Devils Tower National Monument

Jesse Reimink: Welcome to planet geo the podcast where we talk about our amazing planet, how it works and why it matters to you.

Chris Bolhuis: That was the weakest clap

Jesse Reimink: I know I missed, I missed, I

Chris Bolhuis: There was no way you gotta spike out of that.

Jesse Reimink: bad.

Chris Bolhuis: so what kind of Jesse do I have tonight? Like what's what's

Jesse Reimink: You fun, Jesse,

Chris Bolhuis: Do I.

Jesse Reimink: yeah, this is

Chris Bolhuis: Okay. All right. That was not an enthusiastic clap in,

Jesse Reimink: no, that was you're right. That was not, that was, that was shockingly bad performance by me

Chris Bolhuis: it was, it really was.

Jesse Reimink: I really need to step it up for the rest of this

Chris Bolhuis: You do, let's go. How you doing Dr. Reimink? I'm

Jesse Reimink: Oh, I'm doing really well, Chris, how are you?

Chris Bolhuis: we I'm doing great. Um, I'm out for summer now, actually. Yeah. when this comes out, I'll probably be out west won.

Jesse Reimink: You will, you will be out on the trip that I fell in love with geology on while you were teaching me the basics of geology. I mean this trip, and, and this is in the theme of what we're doing here. We're gonna talk about Devil's Tower today. We talked about Badlands national park last week. And the reason is because you start drive from Michigan, you head out west to the Western United States. You stop in the Badlands. It's kind of the first real interesting geology. And then you hit devil's tower, which gets a little bit more serious because let's face it. There's igneous rocks there. And those are pretty exciting. so

Chris Bolhuis: right. But don't forget about the, black Hills too. So when you go to the Badlands, you spend a little bit of time there, but then go to the black Hills,

Jesse Reimink: that's right. Absolutely.

Chris Bolhuis: and go back and listen to our episode on that too.

Jesse Reimink: Because you're out on the trip right now and you're showing 26 high school soon to be seniors. You're teaching about geology. You might be, you know, carrying out a little bit too long for some of them

Chris Bolhuis: oh, oh,

Jesse Reimink: but, but you're providing great information. Nonetheless.

Chris Bolhuis: Okay. You have no right to say that, when you joined us out west, okay. You, I gave you a, a task. I said, all right, Jesse. Talk about what is a magma chamber. It's one of your favorite things to talk about.

Jesse Reimink: That was the

Chris Bolhuis: So we found this,

Jesse Reimink: things to talk

Chris Bolhuis: we , we found this gorgeous place in Yellowstone

Jesse Reimink: Let me interject there a minute, Chris. This was like three years ago. I don't even think I'd started at Penn state at

Chris Bolhuis: Oh, is that a long time

Jesse Reimink: No, no, no, but I was like, I had done my PhD. I had spent three years as a postdoc four years as a postdoc. So this was not like in high school. This was recently

Chris Bolhuis: Oh, yeah, yeah, That's what you're saying. Yeah, it was recent and we were all excited to spend a week with us actually. And we had a riot. However, though, I gave you a job. I said, Hey, put a lesson together on what is a magma chamber. So we found this great spot in the middle of the woods and Yellowstone national park. It was amazing. And you managed to put, to sleep 26 high school kids. Like that was impressive.

Jesse Reimink: They had a really nice nap, though. It was really comfy Moss that they were laying on some nice logs. They were leaned up against straight out, straight to sleep.

Chris Bolhuis: you have to remember your audience, Jesse? Okay.

Jesse Reimink: Th that's true. I did. I did have a comment though. One of your students, I had, I think I had like an REI backpack and I'd brought along like an REI, like hiking chair or something. And one of your students was like, um, Mr. Reimink, are you sponsored by REI or something? and I was

Chris Bolhuis: I remember that.

Jesse Reimink: And she's like, well, I, well, I don't know. You're kind of cool. And you have a lot of REI stuff.

Chris Bolhuis: You had the, you had your guide pants on, remember the

the

Jesse Reimink: Oh, that's, that's exactly right. Yeah. I was like, uh, so REI, if you're listening, you know, we're looking for sponsors here, so um,

Chris Bolhuis: that's right.

Jesse Reimink: now maybe

Chris Bolhuis: That's right.

Jesse Reimink: uh, anyway. Yeah. So you, so let's get back to it. Here you are on this trip right now. You are probably not at Devil's Tower, but you've been there recently or you're headed there soon. Lead us in Chris, like give us the, high level summary of this half an hour episode here on devil's tower.

Chris Bolhuis: Well, first of all, push pause right now. If you don't know what devil's tower looks like, then you should, you need to Google image this. If you've never been there, you've never seen it. Like look at this thing. It is, it is so amazing. , So do that first and then come back. But there are two broad types of rocks that are exposed at devil star. We're gonna talk about each of them. We're gonna talk about their relative ages and how we know that. Then we're gonna talk about the theories that go into, what we think about how this really weird structure came to be from a geoscience standpoint. It's not quite settled. , we know some things, everybody agrees on some things, but you know, it's not settled yet. So that's really, what we're gonna do today is, uh, just kind of go through those things, what we know, what we think we know, and, and what's open for debate yet.

Jesse Reimink: Yeah. So where do we start with this, Chris? I mean, in GE, we always start, you know, the oldest first, the bottom first. So what predated devil's tower itself.

Chris Bolhuis: Yeah, sure. There are two types of rocks exposed at devil's tower. There's sedimentary entry and there's igneous. And, there's just strikingly different from each other. The sedimentary rocks are actually gorgeous. I mean, they're beautiful. Beautifully colored oranges and reds and Browns, and some whites thrown in there too. And then you have this kind of gray, bland looking igneous rock. And I say that it's bland looking until you pick up a chunk of it and, hold it in hand specimens. Really, actually a it's an awesome rock. this is different though, from stuff that we've talked about before the oldest rocks. At devil's tower are actually the sedimentary rocks and that's different from, a lot of the other places that we've discussed. Usually those old basement rocks are igneous and the younger ones are sedimentary. So not the case. So how would we possibly determine that the sedimentary rocks are the oldest they're older than the tower itself? How would we do that? How, how do we know that?

Jesse Reimink: this is one of the most basic laws of geology. And, you know, I teach this in the intro level class that I teach at Penn state now. And you taught me this when I was a, a student taking the college level class that you taught in high school, but there's a lot of laws in geology or rules in geology. First principles that are really simple once you hear it, but until you hear it and think about , you wouldn't really think about, I mean, at least that's the way I kind of feel about 'em is they're they're dead obvious once they're pointed out to you. And this one is one of them. This is the law of crosscuting relationships. And what it is is if something crosscuts another thing, it is younger. And the way this works is picture, a sequence of sedimentary rock. Oldest on the bottom youngest on top, they're deposited horizontally in layers, and then you inject a magma through that. The magma will crosscut the layering. And that means that the magma is younger than the sediments around it. Cuz it cuts across the layers. So. The sedimentary layers. If you like found one of those sedimentary layers, Chris, like let's say there's a oxidized red rock sitting out red on top of a, a reduced green rock. You find that boundary between red and green and you trace it back. That boundary will end. It'll die out when it hits the igneous rock. And that means that the Igni rock cross cuts the sediments. Therefore the sediments are older.

Chris Bolhuis: That's right. And we've also, discovered what we call this intrusive breccia where the, the sedimentary rocks have been brecciated or, kind of busted up by this intrusion and we call it a breccia because breccia and geology means it's kind of angular, you know, there's no transport with it. So they're just kind of like this welded together. Busted up sedimentary rock. And that happened because of the intrusion. So like you said, that means that the sedimentary rocks are older than the Igni intrusion that, that did that. Um, and again, like we said, they're beautifully colored. . They're oxidized, reds and Browns and yellows , and there's some white in there too. They're beautifully color. They were laid down. This is a theme from the Badlands, the black Hills, we're in the same vicinity by shallow sea that existed during this time, which was the Triassic and the Jurassic. So this is not the same sea, the Western interior sea that deposited the pier shale that, we see in the, uh, Badlands, the Western interior sea is actually younger then this interior Seaway, but there were, lots of seas that came and went as time went on in this part of the country. You also get in within this and did you allude to it Jesse, a green sedimentary layer? Why would we get reds and greens? What does that mean?

Jesse Reimink: Well, it's basically reduced iron and oxidized iron and the reds are the oxidized iron think of rust. It's just iron. That is rusted. Iron is bonding with oxygen to make these iron oxide minerals that are often red, usually at hematite. And the green is iron in the reduced state, which tends to make green minerals. And so that's really the only difference there. So if you see this red, green layering, it's an oxidized versus a reduced environment, it's just the amount of available oxygen free in the system.

Chris Bolhuis: Yeah. Think back to your high school chemistry class and Redoc reactions and that's, that's kind of what we have going on in a practical

Jesse Reimink: yeah, it's quite simple to just think of it, leave it at that.

Chris Bolhuis: So the next thing that we have to talk about then are the igneous rocks. Okay. And the igneous rock is actually kind of a rare rock it's what's called a phonolite

Jesse Reimink: and let me interrupt you, Chris. Cuz the igneous rock is what devil's tower is. So , the tower is this igneous rock. That's what

Chris Bolhuis: That's right. Yeah. And, and it's, it's kind of a rare, like very niche kind of rock. It's called a phonolite porphyry to me, I don't know, Jesse, for me. I have introductory level students. Some of them have had very minimal earth science or geoscience education. I call it a phonolite porphyry, but I say, this is very similar to an andesite. In terms of chemical composition. It's in Other words, what I'm saying is it's intermediate. It's not felsic, it's not mafic the magma was kind of sticky that did this. Um, but alright. What? Jesse is a phonolite porphyry and feel free. Go ahead. Get doctory on us. Get professory. Let's go.

Jesse Reimink: Maybe let's focus on , the texture that you can see when you pick it up. First of all, which is the porhphyritic texture. So what is that, Chris? I mean, you, you said andesite porphyry is kind of similar, that porhyrite term is applied to a bunch of different rocks. What does that mean?

Chris Bolhuis: Yeah. So porphyritic means two distinct grain sizes in an igneous rock. And the rule with igneous rock. And there are exceptions, but general rule is the slower. It cooled the larger the crystals get. So if you have a rock, an igneous rock that has two distinct grain sizes, it means that it had two distinct rates of cooling. It had slow cooling, probably deep down, and then it moved up toward the surface. Sometimes it comes out onto the surface where it cools much faster. And so you're gonna get then, you know, big crystals that are gonna be entombed in this fine grain matrix. And that's what a poor tic texture means. Anything that's porphyritic two distinct grain sizes from at least two rates of cooling.

Jesse Reimink: Yes. And so that brings us to the phonolite part. And this is P H O N O L I T E , like a phonograph. What this tells us, this is a chemical designation. It means it has intermediate amounts of silica. So something like 60, 65% silica which is kind of normal for this type of FSIC or intermediate kind of composition rock, but it's has a screaming high concentration of what are called alkali metals. That's sodium and potassium. Really, really, really high amounts. And the interesting thing about this rock, and this is a rare kind of suite of rocks, but we call these rocks alkali rocks because they're rich in the alkali elements, sodium and potassium. What's interesting about these rocks is although they have a decent amount of silicons in them, they have such a high concentration of the alkali metals that felt bar cannot compensate for them. There's too much sodium potassium to fit into feldspar because there's not enough silica. And I don't have a great analogy for this. Chris, you might

Chris Bolhuis: Hold on. So what does it form then? If it, what do you mean? What, what do you get then

Jesse Reimink:

So it's basically me. What it means is there's no free quarts. There's no free silica around, so you don't get quarts ever in these rocks. You do get felspars bars, so you do get feldspar, but there's more sodium and potassium floating around. And so you get minerals that are called feldspathoids a really, you know, original name here.

Chris Bolhuis: I'm gonna interject Jesse you're. First of all, you're a funny guy. Um, you took a long time to get to really what makes a phono light. A phono light is there's no quarts. Okay. like, that's really it, which is really weird. Um, you know, you pick this up and you'd expect to see some quartz in it and you certainly do not. There's no courts in it. All right. Give us an analogy.

Jesse Reimink: You do get weird minerals, like, uh, you get leucite, you get analcime, you get a lot of weird minerals, which are these, what are called feldspathoids. And these are minerals that have less silica in them than Phelps bar. They do have silica, but they have less silica and they just accommodate more sodium in potassium and, you know, I always like to think of mineral making like recipes and you need the right amount of constituent parts to make a good, chocolate chip cookie. And so if you're after a good chocolate chip cookie, you wanna have a lot of chocolate chips in there, make it nice and gooey and Doy, but you're starting to make a chocolate chip cookie and oh shit. I don't only have half a bag of chocolate chips. Right? Think of the chocolate chips being the silica tetras. We've talked about this before, as silica with four oxygens around it. You use all your silica. You can cuz you don't have any leftover or you don't have that much. You dump all of it in and you end up with a chocolate chip cookie that, ah, it doesn't quite have enough chocolate chips in it. It's still kind of a chocolate chip cookie and you don't have any leftover. Right. You know, you always wanna grab a little handful and taste some chocolate chips just while you're making the cookie, but you don't have enough. So there's no free chocolate chips. It's the same thing in these rocks. There's no free silica to make quartz. And so you get a very different mineral logical sequence. at the later stages.

Chris Bolhuis: Good. Good job. Good job. That was a, that was a, was a good analogy. I get it. Now. I get it So

Jesse Reimink: And let me just wrap this up, I'll just wrap this up because they're weird rocks. So like, you know, they form in weirder environments and these rocks are typically thought to be formed by melting of the lithosphere beneath continents, so that mantle that exists beneath continents, it's usually thought to be formed by melting that material. And you get. alkali, rich basalt, and then that sort of differentiates up towards phonolite. So the alkali rich basalt will differentiate and then end up as a phonolite. And that's what we see in devil's tower is the phonolite.

Chris Bolhuis: That's right. And this is where geology gets in the weeds a little bit because you know, a phon light on like just physical appearance looks just like the rocks that you get from Mount St. Helen's Mount Rainier, the three sisters in Oregon crater lake, or the Andes mountains in south America. It's very similar looking to a porphyritic andesite.

Jesse Reimink: Yeah. These weird feldspathoid minerals are hard to identify, you know, you gotta have a pretty practiced eye and usually need to bring 'em back to the lab to actually distinguish them. They do have a greasy appearance. They're a little bit greasier than quartz, which is what I always kind. Think of if you come across this rock, it looks greasy. , even when you break a fresh surface.

Chris Bolhuis: Yep. They do. They, do they have this kind of like weird sheen to them? Yep. For sure. All right. So let's move on, Jesse. We spend a lot of time talking about what a phonolite porphyry is, but that's important. Okay. The, but here's the deal. Let's get into how the tower actually formed. And this is, this is shocking to me, but

Jesse Reimink: Yeah, exactly.

Chris Bolhuis: there's still debate on how this incredible. Igneous feature formed. I've lived through some cycles with this, when I was a kid, it was a volcanic neck. And then, you know, when I began teaching and taking students there, ah, no, it's not a volcanic neck now. It's like a shallow intrusive plug and now we've, gone to other ideas and nobody really knows what the hell is going on with this thing. I, So when I, when I think probably when I took you there, young Jesse. To devil's tower. We were walking around the base and they have these interpretive signs, you know, and they have the diagrams and they're in color. They're pretty well done. They look good, but they were showing this as a volcanic neck and so we looked at the sign and at the time everyone, the consensus was, this is not a volcanic neck, it's a shallow intrusive plug. And so there was a ranger, an interpreter ranger that was, had a group of people and he looked at us and he is like, Who's in charge here. And I'm like, well, I am.

Jesse Reimink: Begrudgingly, uh, I guess I am

Chris Bolhuis: he hikes up his belt, you know, he puffs out his chest and he is like, so volcanic, neck or shallow intrusive plug. I said shallow intrusive plug, we think. And, and he said, okay, good enough. Carry on. And he walked away but, but you're well, I wanted to say, hold on, but your signs are telling everybody else that it's not that it's something else, you know, I'm like, ah, it.

Jesse Reimink: I mean, Chris, it must be interesting to have been born before, Geology was invented in your case. Right. So let's get into the difference there a little bit, cuz at first pass it sounds kind of like what's the difference between a volcanic neck and a volcanic plug. Think of volcanoes, like a plumbing system. Think of the pipes in your basement that are feeding, your plumbing system in your house. , the neck would. Any pipe, that's leading up to a faucet. You go down your basement, you see this pipe that's like in the neck of a volcano, it's, you know, down in the roots, that's feeding the stuff up to the surface, right? Cause what's a volcanic plug. Like, can you kind of contrast that with a volcanic neck?

Chris Bolhuis: Sure. If you just imagine the plumbing network leading to the surface, uh, beneath a volcano, it's very intricate. You know, we think we know what it looks like, but you know, it's hard to see in model and so on, but as, as you take thick toothpaste, like magma, that's oozing up through this plumbing network and it gets close to the surface, you know, into the plumbing system leading to the volcano, but it cools and it just gets stuck and it cools and hardens their without becoming volcanic. Whereas a volcanic neck, it actually was volcanic at one time. That's the, that's the difference?

Jesse Reimink: then, you know, there's. Relatively recent paper, I suppose, in 2015 that they proposed that actually this is actually really in the shallow parts. It's actually really close to the surface, like half a kilometer from the surface. It's more like sort of an eruptive equivalent from the magma chamber, right? This is what's called a dire. And, uh, basically it sort of entails eruption and then stuff falling back into that crater a little bit, but also stuff oozing up from the surface and cooling. Near the surface, almost in contact with the atmosphere. And so that's another sort of option or thing that's proposed for, , the formation of devil's tower igneous rocks. yes.

Chris Bolhuis: So, it's just interesting that we don't have this nailed down yet because. It seems to me that there are far more complicated things in geoscience. , you know, where rather this big, you know, monolith sticking out of the ground like this. I'm so surprised that there's still debate on this. Anyway. So that's where there's disagreement. Exactly how the magma got in placed and exactly where it got in placed in terms of depth, you know, was it two kilometers deep or was it a 500 meters deep? That kind of thing. There's some debate on this, right. But where there's not debate really is that tower was covered with these sedimentary rocks. Then it was exposed by erosion and the river that's there right now is it's called the belle fourche river. Um, and that the FSH part of it is, is spelled F O U R C H E. So it, it's probably the most mispronounced word that , you know, people are reading the interpretive signs. It's really humorous to see this, but, um, Anyway, the Belle Fourche river, as it just meandered back and forth across its flood, plain just began to strip away these soft kind of weak and wimpy sedimentary rocks and, eroded that sediment downstream and just gradually from the top down, exposing the tower.

Jesse Reimink: Right. And that is what we call differential weathering erosion, where this basaltic igneous rock, which is a really solid rock. That is a hard piece of material, preferentially resists, weathering, and erosion, so that it now stands at a high elevation relative to the sediments, even though sediments used to be on top of it, the sediments are relatively easy to erode compared to the phonolite .

Chris Bolhuis: yeah. Right. And , for me, and I think for some of my students too, it's one of the coolest things , to sit there. And contemplate. Imagine it just being covered with sedimentary rocks, relatively flat line sedimentary rocks, and just. Gradually being stripped, down and exposing the tower from the top down. It's just kind of a cool thing to imagine, but it, it doesn't really take a real vivid imagination to see this, because if you stand on the south side of the tower and you look south. You can see the Belle Fourche river in the distance there. And you can see terraces where the Belle Fourche river has like got reinvigorated and cut down and left the old flood plane kind of high and dry. You can, it's this kind of like step, like look to the flood plane. It's very cool. Those are called stream terraces. And, and so you can see this kind of incremental. Incision of the river on the, on its own flood, plain. It's it's. It's awesome.

Jesse Reimink: So Chris, the other, you know, really obvious and very cool feature of devil's tower has to do with the jointing in it. And you have climbed. If I remember you've climbed devil's tower rock climbed. It is that right?

Chris Bolhuis: that's right. Yeah, we did. Um, Jenny and I did it. And then we came back. Well, our kids were there, but they didn't climb. And then we took our kids up, two years later, , when they were, uh, eight and 10, I think. Which such a long time ago. Now my kids are gone. I'm thinking, wait a minute. They were little when we did this. Okay. I have a feeling that you're gonna get very professory on us with this, but we do need to talk about columnar joints cuz you and I we're huge fans of columnar joints. We, we love them. Um, if We, ever have chances to collect columnar joining

Jesse Reimink: It's one of the more spectacular things you can see, and you can see this in many different parts of the world, the Columbia river Gorge. We have been to the Columbia river Gorge together. We've seen these unbelievable columnar joints and the basalts there. The famous giants Causeway is one where people, you can walk on top of the columnar joints. So it's these big hexagons, the rock has broken into hexagons and it's called the giants Causeway, cuz it looks like a giants Causeway, right? Um,

Chris Bolhuis: Which is interesting from the top of the tower. you can't see the columns. There's actually soil up there and it's, it's grassy and there's some cacti up there and so on. it's not like giants, Causeway, where you can literally walk, uh, like steps

Jesse Reimink: that's really interesting, but it must define the climbing here. You know, you must climb basically up these cracks in the, in

Chris Bolhuis: That's right. It's crack climbing. You're jamming. Absolutely. You, you shove your hand in the crack and you make a, make a, fist or try to find a handhold, something to catch, you know, and you just keep doing it

Jesse Reimink: Uh, horrible. Um, so these columnar joints, this is one of the really beautiful features in nature. I think that forms naturally, it's relatively simple to figure out what's going on here. It's the rock cooling and contracting. And when the rock contracts it's losing volume and it needs to compensate for that space. So it break into joints like the joints break the rocks kind of fall apart or, or break apart a little bit to make space because the rock is contracting and cooling. And the reason that it breaks into these hexagons is you gotta think of the joints where they touch. And this is just. Thermodynamically the most energetically efficient way for stuff to form is to have three pieces touching all with 120 degree angles. It's like dividing up a pizza. You just cut it into thirds. You have 360 degrees all the way around. So each one of those is 120 degrees. Each slice is 120 degrees. That's the most energetically efficient way to do it. And you can think through this really in a fairly simple. The less points of contact, the more efficient it is energetically. So you want as few points touching as possible. if you take a piece of paper and you wanna cut it up, you could cut it into a grid. You could cut horizontally and then cut vertically. You would have squares, then all touching each other. But where squares touch, there's four squares touching at one point that's less efficient than having. Now you could think, oh, we could make this two squares touching, probably if we wanted to, , which would mean you just have to draw parallel lines to each other and cut along parallel lines, but that's inefficient because you need to compensate for space in the other direction. And if you kind of find the happy medium between there it's three, and if you combine three together, you make hexagons. And so every hexagon is touching two other hexagons at the points and that's. The way it happens. It's it's everywhere in physics. This happens in a lot of different places. What's called a triple junction, having three points touching at once doctory. Chris was I was I really in the weeds.

Chris Bolhuis: I love you. I you're, you're hilarious. He just, you know, you make me laugh, but I, I don't wanna laugh in the microphone. So I'm just sitting there smiling. I'm thinking he is such a funny little guy over there, except you're not little, you're a giant. Um, but so basically to do this, it's the most E efficient way to crack. right.

Jesse Reimink: Yes, you know, the other interesting point here, Chris, which pertains to devil's tower. And actually we saw this in the Columbia river Gorge is that those cracks will form perpendicular to the cooling direction. So in devil's tower, the cracks are vertical, which means that was cold on top and hot on the bottom. And so that's why those cracks , are vertical there in Columbia river Gorge. We. columnar joints that had big curves to them and kind of swept down into the left. Right. And that forms

Chris Bolhuis: see this in devil's tower. at the bottom of the tower. Yeah. Yeah. They curve and they become almost horizontal.

Jesse Reimink: this tells us that the. temperature gradient changed orientation. And we saw us in the Columbia river Gorge with, you know, big sweeping columns that kind of curve to the left. And then another one that intersected them and curved to the right, the usual interpretation in the Columbia river Gorge is that lava flowed out. And then a river float over top of it, which created like a really cold spot, which changed how the contours of temperature gradients devil's tower. This is probably has to do with like a larger magma chamber down below that kind of made it hotter out to the sides than at the surface, potentially this sort of sweeping outwards pattern to it. So anyway, it's an interesting, you could kind of like look at how the thing cooled, like actually physically what parts were hot, what parts were cooled based on the shape of these,

Chris Bolhuis: Yeah. Right. The geometry of the columnar joints themselves it's a strong indicator that this was not a volcanic neck. Right. I mean that the cooling surface was top down. Good job, Jesse. You didn't get too, like, you know, you're yeah. Left. I'm not gonna say you stayed outta the weeds, but you, you did. All right. You did. All

Jesse Reimink: All right. Well, good. what Chris, like, I dunno, you, teach this amazing field class. You go there every summer, you have 26 new, you know, bright eyed, bushy tailed, high school students. What do you tell 'em? Like, what are the, what's the take home point when you're sitting there looking at devil's tower, the spectacular monument, like, I don't know. How, how do you convey. How interesting this place is. Give us the spiel. You know, that's what I'm looking for. I

Chris Bolhuis: Yeah, well, like, you don't have to. I don't, I don't think because it's when we're approaching it and they're, they got their noses down, they're probably reading something, whatever, you know, and they happen to look up and you can just feel the energy change on, the bus. You know, they look at it and they're like, oh my gosh, I've seen that before. I've he's had that in class. Like we've seen pictures of that and you know how it is right. When you see. Pictures in a book or pictures on a screen, and then you get to see it for the first time in real life. That's a emotional moment. You know what I mean?

Jesse Reimink: Especially when it's like what? 1200 feet tall. And it's shockingly big you way bigger than you thought it was gonna be.

Chris Bolhuis: That's right. And it's just, it just stands up and smacks in the face and says, here I am. So it's pretty cool. I, you know, like, I don't know. I had the same reaction. it's a such an easy cell, but you know what? Jesse that's geology geology is. Our planet is an easy sell.

Jesse Reimink: it's a good thing to tie of take in the time scale of geology too, because that volcano, that ancient volcano that formed this, this igneous rock, this phono light that's about 40 million years old. And that thing is still sitting there. Resistant to erosion. It, it gets eroded. You can see the boulders, you know, falling off these kilo joints are kind of like peeling off the thing, and there is erosion going on, but the volcanic part of it is still there and standing pretty tall above the sedimentary rocks. We can see crosscutting relationships. We can see differential weather in erosion. We can see really cool igneous rocks. We can see really cool structural features in igneous rocks that tell us how this ancient thing cooled 40 million years ago. Very, very cool.

Chris Bolhuis: one other thing that I think is so cool is kind of goes back to like, you know, the more, you know, the more you can think about and kind of the more enriched your life becomes, right? And when, as you're climbing up the talus slope of devil's tower and anybody can do that. You, there are certain places you can't go beyond without a climbing. You go up this and you'll see these like bright, white, like really different looking rock on these colo joints that have cascaded off the tower. And they're surrounded by this bright orange lichen and those things. That's that's lightning strike. Where the rock was hit. It is so cool. And, you just, you look at these things and you wonder, well, how many people have walked right on past this? And it never occurred to them that that's what happened, but it's kind of cool to look at a, this big, you know, hexagonal, co joint that's Flad off the tower and, you know, and you're like, wow, lightning hit right there at that spot. I

Jesse Reimink: Very, Very, cool. Very cool. Um, well, Chris, I think that's a wrap. What do you

Chris Bolhuis: I think so go to devil's tower. It's

Jesse Reimink: go to devil's tower. do it on the way, go to the black Hills, go to the Badlands. And you know, now you can think of Chris out there, lecturing talking about the devil's tower and how cool geology is

Chris Bolhuis: that.

Jesse Reimink: Well, we hope you return safely, Chris, and we can keep doing planet geo

Chris Bolhuis: me too.

Jesse Reimink: Well, that's a wrap. Follow us on all the social medias we're at planet geo cast. Send us an email planet geo cast, gmail.com. Visit our. www.planetgeocast.com. And

Chris Bolhuis: Yeah. And share the podcast with somebody that would might like geoscience or geology Or our planet. Yeah,

Jesse Reimink: loves to travel to cool places and see cool stuff. Absolutely.

Chris Bolhuis: know a little bit about it. That's

Jesse Reimink: man, that's a wrap. We'll

see you soon.