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
Environmental issues in Puget Sound Puget Sound would have repercussions for the marine ecosystem as a whole. Eelgrass ("Zostera marina") is an underwater grass that thrives in marine and estuarine water bottoms and spreads through rhizomes, or roots. It has been estimated by the Washington Department of Natural Resources (DNR) that Puget Sound is occupied by approximately of eelgrass. Research has shown that eelgrass beds in Puget Sound can be found in two different habitats: flats, which can be described as either large, shallow bays or small "pocket" beaches, and fringe beds along steep shorelines. Beds of eelgrass provide a vital link in the nearshore