During class I mentioned the meltdown scenario at Yellowstone National Park — mainly as a way to open the discussion about imagining disaster, but I thought I’d provide a better-sourced article on the subject — lest I mislead too many people!
Says the American Geological Society:
Is it true that the next caldera-forming eruption of Yellowstone is overdue?
No. First of all, one cannot present recurrence intervals based on only two values. It would be statistically meaningless. But for those who insist… let’s do the arithmetic. The three eruptions occurred 2.1 million, 1.3 million and 0.64 million years ago. The two intervals are thus 0.8 and 0.66 million years, averaging to a 0.73 million-year interval. Again, the last eruption was 0.64 million years ago, implying that we are still about 90,000 years away from the time when we might consider calling Yellowstone overdue for another caldera– forming eruption. Nevertheless, we cannot discount the possibility of another such eruption occurring some time in the future, given Yellowstone’s volcanic history and the continued presence of magma beneath the Yellowstone caldera.
ANSWER: Although it is possible, scientists are not convinced that there will ever be another catastrophic eruption at Yellowstone. Given Yellowstone’s past history, the yearly probability of another caldera-forming eruption could be calculated as 1 in 730,000 or 0.00014%. However, this number is based simply on averaging the two intervals between the three major past eruptions at Yellowstone — this is hardly enough to make a critical judgment. This probability is roughly similar to that of a large (1 kilometer) asteroid hitting the Earth. Moreover, catastrophic geologic events are neither regular nor predictable.
QUESTION: What would happen if a “supervolcano” eruption occurred again at Yellowstone?
ANSWER: Such a giant eruption would have regional effects such as falling ash and short- term (years to decades) changes to global climate. The surrounding states of Montana, Idaho, and Wyoming would be affected, as well as other places in the United States and the world. Such eruptions usually form calderas, broad volcanic depressions created as the ground surface collapses as a result of withdrawal of partially molten rock (magma) below. Fortunately, the chances of this sort of eruption at Yellowstone are exceedingly small in the next few thousands of years.