Puget Sound faults about 1100 years ago (AD 900—930) an earthquake of magnitude 7+ uplifted Restoration Point and Alki Point, dropped West Point (the three white triangles in the Seattle Basin on the map), caused rockslides in the Olympics, landslides into Lake Washington, and a tsunami on Puget Sound. It extends as far east as (and probably terminates at) the Rattlesnake Mountain Fault Zone (RMFZ; the southern extension of the SWIF) near Fall City. This seems geologically reasonable, as both the SWIF and RMFZ appear to be the contact between Tertiary Crescent Formation basement of Puget Sound on the west and the older
Possession Sound Possession Sound Possession Sound is part of Puget Sound, located in the U.S. state of Washington between Whidbey Island and the coastline of Snohomish County approximately between the cities of Everett and Mukilteo. Possession Sound connects the main Puget Sound basin to the south with Saratoga Passage and Port Susan to the north. The Snohomish River flows into Possession Sound at Port Gardner Bay. Gedney Island, also called Hat Island, is located in Possession Sound. Possession Sound was named by George Vancouver. On June 3, 1792, Vancouver landed near the present site of Everett and celebrated the birthday of George