How Earthquakes Shaped Seattle’s Landscape

Most people are aware that San Francisco’s north-south trending landscape was shaped by the San Andreas Fault. But who thinks of Seattle that way? Not many. Well, I’m here to tell you otherwise.

As you can see on the map (taken from my novel The Great Seattle Earthquake), the City of Seattle happens to have an earthquake fault running right through it. Fortunately for us, this nasty rip in the fabric of the earth hasn’t let loose a major shakedown in recent history. But the evidence of its past conniptions is there to be seen, and scientists have eyed these landforms with growing concern in recent years. That’s part of what motivated me to write the what-if tale of terror that is The Great Seattle Earthquake. The landscape-altering Seattle Fault is STILL as active as the San Andreas.

Look closely at the map (click or tap it for a larger view). See how Alki Point and Restoration Point on Bainbridge Island seem to point at each other? Of course they do. They are uplifted sections of the Puget Sound seabed, raised in a massive quake that stuck at around 900 AD.

Restoration PtTake a look at these two images of Restoration Point (again, click for a larger view). See those stripes of rock? They might seem reminiscent of geological strata, laid down flat, one on top of the other, then tipped sideways, as is often seen in mountainous regions. But they are not strata. This was a flat portion of the sea floor when the Seattle Fault heaved upward in 900 AD, raising it twenty-five feet into the air. Furthermore, the force of the quake shattered the land in rippling patterns you can still see in these rocks. Wow. What an incredible force it was that moved so much of the earth’s surface up so far, so fast, and did the same on the Alki side of the Sound. Perhaps these ripple marks inspired the legend of A’yahos, the Earthquake Serpent, who Native American storytellers describe as rippling under the surface of the land.

Restoration overheadHave a look at Restoration Point from directly above. Not only are the ripple patterns clear, but notice how some of the strips of rock are jumbled at odd angles. This is the result of what tribal storytellers call “The Day the Rocks Exploded.” And this was long before Europeans arrived with their gunpowder and dynamite. The mind boggles at what the ancient Native Americans saw. Titanic boulders leaping skyward and falling back like scattered hay straws. You can still see these today at Restoration and Alki Points. They form great tide pools where I used to play as a youngster, unperturbed by any notion of their violent origins.

Alki PtThere are other signs of the Seattle Fault’s might and its effect on the area’s inhabitants. At West Point in Discovery Park lie the archeological remnants of Native American camps that span several thousand years of continuous occupation–with a notable hiatus at around 900 AD, when the shell middens and stone tool artifacts disappeared for a century or so following deposition of tidal wave sands several feet thick. That’s right, a tidal wave generated by the earthquake that uplifted Alki and Restoration Points swept over West Point, no doubt drowning any inhabitants and submerging all traces of the encampments there. Furthermore, West Point was once a much larger point, comparable to Alki Point. But the overthrusting of the southern side of the fault drove the lands to the north downward, sinking West Point by several feet, most of it never to rise above tidewater again.

There’s more evidence in our landscape of the rising southern side and sinking northern side of the Fault. Elliott Bay itself is a sunken basin, pushed down and filled with water by the overriding southern heights of West Seattle. And, where is the highest point in all of Seattle? You guessed it, right at the top of West Seattle’s Gatewood Hill.

So next time you’re driving, walking, bussing, training, or biking around our beautiful city, give a thought to how it all came to be. And also give a thought to where you’ll drop, cover, and hang on if a landscape-shaping rupture of the Seattle Fault strikes again.

I have put together a slideshow presentation of this and much more information about the earthquake and tsunami history of the Seattle Area. If you or your group are interested in learning more, you can find further details and contact information HERE.

About Tom Hopp

Thomas P Hopp is a scientist and author living in Seattle. He writes Peyton McKean mystery stories and the Dinosaur Wars science fiction series.
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