 cubic miles of deposit, mostly recently during the Middle Paleolithic period – works a bit differently, according to the new findings published in Nature Geoscience. When it bursts open, it’s because low-density magma has slowly accumulated beneath a volcano, pushing its way upward through thicker magma, like a beach ball released from under water. Or, like a lava lamp.