Susan, All that depends on the type of eruption. When Mt. St. Helens erupted in 1980 it blew out the entire north side of the peak along with over a thousand feet of the top. This sent the flow north, down from the mountain. It really didin't matter if you were in a drainage or not, it took out a considerable area north of the mountain. Considering Mt Rainier is about 10 times larger than St. Helens in land mass, a proportional eruption would take out Seattle, the Olympic Peninsula and make Puget sound look like Spirit Lake does today. Let's hope we never see that happen! I have been on both mountains and actually climbed the Forsythe Glacier in 1976 and 79 and you could tell major differences in the mountain from 76 to 79. The Forsythe glacier was where St Helens blew out, next to the "dog's head". I can also tell you in case you haven't experienced it, that Mt Rainier is a very active volcano, near the rim you can see steam rising from fissures and smell the sulfur very strong and that has been that way for a very long time. It is considered much less active than St Helens and not nearly as likely to erupt. The geologists say we used to have a 19 to 20 thousand foot peak here in Arizona, today it is a 12,000 foot cinder covered half bowl. Who knows what Mother Nature is going to do!