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Fantastic Erratic, Cougar Mountain Regional Park, King County

Submitted by Greg Kulseth

June 30, 2011

Greg at the Fantastic Erratic. Click to enlarge. Photo courtesy G. Kulseth

The “Fantastic Erratic” is a fern-draped rock is located about 1 mile up the Bear Ridge Trail in Cougar Mountain Regional Park (King County Park System).

Getting there:Take I-90 east from Seattle to Exit 15. Take 17th Ave NW south (turns into Renton-Issaquah Road

Fantastic Erratic is in the woods. Help! Green hell! Google Earth is no help.

SE) about 1.5 miles to the Bear Ridge Trailhead on the right (west) side of the road. Hike about 1 mile up the trail, much of which appears to be the remains of a lateral moraine, to the erratic, which appears to be around 15 feet high and is marked with a sign that says “Fantastic Erratic”. The GPS location is 47.530237 N 122.080479 W.

According to Greg, this rock does not appear to be granitic. There is no closeup photo or further geologic description available at this time. Hopefully a reader can attend to this by determining the rock type (if you are able) or sending a good quality photo to:

send email here

A web search for “Fantastic Erratic” will turn up a geocache, a video (the trail sign, not the rock) and several other photos but none as good as the ones Greg sends.

On the PDF map of the Cougar Mountain Park, the “Fantastic Erratic large glacial boulder”, is identified on the east edge of the map. A 7 MB pdf map file is here:


A much larger (20 MB) color map is here:


2 Responses

  1. […] there are strange and curious little anomalies like Fantastic Erratic, an enormous boulder smack in the middle of the woods—presumably dragged into place eons ago by […]

  2. […] the “Fantastic Erratic,” a fern-draped boulder on Bear Ridge Trail in Cougar Mountain. A bit further up the trail is […]

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