Random Roadcuts #13: Geologist Explores Big Roadcut on Utah Highway 20 in Southwestern Utah
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- Опубликовано: 8 фев 2025
- Learn to "READ" the rocks with this innovative video series designed to help you learn geology. Join geology professor Shawn Willsey and investigate a random roadcut, make observations, and formulate basic interpretations. Here in Episode #13, we visit an intriguing roadcut along Utah Highway 20 in southwestern Utah. GPS Location: 37.96511, -112.46899
Geologic Unit: Bear Valley Formation and Mount Dutton Formation (Oligocene and Miocene)
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13:20 Those look like funnerels (I'm not sure on spelling and google has become useless) which indicate rapid hot ash deposition.
Thanks Shawn. I guess that ultimately, a big enough landslide surface, such as that one, can be categorised as a fault? The distinction between the two becomes blurred.
1:54 "discolored, rounded, concentric, blobs" lol. Great Roadcut! The power of nature is astounding. And your crime scene investigations are fantastic.
I love Random Roadcuts! It's so cool to see how you analyze something you're seeing for the first time and think your way through it. Thanks for making geology accessible and understandable for everyone.
My husband said you need to sign your drawings and auction them off as original Willsey art. I'm sure your hardcore team on here would bid on them - I would!
Shawn, you need a sandwich board sign set up alongside the road that reads " GEOLOGIST AT WORK....KEEP MOVING".
"Gsologist at work. Mind low flying rocks!"
'Honk if you like Geology!' @@zweispurmopped 😄
@@RWBHere That! Yes!!1! 😅🤗
Shawn- I was just at that roadcut a week or so ago! Same reaction as you: I just had to stop and do some roadside geology 😂
I interpreted this roadcut as a sequence of Tertiary volcanics:
1) the lowest white thinly bedded section = ash-fall tuffs (possibly into a lacustrine ie lake environment, or washed into and redeposited into a river bed) there’s a lot of glassy angular fragments in there;
followed by
2) the pinkish, massive very thick unit with angular, lithic clasts = pyroclastic or airfall tuff - as you noted this layer doesn’t have bedding, but does have areas of fining-and-coarsening (indicating changes in eruptive energy as the eruption progressed). The top of that pinkish unit is almost entirely free of clastic material. I also saw some large pyramid-shaped boulder-sized clasts that fell pointy-side down, suggesting air fall?
3) repeats of 1 and 2 going up section.
I’m not sure why the contacts are so even and flat, I’d expect a pyroclastic flow or fall deposit to have a lumpier (“more irregular”) surface 🤷♀️
Someone below referenced a UGS report, I’ll have to check that out!
My first impression is pretty similar. I've seen similar laminated, well sorted ash beds at Rainier Mesa, NV, where there are tens of meters of almost parallel fine ash beds, although occasional layers of larger lapilli are interspersed among them. The interpretation I'm most familiar with explains the fine beds as the collapse of a high-velocity Plinian eruption column, with the wind blowing nearly constantly away from the vent. The sharp contact at the top might be the caldera collapse stage of the explosive eruption catching up with the Plinian material while it's still falling. That road cut would show two similar eruptive sequences -- and there's a lot of stuff in there I have no clue about.
@@llanitedaveNice!
I love the Random Roadcut series.
This is literally what drew me to geology early in life, spending a lot of time in the back of my parent's vehicle as they traveled around the country and I looked out and stared at a LOT of roadcuts. I saw so many strange things and wished I understood what I was seeing. It's like a glimpse into the depths of time itself and we just drive right past it all the time.
The Utah Geological Society put out a paper two years ago that supports your volcanic & avalanche theories. Biek, R.F., Rowley, P.D., and Hacker, D.B., 2022, Utah’s ancient mega-landslides-geology, discovery, and guide to Earth’s largest terrestrial landslides: Utah Geological Survey Circular 132, 67 p.
It certainly seemed like a logical hypothesis. I'm glad even more geologists agreed with it, too - especially ones from a state geological group! 😁
I started watching you on January 14th when you were contributing to the Grindavik rift eruption. My wife and I really lucked out checked into your presentation live on RUclips. When you were trying to use the drone and then had the other guy fly it for you, we were watching when I noticed in the background the white plume of gases erupting from the ground closest to Grindavik. Since then we have been watching all of your updates and I have been watching your field trips and other programming including the interview that you had with Nick. All your programming is fun to watch. Shawn, thank you very much 😎 hope you're having a good time in Europe.
I also like watching your roadside cuts.
That's how I found him, too! I'm just not great at keeping up with my subscriptions. 😂
Road cuts for everyone. You were right on about the liesegang rings..i had to look it up. Definition included Iron oxide staining process in igneous rock deposits.
I'd never heard of this before. My initial guess was that it could be an endolithic fungal or bacterial growth causing the staining. I'd like to dig into it and see if it's a confined to a sphere or is a tubular channel
Love these road cuts videos! 1. Would you consider analyzing images or videos of road cuts sent in by viewers? 2. Would you consider analyzing Mars landscape images with your geologist eye for those of us who have little idea of what we are looking at? Thank you for all of the wonderful content that you provide!!
I do love these field trip videos and the road cuts are always great! One of my favorite short hikes where I live has nothing particularly interesting on it save one road cut that reveals the last several thousand years of history and tells a great story about the area.
My grandma was born in Marysvale, she’s 95! Love watching these road cuts so much.
I’ve been missing my random road cuts!
Thanks Shawn. This is one of your many fascinating educational geology videos. 254 like
A retired electron microscopist (semiconductor process development, not geology, alas) I find myself itching for a demonstration of how a geologist goes about systematically collecting and documenting samples for follow-up analysis in the lab. The companion episode would be the sample analysis, hand lens, stereoscope, polarizing light microscope, SEM, EDS, XRF, etc. What techniques and information does a geologist find most informative? Perhaps a series of lab visits and interviews with specialists in specific techniques…
You are amazing. Not only are you thinking, analyzing and talking to us, you are hiking and climbing all while filming. We are hooked. Enjoy your vacation. Adventure on.
Very interesting, thank you. Liesegang rings probably. The v sharp contacts are rather unusual? Maybe a catastrophic ash/pyroclastic flow could produce this? Would a heavier lahar produce a bit of deformation? Afraid I’m not very familiar with relatively young volcanics - instead much older Scottish geology.
Like this short format teaching. In future road cuts could you include your assessment of its geological dates?
Looking on Google Earth it looks like this roadcut was made by a series of four tiers of bore hole blasting to get down to the present road level. An incredible engineering feat. And the newer bore holes are certainly distinct from the old faults and cracks.
ありがとうございます！
I also am leaning towards the pink units with angular clasts possibly being lahars since there isn’t any visible baking (contact metamorphism) along those contacts with the aeolian deposits - as one would expect from a superheated pyroclastic flow. Excellent series Shawn! I am a consulting engineering geologist in Northern California and really enjoy these videos.
@shawnwillsey thanks for another excellent reading lesson! I'm a big fan of your Random Roadcuts :) And I love the volcano beanie ;)
Thank you for these delightful videos! We are moving to Southern Utah and I am learning so much from your educational videos!
This is one of my favorite little roads in Utah. The last time I drove on it, I was on my way to Calf Creek Falls and listening to "The Prestige" on audiobook. Sadly, I didn't know to stop and look at the road cuts back then...
Shawn the Explainer of Rocks..Fine info, speculation, analysis, interpretation ..
As an old guy of the 1960s I appreciate all of what you do..
For a good grin just imagine Jonathan Winters tagging along with Shawn for some added explanations..
Few will appreciate this image. I do.
Now I have to find and watch all the previous versions. New Idaho resident, finding the area near Nampa an amazing geologic treasure for retirement education. Thanks Teach.
So many different angles in this cut. Wonderful.
Very interesting Roadcut, randomly! Love ‘em.
Interesting roadcut, nice sharp contacts and pretty cold I'd say, quite a lot of snow on the other side of the road. Well done Shawn, another winner.
Love this series!!! Thank you!
Looks to me awfully similiar to roadcuts around the bay of plenty, NZ, where you have the pink mamaku ignimbrite unit (also well known for poorly sorted clasts of various sizes), contacting layers of airfall or windblown ash from local, coromandel or taupo (Oruanui/Hatepe) tephra. The concentric rings would also be pretty typical of an ash type deposit, where ash "hailstones" can form accretion discs.
Okay, I have a question but I'll preface it with a bit of unimportant information that creates context.
I started following Shawn in late November when we first started hearing about the potential for eruptions on the Reykjanes. I spelled that incorrectly, didn't I?
I'm on the older end of Gen X and have absolutely no education in geology beyond the occasional documentary and disaster movie.
As I'm watching this, I realize that not only am I speculating what the various rock layers could represent, but that I'm thinking the same things that Shawn is. I'm like a geology student at 55. I know "things".
Anyone else surprised at how much they are learning from Shawn while sitting at home with a cup of coffee in hand?
THIS is what the Internet is supposed to be. Humanity at it's best. Sharing knowledge for our societal and specie's growth.
Now I want to head out in my area with some like-minded and better educated geology fans and understand the geology in my little corner of the US. I wonder if the university here has anything like that. A geology club? Is that a thing?
Cheers, everyone.👊🪨🌋🌎
You echo my thoughts. I was very fortunate to have participated in his first 2-day YT Idaho field trip in October 2023. Shawn in person is exactly as you would expect from viewing his videos. It is fitting that he is bringing his knowledge and love of learning to people all over the world.
Very very interesting. I suppose the thicker single layer event was located at the base of a mountain where the alluvial fan from the event would be deepest. The wind formed layers were the only layers to house the darker concentric spots. It would be interesting to follow one into the cut for a few feet to see if it changes directions or stops.
Shawn, I love your Bryce Canyon knit hat!!
Thanks Shawn. Very interesting road cut and you always make it easy to understand what we are seeing. I'm looking forward to your next readout.
It was awesome seeing you on Scishow, I just now caught the episode!
There are random teal colored rocks in the debris at the bottom, around 10:00. Do you think that might be oxidized copper?
Great show! I grew up in Panguitch. Looks like you encountered the world's largest landslide, good analysis!
I especially like it when you hold the camera still while you're discussing its properties. However, I can and do stop the video so I can take a good look at what you're describing so it's only a minor inconvenience. Loving this series!
No other area along Utah highway 20 looks like this. A very "basin and range" area. Great visit to an unusual roadside
outcrop.
This is a beautiful road cut. I love the clasts and the mysterious dark circles. Looking at some of the rockfall you pointed out, I’m thinking you should be wearing a helmet.
The round blobs might be roots of some vegetation, later got mineralized.
Simply awesome. Thanks for a wonderful series.
Thanks for another one. Your discussion help me a lot when i see roadcuts. The very top is always interesting because it has not been cut so you can see looking around at the hills what might be under them too. My favorites roadcuts are those with volcanic dikes in them. When you see the volcanic spires in the hills around. You can imagine a large dike storm.
Love the bedding of the rocks.
Just back from a Utah spring break trip! Hoping you can do an episode on the Timpanogos cliff bands (north/east side). We're wondering why that mountain "looks" different than the others surrounding it. Thanks for all your awesome info!
Pause anywhere between 7:50 to 8:02 time and note the much larger circular grain structure in that sandstone. There's a radial structure revealed by the way the rock has been broken.
Thank you for scheduling this to post while you’re away! I love Random Road Cuts! ❤
Hi -- love these roadcut explorations. Did you ever figure out what those black concentric things were?
Shawn, I'm thinking that the odd circular features in the sandstone might be fossilized roots of dune growing vines or plants. Having traveled most of the West, these roadcuts have often made me wonder about them, so it's super fun to hear your interpretations!
Thank you, Shawn. I really enjoy this series. I was glad to hear that those two escaped murderers were caught in Twin Falls before they could kill anyone else.
Thanks for this video. I have wanted to learn about geology but am a lazy american. You are answering several questions ive had.
Thank you for another excellent video. We were on that road two days ago. I must have been napping and missed that road cut
Thanks!
Much appreciated
Thank you for making this video! Very interesting!
Cool road cut...those vertical fractures look like bore holes for explosives which moved rock for the road to be built.
Thx Shawn
Thank you , engineers and contractors did a clean cut there . Makes me wonder who they were? You explained very clearly how this earth was so violent once upon a time.
Absolutely fascinating!
One of the saddest Utah mining stories that I have seen is just 1.5 miles up this route from this road cut. They wanted to mine gold from this Breccia and ended up going bankrupt.
Love these random roadcuts!! I don't mind the traffic noise. I just ignore it and look at the cut.
Great video! I love looking at road cuts.
Fantastic Shaun, Really like the road cut series , Thank you
Thanks for your time. Love these vlogs.
Nice job fun stuff
The coarse zones could be volcanic mudflow (lahar) deposits.
There are incredible roadcuts along the 15 at the entrance of Virgin River Gorge in Arizona that I would love for you to do a video on! So many fascinating and spectacular roadcuts that I would love to understand!
I just went to google earth to look at that stretch of road. Amazing! I'd love to see that in person! Thanks for sharing.
I would live to see you do some analysis of the west and east mountains in Salt Lake County. I live near a mountain on the west side south of Magna that looks like a classic caldera.
Interesting that the heavier debris flow did not disturb the more delicate windblown cross beds. The deposit with the larger clasts looks like it might be a lahar deposit. The sharply angular clasts speak it very short transport distances, otherwise they would be more rounded.
The dark circular patches look like they might have started as partially-charcoaled tree branches. (Young sucker-type growth.)
From a distance, that pinkish deposit appears to have several layers (one in the middle much coarser). Interesting!
Thanks
Love it thanks
There's a road cut on UT 73, on the south side, as you head into Saratoga Springs from Cedar Valley/Tooele ... My guess would be a buried beach of Lake Bonneville - it's about 4400 or 4500ft elev. Would love to see your take on the road cuts throughout the Salt Lake and Utah valleys!
When I saw the breccia, I thought that it might be a lahar. (I also wondered if the lighter, striated material might be ash deposits, possibly subsequently windblown.) If that's what this dark layer is, I wonder if the initial lahar might have been followed by mud flows caused by subsequent rainfall, thus creating some "sorting" of the clasts. I was hoping for a guess as to how the layers managed to be angled and stacked as they were. What could account for that strange configuration?
Great find, Shawn! 👍
Ok Shawn, remember you are on vacation. But thanks for another random road cuts.
I'm wondering if the pink, massive unit could be a lahar. Think of a tall nearby volcano, snow covered or even glaciated. It erupts, we get ash fall, then the heat and shock and vibration of the ongoing eruption finally destabilizes the water saturated high slope, and we get liquified slurry sliding off the slope of the volcano bringing ash and volcanic rubble into the land below. It flowed into place in one catastrophic event, then set up like a weak concrete.
Although sections do look like breccia, I would call the entire section with clasts in it a matrix-supported diamicton, due to the variety of grain sizes and the fact that the clasts aren't touching each other, in general.
breccia layer might be massive lahar remnants?
interesting video!
For a musician this would be like sight reading. Performing a piece with just a few minutes to look at it before you begin.
Your hat is great! Is it a volcano with lava flowing into the ocean?
Exactly that
Hawai'i Volcanoes National Park
I like these shorter videos
Cool area! I wish I had your brain. I can't help but wonder the white layer sharing a common theme with the electrical double layer affect.
Are the 'mystery" round features cylindroidal or spheroidal ?
I wondered if they were concretions formed around organic matter similar to 'Boji Stones' ?
Very interesting. What kind of forces worked to create something like that
Can you do Sideling Hill someday!?
Many of us GeoGeeks have seen and swooned over it online.
And I traveled through it a couple times in 2021 (First saw photos in 2019) before realizing it was the same one!
I know it's way outside of your typical stomping grounds... But if you ever find yourself on the East Coast... It's in the choke point between the borders of PA, MD, and WV.
In fact, having seen it first hand and nearly jumping out of the car at highway speed to gawk at it, it definitely instilled a stronger interest in me in Road Cuts!
(No! I did not try to exit the vehicle while moving...lol)
Just putting into perspective how well it grabs one's attention and fascination 😅
What REALLY makes it pop more than anything (besides color contrasts) is the obvious folding of the layers...
(it's also hard to find decent or interesting information about local geology in western and Central PA)
Hey, Shawn. How are things in Idaho? I'm from Southeastern Utah myself. Have you ever seen the massive cut on CA State HWY 14? It's on the Northbound side, or east. It clearly delineates the San Andreas Faultline. This is just as you are about to get to Palmdale, CA.
Also, if you drive down the Pearblossom Hwy going east towards Interstate 15, there another exposed faulting for the San Andreas. It's a place called the Devil's Punchbowl. That place awesome for hiking and seeing all the sandstone every which-way.
How does the drilling and blasting for road construction impact the remaining rock structure? Maybe adding to fissures or creating new cracks?
"Rounded concentric blobs in the rock." Those are wild. Would the processes be similar to those associated with Moqui marbles? Otherwise, my guess is that "it's aliens."😁
Are moqui marbles smaller? Those looked so much bigger than any I’ve seen
@@bky312 The one's I've seen are smaller, but my comment is about the processes producing them being similar. These don't look like moqui marbles to me but the way Shawn described them made me wonder if similar processes were involved.
Moqui marbles can be large in some zones. I've come across some examples in the Navajo SS near Zion that are 20-25 centimeters on the long axis. Since they form in higher permeability layers they grow faster along that axis than perpendicular, so the larger ones are usually asymmetric.
There is a similar process going on here, but these are at least isotropic if not spherical, so they see to grow independent of gw flow asymmetries. Did they all seem to be very similar in size? or did they vary over some range? @@bky312
I love the roadcuts! I would go nuts looking at that. On my phone, it mostly looked pink and green. Is that color the actual color or just a video artifact? Would the darker clasts be basalt?
These explores are interesting and enjoyable. Glad all this massive material migration is not happening today, we would never find a peaceful place to settle. Take care. Are the blobs decomposed tektites?
Thank you, but you left us hanging. Did you have a thought on all that, volcanic? Ash and a Tuff flow or ??? stay safe ALL
@shawnwillsey I am curious, I don't know how roadcuts are made, I assume explosives and some huge jackhammers. Is there a possibility that the road cutting creates some of the lines, marks, fracturing or other effects that can confuse the interpretation of the geology?
I'm not a geologist but after watching your videos, this deposition seems to me volcanic in origin.
Just thinking that maybe some of the rounded items may be fosles?
I'd love your view on American Fork Canyon or Provo Canyon. Or the big copper mine in west Salt Lake Valley.
There are roadcuts at the base of the mountains below the copper mine that look exactly like ones you'd see on the big Cascade volcanoes.
@@marknovak2413 You mean on Butterfield Canyon Road? I know the mine is there because of volcanism, but I didn't know you could see it so clearly.
Whatever road it is that runs N-S along the base of the Oquirrhs.@@Xukaiwen2
Have you searched Shawn's library? He has videos on many Utah locations. Might be some overlap of interest.
Bottoms of the blast holes are the marks.
Maybe Orbicular granite?
Is the bedding surface in its natural repose or has it been tilted