Mt.Mazama ( Crater Lake ) in our county, was estimated over 23,000 feet in elevation. Now the lake level is around 6100 ft, with surrounding peaks around 8k to 9k. Not only did the Mountain loose over ten thousand feet in elevation, it left a hole forming the deepest lake in the U.S.! To put that in perspective, Mount Mitchell in the east, would be but a bump at the base! Mt. Rainer, and Mt.Shasta in all their splender, would also be bumps! Amazing to think about if you've ever seen either of those mountains!
And that was only 7,700 year ago. I would guess that it put out a few emissions when it blew. When you drive from Roseburg to Diamond Lake the road has road cuts through ash deposits that are many feet deep.
