While pulling out of Friday Harbor on San Juan Island, I had one of those "now I get it" moments.
Turtleback Mountain, Orcas Island
Yes, Turtleback does look like a turtle - particularly when viewed from the San Juan Islands most populous location at Friday Harbor. A big part of Turtleback is owned by San Juan Land Trust and there are public trails with great views and some great prairie ecology. The site also has what I describe as the rarest forest in western Washington: rarest-forest-in-western-Washington. Turtleback lends its name to the oldest rocks in the San Juans - the Turtleback Complex. The complex consists primarily a mix of intrusive rocks that have been interpreted to be the core of a volcanic island arc. Where exactly that island arc originally came from may not be entirely solvable. But the Turtleback is one of several accreted terrains in the San Juans.