Indeed, people have a mistaken assumption that just because they haven't seen a gargantuan eruption, it won't happen. The problem could arise at El Popo in Mexico, Long Valley, or elsewhere, says Stanley Williams of Arizona State University. Mt. St. Helens, which emitted one cubic kilometer of ash, was the kind of thing that happens every decade or so. Krakatau, which put out about 20 times as much stuff, can happen roughly once every century. But 75,000 years ago, Mt. Toba, also in Indonesia, blew out 3,000 cubic kilometers, an eruption that must have had global climatic implications.
Gargantuan eruptions are rare, but they do happen.
Earth is not, geologically speaking, past its unstable youth. He wrote us a great letter .