Learn how Supervolcanoes caused the World’s Largest Landslide in Wyoming

well welcome did you know that 50 million years ago about 50 million years before yellowstone yellowstone eruption occurred only about 600 000 years ago but 50 plus million years before a yellowstone occurred there was even a larger volcanic system in northwest wyoming and the vicinity of yellowstone it overlapped some and they were gigantic strata volcanoes huge tall ones 20 000 feet high above the basin floor and there were a series of them and and they were very explosive and they had a habit of creating landslides and one of them turns out to be the world's largest landslide which is referred to as the hart mountain slide and so we're going to learn about this amazing geologic feature and see just how it happened and see where it happened so i'm excited about this i think it's time to get going let's go okay i want to start by orienting ourselves in the world this is a view and a google earth view of the northern united states and the state of wyoming is outlined in this blue now we're going to zoom in here as we rotate in we're going to focus on the northwest part of wyoming where yellowstone park happens to be and this red outline you see that is the mass of land that broke free and many large blocks slid out from that area continuing to zoom in we see some more features here first of all i want to point out these green outlines the big one is yellowstone national park and the smaller one next to it is grand teton national park of course we see the red outline of where everything broke free and to the two green dots out there are landslide blocks some of the blocks that slid out i've just highlighted a couple there many of them the small green dot is heart mountain and the two yellow splotches here very interesting because those are two of the big active volcanoes in that particular area at the time okay so here we are at the famous hart mountain here behind me the mountain behind me i say famous it's famous at least in the local community it's well known uh because of over the years there are many geologists that have come and studied it and their little write-ups in the local papers right in the geologist community in the structural geology those specialized in studying the earth deformation and things it's very very well known the broader geologic community not so much which is kind of amazing to me of course i'm a bit biased because i grew up in this area but uh hart mountain you know it was well known to me as a kid could we drive into cody i'd look at that mountain pretty much every time driving in to get our groceries i go you know that looks like a witch lying on her back with a big old word on her chin so my imagination was working on heart mountain early that all that said if we come back to the geology story what many people of course the locals that aren't specialized in geology and stuff but even many many geologists don't really know that hart mountain is a very small part of the bigger picture it turns out hart mountain is just a small little piece of the big the big landslide it turns out that this mass of earth that came detached and came screaming out as i like to say into the basin i was 20 by 30 miles in size or so 800 plus feet could be two three four thousand we're not sure there was huge pi it could be several thousand feet thick of volcanics that were on top volcanic deposits and all that that came rushing out it was just it must have been unbelievable and i'll i'll reveal a little bit more right now and that was it also came out at very high speeds modern work and modern technologies that we're able to do the geoscience the geology community have been able to show that so what an amazing story i'm sure looking forward to having you along with me to learn about heart mountain and the largest landslide on earth even part of it is in yellowstone national park believe it or not everyone knows about yellowstone but we're going to start off by going over to mccullough peaks here now nearby and there we'll start talking about get more into detail about this amazing story this this is going to be fun let's go and here we have in the beautiful badlands one of the mccullough peaks and just to the left is hart mountain [Music] [Music] well i've made it made it here done a little brief hike down from the pickup truck down into this little hollow near the top of mccullough peaks and this is where we get the first perspective of hart mountain so hart mountain is back through that notch let's see if i i can point to it uh somewhere over in here hopefully that's about right uh heart mountain back in the background and in the foreground are these beautiful red uh red beds of the wilwood formation which are quite young okay about 50 million years old or so so that gives you a setting um and a feel for the landscape right here in this immediate vicinity but heart mountain is so fascinating and i like to think about it from a geologist's perspective and what it would have been like to hike out here and observe this as a geologist that first was unfolding the geology out here at the turn of the century these early geologists like darton and others that were out here studying the geology of the bighorn basin and that's why i came here in particular because i want you with me to think about what a geologist saw and how they might think about well what's going on here okay over here at heart mountain okay so to start off i want to have start with a basic understanding of stratigraphy and how geologists think about the layers of rock or what we call stratigraphy so i'm going to grab a board and here is this stratigraphic column that we call it that's the age here starting from the oldest and going to the youngest these are the age names that some of you may be familiar with and this is the names we give names to all these layers they're kind of like our own babies we know these like the back of our hand like our own kids they're very distinctive these big layers of rock just so you get an understanding this blue light blue layer here happens to be 400 feet it's the maori formation in this case some of them this shale here can be 2 000 feet thick called the cody shale so each one has its name and has a typical thickness out here in the bighorn basin now so with that in mind the old geologist back in the day i like to imagine they came right out here right where we're at right now and i want i want to have you think a little like a geologist and what it might be like i know it's interesting to me and that's kind of the way i think anyway so here we are the geologist and i'm we're standing here and he's standing here and we're going with now basic geologic knowledge we look over at heart mountain and we go uh what what why am i saying what let me give you a clue since these geologists know these light rock layers i mean they're distinctive they can see they can tell them many miles away usually right he's going i gosh heart mountain over here i know what it looks like it looks like it belongs from down here in the bighorn dolomite which is about 400 million years old and you're thinking well okay so well there's something interesting i've shown you all these red beds around here right to start off these banded beautiful red beds well it turns out if you hike over here and you can see it from here but especially on the other side and he would kind of understand that a geologist would that these red beds are sitting right underneath hart mountain and what that means these red beds are up here they're 50 million years old and we're observing rock that's way old that belongs way down at the bottom clear at the top here now how does that happen so in other words let me try to simplify this even more the geologist that's knowledgeable goes the rock that's sitting up there on hart mountain should be 15 000 feet underneath it not right right where it is okay so now we have now we have a problem don't we an exciting problem first of all as a geologist you're going well i could be wrong maybe there's a layer of rock over there that looks an awful lot like the bighorn dolomite that's completely new that's very young or something strange so i've got to go over there and verify what that rock is as i'm standing here you know 15 miles away or whatever it is okay that would be the first step of course but i'm talking here assuming that it is this old rock with you guys okay so wow there are different ways to get old rock on top of young rock and immediately the geologist would be going uh uh gosh if that really is bighorn dolomite if that really is this old old rock sitting on these young beautiful badland rocks there are about three ways to do it and that's i'd be immediately thinking this way and going well the first would be a big landslide off the steep front of a mountain you know where you have old rock that's been pushed up way up in the mountain and there's young rock down low in the valley this big rock just comes off and goes down on top of it the other one would be a thrust fault and that is uh very quickly and i'll repeat it later is that when rock if my hands are layer rock and you compress them they can break like this literally just kind of break along a fault and one big section can slide on top of another and you can get old rock on top of young rock okay uh and actually many geologists thought that could be the case here at heart mountain for quite a while until it was studied more and then finally the third option which ends up being what happened as these geologists studied it more and we'll go kind of act like we're early geologists that's kind of fun is another type of landslide called a low angled attachment the rock slides on a low angle detachment from some place high and gently slides out in this case into the basin and old rock gets way up 15 000 feet above where it should be in the in the column in the in the layers of rock okay and we're going to explore these uh ideas and these options and we're going to learn about these and using very basic uh geologic principles we're going to figure out what happened at heart mountain and believe me it is some story well here we are hiking up towards hart mountain i'm trying to imagine as i mentioned earlier you know as a geologist back in the day as he approached he's he's as he approaches the mountain he's thinking well this is looking more like the the older uh formations like the the bighorn dolomite or the madison limestone and he's starting to think i think my initial impressions are right that this is really old rock sitting on younger rock and so it gets more exciting as you get closer to confirm this because this makes this a very interesting geologic puzzle so as we're going on up the hill i wanted to point out something you see the terrain here in front of me is kind of bummiky hamake excuse me train is hummocky i feel bummicky but meaning it's bumpy and there's a word for that and you see how it's humpy all over small little hills so this hamake terrain comes from the weathering of shales and mudstones and this is what we'd expect from the weathering and erosion of the willwood formation now another thing i wanted to point out is we've come here where there's quite a bit more rain and so everything is covered in grass unlike the badlands that we were at at mccullough peaks in that region uh you know every there's not much vegetation or rain but the geologist that comes out here they look for evidence of what formation is underneath this hummocky grassy surface and lo and behold of course they'll find areas like we see here where i zoom in that in fact prove that it is the wilwood formation the classic red banded badland wilwood formation so with that information we established confidently that the the slide block of the heart mountain to heart mountain is sitting on top of this very young 50 million year old wilwood formation okay i'm kind of uh excited to be here with this tree level i've made it up here to where we're about 800 feet from the top at the tree level and the ecosystem has just changed dramatically because right now probably 150 yards away i'm listening to a couple cow elk whistling and calling to each other and it's a lot of fun well i've finally arrived to a place where i can definitively um definitively talk about these big cliffs so uh let's take a look at some of this rock and the cliff face and the characteristics of it and then we'll go on to the top i'm gonna turn the camera here and look at a little bit of rock so you can see what the geologists saw at the time and if i had time i would love to scramble over and get on it and i might see stuff higher up so we'll see so here's a big boulder as we look out into the basin i'll turn slowly sitting way above the basin way out there and swing around and watch yeah get the camera up a little higher big tall cliffs big tall cliffs of the madison and the bighorn dolomite so that's the story here for this uh little stop here on the trail and we got to get on up to the top and we've still got a ways to go but the amazing thing to me to think about standing right here where i am is that if we drilled a well we would drill through this old old rock up here then we'd drill into some wilwood like we saw below on the hike we drilled down down down and guess what would happen we would come right back into this very same rock underneath our feet 15 000 feet 15 000 feet down so that gives you some perspective so here we are higher up and yet again i see behind me just beautiful beautiful uh big horn dolomite madison limestone up higher what a beautiful hike in a beautiful trail spectacular much better than i thought this is the first time i've hiked this trail standing on this huge block of limestone that slid out in the basin and looking way out over the basin way above the basin floor is pretty darn awe-inspiring boy this is beautiful light as the sun's setting here and i'm looking way out to the west this turns out to be where all the slide blocks in this area came out from towards me so let's zoom in with the camera here and talk about a couple things right here where you see this beautiful area of uh grassland on this slope here that saddle there that pass is where several of these large blocks came out from came right out through that area now of course it looked a lot different then you have to remember there's been a lot of erosion this basin this low area in front of us was actually all a great plane it was very flat there was no erosion at the time in fact sedimentation it was filling in the basin was filling in with sediment and so when these big blocks came sliding out it was on a very very flat planar surface as it came out into the basin unlike we see today now you see this way in the distance this amazing peak it's called pilot peak and it turns out that the slide blocks came out from even beyond that clear up past that to yellowstone park this whole huge area that broke free which we'll be learning about you know as i drive along here towards a little community for our next stop clark wyoming i can't help but think of those geologists that that had to get on their horse and and use a wagon and ramble around you know it must have been quite a chore well here we are at an amazing place yet again an amazing place in the bighorn basin and in wyoming don't you just love wyoming i know i do it's just it's an amazing place to be and i come here uh i came here for a very particular reason and relating to heart mountain force to help us think about heart mountain and what could have happened and how the original geologist may have thought of the problem and likely did i'm a geologist after all and i know how i would approach it but off to my right in the distance you can see heart mountain and here is just an unbelievable fold of the mountains on the front of the beartooth mountains we call on the clarks fork river where it comes out of the mountains and it's as you can see here it's just mind-blowing how the layers of rock come from even out of your picture frame it goes on up i can't get it all in i can't get it all in without going way wide angle and then you can't see other key things but the whole the big layers of rock come and they just turn and they go vertical they turn vertical and go down under the ground way down under down into the basin and by the time they get just a few miles out to the east out here these layers of rocks are fifteen thousand feet under the ground okay it turns out that heart mountain the layers that we see in hart mountain are the upper part those cliff formers up there see those cliffs at the top that turn underneath those are the layers of rock that slid out into the basin out here way out here now it turned out it was back there a ways where it came through broke through through but now we know the layers the stratigraphy those are the layers that broke free those big cliff formers okay another reason um i brought you here is you think well gosh look how high these layers are they're way up this mountain face rises 4 000 feet above the river couldn't they have fallen out just like a big catastrophic plunge and and that's how heart mountain got there well that's a good thought and that's a reasonable thought but you can't find the piece that broke loose here this is all intact this is all intact rocks those layers you don't have evidence of it breaking free right here so you go so you you think it through and you hike along the geologists would and ride their horses and then and their wagons back in the day looking for evidence of how that big piece of rock on top those layers how a huge section of that got way out into the basin in fact there's parts of heart mountain out further at mccullough peaks where we were earlier there's actually pieces clear out there that slid out and even further so so it makes you think about this whole problem right okay so we don't now know the layers involved of rock and quickly here i've tried to establish that it's still even though you've got them way high they didn't plunge and fall off catastrophically in a steep fall off the front of the mountain that could be a viable theory so now what does that do tell us about heart mountain out in the distance off out here now we're starting to lean to okay i don't think it's a catastrophic plunge of rock we don't have evidence of the the thrust faulting so i wanted to jump in here and talk a little bit more about this idea of thrust faults i've mentioned that geologists decided they weren't thrust faults that this heart mountain and this big landslide wasn't the result of thrust faulting let me talk to you just a minute about that i have a sketch of a layer of rock this red layer here that has been folded the big fold and then there's it broke in this fault see this big heavy dark line that's a fault in this sketch and this blue arrow shows that the the top above this fault it broke this way that's what i have that arrow for so the rock basically got squeezed and squeezed and folded over and broke okay that very common in thrust fault terrains we call these features compressional features everything's being compressed and squeezed now it turns out when geologists hiked around all through the region of the hart mountain area what they saw were extensional features signs of things being pulled apart and that's common in landslides most of the features and landslides there are a few exceptions locally are extensional being pulled not compressed they didn't see rocks that had been folded all over the place and that and there are other things that you look at as well that but that's one of the main ones so in the end the important point is in the end all the information says no there was no thrust faulting involved in the great landslide so now where really left with what we call the low angle detachment where things break loose on a very low angle like two degrees literally a huge area now we're kind of thinking of that and we start looking for evidence of that right or we find evidence and then and then start putting it together and that's how these geologists did that here i am uh standing looking down behind me to heart mountain i'm up in the mountains heart mountain's about 14 miles away out down there you can see it in the far distance from man i'm standing on a ridge west of it high in up in the mountains along the chief joseph highway they call it spectacular country and it's here we're going to start examining and looking at things that the the geologists that studied this area uh that they studied and see evidence for what happened to heart mountain how did it how did it get out there where it is on top of these young rocks right that i've discussed so let me walk over here and we'll look out beyond us to where we're going to be exploring as the geologists did so if i turn the camera around and uh walk down here walk just to the ridge up here onto this ridge beautiful country here really spectacular this is the country where nearly all the evidence that geologists found that helped them understand uh about heart mountain this is where all the evidence comes from so this is the clark's fork river drainage on the right side of the screen and the distance is the beartooth uplift and then as i turn here and pan to the middle here it's way out in there where the core of this giant landslide occurred it's an area that's about 30 miles back behind me back here over 30 miles where it broke free in yellowstone park technically 30 miles by 20 miles massive piece of uh real estate of land broke free and uh so now it's getting exciting isn't it because we're gonna actually start looking and seeing what the geologists saw and start putting the pieces together and determining that that's how and that's what happened to heart mountain that's how it got out there so let's go and start examining and seeing what we see in evidence to help us out shall we sounds fun to me driving down off this big ridge i was on i'll just call it the big windy ridge because it normally is quite windy up there coming down into the valley where we're going to be looking for all this evidence of the detachment it's pretty exciting to think about what we might see [Music] well here i am at another really very interesting spot on the whole heart mountain story i like to think of where i am at as one of the key uh key points that a geologist hiked to back in the day and going aha when he saw this mountain and some of the relationships that he observed and that he mapped out this geologist he or she and i want to start by looking at the layers of rock we've covered this some before but i want to come back to this okay i am standing uh on what's called this this little blue line here is called the pilgrim limestone and this is a really key marker bed in this entire story because it helps kind of it it sets a framework to help us understand what's going on because it turns out the detachment is up above that just a ways right at the base of the big horn dolomite and we'll be looking that at that further so i am standing on the pilgrim limestone okay rocks are deposited in layers like this that are originally very flat okay but every now and then a geologist like here comes to a situation where he sees something pretty strange you have your nice uh layered rocks that are predictable we'll say and then all of a sudden you see layers of rocks maybe doing this as an example oh boy now there are a couple different ways to to get this scenario situation uh and they're pretty easy to sort out if you have the information at hand for geologists but let me talk about the one way that's important and it's important here and that's the detachment to get rock that's tilted or folded on top of flat lying rocks if you have a detachment surface meaning a surface let's call this surface here a detachment surface which is important to our story okay if you have a surface like that that means everything above it was sliding around on top of this surface it was jumbled and moving around well you can imagine large mountains of rock like we're talking about here sliding around those rocks get broken and bent and faulted and all that kind of mess so that is one way to explain this situation so i made this sketch because that's what's happening here and it must have been exciting as geologists came back to the west of hart mountain into the mountains and mapping in great detail they started noticing these types of things among others and they started to go hmm where does it how far does this detachment surface go what does it mean uh what's on top of that surface what is the actual surface like so uh and and so it must have been boy i can tell you there's nothing funner for a geologist than trying to figure out a puzzle a puzzle in the rocks okay so when i walk over here to this edge here and show you some drone footage footage of this particular spot i'm in i want to sketch a couple observations so to my left right just like i am now i'll be looking at the drone like this we'll have that pilgrim limestone as i just talked to on my stratigraphic column the rock layer it'll be dipping like this very predictable it's a really great marker it's a big thick limestone and i'll be i'll put a little tree here i'll be standing by this i don't know if there'll be a tree i'll be standing right here on this edge okay it's not flat it was deposited flat it's been rotated some but above it you're gonna see some interesting things and i won't tell you what you're saying until you see it and i'll talk to it on the drone video so let me step over to this and let's take a look at what we have okay so here i am standing on the pilgrim limestone as we back away here to reveal interesting things and as we back away whoa whoa wait a minute what what what is going on here we've got to stop this this is interesting yes yes look at these upper layers of rock here these big layers of rock that are dipping quite steeply they're dipping much more steeply than the gentle slope of the pilgrim limestone beneath it so this is a nice clue that boy there's something going on here and there must be some surface a detachment surface in this region so let's continue to fly up over the mountain to see more and we see in the distance here the big windy ridge and then this immediate next mountain we see similar things don't we we see steeply dipping beds in this area and then over to the right on the right side here which is to the south we see beds that are not so steeply dipping everything just looks kind of jumbled well it's time to move on and drive further to the west looking for more clues as to what happened here i love driving this road in this beautiful country even though it's a bit of a smoky day there's still many beautiful things to see [Music] well here we are at a really important place for geologists as they were mapping out this area this mountain face that we see back here behind us this very large mountain face goes from here clear back around that's like eight miles long okay and this turned out to be a really important area to see many interesting features that helped them to determine where the detachment is so we're going to acquire some drone video and i'll show you that video and we'll see what they were learning but it's sure a neat place okay i wanted to stop here and kind of set the stage with the layers of rock that we're looking at so at the bottom here we have the pilgrim limestone which we're familiar with now and then above that we have the section of dolomites and limestones like the bighorn dolomite and some mississippian madisoners and other units within that and then on top of that we have a big thick section of volcanic deposits that you see in this kind of darker color now i also want you to think about the processes here um these on top of these limestones here originally there was another oh at least eight or nine thousand feet i'd say of more sedimentary rocks that were there and then when the mountains were uplifted the erosion occurred and eroded it all down to the top of these where this line here in this particular mountain face this about this much limestone down to there and then the volcanics came in on top of that and deposited thousands of feet of volcanic deposits on top and then they were eroded too we have to remember these volcanic deposits have been [Music] eroded and continue to be eroded since for 30 plus million years they've been eroded so of course when these volcanoes were active it set up the stage to trigger this massive landslide that occurred 49 million years ago i'm seeing something interesting in this area are you let's take a closer look yeah we can see these sedimentary layers here that are starting to turn and bend down to the right side of this image here in our zoom in image and abruptly stop at a planar surface so everything underneath this is planar almost horizontal here and that contact where we can see where it meets that would be the surface of detachment so now for the first time we're starting to get close to understanding exactly where this detachment occurred where everything broke free hopefully this will remind you of the last sketch i did on the whiteboard showing some of these relationships if you'll remember so continuing on i want you to notice this nice distinctive layer here it's about 10 feet thick very interesting and that looks to be about where where this contact is where things change from dipping rock to planar or horizontal rock meaning that would be where the detachment is let's let's keep an eye on that okay wow look at this area here i'm seeing things here that are really getting interesting let's take a look yes can you see this darker vertical seam of molten rock that's been intruded in this is volcanic rock and look how it abruptly ends right at that contact we've been keeping our eye on this is very important let's expand on this some well i wanted to jump in here while we're watching this drone video and insert uh a sketch using my my whiteboard here to help us understand what we're seeing you know we're in the or see this but a vertical seam of dark volcanic rock that cups cuts up through the formations and then underneath it abruptly ends how could this be well i made a sketch here of a volcano and a magma chamber molten rock underneath and molten rock squeezing up through some right up to the volcano but others are walls that is in fractures that come all around the volcano kind of radiate out from the volcano so there's a seam here for instance in this little sketch okay now what happens what happens when we have a detachment and we take this whole thing and slide it so i'm going to draw an arrow here a big old arrow off to this side of the sketch which is to the east in this case slides out okay and where is the detachment well it's i'll make it in this for this sketch right on this green line right here okay right along there now i want you to think well what happens when we cut everything and slide everything along that detachment surface and that's the way geologists they thought backwards on this to to figure this out when they made these observations that we're saying what happens well let me show you the next sketch uh and slide it over okay okay so i've had a chance to re redraw this sketch a little with the mountain the volcano slid over like we said on the detachment so let's mark this detachment it's on this green line right here on the sketch right figuratively that means that all this rock from here all these layered rocks plus a bunch of volcanic on top all broke loose and slid this way and of course everything underneath is stationary and so that volcano and the associated dikes and stocks or plugs in here slid over this way from here so it used to connect up here pretty interesting huh so this helps us understand what actually happened when we see the outcrop here on this mountain front because what are we observing here in this drone video we're seeing uh volcanic dikes there's several along the mountain front but this really nice one here we're seeing one that comes from the top you see it above the detachment it comes down and it ends right here and you don't see under anything underneath the underneath part of it is clear out somewhere else we don't know where and also a geologist can find these relationships maybe somewhere else if you hike around a lot where you see a volcanic dike come up and abruptly end at the detachment because it was severed it was just severed right off and slid away so you can imagine when a geologist saw this these guys hiking around out here doing all the hiking and mapping when they see this it gets really exciting because wow it's pretty unusual to see this uh just something that's just cut right off like this and of course this was a very key piece of evidence to help them understand what was happening and to determine that actually it was a detachment a low angle detachment that covered a huge area hopefully with the help of this discussion uh this mountain face and what we see here is far more interesting to you so let's continue watching this actual detachment surface you're going to see some interesting things i think you'll see some hints of vertical volcanic dykes now they can be partially covered that's how nature works and other jumbled rock and things isn't this a beautiful view down this detachment line wow and we're looking right out down towards hart mountain so it slid right down the way we're looking and i want to kind of back out and go in that direction because there's an interesting change here i want you to see so we continue to move to the east along this mountain face towards hart mountain the way the mountains slid and we come around the corner and we see a different type of field don't we we see softly eroded mountains more softly eroded and the detachment's a little more difficult to see but it's right here and on top of it are softly eroded volcanics now not all volcanics is hardened or you know lava flows or hard and durable lahars but you have all other types of volcanic deposits and some of them are pretty easily eroded and they formed these gentle hills and so here we have all volcanic deposits on top of the detachment we don't have any sedimentary rocks at all it's all volcanic on top well i've gone up the road aways it's another day actually i've had to use several days to develop this video but it's a mother day and back oh right up that can up that valley way back there is where the great wall the mountain wall was that we filmed the drone video to see some of the things the geologists were looking and a lot of sedimentary rock on top of that detachment there as we learned but as you come this way if i turn the camera i'll turn with it there's some sedimentary rock in this area but from here as you go further west further west up the valley to the beautiful pilot peak and beyond clear up into yellowstone still another 15 miles or so most of that is volcanic rock that's on top of the detachment i'll be hiking up a canyon right up in the middle of that big black point that canyon's about right there and we'll actually hike right up to that detachment and take a look at it okay so here i am i'm gonna be hiking up uh a canyon near pilot peak we're going to be looking for the actual detachment detachment surface just to give you a feel here be hiking in my way up in there to this canyon this is kind of tough going it's a lot of fallen timber and it's been this way all the way so far so the things we do to show you geology i guess is i hike up here i can't help but think that the geologist mapped this whole region uncovering this mystery this came on later but geologists hiking every nook and cranny this is a pretty unremarkable little canyon up here what they call a creek which i don't think it has water flowing in it very often at all but it's uh on the face of a very rugged mountain and there you can get some good exposures and that's what geologists are all about is is trying to find just the right exposure of rock to tell the story so they can unravel the mystery and this is certainly one of the key places well i'm finally here to where i can see the prize it's been a heck of a scramble i went too far east got up high had to come back down very steep nasty slope through lots of dead fallen willows oh if i would have been further west it would have been so much easier but i didn't know that but uh i'm definitely excited what i see i won't talk about the geology yet let me give you a feel of what's up the canyon here nearby [Applause] well here we are to the place of glory and it has been quite a work quite a lot of work whoa and i'm on a steep hillside here and i'm uh as usual i'm running short of time i've got to start giving myself take an hour extra even i don't know i just never estimate right but here we are and this contact see this beautiful white it's dolomite underneath where my finger is here okay and above it is volcanic rock and this is the contact of the detachment this is where the detachment actually occurred and it is a uh it's just a hairline there and it detached in the same place over a huge area probably 30 by 20 mile area 30 miles by 20 miles something like that that this detached uh remember we talked about detachment earlier so just to refresh our memory here let me get my drawing board remember i talked about you know layers of rock and that's what occurred now i haven't drawn all the volcanic rocks thousands and thousands of feet 10 15 000 feet well maybe not fifteen thousand but easily ten thousand feet of volcanics at the top of a volcano these strata volcanoes that were on top but i'm not putting that here these are sedimentary rocks so it's easier to think conceptually and then add the volcanics in later i've got a little tree here for kind of it's not really scale i mean it'd actually be much much smaller but just a reference so these are the layers of rock uh going up okay nice layers almost flat about two degrees of slope and then wow then all hell broke loose explosive volcanoes probably multiple but at least one just rattled the dickens out of this whole area massive shaking and hot fluids and everything and came up uh these fluids came you know into these uh layered rocks these uh stratigraphic rocks and and it detached what do i mean by that well let's do this again let's put a fault here okay i'm going to take it from here i'm going to go down to here and then i'm going to cut across here like this all the way across and i'm gonna remove some of this because these big blocks started moving okay so they started moving like this just moving across and another one here i could draw another big block over here but detach so this is the um breakaway fault we call it here very steep and then it broke loose underneath and i'll put a little right on that line broke loose and the fascinating thing is where it broke loose it broke loose right here and this dolomite ver this white dolomite and it's really hard rock and why didn't it break uh loose in a weaker spot of rock in fact just underneath are these shales that it could have broken loose on which are very weak now let's look at uh some rock layers the same rock layers we've been seeing with the big horn dolomite at the base going on up to up higher into the section and look at this where the detachment occurred and this rock here that we're looking at wasn't involved in the landslide so we can see uh actually we can map it out and see exactly where this detachment occurred and it turns out it was right here on this contact isn't this amazing right in this huge thick dolomite at the very base of it only about 10 feet up into it when underneath as we see here are these very weak shales so we had to have some very special conditions for it to break free on that little hairline this bedding plane over such a huge area it's amazing to think about and very surprising to geologists i thought i would explain this more clearly the whole situation about the detachment and how it broke loose in a strange place so to speak so i've made this sketch okay let's start here these two heavy black lines here those are the limestones and dolomites the hard rock for the most part underneath i've got some green dash lines that represent the very weak shales that we've seen in the drone video right and then on top all this red are the volcanics the strata volcano type volcanism now let me give you a feel for the scale this volcano here is easily ten thousand feet tall huge strata volcanoes off the flanks pretty much everywhere in the area you would have probably at least three thousand feet of volcanic material on top of these pretty much horizontally they're only have like a two degree dip layered sedimentary rocks now notice this upper surface here is a bit wavy that's because before the volcanoes came there was lots of erosion eroded like now 9 000 feet or so through time of sediment down to this point here and then as i mentioned earlier the volcanics the volcanoes came into play now i want you to think about here we are with volcanoes we have earthquakes going off everywhere we have lots of fluids coming up through into these volcanic systems and the seismic activity from these volcanoes the seismic waves and vibrations must have been tremendous and we think that could have been a contributing factor as to how this happened because if you if you get strong enough vibrations and stuff you could basically rattle loose on a betting plane like in the big horn dolomite and just break it free just a little and once it slipped even just i don't know i'm not sure exactly the distance but very small a couple inches just break it loose a little now you've created a weak spot and phenomenal heat from friction that started to break down the carbonates into their components like co2 gas and things and they've done the work the geoscientists have done the work to show that this occurred so once you get all that frictional heat you break it loose just a little potentially from the seismic waves and vibrations and now now with the fluids from the volcanoes and everything now you can create what's called an overpressured situation where the rock is essentially sitting on fluid and that means it's essentially frictionless and now it can take off like a bullet you know we're talking 100 plus miles an hour they estimate it could easily have been 200 miles an hour on just a two degree slope amazing to think about isn't it so this pulls away right right here i'm going to make this bigger like this okay slid out now i'm gonna scribble in a bunch of volcanics on top of here way up here way higher than where i'm scribbling huge volcanic pile massive volcanic pile well this as this separates and detaches it's not just going to leave a whole air here is it no all this volcanic uh pile as we call it is going to collapse into there and so there are two types of situations you see on this detachment surface you see a this detachment surface sometimes has sedimentary rocks right on top of it where it slid and stopped and other times where it slid open here the volcanic pile collapsed on okay and that's what happened here let me see if i can turn my camera slow here and see that see up up up up up up oh man whole mountain and a lot of it is eroded there used to be a lot lot more huge geology huge geology the last point i want to make is something kind of artsy a lot of geologists are kind of artsy by nature i love to paint oil paint i do photography i really am appreciator of art and geology is art and the beauty that we see around us can often be created from catastrophe and as you learn about how this all formed and you think about these processes for me as a geologist and i hope for you it helps you just even appreciate it more and ponder our place in this time and how fortunate we are to live now when we don't have these volcanoes coming over and getting us but but isn't it amazing i've driven up the road oh five or six miles and the road was kind of in the trees quite a bit but i could see something kind of interesting so we stopped and sent the drone up and now we're looking back from where we've come from way out in the distance is the big mountain face that we like so much and right here in this area is the jim smith creek and now we've come up to here and i'll just turn and look up towards yellowstone park i'll turn this drone right around and this is what we see we see an amazing slide block here wow this contact here is really stark we've got the the lava rocks from volcanoes right we uh on top of a very sharp contact we're familiar with that now and in this area i get the impression there was a lot of heat involved in that it's altered the shales underneath this contact to make them look appear you know very light colored as well as the limestone but just an amazing contact and out in the distance another 10 plus miles or so is where finally we hit the breakaway in yellowstone park so let's proceed forward up into that country well i've come up here to the great breakaway fault up right it's actually right inside a yellowstone park at least this area and unfortunately you can't fly the drone up and it's very difficult to see this breakaway fault from the ground i thought about various ways to present you this information and decided to you just use a still photo here and draw it in it's hard to see i can promise you the geologists that have worked this to them as they hike it out and see it from various angles from up above etc that they're very confident and it's well established this breakaway but it's hard for us to see on the right side of the that red line which is the breakaway fault the trace of it on the surface on the right side of it are all the layers of rock that are essentially undisturbed you know volcanoes of course came in and put lava and and various volcanic deposits on top of it and now it's been eroded but other than that it was not part of the slide everything to the left which is to the east side that's where it all went all the way out clear out into the uh into the basin going on a long drive today gonna be introducing you to some areas outside the core of the whole heart mountain story you know we've seen the breakaway faults we've seen big blocks we've seen the the detachment and of course we focused on heart mountain but it turns out as i've mentioned there are many blocks and some of them were much bigger than heart mountain and some of them slid a lot further than heart mountain out into the basin so we're going to be going to up near cody to sheep mountain and also way out in the basin and we will learn more about this this whole mega landslide now this canyon right here is where the dam is just west of cody so i'm just west to cody and it holds back the buffalo bill reservoir okay and this is on the highway that goes up to yellowstone rattlesnake mountain continues there's a notch here where the river cuts through and it continues back back back back back to the north okay see it way back there and that's a fold that involves sedimentary rocks not volcanic rocks there could have been volcanics on top i'm sure there were that have eroded away over the years many years okay and then if i turn okay we're back to the canyon and if i turn the camera with me to look across the reservoir here that is sheep mountain now there are a lot of sheep mountains in wyoming it turns out but that's sheep mountain and that was a big block that slid out like hart mountain it's much bigger than hurt mountain and it's slid about the same distance and it has the volcanic or the excuse me the layers of sedimentary rocks in it and on the flanks and places you see some volcanic rock as well and uh you can notice that you'll see tilted rocks and bro you know like we've seen you know layers that have been tilted and faulted and and whatnot on sheep mountain like we've seen another block well now that i have my trusty white board out i'll add to this picture okay so what are we looking at here in my crude sketch let's start with cody right over here in the green okay this is heart mountain this little oval here is rattlesnake mountain and then up here one that's the other direction of fold so they're folds is a patahara mountain okay and we've been spending a lot of time in this area this is the beartooth uplift represents the beartooth uplift this represents the uh breakaway fault where the the head breakaway fault where it all turned loose uh most of the uh detachment was in an area of say kind of in this area up to this breakaway fault and down here so big area like that that breeze is getting me okay and now let's move down to where we're at now uh this is the uh buffalo bill reservoir buffalo bill reservoir and this is sheep mountain down here at the bottom in the red so we have heart mountain and sheep mountain two big blocks this is a beauty here within blue here right here the buffalo bill reservoir with the river flowing right it cuts right through the mountain here kind of an interesting story okay so the the blocks were sliding some of them out this way towards hart mountain and some out this way towards sheep mountain um west of cody and this as i mentioned is a big much bigger block than hart mountain it's about four miles by four miles or so so there were two relatively small blocks that slid way out into the bighorn basin and here i am on top of one of those two small blocks relatively small i should say looking out towards hart mountain and the beautiful bighorn basin but out in the light where i'm pointing if you can see it out here out in the light out there is hart mountain and the biggest highest lit up mountain back here is where we think this detached from the geologists that studied this it was part of the heart mountain detachment it slid some 60 miles easily to where it is right now we have i'm standing on vertically bedded so it's been rotated right as it slid out it tipped up on its side clear out here it's almost vertical the bedding on this volcanic rock and using dating and and looking at the composition of these rocks the the geologist that worked it determined that in fact it came from the heart mountain detachment area likely right right across sheep mountain the buffalo bill reservoir in that area right out to here crazy to think about isn't it well here i am on the windy ridge of indian dead indian hill as they call it here we've been here before but i want to repeat we've been way back in this back country 30 miles back to the yellowstone park border the space 20 miles out through here across here 30 miles back and this gigantic landslide that we've talked about came over my head just a couple hundred feet over my head at the time sliding out into the basin out in front of me here towards heart mountain and i wanted to come here and put it all together and and wrap it up shall we say so i've got a 3d diagram that i've made and we'll probably do some sketches on the whiteboard and just kind of review exactly what happened and and tidy it all up so let's do that well i'm down below the ridge i had to move is too windy up there so i'm down below the ridge that where the landslide went up and over in this direction to get out of the wind and talk to you guys about the final you know the final wrap-up about this heart mountain landslide i wanted to start with the stratigraphic column remembering that we're down in the old rock and the in the big horn dolomite right near the base is where this detachment occurred okay as you'll remember and there wasn't much younger rock that was involved it had all been eroded away and then volcanics had come in even after the erosion so that's pretty interesting in itself but if we cut if we look at this little sketch i have here again here's my famous little tree here's the breakaway the the red line is the detachment that everything broke free on and slid around on and this right here is the breakaway fault and technically right up in yellowstone park and these represent the blocks that were sliding around now some of them had bends in them you know folding and they were faulted up some of them had big dikes volcanic dikes intruded up in them and all kinds of amazing things and underneath are just the layered sedimentary rocks here in the that represented by these green lines again about a two degree slope this is heart mountain out here this is the big ridge the big ridge that went up now in fact it looks big on this sketch but if i drew it to scale it's just a little bump because the the blocks of mountains and these huge blocks that are five miles uh across or so easily sliding around and the big thicknesses it was like going over a little marble i mean it's it's really nothing ah so i show i've depicted some layers that are folded or tilted and etc okay and i've left the volcanics out of it on top for the moment now let me show you a perspective drawing to show the whole region from a bird's eye view of this surface this red detachment surface so here here we are okay the green is the detachment surface this green area for reference we have the great beartooth mountains on the northern boundary so north is more or less that way here south is more or less this way we have the great beartooth mountain uplift we have the big rattlesnake mountain that comes in up to cody and in the cody area extending towards uh here here's pat o'hara mountain these are two big mountains that are important in this story the big blocks sliding around heart mountain would be about right here okay and so we have this set up with these blocks some of them went out towards buffalo bill reservoir in that area and some of them went out towards hart mountain and these two mountains rattlesnake mountain and pat o'hara mountain were kind of like buttresses they were there so it wasn't this nice two degree slope of the of the str uh str layered rocks the stratigraphic rocks okay they were there and they kind of blocked it and and wouldn't allow of course these big mountains of blocks to to slide here it stopped them okay and diverted them so to speak and then we have all the volcanics the of the absorka volcanic field i've depicted here in reality they were here as well but to keep a nice clean picture i wanted to just show the blocks with the stratigraphic layers schematically and the detachment surface huge area remember this is 30 miles by 20 miles or so that it where it all broke free on so i wanted to show you the real world now after we've seen my perspective view and this is of course using google earth and we're looking to the southeast out across the bighorn basin in the distance and in the foreground of course on the right we have the yellowstone park area on the left the important and great beartooth mountains the beartooth uplift and of course we see the outline of the actual area of detachment and we have these two arrows pointing to these yellow splotches of color which are where the two major volcanoes were at the time in this particular area moving along here we start to see some more details uh first of all uh we see the big ridge here on the left that we're familiar with and these two arrows are pointing to the main direction that these blocks went some a little more to the right in this view and some a little more to the left we have pat o'hara mountain here and also rattlesnake mountain there next to cody and actually here is the town of cody right here shown here so now to the slide blocks it turns out geologists have mapped over a hundred of these blocks and we've only visited a few here are some of the key blocks that we have visited we have the sheep mountain slide block then right here this rather small one compared to sheep mountain is the famous heart mountain as we know beyond it just a bit here out it's like 15 miles actually is mccullough peaks and then way way out in the distance was that block that we visited the volcanic block way out in the middle of the basin that slid so very far if we go back to my cross-sectional drawing i'm going to use some green here i want to put in the volcanics on top of all this this absorka volcanic field that was involved uh 7 000 cubic miles of rock was extruded out of the earth there that's 15 times bigger than the big bulk uh yellowstone eruption and it's much older it's 50 million years old or so the volcanics the absorka volcanics where yellowstone's only about 600 the last big eruption about 600 000 years old so we had such a huge amount of volcanic material on top let me just schematically put that in boy that was schematic put a big old nice cone up here you know kind of like that of volcanic material all through here and this green okay huge area volcanics easily 5 000 feet of volcanics on top of these blocks or before the blocks even of course and then as it broke up as i had mentioned earlier the volcanics fell down so to speak collapsed into the the space here that was developed between blocks okay and if it happened to be an open area of course there's pretty immediate volcanics volcanoes going off to fill that in with lava flows etc okay so wow so hart mountain at one time had several thousand feet likely of volcanics from these big strata volcanoes slid out and then the erosion and stuff and and of course during the slide probably some of it fell off too and then all this eroded down we still have a lot of volcanics out here on top that have not been eroded even now so we've seen so many interesting things and we've kind of imagined ourselves as geologists out here making these observations and finding very interesting relationships haven't we we've seen faulted and tilted blocks we've seen volcanics on top of this red surface you know where it'd be between the blocks it's just all volcanics we've seen big dikes of volcanic material molten rock that's squeezed up into these rocks as part of the volcanic process we now know with studying of the minerals and and the chemical reactions that were occurring along here that these blocks were sliding out easily 100 miles an hour 200 miles an hour we excuse me we know that that uh the volcanoes uh their eruptions rattled things around and got it started away started off and then you can imagine the heat from the friction as these blocks were sliding on that surface and in fact that we think was very important it created tremendous amounts of heat and that uh created co2 gases and the fluids were superheated and it made this slope of two degrees become basically frictionless and that's how it all slid out with blocks sliding over to buffalo bill reservoir blocks sliding up over this big ridge down to hart mountain and beyond and now with all the erosion that has occurred later to give us this amazing landscape okay so i realized i hadn't explained a really important point and that is how did harp mountain get on top of the younger rock specifically let me get my stratigraphic column right here and we've been talking about very old rock sliding out on top of very young rock thousands of feet up here right how did that happen specifically well let me come back to this sketch of the breakaway fault here you're familiar with the block i've you know some blocks i've depicted this would be depicting heart mountain this slide block here here is the great windy ridge right here very important this blue layer i'm going to say represents the pilgrim limestone which we've talked about earlier it's underneath the detachment this red here is where it detached and slid along right okay so as these out in the area where the great detachment is is a two degree slope and a big broad relatively flat area that was uplifted this is the basement it was uplifted and eroded and then volcanoes came in okay so but out here is the basin so here is the the key point this limestone plunges deep deep into the basin deep into the basin out here okay and all the rock above didn't get eroded it stayed there and in fact there was sediment being deposited out into the bighorn basin and filling in the basin the basin was full flat level up to the level of hart mountain and higher later but for now it was full it wasn't eroded and rugged like it is today and so these slide blocks are sitting here on this old rock here and as it comes out this old rock goes way down and it slides out over the top on top of young rock all on a gentle slope out into a broad flat plain in the bighorn basin that's how it happened this is a nice view of the big ridge that we've talked about many times with heart mountain in the far distance i thought it'd be kind of fun just to show a simulation of blocks going up and over this big ridge earlier we explored a couple blocks that were very close to this ridge they were are basically at the base of the ridge these two giant blocks that that stop before going up and over it's amazing to think that there were many blocks that in fact did go up and over this ridge i want you to imagine what it would be like 49 and a half million years ago to be standing on one of these giant blocks going a hundred plus miles an hour up and over this ridge and out to heart mountain one last thing i want to comment on is just how incredible fortune i feel as being a geologist that now retiring back in the bighorn basin in northwest wyoming where i grew up and learned to be curious about geology and over the years i've learned so much about it and now i have the opportunity to share it with you here on with video and through modern technology and thank you so much for watching this and i hope you've learned a lot about the great mega landslide of heart mountain

Channel: Myron Cook

Views: 351,388

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Id: CYS3r3tk2GI

Length: 89min 49sec (5389 seconds)

Published: Fri Feb 04 2022