Blanchard Mountain was once covered in a massive sandstone deposit called the Chuckanut Formation. Over time, this sandstone unit grew to be more than 10,000 feet thick, trapping many fossils of ancient plant and animal species.

geology of

Oyster Dome (wa100.dnr.wa.gov) Take an invigorating hike up Blanchard Mountain, located south of Lake Samish, to the geologic treasure known as Oyster Dome—a rounded, rocky promontory with spectacular views of the San Juan Islands and the Olympic Mountains. Oyster dome is located in the 4,500-acre Blanchard State Forest, the only place in Washington where the Cascade Mountains meet the Salish Sea.