Winchester Mountain trail side geology

I hiked up to the restored fire lookout on Winchester Mountain on Labor Day, 2022. Winchester is above Twin Lakes off the Mount Baker Highway. I wrote up what I could figure out about the trail side geology and posted it in the ‘field trips’ section of this website. Thanks to the Mount Baker Club for maintaining the lookout building, and boo to the anonymous idiots who broke into it and damaged the door last winter.

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The geologic highlight of the Winchester Mountain trail, other than the stupendous views into the complex geology of the North Cascades, is the trail climbing along a yellow dike cutting across the basement rocks.

The approach is on a challenging but very fun (if you like that sort of thing- I do!) rough road. I’m glad I had my Crosstrek with its ‘X-mode’ for traction. The views into the Cascades are the main attraction for most who visit, but I got a big kick examining a 2+ meter wide dike that intersects the trail 300 feet below the summit. The hike is moderate, gaining 1300 feet in just over 2 miles on a good trail. But if you are fazed by the road, you will need to add a lot of road walking- up to 2.5 miles each way if you park near the Yellow Aster Butte trailhead. If you are lucky some nice person may offer you a lift.

Rock Trail in the Chuckanuts updated

I updated my geo guide to the Rock Trail in Larrabee State Park; I hiked it last Friday on a gorgeous warm spring day. This is one of my favorite geology hikes in the park; I wrote the original description on this website shortly after the trail was finished in 2014. So, what’s new? A ways beyond the last high sandstone wall I came across a new [to me] exposure of sandstone, scoured and cleaned off. Looks like the overlying soil and vegetation slid off and the beautiful rock has since been been flushed clean by heavy rains. The slab reveals some very fine cross beds so I added this near the end of the guide. Go now- before the trees leaf out there are views east to snowy Mount Baker and the Sisters Range.

Cross-bedded stream sand in the ‘pale slab’.

About these field trips- they are not actually ‘virtual’.

Dear friends and subscribers,

There seems to be considerable misunderstanding of my use of the term ‘virtual’ field trip. I do not actually lead the field trips i publish on this website. I write them up so YOU can go do them yourself; they are intended to be self guided. My apologies for misunderstandings and apparent misuse of the term. I will no longer these field trips as ‘virtual’, as that apparently implies you can ‘join me’ on line somehow.

It is my hope you will find field trips to places near you, or that pique your interest, and go there. You can take along the website on a smart phone, or use the tips here to show you how to efficiently print out the trip on actual real paper.

Dave Tucker

Point Whitehorn: updated field trip

I updated my 11-year-old virtual field trip to Point Whitehorn, up the coast from Bellingham and just south of Birch Bay. I have been there many times in the intervening years. It’s always a fine jaunt, especially in winter and most especially on the day after Thanksgiving! There is plenty of changing geo scenery due to wave erosion of the beach bluff. The updated page has a lot of new pictures. Like this one.

Whoo hoo! If any visitors have pictures documenting further erosion around this big erratic, send them to me. How much longer until it is on the beach?

Damfino lakes geology hike

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Mazama O and Baker BA ash on the Damfino Trail.

I just posted my geology field trip guide to the Damfino Lakes Trail, reaching Excelsior Pass from the Canyon Creek road to the north- and a much shorter hike than the Excelsior Trail.

The rock exposures aren’t all that great, but there is a small and lovely exposure of Mazama ‘Layer O’ volcanic ash and Mount Baker BA ash sitting right on top. And of course the flower meadows and the views.

Excelsior Trail geology guide is up!

As promised a week ago, I completed the geology guide to the Excelsior Trail, rising from the Nooksack River east of Glacier to Excelsior Pass and ‘Excelsior Peak’. I will post a separate description for the ‘back door’ trail via the Damfino Lakes trail.

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Steeply dipping Jurassic Nooksack Formation marine sedimentary rocks just east of Excelsior Pass.

Mount Baker Geology Report is published!

Dear friends,

coverMany of you will know that for years I have been among a group of geologists putting together a USGS report on the volcanic history of Mount Baker since the end of the last glacial maximum {that’s geologese for ‘Ice Age’). That paper has just gone up on line and you can read it here:

The authors are Kevin Scott (USGS, retired); myself; Jon Reidel (North Cascades National Park); Cynthia Gardner (Cascades Volcano Observatory, USGS); and Jack McGeehin (USGS, who did the C14 analyses)

The brief citation reads:

Latest Pleistocene to Present Geology of Mount Baker Volcano, Northern Cascade Range, Washington: This report summarizes the multifaceted and complex surficial geologic history of Mount Baker just before, during, and after withdrawal of the latest Pleistocene Cordilleran ice sheet from the Mount Baker area. Nearly 80 new radiocarbon ages are reported that constrain the timing of glacial and volcanic events and help define four post-glacial eruptive periods: Carmelo Crater (ca. 14–11.6 ka), Shriebers Meadow (ca. 9.8–9.1 ka), Mazama Park (ca. 6.7 ka), and Sherman Crater  (1842–1880 C.E.).  The end of the Carmelo Crater eruptive period marks the end of Mount Baker edifice construction and the beginning of mainly destructional processes (flank failures and resultant lahars) during the Holocene.  It also marks a shift of vent location from the summit to off-summit locations. Findings from this paper dovetail with the bedrock history of Hildreth and others (2003) to give a comprehensive view of the United States’ most northern Cascade volcano.


Scott, K.M., Tucker, D.S., Riedel, J.L., Gardner, C.A., and McGeehin, J.P., 2020, Latest Pleistocene to present geology of Mount Baker Volcano, northern Cascade Range, Washington: U.S. Geological Survey Professional Paper 1865, 170 p.

Coming up: Excelsior Trail geology guide

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Looking west along Excelsior Ridge from just below the pass.

In the next couple of days I plan to post a geology guide to the Excelsior Pass Trail. The trailhead is near Nooksack Falls; the trail climbs out of the North Fork Nooksack valley to Excelsior Pass. The trail ascends through the Jurassic Wells Creek Volcanic Member of the Nooksack Formation; I wrote of them waaaaay back in 2010, here. Find the glory of flower meadows and views and, at the pass, the reach small exposures of conglomerate and breccia in the slightly younger Nooksack Formation.

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A fragment of greenstone from the Wells Creek volcanics. Exposure to the atmosphere and water has produced the 1-cm-thick weathering rind on two sides of this bit of rock, but the greenish rock in the center is fresh greenstone- at one time a submarine volcanic deposit.

Racehorse fossil fields- update

P1040854 mark rszI visited the Racehorse Fossil Fields up the North Fork Nooksack on July 10. I have updated the access directions. If you haven’t been there in a while you may marvel at the amount of biomass that is now covering the 2009 landslide and growing on the road. It is now a foot path, in places a green tunnel. A relatively simple walk though, for 1 mile and there are still plant fossils to be found.

It was fun to see so many website subscribers up there. DaveP1040856 rsz mark

New geo field trip to Chuckanut rocks posted on this website

Dear Friends,

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Outcrops along the road.

I just posted a new virtual field trip. It is a 3-mile round trip walk on a logging road in the Chuckanut Mountains just south of Bellingham. It examines near-continuous exposures of a variety of rocks in the Chuckanut Formation. The road is gated so no vehicle traffic.

You will see conglomerate transitioning to sandstone and vice versa. The trip describes the dip, or tilt, of the rock layers, and finishes up at a quarry in remarkable conglomerate. Plus a very nice view down the length of Lake Samish. P1040814 rsz mark