City of Rocks is new to me. A really interesting place. Thanks.

Excellent. I found it a really interesting talk, I like the explanations with detail on weathering and so on.

Thanks for explaining why the granite is so friable. Being from Colorado, I've been in contact with many granite facies, but I haven't been in contact with one so crumbly as what you're describing. Amazing how the haline content of the rain can make such a difference between hard and crumbly.

These videos are so very interesting …… thank you

Thanks for taking the time to make this and educate us. I learned a lot. It is a wonderful place to be!

@shawnwillsey

2 жыл бұрын

Thanks for watching Jay. Subscribe if you haven't already. More to come.

Thanks for this. I grew up in SW Idaho and have never made it to the City of Rocks. My son has climbed there many times from SLC.

Really appreciate your explanations and videos!

Thank you for teaching the geology of this area. Very interesting.

@shawnwillsey

Жыл бұрын

Glad you enjoyed it

Incredible place and climbing area

City of Rocks, never heard of it, awesome spot.

🙏 thank you 🙂

Thanks!

Great video podcast to listen to in the car on the way to the City, thanks! A lapel mic might be of help for your listeners to not miss any of the fascinating details as you turn to point them out! Thanks for making this-so many times we’ve wished for a geologist at our elbow as we travel. What an endlessly fascinating speciality.

My favorite color of granite. Very much the same color as the granite in Central Washington and North. My copy of Geology underfoot arrived toady. Now that I've watched this I have the chapter in your book on City of Rocks. I'm trusting the donation I made has reached you by now. I'm off to learn some more now.

@shawnwillsey

Жыл бұрын

Yes, thank you for your kind donation. Glad to hear my work brings value to your life.

Reminds me of some areas in southern Arizona.

used to have our easter picnics there. There is a formation that I have been told is called the elephants head. My Uncle and I would rock clime that.

Great learning Video ..................... thanks ..............

question: at 5:45 there appears in the background a strange discontinuity in the rock just behind you at a nearly vertical angle. It looks to be perhaps 2 inches wide. what is that?

@shawnwillsey

2 жыл бұрын

Nice observation and great question. This is a small igneous dike, an intrusion of magma that cuts through the granite. Basically, as the magma cooled to form granite, it contracted slightly, creating fractures. Residual magma moved through these fractures and cooled and crystallized. The dikes are typically lighter in color because they are made of lighter colored minerals like quartz and muscovite.

@brentweissert6524

2 жыл бұрын

@@shawnwillsey thanks for getting back on this. when i saw that formation i immediately thought "igneous dike" but i have always thought igneous dikes to be much darker in color. I really do enjoy your videos. Keep 'em coming!

@shawnwillsey

2 жыл бұрын

@@brentweissert6524 You bet. Dikes can be an array of colors, ranging from white to black depending on magma composition. If the magma composition is mafic (more iron and magnesium), dikes are usually dark gray to black. If the composition is felsic (more potassium and aluminum), dikes are white to light gray. Thanks for the kind words. Look for more videos soon.

Another good one!

Very interesting. I have not heard of muscovite crystals.

Ever see the unusual City of Rocks State Park in New Mexico? Really odd spires of volcanic tuff just popping out of the ground in the middle of a plain between Deming and Silver City. It isn't a very large area, maybe about a square mile, your video reminded me of it.

Great video! Thank you!

@shawnwillsey

2 жыл бұрын

You bet. Thanks for watching!

That looks just like where my mom lives above Palmdale, in the San Gabriels in southern CA. You can see the Devil’s Punchbowl formation right out their front window. It’s beautiful, aside from the name.

Is this granite part of the Idaho Batholith history which would be older than 28 MYA. If not, then what was the source of the granite, Yellowstone Hot Spot? I was intrigued by Professor Zertner’s crazy Eocene series and from what I have learned is granite implies there was volcanism above the area. 28 million years seem quick to erode overlaying volcanoes.

@shawnwillsey

2 жыл бұрын

Hi Cary. No, this granite is not part of the Idaho batholith. It is much younger and too far south (not connected). The source of the magma that formed this granite is likely related to east-west extension (Basin and Range extension) that thinned the crust and allowed partial melting of the lower crust. This magma rose upward, crystallizing into granite at a depth of about 6-10 miles. Continued extension and uplift of the Albion Range eventually exposed the granite within the past 5 million years. There is no evidence the magma ever made it to the surface here and erupted from volcanoes so it appears to be an intrusion only.

@carygrant8796

2 жыл бұрын

@@shawnwillsey Thank you for the response and education. There appears to be wide spread thinning and relaxing of the western North American crust following the subduction of the Farralon Plate, hence the Basin and Range province. I take it the San Francisco Volcanic field in northern Arizona, the lava flows in southern Utah, and the New Mexico volcanics are a result of crustal extension. How does a granitic intrusion get uplifted during extension, especially if it formed at a depth of 6 to 10 miles? If the over laying structures have been removed, where are they? Did they erode? Did they slide off? The remnants must be somewhere, but where?

@shawnwillsey

2 жыл бұрын

@@carygrant8796 San Francisco volcanic field is somewhat problematic and does not seem to be related to B&R extension. Maybe its a hot spot of some sort. Volcanism around Cedar City and St George is definitely B&R. Not sure about New Mexico unless we are talking Rio Grande Rift area. Once granitic magma forms, it rises because it is less dense than surrounding rocks. If it rises close to, and ultimately breaches, surface, then it is an eruption. However, many magma bodies rise to a depth of equilibrium and cool/crystallize. As for the overlying material, some of it was eroded when Albion Mountains rose, but much of it slid off of intrusion along low angle (detachment) normal faults. These lie east and west of Albions. The east side of the Albions is the best example where the rhyolite ash and lava (related to Yellowstone hot spot) of the Jim Sage and Cotterel Mountains slid eastward along detachment faults between 5-8 million years ago. These ranges are now backtilted to the west. The western side of the Albions is broadly similar with the detachment between the Albion Range and Middle Mountain which mainly has Proterozoic metasedimentary rocks.

Don't think I'd be sticking my hand in those holes being in an area where there are rattlesnakes.

@k.chriscaldwell4141

2 жыл бұрын

I was thinking the same.

Shawn, I'm intrigued by the narrow intrusion running almost vertical at 5min 40sec. What was going on here? Was this fluid intrusion well after the main material had hardened?

Dr. Willsey: at 5 min 45 sec in, you pass in front of a slightly raised dike or slab slicing diagonally across the granite face. What do you call that, and how does it form? Thanks.

Apologize if I missed it... Is there a rough time frame of the granitic formations, you're referring to, have been exposed to the surface? Deeply admire your work. TY.

At 5:45 you walk past a strange line of rocks that looks like it's been squeezed out between two other forms -- what is that?

Image being people living around there before modern plumbing of fresh water to everyone's home. It's a desert area. Finally...some rain! But....the rain is SALTY. Talk about unfair! It had NEVER occurred to me that rain could be salty. I had always just assumed that it would be fresh.

I see you walked past what looks like a dike at 5:46. When did magmatic intrusions occur following the crystallization of this regions granitic batholith?

went there more than 50 years ago

i love you so much

At least a bazillion years ago I estimate.

@dukecity7688

Жыл бұрын

At least.

kzread.info/dash/bejne/mathr5WYYbW9frg.html these 2 guys believe they've discovered megalithic construction in Wyoming. I've tried to explain that's not the case but they're dead set and determined lol

Exfoliation=choss

Alluvial shaped by A massive flood .

Commercial boots look like cheap sht to me.

@geoffgeorges

6 ай бұрын

Nice on topic comment!