Evolution of the Puget Lowland, last 20,000 years

Animation of the advance and retreat of the last great glaciation in the Puget Lowland is available on the Burke Museum’s YouTube channel. Thanks to reader ‘Deb’ who notified me that the link in the ‘Lake Stevens Erratic- the largest in the US?’ page was broken. It’s been repaired. The animation is based on a model by Ralph Haugerud of the USGS- see the very end of the animation for full credits. Unfortunately, the model is only for Puget Sound, and does not include the San Juan Islands or points north. The source of the glacial lobe is not shown- the interior of British Columbia, the BC Coast Mountains, and the Canadian Rockies. The diagram shows the bigger picture, which has a chapter on glacial erratics, and another on the history of glaciations in the lowlands of western Washington.


Diagram from my book,Geology Underfoot in Western Washington showing sources and paths of ice related to the Vashon Lobe. The glacial tongue reached its maximum extent south of Olympia around 16,000 years ago.

This animation is a bit different from the original. This one shows events in the Lowlands following retreat of the Vashon glacial lobe, such as the Osceola Lahar from Mount Rainier 5600 years ago that reached the salt water Duwamish Embayment near Auburn, and local rebound of the crust from the weight of the ice.

If anyone finds broken links anywhere on this website. please notify me by way of a comment on the page. If you know if a replacement link, please include that.

Snohomish and Tacoma Geology Underfoot Book talks

A reminder that I will be in Snohomish this Saturday, Feb. 20, and in Tacoma next Thursday, Feb. 25, to talk about Geology Underfoot in Western Washington.

SNOHOMISH Saturday February 20th, 2 PM, Sno-Isle Public Library, 311 Maple Ave., Snohomish, WA

TACOMA Thursday February 25 Kings Book Store, 218 St Helens Ave Tacoma, WA. 7 PM http://www.kingsbookstore.com/event/2016-02


Welcome new subscribers

January 1, 2014. Happy New Year!

A nice sight in the gloom of a NW winter. Franks Beach on Lummi Island.

A nice sight in the gloom of a NW winter. West Beach on Lummi Island.

Many thanks and a big welcome to the 154 people who have subscribed to this website in the past year. There are now 538 subscribers. Posts have not been very frequent because I put most of my writing energy this year into finishing my book, Geology Underfoot in Western Washington. But, the book has gone to the editor at Mountain Press Publishing (Missoula), and should be out in Fall of 2014. You’ll certainly get the good news as the publication date nears. While I’m waiting for the editor to get back to me, I continue to write another, with the working title of  Road and Trail Guide to Mount Baker Geology. But, I promise to add more field trips to the blog in 2014.

Readers are encouraged to send in their own geology field trip guides, or suggest good places for me to visit in Washington and British Columbia- perhaps in your company. Send a comment to the blog, or an email directly to me. Winter has arrived in the high country, so let’s focus on the lowlands for now. A Victoria, BC field trip submitted by Gerri McEwen will be posted in the next few days. If you know of a place in the mountains, go ahead and let me know why it seems interesting (with your photos) and I’ll try to get to it next summer. Even better, you write it up! Also, if you come across any good field trip guides, send the info so I can add it to the “Guides, Books and Maps” page.

email address to send reports and photos. I'll credit you.

email address to send reports and photos. I’ll credit you. This is not a link.

There were 85,000 visits to the website in 2013. The most popular page on the website in 2013 was a tutorial on sedimentary structure (strike and dip of beds). That one had over 4200 hits. I think many students find it in the course of school projects. And many people checked out the trip guide to the Nooksack ‘Gold Mine’ near Sumas, in Whatcom County. The most popular topic of all time on this website remains the story of Diatryma, the giant flightless bird whose 10-inch footprints were found in the Chuckanut Formation in 2009, and put on display at WWU’s geology museum in 2010. (Over 10,100 site visits to date).

A request- when you take one of the field trips on the blog, please drop me a note via comment and let me know how it turned out. Especially let me know if road or trail names have been changed or are labeled differently, if trails are washed out or rerouted, if you couldn’t find what I tried to direct you toward, if my description was inaccurate. I’ll do my best to update things.  But, please, at minimum, tell me you went.

MBVRC field trip to Baker Lake during draw down.

MBVRC field trip to Baker Lake during drawdown. Great geology!

So enjoy the next year’s ramblings from your scribe. Visit two other blogs I moderate: the Mount Baker Volcano Research Center’s is http://mbvrc.wordpress.com. MBVRC occasionally offers fundraiser geology field trips oriented toward folks just like you. The best way to stay posted is to subscribe to the blog. And, a blog for die-hard cross-country skiers in the Chuckanut hills: http://chuckanutcrosscountryskiing.wordpress.com/


Guided geology trip to Ptarmigan Ridge, Mount Baker

Mount Baker and Rainbow Glacier from Ptarmigan Glacier.

Mount Baker and Rainbow Glacier from Ptarmigan Glacier.

There are three spaces left on North Cascade Institute’s guided geology hike [led by yours truly] to the volcanic wonders along the Ptarmigan Ridge trail. This traverses the high country between Mount Baker and Artist’s Point at the end of the Baker Highway.

Sunday, September 29 Rendezvous in Glacier at 8 AM. An all day hike, about 6 miles round trip, 500′ elevation gain/loss. $95 includes bus from Glacier.

Sign up info here:


Here’s the NCI blurb:

Experience time travel by foot on the Ptarmigan Ridge trail in Mount Baker’s radiant late-summer high country. Our field excursion will begin above tree line at Artist’s Point at the end of the Mount Baker Highway before venturing out toward the simmering, glaciated volcano herself. Along the way, we’ll travel over ancient records of volcanism as we traverse the 1-million-year-old Kulshan caldera, a giant volcano that erupted cataclysmically through a continental ice sheet long before Mount Baker built itself from stacks of lava.

As we hike past lava domes that erupted shortly after the caldera collapsed, we’ll lay hands on much younger columnar andesite that still predates Mount Baker, discuss the origin of the eroded table at Table Mountain, and examine layers of volcanic ash preserved in the soil, including the famous Mount Mazama/Crater Lake layer.

Dave is a leading geological expert on the Mount Baker region and will share his intimate knowledge of the natural and cultural history of the area. He’ll interpret the story of this landscape as evidenced in its rocks and ash.

Geology Underfoot in Western Washington- news about the publication date.

Dear friends,

News received here at geo-central today is that my geology guide book, Geology Underfoot in Western Washington, will be published in 2014 by Mountain Press Publishers in Missoula. Here is a link to the other books in the series. I have only three chapters yet to write: Johnston Ridge at MSH, Nisqually Vista at Rainier [deals with the consequences of rapid glacier recession] and the Introduction. Three others are currently in peer review by geologists who are authorities on those specific places. The MS should go to the editor around the end of February this year [I do have other things to do, believe it or not]. Thanks to all for the encouragement in this long process. Now that you know more about a publishing date [vague as it is] you can start saving your pennies to buy a copy or two; it should be a good gift.  Once the book gets through revisions, I’ll publish a list of the chapters, and hopefully more news on the publication date.

Here is a photo from the book.

Here is a photo from the book.

Here’s a figure from one of the most recent chapters.

What do you think it is about?

Pillows in the Middle Fork Nooksack

Stacked pillows. Stolen from a commercial website. So, sue me.

Stacked pillows. Stolen from a commercial website. So, sue me.

(Click HERE to go straight to the page about the pillows along the road.)

No, pillow lava, silly!

Cross-sectioned basalt lava pillow in the Elbow Lake Formation, Middle Fork Nooksack Road. Click to enlarge.

Cross-sectioned basalt lava pillow in the Elbow Lake Formation, Middle Fork Nooksack Road. Click to enlarge.

I planned a XC ski trip up the Porter Creek Road or elsewhere off the Middle Fork Road today, but it was raining and 41 degrees. Indulging my secret identity as a geologist, I instead poked around in a roadside quarry, looking at pillow lava in the Elbow Lake Formation. A rewarding outing from Bellingham if you have a 2-3 hours on your hands and a deeply felt need to look at some exotic, unusual, and (admittedly) not too beautiful rocks. The saving grace is the lava pillows, and a cup of coffee on the way and on the way back. As an added bonus, there is access to Twin Sisters dunite nearby.

P.S. There ARE some nice roads to ski up and back down off the Middle Fork.

Online geology field trip: the Deadhorse Volcano, Skyline Divide, Mount Baker volcanic field

The last couple of miles of Skyline Divide. The Deadhorse Volcano is marked by the red pin and Hildreth’s unit designation ‘acr’. Click to enlarge.

A nearly unknown volcanic vent is exposed in cross section on a rock wall at the south end of Skyline Divide north of Mount Baker. Click here to read my on-line field guide to the informally named  “Deadhorse Volcano“. Yes, I know, winter approacheth, so chances to visit this eroded volcano are fast-slipping away. Hope for a weather break, or save this little gem until after the snow is gone next year. The snow that hasn’t fallen- yet.

Cougar Divide field trip updated


Pale dikes intrude Nooksack Fm. at the head of Dobbs Creek.

I hiked Cougar Divide again on September 12, and have updated the field trip guide. You can read it here. This is the easist and best place in the area to see intrusive dikes.

The updated guide includes these changes: better directions to find the oldest dated rock in the Mount Baker volcanic field, a rhyodacite dike, and the GPS coordinates have been changed slightly; a new photo added showing the dikes at the head of Dobbs Creek.

The ridge is beautiful. I noticed that there was some hoar frost on the trail in a few places, and there are patches of fresh snow on the snow slopes below Chowder Ridge. Take an ice ax to reach Chowder, as there is a short section of firm, steep, and exposed snow to cross just below the ridge.

Virtual geology field trip: Cougar Divide

Acres of flowers and meadows on the crest of Cougar Divide. Did I say I like this hike? The snow fingers mark the Dobbs Creek headwaters, site of many dikes. Copyright Dave Tucker.

I have broken out of my writing doldrums and written a self-guided geology field trip to Cougar Divide on the north flank of Mount Baker. Figure I better provide people with a summertime hike before it is too late! This hike is mostly volcanic geology that long predates Mount Baker. In fact, the oldest dated rock in the Mount Baker volcanic field is found on the ridge crest. That alone makes this beautiful hike significant.

Read the field trip here.

First MBVRC field trip of 2012

The first Mount Baker Volcano Research Center geology field trip of 2012 is announced over on the MBVRC blog.

The Pinus Lake lava towers 600′ above the Baker Highway east of Nooksack Falls. Click to enlarge any photo

The trip will head up the North Fork Nooksack and visit the Pinus Lake lava flow, the Wells Creek formation (subducted sea floor basalt), the gigantic Church Mountain Landslide, an older and larger version of the Racehorse Creek landslide, and Nooksack Falls. The trip will be led by Doug McKeever, geology Professor at Whatcom Community College. The first ten people have already signed up and the trip will reach its limit of 26 quickly so click here to  learn more about the trip and how to sign up.