Washington's 'forgotten giant' volcano stirs

Volcanoes give you a lot of warning and most in Washington are not located close to major population centers. The one exception is Mount Rainier, which is on the Decade Volcano list. Technically Glacier Peak is a similar distance from Seattle but it is a much smaller volcano and risk of damage is much lower. Historically the Cascade volcanoes only erupt something like 2-3 times per century and most are minor. It isn’t something anyone really worries about. Much higher risk from earthquakes.

I lived down range of Mount St. Helens when it had its major eruption in 1980. It was a regional disaster but the recovery was relatively quick and few people died despite the epic scale of it.

https://en.m.wikipedia.org/wiki/Decade_Volcanoes

Tahoma is the most potentially destructive one. some projections suggest lahar flows reaching downtown Seattle in a worst-case.

https://pubs.usgs.gov/publication/ofr98428

https://www.usgs.gov/media/images/mount-rainier-volcano-haza...

Here in seattle, volcanoes feel like an afterthought attached to the thing that's actually scary, which is the Cascadia Subduction Zone[1]. There's an hour long presentation from CWU [2] that's dry but fascinating, and pretty free of popsci FUD. When the CSZ eventually goes, it's gonna be truly catastrophic.

[1] https://en.wikipedia.org/wiki/Cascadia_subduction_zone

[2] https://www.youtube.com/watch?v=UJ7Qc3bsxjI

Not just modern - [https://en.m.wikipedia.org/wiki/Yellow_journalism]

It's possible, by several mechanisms.

The Mt. Saint Helens eruption was precipitated by a landslide, which reduced pressure over the caldera, leading to a sideways-launched blowout of the volcano itself. That landslide might very well itself have been triggered by an earthquake.

Other possible mechanisms would be either the widening of a magma tube or fissure (permitting higher pressures to the surface), or the introduction of water (crustal or near subsurface) to a magma tube, with the ensuing steam explosion precipitating an eruption.

The role of water in vulcanism is something I'd not been aware of until relatively recently. The Ring of Fire volcanoes form largely around subduction faults, generally inland of where an oceanic plate subducts beneath a continental plate. The oceanic plate carries with it large volumes of seawater, and as that plate itself intersects with (and is absorbed into) the mantle, that incorporated water flashes to steam. The steam pressure itself then plays a major function in generating pressures and driving magma toward the surface. This is also why volcanic eruptions tend to have so much steam as part of the emergent material, so far as I understand.

Another recent eruption in which water (in this case seawater) played a huge role was the 2022 Hunga Tonga–Hunga Haʻapai event, occurring as seawater flooded into a large, shallow caldera, flashing to steam with explosive consequence. Whether or not that event was preciptated by an earthquake again isn't clear, but could be possible. Other mechanisms might have been a cascading failure of the overlying roof of the caldera, with smaller introductions of water expanding access and leading to the catastrophic failure and explosion.

There's some scientific research into the question:

"A review framework of how earthquakes trigger volcanic eruptions" (2021)

<https://www.nature.com/articles/s41467-021-21166-8>

"Can earthquakes trigger volcano eruptions? Here's the science." (2019)

<https://www.nationalgeographic.com/science/article/can-earth...>

Why shouldn't it? I imagine volcanoes as evolving pressure situation slowly tipping towards eruption. Anything that disturbs situation and tips it faster towards eruption, like an earthquake seems as a reasonable assumption. Not that all earthquakes tips it towards it, sometimes maybe it actually relieves the pressure, depends how things move and crack.

Absolutely. Anything from landslides to temporary liquefaction of the ground can weaken the caldera or surrounding vents enough to allow the pressure to force magma to the surface or higher.