Authors Marie D. Jones & John Savino (who are father & daughter) discussed the history of catastrophic supervolcanoes, and the possible locations where they could occur again. Supervolcanoes are associated with certain calderas around the planet, and when they erupt, the amount of material they spew far surpasses a regular volcano. The study of these massive volcanoes is relatively new, said Salvino, who noted that Cambridge Univ. has found 42 occurrences of them in the last 38 million years. There is a possibility that ones not yet identified could suddenly erupt.
Jones spoke about the Toba supervolcano which erupted 74,000 years ago in Sumatra. The massive amounts of ash brought about an ice age, and nearly made extinct the human/Neanderthal population of about 100,000. Ash, which contains small shards of glass, causes suffocation and internal bleeding, she explained. The remaining population, heavily reduced in numbers, was forced to rapidly differentiate in order to survive, she suggested.
If the Yellowstone caldera erupted (as it did 640,000 years ago) the ash fall would extend all the way to the East Coast, agriculture in the Midwest would be destroyed, transportation would be halted, and up to 2/3 of the population could die, Salvino outlined. Another supervolcano in the U.S. is in Long Valley, CA-- it last erupted some 760,000 years ago, but could be triggered to blow by a giant quake in Southern California, he warned.