Watched I-90 Rocks: Geology of the Puget Sound

Watched Geology of Seattle and the Puget Sound by hugefloods from

The hills and lakes of Seattle, Washington are a direct result of multiple Puget Lobe advances during the Ice Age. Beneath the drumlins, outwash, glacial troughs, and scattered glacial erratics lies the Seattle Fault, an active fault which has produced numerous magnitude 6 or higher earthquakes since the Ice Age.

Interstate 90 exposes much of this geology in its first few miles heading east from downtown. The freeway begins on old tidelands that were filled by early residents of Seattle. Hills composed of soft glacial deposits were moved and dumped into Elliot Bay to make new land for a growing city. Today’s SODO district – including stadiums for the Seattle Seahawks and Seattle Mariners – sits on filled tidelands that are especially prone to seismic shaking during the next big earthquake in the Puget Sound.

Tom Foster ( and Nick Zentner (Central Washington University) have been hiking together in Washington for years. ’Geology of Seattle’ is part of an “I-90 Rocks” video series.

Learned the reason everything in the Puget Sound is so north-south oriented: it’s a field of drumlins formed by the glaciers that at one point lay 3000′ thick over Seattle!

I always figured our yard was an old stream bed because of all the rocks but it’s totally glacial till 😂

It’s shocking how much of Seattle proper is built on fill 😳 South Seattle west of I-5! So, like, a lot (including the stadiums). As a born and raised Californian with a deeply rooted awareness of earthquake danger, my mind turns to liquifaction 😳

So much interesting geology in Washington! Snoqualmie Pass is different from most mountain passes, lacking a steep cirque on either side because of ice age glaciers weighing down the peaks (probably also explains why it’s a relatively low pass at 3000′). And a diverse blend of rocks – sandstone uplifted, magma chambers exposed, volcanic deposits, lots of cool stuff.


Earthquake Safety Retrofits

Bookmarked Seismic Solutions (Simpson Strong-Tie Site)

Seismic Solutions | Simpson Strong-Tie

Washington resources: – online classes

Growing up in California, earthquakes weigh on me. I was really little for the Loma Prieta earthquake but I remember taking my duplos outside to wait for aftershocks.

My dad saw our crawl space and was horrified by the lack of earthquake safety, so it’s been on my mental to-do list to have a seismic retrofit done, but it keeps dropping to the bottom of the list.

We watched part of a documentary about The Big One that we’re due for in my lifetime. Living on a subduction zone is mildly disconcerting. Nothing much for a thousand years, then a magnitude 9 earthquake. I think winter storms have been a preview that we’re not ready for a disaster like that.

Would a seismic retrofit really protect us from a quake that big? Maybe…


Watched X-ray Earth Pacific Northwest Earthquakes

Watched X-Ray Earth from National Geographic – Videos, TV Shows & Photos – International

Beneath our feet, under trillions of tons of rock, lurk astonishing and deadly secrets. Earthquakes, tsunamis, volcanic eruptions are all driven by hidden forces deep inside our planet. Now, using the latest scientific data from sensors and surface scans, we can x-ray the earth to reveal the dangers locked inside our planet. Using thousands of sensors and state of the art surface scan information, for the first time, we can create x-rays of the deep interior of our planet.

Hit a little close to home. Being raised in California I know a fair bit about earthquakes but learned a few new things about the Cascadia subduction zone. DH bailed on the ending because it was getting pretty doom and gloom.