| Summary: | In order to classify volcanic eruptions and their potential effects on the atmosphere, Newhall and Self (1982) proposed a scale of explosive magnitude, the Volcanic Explosivity Index (VEI), based mainly on the volume of the erupted products (and the height of the volcanic eruption column). VEI’s range varies from VEI = 0 (for strictly non-explosive eruptions) to VEI = 8 (for explosive eruptions producing ∼1012 m3 bulk volume of tephra). Eruption rates for VEI = 8 eruptions may be greater than 106 m3s−1 (Ninkovich et al., 1978a, 1978b). Eruptions also differ in the amounts of sulphur-rich gases released to form stratospheric aerosols. Therefore, the sulphur content of the magma, the efficiency of degassing, and the heights reached by the eruption column are important factors in the climatic effects of eruptions (Palais and Sigurdsson, 1989; Rampino and Self, 1984). Historic eruptions of VEI ranging from three to six (volume of ejecta from <1 km3 to a few tens of km3) have produced stratospheric aerosol clouds up to a few tens of Mt. These eruptions, including Tambora 1815 and Krakatau 1883, have caused cooling of the Earth’s global climate of a few tenths of a degree Centigrade (Rampino and Self, 1984). The most recent example is the Pinatubo (Philippines) eruption of 1991 (Graf et al., 1993; Hansen et al., 1996). Volcanic super-eruptions are defined as eruptions that are tens to hundreds of times larger than historic eruptions, attaining a VEI of 8 (Mason et al., 2004; Rampino, 2002; Rampino et al., 1988; Sparks et al., 2005). Super-eruptions are usually caldera-forming events and more than twenty super-eruption sites for the last 2 million years have been identified in North America, South America, Italy, Indonesia, the Philippines, Japan, Kamchatka, and New Zealand. No doubt additional super-eruption sites for the last few million years exist (Sparks et al., 2005). The Late Pleistocene eruption of Toba in Sumatra, Indonesia was one of the greatest known volcanic events in the geologic record (Ninkovich et ...
|
|---|