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  • MOUNT BAKER: Eruptive history, hazards, research.

    Visit Mount Baker Volcano Research Center websites Main website and the blog These are no longer actively maintained but are still good references [DT, April, 2020]
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    This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
    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.

    EDUCATORS: Please feel free to use anything you find here that is useful to your mission educating people about Earth science. E-mail me if it would help to have a larger or higher-resolution version of any of the images. tuckerd at geol dot wwu dot edu

Dickerman Mountain geology guide posted

Hi friends! Remember me?

P1030402 mark

Stacked lava flows below the summit of  Dickerman Mountain. Click to enlarge.

A new geology field guide has been posted on this website. This one gives you something to do while you huff and puff your way up through the 45-million-year-old Barlow Pass Volcanics on the Dickerman Mountain Trail. The mountain rises above the South Fork Stillaguamish Valley, and is reached by the Mountain Loop Highway east of Verlot and Granite Falls. The trail is a steep mother, gaining 4000′ in just over 4 miles. The summit gives spectacular views into the Monte Cristo area peaks and Glacier Peak. I hiked the trail on July 3, 2016 with my friends Charlie and Scott Linneman. The views weren’t great due to clouds, but I got to examine some North Cascades rocks I wasn’t familiar with. The story is online, here.

Guided geology field trip to Schreibers Meadow cinder cone

The NCI field trip to Schreibers Meadow cinder cone is booked up.


Dave Tucker

Mount Baker Volcano Research Center subscription website

The bushwack up to the cinder cone rim. Click to enlarge. The bushwack up to the cinder cone rim. Click to enlarge.

North Cascades Institute is offering a guided geology field trip to the 9500-year-old Schreibers Meadow cinder cone on the south flank of Mount Baker. The trip will be led by MBVRC’s Dave Tucker. The date is July 6th, and costs $95. Register at the NCI website:


The Schreibers cone is the only one in the Mount Baker volcanic field. It is located in old growth forest at 3500 feet elevation in Schreibers Meadow, just 1/2 mile from the end of the road. The trip will walk a short distance along the Park Butte/Railroad Grade trail, then veer off cross country (huckleberry meadow and some ponds) before the final 130′ climb up a steep forested slope to the crater rim. We’ll walk down to the soggy shores of the two crater lakes, and up to the opposite rim. After…

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Giant Cairn in the Wharf Roundabout, Bellingham Washington

Some guy in a funny hat looks at the giant rock cairn in the roundabout. Hey! Wait I think I know that guy! Where're the cats?

Some guy in a funny hat looks at the giant rock cairn in the roundabout. Hey! Wait I think I know that guy! Where are the cats?

A number of Bellingham people have written me for a geological description of the 12′ rock cairn in the middle of the new roundabout at Wharf, State, Forest, and Boulevard. An article appeared in Dean Kahn’s Dec. 22 column in the Bellingham Herald; prior to that, I sent a photo and a brief notice to David B. Williams’ GeologyWriter.com blog. The 13-foot-tall stack of 4 boulders sits in the new roundabout at the south edge of downtown Bellingham. Shrubs have been planted around the cairn, but they are still spindly and short so it is still approachable on foot.


The lowest two, and the uppermost, boulders are dunite from the Olivine Corporation’s Sven Larsen Quarry on the north flank of the Twin Sisters Range west of Mount Baker. (48° 44.640′ N , 122° 0.345′ W.) The stone second from the top is serpentinite. It also came from the quarry. The stones were supplied by Princess Jade, a stone-supply company in Everson Washington. Get up close enough to see the smooth highlights on the serpentinite boulder, polished by Princess Jade prior to installation. The 8-mile-long Twin Sisters Range is a narrow slab of mantle dunite, among the largest in the world, faulted upward into the crust during plate collisions, and exposed by erosion.

The dunite boulders feature tiny black chromite crystals surrounded by olivine.

The dunite boulders feature tiny black chromite crystals surrounded by olivine.

Dunite is a dense crystalline rock. By definition, it consists of around 90% olivine crystals; the remainderis pyroxene and chromite. Dunite is believed to be the residue left behind when basaltic magma forms in the mantle, typically deep in subduction zones. Water carried into the mantle via the subducted ocean plate (the ‘slab’) lowers the melting point of the mantle, generating basaltic melt. The lower density basalt magma rises upward through the mantle taking lighter minerals such as silica along for the ride, leaving behind the denser minerals – olivine and pyroxene. Serpentinite is a low-temperature metamorphic rock formed when water enters the molecular structure of ultramafic rocks such as dunite. Hydrated olivine becomes a different mineral, serpentine.

Polished highlights on the softer serpentinite boulder.

Polished highlights on the softer serpentinite boulder.

The City of Bellingham had a choice of two designs incorporating the large boulders. The stack won out over the other possibility, scattering the rocks on the ground. Bellingham’s mayor, Kelli Linville, said “The landscaping we chose reflects the natural beauty of our area. Since cairns are traditionally used to help people find their way, a cairn is an appropriate part of the landscape at this important crossroads in our community.” (Bellingham Herald, Dec 22, 2013). According to Sam Shipp, the project engineer at Bellingham’s Public Works Department, the cairn option helps protect drivers from the glare from oncoming headlights and directs drivers’ vision toward other vehicles approaching from the left inside the roundabout, as well as providing an aesthetic component.

Dunite is very dense, about 3.3 grams/cubic cm. Serpentinite is around 2.7 g/cc. Contrast that with basalt (2.8-3 g/cc), andesite (2.5-2.8) and granite 2.6-2.7). The largest stone, the one on the bottom, weighs around 15.5 tons. The two in the middle are 8.5 tons each, and the little one on top is about 3.5 tons. The four stones are held upright by a central steel rod sunk into a concrete base. The project cost $75,000.

OK. “NAME THE STACK” CONTEST! Let’s name that stack o’ rocks! Submit your suggestions via comment and I’ll forward them to the City via my very special confidential connection.

I ar a perfeshunal jolojy riter!

Dear friends,

This photo appeared on teh 'meteor craters' post on Ask Dr. Rock.

This photo appeared on teh ‘meteor craters’ post on Ask Dr. Rock.

I have been hired by an acquaintence to produce a geology blog twice a month. It is called ‘Ask Doctor Rock’ and can be found at http://askdoc-rock.blogspot.com/. The blog is one of several associated with RVtravel.com based in Edmonds, Washington. I’ve been getting paid for my screed since last January. That makes me a perfeshunal riter.

The website’s many readers are invited to send questions about the roadside geology they see on their travels. Some ask about cool places to go so they can plan future trips. A few questions are more esoteric: “What’s the difference between the Cascades and Sierras?” The topics range pretty far from the bounds of Northwest Geology Field Trips: all the way to Florida and New England so far, but several have focused on places in the great Northwest, too. I recently wrote about the effects of sea level rise from global climate change, and got some unpleasant comments. That topic seems to anger some people. Ordinarily I write straight geology. I have to scramble to come up with good answers for questions about places I have never been to and rocks I have never seen. Ain’t the internet just great?

Readers from my website are welcome to send in questions. Write Dr. Rock (yers trooly) via a comment at the Dr. Rock blog.

This one illustrated "Why si the Midwest so flat?"

This one illustrated “Why is the Midwest so flat?”