Glenn Jaecks
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glennjaecks.bsky.social
Glenn Jaecks
@glennjaecks.bsky.social
1.1K followers 1.2K following 1.3K posts
Geology Professor, Cyclist, Commuter, Beach, 'n' stuff. I think I might be a Le Guinian anarchist, with a tinge of Marx and democratic socialism. I teach climate change.
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glennjaecks.bsky.social
Trolly system in Dubuque, Iowa, a little more than a century ago. Bring them back!
Reproduction of a 1910 photograph of downtown Dubuque, Iowa, USA showing a row of shops, with four filled cars of an electric trolley system. No automobiles to be seen. Photo hanging in 7th floor of the Julien Hotel. Streets of brick.
September 30, 2025 at 1:46 PM
glennjaecks.bsky.social
Here is one and a bonus chevron fold shot
Turning aspen nestled in a side valley to Kings Canyon or golden leaves surrounded y grey granite. Photo by student, Nathan Photo of decidedly not cylindrical chevron folds in the Boyden roof pendant, along kings canyon between the caves and where the valley opens up into a U-shaped valley layers are generally a few cm thick
September 24, 2025 at 4:26 PM
glennjaecks.bsky.social
Field trip to Sequoia and Kings Canyon National Parks
I prefer this to Yosemite. With @thomsec.bsky.social
This is General Sherman, the world’s most voluminous tree, estimated to weigh 1,200 metric tonnes. If Sherman were carbon, it would take 8,333,000 of them to equal annual human carbon emissions. We need to stop burning fossil fuels, planting more trees won’t fix the problem. (I like trees in the proper setting) we need to conserve our forests Group selfie fromour filed trip to SEKI, in front of the biggest tree A giant sequoia named general sherman.
September 21, 2025 at 5:24 PM
glennjaecks.bsky.social
From my bike ride today Fight me bro!
Mantis on gravel poised to fight with arms wide, like Temba, wings ruffled like a Targ would ruffle its scales.
September 5, 2025 at 10:51 PM
glennjaecks.bsky.social
#fossilfriday
one from my dissertation (slightly less than 1cm wide for scale)
Interior view of a dorsal valve from one of "my" thecideide brachiopods- a weird cementing group notable for their small body size and mysterious origins (Triassic to Recent). The image shows the convoluted lophophore support structure, like a bunch of fingers pointing down towards the bottom of the picture.
September 5, 2025 at 3:15 PM
glennjaecks.bsky.social
Post your dream ride

opencycle.com/thumbnail/9a...
August 23, 2025 at 2:32 AM
glennjaecks.bsky.social
Tree frog with lichen, central Wisconsin, USA
A dark green tree frog with yellow arm pit perches atop a fence post covered in several species of lichen. (The frog was rescued from the back of our van) A dark green tree frog with yellow arm pit perches atop a fence post covered in several species of lichen. (The frog was rescued from the back of our van)
June 30, 2025 at 3:14 PM
glennjaecks.bsky.social
badlands? More like totally awesome lands!
June 18, 2025 at 1:39 AM
glennjaecks.bsky.social
Wyoming rest areas are woke: they’ve been using passive solar and geothermal heat pumps for decades! #heatpump
Diagram of the energy saving design of a Wyoming rest area in Lusk. It utilizes passive solar, along with ground exchange heat pumps to keep cool in the summer and warm in the winter, and awesome all year round The story of how Ladybird Johnson was involved in improving our highways, and how Wyoming responded with the new rest area designs
June 17, 2025 at 1:43 AM
glennjaecks.bsky.social
It’s a day for tacos #TACO
Tacos from Wendover. Not pictured: awesome gorditas
June 14, 2025 at 6:59 PM
glennjaecks.bsky.social
Bike trip to the hardware store #cargobike #squidfacts #waroncars #activetransportation
My cargo-adjacent ebike locked to a poorly-designed bike rack, in front of a pebbled, concrete wall that is my local hardware store in Sacramento. Squid facts sticker for scale
June 11, 2025 at 6:18 PM
glennjaecks.bsky.social
happy world bicycle day! I think I'll ride down to the eye center to have them fix my spectacles. #worldbicycleday
My gravel bike leaning against a tree, and an empty bay of Folsom Lake in the background, under overcast skies my gravel bike leaning up against a picnic table at the old farm above McClure's Beach, Point Reyes National Seashore. Barns and farmhouses nestled under pine and eucalyptus trees in the background, below clear blue skies My single-speed Phillips bike, with the annoying british 26 inch standard tire size, which is different than the 26 inch mountain bike tire size. My trusty old trek 2000, with replacement forks from Colnago. I built this up originally in 1986. Central Wisconsin glaciated landscape in the background, taken from the park on top of "Mount Morris," a glacial moraine.
June 3, 2025 at 4:10 PM
glennjaecks.bsky.social
Wee yardwork surprise today- a sharp tailed snake (I think) #herps #snake #herpetology
A closeup of the pinkish snake, coupled amongst the coarse gravel A wee sharp tailed snake amongst the coarse gravel.
June 2, 2025 at 9:26 PM
glennjaecks.bsky.social
#fossilfriday even though grades are not done.
A bottle of red wine with a logo of an ammonite cross-section in gold
May 24, 2025 at 1:43 AM
glennjaecks.bsky.social
Looking for patio stones, and found some rain drop impressions.
Sandstone with faint raindrop impressions. The sandstone most likely formed as a sand dune deposit. I say most likely since I don’t really know where it’s from, supposedly Arizona
May 20, 2025 at 6:09 PM
glennjaecks.bsky.social
I made a friend on my bike ride today
A gravel trail in open woodland and blue sky above. A rattlesnake crosses the trail to hide in the grass on the right A closer shot of the rattlesnake on the trail; it didn’t want me to be there
May 9, 2025 at 11:04 PM
glennjaecks.bsky.social
Field trip to the north coast redwoods in the books; lots of big trees, especially along Bull Creek, another great visit to Hog Island Oyster Company, and some views of the coastal melange north of Arcata.
View of the trail at Rockefeller Grove. Ferns in the foreground, big trees to either side, with sunlight glinting through. The trees here can exceed 100m in height and inspire awe. Student holding up a fallen giant, exceeding 2 meters in diameter. Splintered remains of the violent fall to the left Lucas at the Hog Island facility explains a step in the oyster rearing process to a couple of students. The barrel he’s holding has a mesh screen on the e bottom to only hold in baby oysters of a certain size. A sandy beach with some rocks in the shallow water being swept by waves and a (dead) tree-topped sea stack in the background. White, streaky clouds in the background
May 4, 2025 at 9:45 PM
glennjaecks.bsky.social
Indeed!
A path though towering giants of the California Coast Redwoods Closeup of a single redwood, showing the thickness of the bark. Top half of my head in the foreground for scale
May 2, 2025 at 1:17 PM
glennjaecks.bsky.social
Heading to Bull Creek for the first stop of our redwoods trip; last years photo
Students on a first path surrounded by gigantic redwood trees and a fallen redwood log
May 1, 2025 at 9:25 PM
glennjaecks.bsky.social
Last summer on top of Smarna Gora, Slovenia with my daughter.
Two doofuses in a selfie with fog below in the background, hills poking up in the background, and a gorgeous, partly cloudy sky above.
April 30, 2025 at 3:46 PM
glennjaecks.bsky.social
Lupines, egrets, Dudleya, and a bike glamor shot (last week the beach was hopping, that’s what a 20-30 degree f cooling will do). Good ride today, despite the wind.
A gravel path lined with lupines on the outside of the curve A lone egret on the far side of a pond. Grasses and algae in the foreground, meadow and woods in the background The succulent plant, Dudleya, making little patches of red in the grey volcanic/fluvial rock. Dried grasses in the background. My grey gravel bike with green tires rests against a tree, near a picnic table and Folsom Lake in the background.
April 25, 2025 at 11:56 PM
glennjaecks.bsky.social
#invertfest entry: an anemone rock. Low tide at the end of Estero Trail,
Point Reyes
A small boulder the size of a large boulder, completely covered in anemones. Surrounded by a shallow scour moat, filled with water. Mid in the foreground, water in the background
April 24, 2025 at 9:07 PM
glennjaecks.bsky.social
“Save the Freaks, Don’t Mine the Deep” shirt worn for #earthday.
Doofus on a bike (me) wearing a save the freaks, don’t mine the deep shirt that features a cartoon strawberry squid enveloping a ship.
April 23, 2025 at 12:31 AM
glennjaecks.bsky.social
I guess it’s snake season along the American River. I helped this lovely rattler to safely cross the path yesterday.
An asphalt bike lane with a ~70 cm western diamondback rattlesnake half way across the path, heading to the right.
April 22, 2025 at 2:17 AM
glennjaecks.bsky.social
Today’s ride to Folsom Lake included a bald eagle, more tadpoles in a different pond, some nice trails, and a plover.
A ghost pine with a bald eagle near the peak a light cloud on the left, blue sky in the background in the right A beige single track gravel trail winds into the background with green grass surrounding, and (blue?) oaks on the horizon. Below the levees at Folsom lake A pond on the left foreground, with tall grass on the banks. A. Barely seen plover at waters edge, trees in the background. A pond edge with duckweed? And tadpoles.
April 18, 2025 at 11:37 PM