"Washington Park is 4 miles west of downtown Anacortes. In the park, follow the paved loop road counterclockwise using the park map. At West Beach (48.4977N, 122.7012W), one can see the base of the Fidalgo Ophiolite, a sequence of oceanic crust (basalt and overlying sediments) and underlying mantle (serpentinite) once miles below sea level." (see reference)
Description
Ophiolite
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks.