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
Puget Sound The maximum tidal currents, in the range of 9 to 10 knots, occurs at Deception Pass. The size of Puget Sound's watershed is . "Northern Puget Sound" is frequently considered part of the Puget Sound watershed, which enlarges its size to . The USGS uses the name "Puget Sound" for its hydrologic unit subregion 1711, which includes areas draining to Puget Sound proper as well as the Strait of Juan de Fuca, the Strait of Georgia, and the Fraser River. Significant rivers that drain to "Northern Puget Sound" include the Nooksack, Dungeness, and Elwha Rivers. The Nooksack empties into Bellingham