Sunday, November 25, 2018

Ice Age Boulders in Drayton Harbor

Drayton Harbor is a shallow bay just south of the Canadian border. The City of Blaine is located on its northeast and southwest sides such that the small city has two parts separated by the bay. 

The predominant geology formation around the bay is glacial marine drift. During the last glacial period, glacial ice in this area was on the order of 6,000 feet thick. That mass of ice load pushed the local land surface downward hundreds of feet. During the late stages of the glacial period, the ice thinned and the area was inundated with sea water with ice floating on the surface. As the floating ice melted, sediment would drop out of the ice and land on the seafloor below. The sediment included boulders. Post ice age the land surface rebounded and lifted the former sea floor above sea level. 

Along the south tidal area of Drayton Harbor, boulders that had been dropped out of that ice sheet are scattered across the otherwise muddy tidal flats.    

Drayton Harbor with three glacial erratic boulders 

The tide was high when I stopped at the shore, so many of the tidal boulders were covered. Just about every time I pass by this shore, a great blue heron is using one of the rocks as a resting perch.


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