Yellowstone Eruption Possibility? What is the probability of the Yellowstone supervolcano erupting during any given year? I had heard that it erupts once every 100,000 years. Does that mean there is a .001% chance of it erupting during any given year?
1 in 100,000 is an estimate of frequency based on past eruptions which should not be confused with possbility or probability.  It is an oversimplification to state the probability of an eruption as 0.001% chance per year.