
David B. Williams discusses Seattle’s surprising geological history. The marled stone behind him is 3.54 billion-year-old gneiss that can be found at the base of the Seattle Exchange Building.
In the past week, Seattle received more bad news about its ill-fated tunnel construction and Bertha, the infamous tunnel-borer that has now been stuck under the city for a year. New reports indicate that Pioneer Square has sunk an inch since Thanksgiving and that a number of historic buildings and roadways are newly compromised by the beleaguered tunnel project. In this guest post, author David B. Williams places these recent developments within the city’s complicated history of reshaping its landscape, arguing that the shifting ground should come as no surprise.
[Crossposted from GeologyWriter.com]
Another day, another problem with Bertha. This time it has to do with cracks and settling and groundwater and planning and fixing and… It’s amazing how many problems that Bertha has had! I want to focus in on the newest map released by the Washington state Department of Transportation (WSDOT). Below is a zoom-in on the map, where I have added an outline of Seattle’s historic shoreline in red. You can clearly see that the areas of greatest settling correspond to where the city was filled in around what is known as Maynard Point (also known as Denny’s Island, but this is a made up name that probably didn’t come into existence till the 1960s). Maynard Point was a mound that rose perhaps 20 feet or so above sea level. It connected to the main part of Seattle by The Neck, a low spot that would periodically be covered by tides, converting the mound into an island. The Point has also been buried by fill. Continue reading