The Great Unconformity: a geologic feature spanning 1.3 billion years high in the Wasatch Mtns, Utah
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- Опубліковано 14 жов 2024
- The northern portion of Utah's Wasatch Range proudly displays one of the great geologic features in western North America - the Great Unconformity. This feature is typically buried miles below the surface but is exposed in tall, young mountain ranges (like the Wasatch or Tetons) or deep canyons (like the Grand Canyon). The unconformity is a distinct contact between dissimilar rock units and represents a whopping 1.3 billion years, nearly 30% of Earth's entire history. Here geology professor Shawn Willsey treks up the steep mountain front near Willard Canyon to show you the rocks on either side of the unconformity and explain its significance.
GPS location: 41.41166, -112.01365
I love doing these videos and will continue to do so but if you want to provide support or much appreciated gas money, you can send support via Venmo @Shawn-Willsey (be sure to put two L's in last name)
or PayPal:
www.paypal.com...
or a good ol' fashioned check to this address:
Shawn Willsey
College of Southern Idaho
315 Falls Avenue
Twin Falls, ID 83303
I love geology and your enthusiasm when informing your audience. Thank you.
I agree! I have always enjoyed Geology as a kid and as an adulr.
I agree as well! Now that I'm retired, I finally have the time to learn more about geology, and these videos are very interesting and helpful. Thank you!
Hey thanks. These are easy to do as they are essentially an extension of what I do on field trips with students. It's been fun to share and connect with so many folks. Keep watching and learning.
Willard Canyon enters my bucket list. Thank you Shawn.
For those out in the Las Vegas area, The Great Unconformity is also accessible right off of Lake Meade Blvd. as it begins to make its way over the hill to Lake Meade, on the south side of the road. There is a sign there, pointing it out.
Thank you Shawn. As a finance executive for a number of Australian resource companies, I was always impressed with the presentations given by our exploration geologists. By subscribing to you presentations I can continue to be impressed in my retirement.
Thanks for watching and subscribing, Barry! I like to think that most geologists are good storytellers/presenters.
I saw the great unconformity in the grand canyon. This is way more impressive. Thanks.
@@jimmccready9487 Glad you liked it. I agree that here in the northern Wasatch is quite impressive.
Pretty amazing being able to actually touch the conformity and bridge it with both hands, such a clean sharp line. Massive Quartzite deposit !
A great video made in somewhat difficult conditions!
I’ve hiked exactly there and also above Honeyville to hunt trilobites. Great specimens.
Shawn, thanks so much for making this video! I grew up in Willard and spent countless hours hiking all over those mountains and though I've heard of The Great Unconformity I had no idea there was such a good example of it literally in my backyard. This gives me an even deeper appreciation of that area that is so near and dear to my heart.
What a great area to grow up in! I went to HS in Layton and college at Weber State so this area was my backyard for a while too. So many awesome geology stories. Be sure to watch the one I did from near Willard Peak: ua-cam.com/video/1PkKDW4fKeY/v-deo.html
Thanks! I felt as if I were there and listening to you directly standing right at the edge of the cliff. Somewhat ominous sky fitted to the feeling of jumping 1.3 billion years from grey to cream.
Actually scared me in a couple of the shots! I hope it looked more precarious on film than it actually was.
Another good show Shawn! Thank you for sharing your knowledge with us brother. Educational and entertaining. Keep the videos coming! Jim
Thanks for watching Jim. It's fun to share and connect with folks. Look for more soon.
Cool! I’m heading to Logan next week, will keep my eye out.
This is one of the most interesting videos I’ve ever seen. I love learning and this geology video is the best. Thank you.
So, long story but I became a geologist when I took intro to geology at BYU and touched a billion year old rock at Rock Canyon on a field trip. I left BYU (was not meant to go there) and finished by degrees at UTEP. We have the unconformity in El Paso and 500 million years of missing time is one of the most intriguing things to me still in geology. You got a new sub today. Look forward to more content.
The reason it’s missing is because it’s nonsense without evidence. The earth is only about 8000 years old.
Carl, great backstory and welcome aboard. Have fun looking through past videos as well as looking for new ones dropping soon.
Love this! Not sure why the algorithm picked this video for me, but having grown up in Box Elder and moved away long ago, it’s wonderful to learn something fascinating about these mountains I saw everyday as a kid.
Welcome aboard!
Very cool. Thanks for sharing that spot.
1.3 billion years is really hard to wrap your head around. I love driving by the Wasatch range. Great to learn about some of the history I'm always curious about. thank you!
Thanks for watching and learning with me. So much awesome geology in the Wasatch.
Thanks for sharing this portion of the fascinating story of earth's past. Now that I've found your channel, I will very much enjoy catching up on your expeditions. Subscribed.
Awesome news. Welcome aboard. Enjoy the past videos on my channel and look for new ones soon.
In Western Colorado there are the Black Canyon National Park and Colorado National Monument, both of which display the Great Unconformity in exquisite detail. In Colorado National Monument, there is a basement that's 1.8 billion years old, intruded by granites that are 1.4 billion. Then there's the Triassic Chinle Formation on top of that, illustrating a mere 1.2 billion years of missing time, which I find amazingly close to your 1.3 billion in the Wasatch.
A great video on a really interesting topic! You do a great job making geology more accessible to those without a geology degree in these videos.
Thanks for the kind words, Austin. This is a fun outlet for me and I love sharing Earth's stories with folks.
THANK YOU! I went to USU and often drove past this section of mountains. As a kid on the east coast, I always imagined all the "Rocky Mountains" would look like this section. Always one of my favorites. Thanks for the video!
You bet. It really is my favorite, scenic section of the Wasatch. Glad you enjoyed it.
I remember noticing the Great Unconformity while passing ❤on I-15 a few years ago. It is quite striking. Sadly, I had to put my eyes back on the road and the question faded away. Thank you for taking the sweat hike to explain it. It is also good to understand the gravel imbedded rock in my front water garden in Grantsville. What a fine world to live in! It is full of stories of the old and new, sound and silence, black, white, and every color in between. It is quite a magnificent creation when we start asking questions. For me, the temples along the Wasatch Front also provide some awesome context.
Really interesting - thank you for the lucid description. Something I've wondered about since seeing that in Grand Canyon
Thank you for the informative video, It is good to see lots of people really enjoying Geology.
I am Miner ! I look for Pocket Gold in my region. Have found some spectacular Rock Deposits in which I display in my Restaurant. But unraveling these Rock structure’s and identifying them is really what it’s about for me. Ty just found your channel and love your take on it for the common person. I’m from the Klamath mountains of Southern Oregon so the Geology is unbelievably complex with faults folding an covered by vegetation. Makes for a Awesome challenge.
Great vids. I'm a retired geologist living in Prescott, Arizona. We have a great exposure of the Great Unconformity here between the Tapeats and the Proterozoic basement rocks on Route 89A going up the west side of Mingus Mountain. I love pointing it out to visiting guests. Keep up the good work. We love going thru Idaho to visit son in Bozeman, MT.
Greetings. I went to grad school at NAU so I know that area well. US 89A over Mingus is a winding road but very scenic. Thanks for watching and learning with me.
I LOVEEEE that mountain range, I love looking at it when I drive past it. Thank you for explaining about the different layers. So awesome! ❤
Your lecture reminded me when I was exploring South section of our CENTRAL PARK NYC...bed rock there is amazing! Huge mountains were there when two tectonic plates collided eons ago to form the foundation of MANHATTAN.
Hey Shawn, I have been loving your videos! On a topic unrelated to this video... As a local to SE Idaho, I would love to see your breakdown of the Menan Buttes north of Idaho Falls, I have always found the limited amount I know about the geology of them fascinating. On hikes up there, I have also noticed what appeared to be sandstone or some other sedimentary type rock up at the top along the south part of the rim that I have always been interested in. Also the island park caldera could have some interesting geologic history.
Hi there and thanks for watching and learning with me. I wrote a book called Geology Underfoot in Southern Idaho and dedicated a full vignette to the Menan Buttes. It would be a great site to do a video as it has a cool story. I will try and make this happen soon. Thanks for the suggestion. The rock near the south rim is tuff but it contains an alteration mineral called palagonite which is yellowish. It forms when basaltic lava and water interact. You can see small rounded river gravels imbedded in the rock. Such a cool spot!
Wow, interesting stuff and presented in a useful way. Thanks for sharing.
Great film, I got dizzy from here.
Camera quality, photographer, or my waning balance?
Thanks too for the clear explanation
I remember seeing what I believe was the same unconformity in the Wind River Mountains when I was attending my geology field camp. I also saw it at the bottom of the Grand Canyon. Just amazing knowing the history and actually being able to put my finger on the contact!
Thanks Shawn for another great video "field trip!" I've really enjoyed learning about the geology of the Utah/Idaho region through your channel. The Intermountain West geology is so fascinating that Earth Science has become a real passion and study for me. Soon, and with a bit of regret, I'll be moving from the mountains to the flatlands of the Great Lakes region -- a whole different type of geology -- no mountain building events, volcanic fields or an active 800 mile earthquake fault system ... though I'm sure the geology will present itself and I'll find equally fascinating geologics all around me. Maybe the Mid Continent Rift system for a start! ... lol! Happy geo-explorations!
Thanks for watching and learning with me. Even with your move, you can still enjoy some western landscapes and geology with these videos. Good luck on your move.
Thank you, I automatically subscribe your channel, btw.. why youtube is so late recomend this great channel?
Thanks for subbing!
I enjoyed a few hikes up Ben Lomond and noticed the fun rock differences in that area. As you panned over the Great Salt Lake and Willard Bay, I think Promontory Point was visible. Just to the north of it was then Thiokol, where the first space shuttle motors were developed, built, and tested. During the first test, seismic activity was noted on the Wasatch Fault, but the NASA contract was firm even though USGS asked that the testing be stopped. I hope some day you can do a presentation of the Wasatch Fault and its connection to Yellowstone. Timpanogos Cave is such a fine place to see the fault's vertical displacement. I've heard that the geology building at Weber State is built atop the fault itself. Fun connecting times.
Been working across the lake out near Wendover in the crater islands. Looking at Devonian/Cambrian limestone intruded by Jurassic granite. It's been a goal of mine to do some videos like this with some brief diagrams, but I didn't think I have enough credentials. Good video
Interesting. A story on the coal ribbons along US 6 south of Castle Gate UT would be nice.
Cheers from a fellow Brazilian geologist!! What a great UA-cam Channel u have.
Thanks for watching and learning with me. Hope all is well in Brazil!
Wow so cool! We climbed the most prominent spire to your south and I remember climbing up and over the black rocks and the transition to the lighter colored rocks. At that time I had never heard of the Great Unconformity but some how knew it was important as it is such a dramatic change in the rocks. What a beautiful place and the view back over the Great Salt Lake was pretty cool with the sunrise. It took two times to get up that. How was your down climb ours was pretty sketchy :)
Wait. So you can see the dark basement rocks on the north side of Willard Canyon? It looked like they were covered both on Google Earth and on the ground which is why I climbed up the south side of canyon. Or maybe you are referring to the gray limestone above the quartzite? Going down the talus was definitely a little tricky with lots of teetering blocks but it was much better than the slog through the brush.
Great exposure of the Great Unconformity. In southwestern Utah old highway 91 goes right over the Great Unconformity in the Beaverdam mountains, a bit easier access, but not as pronounced as here, some delightful migmatites in the Precambrian layers as a benefit!
Yes! I have been there as well. That area of Utah is so fascinating as it lies near the boundaries of several geologic provinces. Basement rocks there are about the same age as those in video. Great stuff!
@@shawnwillsey I retired in this corner of Utah ten years ago, and still enjoy the amazing variety of geological features! Thanks for making and posting your videos. I strongly believe in the importance of making science accessible to a wider than pure scientist audience. I do admire your free flowing style, geared to an audience with a somewhat shorter attention span!
@@ThomasEckhardt You nailed it on all fronts. Thanks.
Thanks so much for sharing, you've sparked an interest over here in Taiwan! Are there any books you'd recommend for a hiker who wants to better understand the story the rocks tell as they wander up a mountain?
Hello in Taiwan and thanks for watching and learning with me. Hmm. No books immediately come to mind. I think a basic Physical Geology textbook but be a good resource. If you are into US national parks, there is a book called Geology and Landscapes of America's National Parks by Osleger that might be good too.
I love northern Wasatch. Good hiking. We also have a great unconformity down in southern NM. Mud mountain in TorC.
Hi Shawn, thanks for pointing this out. I worked in the San Juan Mountains of SW CO looking at 1.75 Ga metavolcanic rocks now gneisses and amphibolites overlain unconformably by 1.65 Ga quartzites and slates that are folded and thrust faulted. There was a second "great" unconformity above these quartzites and slates with Cambrian sandstones through Pennsylvanian limestones on top of the exhumed Pennsylvanian paleotopography. This is visible along Lime Creek off of US 550 north of Durango, CO near Molas Pass. Another example can be found in Uncompahgre Gorge just south of Ouray, CO where the folded Proterozoic quartzites and slates are overlain by Paleozoic limestones. I"ve published several scientific papers on this area.
I'm intrigued by the Cambrian Quartzites and conglomerates above the 1.8 Ga gneisses and amphibolites. Reminds me of the San Juan mountain's rocks in the Needle Mountains area.
Another amazing video! I live in the area and am mesmerized by that formation! Appreciate the analysis!
Awesome! Is the missing material from the unconformity represented in other areas?
Yes, but not completely. In other locations in the region, there are rocks between 1.8 billion and 500 million years old, but nowhere do you have a complete record during this timeframe.
I love hiking up Willard Canyon and some of the smaller canyons in the cliffs nearby, especially when water is flowing. There’s an old C.C.C. trail to the south of the waterfall zig-zagging right up the cliff. It’s been restored somewhat since my dad first showed it to me when I was younger.
Great explanation!
Being from Colorado, I am more familiar with the Great Unconformity in various locations around the state. I was not aware that it also appears on the Wasatch front.
One of the easiest and best locations to observe the Great Unconformity is along i-70 in Glenwood Canyon. The dark ancient rocks there are overlain by limestone layers which contain caves and other Karst formations. Not being a geologist, I don't know the time difference or whether the limestones are metomorphic. But the demarcation between the rocks is clear and can be observed in multiple locations through the canyon.
Another great location to observe the Great Unconformity is at the Uncompahgre Plateau near Grand Junction. You can hike down (or up) to the time gap (or drive past) in several locations within Colorado National Monument, in several canyons draining the plateau, floating the Colorado River across the state line into Utah, and to the west at Black Canyon of the Gunnison NP (the gorge is cut into the Pre-Cambian rocks but overlain by younger rocks). In the Uncompahgre Plateau area, the Great Unconformity is very beautiful, with the very dark (black) older rocks overlain by very red shales(?) of the Chinle Formation. The Chinle and the other sedimentary rocks above it form traditional desert canyon topography with sandy and rubble filled streambeds andgreat sandstone cliffs, while the small streams have sculpted narrow inner canyons into the dark Precambrian rocks with waterfalls, pools and smooth rocks.
One other thing, of which I am proud. We were recently in Albuquerque and took the tram to the top of Sadia Peak (highly recommended). About 2/3 of the way up, I looked out and pointed to a demarcation in the rocks and told the tram operator, "Great Unconformity". He was kind of amazed that I observed that, as was I. I guess I have seen it enough times in various parts of Colorado so that I can instantly recognize it. I was not expecting it in New Mexico, or that far east. It must really be quite extensive and found in many places throughout the western U.S. I hadn't really thought about it, but I guess it exists within a couple miles of my home in Littleton, CO and all along the Front Range of Colorado where Pre-Cambrian rocks of the foothills are overlain by sedimentary rocks such as the famous Fountain Formation (Red Rocks Amphitheatre) - it's just that the line of demarcation is not as distinct as observed in some of the western canyons.
Thanks for your video. God bless.
I really gotta go to Utah. Every time I see a picture or video from there it’s just absolutely beautiful.
Hey Shawn love your videos man. Was wondering if you could do one on the Farmington canyon Complex?
Thanks for watching and learning with me. I will put this topic on my list. The Farmington Canyon complex varies a bit from place to place but I know of some great outcrops and exposures I can do.
Well hello sir! I could listen to Geologists forever. Looks like you are one of my kind, going the extra distance for rocks. Sub'd
Awesome. Glad you found this. Thanks for watching and learning with me.
Such a span of time… it boggles my mind trying to imagine this. Its amazing what stories rocks can tell
Very cool to explain the earth we see everyday but don't really know how it's formed, good to physically show the terrain and talk about how it formed, excellent learning program, thanks for your efforts.
You bet. I appreciate you watching.
That was amazing I’m on summer break and it felt like I was in class thank you!
Awesome. Never stop learning (even on summer break) :) Thanks for watching.
Fascinating. Thanks.
Beautiful video.
I always wondered what made those certain rocks so old looking and craggy. Some rocks I see are huge, with deep, old pitting just like these. It makes sense they came from so far down.
Thank you for the lesson and for the beautiful scenery. Glad to be a subscriber.
Thanks for the sub! Glad you enjoy the content.
Enlightening
This is great! Thanks!
Love learning about all the geological processes that make up our region. No spills over the edge though! You know what they say about geologists having rocks in their heads! 😅
I was just there in May at the KOA down the hill. Beautiful features and out croppings.
Superb, got my subscription, cheers to you 🤟
Awesome. Welcome aboard and enjoy the existing videos and look for new ones soon.
Fascinating, thanks. New sub
Awesome. Thanks for watching and learning with me. Enjoy the existing videos here and look for new ones soon.
@@shawnwillsey love the views and history, fascinating stuff. Thanks
Thanks Shawn, love your explanation ....
I'm late to the party, I know. When we went to see the total solar eclipse in 2017, I saw this spectacular front of the Wasatch above I-15 in the Willard area, and I took shapshots from the moving car. I hoped to find a good guidebook or description of what I was seeing, but I found almost nothing online -- which surprised me. Thank you for this explanation of at least one aspect of the mountain front.
Hi Shawn! We really enjoyed this video we've looked at this section for a long time trying to figure out the stark contrast.
What is the layer above the sandstone? Because you have the metamorphic basement rock, then the sandstone, then it goes back to another darker section of rock.
Thanks for the information!
That quartzite layer goes all the way into Washington and Idaho.
Question: (different topic but this location is just right for it) You mention the Wasatch “front”. Recently I learned the term “break in slope”, which I’m guessing can be applied to a front. West of you the terrain is dramatically flat. You mentioned uplift of course.
My question is, is there a north-south fault at the base of the front? Is there always one, e.g., along the Front Range at Denver?
Thank you so much for these informative mini field trips!
Great question. Yes, the Wasatch Mountains (and Wasatch Front) are bounded by the Wasatch Fault, which runs along the western base of the mountains from southern Idaho into central Utah. Thousands of earthquakes over the past 20 million years have incrementally pushed the mountains up and dropped the valley down, creating the scenic skyline and imposing massif of the Wasatch. The Wasatch Fault is still active and capable of generating quakes up to magnitude 7.5, presenting a real hazard to the millions that live along the Wasatch Front.
Colorado geology is not my strongest suit but I'll take a stab. The Front Range (and Rockies) were uplifted during the Laramide Orogeny (a mountain building event about 70-50 million years ago) along faults along the east side of the range.
@@shawnwillsey Thanks for the thorough answer. I'm gonna infer that as a general rule a fault is involved in such an abrupt topography modification (break in slope). Interesting that the Wasatch Fault is still active.
@@mrfranksanYes, large faults often produce a pronounced break in slope but other factors can produce similar results such as erosion and differences in rock types (resistant rocks vs softer rocks). Basically the entire Basin and Range (from the Sierras of CA to the Wasatch of UT is still very seismically active. The most recent notable fault in UT was the April 2020 quake near the SLC airport. All part of the active E-W extensional forces still acting on the crust in the region.
Nice to see that over 12,600 other people were interested in this.
really spectacular. i remember hiking down into the Grand Canyon and seeing for myself the great unconformity and trying to get my head around the timescale, something a person cannot do, try as he may. You have given me one more must see destination! i'm curious as to the forces that brought these rocks to the surface and tilted them. Was the continent you mentioned that collided with N A Rodinia Are the Mojave and Yavapai orogenies in any wise implicated here, or is that another story entirely?
Thanks for watching. Yes, humans are ill-prepared to wrap their heads around time scales of this magnitude. The basement rocks (1.8 billion years old) were at the surface about 500 million years ago when the Cambrian quartzite (sandstone) was deposited. Then these rocks were buried under 1,000s of feet of sedimentary rocks. The basement rocks were most recently exposed at the surface by uplift along the Wasatch Fault which also created the N-S trending Wasatch Range over the past 20 or so million years.
The continental collision that produced the basement rocks was not part of forming Rodinia, which formed about 1 billion years ago. Instead, it was part of forming the supercontinent Columbia (aka Nuna). Accretion of the Mojave and Yavapai provinces to ancient North America occurred about the same time and is part of the story of building Columbia/Nuna.
@@shawnwillsey I'm wondering if you might recommend a good textbook on Historical Geology. i've been searching about. i'm looking to buy HISTORICAL GEOLOGY by Reed Wicander. are you familiar with this? also, i've read several books on the geology of North America--Ancient Landscapes of America, by Ronald Blakey and Wayne Ramney, The Evolution of the Geological Plateau, by Willard Fillmore, and some others. Are there any books about the geology of NA,--specifically the western USA--that you would recommend? Thanks
@@brentweissert6524 Hi Brent. I use the Historical Geology text by Wicander and Monroe in my Historical Geology (GEOL 102) class. It's solid in every respect and you can probably find a used or older edition on the interwebs for cheap. It provides a good overview of Earth history and focuses on North America. The other two books you mentioned are very good as well. Other titles that come to mind are state or region specific. Another good option are the Geology Underfoot and Roadside Geology series by Mountain Press publishing. I wrote Geology Underfoot in Southern Idaho and co-wrote Roadside Geology of Idaho. There are other titles for other states. These are nice because not only do you get the geologic history, but also places where you can see the evidence yourself. I'll check my office later today and see if any other titles pop.
@@shawnwillsey thanks for getting back to me. yes, i love those roadside geology books and are a must take along as i travel.
I'd love to go on a road trip through the Rockies with a guide like this
There will be a test every week.
Being from Germany I probably will not get to visit this unconformity in person. But now that we have Google Maps I can zoom into the aerial images of where you are standing and see it for myself.
I love the technical achievements of today.
It looks exactly as one could descibe. Really old rocks being covered and being pushed up along the top of the much older rock underneath. The newer rock covers the old like a veil in the wind. Not so uniform across either because I'm pretty sure
there was a great inland salt water sea here for millions of years. It is amazing how much higher the land got after even
more millions of years afterwards.
GREAT Video and thank you for explaining...
Question: are there Quartz Crystals inside of those rocks?
Also.. did I actually see Seashells in the " Pebbly" looking Rock?
Thank you again for the uncomformity lesson.. its SO HARD to wrap my head around the AGE of these Rocks!
Mikeyo-NJ😎
No quartz crystals in this unit. Crystals require space (voids) to form and are therefore somewhat rare in most rocks. The quartz in the quartzite is grains of sand. I've never seen any shells in these rocks but the unit above (Ophir Shale) has yielded trilobites and other fossils. It also has trace fossils (burrows and trackways) which I featured in another video: ua-cam.com/video/WlfA0jnUySg/v-deo.html
I don't know I you have done anything els3 on the area, but the whole of the ogden end of the watch is amazing. Would love an indepth view on the area from you.
I have several other existing videos from Ogden area so look through Northern Utah playlist
Sometimes a formation pinches out against an unconformity and forms an hydrocarbon trap. These can be some really big oilfields. They are kinda hard to find but there are more to be discovered.
Shorelines of sand deposits and gravel layers deposited above it by river flow are 1/2 mile above visible farm fields that are higher then current sea levels .
I've straddled the same unconformity in Broken Hill, Western NSW. totally awesome. (The basement rock there is pretty messed up - schist to gneiss - I found a pegmatite intrusion that was folded in three different directions...)
Do you have a comment on the new crack in Turkey after the recent earthquake? It has amazing geological features. A unique opportunity to experience an active fault breaking layers of rocks. Beautiful! Do not misunderstand what I refer to, the pain, suffering of all is a tragedy to humanity and I am deeply sad.
There's another example of the Great Unconformity (though less dramatic than this one) behind Boulder, CO, where the Fountain Formation (of which the Flatirons are made) lies on top of the bedrock Boulder Creek granodiorite. At Contact Corner on Flagstaff Road, you can actually touch the contact, which spans 1.3 billion years, as it does here...
Very neat. When I was a kid my pops told me that the color difference was the wasatch fault. I was in middle school before I reasoned that it wasn't the case hahah.
Yeah, dad was a little off there but the reason these rocks are uplifted and displayed so prominently is totally due to the Wasatch Fault.
Great info. I love your videos.
Glad you like them!
I've seen those mountains but never walked them, really interesting. BTW I expected to see you disappear any second.
Ha. There was a big ledge below me so not as spicy as it looked but still very steep area.
Do we know where all that eroded rock ended up? Or is there simply no way to know?
Shawn, it would be interesting (to me, anyway) if you could describe the Wasatch Mountain front as it is visible from I-15 in Willard. I appreciate the close-up analysis. But I took photos of these mountains from I-15 when we were heading to Idaho to view the eclipse in Aug 2017. I was left to wonder what I was seeing in the photos.
I know that mountainside well so ask any questions you have.
@@shawnwillseyI don't think the message function of UA-cam allows me to attach a photo.
@@shawnwillseyLooks like I'm going to have to verbally describe the photo I wanted to share. Also, I'm colorblind to the extent that "pink" is usually a non-color to me. I'll never refer to anything as "pink," except maybe Barbie's car. Very prominent in the mountain front, as seen from I-15 in Willard UT, is a light-colored layer. It has some sharp peaks that block parts of the mountain front above it. It looks to me like it's stratified, and, therefore, I conclude that it's a sedimentary deposit, perhaps sandstone. Perhaps this is the sandstone in your video. Above the "sandstone" is a dark layer that forms the crest of the mountains. I think it's "dark" partly because of the vegetation, which appears to be pines and/or junipers. Limestone? Below the very prominent light-colored layer is a thick grayish layer. The "grayish" aspect changes from north to south -- lighter in the north, darker in the south. But that may be an artifact of the lighting (afternoon sun, no shadows). Is this the ~2.7 billion year-old basement of Rodinia? The south end of this "grayish" layer, as seen in the photo I wanted to share, appears (to me) to be crossed by pegmatites. Below this lower dark layer are enormous slopes of talus, extending to the valley floor. OK, my question to you: the contact between the prominent light layer and the lower grayish layer -- is that the Great Unconformity?
@@curtiscroulet8715 Can you email me a photo and I can annotate it with some info? shawnwillsey@gmail.com
Will do.
This is visible just outside Las Vegas, on Lake Mead Blvd, on the way to that lake.
There used to be a big display about it, but it was destroyed by vandals.
That’s really interesting. If that’s the spot I’m thinking of I have seen it a number of times while traveling on I15. I always thought it was fun to look at the up tilted band of rock on the mountain that looks all wavy until you view it from the north around where the port of entry is on I-15 at mile marker 361, from there you can see it is one lined up band going up the mountain.
Shawn, did you know all of these areas in Willard are now blocked off from public access? They are destorying this whole mountain range from open-pit mining. Is there anything that can be done to protext this geological history?
Hi Shawn. As a Less than Layman, what is the causation of the sedimentary stratification. What took place that separates the sedimentary layers so that the deposits are not just a continuous layer. Is it just suggesting seasonality? Also have you read the hypothesis that glacial erosion during the Earth Snowball period wore away the deposits and that led to the Cambrian Explosion?
awesome thank you
You describe the older metamorphic and the younger quartzite rocks/layers, but you didn’t answer the questions as to why they are adjoined or what happened to the 1.3 billion years that separate them. I would love a video that answers these questions. Thanks.
Yeah... kinda missed the most important part of the deal!
Yes, sorry. Not all geologic events are recorded in the rock record. In this case, we have the basement rocks (the metamorphic rocks) which formed deep below the surface overlain by the sand layers (quartzite) which were deposited at the surface. The unconformity between the two represents a whopping 1.3 billion years. Getting those deeply formed basement rocks to the surface with uplift and/or erosion still takes a long time, which may account for a solid chunk of the intervening time but not the full amount. If this location was our only data point, that would be all we could safely conclude. However, regionally we have outcrops of other layers or units that are younger than the basement rocks and older than the Cambrian quartzite. Unit such as the Kelly Canyon Formation, Perry Canyon Formation, and Big Cottonwood Formation. These are exposed at various locations like Antelope Island, Willard Peak, and Big Cottonwood canyon. Basically, they include coastal mud/sand deposits, glacial till, and other material. These were likely deposited near Willard but were eroded and not preserved. Hope this helps a bit.
The Great Unconformity can be observed on the west side of Frenchman's Mountain in Nevada near Las Vegas.
Yes indeed although the place I went to years ago was a little trashy along highway and more subtle in terms of juxtaposing the two different rock types.
@@shawnwillsey Yes, years ago, however in recent times there has been major cleanup performed. A better location is approx. 1/5 mile to the south. I have pics and video if interested.
@@rogercotman1314 Good to know. I'll stop by next time I am in that area.
I will need to look next time. I drive by at least twice a week.
Very interesting, thanks.
Did I hear you say that the Precambrian rocks at this outcrop were 1.8 Ga or Archean Eon?
Yes, these rocks are part of a group of high grade metamorphic and intrusive igneous rocks (they formed deep underground) called the Farmington Canyon Complex. They are 1.8 billion years old and from the Proterozoic Eon of the Precambrian. If I said Archean, then I misspoke.
@@shawnwillsey - Thank you for the reply.
Thanks for producing this! Climbing alone would have been difficult and you are still understandable above the wind noise. I'm interested in why early on you didn't mention that quartzite was a metamorphic, the other metamorphics, though, being well discussed. This seems to be to me, as a non-degreed, non-academic, to be a logical point to mention how sandstone can alter to quartzite. To me, not knowing anything, "blocks of sandstone" immediately calls up all things sedimentary, that rock type seemingly out of place on the hill. But knowing that quartzite is a metamorphic, well, everything now seems consistent. Again, thanks for all your efforts on educating people on the natural world.
Thanks for watching and your comments. Quartzite is a bit of a problematic rock term. It is classically identified as a metamorphic rock. Geologists define two types: orthoquartzite and metaquartzite. Orthoquartzite is what is featured in the video - a quartz-rich sandstone that has been slightly metamorphosed (low temps and pressures) such that the quartz grains are fused together. An easy way to distinguish an orthoquartzite from a sandstone is by tactile feel: a sandstone will feel rough (like sandpaper) because the rock fractures around individual quartz grains. Whereas with an orthoquartzite, the sand grains are fused so the rock fractures through the grains, producing smooth to the touch surfaces. Orthoquartzites often still retain primary sedimentary features like bedding and even fossils. Metaquartzite is often only identified using microscopic analysis where textures and other features provide evidence of higher temps and pressures.
The main point of the video is differentiating the two rocks: one that formed miles below the surface due to high temps and pressures and the other forming at the surface on a beach.
@@shawnwillsey Thanks, Professor, for the comments. I respect your time. I live in the SE corner of the Death Valley Region in Pahrump, Nevada and it seems that, aside from limestone and different kinds of breccias, that quartzite rules the world here. Today I was rockhounding in the Campito formation with its quartzite and we also have the Stirling quartzite and, I think this might be true, the most noted, that being Zabriskie quartzite. So, anything and everything about this rock I enjoy reading and learning about. Again, thanks, and I will be studying your remarks. Thomas
@@thomasfarley Yes quartzites are a common rock type in the western US from the Paleozoic for two reasons. 1) sand deposition along the coast of ancient western North America (which shifted location as sea level rose and fell) and 2) quartzites are very hard and resistant to erosion so they are quite persistent.
@@shawnwillsey Thanks, again. I'm learning from this discussion and I am sure others are, too. Thinking this over, it would seem a metaquartzite would seem to be v. difficult to teach in a class, and 2) I'm confused about a metamorphic forming at the surface of a beach. To me, a metamorphic occurs over time by things like pressure and heat. Wouldn't a quartzite arise or be a product of buried sediment? Or, are you saying that the metamorphic process _begins_ at the top of a beach and eventually results as more and more layers accumulate? Sorry, I'm a business writer and editor and I get hung up on things. I once corrected a writer who penned, "The client drove away in a silver Mercedes." Instead, without thinking, I put down "silver colored Mercedes." At that point I knew I had gone editorial mad. I've tried to back off ever since.
@@thomasfarley Sorry if I've confused you along the way. Yes, a quartzite is easy to ID in field settings or hand sample but differentiating the two can be tricky. In this (and other) cases, it's made easier by looking at context and adjacent rocks. The overlying units are the Ophir Shale and the Maxfield Limestone (both Cambrian), two sedimentary units. Within this context, it is much easier to confidently call this an orthoquartzite. Plus it has primary bedding structures in it like cross bedding.
To answer your question, yes a metamorphic does form due to pressure and/or heat. This Cambrian unit was deposited on the surface, originally as a sandstone (sed rock). Over time, it was covered and buried by subsequent sedimentary layers (and there are a lot: the Paleozoic sequence of sed rocks in the region is something like 40,000 to 60,000 ft thick!). The weight of the overlying layers increased the pressure and the depth of burial increased temps enough for low grade metamorphism to occur. Metamorphism occurs across a range of temps and pressures, ranging from low to high grade. The presence of certain minerals and other evidence provide clues to estimate these conditions.
Hope this helps clarify. I am an author but not an editor so what makes sense in my brain and writing seems fine to me. Editors are helpful at interpreting and suggesting cleaner phrasing and language so the writing is more accessible. Happy to answer more questions.
Love your vids ty ps- what’s that first step it’s a doozy
Shawn: Dude! You get so close to the edge. You are freaking me out!! Thanks for the great videos though.
All good. The selfie stick/GoPro combo always makes it look more sketchy than it is. I was safe and solid. Thanks for the concern though.
Wowzers "put your hand on 1.3B years of time"!
Is it not a fault contact? Is the quartzite not allochthonous? Or were the sediments deposited on a Precambrian peneplain?
The contact is definitely erosional, not a fault. The quartzite here is autocthonous. Further up the mountain range and eastward, the Cambrian quartzite (formally the Tintic quartzite) and other units are repeated by thrust faults.
@@shawnwillsey Thanks!
Wow love the conglomerate Quartzite.
would love to find a transformative magma/hydrothermal intrusion into something like those pebbly quartzites @7:25 should make some lovely stone.