HUGE Boulders Transported by a Megaflood in Southern Idaho: a geologist's tour
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- Опубликовано: 25 июл 2024
- Geology professor Shawn Willsey takes you on a tour of the "petrified watermelons" or Melon Gravels, the huge boulders deposited by the massive Bonneville Flood of the Pleistocene. Learn why the size of the boulders varies and how the boulders were shaped by water and sediment. For a more comprehensive presentation of the Bonneville Flood, go to
• The fascinating story ...
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Shawn Willsey
College of Southern Idaho
315 Falls Avenue
Twin Falls, ID 83303
Approximate GPS Locations:
Intro and sign: 42.97521, -115.15911
Cliff: 42.94861, -115.16055
Boulder Bar: 42.95074, -115.16303
00:00 Introduction to Melon Gravels
02:38 Huge boulders atop basalt cliffs
08:40 Boulder bar near Snake River
11:56 Up close view of asymmetric boulder
12:17 Explanation diagram 
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That amount of water moving boulders that size is unfathomable!
There should be one of these boulders at every school in the United States with an explanation of where it came from and how it was formed. Great video, this has been very educational.
I have installed irrigation projects on farms around there. Downriver about five miles from this melon location, there are massive pea gravel deposits covered by about 6 feet of sandy silt dirt. A lot of bumper crop Idaho potatoes have been grown there.
It's amazing how much geology you can learn by just looking closely and using a basic understanding of how water flows and rocks erode! Thanks!
That's right Kevin. We can learn a lot just by observation. As Yogi would say, "You can observe a lot just by watching".
Love that sign about the petrified watermelons. It never gets old and thanks to sign painter Gus Roos for coming up
with the saying. Imagine the scale and volume of water that occured 17K years ago to move these rocks and push
these boulders. It would best be described as an action due to the Venturi effect. Thanks for showing and explaining
this area of Southern Idaho Shawn.
Watching your videos from Missoula, it's amazing how different Idaho and Western Montana can be geologically.
So true!
I recall seeing that watermelon sign when I was young but never saw it later. Now I recognize this coincided with the freeway being built.
Thanks Much! I love to follow along on my favorite aerial photography app. This site was easy to find due to the interstate bridge (and train). Could you include coordinates on future installments? Geology ROCKS!!!
Thanks for watchin. I'll add GPS coordinates to this video's description.
Thank you Shawn, doing a Great job! Always interesting details you bring us along to see and learn about!
I appreciate that! Thanks for your support and viewership.
I never knew watermelons could be petrified. Thats amazing
They are much sweeter that way. We call them "Watermelon Brittle".
Your travel lectures are an inspiration to me. l like your diagrams of events, they really help to visualize the formation. l wish you would go to Pennsylvania to the South Mountain Rhyolite Formation near Gettysburg and explain it. l spent a lot of time there as a field archaeologist trying to define why some areas were utilized for lithic tool production by the original people but the vast majority of the formation was bypassed by them.
I Didn’t know i could be so interested in geology! It’s fun to watch you go around southern Idaho! It’s where I grew up and visit quite often. Very cool to understand how all these beautiful places are formed!
Thank you, Shawn, for another great video!
Glad you enjoyed it
Thanks for your efforts. You clear up so many mysteries about our wonderful planet.
That was a very clear and informative explanation. I have mentioned in previous comments that I'm an older guy with no geology background but I just have a deep interest and fascination with the geology I see out on hiking and backpacking trips. Often I see things while out hiking and I am quite puzzled by the features. So I go back and search through my geology field books to try and make sense of things. But journeying with you, a real geologist, on these field videos makes the features so much clearer and enjoyable. I have seen landscapes just like in this video while out in the Eastern Sierra of California. I thought maybe the giant boulders shot into the air by a massive eruption. I wondered why they were shaped with a shallow slope on one side and a steep slope on the other. I have seen similar striations and thought maybe some sort of partial metamorphosis. Now after watching your demonstration in the field, it all seems so obvious that I wonder how I didn't see it myself. It is all so much more exciting when you understand what you are seeing. Thank you.
Shawn, Thank you for your wonderful videos. My husband is retired geologist and we have been on one of your guided walk abouts with IMMG. But you are a professor first class. You make geology rock(pardon the pun) but you are the instructor to light fires under younger people to learn more about our earth and it's surprises and secrets. You make learning geology understandable and with enthusiasm. Keep up your wonderful work. Any plans this year for a walk about with IMMG?
Thanks so much for your kind words. These videos are just an extension of what I do at the college but allow me to connect to a much wider audience. I love doing IMMG trips. They can contact me anytime to set something up.
Thank you Shawn! I need to catch up on all the videos! Good way to spend Saturday!
Enjoy!
That is particularly interesting in application for me as a placer miner. Thank you!
Living here in Southern Idaho I've seen them a lot. I always tried to figure out how a volcano could have blown them that far away, really enjoy learning about the geology of Idaho..
Hi Shawn. Interesting area. Great explanation.
You help us see with expanded vision. Geology is just huge!! You're a great teacher, Shawn. Thank you.
Wow, thank you! Appreciate your viewership.
Your vids are fascinating and terrifying at the same time. I'm a local. I enjoy them. It explains a lot of what I've stared at my whole life. Thanks for the vids.
Greetings from the BIG SKY. Been thru there many times and it's a neat place.
Excellent lesson and explanation. Thank you sir.
You are very welcome
Very nice lesson. Great information, well presented. It saddened me that you left out the story of Fearless Ferris Lind, the man who created the watermelon sign along with many other humorous signs planted all over southern Idaho.
Outside of king hill. Love that sign. Thanks for the lessons today. Appreciate you learning us a few things
Really enjoy going on these field trips from my living room.
Thanks for watching and learning with me. Enjoy!
Thanks Shawn! On some of the boulders you can see impact marks where smaller stones smacked them.
Thanks Shawn. Nice talk.
Thanks for the info on the backyard 👍
Thank you again Shawn.
As always, thanks for the interesting and informative video. Couple questions... How far up stream is the estimated source of these melons and larger boulders? And what is the estimate of how deep the water was rushing over the area during the flood event? Oh ya noticed you in the chat the other day on Nick's Baja/BC series. Keep up the great work!
Nick's last two sessions with Bernie Housen has melted my brain. I'm left to take everybody's word for it re: the efficacy of paleomag because they got so deep in the weeds with it my feeble brain couldn't keep up. When I need a break with geology I can get my head around I can always count on Shawn -- can't wait for his next video.
@@briane173 Lol... agreed. I also found it hard to follow and am in over my head on the paleomag, but will continue to watch the series because I randomly found and have enjoyed Nick's presentations for several years and have learned so much. I found Shawn on RUclips about a year ago or longer and have very much enjoyed and learned from his videos as well. He does a great job! Seems I cannot get enough geology these days and have other channels I follow as well. I was an organic vegetable farmer for 25 years after studying biology, soils and finally horticulture at UW-Madison. Now only farm part-time. I find it refreshing to learn about geology at my age (61) after being a rock hound since I was a kid.
@@farmermark2067 My avocational interest earlier in life was meteorology; but about 12 years ago I started getting interested in geology, after I discovered that our cabin in Mammoth Lakes, CA was sitting inside a supervolcano. And now that I live between Mt St Helens and the Cascadia Subduction Zone I became REALLY interested, for parochial reasons. To discover these two great _teachers_ in the course of my research and study has been a bonus. Two great _teachers._
Yup. For sure. I live in central Wisconsin. Not much going on but close flat land glaciated with all the named features. Sandstone buttes south a ways in the central sands outwash plain, , As a kid my parents took us on "pic nics" a little ways away and got to climb on a relic sandstone butte called "Rabbit rock which is one of many in our area. You are so fortunate to live in the geology you do. My big thing is knowing that close by we have 2.8 billion year old archean gneiss from the Marshfield supercontinent (road side geology of wisconsin) below a dam in Stevens Point. I want to go west and see that geology.
Good question. Determining exact source of boulders would be difficult since 99% of them are basalt and there were hundreds of eruptions of basaltic lava throughout the Snake River Plain. However, when you consider the speed and energy of water through the narrow sections, it makes sense that most deposited boulders were sourced in the narrow canyon section just upstream. At the location of the video, the flood water was about 250-300 feet deep (above river).
Yeah, made it to one of Nick's livestreams when I had some time but this semester looks to be very busy: six classes, 5 presentations, trip to Yellowstone, trip to S. Utah, and then back to back Hawaii-Iceland trips in May. Plus trying to get some videos done at these locations and others. Not sure I will be on many of his livestreams, unfortunately.
When I was growing up in Boise decades ago, Stinker Station signs were the highlight of any trip we took through the Snake River Plain. I don't remember if that "petrified watermelon" sign was in the same location then (it very well may have been), but at the time, someone had painted a couple of the rocks underneath it green.
For those with questions about the flood, Shawn has made a couple of videos covering it in great detail.
This is a good one Shawn. Thank yo!!!
Great video! Thank you
Definitely a huge "water event". I've run into really huge boulders that were left behind along with the other sizes in a now "dry channel" of the Sinks Canyon, outside of Lander, Wyo. On the other side of the bluff/high hill, is the existing Popogie River. Really is a quite "eye thrilling" as to how that canyon was formed.
good video Shawn!
Astounding amount of water to move stones that huge! Wow!
My ancestors in the uk built field wall boundaries with this kind of debris.
Great class!
Many thanks!
Always super clear explanations. Thank you!
You're very welcome!
Thx Sir Willsey. ✌
Excellent video, so informative and interesting.
Glad it was helpful!
Good show Shawn!
Thanks Paul!
Thanks
Thanks, I use to live in Idaho near to Melba on a road about a mile from the entrance to the Owyhee mountain range. I worked for a ranch on the Snake river.
*Let the Sunshine In...*
.
Funny how most places don't want you to take home any of the rocks. Here you can take one home to your mother-in-law (that is, if you can lift them).
Thanks!
If , like me , you were an English/arts major and must take a science elective , make it a Geology 100. Nothing will change the way you see the world as will a basic geo understanding. And you get field trips.
Thank you!👍🏻❤️ i can't not say that the roundish concavity on the rocks resting up top look chillingly reminiscent of ancient river rock.
No problem 😊
Fantastic. The energy of the flood was massive and sustained. What is the best estimate for the amount of time elapsed from the initial break at Red Rocks Pass until flows from the Snake into the Columbia normalized?
Estimates for flood duration range from a few weeks to months of high discharge, tapering off within a year.
@@shawnwillsey Thanks Shawn-- quite a sluice box.
Does anyone else go boulder jumping? It's just where we go to a boulder Field and you have to jump from boulder to boulder without touching the ground. Kids love it and it's good exercise.
Great video. Very interesting.
Glad you enjoyed it. Thanks for watching and learning with me.
Picture this landscape, only under about 400 feet of water that's moving 35 _million_ cubic feet per second, or about twice the amount the Colorado River historically discharges in an entire year. Every second.
you rock Shawn- still waiting to hear about Sand butte- South of Preacher bridge west of Carey- but the melon rocks down stream from Swan Falls, south of Kuna and into Centennial park and up stream to Priest ranch with petroglyphs are really
some amazing rocks
So many places to get to. Swan Fall and Celebration Park are on my spring list.
Once again
Makes me want a class b rv
To take along behind and see
Verry interesting
Nice. As an amateur geologist I find your explanations fascination, especially since I live in the general area.
Glad you like them!
Rockin' in the Free World
Thanks! Nice narrative and MELON GRAVEL too!
Thanks for your kind donation. Much appreciated.
Well done! Is this public or private land? I'm marking a map of places to see and it would help to know the "no-go" places. Thanks! 😀
Hi there Greg. The boulder bar and cliff band are on state land but accessed by a road that is private. If you want to see fantastic Bonneville Flood boulders, head to Swan Fall and/or Celebration Park (southwest of Boise). I'll try to get over there this spring and do another video. Other good Melon Gravel locations: Auger Falls park near Twin Falls and "Melon Valley" around Buhl and Hagerman.
@@shawnwillsey Thanks! :)
You should get drone to provide a larger view of things like this Boulder field. Really enjoy your videos. I’ve always thought idahoho has the most interesting geology of any state in the lower 48
Was there only one Bonneville Flood? Was all this erosion and shaping accomplished in one event? How many hours were these rock subjects to the unidirectional erosive forces?
Yes, just one flood event (but huge). Flood duration is estimated to have lasted several weeks to months.
There are similar flood zones all over the. In souther California there are massive alluvial plains where flood soils settled out in hundred of feet in depth. Mixed in with the soils are smaller builders and further up in the passes larger boulders
Might get another one pretty soon. Nothing is forever.
There are some granite borders size of houses in So cal they gonna find somewhere else when the snow is done melting this year
As I watched, it occurred to me that the large, asymmetric rock you focussed on was a bit reminiscent of a basalt column. Would there be columnar basalt around the narrow canyon area?
Columns do form in places so it is a possibility.
Love your videos. Just need Dremamine with the fast panning.
Yeah, working on that. I think I get too excited. Thanks for your patience. My degrees are in geology, not videography. 😉
Seen those in Kansas too... They're massive...
The one on your thumbnail.. not the watermelon ns kind...
I believe the large spherical rocks in Kansas are concretions, formed by a different process, but equally impressive.
I'll have to revisit the genesis of the Bonneville Floods, but it's more than a little ironic that it would have occurred so close to the time the Missoula Floods began to happen much further north.
I do like the theories that some giant bolide meteor or cometary fragments caused a near immediate melting of the ice sheets and catastrophic flooding. Definitely helps explain a lot of the fauna extinctions around the younger dryas, too.
@@svendragon8139 that meteor idea is one that lacks every form of evidence
In a way they are related in that the cool climate allowed the ice sheet to grow and advance southward, cutting off the Clark Fork River and setting the stage for the Missoula Floods. At about the same time, the cool climate allowed Lake Bonneville to grow larger and rise as precipitation outpaced evaporation. Other than that, no other connection.
@@harryromo2508 We should have many competing theories concerning the younger dryas put to the fire of the scientific method. Only the truth survives true investigation
Hey Shawn, have you ever looked at the hills to the immediate east of Cold Water Hill on the south side of I-86? They have lines on them that look like a lake might have been there at some point. I was wondering if the Bonneville flood formed a temporary lake there. The river is only a few hundred yards away so maybe that's what formed them. I drive by that area when I drive from Blackfoot to Twin Falls once a month. I always look at them. Do you know anything about them?
Hi your are right by our ranch. The devils tail. If you went down below train tracks your where on our ranch.
Very interesting! Is there an estimate for how long the flood took place? I'm guessing a long time considering the amount of erosion.
Estimates are that the flood lasted several weeks to several months, perhaps a full year.
This is fascinating, and you did a great job laying out your explanation!
Where are the boulders from? They sit atop a pre-flood basalt and the boulders look volcanic; are they the same basalts displaced and eroded as you talked about?
Good question and I probably could have explained this better. Flood filled entire canyon here, even higher than the cliff band and had enough energy to transport and deposit boulders on the cliffs.
We have big boulders of fine grained Dolomite (?) around here in some areas of Johannesburg that are on the surface and others that have been exposed in earthworks. They are all very rounded and displaced well away from any formations, please help me solve this puzzle! Can send pics. Most have the characteristic brown weathering crust.
Would colliding with ice help shape rocks also?
I wonder how deep the pile of watermelons goes?
Boulder bars are at least tens of feet think in some places.
Behind the Palisade Dam I saw a boulder washed down a canyon size of VW bug
Did the flood also greatly modify this channel from close to the same elevation where these boulders are today? Perhaps the Paleo-Snake was in a V-shaped valley @250’ higher, which enabled the flood to deposit these boulders to the side rather than vertically.🤔
Possibly. It's hard to know what the pre-flood canyon shape was like. Wide areas were likely filled in more than eroded but narrow canyon sections were widened and deepened by some amount.
Thanks great video again! Is this close to the area where there are these mega-huge current ripples (also caused by a flood)? (is this as controverse topic as BF is for criptozoologists?)
The Missoula Floods (up in eastern WA) has the classic megaripples. The only ones I know of from the Bonneville Flood are in Hells Canyon.
@@shawnwillsey Thank you very much!
when the river passed the narrow and broadened, why did it not create a river delta like feature. on the broadened field area, are they lying on the river bed, or is there aggregate below them...
Deltas form where rivers end like at a lake or the ocean. The river's velocity goes to zero so most sediment is deposited, forming the delta (similar with alluvial fans too). Here, the floodwater slowed entering the wide valley but still had quite a bit of velocity. It deposited the big boulders here but still transported softball sized gravel along with sand.
@@shawnwillsey I see it now. FYI: a drone would be a handy tool for you.
Rock only become rounded when they collide with other rocks................There is another mechanism. Not for these. But in other geologic settings. Concretions, some quite large in sedimentary rocks.
True. I guess. I should qualify this as the only process in erosion settings. Good point.
@@shawnwillsey Doesn’t some sharp angled outcrop tops weather into roundish tops, such as columnar basalt? Perhaps yet another way to erode sharp into smooth?
Would need a lot of salt for those watermelons. Maybe some tenderizer sauce as well.
7:50 The energy of flood is one million locomotives.
How do you know the Bonniville flood was that long ago?
You took John parke loop rd. If you would have come to the house we could have given you more info. Our family has been here since 1947.
Did you see the Indian caves? You are right on top of them. Please reach out to us. The Parke family
Good to know. I’d love to meet and talk geology around your property. Email me at swillsey@csi.edu and we can set something up this spring.
How long did the actual flood last?
Estimates are several weeks to several months of high discharge.
👍
Nice video. I have a question. How long did the flood last? Days weeks months. Seems it would take awhile to erode those boulders into that incline shape. But maybe the huge forces could do it quicker. You probably covered that in some other video but just asking
Flood duration estimated as several weeks to months of high discharge.
do you believe that the bonneville flood was a one time event, or many floods as we have been taught???
Yes, Bonneville Flood seems to be a singular flood based on evidence. Missoula Flood in northern Idaho, formed my an ice dam, occurred repeatedly.
What about glaciers?
No evidence of glaciers anywhere in Snake River Plain (elevation is too low). No moraines or till. No striations on bedrock. There is plenty of evidence for alpine glaciers in Idaho's mountains but the glaciers terminated in moraines around 7,000 ft in elevation.
I am curious how a geologist thinks about the work done by Randall Carlson. I know he might run with some fsr out people sometimes but he seems to have a good understanding of geology and hydrology. But for a layman it's really hard to tell.
I agree that it is hard to discern what is credible and what is not. Especially when folks sprinkle in just enough science jargon that it sounds legit. They often cherry pick data/evidence that supports their conclusion (usually a sexy, dramatic thing like floods, impacts, etc) rather than let the evidence lead to testable hypotheses. I'll leave it at that for now.
what is the duration of this event , to create such dramatic evidence? to me, it was a HUGE event lasting a very long time.
Estimates are weeks to months. The lake was huge so draining the upper 400 feet through a narrow gap would take some time.
Are all the boulders basalt?
Yes. Although near Twin Falls there is a few rhyolite ones mixed in.
I wish he would have followed the trail BACKWARDS as to where all the basalt rocks came from. Canada to the North?
No, upstream a few miles along the snake river canyon.
You hinted at telling the provenance of these rocks...is it not Twin Falls?
Most of the Melon Gravel boulders are basalt and were ripped or plucked from the cliffs of the Snake River canyon. Usually most of the rocks in a boulder field like this likely were sourced from the narrow canyon section upstream.
Coffee Stipend!!!
Much appreciated. Thanks for the support.
What do you think about the theory of the pole shift every 12000ish years? Have you seen anything in the geological record to support it? Could the Bonneville flood been a part of that?
There is no validity to the pole shift idea. There is no evidence that Earth's rotational axis (currently at 23.5 degrees) changes drastically over geologic time. It fluctuates slightly between 22.1 to 24.5 degrees (known as obliquity) due to gravity from Sun, Moon, and other planets. This has a very minor impact on seasons. If you are referring to shifts in the magnetic poles, there is no effect of the magnetic poles reversing from north to south (which they do often over geologic time) on seasons or climate.
The Bonneville Flood occurred because a large lake in an enclosed basin (Lake Bonneville) grew and overspilled.
Thanks for sharing sir. One doubt sir. Is these ice age effects or transformation of earth occurring on West side of the globe. Will we find same features on East side .. Europe and Russia also? If not Why?
Did the bonniville flood cause lake Idaho not to exist?
They occurred at different times. Lake Idaho was around intermittently from 10 to 3 million years ago then drained as the Snake River became a through flowing river system and connected to Columbia River. Lake Bonneville is younger than Lake Idaho.
@@shawnwillsey thank you for the info, do you hear much about the ongoing battle between twin falls water district and Bingham county area? If so it would be very interesting to hear your thoughts on it and what you think would be a good solution if there is one.
The event that caused this formation is reletively recent in geological terms, wouldn't you say?
Gold bearing gravels? Lol