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 sea urchins, and sand dollars. Dungeness crabs ("Metacarcinus magister") occur throughout Washington waters, including Puget Sound. Many bivalves occur in Puget Sound, such as Pacific oysters ("Crassostrea gigas") and geoduck clams ("Panopea generosa"). The Olympia oyster ("Ostreola conchaphila"), once common in Puget Sound, was depleted by human activities during the 20th century. There are ongoing efforts to restore Olympia oysters in Puget Sound. There are many seabird species of Puget Sound. Among these are grebes such as the western grebe ("Aechmophorus occidentalis"); loons such as the common loon ("Gavia immer"); auks such as the pigeon guillemot ("Cepphus columba"), rhinoceros auklet