The Bonneville Flood: Why, How, and Its Spectacular Effects on the Landscape

[@JasonSmith-we5ls]

I watched this in its entirety. Great work, thank God those of us that are interested in the topic from home have guys like Shawn.

[@theMick52]

Don't forget Nick!

[@larrywaltman3916]

Excuse me. Do you really believe in God? If so, how can you believe the dating of this flood? God flood the earth roughly 5,000 years ago. He created heaven and earth about 1000 years before that. At this point I quite listening.

[@kinzieconrad105]

Do you Believe that continental uplift had nothing to play with it!

[@kinzieconrad105]

@@theMick52nick would get it right , not like this idiot!

[@brettdavis4269]

This is exactly what I've been looking for. For over 20 years I've wanted to know this exact information about the Bonneville Flood. Thank you, from the bottom of my heart, for presenting this.

[@shawnwillsey]

You bet. I'm glad I was able to finally put together a comprehensive presentation on this often forgotten or overlooked, yet spectacular event.

[@dianespears6057]

Still watching but have to say Shawn is the only person (in my You Tube world) who gives detailed attention to the Bonneville flood. Always glad to see the presentations. Thanks to Shawn and the group.

[@shawnwillsey]

Wow, thanks!

[@Mrbfgray]

Indeed, I've seen a ton on 'that unnamed' flood series to the NW but this one only mentioned, fascinating stuff. That these great lakes existed is old, but the massive floods associated much newer territory.

[@Greg41982]

Not sure why KZbin suggested this to me today, but Holy Cow, man! 1.33 hours of enthrallment right here! I'm a Utah native. I have learned about Lake Bonneville all through primary school, we ride our bikes along multiple parts of the Bonneville Shoreline Trail, I have wondered out loud why the Bear River flows where it does, but never dived deeper. Now I'm droning on and on to my wife and two boys and currently I'm just like, "look, just watch the presentation, okay?" The only drawback is that now we'll have some weekend road trips to really otherwise boring places... Thanks, mate!

[@Rachel.4644]

Your talk sure brought Lake Bonneville into clearer focus. Impressive. Thank you !

[@shawnwillsey]

Great to hear!

[@toughenupfluffy7294]

Excellent presentation! Thanks, Professor!

[@StereoSpace]

Shawn, what you see as a dearth of educational material on the Bonneville flood, I see as a golden opportunity for you to write a book - the first book? - on the Bonneville event. If you do a good enough job, it may become the definitive book on the subject.

[@shawnwillsey]

Tempting. I'll give it some thought.

[@Danika_Nadzan]

Great idea!

[@erinmac4750]

Exactly! I would've thought there'd be something. But, then I'm likely biased by my interest. 😎🏞️

[@Anne5440_]

Oh, please do! The Bonneville Flood is important to all of the PNW because it went to the ocean before the Missoula floods.

[@Linandemma]

@stereospace It will be the only one, lol. But yes, someone in your state is missing a trick, folks. I'd buy it; I live in the UK 😅.....(I would). And I've no doubt it would be very good, Shawn has done this before.

[@ja6995]

So excited about this upload! Thank you!

[@shawnwillsey]

Hope you enjoyed it!

[@stephenbeck6410]

I love your channel! The algorithm gave me your other “short version” first, and then I watched this one. This one is so much better! Thanks!

[@shawnwillsey]

Agreed.

[@mamak1379]

Please write that book Shawn. I would buy it. I own your other 2 books . Thanks for this lecture.

[@rockweiler777]

I enjoy flying from south to north, watching the flood stories unfold beneath me from Utah to Washington. I agree with you that the Bonneville flood deserves much more exposure, and appreciate greatly that you have helped with that here! A remarkable and ever unfolding tale!

[@shawnwillsey]

Well said!

[@johnplong3644]

Just finished watching this I am a Zentnerd So now am Watching and listening and learning from you as well

[@Linandemma]

Myron Cook is really good as well as shawn and Nick. Different style again.

[@brendanacord]

Love these lectures, top quality stuff, would be great to see more! Thanks for sharing!

[@shawnwillsey]

Glad you like them!

[@bobbyadkins885]

Excellent Shawn, I remember your first KZbin video on it, that’s what brought me to the channel couple years ago, enjoyed everything you’ve done

[@shawnwillsey]

Thanks for sticking with me these last few years. I feel this presentation is a big upgrade over the first one which was just a crude concept but really resonated with folks.

[@3xHermes]

Very well done Shawn!!

[@rossr6616]

Excellent, thank you!

[@biffburley1]

Great talk!

[@Riverguide33]

Great review….excellent presentation! 👍

[@maryb345]

Thanks!

[@shawnwillsey]

Thank you for your kind and generous donation. Much appreciated and glad you like the content.

[@jettyeddie_m9130]

Thank you very much Shawn 🫡

[@davidduma7615]

Great lecture and I hope to see this part of the country. You deserve a KZbin following like Nick Zentner.

[@frankthomas855]

Fantastic presentation. Such a beautiful place!

[@Anne5440_]

This is a really good presentation! As I have mentioned this spring I've been studying the floods through WA state. Nick has been doing a lot on KZbin on them. His geology 351 class topic spring quarter was ice age floods. But he did cover the Bonneville Flood too. There are locations in WA that show evidence of the Bonneville. Your videos that I watched during the last winter had prepared me for the WA portion information. I have been working on reading more about the Bonneville Flood. This presentation has helped me greatly to create a mental timeline of the events. Your maps also helped me with locations in southern Idaho. I have personal history with Massacre Rocks. I saw it on the map. Did erosion from Bonneville cause those rocks to be standing alone in that flood plain? Yes Missoula floods are exciting and dramatic. But to me the Bonneville Flood is dramatic because it was so big for a much further distance and longer time period. I hope you will do more presentations, you are very good at it. They make a good overview of a topic. Your short videos are information packed and very personal with each viewer. The shorter videos cover specific features so well. Combining your presentations with the short ones makes a course complete on the specific topics. Thank you very much.

[@russtuff]

This was amazing

[@optitom9033]

As a Buhl Idaho resident Shawn's presentation of our great state is nothing more than amazing, like ti shake his hand one day

[@thomashendron4356]

Just purchased both books

[@shawnwillsey]

Awesome. Thanks and I hope you enjoy them.

[@chuckbouscaren3898]

What a great and informative talk!

[@shawnwillsey]

Glad you enjoyed it!

[@laurencelance586]

Fascinating!

[@pauldavis1943]

We used to travel from Corvallis to Cache Valley every year to visit grandparents. I was always memorized by the benchmarks and spent many hours contemplating Lake Bonneville...and the petrified watermelons. Never connected the two things.

[@mrdayyumyum3712]

Very good and interesting presentation.

[@ToddBeck]

Awesome. Answered my questions and generated more. Thank you!

[@shawnwillsey]

Happy to help!

[@causewaykayak]

This talk had me rivetted -- missed my breakfast totally !! Well worth it 🏆

[@shawnwillsey]

Glad you enjoyed it

[@runninonempty820]

Excellent presentation. I found this talk very interesting because my wife and I are planning to go to the area in August. I can't wait to see the flood evidence for myself. It should be a lot of fun.

[@shawnwillsey]

Awesome. Glad it was helpful and enjoy your upcoming trip.

[@stevehearne]

Go Bonneville Flood! 😊 Really interesting, followed along on Google maps. What a beautiful part of the world with awesome features nature has created.

[@rodchallis8031]

1:00:00 The question about the east had me thinking of Glacial Lake Agassiz. A little search indicated that Lake Agassiz had many incarnations as the Laurentian Ice Sheet retreated. The only flood-- and it was a doozy-- referred to associated with this lake was through current day Alberta, into the North West Territories and down the Mackenzie River valley into the Arctic. So, I would suppose that would qualify it as a "Western" flood. However, the last incarnation of Glacial Lake Agassiz drained via the Ottawa River valley and into the St. Lawrence. While that was a very significant event, I think we start to get into a philosophical debate about what constitutes a "flood". While the flow was on a massive scale, it might not have been as suddenly catastrophic as the Bonneville flood and the near by flood which shall not be named.

[@erinmac4750]

Thank you! I was trying to remember the name. I knew there was occurrence(s) back east. Now, I'll have to go on a deep dive comparison. 😎

[@JanetClancey]

This is brilliant wow mind blown a huge amount of water

[@sluggotinfantryman]

Best blathering on subject I have heard. By far. Excellent. Mount Logan to Toroweap is the one that is interesting. And giant plug at the end of Sullivan Canyon in gorge, Virgin River.

[@dannyrocket77]

I grew up in Soda Springs now in SLC I had no idea that the B. River changed course here and headed south. Amazing. I always loved geology. Wanted to do it as a career. I admire your work. Thank you for the education.

[@vickihubach4388]

Fascinating! A great talk and very timely -- I just got off the John Day river a few days ago -- the guides talked about the un-named other flood quite a bit. I had never heard of that one, but I brought up the Bonneville flood, as I've visited the Twin Falls area. I was delighted to find this video about it when I returned home. Thank you, Shawn!!

[@shawnwillsey]

Thanks for watching. John Day river is on my list.

[@sluggotinfantryman]

That river goes forever.

[@jdc8352]

I really enjoy your vids.

[@shawnwillsey]

I appreciate that!

[@asmith7094]

Very cool

[@Laserblade]

Excellent presentation Professor. Very educational, and You gave me an answer to a question regarding the sequence of the Bonneville and Missoula floods. Thank you sir - and thank you for bringing your expertise to KZbin for the benefit of untold numbers of us who share your interest in geology!

[@shawnwillsey]

Glad it was helpful! Thanks for watching.

[@Danika_Nadzan]

Great update on the previous Lake Bonneville video, which I totally enjoyed also. The Google Earth and drone views showed so clearly what you were describing--a sort of mini-field trip! My favorite part was Devils Corral, where your usual excellent description made it easy to see and understand the sheer force of the flood waters. The boulder bars were also eye-openers. Thank you for once again helping us armchair geologists continue our education!

[@Oregontrailblazin]

Thank you for the Idaho/Utah side fits in to Bonneville side .

[@jadefinchscene5644]

I agree, we need more attention to all aspects of lake bonneville

[@YouTubalcaine]

I went caving in some lava tubes out that way about thirty years ago. It's wild to be deep underground and consider that the earth under your feet was once a vast plain open to the sky. It absolutely boggles the mind how much landmass volcanism actually produces. With a thousand cubic miles of magma in the chamber I can't even imagine how terrible and widespread the devastation would be if the Yellowstone Caldera suddenly erupted in all its ancient fury. As impressive and awe-inspiring as the Bonneville Flood must have been to see, it pales in comparison to the forces of nature that shaped the land beneath it.

[@ivanivonovich9863]

Check out the info on the Siberian Traps, or the Decan Traps... Far more basalt flowed from those than all the calderas that proceeded the Yellowstone basin, (those calderas go west almost to the middle of Oregon).

[@YouTubalcaine]

@@ivanivonovich9863 I've been doing a lot of reading on the Karoo lately. It's hard to wrap my mind around the fact that, despite covering tens of thousands of square miles, the Columbia River Group is the _smallest_ flood basalt province. Crawling through old holes in the ground makes it seem like ancient history, but geologically speaking it's all rather fresh. It's really humbling to consider the scale of some of these events, both in area and time, but there's nothing like getting out and studying them in the field to make you feel like an insignificant speck in the universe. I just wish South Africa wasn't in such political turmoil these days. Lately it's been a bit hazardous to go tramping around the bush to visit some of these formations in person. It's sad, really. Human conflict seems like such a silly and fleeting thing when contrasted by the wondrous history of the land on which we live.

[@erinmac4750]

​@@YouTubalcaine Beautiful. Well said. It would be nice if our collective governments could just chill, so that we could appreciate the amazing people, creatures, and places we have on this planet. Sometimes I feel like they're babies at gourmet dinner busy chucking tasty morsels at each other and the floor.

[@Anne5440_]

​@Erin Mac I keep wanting to pass out big boy and big girl panties to the politicians that make up those governments.

[@MARILYNANDERSON88]

​@@Anne5440_too funny, I just slipped on my 'skinny' pants.

[@russelllombardy3648]

Just excellent. Content and delivery were fantastic.

[@88fjoe]

Great work and wonderfully presented, thank you

[@terreshort1158]

Im about to graduate from utah state university as a geology major. We know all about Bonneville due to evidence visible in Logan, with campus even residing on the Provo delta of the shoreline. Being an interpreter to give this kind of history in a national or state park is my dream. Now shorten the lecture to 5 minutes, thats what I want to do as a career. Well done

[@Josh1888USU]

Well, then maybe you can answer my question above. The cut that the Bear River takes at the dam that creates Cutler Reservoir; that looks incredibly unnatural especially when viewed from the Tremonton side. It seems to have taken a path straight through a knoll there rather than the lower land just to the north that seems like it would have been a much easier path to take. I understand that it could be explain by the river being there prior to the uplift of the range. The river having more cutting force and it just stayed where it was as the hills uplifted around it. So my question is how and when was that cut made? Is it something that predates the Bear River being diverted south through the Oneida Narrows and into Cache Valley and therefore it was cut by the rivers that are now tributaries of the Bear in Cache Valley (Cub, Logan, Little Bear, Mink, ect.); or was it cut after the diversion? Thanks and Go Aggies!

[@evelynmoyer9069]

This lecture helped reinforce the presentation you did for Nick Zentner . Thanks! 🙂

[@jhonbus]

41:35 This has to be the most valuable insight in this video.

[@toughenupfluffy7294]

I'm curious-since the Gilbert Episode apparently occurred about the same time as the glaciers to the north started melting away, is it possible that the rise in Lake Bonnevile was a pluvial phenomenon? Due to the overall increase in atmospheric humidity, the melting glaciers would've likely increased rain effects and added to precipitation events during this time.

[@ivanivonovich9863]

The area covered by the Lake Bonneville would indeed have been an area of higher rainfall in that time. Not just because of glaciation meltwaters, but because the climate would have been much more temperate than what is now desert.

[@elliswoodall407]

Interesting. I ❤️ geology.

[@codyhughes4472]

I’ll be exploring these two floods probably my whole life

[@5homegirl]

9 Feb 2024......While waiting for the update on Iceland I watched most the Nick Zentner joint venture with you. I pulled up your presentation of The Bonneville Flood and watched it on my 2nd screen beside your visit with Nick. Thanks, Shawn, for sharing your knowledge with us!

[@vinmansbakery]

Watching as a primer for the Zentner-Willsey broadcast tomorrow……and glad I did!

[@shawnwillsey]

Way to get the optional homework in. "A" student.

[@Rabidchu]

The part at 41:35 legitimately made me jump out of my seat lol Great presentation. I would love to attend a public lecture some day.

[@glenncourtney4876]

I live and drive thousands of miles a year for work through the area of the "Flood that shall not be named". I've also been through Red Rock Pass and stopped there for an hour and did some sight seeing. I have all those Missoula Floods books you showed and then some. Maybe it's time for a geologist to write a book on the Lake Bonneville Flood, hint, hint. My teenage daughter wants to go to Thousand Springs State Park this summer, need to find your video on it and send it to her. Last summer we did the MT Dinosaur Trail for our vacation. Love your videos and keep up your good work.

[@paulmryglod4802]

I was just there for the first time. Incredible place to visit.

[@robinbaum-hn2pc]

Thanks so much for you presentation. Having lived in Salt Lake City pretty much all my life,(73. Years) this has been the very first time through your wonderful graphics and great presentation I’ve really understood what and how the huge prehistoric lake leaked out into the Columbia River and left the now salt lake that this area is named for. Thank you so much for filling in the gaps in my knowledge!😊😊😊😊 1:19:50

[@shawnwillsey]

Glad to hear. Thanks for watching.

[@guitar1keith]

I subscribed. Please surf up Rick Sneddon's 3 part series on the well supported Big quake along the Wasatch Fault and the evidence of the Tsunami that accompanied it. It is arguably the single point in time starting the flood.

[@shawnwillsey]

Thanks and welcome aboard.

[@jackprier7727]

Thanks for another interesting explanatory voyage. I've admired the old poised lakeshores of the UT West Desert for decades, obviously something huge was and then wasn't-

[@tomolson1320]

I knew it! Shawn went to NAU and so did I! Go Lumberjacks!

[@lakefiftyseven]

At 44:17 I found that exact view on google maps. You go to 3D and then orient to the West. It's nice to be able to look around at Google Earth and see what you are talking about.....Maybe you could use that more.....Thanks..Great presentation. I love seeing things about the earth and geology. So much more is left to be learned.

[@dustychamberlain9739]

Interesting fact; the bear river is the largest river in north America to not reach an ocean.

[@oqsy]

41:36 made me jump 😂

[@Bombsuprise]

It's funny that when I was in college in the 90s the Missoula flood was still pretty controversial. Now it's the famous cousin, haha. I was at a rest stop in Utah this summer and saw a fantastic educational display about the Bonneville flood, which sent me down a new rabbit hole. Great video, thanks for posting.

[@snieves4]

Man i miss this content

[@WayneTheSeine]

I sure hope lower educational schools of today teach this, they certainly didn't back in the late 50's or early 60's. At 75 years of age, I have never heard of the Bonneville Flood. My only knowledge was the Bonneville Salt Flats for speed records. That was a big thing back then for teenage boys. What a shame. Great presentation. By the way Shawn, I have placed both of your books in my Amazon buy list for next months funny money payment.

[@paulmacfarlaneslp9209]

I think of the Bonneville flood as having been triggered by a huge spring runoff during the Ice Age, or maybe more likely a massive wind seiche causing ice to plow through the loose sediments of the previous stable overflow channel.

[@davidleadford6511]

Locals don't refer to it as the Pocatello Gap or Pocatello Narrows. Though it very well could be. They call it the "Portneuf Gap". Stinker Gas Stations still exist.

[@fallinginthed33p]

Thank you for this great video, it's the best primer on the Bonneville flood on KZbin. For me, the Missoula floods overshadowed the Bonneville simply because of how frequent they were, but the Bonneville's monstrous scale is mindblowing. In a way, it's too bad the Bonneville flood followed most of the Snake River drainage to the sea, instead of punching huge coulees out of basalt.

[@russward2612]

Much of my childhood was spent on the ancient shoreline of Lake Bonneville in Sandy Utah. It's called Sandy because there is, of course, a vast amount of sand from the lake. Where I live now would be about 800 feet deep when the lake level was at its maximum depth.

[@BlueInOrangeAgain]

thanks for the lesson; one recommendation would be to install or configure a mouse pointer highlighter.. Windows has a few defaults or you can get one specific for screen sharing stuff. Kinda hard to see/find your mouse when you're using it to point things out

[@Dragrath1]

Regarding the timeframe of the Missoula floods versus the Bonneville flood Nick Zentner is doing a geological series revisiting/adding some details to the Missoula floods. I'm not fully caught up on the series but one of the big takeaways is that the Missoula floods have older chapters including at least some reliefs which show pre Wisconsin glaciation episodes as overlying layers of calcrete soil horizons cap megaflood slack water deposits. The consequence of these findings is that the amount of eroded rock now gets split up by even more flood events and thus the floods might not have been as extreme as they would have to be to carve all of the coulees during the Wisconsin glaciation. At the very least it seems that the Grande Coulee was probably already largely carved out before the Wisconsin glaciation began. And there was a picture which shows the distinctive Bonneville flood deposit interbedded between both older and younger Missoula flood deposits. I couldn't help but note that Missoula slack waters carried far less larger rocks compared to the Bonneville slack water layer at lake Lewis. From Nick Zentner's A to Z series I do remember hearing about floods associated with the Hudson waterway system as well as floods in the Mississippi river system flowing out from the Laurentide ice sheet but that they aren't as dramatic/sexy since the rock types involved weren't as readily eroded to create such dramatic landscapes. Check out his livestream A to Z series. The guy asking about the salt seemed to me like he might have been mistaken in thinking the entire lake drained which would have removed the whole salt hopefully your clarification on the Provo shoreline resolved their confusion. In terms of the Snake River plain the seismic tomography images I've seen of the upper mantle beneath the western US Nick Zentner's A to Z series for the Eocene and Baja BC I can't help but note that the slow sheer velocity zone in the upper mantle below the snake river plain connects directly to the Juan de Fuca ridge via a zig zagging path through south eastern Oregon and northern California while on the other side it joins up with the Yellowstone Hotspot in what looks like an oceanic triple Junction the border of eastern North America and the Colorado plateau the Rio Grande rift valley and then darting through New Mexico and Arizona where it joins up with the East Pacific Rise beneath the Sea of Cortez/Gulf of California. In that sense the mysterious volcanism just outside the Snake river plain, and continued activity of the snake river plain is probably the effects of the underlying mantle. Fascinating if poorly understood stuff but the picture looks to be more complicated. (The timing of the onset of the Tertiary Ignimbrite flare up and the exposed metamorphic core complexes discussed in the crazy Eocene series certainly fits with the picture where the upper mantle and oceanic crust are interconnected with only really phase transformation differences in the absence of an overlying continent. Fascinating research stuff.

[@MaxPixUT]

Awesomeness! Thanks for this presentation Shawn, might be time to write that book? I'd sure like to see some CGI simulations of this event; maybe the AI can take care of that for us if you feed it all this great info.

[@roughout]

The flood waters flowed over much of the northside and entered the Malad river gorge north of the interstate southwest of Gooding. That's why there is a shortage of top soil over much of the northside.

[@shawnwillsey]

Small correction. The floodwaters on the north side of the Snake River (Eden Channel) re-entered the Snake River near Twin Falls and south of Jerome. The Malad River does indeed show signs of huge flooding events but not the Bonneville Flood based on ages and other evidence. Bottom Line: there is evidence for other spectacularly large floods besides the Bonneville Flood.

[@Barley150]

Magnificent, Prof. Willsey! First time I've seen, for example, a comparison between those two great floods. Could either or both of them occur again? -- charles johnson, sacramento ca

[@onthefive5615]

Very interesting to this amateur Arizona geologist; thank you! And it must be noted that you can't go wrong with a degree in geology, archeology or anthropology from NAU, ASU or UA. ;-)

[@jdc8352]

As a young kid in the mountains of southern Idaho.... I found it odd even then to find seashells in the mountain dirt. I only recently found out why.

[@Pudentame]

The Rodney Dangerfield of prehistoric geologic events.

[@lanereese9303]

I have been looking for a good presentation on lake boniville. What i took away on the 3 causes of the breach was probably saturation of the aluvium combind with a seismic event causing liquefaction and the flow of the deposits of alluvial landscape. So it could have emptied much faster than a few weeks.

[@stevebooher7419]

Great presentation! Did Shoshone Falls form during the flood or did it predate the flood? Thanks! Just discovered your videos - great stuff!

[@jodyfairchild5446]

Yes, this is better than your 20 minute Bonneville flood video. My question: where did the water come from that made Bear River such a huge river? Just draining Uintah and Wasatch Mountains?

[@shawnwillsey]

Thanks. There were glaciers in the high peaks of both mountain ranges, but yes the Bear River drains a large area.

[@jodyfairchild5446]

@@shawnwillsey thanks for the reply. My Grandparents had a ranch 7 miles north of Randolph, Utah. They had a hill that I know now was a sand dune. Grandpa dug into the side of the dune and made a shop/lambing shed. There were several large gullies that carried water in high water years that they dug into the bank of the gully for the privy. In the late 1940’s/1950’s it flooded and took out the privy and eroded the hole and its contents. I can see a braided river stretching across the entire valley. Thanks for calling attention to an amazing water way, Bear River.

[@craighoover1495]

Thank you Shawn. I too was raised on Air Force Bases the last one being Mtn Home AFB where we moved in 1970. I patronized Stinker Stations back in the time they were still operating and their advertising signs were legendary. Thanks for showcasing this particular one. I spent three years (disjointed) in eastern Idaho so I became aware of Red Rock Pass then. I learned more here from you than ever. Is the source for the water for the Bonneville event glacial? Bretz speaks of old ice sheet influence in the flood events in Washington. Could the water be from this source?

[@shawnwillsey]

Glad you enjoyed this and learned from it. The Bonneville flood was all lake water spillover (no glacial input). The high peaks of the Wasatch and Uinta Mountains had glaciers at the time of the flood but no direct connection between ice and the spillover at Red Rock Pass.

[@Josh1888USU]

Actually there are still Stinker Gas Stations. I stop at one all the time at the Gowen Road exit when you are coming into Boise.

[@markfults1693]

How come everytime someone talks about this flood they go into detail of its starting point to boise than skip the whole area from there to hells canyon?.. i live south of Fruitland with lots of gravel pits n always wondered if they have anything to do with the flood

[@FerozeDaud]

Dont understand something. So I get it that lake bonneville overtopped it's shoreline and flooded. But once the volume of water had reduced enough, so that the water level went below it's shoreline, or rim, the flood should stop, and lake bonneville should still have been there. I do understand it is not there right now. But I was wondering why it totally drained at that time? or did it?

[@shawnwillsey]

Lake Bonneville overspilled and cut through Red Rock Pass until the floodwaters reached hard bedrock which slowed then ceased the downcutting and ended the flood. The lake may have rose and fell a bit and occasionally spilled a bit of water over the divide but never really caused a large flood. Then the climate changed, warming and drying, and the lake shrank, eventually becoming today's Great Salt Lake.

[@davidk7324]

Since your prior Bonneville Flood videos I've wondered what would have happened had the Bear River not been diverted southward. No flood and a much larger Great Salt Lake remnant?

[@shawnwillsey]

Very likely that no flood occurs without the Bear River's input.

[@ritaswedia399]

👍👍👍👍

[@mashak640]

Is there a link to somewhere to buy your books? I'm absolutely obsessed with your content. Finding this video as an update to the Bonneville flood video from 2 years ago made me SO excited that I cannot contain myself

[@mashak640]

Autism moment: how do I explain to people that my special interest is the great basin and lake bonneville 😅

[@shawnwillsey]

Here you go: shawn-willsey.square.site/

[@mashak640]

​@@shawnwillseythank you!!

[@DRY-C0WB0Y]

For anyone wondering how peak flow of Shoshone Falls compares to the Bonneville Flood (I did after staring at that picture of it), Bonneville was about 3,000 times more massive.

[@dr.fidelius2905]

Re an earthquake trigger, liquefaction: if the soil/rock material that is acting as a dam for Lake Bonneville has a groundwater layer, this subsurface layer will effectively liquefy during earthquake shaking, due to the temporary compaction of the overriding soil/rock layers thereby causing an increase in pore water pressure in the groundwater containing layer. This can cause catastrophic loss of soil strength during earthquakes - earthquake engineers can tell you all about the liquefaction phenomena.

[@danniegibbs6535]

I just watched your video, because ive been watching nick about Missoula flood. I see the Bonneville flood was backed up down here at the wallula gap, was there Bonneville water still here at wallula gap when the missoula came later? From my understanding the wallula gap wasn't cut out till the missoula flood. Thanks

[@sluggotinfantryman]

It makes one realize what we have on Antarctica. Possibly the biggest river on Earth 🌎 and lake if middle is dented from weight.

[@pamelaspelbring6297]

I cant imagine the size of this event. Too many zero's. The earth in all its glory.

[@davemi00]

Awesome and Interesting presentation I thoroughly enjoyed learning about this. I watched thinking it was another man made disaster.

[@johnnash5118]

Is there evidence of a “Bridge of the Gods” type landslide occurring in Hells Canyon during the initial passage of the Bonneville floodwaters which may have created a temporary lake behind it?

[@shawnwillsey]

Not to my knowledge.

[@jettyeddie_m9130]

This could of been 10 hours and I would of watched the whole thing 2x

[@shawnwillsey]

Wow. Thanks for the kind words. Glad you enjoyed it.

[@daveisnothere]

I've spent the last 10-12 years looking at a lot of the information relating to the Bonneville Flood. A lot of the evidence I have seen makes the flood, as described to us, impossible, or at a minimum, a lot less violent than we have thought. It would take me an hour or so to go into all of the details I've seen, but I'll summarize here. There are multiple shorelines north of Matlin Park (almost straight west from Promontory), 40 feet apart until it drained down to 5000' elevation. At this point it appears to have slowed a bit until getting down to the Provo level at 4800'. This makes sense because of the ridge between the Cache Valley and Great Salt Lake Basin has an elevation of 5000' at it's lowest except for the cut at Cutler Dam. This cut had me confused for the longest time. From the evidence I've seen it seems it was cut near the end of the sequence of events in question partly because it ended up at 400' below Red Rock. Near Beaverton there is erosion which appears to be caused by a significant amount of water flowing both directions over this ridge, westerly after the Cache Valley was filled by the Bear River and then easterly after the water in the Cache Valley drained and the Great Salt Lake basin was still spilling over. There is an older drainage channel cut at Red Rock Pass that starts near the town of Oxford at about 5000' elevation. Judging by the amount of erosion on this channel it is significantly older than the channel believed to have been cut by the Bonneville Flood. This channel's elevation is the same as the ridge mentioned earlier. Based on this, and some other things I've seen, the draining of Lake Bonneville took a lot longer than we have thought.

[@Josh1888USU]

I wonder if the Bear River cut between Cache Valley and the Salt Lake basin predates Bonneville and maybe even the formation of the range between the two as well? I think that might explain the odd way that it cut through the range there. That would assume that the erosional force of the river was greater than the uplift of the range as it was forming. That river wouldn't have been the Bear as we know it because the main part of the Bear that we know would have been flowing to the Snake through the Portneuf as shown in the video. Rather it would have been the combination of the other rivers that are now tributaries to the Bear in Cache Valley (Logan, Cub, Mink, Little Bear, Blacksmith Fork, ect.). So maybe that cut is way older than anything to do with Bonneville? You may still get the erosion over the ridge there depending on how fast the cut could drain after the main part of the Bear was diverted south through Grace and the narrows.

[@daveisnothere]

@@Josh1888USU I wondered about the age of that cut for quite a while. There are deposits from this cut on the Cache Valley side so there was some erosion as Bonneville drained into the Cache side. There are some erosional features SE of Beaverdam that kinda make me think there was a decent amount of water flowing both directions there as well. Most of the Cutler cut is below the Lake Provo level which means at least that part had to be eroded after the GSL side evaporated down between the 4800' and 4400' level. Lake Provo being 4800' elevation. The cut has steeper walls, which means it is relatively young compared to the erosion on the sides of that ridge. If it was older it would have prevented water from moving over in other places and also would have had more gentle slopes from being eroded more during the time the Cache and Bonneville sides drained. Cache would have filled first, then it would have spilled over into the GSL basin and then the process would have reversed when they both topped over in Red Rock, until both drained down to 4800' then this notch would have been cut as the Bear River and/or "Cache Lake" drained into the GSL basin.

[@Josh1888USU]

Awesome lecture! One thing that I have a question on is how did the Bear River produce the cut that it does between Cache Valley and Tremonton? If you are familiar with that area you can see that the cut of the river there is odd because it appears to cut through the rock at a point that one wouldn't think would be the path of least resistance. Interesting to learn the time line of that after now watching this. I would imagine that some of the cutting happened before the flood and after the Bear was diverted, and then started again after the flood and the lake level dropped to its present day level at the Great Salt Lake. Take a look next time you are through there and I think you'll notice what I am talking about.

[@daveisnothere]

I am glad I am not the only one who noticed this anomaly. I've looked at the area around there and determined it had to have been cut near the end of the cycle of events in question. I am doing a long comment in a bit that will discuss this in more detail. One thing to consider though, before the flooding there was really no reason for water to move between the Salt Lake Basin and the Cache Valley.

[@shawnwillsey]

As Lake Bonneville dropped (eventually becoming GSL), all rivers and streams that fed into it downcut through sediment and/or rock layers.