The word supervolcano began as a throwaway line in a 1949 book review
Geologists did not coin supervolcano in a landmark paper. It first appeared in 1949, when F. M. Byers Jr. reviewed a book about Oregon's ancient volcanoes and used it for a vanished giant called Mount Multnomah. Half a century later a BBC documentary turned the word into a household term.
The story starts with a quarrel over Oregon's Three Sisters peaks. In 1925 Edwin T. Hodge argued they were remnants of one huge volcano, Mount Multnomah, blown apart like Mount Mazama. Howel Williams ignored that idea in his 1948 book on the region, and Byers, reviewing it, called Multnomah a supervolcano. The term stayed obscure until the science series Horizon used it in 2000 for eruptions that throw out colossal amounts of material.
Today the label usually means a volcano that has produced an eruption rated 8 on the volcanic explosivity index, the top of the scale, burying the land under more than 1,000 cubic kilometres of debris. Each step on the index means ten times more material. Such blasts empty the magma chamber so fast that the ground above collapses, leaving a broad caldera rather than a cone. They happen when rising magma cannot break through the crust and pools until the pressure finally ruptures it, whether above a hotspot like Yellowstone or at a subduction zone like Toba. At least 60 have been identified, the most recent being New Zealand's Oruanui eruption at Taupō about 25,600 years ago.
A second kind of giant is quieter but vaster. Flood basalts spread lava over millions of cubic kilometres across several million years, forming large igneous provinces. The Siberian Traps erupted around 250 million years ago, alongside the worst mass extinction on record, and the Deccan Traps poured out about 66 million years ago, during the Cretaceous–Paleogene extinction, though an asteroid is considered the main culprit there. Iceland may be such a province still forming; its Laki fissure released some 14 cubic kilometres of lava in 1783 and 1784.
Filmmakers love the idea. A British-Canadian drama in 2005 imagined Yellowstone blowing, and the 2009 disaster movie 2012 made the same eruption one strand of a worldwide cataclysm.
Source: Supervolcano
