Virtual Geology Fieldtrips offered

My friend David B. Williams in Seattle is hosting virtual geology field trips. If you read

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Chapter 14 is a tour of  Seattle building stone

chapter 14 in my book, Geology Underfoot in Western Washington, you will love the ‘Stories in Stone’ tour. My chapter was inspired by David’s downtown Seattle Urban Geology tour.

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New edition of David’s book. GET IT!

Through the Seattle Architectural Foundation, David is offering Stories in Stone (June 10)- Most people do not think of looking for geology from the sidewalks they travel, but for the intrepid geologist any good rock can tell a fascinating story. On this virtual walk, which incorporates illustrations and photographs, you will explore a range of rocks equal to any assembled by plate tectonics, from 3.5-billion-year-old gneiss to 120,000 years old travertine; fossils the size of cinnamon rolls, and rock used by the Romans to build the Colosseum. In this tour of Seattle building stone, David will discuss history, transportation, and architecture to give you a new way to appreciate urban geology. Plus, you’ll even be able to “visit” a couple of quarries and see where the stone originates. $5/person

Through Airbnb David is offering The Secrets of Seattle’s Disappearing Hills (Multiple dates) [Mondays and Thursdays in June- dt]- On this virtual walk you will explore Seattle’s most famous land alteration project: the complete removal of a hill in the downtown area. Through a series of illustrations and maps and historic photos, we’ll virtually cover about 1.5 miles circumnavigating the old hill in the area known as the Denny Regrade, where Amazon’s campus is now located. Along the walk, we’ll learn about how and why early Seattleites undertook this audacious and ambitious project, which they completed between 1897 and 1930. We’ll also see clues in the landscape that allow you to visualize Denny Hill as well as see historic images to better understand the story. $7/person
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Chuckanut Fm. sandstone forms the vertical columns on the Pioneer Building in Seattle. Photo copyright Dave Tucker.

Fixed link to glacial erratic field trips

Several alert readers let me know that the link to the field trips to glacial erratics in the Salish Lowland was broken. So, I have fixed it. Go to the ‘Field Trips’ tab at the top of this page, scroll down to the blue Glacial erratics text, and try out the link. Unfortunately, the online inventory of glacial erratics maintained by UW students, reached by a link on my erratics page, is an uncompleted website, a student project, and does not actually take you to an inventory or map or photo. Dang.

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Just for grins- here is a large erratic not previously visited on this website. Any one know where it is? Hint- north of Seattle, south of Bellingham. Its a pretty big rock. Shows well in Google Earth.

Urbanite examples sent by readers- 2. Concrete High School, by Todd S.

Concrete, WashingtonTodd Schlemmer provided photos of the ‘rock’ lining the road that passes under Concrete High School. The school, built in 1952, is unique as it is built as an overpass over the access road. The design was reportedly intended to provide a dry place for a bus-loading zone; given the 65 inches of annual rainfall here, not a bad idea.
To get there, go east from Sedro Woolley on Highway 20 to Concrete, turn south (right) on Superior Avenue, and voilà! You can’t miss it. It is 23 miles, whether you drive the highway or do what Todd did- ride the graveled rails-to-trails Cascade Trail from Sedro  to Concrete through the Skagit lowlands.
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Your target urbanite- stepped structure at the underpass.

The underpass is lined with oddly stepped rock. Well, ‘rock’, because it is, of course urbanite. Given the town’s name, you shouldn’t be to shocked.

Concrete (formerly ‘Cement City”) produced

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These 90-foot tall silos once held Portland cement produced by Concrete’s cement plant. They are on the corner of Highway 20 and Superior.

Limestone from the quarry north of town was made into Portland cement in Concrete, and was used for the two dams built by Puget Sound Power & Light up the Baker River, and for the three Skagit River dams built by Seattle City Light above Newhalem.

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Under the high school, the stepped concrete foundation has been sculpted with ‘fractures.

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Look for places where the exterior facing has eroded away. Pale blocks of cement are exposed, with slabs of concrete layered on them.

A field trip guide to the limestone quarry just north of town is on Northwest Geology Field Trips here. Bear in mind that the quarry is now closed, and visitors face arrest for trespass. Big bummer- it is fascinating.

Thanks for the photos, Todd!

Urbanite examples sent by readers- 1

Reader submissions to my initial ‘Urbanite’ posts are rolling in. Here’s one from Dan Burwell. (I have another in the works to follow this one already. Send yours!) Dan shows us a really cool ‘soil nail wall’, so I follow up with a basic explanation about ‘soil nail walls’ using photos from the internet . The wall on W. College Way in Bellingham, featured in my preceding post, is a nicely disguised soil nail wall.

We’ll start out with Dan’s note and photos.

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Dan’s ‘soil nail wall’. Can you spot the fault? Answer at the end of this post. NO PEEKING!!!!

Here is a wall I designed, installed in Manson, WA near Chelan in 2008. It’s a soil nail wall where “nails” are drilled behind the wall as the face of the wall is excavated from the top, working down. The nails are set in grout and then attached to the wall face. The nails use friction to resist soil pressure pushing the wall outward. Once the nails are installed, the wall face is then sprayed with shotcrete to form a short term construction wall face (usually done in stages to keep sloughing to a minimum). A final wall face can then look like a rock outcrop or whatever else you want to dream up which combines with the construction face and is designed for seismic forces.

The sculptors are a specialized group that work all over the world. I asked them to sculpt a fault and they did a reasonable job of it. Can you spot it?

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Dan Burwell | RH2 Engineering, Inc.,  Bellingham

Now, here is my photo essay on construction of a soil nail wall.

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A soil nail schematic, so you can see where we’re headed here. This example has no cast concrete or rock work on the outer surface, so differs form the fancy wall Dan showed us.

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Here’s a ‘soil nail’. Not really a nail, but a grouted steel rod or pin.

 

 

 

 

 

 

 

 

There are variations on the method, but here’s a generic one. Start out with an unstable soil or rock face. Work progresses from the top down if the finished cut is tall. dywidag-systems-soil-nails-wall-construction-08

Drill holes into the exposed face.

3. Drilling

This is one hell of a noisy job. Hopefully with a strong union so workers can enforce safety. Note protruding soil nails and mesh higher on the wall.

4. drilling detail

Insert the ‘nail’ structure into the drilled holes. Layer with steel mesh. Remember work is from the top down so the rock or soil face above these drilled holes is already stabilized with shotcrete.

6. shotcreting a low wall. drains

Applying shotcrete, blown under pressure through a feeder hose. The kickback can be strong so watch it! This wall has drainage installed at the base, usually required. The drain pipe collects water to reduce pore pressure in the soil behind the wall.

Blow shotcrete over the mesh. Add outer bearing plates on the ends of the exposed nails, to bind the shotcrete/mesh structure to the nails in the soil wall beneath. Another coat of shotcrete could be added to cover the ends of the nails as in the case above.

Now for the urbanite. Install poured concrete or concrete blocks or even cemented real rocks over the shotcrete. Sculpt as desired. 4fbac1ae9814b22f440e824a6b165325_XL

Finished product. Plus a couple decades.W. College Way 1 mark

If you didn’t spot the fault in the first photo, here it is. The ‘faux fractures’ are offset at the top of the face. The lower fracture cuts across the fault, and is an added touch of disguise. Well done, Dan and crew who built the wall.OLYMPUS DIGITAL CAMERA

Is this the best urbanite anywhere?

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The ‘outcrop’ on W. College Way. There isn’t much room to get up close and personal, but with reduced traffic when campus is closed, you can pull it off. 

A great example, maybe the best I’ve ever seen, of urbanite nicely mimicking real rock is on W. College Way in Bellingham, between Highland Drive and Bill McDonald Parkway, just up the hill from the Wade King Student Rec Center. An exposure of apparent sandstone of the Chuckanut Formation (or is it?) lines the road.(For field trips to real exposures and features in the Chuckanut, go here on this website.

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Here’s a closer view. Looks pretty natural, eh?

Actually, there really is Chuckanut here, just up the hill, but it is buried in the bushes. This is the most convincing urbanite I can think of in these parts; maybe anywhere. If you know of something really good, please send pics and the location and the story if you know it. If you know of something really badly done, send that. too.        dtchico@gmail.com copy

 

How can I tell this is urbanite and not the local sandstone? It could have fooled me.

First lets take a look at the real thing.

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Dipping Chuckanut mudstone and more massive sandstone beds north of mile post 13 on Chuckanut Drive, south of Bellingham.

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80-foot wall of Chuckanut sandstone and shale in the scarp of the Racehorse Creek landslide. Read about that 2009 event here on my website.

 

 

 

 

 

 

 

So you can see, the illusion isn’t bad. The engineers did it well, and likely had the assistance of a geologist.

UPDATE– April 10, 2020. Indeed there was. According to alert reader Sue M, the geologist on this project was J. Robert Gordon of Geoengineers in Bellingham

Now, let’s get a close look at this urbanite.

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You can see that the surface is sprayed on, and in places it drips, like just to the right of my finger.

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And the ‘cracks’, meant to mimic fractures in sandstone, all bottom out- they were carved into to hardening concrete. You have to scrub out the accumulated soil to see this.

 

 

 

 

 

 

 

 

 

 

 

 

 

But now, for the real evidence. I remember when this concrete was poured to stabilize this slope. The steep slope of unconsolidated soil and glacial till slumped a couple of times and covered the road. This was done in the mid-1990s. Since then, our prolific vegetation has colonized the ‘roadcut’. Well done, engineers!

Urbanite is everywhere

Dear friends,

Over the past few years, “fake” has become a much-used term. So, time to apply it to rocks. Make that “rocks”, as in “urbanite”. No, not those folks. I am referring to artificial, rock-like materials- concrete, asphalt. And now, plastics. I discuss it quite a bit in Chapter 14 of Geology Underfoot in Western Washington.

Though you may not be getting out and around much these days, go for a stroll and take photos of some good examples and send them to me at dtchico@gmail.com copy.

I will put them up on a thread below, and let you know when I do. Photos will be credited to you, unless you instruct me otherwise. Tell me where the urbanite is, if it fooled you or seemed particularly ingenious, and how it is used.

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The shape, and the fact that there are two of these things the same size and shape (no, not the one in the red jacket- look behind him!) but with slightly different exterior molding was a give away. Not to mention the padlocks and the access plate at the bottom…

Here’s an example I came across in Bellingham the other day. This is at the railroad crossing at the entrance to Boulevard Park. It is some sort of thin, molded plastic or fiberglass. I could tell right away it was fake because of its usage and overall appearance. Was the manufacturer trying to mimic a particular type of rock? The pale gray  blockiness right away was reminiscent of granodiorite.

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Zoom in on the photo to see there are even a few pale fake intrusions, with a finer ‘grain’ size. As if a blob of different magma was trapped in the host ‘rock’.

Hmm, how about the texture, that is the close up appearance and relationship between any fake components meant to resemble ‘minerals’ or ‘clasts’? Not bad. Right up close there are even two colors of ‘minerals’, black and white. As in white plagioclase and dark biotite mica, kinda sorta like the real thing. So, final verdict: up close, not bad. But from away- meh.

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Here is a granodiorite erratic at Highline Community College. Go to the link to read about this rock and that distinctive white linear structure. Bud Hardwick photo.

Geology field guide to the Blue Lake Trail, Washington Pass area.

As promised, I just published a geology guide to the Blue Lake Trail. Find it here. This is a deservedly popular hike off Highway 20 near Washington Pass. It skirts below the pointy crags of Liberty Bell and the Early Winters Spires, composed of a true granite- a very unusual rock in the North Cascades. But there is also some other cool geology at Blue Lake. Go to the page, read up, and get set for a gorgeous 4.4 mile round trip geo-trip. It’s a pretty easy hike. Really. And maybe a swim. (Geeez, but the water is so cold. Or so I hear. I, of course, wouldn’t think of swimming in that lake.)

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The Liberty Bell and Early Winters peaks east of Blue Lake.