It is a startling experience to come upon Wedgwood Rock for the first time. More than 19 feet high, the Rock looms up out of a parking strip on 28th Ave NE at the intersection of NE 72nd Street.
How did the Rock get there? Certainly it was not put in place by Albert Balch, the developer who platted the surrounding streets and built the houses!
Research on Wedgwood Rock has been done by Dr. Terry W. Swanson, Department of Geological Sciences and Quaternary Research Center at the University of Washington in Seattle. The term “quaternary” refers to the time period of the most recent Ice Age, when glacial ice extended down into Washington State as far south as Olympia and Spokane.
This glacial movement is called the Cordilleran Ice Sheet, from a Spanish word meaning cord or string of parallel mountains. The geography of the Puget Sound region has a north-south orientation as though long fingers reached out and pressed down into the earth. The “dough” of the land oozed up between the glacial “fingers” to form mountain ranges, and the depressed areas became Puget Sound, lakes and lowlands.
As the Ice Sheet moved down from the north into the Puget Sound area, rocks, sediments and boulders were carried along by the glacier, then were left behind when the ice retreated. Testing done by Dr. Swanson has shown that the mineral composition of Wedgwood Rock matches a site on Mt. Erie, Fidalgo Island, near Anacortes in Skagit County, about 75 miles north of Seattle. Wedgwood Rock is classified as a “glacial erratic,” meaning that its composition does not match its present surroundings and that it was deposited by glacial action (not by Albert Balch!)
“Determination of Cl-36 Production Rates Derived from the Well-Dated Deglaciation Surfaces of Whidbey and Fidalgo Islands, Washington.” Swanson, T.W., and Caffee, Marc L. (1999) Quaternary Research 56, pages 366-382 (2001.)
“How’s This For a Rockin’ House?”, Washington Secretary of State blog, June 2015.
Washington’s Glacial Geology,” Washington State Department of Natural Resources.