Large-scale pyroclastic eruptions (LSPE) can eject 10s-100s km~3 of silicic magma onto the Earth's surface as pumice falls and ignimbrites. The evacuation of voluminous magma from a shallow magma chamber may result in the collapse of a caldera. The frequency of LSPE is "low", with less than 10 eruptions of VEI 7 or more recorded during the last 10,000 years on the Earth. However, LSPE can cause fatal disasters both near the eruption site and at a distance from it, while also seriously impacting the global climate. Pyroclastic fall-outs, ignimbrite flows, and tsunamis during the 1815 eruption of Tambora (Self et al., 1984) and the 1883 eruption of Krakatau (Self and Rampino, 1981) caused destructive damage in areas surrounding the volcanos, although magmas ejected during these eruptions totaled less than 100 km~3. Large volumes of volcanic ash in the atmosphere also resulted in a climatic aberration, known as the Year Without a Summer, in Europe (Robock, 2000). Although these eruptions are the largest known in history, many geological records indicate that some pre-historic LSPE discharged magmas in volumes of an order one or two times larger than these Indonesian examples. Many collapsed calderas surrounded by massive ignimbrite deposits are distributed in subduction zones and continental hot spots. A detailed analysis of deposits surrounding these collapsed caldera reveals that on average more than one mega-eruption VEI ＞ 8 occurs on the Earth every 10,000 years.
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