I am near Portland Oregon, 100 km southwest of Washington's Mount Saint Helens, which in 1980 blew about 3 cubic kilometers of rock and incandescent gas as high as the stratosphere. A bit more frisky than Eyjafjallajökull in 2010, though fortunately our ash plumes did not cross major air routes. That series of eruptions deposited a centimeter of ash on my apartment.KarenRei wrote:However, given that the volcano is erupting lava, it's unlikely to be Washington. Do you get any lava eruptions there?
Saint Helens is active, and is rebuilding inside the huge crater left by the blast. No incandescent liquid lava visible - it pushes up slowly but persistently under the pile of rocks and ash that rained down from the first explosion. As it builds and consolidates, liquid lava may break the surface.
The lava around here is pahoehoe, like that currently oozing out of Mauna Kea in Hawaii. Large flows make lava tubes, and there are many on the south flank of Mount Saint Helens and Mount Adams - some are larger than rail tunnels inside. So, no rivers of incandescent lava recently, though lava vented from sides of Saint Helens and made lava tubes as recently as 400 years ago.
There are three dormant volcanic vents within the city of Portland, and sulfur fumes have vented from Mount Tabor in recent years. My house is on a ridge running down from the cindercones on the west side of Portland. Old sediment-filled lava tubes run 100 meters below me. Deep below, the Juan De Fuca plate grinds eastward underneath the North American plate, pulling down water-laden seafloor sediment that melts and expands and eventually finds its way back to the surface along the line of volcanos that make the Cascade mountain range.
The question is not if the volcanos will go again, but when. Portland and southwest Washington could be under 30 meters of lava 10,000 years from now, or 10 years from now. Portland is more likely to be leveled by a moment magnitude 10 earthquake first; these happen about every 300 years, and the tsunami from the 1700 AD earthquake killed people in Japan. Geology does the darndest things. As disasters go, at least we do not have to eat lutefisk.