Glacial Erratics in Our Neighborhoods

Millions and thousands of years ago, a number of geologic events–volcanic eruptions and glaciers and floods–created the lands of Washington State as we know them today. We’re told that Puget Sound was carved out by glaciers millions of years ago, and the basalt that underlies central and eastern Washington was once molten lava spewed out by–well, there’s controversy over that one–by one giant volcano? by many eruptions?

Last summer I took a course with Road Scholar on the scablands of eastern Washington, studying how giant lakes, damned up by glaciers, broke loose and carved the deep coulees that are there now:  the Grand Coulee where the dam is, Dry Falls once many times greater than Niagara, and many features of the Columbia Gorge. As we toured we found many erratics,  each “a rock somehow transported and dropped some distance from its original home” (David Alt,   Glacial Lake Missoula and Its Humongous Floods, 2001). These rocks were not all pebbles; some were the size of a two story house.

Now I know of two of these rocks, right here in Seattle. When I lived in a neighborhood called Wedgwood Rock, near Eckstein Middle School, there was a big rock up the hill from my house. I knew that if that rock broke loose it would roll down 72nd NE right into my house–of course it would take a humongous earthquake to break it loose. In early Seattle days, people would make an excursion of going out to see Big Rock. You can see it easily. Go to 28th Ave NE, between NE 75th St and Ne 72nd St. The rock is covered with foliage and 28th curves around it. Please don’t bother the neighbors who have the rock in their front yard.

The second rock, you can’t see. Believe. While we were walking down Broadway with our regular walking group, George Guttmann stopped us in front of Casa del Rey Apartments and told us this story: Many years ago, he had been working on a construction project to dig out a street level space under that residential building which at the time was up a small slope next to the sidewalk. As they dug, they found an enormous rock, so big that removing it would be very difficult, and of course blasting it, which was common with big rocks in early Seattle, was out of the question. So they secured the rock with ropes to keep it in place, and dug behind it and under it until they had a gigantic hole. They rolled the rock into the hole and covered it. It’s still there, under the floor. As you step across the level threshold at the retail space under Casa del Rey, think about that rock and ponder–how many big rocks lie under the surface of my city? In my neighborhood? Under my house?

 

 

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One Response to Glacial Erratics in Our Neighborhoods

  1. Sarah Silverman says:

    Fun article

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