And then there's the Cascade Volcano arc, many of which I have climbed and can confirm are 'active'. For example, you can see 'bubbling goo' at the Devil's Kitchen near the summit of Mt Hood, and wisps of steam emerging from many of the others. And Mt St Helen's blew up in 1980.
The lahar threat to Seattle from Mt Rainier is particulalry serious, apparently, and there is a similar threat to the Sea to Sky/ Vancouver area from Mt Garibaldi. There is geologic evidence that some of these volcanoes have erupted over a series of years in the past.
From the summit of Mt Douglas in Victoria you have direct line of sight to Mt Baker and Mt Rainier, amongst others. The blast from a big eruption, like Mt St Helens, would hit us pretty full on.
The Cascade Volcanoes
(also known as the Cascade Volcanic Arc
or the Cascade Arc
) are a number of volcanoes
in a volcanic arc
in western North America
, extending from southwestern British Columbia
to Northern California
, a distance of well over 700 miles (1,100 km). The arc formed due to subduction
along the Cascadia subduction zone
. Although taking its name from the Cascade Range
, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes extend north into the Coast Mountains
, past the Fraser River
which is the northward limit of the Cascade Range proper.
Some of the major cities
along the length of the arc include Portland
, and Vancouver
, and the population in the region exceeds 10 million. All could be potentially affected by volcanic activity and great subduction-zone earthquakes
along the arc. Because the population of the Pacific Northwest
is rapidly increasing, the Cascade volcanoes are some of the most dangerous, due to their eruptive history and potential for future eruptions, and because they are underlain by weak, hydrothermally altered volcanic rocks that are susceptible to failure. Consequently, Mount Rainier
is one of the Decade Volcanoes
identified by the International Association of Volcanology and Chemistry of the Earth's Interior
(IAVCEI) as being worthy of particular study, due to the danger it poses to Seattle
. Many large, long-runout landslides originating on Cascade volcanoes have engulfed valleys tens of kilometers from their sources, and some of the areas affected now support large populations.