Is the West Coast Toast? Let’s Talk Cascadia!

I can stare into the mouth of Mount St. Helens without flinching, begging her to erupt. I can hike up river valleys draining Mount Rainier, and just make a mental note to scramble uphill if it sounds like a mudslide’s coming. I’ve tramped around Mount Baker without once worrying about the fact it’s active. Volcanoes don’t scare me a bit. Okay, I lie, they scare me a wee bit, just enough that I have a healthy respect for their power and refuse to buy property in their hazard zones.

Where I go all white-knuckle and stark terror is on Seattle’s few double-decker roads. Whenever I have to take the southbound I-5 express lanes, I’m staring up at the freeway above, and out toward the Cascadia subduction zone off the coast, and begging it to please oh please not choose this particular instant to rip. Whenever I’m on the coast, the first thing I’m looking for is the quickest route to high ground. See, I know that the Cascadia subduction zone is prone to enormous earthquakes, much like the one that devastated an appreciable chunk of Japan in 2011, and I also know that earthquakes don’t give any warning before they hit. One instant, you’re going about life as usual. The next, the ground is shaking, things are falling, and there’s nothing you can do but ride it out. Well, there’s plenty of safety tips you can follow. But I much prefer volcanoes, which generally give more notice. Also, those generally don’t sink the coastline several feet.

Image shows Lockwood, a man with white hair and beard wearing plaid and denim, standing in the hollow center of a low stump, roots radiating around him through the sand and pools of saltwater.
Lockwood stands on the stump of a gigantic spruce tree at Sunset Bay, Oregon. It was killed more than 1,000 years ago when a massive subduction zone quake dropped the coastline and drowned the forest.

Cascadia terrifies me, people. The idea of it reduces me to a quivering mass of gibbering dread if I allow my thoughts to dwell upon it too long. So I’m glad it’s other people’s jobs to dwell. And they’ve got great news for us! The west coast won’t quite be toast. Our emergency planners are all, we’ve got this.

But if [the recent New Yorker article] has anyone thinking of relocating to another part of the country, you might not want to book the moving van just yet. The region is not “overdue” for a megaquake, geologists at the Earthquake Science Center in Seattle said. It almost certainly won’t be as devastating as portrayed in the article, which suggests everything west of Interstate 5 “will be toast.”

A tsunami will not wipe out Seattle and Tacoma, and buildings constructed since 1995 have strong quake-resistant features. It will be bad, but it won’t catch the Northwest unawares, said Art Frankel, a geologist for the U.S. Geological Survey.

“There’s been lots of preparation done,” he said.

Are you curious about Cascadia? Certain everyone in the Pacific Northwest is gonna die? Then this is the article you should read. The upshot: yep, it’s gonna be very, very bad. But lots of sensible people have been putting a lot of effort into hardening the target and ensuring there’s a solid disaster response plan in place, so it’s not going to be west-coast ending when it happens. We’ll get through this, together.

And hey, the reason I live here is because it’s possible this won’t happen in our lifetimes at all. The megaquake could happen this second. Nope, maybe this second. Okay, maybe it’ll happen tomorrow, or next month, or years from now, but it could also easily not happen for many generations. I’m actually more worried about anthropogenic climate change on a daily basis than I am the Cascadia earthquake, because climate change is happening right now. I mean, our temperate rainforest is on fire right now. A rainforest, people. Burning down. Cascadia will cause us some immediate agony and several years’ worth of expensive rebuilding, but all the carbon we’ve pumped into the atmosphere is going to cause us serious problems for the rest of our lives.

So, yes. We in the Pacific Northwest must prepare just in case the full rip-nine happens. Goodness knows it’s good sense – we’ve got plenty of faults around here other than Cascadia, so we’ve got more than one reason to harden our seismic targets.

Want more Cascadia? The Pacific Northwest Seismic Network has more! If you’re going to be near the University of Oregon tomorrow, you can swing by at 7pm Pacific time for the public forum. It’ll also be streaming live here. For those who loves them their Twitter hashtags, they’ll be tweeting using #‎TheReallyBigOne. And for ongoing adventure, you can explore the subduction zone with Garry Hayes. Come for the gorgeous photos, stay for the exciting geology! You’ll have to endure some geological humor along the way, but you’ll see just why so many millions of people are willing to tolerate the risk – this coast is one of the most beautiful places on earth!

Image is looking downslope at a small mountain lake. In the distance, a pink haze covers row upon row of misty silhouetted mountains.
Tarn Near Sunset, Hurricane Hill, Olympic Mountains


(Originally published at Scientific American/Rosetta Stones)

Is the West Coast Toast? Let’s Talk Cascadia!

9 thoughts on “Is the West Coast Toast? Let’s Talk Cascadia!

  1. 1

    I’m actually more worried about anthropogenic climate change on a daily basis than I am the Cascadia earthquake, because climate change is happening right now. I mean, our temperate rainforest is on fire right now. A rainforest, people. Burning down. Cascadia will cause us some immediate agony and several years’ worth of expensive rebuilding, but all the carbon we’ve pumped into the atmosphere is going to cause us serious problems for the rest of our lives.

    ^ This. So very much this.

    The scale of our Human-Induced Rapid Global Overheating problem and its effects is horrendously under-appreciated in my view. For instance :


    This is a worrying development albeit perhaps a bit technical for folks to follow. The implications of this are really very worrying. Especially when you realise that the climatologists have generally been overly conservative in their estimates and events in reality (eg. Arctic sea ice decline) have frequently been happening much faster than they forecast.

  2. 3

    Let’s suppose you plan on a 10 meter tsunami, and on 34 cm of sea level rise in the next 50 years. You build a 10.34 meter sea wall. (34 cm in 50 years would be about what IPCC AR5 predicts, plus a bit of margin.)

    Now let’s suppose sea level rises much faster than expected, and 50 years down the road, you still have the same sea wall, but sea level has risen 1 meter.

    Then suppose the 10 meter tsunami arrives at that time. 68 cm of water goes over the wall …

    Planning for a tsunami requires, in part, knowing not just how big the tsunami might be, but also, how high the base sea level might be when the tsunami hits.

    That’s important, because buildings and dock structures must be built accordingly, and they have very long lifespans, so it’s necessary to estimate what the sea level is likely to be 30, 50, 70 years into the future.

    But there’s a great deal of uncertainty in how fast fossil fuel driven global warming will make the sea level rise. Largely because governments can’t make up their minds about how much CO2 to emit. But also partly because ice sheet physics is poorly understood.

    Should it rise faster than expected, that could mean a tsunami the area would otherwise be prepared for would be too much.

    For the west coast, I think it’s possible, although difficult, to convince builders of such things to plan on sea level rise near the high range of projections, which is what is necessary.

    But, in the southeast, they face a similar problem with respect to the combination of sea level rise and hurricane storm surge. And in that area, multiple ideological and economic factors overwhelmingly tilt things toward building on the assumption that sea level won’t rise at all, or will be toward the low end of projections.

    Oh, by the way, large hurricanes can cause a local rise in sea level, even as much as 1 meter, even when they pass hundreds of miles off shore …

  3. 6


    Or, you could just realize as I do that it’s unlikely at my age that I’ll be around for either of them. But I do sympathize with those who will have to live through it.

  4. 7

    My hunch is that we should worry more about Cascadia, not because it’s more likely, but because those worries are more likely to lead to doing useful things, like making seawalls large enough and quake-resistant construction. How do you prepare in order to mitigate damage if the Yellowstone supervolcano erupts on the scale some people are worrying about? (I don’t know if an eruption on the scale on the 1980 eruption of Mt. Saint Helens is likely, but Yellowstone is relatively thinly populated; I’d worry more about Mount Rainier.)

  5. 9


    Well, the Yellowstone volcano will let us know it’s going to blow well before it does. And if it does it will probably be orders of magnitude larger than St. Helens ’80. A good part of the northern tier of states may not be habitable for several decades or even centuries.

    However, as you say, Rainier is trouble waiting to happen. It doesn’t even have to have a full scale eruption to cause massive and very deadly damage. All it has to do is heat up enough to melt the glaciers. Bad things will happen. But, again, there will be some warning, so all those people who insisted on buying in the channel of one of the old mud flows might have some warning. I hope.

    Trying to prepare for the Cascade fault to let go is a very good thing, but I am not as sanguine as some that people will be willing to pay for all of that when there is no in-your-face warnings ahead of time.

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