Not too long ago, I posted a shot of "Moon Lake" (aka Penley Lake). When we went flying the other day, we flew over the lake and got to see it from a different perspective.
There isn't much information available on-line about Penley Lake. I found that it is a saline lake, similar to Mono Lake in California and the Great Salt Lake in Utah. There is some kind of brine shrimp that apparently lives or lived in Penley. Only four lakes in Washington state have this kind of shrimp.
There also used to be a sodium sulfate mining operation at Penley in the mid-70's. The deposits were crystalline cylinders, ten to thirty feet in diameter extending straight down. Those mining areas are probably what we are seeing when we drive by it and also from the aerial view. Apparently mud was trapped inside the crystals and made it too costly to mine so the business went belly up. The mining building and hopper are still there along with remnants of the mining operation.