Marvelous Migmatites at Unicorn Point, Utah: Bridging the Gap Between Igneous and Metamorphic Rocks
Vložit
- čas přidán 15. 04. 2023
- Journey to Unicorn Point, the southern tip of Antelope Island in the Great Salt Lake, with geology professor Shawn Willsey to investigate fascinating and beautiful migmatite. These 1.8-billion-year-old rocks represent the upper end of temperatures and pressures for metamorphic rocks, where the rock partial melts into magma.
Support these videos! Your generous support allows me to travel to these location and create videos. Send support via:
PayPal: www.paypal.com/donate/?hosted...
or click on the "Thanks" button above.
or a good ol' fashioned check to:
Shawn Willsey
College of Southern Idaho
315 Falls Avenue
Twin Falls, ID 83303
Approximate GPS Location: 40.84747, -112.17578 - Věda a technologie
Another great presentation. This rock series has been very educational and useful. Keeping it real for being able to identify rocks in the field rather then teaching to do it on a 101 lab test has been perfect, thanks.
Great dramatic squiggles. Of course, it all makes obvious sense once concisely-explained. Thanks for closing that loop in the rock understanding-
I live in Lake Chelan and we have amazing migmatite here.
I'm a long haul driver from Florida. I have lived here all of my 55 years and the biggest thing around me are a few sand dunes and water. Don't get me wrong it's great, but I LOVE getting out the the Northwest (excluding the big cities on the coast) and seeing all the beautiful landscape and rock formations.
My favorite strength of interstate is I-70 between I-15 and the mountain range.
First time I drove that stretch of interstate it took me all day because I stopped at every pull off to look at beautiful landscape.
I'd love to spend a month around the Moab area.
Man, it's such beautiful country up there in Utah! Migmatite is the coolest stuff. We have some very colorful examples around where I live in Hemet, Ca. Trips me out when I'm out exploring to think of the conditions that produced these deposits. Thank for another great video!
Love the look of those layers
Thank you for sharing the fantastic discoveries Shawn.
Thx Prof for another interesting Geology Adventure. ✌
This was a perfect way to build on what we learned from the metamorphic rock video. As you suggested, I guessed these were gneiss, but your explanation of how they melted and folded made it easier to see the difference. I always learn something from even your shortest videos...thank you, Professor!
Rock on!
Brilliant! Gorgeous! And an excellent explanation. Last September, I was at the info center there, then up through Heber City, fascinating country! Sure appreciate seeing this. ❤
cool looking rocks. Interesting that they are being pushed deeper in the earth and are just beginning to melt from the pressure and heat.
What an eye opener, thanks Shawn
You can support my field videos by clicking on the "Thanks" button just above (right of Like button) or by going here: www.paypal.com/donate/?hosted_button_id=EWUSLG3GBS5W8
1:02 - I think I can see that huge smokestack at the base of the Ochre Mountains.
It's Oquirrh mountains.
If not OT, possible you could cover the Sevier VS Laramide, and maybe some apparent visual structural differences if the scale of the formations are able to be described that way like when you are on location?
Specifically what we observe about how each were formed. And how we "know/think that". Curious about the forces/directions and how they think the vertical blocks are moved up VS the sheeting, and possibly the interactions of the later aiding the former.
Or maybe even your take on the chronological timing of superterrains having any direct effects on those formations.
Thank You Shawn, learn so much here!
The Sevier and Laramide orogenies would indeed be a good subject as they overlapped somewhat in time and space but had different structural styles.
"Spread across the southern two-thirds of Antelope Island are the Farmington Canyon Complex rocks, which were originally sedimentary rocks formed approximately 2.5 billion years ago that were altered by metamorphism and intrusions around 1.7 billion years ago, making them the oldest visible rocks on the island (King & Willis Eds.,2000, p.1). The Farmington Canyon Complex presents as an assortment of granites, granite gneisses, migmatites, schists, quartzites, amphibolites and pegmatites (Parry, 2005, p.16). The layered gneiss of Antelope Island is composed of quartz, feldspar and biotite and exhibits strongly developed foliation. It weathers to show how rocks containing quartz and feldspar are more resistant to erosion than minerals like biotite (King & Willis Eds., 2000, p. 9). Crystalline basement rocks are exposed in a few other locations in the Basin and Range region, however, abundant examples can be found on Antelope Island, especially on the south end of the island at Unicorn Point (figure 1) (Willis et al., 2003, p. 6). The granitic gneiss, composed of medium-grained quartz and feldspar, with lesser amounts of hornblende, are distinguishable by their bands, created by layering and foliation, the result of metamorphic processes (figure 2) (King & Willis Eds., 2000, p.24)."-slcc.digication.com/geo1010/final-report
The Farmington Canyon Complex represents a triple junction, where three convergent plates came together in the Paleoproterozoic: pubs.geoscienceworld.org/gsa/lithosphere/article/3/6/401/145602/Paleoproterozoic-evolution-of-the-Farmington-zone.
❤ so great Shawn! Thank you!
I just discovered you channel and really enjoy it. You comment about the use of the migmatite as a landscape rock was what I was thinking all through the presentation! Thanks
Thank you for sharing these fantastic videos and geological explanations of the history of the Great Salt Lake in Utah. Wow !
Glad you like them!
FANTASTIC
Thanks for another informative video.
Amazing, videos on the great salt lake in general would be cool also
the way you teaching us (addicted me ) to the geology field trip , what an interest story behind each rocks you told us, thanks again
Nice. I'd love to see a geologic tour of places like Grand Canyon and Palo Duro Canyon.
I have a whole playlist of Grand Canyon videos with more to come this summer. czcams.com/play/PLOf4plee9UzDeaEYBHtkhGCiFbD4TcI0x.html
I love learning new things, thank you for explaining these rock formations I see from time to time. What camera do you use for your videos? Do you use an external mic?
GoPro Hero 8 with a foam wind case. No external mic (I'm just loud).
Simply Marvelous!!!!
Thanks! I always enjoy learning about rock types and structures. You make it easy to understand.
Very pleasing video. Thanks for showing these migmatites up close, it really is an amazing rock, what a story they have to tell. Did you say 1.8 billion yrs old, that sure is a long time and we can still touch them. They have weathered well.
I'd love a miniseries just on the basin and range extension of the Southwest! It's fascinating. Love your channel!
I was going to comment similarly. The rhythm of range and basin as you drive east-west through Utah and Nevada is unmatched. But not all ranges are the same! The Black Mountains (east of Minersville, UT) have entranced me for decades as I go by on I15. I have yet to go hiking there but it’s on the list. The bands of lighter rock and the craggy look draw the eye. For those of us that rock, anyway.
How I love ptygmatic rocks, great explanation, thank you Shawn.
Really beautiful rocks and a great explanation! Thank you 😊
I would like some of those Migmatotes for a rock garden. Fabulous!
There is a fabulous cliff exposure of migmatite at Chelan, right off the shoulder of the highway. There are some with very tight ptygmatic folding (I got to use the new word you taught us.) As a rock hound I find it exciting.
Speaking of the Stansbury Mountains - as you climb Deseret Peak and get within 100 yards of the summit - what is the rock in that rock pile. I last climbed there in 2000 and I remember thinking it was chert at it's angle of repose - it made climbing difficult, as in three steps forward, 2 steps back as the rocks shifted. As a newby to that area I probably didn't take the most efficient route to the the top. Thanks, great video, it's fun to learn more about the rocks there.
Thank you for this series. It’s been a long time since I was in school. This was a good refresher course. I may watch it again soon along with the mineral series.
Loved seeing those rocks and getting the explanation of their composition. THANKS!
You bet!
Great location/video! Thanks Prof.
They are beautiful. They would look great in my yard.
Woah sweet!
Thanks! Ptygmatic!!
Thanks for the donation. Much appreciated.
Wish I could take your class. A long time ago, I considered the South Dakota School of Mines. Love geology.
Thanks Shawn so beautiful
Thank you Prof Shawn!
Very fascinating rocks. From here in the video, it looked as it the white streaks resisted weathering more than the gray bands. I am in SE
Texas. Could you start with a map to get large scale location and cone down to the specific location? It would not take more than 60 seconds to give a clear location.
Is the water level rising due to rain and snow?
Okay I will get my Utah map out to follow.
I love your teaching and have been a rock collector all my life(76). Where I live is dead flat mud/gumbo clay. The highest elevation in our county is 18 or19 feet. The tallest thing is a big bridge built so the tallest Navy ship could pass under it to Beaumont TX. About 360 ft. The only interesting rocks are in the Home Depot garden center. I have traveled to every state and found the Roadside Geology books about 20 years ago. I love studying and learning. You videos are among a handful of informative ones I seek. There is nothing on the television worth seeing.
Thanks for watching. I usually put GPS coordinates in each video's description. I do lots of videos and don't have much time/energy to spend on editing but I'll consider adding a quick map view when I can. Yes, Great Salt Lake is an enclosed basin (no outlet) so it rises and falls based on precipitation amounts and evaporation rates.
Thanks for another great video Shawn
Farmington Canyon Complex. Might also point out that the pegmatite veins cross-cut the metamorphic foliation.
Good point. So much to cover.
I enjoyed it very much- thank you!
Thank you for another informative lesson! Is there any reason to the parallel orientation of the inclusions in the granitic dike and is this feature indicative of great depth conditions at which the inclusion has occured? I have recently stumbled across some felsic igneous rocks with inclusions and even dark minerals that display banding and similar orientation to some degree. So this piece of information would be helpful for me to see what kind of conditions this rock was formed.
The pervasive foliation (layering) of the metamorphic material was retained as the material partially melted. You can use the principle of inclusions here to determine relative ages. In this case, the dark metamorphic material is an inclusion in the pink pegmatite and is therefore older.
Great video!
Please be aware that Antelope Island is a state park, and removing rocks is prohibited. Unfortunately you will have to find migmatite for your yard elsewhere. 😊
Always interesting,thanks. 👏
Seeing some interesting rootless isoclinal folds in there as well. And I love ptygmatic folds.
The structures are exquisite.
Super cool
First video. I didn't expect those rocks to be on the shores of Antelope Island. It was still an island when I was there for school, so I missed out getting to see the cool stuff.
I'm going to have to check out your rock cycle videos. I'm betting they will be of interest to some of my students, as well.
Missing those mountains! 💜🏞️✌️😎🍏
They are packed with snow.
Fantastic
Very interesting, thank you
Thanks!
also some cool migmatites in the Precambrian rocks of the Sangre de Cristo Mountains and exposed in the roadcuts on the road up to Taos Ski Valley
Thanks! I've always wondered how these rocks formed.
Thanks for your kind donation. Much appreciated.
If you didnt know what you were looking at....
I have never noticed a rock like that ever. It went right to the edge of what a rock can do and made it back...
:D
I am number one 👍
Thanks
*Let the Sunshine In.*
*The Sun that Rises everyday...*
Just wondering, how old were you when you became interested in geology, how old are you now, where are you a professor at, and do make these videos off the cuff? There fascinating…. I could watch them all day.. Thanks so much for uploading them!
Hi Tom and thanks for watching. I teach geology at the College of Southern Idaho. These videos are indeed off the cuff although I know the area or read up before doing them. They are not professionally done so the videography can be crude at times but hopefully they are informative. I don't have the time or energy to do slick, in-depth video editing as I am a geology professor and not a full time CZcamsr. I am 50 years old now and was always interested in maps, landscapes, and such as a kid but it took me a while in college to find geology. Now its my passion.
Felsic-mafic banding and sharp isoclinal folding in both banded iron formations and migmatite makes one wonder whether there could be a common (modulated-sedimentary) formation mechanism.
6:24 The deep, round, parallel holes! The ones that look like products of migmatite-eating carpenter bees! Do they occur only in lake-weathered migmatites? If so, might saturated salt water etch faster along fold-parallel paths in the metamorphic layers, perhaps following early melt lines? [Or did someone just have a drilling contest there? :) Seriously, we used to have those in my hometown!]
Good observation. These are not vesicles (which only form in volcanic rocks). They are salt weathering features caused by spray when the lake was higher and wave action would throw salty water on rocks. Similar features form along coastlines and the “holey” weathering is called tafoni.
@@shawnwillsey now that's fascinating! Tafoni... a nicely melodic word! I wonder if the Unicorn Point migmatite tafoni examples might make someone a good Ph.D. thesis topic? The depth and parallelism of the holes, which appear somewhat correlated to structural features of the melted and almost-melted rock folds, might provide insights into why etching reactions prefer particular spots.
A wild guess: Salt in combination with moisture cycles may act as a redeposition catalyst. Concentrated chloride ions dissolve rock at the center of a saltwater puddle, but then redistribute the mineral content in pores of the surrounding rock as the chloride content spreads and diminishes. This would harden and reduce the porosity of the surrounding tube, producing ridges and tubes that resist the etching side of the cycle. The result would be a bistable chemical process in which the etching process prefers the center and the deposition process prefers the edges.
The easily-soluble salt would then re-accumulate back in the center of the tube in the next moisture cycle, repeating the process.
If there is a constant supply of salt and moisture, much of the mineral content could end up either being absorbed by pores deeper in the rock or dripping off and getting lost, especially after the outer perimeter of the tube hardened.
This should be testable. I notice that in Wikipedia pictures of various tafoni examples the perimeter rock looks darker and possibly more weather resistant than the average rock surface. That might support the deposition idea. Microscopic analysis should readily spot whether redeposition has occurred in the edges of the holes and tubes.
Fascinating, quite fascinating...
Addendums 2023-04-18.15:02 EDT Tue:
(1) The saltwater likely would tend to wick towards the more porous center of a tube, the same location at which minerals were dissolved, giving a net drilling effect.
(2) Given the extreme solubility of calcium chloride, one possible heuristic for which rock types are most likely to promote "drilling" would be surface locations with high calcium content. If initial melting preferentially liquified calcium minerals, that might work with the idea of lines of early melting as likely hole locations.
(3) A different triggering hypothesis might be porosity. Any rock that is inherently more cracked, porous, or containing easily dissolved minerals might preferentially become an etching site. However, since the most likely type of water is saltwater, this might bounce back to hypothesis 2 for the case of easily dissolved minerals.
In the migmatite, I clearly see the folding caused by the great pressure on the hot rocks. What I have been told by geologists about the reheating of metamorphic rocks is finally on a scale that is easy for me to understand visually. Thank you for doing this. I'm also glad to see the great salt lake. I have started my studies of ice age floods. As I watched a lecture done by Nick Zentner two nights ago I was remembering your videos about the Bonneville Flood. He was showing pictures of where the Bonneville effects are seen in Washington. Part of my study plan is to re-watch your flood videos. I'm also reading in my books about the floods. I'm really putting together a big picture of just how amazingly large these glaciation events were. Thanks for all your videos! I
I love your diligence and dedication to learning.
@Shawn Willsey I loved college but was burned out after my Masters. I have always worked on learning new skills in my textile hobbies. After being so sick and nearly dying fighting cancer in 2021, I lost executive functions. I worked to get them back. My daughter was taking a geology class, and I was asking too many questions. She taught me how to find Nick Zentner on CZcams. As I learned from him, I wanted more. Then, last year, I found I could read freshman level texts again. From that point, I have gone way down the rabbit hole. It keeps me busy and fights off worry as I am mostly in a recliner continuing this, winning this cancer fight. Most importantly, the study makes me happy and joyful. You and Nick are excellent teachers, each with your own style. I'm so glad you are sharing with lay people through modern tools. Thank you!
@@Anne5440_and Myron Cook is excellent too. He has been aptly named the Bob Ross of geology.
Shawn, thanks for sharing these fascinating rocks. In addition to being really interesting, they are gorgeous!
One suggestion, please try to slow your camera moves and think about stabilization. It is sometimes difficult to see the features you describe because the camera is moving too much.
Yeah, solid geologist and lousy videographer. I will work on panning slower.
I've looked at a rock cut all the time and wonder how do you get rock that looks like it was mixed as easily as muffin batter or folded bread
Ontario Canada :)
Very cool rocks
With your word of the day, I’ll bet you’re great at scrabble 😅
I'm glad he spelled "ptygmatic," because I'd never have guessed it! 😅
Exciting presentation, who would not be impressed by the beauty and geological forces involved. Was this the result of an accretion wedge being squeezed into an oceanic trench?
The Farminngton Canyon complex is thought to be the result of continental collision as smaller crustal pieces collided with and accreted to North America.
@@shawnwillsey Thanks Shawn!
Fabulous, Shawn. I've not been that far south on Antelope Island. Is this near the end of East Side Road?
Yes, literally the end of the road. See my GPS coordinates in video description.
What caused all of the little holes in some of the rocks. I’m trying to figure out how they were formed since there is no flowing water there.
Good observation. These are not vesicles (which only form in volcanic rocks). They are salt weathering features caused by spray when the lake was higher and wave action would throw salty water on rocks. Similar features form along coastlines and the “holey” weathering is called tafoni.
I always find it is so much easier to understand the big picture of stuff like this if I understand the etymology of the specialist terms, like migmatite; does it mean “mixed rock”? Is there an online geology encyclopaedia of etymologies for people like me? 🤔
I see several rocks with holes in them that look too perfect to be vesicular, especially the way some of them are lined up with precision. Are they somebody drilling out samples? Are they bored out by insects? What's the story with those?
That caught my eye, too. I'm guessing vesicular, given the rock type, but proximity to a salt lake puts me in mind of the process that created vuggy limestone. I think Occam's razor still cuts the vesicular way though.
Good observation. These are not vesicles (which only form in volcanic rocks). They are salt weathering features caused by spray when the lake was higher and wave action would throw salty water on rocks. Similar features form along coastlines and the “holey” weathering is called tafoni.
@@shawnwillsey , Ah. I ultimately guessed wrong though. But, to put a finer point on it, I'd now guess that it's the magnesium chloride and not sodium chloride that is doing the weathering there?
@@shawnwillsey Wooowwww, learn something new every day. Had NO idea that's what caused these holes and "tafoni" is my new word for the day. That's just amazing. Of course as salty as the Great Salt Lake is, it can probably do some damage fairly quickly.
Been there once, once! Happen to see any Bison herd out on the flats or near the road?
Yes I did. I'll maybe add a short clip of them when I bundle these four videos together later.
Thanks for the lesson! Looks like I'm the 666 liker, lucky or not depending on your superstitious preference. Antelope is a frequent playground but I haven't been out to the south tip for a few years. I'm going to get back out there this year and see those amazing rocks again! I think there are also some really old rocks over by the Frary Peak trail head turn off?
Yes, much of the island (except the northern 1/3) is 1.8 billion year old metamorphic and igneous rocks of the Farmington Canyon Complex. Look for a four-part video series soon.
Amazing video! I'm assuming that those rocks were buried several kilometer below the surface at one point in the distant geologic past. How old are those rocks? What geologic process or event(s) brought these rocks to the surface?
Paleoproterozoic: about 1.8 billion years old. Two mtn building events and erosion exhumed the rocks.
@@shawnwillsey The original sediments are ~2.5 Ga, the pegmatitic intrusions are ~1.7 Ga.
Good guess.
You mentioned that the big rocks would make great landscaping 8:00. I don't know if it is legal to take rocks from Antelope island state park, but I hope it is not. Those rocks should stay where they are for others to enjoy and to preserve the park.
No it is not legal as far as I know. Comparable rocks are available on public land in the Wasatch Range and other locations.
So would the banding and injection of other rocks taken place while they were flat lying? And then with heat and pressure would they have just been pushed together or could they also kind of swirled around a bit like different layers of taffy pushing into each other? Just trying to visualize the possible scenarios taking place deep underground.
Likely this was a complex zone with no preferred orientation of rocks. Imagine these rocks forming in a vice.
How do I remember these words? Migmatite and ptygmatic. Mig and ptyg. Okay, if I imagine that's how it would end up looking if I were to weld something, MIG or TIG. So between Shawn and This Old Tony maybe I can remember.
You forgot to tell us how the heck they got from a place so deep they melted into taffy, but are now at 4500 feet at the surface. And where and when that rock originated... Has it ever been at the surface before and then made a round trip? Or has it been so deep from the beginning and only now comes up for some reason. I suppose there's no gold in that kind of 'ignius' rock because it isn't from a place that deep, and never had any to begin with despite all the quartz veins. Yes I'm a gold bug hehe.
Shawn pointed out all the fault-block mtn ranges from the Basin&Range fulting- The tilt of the blocks lurched the under to the over and vice-versa.
Yep. Several mountain building episodes along with erosion have exposed these basement rocks. Sevier Orogeny was a major mountain building event in Cretaceous and then Basin and Range extension over last 20 million years have uplifted block to form island.
What is the regional geology of these migmatites at Unicorn point, meaning, how did they form and get there ? What’s the name of the formation and its age?
These rocks are part of Farmington Canyon Complex, Paleoproterozoic in age. A future video that will drop soon will cover the other rocks that are part of this assemblage. These rocks formed tens of miles below surface under extremely high temps and pressure during a period of continental growth as crustal fragments were colliding and suturing onto North America.
How did you get onto the island, I thought you had to fly?
Nope. Causeway from Syracuse, UT takes you right here by car. The island is a state park with trails and such.
@@shawnwillsey flown over it my times, will have to land and look some day.
“Pre-Metautrafelsic.”
I am not a geology student but I really like your geology videos. North America is an amazing place with a lot of unique geological features too! I have been around for a lot of your videos and liked them a lot.
I mean no offence, but you camera seems to over-sharpen the video, and created an 'oil paint' effect when pointing on the rocks. It was sometimes hard to tell the texture of the rocks from the artefacts.
Could you by any chance turn off the sharpening from your camera so it doesn't change the texture of the rocks too much? Thank you.
Thanks for watching and learning with me. I use a very simple GoPro Hero 8. I don’t think it has many effects and settings but I will check. Maybe it’s your monitor?
@@shawnwillsey Thank you for paying attention to that. I really appreciate it. GoPro has a selection in its menu, for sharpening low-medium-high. It's probably set to high by default. High sharpening is fine for portraits and sports, but is not great for scientific display. There's an example czcams.com/video/8WZXdnb-YOE/video.html
How old are those migmatites estimated to be?
'Ptygmatic,' from the Greek 'ptygma-' folded.
Is this exposure the bedrock of this location that has been uncovered by erosion? Don't see any other likely source.
Yes, along with uplift by Basin and Range faulting which brought up the block of rock that forms the island.
Thank you. There be dragons
More sexy rocks 😁😁
ptygmatic folding...gneiss ...as in that's some gneiss schist...haha
Sometimes geology sounds like Pokémon
finger painting, where a child should not be finger painting...to answer the question as to how them rocks formed...LOO
That's not Igneous, it's an ultrametamorphic!
у нас на острове Сахалин много таких пород ,спасибо за работу
ooow, how tortuous, that's not gneiss.......
Thanks!
Thank you for your kind donation. Much appreciated!