Supervolcanic eruptions are very large volcanic eruptions. None have been witnessed in recorded human history, but the evidence of them can be found in the geological record. While infrequent, a supervolcanic eruption is slightly more likely on average than a meteorite impact of comparable size, and they are capable of producing devastating effects. Previous supereruptions have been linked to mass extinction events. If one were to occur in the near future, it is possible it would cause the extinction of the human race.
This essay presents an overview of supervolcanic eruptions. Firstly, what supervolcanoes are, and how they form. The second section details the most recent previous eruptions, and the predictions for future events. The final section contains a discussion of the potential effects of a supervolcanic eruption on local and global scales, with conclusions as to the potential consequences to humans.
What is a Supervolcano?
‘Supervolcano’ is a semi-colloquial term, which is applied to a volcano capable of producing an eruption of magnitude 8 on the Volcano Explosivity Index (VEI) . VEI 8 eruptions are ‘ultra-plinian’ explosive events, characterised by plume heights of over 25 km, and ejected volumes of 1000s of Km3. Since no supervolcanic eruption has been witnessed in human history, the more usual method of defining a supervolcano is by the volume of ejecta deposits from previous eruptions . Ejecta deposits include ash and tephra as well as lavas, and may cover very wide areas. Large igneous provinces (LIPs) also produce such volumes of ejecta, mainly as basaltic lavas, and could therefore also be termed a supervolcano, although they are not explosive.
While Yellowstone may be the most widely known example of a supervolcano (certainly in the minds of the general public, as several documentaries and docu-dramas have been produced about it, e.g. by the BBC and the Discovery Channel , , it is by no means the only one, or even the biggest. Supervolcanic centres have also been identified at Long Valley and Valles Caldera in the USA, Lake Toba, Indonesia, Taupo Volcano, New Zealand, Campi Flegri, Italy and Aira Caldera, Japan, and there are probably many more as yet undefined1.
A particular geology is needed to produce magma chambers capable of explosive supereruptions; the magma must highly viscous, and contain large volumes of dissolved gases so as to be explosive1. This implies silica-rich rhyolitic melts, as their high silica content and low melting temperature makes them more viscous. Most of the known supervolcano sites are within the area of the Pacific Ring of Fire, where the appropriate types of melt are able to be produced- all that is needed for a super-eruption to occur is rapid magma production and a near surface chamber for it to fill.
LIPs require a different type of setting. A large near surface magma chamber is not required, as they continuously erupt basaltic melts derived from the mantle and lower crust. The...