Whole Mountain of VOLCANIC GLASS! Explore the geology of Glass Mountain, California 

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Three years ago, I was exploring with my metal detector, around my Arizona campsite, along a wash, when I came across a bunch of obsidian flakes. Obviously, someone had been knapping at this site and recent flash flooding had exposed the shards of obsidian. What surprised me the most was that much of the obsidian was obviously not native to Arizona and after reporting the area to local authorities, who excavated the site, it was reported the obsidian was from New Berry crater, in Oregon.

The layers of obsidian and pumice are fascinating! I didn't know that the two could be found together like that. Amazing!

So in the summer of 1990, I worked for the NPS in Lava Beds NM looking for Bald Eagle barf. The bald eagle was being delisted from the endangered species list and they were creating a management plan. Anyway, on a sunny day, you could look to the south and see Glass Mountain glittering in the sunlight. Really cool!

Thanks to your classroom videos I was able to ID both rocks!

What are the odds? I am from Utah and have been watching all of your videos enjoying all of them for the last two months. Trying to teach my kids about rocks and where and how they were made while driving Utah and Idaho. (Failing) Funny enough last night we drove to Sacramento though Nevada and up over Reno and Lake Tahoe. While on that drive my 9 year old asked what type all the rockets were we were seeing. My reply was oh man I haven’t watched one of Shawn’s videos of California yet too bad he isn’t in California with us. What are the odds? My 9 yr old daughter struggles with school but Volcanos and Mountains excite her and open a flood gate of hundreds of questions my wife and I try to google or learn from Shawn. Keep it up. Great content.

Thanks for showing all these igneous relationships basalt, scoria, then gas-glass and ooze-glass. Also, the footsteps sound extra-crunchy.

Newberry volcano is an amazing place to see obsidian. Thanks for another great video.

Well I got one out of two I know obsidian well my grandparents were RockHounds you would think I would have guessed pumice as well . The folds were the most amazing part of this video.

Thank you. From switzerland. 🙂

Very cool! And so young. I wonder about indigenous peoples recollections of this. There must be stories. 👍🏼

Remarkable is right. Google videos of taffy pulling machines. I remember seeing them at the Idaho State Fair when I was a kid in the 60s. That's the metaphor that immediately sprung to my mind.

There is a hill @640’ called Glass Mountain in St. Helena (Napa Valley). There is Obsidian but it seems that it also shows trace “rhyolite ash” and “perlite”. Quite an anomaly. This is attributed to the high silica content in the Sonoma Volcanics field. There are several “Glass Mtns.” In California. The one I plan to visit first is near Mono Lake in the Long Valley Caldera (Owen’s Valley). Mono Lake has Tufa’s. Check them out. Thank you for the great video.

Instead of toothpaste, it reminds me of watching a taffy machine. What a fascinating place. I would be inclined to have a desire to take home a truckload... ❤❤❤

I thought you were close to me, since I’m not far from Glass Mountain, but my Glass Mountain is in Mono County and is part of the Long Valley Caldera. I didn’t know there was another Glass Mountain in California. Anyway, very interesting volcano.

No kidding Glass Mountain! It sounds like you are walking on broken glass the whole time. Great video!

Glad to see you in my neck of the woods Shawn! I am fourth generation Siskiyou and Modoc county native.( not Indian) In the summer of 1970 I worked on a fire crew at Lava Beds National Monument. In my free time I explored the area extensively, plus I hunted mule deer in this area. It is truly fascinating and beautiful,lots of lava tubes etc. Great post Shawn keep em coming!👍👏❤️😁

I grew up camping at Medicine Lake. It was so cool exploring the glass mountain. we found arrowheads and the imprints of animals caught in the glass flow! we carried some obsidian rocks home to San Jose for my parent's rock garden. That was back in the 1960s. Thanks for reminding me of good times!

I'd love to have that initial piece of obsidian for my coffee table, and a few good pieces of pumice in my bath!

The little test was easy. I'm ready for the final exam.

Nailed the quiz thanks to your rock identification videos. 🤓 What a cool place that was once very hot.

Coolest looking rocks ever. So much differences in the types making up the layers. Weather changes have played havoc in the cooled rock , cracking everything up, which actually came out of the Earth surface slowly about 950 years ago. Nice to actually see this on video Shawn. There are many small volcanoes that make up the area to the north and yet to see those. Plus the shield volcano that is Medicine Lake. Recommend very sturdy footwear here!

When I was very young, back in the early 90s, my family and I stopped by there, as we were on our way to some property we owned or maybe still own out in Modoc. We and a bunch of other people took a bunch of large pieces, even though that was not permitted. We still have them in our front yard to this day!

What a great location to illustrate both. Wish I was still teaching. Thanks

Fassninating to see the folds of lava that had been flowing......and the inserts of Obsidian ot lava that had cooled and was exposed during the flow episode. Thank you for sharing on film this site!!

Cool place.

Great footage & comentary! Thank you for sharing your knowledge. I'm from Utah & have some nice pieces of obsidian in my front yard My mother used to take us to Glass Mountain when we would go to Medicine Lake

Thank you sir for showing this glass mountain. Looked rock for Fence building but there seems more to it glass n floatabioity. Good day jussojuan

Fantastic! Really enjoy all you do! This one was, for me, terrific!

A suggestion to those who decide to go.. boots, thicker jeans/shirt, and gloves are a must have when hiking over that pile of glass. It's an awesome place to visit with lots to see. In retrospect, it's time to go back.. been a while. Plenty of lava tubes to explore at the park north of Glass Mtn. Go get your hike on!! (pack a lunch)

What a great lesson. First time I ran into your channel, won't be the last.😊

Boggles the mind. So the lava must have been "dry" to form obsidian, if I recall previous lessons correctly. Is it correct to assume the pumice gas is from materials in the granite, or whatever the source rock is made of, and not water? And how can the banding happen in the same material? Are the obsidian layers "fizzing" away their gas before they roll along?

Wow, Glass Mountain looks even more awesome than Big Obsidian Flow at Newberry! That's worth taking a drive. BTW, Shawn, sorry I couldn't make it last week. One of the questions I was going to ask if we'd been able to meet up at Newberry was about Big Obsidian Flow and Glass Mountain and just about anywhere that forms this amazing obsidian: Since it requires RAPID cooling in order for obsidian to form without mineralizing, can some of that rapid cooling be attributed to the environmental or climate factors in place at the time it erupts? I've noticed that these obsidian flows occur at pretty high elevation, where at times it can get bitter cold or even glaciers are present; do you see any evidence of these pasty flows taking place either under snow or glaciers? Or such low air temps that it impacts rapid cooling of these flows? I can see no evidence of these flows forming as tuyas, but I can see where a cold enough climatic environment might be enough to cool these flows almost like a fast-paced freeze-dry process. Your thoughts?

Are you going to visit Mt. Lassen? I used to camp there and climbed to the peak. It's amazing to hike on a potentially active volcano in California. I live in Houston now where there is no volcanoes, and no earthquakes. Just hot temperatures and hurricanes.

Thanks as always for an entertaining and informative geology video - love that you take us to so many places! One question I had on the obsidian - does each flow have a distinct enough chemical signature that it can be used to associate artifacts made from it?

Obsidian. Pumice. Aced it! Woohoo!

The folded layers are awesome

1) Obsidian 2) Pumice I honestly didn't cheat. I suck at naming rocks. "Rocks for Jocks" class was hard! Wow, wonderful video and geology lesson on the area. Spent early childhood summers at Lassen. So cool to learn more about the area. Thank you.

Driving along CA Hwy 139 east of Glass Mountain during the winter, many motorists refer to Glass Mtn. as the "Modoc glacier", because all the snow on the thick obsidian mass resembles a glacier.

I will always know pumice when I see it for I used to have to scrub a big flat grill in a commercial kitchen with it at the end of every day. It was remarkably consistent in texture and it would wear away with use. I had never thought until this moment how that it could be that that texture could be so consistent but perhaps in nature there are locations where it is uniform like that and it is mined. Perhaps it is artificially produced?

Fun fact: if youre driving into Glass Mountain from Medicine Lake and stop at the little parking area, there is a tree with a giant burl on it there. Back in 1997 I tied that tree in a knot on a Shasta College geology field trip.

Thanks!

Tucker Hill is a rhyolite flow dome in Oregon north of Lakeview. The outer shell is perlite then obsidian and then glassy rhyolite. There was an open pit perlite in early 2000s.

You're in the field video tours are amazing. What an incredible geologic playground.

Absolutely fascinating 😮

Really interesting location, had no idea about the relationship between obsidian and pumice. Thanks for the work you do, really enjoy it

Appreciate your work.

I was privileged to study three years under a Dartmouth trained geologist in high school, at Henley HS in Klamath . He had a pregnant wife as he began his doctoral dissertation and took a job with USGS, never getting back to his PhD. I majored in geology at OSU, but paused to get married and never made it back. Oye vey. Love your channel so far. Thanks for your work.

Grt geo-adventure. Thx Prof ✌🏻

Very cool! Thank you for sharing.

Your videos are bad ass! Thanks.

I found the sounds of your footsteps hauntingly familiar. I used to live near an old slate quarry in upstate New York and whenever I used to explore there, my footsteps sounded like yours. Very different rocks, I know but the sound is the same. However when it comes to your obsidian and pumice, I wish I could see the grain structure under a microscope. I'll bet some dramatic differences show up at that level just like in metallurgy. You can tell a lot about the quality of steel and the sharpness of edges under magnification.

Surreal landscape, sounds like you were walking on Glass.

This was great- I visited this place more than 50 years ago as a young girl and have wanted to return some day.

Hello Shawn, been there a few times back in the 90's, back then there was a road where you could drive up to the top in your car, giant chunks of obsidian on top.

Thanks! That was AWESOME 😮❤

The geologic formation of Big Rock Candy Mountain near Sevier would make a fascinating video.

Awesome! Melted rock is the best. I was out exploring an area with similar geology... Pumice like stuff. All folded up, lots of Migmatite. No Obsidian though.

Fantastic video, thank you!

I travelled through all of CA except for San Diego, 42 yrs ago. I miss it. Didn't get to see La Brea. Lived in BC for 30 yrs. Now live in Quebec. Want to get a motorcyle and take up camping.

Absolutely fascinating!

The folds are just crazy....so clearly defined by the obsidian and pumice! Spectacular, Shawn. It looks sharp and tricky.

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Thank you Shawn - love your videos 😀

Awesome

You are not too far from some incredible supervolcano caldera features.

Fascinating area and great content!

There’s more to creating obsidian than just rapid cooling of lava; if it were just the cooling process, the whole oceanic floor would be glass. Obsidian is produced from felsic lava (not produced on oceanic floors) rich in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. It is commonly found within the margins of rhyolitic lava flows; these flows have a high content of silica, granting them a high viscosity (low fluidity.) The high viscosity inhibits diffusion of atoms through the lava, which inhibits the first step (nucleation) in the formation of mineral crystals. Together with rapid cooling, this results in a natural glass forming from felsic lava. This is how obsidian is formed.

Wife and I went to Newberry earlier this summer, when she sees this video we may be loading the car for another road trip

Over here we had a fieldtrip to a little cone in the Mojave desert, there's a ton of cyan colored obsidian (though my classmates think they're more like grey)，I did not believe those were obsidian at first！Looks like they can be several different colors.

Great Video!

WOW Damn that is so cool. Thanks for showing all the beauty of geology.

Such a cool vid👍🏼

Great job teach!!!

Thanks for the video! Really fascinating the geology involved in a lava flow. I've heard of glass mountain but have never made the drive up that way to see it for myself. I may have to venture up that way!

It is amazing to see the pumice so closely intertwined with obsidian. Never would have thunk it. Thanks for svrambling for me.

Truely fantastic. I'd never seen such close contact with Pumise and Obsidian. Amazing folding of those layers of Obsidian. Fascinating. Nice find Shawn !

When I was growing up my Dad told a story of a Mountain in California where you could pick lava rock of the side of the mountain. He brought back a good piece of the black lava rock. When he passed on I got it. It is flat on one side and kind of wavy on the other side and black and shinny.

thanks for a great lecture :) Living in Denmark we dont have volcanoes or mountins, so find it very interesting and realy love geology :)))))

Shawn, what an amazing trek... Your video quality is super. I wish we had such a range of volcanic deposits here in the UK. I'm so envious!

This is so, so cool - to see the obsidian and pumice together in this formation! Thank you for this information and video. Now I'm going to watch your other videos...

Has anyone been able to get into the pumice and see what kinds of gasses are trapped in there? The folds were absolutely stunning. I loved collecting obsidian as a kid.

I am from northern California and when I was about 14 (1972)we were over at Lassen deer hunting and stopped at Glass Mountain. Back then there was no restriction on picking up a hunk or two of the obsidian. But, the last time I was there in 2010 there was not a whole lot of the glass left and warning signs to leave it alone. It is still an impressive deposit but nothing like it used to be.

Back in the day when nobody thought grabbing a souvenir was a problem, my family took a big chunk away from Glass Mountain. I still regret leaving it behind in my parents' yard: wonder if new owners have a clue....

Thanks

Beautiful way the lava flowe and folded on itself! I’ve been to Newberry in Oregon and the San Francisco Volcanic region in Arizona. Now I want to see the folded pumice and obsidian flows in California! Volcanic landscapes are beautiful! Thank you for the tour!

There are areas toward the eastern side of Mt. Shasta that have pure obsidian flows. In those flows you can see tree trunk casts.

Great video and great area, thanks! Medicine Lake and Newbrrry are so different being shield volcanoes, unlike the Cascade stratovolcanoes. Have you read Vic Camps paper “The Case for a Long-Lived and Robust Yellowstone Hotspot” that says seismic tomography shows ‘fingers’ of magma 75km deep reach out from YHS to Newberry and Medicine lake?

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I know EXACTLY where that is. I've been there before & the last time I was there they were mining it!

This mountain is upscale and shows a lot of glass! 😉

There is a mountain north east of Flagstaff, Arizona called Government Mountain. It is made entirely of Mahogany and black obsidian. I have seen large slabs of obsidian there. It is crazy.

I spent some time at MLV looking at geothermal power development (couldn't get a permit). Check out the ice caves, extensional fissures, and phreatic craters in the area. So cool!

I've camped there before. Wearing gloves and old shoes is a good idea if you are hiking around in those lava flows. In some places there are larger blocks of obsidian. There is dispersed camping just south of Lava Beds and reserved camping at Medicine lake. A great place to visit, but remote.

A bit of landscape literacy regarding a pile of rocks. Thank you

My son and i built a snowman where you're standing in June one summer.

A few years ago my husband our daughter an I went up to “GLASS MOUNTAIN “ there are/were chunks of OBSIDIAN AS BIG AS A SMALL HOUSE AND BIGGER GLOBS OF GLASS ! It was amazing! Not just a small amount either ! Very interesting and is a mountain of BLACK GLASS !

At the entrance of the current pumice mine there used to be a small cabin where an old man lived in summer as he cut pumice bricks, sold for restaurants use on grills. Incidentally there was a brothel in Tionesta. My dad had to turn his head when they were driving by in his dads Model A Ford.. His dad was a pentacostal preacher from Westfir, OR. I can only imagine that scenario. Lol Nothing remains today of the milltown but Tionesta still has a store as far as I know, with many pictures of that day.

Ajusco in Mexico City, is very volcanic. Vallee de Tezontle-one cliff is red and the other is black pumice.

Love this one Shawn. Just thinking about how many uses and how important these volcanic out-crops were to Aboriginals. Fire was great and the wheel worked out well. Thanks for posting! What other types of rock could be flint knapped Chert? Flint?