Tuesday, May 29, 2012

Agate Pass, Bainbridge Island

I had a recent down slope traverse between recent landslides on a clayey slope on Bainbridge Island. This traverse entailed sliding from tree to tree down the slope. Better for slugs than people, but at least this slope had minimal blackberry brush and I guess I could claim it is one of my skill sets. 

Recent slide scarp

Dense clay on slide area

Random cobble embedded within the clay

I noted a few random cobbles embedded within the clay indicative of the unit being an ice margin lake. When glacial ice blocked off the north end of Puget Sound approximately 18,000 years ago, a lake formed over the Puget lowlands. In the Seattle area, the lake deposits associated with this lake are referred to as the Lawton Clays. Haugerud (2005) has utilized the Lawton Clay in his mapping of units on Bainbridge Island. based on what I observed this is a very reasonable interpretation.

I was not real keen on crawling back up the slippery steep slope and there were a couple of pitches I was not sure I wanted to try again with my shovel in hand so I set my sites on Agate Pass and using the bridge over the pass as a possible easy route back up.

Bridge at Agate Pass with casino on opposite shore

The Port Madison Indian Reservation is on the opposite shore from Bainbridge Island, and like many reservations in Washington has casino and hotel. Agate Pass itself had a favorable south wind and a northward tidal current at the time of my visit allowing for an easy passage for north bond sail boats. 
Agate Pass looking west

The route back up off the shore was an easy climb under the bridge span. And I got to see a bit more geology this way.

The east shore of the pass is a platform beach with a bare covering of sand and gravel over glacial drift.

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