supervolcanoes-self and blake

supervolcanoes-self and blake - Consequences of Explosive...

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INTRODUCTION The geological record contains evidence of rare, explosive supereruptions that have covered whole continents with volcanic ash and have global long-term recurrence intervals estimated to be in the range of 100,000–200,000 years. Supereruptions have been defined as eruptions yielding in excess of 1 × 10 15 kg of magma (>450 km 3 ; Sparks et al. 2005). Extremely rare examples have produced vast amounts of magma (>1 × 10 16 kg, or 4500 km 3 ). Supereruptions lead to caldera collapse, the formation of huge sheets of pyroclastic flow deposits (ignimbrites), as well as very extensive ash-fall layers and injection of noxious gases into the atmosphere. The effects of a future supereruption will therefore be more violent and damaging than those of the considerably smaller eruptions that society has experienced in historic times. The immediate effects of a supereruption will be almost unimaginably severe. Yet sooner or later, another one will occur, and future societies must be aware of, and prepared for, the consequences. Unlike other extreme natural hazards, there may be some degree of warning of an impending supereruption (Lowenstern and Hurwitz 2008 this issue). Furthermore, supereruptions are potentially long-lasting (continuing at least for many days, and in some cases inter- mittently for weeks to perhaps years; Wilson 2008 this issue), compared to a brief but intense major earthquake or tsunami. The volcanic ash and gases released high into the atmosphere could have severe worldwide effects on climate and weather. Thus, huge explosive eruptions are one of the few natural phenomena that can produce truly global catastrophic effects. They also differ from other hazards (except meteorite impacts) in producing persistent atmospheric effects for several years after the eruption (Rampino 2002). This article presents an assessment of the effects of very large explosive eruptions, which could have con- sequences well beyond those asso- ciated with historic volcanic activity. We begin with brief descriptions of the eruption style and the deposits that are produced, the gases that are released, and how we study them. We then turn to the duration, recurrence, and effects of supererup- tions, including their atmospheric impact, and consider their poten- tial influence on global tempera- ture and weather. Finally, we discuss issues facing society after a supereruption, including potential socio-economic impacts. Predicting all of the effects of supereruptions is problematic because many are outside modern experience. PRODUCTS AND STYLES OF SUPERERUPTIONS We have chosen here to assess the effects of a supereruption in the range of 2000–3000 km 3 of magma [4–7 × 10 15 kg, or Magnitude 8.6–8.8 (Pyle 2000; see Miller and Wark 2008 this issue), equivalent to 5000–8000 km 3 of volcanic ash deposits], an eruption like the largest from the Toba (Indonesia) or Yellowstone (USA) supervolcanoes. All supereruptions are associated with the formation of a
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supervolcanoes-self and blake - Consequences of Explosive...

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