The boulder behind Mount Baker Theatre is rather conspicuous. Nestled in the alley behind the building between Commercial and Unity streets, it looks like city planners made a mistake.
But no, this boulder is not an interloper. The outcropping is Chuckanut sandstone, the local geologic formation that makes up the Chuckanuts and the rest of Bellingham’s hills and coastline, running below the buildings and streets of downtown.
The Chuckanut sandstone formation was deposited 50 million years ago, before the formation of the Olympic Mountains. Sediment from the Rocky Mountains and southern British Columbia was carried by rivers until it settled in the then-floodplains of what would become western Washington.
David Tucker, a research associate in the geology department at Western Washington University, wrote about the outcrop in a 2010 blog post. While he hasn’t cracked why it’s there, he’s glad it’s there as a piece of history.
“It’s a remnant of what downtown used to be, and also, for those who care, a reminder of what had to be removed to make downtown flat,” Tucker said. “I see it as a memorial, if you will, to the one-time topography of downtown.”
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