Super eruptions are millions of years in the making - followed by rapid surge

New research suggests that super-eruptions occur when huge accumulations of magma deep in the Earth's crust, formed over millions of years, move rapidly to the surface, disrupting pre-existing rock. Researchers from the Scottish Universities Environmental Research Centre (SUERC) and the University of Bristol led an international team of scientists to make the discovery using a model for crustal flow. The model showed that that pre-existing plutons - a body of intrusive rock made from solidified magma or lava - were formed over a few million years prior to four known gigantic super-eruptions and that the disruption of these plutons by newly emplaced magmas took place extraordinarily rapidly. While the magma supplying super-eruptions takes place over a prolonged period of time, the magma disrupts the crust and then erupts in decades. The findings, published today in Nature, explain these extreme differences in time ranges for magma generation and eruption by flow of hot but solid crust in response to ascent of the magma, accounting for the infrequency of these eruptions and their huge volumes. Professor Steve Sparks of Bristol's School of Earth Sciences said: "The longevity of plutonic and related volcanic systems contrasts with short timescales to assemble shallow magma chambers prior to large-magnitude eruptions of molten rock." Researchers from SUERC used high precision geochronology, a technique to determine the age of minerals using radioactivity, to work out how old crystals within the volcanic rocks are.