Another southern Jackass erratic sighting

Jackass conglomerate erratic tucked among logs on Camano Island. Photo courtesy Carl Johansen and Frank Alishio. Click to enlarge.

Website subscriber Carl Johansen sends these photos of erratics from the Jackass Formation conglomerate on the beach on the east shore of Camano Island. Unfortunately, the beach is private. Earlier this winter, I asked people to keep their eyes open for any of these distinctive erratics south or west of Whatcom County. This is relevant, as they have been associated only with the last gasp of Pleistocene glacier readvance (the Sumas advance) which barely reached Bellingham and was entirely on land- no glaciomarine component is recognized, so they didn’t flow to their current resting places in calved icebergs. The presence of these distinctive boulders to the south or west negates that theory, put forth by Dr. Don Easterbrook of WWU. Thanks to the reports sent to this website, it looks like these rocks can not be used to delineate the extent of the Sumas readvance.

I’m still hoping for photos of a reported Jackass erratic way down south in Des Moines.

Verified Jackass erratics. Red line marks approx terminus of Sumas readvance.

A smaller Jackass erratic, north of the first. Photo courtesy C. Johansen and F. Alishio.


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