It doesn't help that the internet keeps going out, either. But, damn it, I promised you a missive on the bedrock in Seward Park, and that you shall have.
Feast your eyes upon this:
|Feast Your Eyes Upon Actual Bedrock|
Exposures of bedrock in Seattle are fairly rare. Yes, I'm sure anybody who's tried to plant a garden round here has plenty to say about all the damned rocks, but the majority of stuff they're dealing with is glacial till and outwash. It's full of rocks, but it's got a ways to go yet before it becomes actual bedrock. As far as your actual bedrock, though, you're very nearly out of luck.
But thanks to a few earthquakes, you'll get some opportunities. They gave Seattle a high - the Seattle-Bremerton High, in fact. Travel along the high, and you'll catch out some sweet bedrock: the Puget Group in Renton, for instance. But it's the Blakeley Formation we're concerned with here. You can glimpse it in Seward Park. It outcrops along with some Oligocene volcanic rocks at Boeing Field, by itself at Alki Point, and sweeps along the southern bit of Bainbridge Island all the way to Bremerton. They give way after that to nice outcrops of the Crescent Formation from Bremerton on west - the foundations of the area, uplifted by earthquakes and excavated by erosion.
I'll tell you, after encountering very nearly nothing aside from glacial deposits, running into bedrock is pretty damned exciting. Follow me after the fold, and I'll show you (drumroll please) the Blakeley Formation.
|Blakeley Formation Up Close|
Makes the mundane rather magnificent, doesn't that just?
The exposures in Seward Park aren't the best, and most folks pass them right by without a second glance. Understandable, considering:
|Not Putting Itself Forward|
The currents carried bits of land-based trees with them, leaving the sediments peppered with branches and leaves, which became fossilized along with the resident clams and snails. Shore wasn't far, and layers of ash and pumice hint that the Cascade volcanoes were starting life just about then. The subduction zone that gives us so much excitement today provided just as much or even more then. Some of those turbidity currents, in fact, could very well have been caused by the shaking of enormous subduction zone quakes.
The bedding in Seward Park isn't as distinct as it is elsewhere, but you can see it in places:
|Bit o' Sandstone|
|Blakeley Formation Cliff|
The Earth really is an amazing place, and for the geologically-inclined city dweller, there's plenty that shall enthrall you at Seward Park. Hell, we haven't even gotten to the glacial erratics yet.
USGS: Bedrock Geology of Seattle (.pdf)
Northwest Geological Society Field Trip: "The Bedrock of Seattle" (.pdf)
Troost et al: "Geology of Seattle and the Seattle Area, Washington" (.pdf)
Friends of Seward Park: The Geology of Seward Park