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    Northwest Geology Field Trips, by Dave Tucker, is licensed under a Creative Commons Attribution-Noncommercial- Share Alike 3.0 United States License. You can use what you find here, repost it with attribution to the author, "remix" it for your own purposes, but may not use it with the intent of making money off of it.

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BEACH ERRATICS AT DISCOVERY PARK, SEATTLE

Notes and photos submitted by Sandy Bowman, Seattle.

The erratics in this trip are located on the northern shore of Discovery Park. Map from Seattle Parks Department. Click to enlarge images.

Several erratics dot the cobbly northern beaches of Seattle’s Discovery Park, the site of the former Fort Lawton and just south of Shilshole in Seattle. One Panoramio photo shows a collection of these erratics. (Panoramio is the  website that shows all those photo icons on Google Earth.) Click to go to the Panoramio photo. There are several other photos on Google Earth showing offshore rocks on the beach at the foot of the trail.

The big one at Discovery Park, and Sandy. Photo provided by Sandy Bowman.

The largest of these erratics (47° 40.124’N, 122° 25.210’W) is ~150 yards northeast of where the North Beach Trail joins the Beach Trail in Discovery Park. Sandy Bowman and her friend Consuelo Larrabee were able to walk out to examine it at a -1.7 foot tide, which appears to be plenty low enough for a visit. Judging from barnacles in Sandy’s photos, this rock is about 50% submerged at highest tides. The rock is a smooth, tan rock with glacial striae, especially evident on the water side. If anyone visits this rock, take a stab at identification, or send in some good close up photos showing features. It appears to be rather fine grained. From the solution pockets and color, it might be Chuckanut Formation or another sandstone. Using a tape measure, Sandy and Consuelo determined that the erratic is 15’4″ high.  The circumference is 69.5 ft. You may find a knotted rope hanging down the rock- it is attached to a heavy duty pin with an eye (piton?) but I’d be very leery about trusting any rope that someone else left who knows how long ago.

The shoreward face of the big erratic. S.Bowman photo.

The western-most erratic Sandy described. S. Bowman photo.

Sandy reports that a smaller erratic, covered with algae, barnacles and other marine life lies 130 yards to the north-east. Too much biota to actually get a good view of the boulder’s surface to identify the rock. This one is out of the water at a -2.4 tide.  Our intrepid duo of erratic hunters found that This erratic is 49 ft. around and 8’2″ high.

The immersed erratic and a good samaritan. S. Bowman photo.

There is a smallish rock 100 yards north-west of the big one, but it has always got water around the base.  Not to be defeated by mere seawater, Sandy and Consuelo asked a  party of standup surfboard paddlers who were passing to please measure the height of this rock, and one fellow agreed  to do it.  Using the measuring tape he determined that it was 59″  high and sitting in only 2″ of water.  Sandy told me she found this quite hilarious  as she had hoped to recruit  a kayaker for the job.  If you are out there, thanks to the paddler for graciously cooperating.

Consuelo and the granitic boulder near the foot of the trail. S. Bowman photo.

Finally, another nice erratic, this one granitic, is very near where the North Beach Trail meets the shore at Discovery Park.

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5 Responses

  1. […] new field trip to visit some erratics on the north shore of Discovery Park is here. These were measured and photographed by Sandy Bowman and Consuela Larrabee. I confess I’ve […]

  2. Once you get off the trail, the short hike to the erratics is on slippery, rounded cobbles. Watch where you step when near the big rock because there are anemonies underfoot. Look for starfish clinging to the base of the big rock, too.

    I have offered to lead hikes to this spot. As spring approaches the tides improve each month. If anyone would like to join us, send your email address, and I will send a list of suggested dates and times that look the best.

    • Thanks Sandy, slippery rocks are a good thing to bear in mind. Anyone who wants to take Sandy up on her offer of hikes to these erratics in Spring of 2012, leave a comment (leave your email address out, please). Your email address WILL come to me as moderator, and I’ll pass it along to Sandy for connections.
      Dave Tucker

  3. Here on little Ketron Island (in the southern Sound) we seem to have a lot of small basalt and granitic erratics which have fallen out of heavy clay deposits, some of which are full of gravel. How big does a rock have to be to qualify as an erratic, anyway? Most are on the beach, but there are several up top as well. I wish you would bring a field trip out here–the variety of deposits fascinates me, and I’d like to understand them better. Thanks–

    • Sharon, sorry to take so long to respond. Any rock transported by glacial ice and that is different from the local bedrock is a glacial erratic, even if only the size of a grain of sand.

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