• Your EMAIL ADDRESS is never used for ANY purpose except to send you updates. EVER!!!!!!

    Join 1,216 other followers
  • 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    Visit Mount Baker Volcano Research Center websites Main website and the blog These are no longer actively maintained but are still good references [DT, April, 2020]
  • Most recent posts

  • This website first appeared December 6, 2009

    • 801,528 hits
  • Feel free to use the material on these pages.

    Creative Commons License
    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

Geology of the Rock Trail, Larrabee State Park

Tafoni Wall, striped by tree shadows, is a highlight of the Rock Trail.

Tafoni Wall, striped by tree shadows, is a highlight of the Rock Trail.

I have posted a geology guide to Larrabee State Park’s new Rock Trail. Read the full guide here on the Northwest Geology Field Trips website. The out-and-back hike is just short of 2 miles, and the cliff exposures are perhaps the best in the Chuckanuts. The trail, built by prodigious efforts of over 100 volunteers, was profiled in the Bellingham Herald in February.


Red line marks the new Rock Trail. Contour interval is 20'. Note scale in lower left.

Red line marks the new Rock Trail. Contour interval is 20′. Note scale in lower left.

Fidalgo ophiolite field trip, Part II- Mount Erie

Gabbro at Stop 1. Note the pale vertical dikes near the yellow hammer. Click any image to enlarge.

Gabbro at Stop 1. Note the pale vertical dikes near the yellow hammer. Click any image to enlarge.

A self-guided geology field trip to the second part of the Fidalgo ophiolite (oceanic crust section) is posted here. This field trip visits intrusive and sedimentary rocks on Fidalgo Island, including Mount Erie. This is the second installment in the ophiolite series, which started at the chunk of the mantle at Washington Park.

The April 12th guided geology field trip sponsored by Mount Baker Volcano Research Center will visit some of these rocks. Registration information is on the MBVRC website. If you have been waffling, time to be decisive- the trip is nearly full!

The view south from Stop 2 at Mount Erie.

The view south from Stop 2 at Mount Erie. Here we see an island in Lake Campbell, on Fidalgo Island. Skagit Bay stretches off to the south.

A bit of the mantle: Washington Park, Fidalgo Island, Washington

The 'snake-skin' texture of serpentinite lends its name to 'ophiolite'. This is a nice example near the foot of the stairs.

The ‘snake-skin’ texture of serpentinite lends its name to ‘ophiolite’. This is a nice example near the foot of the stairs.

A geology guide to ultramafic rock at Washington Park, near Anacortes, is now available on Northwest Geology Field Trips. Click here to go straight to the field trip! The rock is the metamorphic rock serpentinite, and was originally in the earth’s mantle below oceanic crust. Exposures are found along the dramatic rocky shore and on bare rocky knobs above the coastal cliffs. A single essential outcrop is highlighted in this quick self-guided field trip. The description explains what ‘ophiolite’ is and points out spectacular glacial polish at the same outcrop.

Coming soon:

  • Mount Erie- Fidalgo ophiolite Part 2
  • Finlayson Point, Victoria
  • Rock Trail, Larrabee State Park
  • ?????

Do you have field trips to share? Please do. Let’s branch out to places in southern and eastern Washington. I’m happy to help you write your guide . Contact me via comment or email:

send email here

send email here

Racehorse Landslide Fossil Beds- big rockfall; trail is brushed out

George Mustoe (WWU Geology Department) visited the famous Chuckanut fossils in the Racehorse Fossil Beds a few days ago. He sends a report  on trail access. (If you aren’t familiar with this place up the Nooksack east of Bellingham, this is the site of the 2009 landslide that exposed the 11-inch-wide foot prints of the 300 pound, 7-foot-tall flightless bird Diatryma, and a host of other animal tracks and plant fossils from the 55-million-year-old Chuckanut Formation. Directions follow George’s trail report. There are many reports on this website about the fossils and the landslide. Go to the older posts and pages.

George’s report:

The largest of the blocks in the 2013 rockfall.

The largest of the blocks in the 2013 rockfall. Click to enlarge any image.

A few days ago I went to Racehorse slide with Gary Coye. We took some gardening tools, and trimmed branches that had grown up along the way trail. There’s presently a clear trail route all they way up from the parking area to the ridge crest, at least until the branches grow back. As for driving, the gravel road is the best I’ve ever seen it in terms of being smooth. This is the first time I’ve been to the slide this year, and I was surprised to see the big rockfall on the scarp face that  must have happened this past winter. I’m attaching some photos, Some of the biggest rocks came from the top edge of the cliff, and carried down intact vegetation. You can see Gary standing on one of the largest blocks, and the scar on the face where the rockfall originated.

The 2013 rock fall came from the upper end of the vertical landslide scarp.

The 2013 rock fall came from the upper end of the vertical landslide scarp.

How to get there:

Google Earth scren capture, looking south

Google Earth scren capture, looking south

These directions are current as of June 23, 2013. Drive the Mount Baker Highway east from I-5 in Bellingham 17 miles to the junction with Mosquito Lake Road. Turn south (right). Cross the North Fork Nooksack, and turn left on the North Fork Road. Set your odometer to 0.0 here. This paved road eventually becomes gravel. You will notice some big blocks and hummocky terrain along the road at about 2.2 miles, the hallmarks of landslides. These are the deposit of a large prehistoric landslide that reached the Nooksack, dwarfing the 2009 slide. The hillsides above  have slid multiple times since the end of the last glacial period, and the mountain itself is called ‘Slide Mountain’. Follow the mainline to a major junction immediately before the bridge across Racehorse Creek, 4.1 miles. Turn right on this gravel logging road, and begin climbing. In about 0.2 mile, you may note a trailhead on the left, with parking on the right. This goes through the woods a couple of hundred yards to the rubble-choked course of Racehorse Creek. A quick trip out this trail reaches the stream. You can walk up-stream a few hundred yards to the lovely multi-tiered water fall.

Continue up the road beyond the trailhead. You will pass  a few side roads, but stay on the main line. Turn sharp left  5.1 miles from Mosquito Lake Road. This left turn is just after a white ’1′ painted on a tall tree on the right, in a clump of woods. The road switchbacks up; pass a couple of minor semi-overgrown spurs to the left.  and is blocked at a fork 5.7 miles from Mosquito Lake Road. 48° 52.295’N, 122° 7.455’W. Walk up the left fork, blocked by deep ditches and mounds of gravel; a trail passes around the right side of these obstacles. Walk up the road 100 yards to the next switchback swinging to the right, next to a high pile of logs. Here is where you take a path into the clearcut, just as the road swings right. The elevation is approximately 1450′, and there is a nice view out to Kendall and the North Fork from here. The entire field trip is on Washington State Department of Natural Resources timber lands. Total driving time from Bellingham is less than an hour. Please consider taking some pruners with you to help keep the trail open, especially where it leaves the road.

The trail reaches the now overgrown landslide debris field in a hundred yards. Here is where to start looking for plant fossils in the broken shards of rock. This is a small ‘overspill’ of the January 2009 landslide. The slide scarp is up the slope and out of site beyond the skyline ridge crest. Pick your way up the ;landslide slope around fallen trees, rock blocks and brush to the skyline, about 200 feet higher. Now you can see the rock face of the scarp to the right, and the upper part of the deposit in the basin below you. The main body of the slide went to the left (east) and down into Racehorse Creek.

Geology guide to Fragrance Lake Trail (Larrabee State Park)

The Christmas Girls had just finished decorating all the sign posts as I pulled into the parking lot. Very festive! Click to enlarge.

The Christmas Girls had just finished decorating all the sign posts as I pulled into the parking lot. Very festive! Click to enlarge.

I’ve written up a geology guide to the popular Fragrance Lake trail. You’ll find it here. Even if the hike is mostly in glacial till, there are interesting stones in it, and the Chuckanut cliffs are always worth a peak. I do some armwaving about the origin of the big cliffs above the lake, too.

Geologic hike on Sumas Mountain, Whatcom County: real geology and a mining hoax

Doug McKeever at the rusted ore cart and the infamous ‘gold vault’ from perhaps the biggest mining scam in the region. Photo courtesy Eric Rolfs.

Hey, take me straight to the field trip!

No, I haven’t finished my book. Time away from the keyboard is important, so what do I do? Go for a hike up Sumas Mountain, come home and write about the geology! I have had this field trip in my head for a while, and needed to share it. I did the hike back in early April with Doug McKeever and Eric Rolfs, but didn’t have my camera, so returned with Scott Linneman May 28. Click here to read the story of an audacious early 19th Century mining scam, and to learn about the geology on this short hike. You’ll also find a rare bonus- an exposure of the basal contact of the Chuckanut Formation, where it overlies the serpentinized ultramafite of Sumas Mountain.

Virtual field trip to Raptor Ridge geology posted

Looking south from Raptor Ridge. Two unrelated types of eroded grooves cut deeply into the soft sandstone. Click to enlarge.

I’m thankful to the forces of nature that present us with such a wealth of fine places to see geology and the scenery that goes with it. In that spirit, I wrote a guide to geology on the hike to Raptor Ridge in the Chuckanut Mountains, south of Bellingham. There are some rock cliffs, two different styles of eroded grooves eroded in the rock, two erratics, a water fall, and pervasively weathered Chuckanut sandstone. All this is capped with a fine view at the top. Click here to read the guide. It is a nice winter hike, unless there is too much snow. But then, it becomes a really great cross-country ski trip! Just the thing, either way to work off some Thanksgiving over eating. See you on the trail!


Geology at Teddy Bear Cove, Whatcom County

Adena Mooers points to the sharp facies change from sandstone to conglomerate at Teddy Bear Cove. Click to enlarge any image.

Teddy Bear Cove has shoreline exposures of west-dipping Chuckanut Formation conglomerate, and  a couple of nice swimming beaches. It is a Whatcom County Park on Chuckanut Bay reached by a short trail from Chuckanut Drive.

Click here to go to the full page.

Updated trip to Nodule Point & Liplip on Marrowstone Island

Concretions in Scow Bay sandstone at Nodule Point. B. Mooers photo.

For whatever reason, the webpage describing the geology at Nodule Point on Marrowstone Island (south of Port Townsend) has received a lot of visits lately. I decided to see what I’d written back in the fall of 2010. I found that somehow I had deleted the photographs. I have replaced those with the originals from Dan McShane, or new ones provided by Bob and Adena Mooers, who field-checked the original trip. The trip describes latest glacial deposits, cannonball-like concretions, and best of all for this volcanophile, a basalt dike intruding the sandstone bedrock.

Visit the webpage here.

A dike cuts sandstone at Nodule Point. B. Mooers photo.

Racehorse Landslide fossil fields- access update

The trail through the clearcut leaves the road about 100 yards from where the road is now blocked off.

Since completion of logging adjacent to the Racehorse Creek fossil fields (Chuckanut Formation), the road has been blocked off about 100 yards below the trail- a tad less driving, a tad more walking. There are big berms built across the access road, but you can walk around them on the right, through the bushes. See the updated webpage here. I’ve highlighted changes in red. The big Doug fir at the end of the trail has died a slow death, smothered in the 2009 landslide debris, but it still makes for a good landmark to find the trail back out. The landslide is rapidly getting overgrown with fireweed and the like, but there are still plenty of fossils to be found. Today, I met a group of students from Harvard University geology department there, on their summer field course. All the way from Harvard to see our fossils. Imagine that. They found the place by stumbling across this website on the internet. Ain’t that somethin’?

If you go, consider taking some garden pruners to help keep the trail open. I brushed the trail today, but it can always use a little help.