Not sure if people are aware or not, but WA had a super colossal (Mount Mazama type) eruption about where Mount Baker currently sits around a million years ago. It is called the Kulshan Caldera, and they know it buried the Seattle area with a very thick layer of ash. It was close to a glacial maximum so prevailing winds were northerly at the time. The best deposit of ash they found was around Lake Tapps. Very close to here in fact.