Thursday, August 10, 2017

Double Bluff

I've been slipping. Maybe I was thinking I was going to write something longer, but just didn't seem to get to it. It's summer, after all. But I've had a bunch of pictures from Double Bluff in the queue for more than a month and if I don't do something with them, they'll sit for another month. So I'll post the photos with minimal commentary, hoping it will allow me to move on.

Double Bluff is the distinct light colored cliff you see when you look north up the Sound from the Edmonds ferry. It is a long, straight stretch of high bluffs, oriented perpendicular to the maximum fetch. One of several notable "swash-aligned" bluffs on the Sound.

It's a cross-section of older interglacial fluvial sediments (Whidbey formation) overlain by Vashon advance outwash and till (though that stuff is high above the beach). There's a lot of variability in the sediments - not a terribly simple layer cake. And there are some fascinating deformation features that always capture attention and cause arguments among geologists.


You often see big chunks of peat on the beach - coming out of the Whidbey, so they date back a glacial cycle or two. There's a big boulder at the east end. Chuckanut, apparently, with a big fossil palm frond on top (something like that, I'm no botanist). Started near the equator, traveled to Bellingham, then got delivered to south Whidbey 18,000 years ago. Give or take a few thousand years. It's not going anywhere right now.

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