Mount Rainier

Returning to an ancient topic here on LJ, Wikipedia says Mt Rainier could destroy parts of downtown Seattle with mudflows: http://en.wikipedia.org/wiki/Mount_Rainier

Also there could be tsunamis.

In the past doubt was cast on my contention that nearer-by Tacoma faced a serious risk. I went by the fact that Tacoma was only about 40 miles from the stratovolcano.