Sunday, December 06, 2015
Keystone Spit is one of the larger barrier beaches in the central Sound, maybe even the largest, depending on how you measure these things. It's a south facing beach that forms a long crescent separating Crockett Lake from the rest of Puget Sound. The lake itself is actually a freshwater (maybe a little brackish in places) lagoon.
The well-sorted gravel results in a very steep beach. Breaking waves disappear into the permeable gravel with a whoosh, followed by the rattle of gravel rolling back down the beachface. Storms pile gravel into high storm berms. And as should be expected of any large south-facing beach on Puget Sound, this one collects logs, lots and lots of them, along with plastic and styrofoam and anything else that floats.
Keystone Spit is a beneficiary of large amounts of sediment converge from two different directions -- and that then have no where else to go. Sand and gravel deposited by landslides in the Ledgewood area (Ledgewood 2013) probably ends up here. And sediment from farther north on the island (see subsequent posts from Ebey's Landing) is transported southward around Admiralty Head. This material is held up briefly by Keystone Harbor at the west end of the spit, but is eventually bypassed (Keystone 2012) and gets blended on this beach with the gravel from the south.
A couple of ponds mark borrow pits form when gravel was removed from the spit decades ago. The two concrete posts were associated with a small building (Navy, I think) that was removed in the last couple of years, but I'm not sure just how they functioned.