Tuesday, May 09, 2017

Thompson Spit

The Miller Peninsula, on the north side of the Olympic Peninsula, lies between Discovery Bay on the east and Sequim Bay on the west. Diamond Point is the cuspate foreland that marks the northeast corner and the entrance to Discovery Bay. Travis Spit extends from the northwest corner across the mouth of Sequim Bay. In between is about 5 miles of gravel and cobble beach, backed by steep bluffs.


The one exception to this long stretch of bluffs is Thompson Spit, located near the eastern end. The spit is a looped barrier - basically a spit that extends out from the coast and then reconnects farther down the shore (in this case, west to east, which is consistent with what we expect of longshore transport here). They're rarely symmetric and this one is no exception. Their updrift ends are often tangent to the adjacent bluff - as if the beach reached a sharp bend in the coastline but couldn't turn fast enough. The downdrift ends tend to merge back to the coastline asymptotically. If there is a tidal inlet, it's usually near this downdrift end (that's not the case at here, which just suggests a more complex geologic or historic story that I don't know).

The berm on the western end is low and narrow and there was evidence of overwash. The lagoon was draining through a shallow inlet and the beach in front of the inlet was marked by several organic ledges (the upper looked more like sawdust - perhaps evidence of some human history?) - which is typical where a barrier beach has migrated landward, exposing old marsh and lagoon sediments. The central point of the spit is marked by a large mound that appears to be fill - was there an old cabin or small mill here once?

This may have been referred to as Deadman's Spit at one point - the dead man being a guy named Thompson in the 1860s. But that may be reading too much into a local history I found online (Diamond Point history).

I'd like to come back and explore more sometime - lots of unanswered questions. But only the western portion of the spit is in the State Park and I'm not sure how welcoming the owners of the eastern half are likely to be.

Looped barriers are common on Puget Sound - here are a few we've visited before:
Perego's Lagoon: December 2015
Cama Beach: April 2017 (and many previous)
Kayak Point: January 2009

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