In the nearby Pacific Ocean, roughly 170 miles (270 km) west of Vashon Island, lies the 700-mile (1,130 km) tectonic boundary known as the Cascadia Subduction Zone, and as such, Vashon Island is one of many areas at risk for earthquakes or related natural disasters. 
On the deck toward Vashon IslandThe northern terminus of the Vashon Highway is the Heights Dock at Point Vashon, serving the state ferry docks at Southworth, and Fauntleroy in West Seattle. The southern terminus of the Vashon Highway is the Tahlequah Ferry Terminal in the Tahlequah neighborhood, connected to the Point Defiance neighborhood of Tacoma by the Point Defiance–Tahlequah ferry. To the west Vashon Island is separated from the Kitsap Peninsula by the Colvos Passage. Vashon, Washington Vashon, Washington (Wikipedia) Vashon is a census-designated place (CDP) in King County, Washington, United States. It covers an island alternately called Vashon Island or Vashon–Maury Island, the largest island in Puget Sound south of Admiralty Inlet. The population was 10,624 at the 2010 census and the size is 36.9 square miles (95.6 km2).