Who knew that the American Mid-West was the most tornado prone area on the planet? or that Yellowstone was one gigantic calderas? Under "should have known" are the Mississippi flood planes and those of adjoining rivers. As San Francisco grew who really knew the extent of the San Andreas fault system, the Calaveras, the Hayward, the Rogers Creek, San Gregorio and a host of others?

Obvious answer to that, but the European settlers weren't doing a good job of asking the indigenous people about the local conditions.

Don, that was a beautifully written, very tidy and accurate summary of the events at and around Mt. St. Helens. You are to be congratulated! I've been in some geology classes that would have benefited from that succinct approach!

SRS