Tuesday, April 10, 2012

Cascades Volcanoes, Sleeping Giants

The entire West Coast of the United States, and Canada are strewn with large stratovolcanoes. From Mt. Shasta, to Mt. St Helens, to Rainier, to Glacier Peak, the West Coast is literally pockmarked with large, explosive, and potentially dangerous volcanoes. The Cascades Volcano Observatory (CVO), and the newly minted California Volcano Observatory (CalVO), are tasked with monitoring these massive volcanoes that are near heavily populated centers. With so many volcanoes on the West Coast, it is a wonder that not a lot of people out here actually realize how volcanically active California, Oregon, and Washington actually are.

The last eruption of a Cascades range volcano was in May 1980 (actually I need to correct this... Mt St Helens erupted from 2006-2009 with a lava dome building event!), when Mt St Helens ended a very long period of dormancy explosively and with little warning (although with today's technology, we may have seen that eruption coming, but we did not have advanced GPS satellite data to measure deformation, nor did we have the types of seismic knowledge that we do today). Mt. St Helens was a beautiful, conical volcano, which until 1980 was a favorite hiking trail and nature preserve. The eruption, many thousands of times more powerful than a nuclear bomb, wiped out and flattened the landscape for tens of miles around the volcano. The only death was a man ironically named Harry Truman, who refused to leave his mountain home. As many as 57 people were killed in the blast, mostly hikers, and a mountain resident named Harry Truman. One persons ordeal was captured on his camcorder as he attempted to escape the ash cloud, but unfortunately he was unsuccessful. Several others survived lahars and thick ashfall, and lived to tell their stories. This eruption could have been much worse if it occurred in nearly any other Cascades range volcano.... and this is the only eruption that is still fresh in the minds of the US.

There were however eruptions of other Cascades volcanoes within the last century. The eruption of Mt Lassen in 1914-1917 was extremely large, and one of the first eruptions to actually be photographed as it exploded. Huge boulders many tons in mass were flung miles from the summit, pyroclastic flows raged down the sides of the mountain, and ash fall was recorded very far from the volcano. There are very few people alive today who would have witnessed this eruption, and the eruption has all but faded from memory.

Before the Lassen eruption, there was the reported eruption of Shasta in the late 18th century. "Shasta's only historical eruption was observed from the ship of the explorer La Perouse off the California coast in 1786." according to the Smithsonian Global Volcanism Project. While this seems like a long time ago, consider how long St. Helens was dormant for. Shasta, like most other volcanoes in the Cascades still experiences periods of heightened seismicity, and weak geothermal action. Shasta will erupt again, but like St. Helens, it is in a lightly populated area (a town called Weed, CA).

But then there are the more dangerous Cascades volcanoes. Like Vesuvius in Italy, Mt Rainier is considered by many scientists to be the most dangerous volcano in the world in regards to the population surrounding it. Not far (40 miles SW) from Tacoma and Seattle Washington, Mt Rainier looms over the landscape and dominates the skyline. This 4,392 meter tall giant of a stratovolcano last erupted some time in the 19th century, according to tree-ring data and analyzed tephra layers.

The threat from this volcano is three-fold. An eruption would melt the glaciers capping the volcano, causing mudslides and lahars. Even if the volcano doesn't erupt, it can collapse due to hydrothermal action 'rotting' the rocks it is made of. This is currently the biggest worry of geologists, and they have a reason to. Flank collapses have reached all the way to the Puget Sound, and that didn't even require an eruption from the massive hulk. Currently, the volcano steams away at the summit, creating a series of steam carved ice caves, a reminder that it is still very much an active volcano. The worst case scenario for this volcano would be a collapse resulting in an eruption, mudflows, pyroclastic flows, and lahars. Much like St Helens, but far larger.

All of these volcanoes have erupted before, and all of them will erupt again. And thankfully, we will probably known at least a few days before that will happen, but there is no predicting structural collapse of these volcanoes, as there are little to no precursor signals that we could be aware of except for GPS measurements, and they would have to be rather frequent. In any case, if you, like me, live on the US West Coast, it's always good to have a disaster plan. We have frequent earthquakes, and will have volcanic eruptions in the future. It's a matter of when, not if. We even have our own supervolcano, the Long Valley caldera, which has erupted after Yellowstone and still shows deformation, seismicity, and hydrothermal action. Its a good thing any new eruption at Long Valley would likely be a small dome building event, or I might just get worried.

The best course of action, especially if you worry about silly things like 2012, etc, is to have a volcano preparedness kit. Breathing masks, batteries, flashlights, LOTS of bottled water, non-perishable food... if you worry about these things, you should have a supply ready to be used in an emergency. The same goes for earthquakes, wildfires, or any other natural disaster our coast has and will experience again. 


  1. Krakatau volcano and Katla action up, your thoughts on this. Thanks.

  2. Anak Krakatau is typically active, still exhibiting a strombolian type cone building phase. Katla is rumbling away with minor quaes every so often, but no eruption is currently imminent.

  3. A volcano might erupt someday. Until then we can go about our lives in peace. Probably won't happen in my lifetime.
    Ah shucks.
    It would be pretty cool if they 'grew' up to great heights of 10 miles prominence.
    Highly unlikely. But we can always hope.

  4. You never know what these volcanoes have in store for us, however the volcano most likely to erupt in the future is most certainly Mt st Helens. Its last eruptive episode ended in 2008 and I suspect it will keep building its dome on and off for some time. I'm currently keeping my eye on Mt Shasta and Hood, as seismicity has been present for a while now. Hood probably won't do any thing for a long time however.

  5. Good article. But there was more than one death associated with Mt. St. Helens ( The camera man who shot the famous blast and several campers in the area were cooked to death ).

  6. Mt St Helens killed 57 people not just Harry Truman

  7. Thanks for the corrections guys, I will update the post!

    1. Can I get the type of breathing masks needed at Home Depot or do I need to order from internet. What type are the best in thick ash situations? Is the a sulfur danger to lungs?

  8. Medical masks are a good, cheap solution and you can certainly get them at home depot, but the best solution would be military surplus breathing masks, as they have more advanced filtration. The dangers of breathing volcanic dust are grave, but usually the ash can be filtered even by breathing through a wet rag. I suggest a gas mask because if you are worried abut poison gas, that is what they are designed for!

  9. Sulfuric gas is deadly if inhaled for too long, it destroys tissue and can cause severe problems even with minimal exposure.

  10. Actually the cameraman who ran away from the blast DID survive. He was a cameraman for Seattle station KOMO TV. He thought, as he said in the video, that he was already dead. It turned pitch black around him as he ran away.


    There was a photographer that did die, and he took still photos of the beginning of the eruption. http://www.petapixel.com/2011/09/07/photographer-died-protecting-his-film-during-the-1980-mt-st-helens-eruption/


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