Rocks and Rules - Putting Things in Order

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

Okay. Freaking finally.

Chris Bolhuis: you doing? how you doing Dr. Jesse Rek? How are

Jesse Reimink: I'm great, Chris. I mean, now, now that we finally hit record here, 45 fricking minutes later, you've been down the rabbit hole. You've been messing around your microphone. We've been arguing about the title. It's all

Chris Bolhuis: Oh, my gosh, coming up with a title for this episode. Yeah, this was a, this was a chore. Everybody needs to know this. We came up with a whole page full of possibilities. three quarters of the page were Jesse's horrible ideas. Um,

Jesse Reimink: We rarely agree on a title. Let's put it that way. We

Chris Bolhuis: that is true.

Uh, Hey, you know what? The last two episodes though, we've actually had some agreement.

Jesse Reimink: it's true. It's true. We we're on the same page, Chris. We're operating on the same wavelength for a while here.

Chris Bolhuis: yeah, not quite, but

Jesse Reimink: Yeah, no, that's right. okay. As the title implies that we agreed upon the title that we both agreed upon. we're putting things in order today. And this is this, I don't know. This is, uh, how long do you

Chris Bolhuis: What a minute. You're not even gonna say the title, Jesse. It's called rocks and rules, putting things in order. That's our title.

Jesse Reimink: there we go. So how long do you spend lecturing in your class about stuff we're gonna cover today? Just outta C.

Chris Bolhuis: Not a long time, maybe 15 to 20 minutes with the things that we're gonna do today.

Jesse Reimink: So not even a full lecture.

Chris Bolhuis: no, I don't think so. Uh, what I would do is I would go through the things we're gonna do today. I don't know though, you know, that's hard to say because you know how I am, I get a little off topic because I try to make this as visual as I can. Yeah, I do. I make it as visual as I can. So I'm showing pictures of the principles that we're gonna talk about. And then when I show a picture of it's a place I've been, I probably took the picture. And so I've got things to say about that too, you know, so maybe a little bit.

Jesse Reimink: and that's kind of what we're gonna do today. These are the basic, you know, five slash six basic principles of. a part of geology, I would say like half of geology and these are, principles that I think on the surface are very simple. They actually are really simple ideas, really simple concepts. But for me, at least they're the kind of thing that. You don't come about them naturally. Like it's not natural to just think, oh, that makes sense. You, you don't come up with this on your own, but once it's pointed out to you, it's very obvious and it makes complete sense. Right? I mean, these, all these five or six principles are fairly straightforward, but it's hard to come up with on your own. I think.

Chris Bolhuis: Yeah, I think you're right. But once you get ahold of it and you think through these processes, then, then it becomes like putting together a puzzle almost. you're using these to like, just sequence things out. And that's what we're doing today. This is about sequencing rocks and events in their proper order using basic basic principles.

Jesse Reimink: that's exactly right. And we're gonna cover five principles here, superposition, horizontality, crosscutting relations, inclusions, and correlation slash continuity. And these five principles were derived back in the 18 hundreds, really early 18 hundreds. Well, before we had any of the modern chemical or chronological. Tools that we have today. Like my lab did not exist being able to date rocks did not really exist. So these principles are all based on simple observations in the relationships of rocks to one another. And most of them focus on sedimentary rocks in the sedimentary rock record.

Chris Bolhuis: when we do this kind of like sequencing, we're not concerned with putting a number on things as in this happened so long ago, we're just putting things in their proper order. This happened first, second, third, and so on to get us to the end of the page. This is the last event that took.

Jesse Reimink: Yeah. And this is what's called relative dating because we're just putting things in relative order. It's you know, I got in my car, I drove to the gas station. I got a flat tire in that order. It's not, oh, I got gas at noon on Wednesday, last week. So these are relatively simple rules, but they're really valuable, they're valuable to practicing geoscientists out in the field. They're also valuable to just know if you like going outside and you see rocks you're on a hike. It's valuable to know these things and be able to recognize 'em in the field because I find it adds it. You know, a decent amount of appreciation. When I go hiking with non geologists, they're always asking about the rocks. And invariably, we end up talking about one of these five principles at some point on even like a one mile hike through a little park in the city, they're everywhere. So it's important to know these things. So Chris super positioned, do you start there in class?

Chris Bolhuis: I do. I, I think it's a good place to start because it's probably the easiest of all these things we're gonna talk about today. It's called the principle of superposition or do you call it the law of superposition or is,

Jesse Reimink: I call them all principles, but I don't,

whatever.

Chris Bolhuis: Okay. So yeah, we're gonna start with the principle of superposition, which all this says is that in a vertical stack of sedimentary rocks, the oldest layer is on the bottom and the youngest one is on top and everything else follows in that proper sequence. It's kind of like, you know, taking loose leaf paper , and making a stack of the paper on the table. You take the first one off and you put it down on the table and then you keep putting papers on top, on top, on top. And then the last one that you put down is the one that's on the very top of the stack. That's the principle of superposition because sedimentary rocks are laid down this way.

Jesse Reimink: So, Chris. Principles. At least my experience with these principles is most easily represented in mostly the Southwest us or the Western United States where there's a load of sedimentary rocks everywhere. There's you could see this in Michigan too, but as we talked about in our listener question episode about Michigan basin, you know, there's not a lot of rocks exposed, but where are some good places that you. Have seen super position or it's like dead obvious, you know, this is relatively simple principle, but where's it obvious. Can we paint a picture?

Chris Bolhuis: Yeah. In one of our earlier episodes, we talked about the Badlands Badlands national park in South Dakota. It's a great place to see the principle of superposition because you can see these vertical layers are stacked right up on top of each other, and you have all these paleo salts, these ancient. Soil layers that are colored red. , and so it's very easy to discern, bottom layers from the top layers. , and , it just works. The oldest layers are on the bottom and the youngest layers are on top.

Jesse Reimink: that's, that's a very clear one. I mean, that was the place I first saw this principle, for the most part. And you can use this principle in a lot of different settings too. If you're digging down into the soil, around your house, or if you're in a stream valley and you see one of those cut banks from a stream, you know, where the stream is cutting into the edge, it's turning like to the left and the right side of the stream bank will be cut through. You could see different soil layers in there. The oldest is usually on the bottom there. The oldest is on the bottom and those get stacked up over time.

Chris Bolhuis: Yeah. And you said too, that, these principles largely apply to sedimentary rocks. This can apply to igneous rocks too. If you have lava flows, lava flow on top of flow on top of flow, like you get in the Columbia river, flood basalts or some of the lava flows in Hawaii works also superposition oldest on bottom youngest on top pretty.

Jesse Reimink: yeah, very basic. And you need to be a little bit careful with this at times, because there are certain tectonic. Regimes that can actually overturn a package of sedimentary R that can flip it upside down. You imagine a big fold. If you take that sheet of paper, that pile of paper you were talking about, you smash it together. The middle of the paper will go up. The stack of paper will kind of bend up and then it'll get a bit heavy and it'll kind of flop over on the side now. The bottom side of that, the rocks are upside down. That sequence of paper is upside down now, and we can see this. So actually when you're working in areas that have rocks that are really deformed and folded and faulted, you always need to be able to say which way's up because that will tell you which one is the oldest and you know, which way's up points in the younger direction. So determining that is important.

Chris Bolhuis: And sometimes faulting can do the same thing. Faulting can displace rocks and put younger rocks on top of older rocks. But you can't use this alone. You have to use other things in conjunction with superposition to put the whole area in order. So let's move on. Let's go to number two, Jesse, what do we got?

Jesse Reimink: Uh, this is the principle of horizontality or the principle of original horizontality. And this just states that sedimentary rocks were deposited horizontally. You don't deposit sediments. On their sides. basically is all it says, like sediments are laid down in a flat manner. So they're stacked up vertically and they're layered just like your paper sheet, you take your paper sheets and you're stacking them on a flat table. They're laid down flat. You're not stacking them on some ramp where the top sheets would slide off. Right? Sediments are laid down flat and the same goes for basalt flows as well. So, these things are originally flat and if you see them tilted. That tilting came later. And so I see this every week for the last year and a half, I've been driving back and forth between state college, Pennsylvania and Eastern Pennsylvania. And there's this road on highway 3 22 in, Pennsylvania. There's a exit called arch rock road, exit, and it's called arch rock road because there's a big road cut. It's like a hundred feet high road. And there are stacked sedimentary rocks in there. There, you can see little tiny like coal seams and Shas and limestones, very finely layered. And there's this huge arch in it. And so these sediments are bent in a big arch. You could actually see two folds in the road car. It's really pretty, really beautiful, but this original horizontality principle tells me those things were actually. The folding came afterwards. They were folded after they were deposited. Cuz they had to be deposited in flat layers.

Chris Bolhuis: So original horizontality. This principle is not about placing rocks in their proper order. you use superposition for that. This is about putting an event in its proper order. It was deposition first and then folding , and the folding or tilting is a tectonic event.

Jesse Reimink: We talked about this in the answer to our listener questions. Uh, a couple weeks ago, when we were talking about these rainbow Hills in Peru, talked about this beautiful banded sediment, uh, really brightly color banded sediment, but it's tilted and it's tilted so that the sediment layers dip down into the mountain side. That's not original. The sediment was deposited, it was turned into a rock and then it was tilted on edge like that. So it puts these tectonic events in order. So Chris, that brings us again. We always have to use these things together, cuz usually we will be able to leverage a couple of these laws or principles against one another or together. So this brings us to crosscutting relations, which, uh, to me is perhaps the most. Out there, at least in my, you know, functional field work days is like, this is the one I use probably the most.

Chris Bolhuis: Yeah, I agree. So crosscutting relations can mean a lot of things. It can mean if you have a sequence of rocks, a vertical sequence of rocks that has a fault cutting across it, the rocks had to be there first and then the fault cut across it. So crosscutting relations says that if there's an intrusion, Like an igneous intrusion, a fault that happened, the rocks had to be there first, then the intrusion or the faulting took place. So it's again, putting an event in its proper place in its proper order. So Jesse, where have you seen crosscutting relations? Where's the first time you saw it?

Jesse Reimink: Well, it's near and dear to my heart because you taught me crosscutting relations on this beach. I think it was like a beach if I'm remembering correctly up in the upper peninsula in Michigan. And I just, I don't know how long this exercise is supposed to be. Like how long is it typically for you?

Chris Bolhuis: It depends. It depends upon the engagement of the class. You know, I mean, you can spend an hour there. I think we probably spent three or four hours there cuz it's extremely complicated.

Jesse Reimink: far as I remember, it was like kind of a cold dreary rainy day. And it was kind of that slight drizzle overcast kind of cold. But man, was I interested in this outcr cuz it's basically this huge broad swath of mostly basaltic rocks. If I remember correctly or at least mafic rocks with some intermediate and felsic rocks. So you have this dark, like small peninsula that goes out into the lake superior. And then there's all these crosscutting veins going across veins slash dykes. They're, you know, maybe 10 centimeters wide at most, and then down to millimeters wide. And they're all different colors and they all crosscut each other. And so you basically say, okay, All right. Kids work out what came first, put these things in order. There's however many generations of veins and dykes going through here put 'em in order. And that was the exercise. And man is just like putting a puzzle together. Cuz obviously the dark rock is the one that is being cut. So it had to be there first. Like the background dark rock was there first and then you're going through and you're saying, okay, which one? There's a white vein here. A small white vein. And that cuts a bigger gray vein. The white vein has to be younger than the gray vein, but then the gray vein has to be younger than the black rock. That is the most of the outcr. And then you kind of have to work through this, cuz not every vein cuts, every other generation of vein. So you gotta like put 'em in relative order. Oh, it was a great puzzle. that that is just

Chris Bolhuis: it really is. Because you said it, I mean, you have to identify all of the different, like chemical compositions of the veins that are cutting across the black rock and then work out the, the sequence of what veins are older and which one is the last one and then put everything else in its place in between. So it's really complicated if you dig down like the way you did. You know, if you dig into it and, and really analyze, or what's this vein here, what's it made of what's this vein made of and so on. So it's really cool. Crosscutting relations, like you said, is really, really a valuable tool in the field.

Jesse Reimink: Yeah, it's extremely viable. And I use this all the time in field work. You know, it is the one we lean on the most because we're dealing with not necessarily sedimentary rocks. We're dealing with like very deformed ancient, 3 billion, 4 billion year old rocks that have seen a lot of alteration and deformation. Usually when I'm going out sampling, it's this really complicated. Outcr like you taught me, uh, with the principal on back when I was in high school, very complicated outcr and I'm interested in sampling the oldest one, I can't bring , a sample of every rock back. So I want the oldest one or the oldest couple. So you have to work through this process to decipher which one's older, which one has the potential to be the oldest rock in this given package of rocks.

Chris Bolhuis: that's a cool application. Real quick, continuing cross cutting relations, paradise valley, which, uh, earlier in the summer was just devastated by these floods that started in Yellowstone paradise valley runs From Gardner Montana up through Livingston Montana. , and there are just these gorgeous basaltic dykes that cut across sedimentary rocks. And it's like, it's a great example of a lot of geology, because most of the students haven't seen sedimentary rocks that are that folded before. I mean, these things are vertically. I mean they're straight up and down and they're cut across by a basaltic Dyke. So you have super position, original horizontality, crosscutting, all going on in a field of view that you can all see at the same time. Pretty cool stuff. and then also the grand Tetons we've, talked about the Tetons earlier in an episode, uh, we did the geology of the Tetons and that database Dyke that cuts across Mount Moran. And then. All kinds of other, you know, dye based dykes that are smaller, that cut across other peaks in the Tetons cross cutting relations. That database Dyke is younger than the peaks that it cuts across. So, yeah, it's just a, it's a fun one to, to apply. It's it's really cool. When you first see this one in the field, you remember that.

Jesse Reimink: that's a great point, Chris, you can see this. A variety of scales in the field, like a big Dyke cutting across an entire mountain in the Tetons. And then also these tiny little veins that we were mapping when I was in high school. In your exercise, you could see this cross country relations at a wide variety of scales. That same variety of scales think can be applied to principle number four, which is the principle of inclusions. And this much like crosscutting relations tells us of two events, which one came first and the principle inclusion states that. If a rock is included in another rock, it is older. And the way I always describe this. And Chris, you usually have better analogies than I do. So, you know, give a better one. If mine's not that good, the way I always describe it is used in baking. Like if you're gonna make a chocolate chip cookie, you had to have chocolate chips, the chocolate chips had to be made before the cookie. And that same thing kind of applies to rocks. Like if you have. Well, in my lab, we do a lot of dating of certain minerals called zircon. And we find some of these in sedimentary rocks, but the zircons are in the sediments and therefore the zircon were formed before the sediments. If that makes sense. So it's kind of the chocolate chips and the cookie there away.

Chris Bolhuis: now. I. I like the chocolate chip analogy. It works, the chocolate chips are the inclusions. So they have to be older than the cookie because you can't have the cookie. And then just, you know, smash in a bunch of chocolate chips doesn't work that way. Uh, that scenario would never work in geology. So we see this a lot with igneous rocks, these intrusions. Okay, that break off some of the rock that they're intruding, the magma doesn't have enough heat to melt the rock that it broke off. So it just becomes included in it. So then that different rock is the inclusion it's older than the magma that caused the whole thing in the first place.

Jesse Reimink: This one, I think students find a little bit more complicated to interpret at times because you know, it's not as obvious. Like I've seen this in the field school I used to teach when I was a PhD student at university of Alberta, we go out to British Columbia. This is beautiful. Granite. Beautiful white granite. It's a, formed by melting of sediments. So it's this lower temperature granite, and it has these big pieces of black amphibolite in it. What we call rafts of amphibolite in it. And it does not look obvious. What's going on cuz this amphibolite like layered in there and the granite's not layered. So I found students, you know, usually can kind of get a little bit confused there when you actually look at the rock, cuz the structures can be misleading. You see this layered thing inside of this other rock, it could get a little bit. Sort of confusing in that way, but you have to sort of step back, look at it and be like, okay, what is included in? What, which one surrounds the other one? The one that surrounds the other one is almost always younger. And so the granite is younger. The amphibolite was older and was around before the granite formed. I always just found this kind of got confusing. , do you find this as well, chris or, or not really?

Chris Bolhuis: I, do. I do. So here's an example that we come across in the field, that you can predict. Okay. Hey, we're gonna see the law of inclusions here and it's in glacier national park. there's a great rock that I absolutely love. It's called a mud chip. BCHA. The chips of mud are bright red and they're embedded in what is now a quartzite, but it used to be just a quartz. So sandstone. And so the bright red chips of mud, those are the inclusions they're older than the sandstone, which is now quartzite. Right? , and so you can see that great. And the way this happens is when mud dries out. It cracks and it kind of peels up like potato chips, it curls up like potato chips. Well then imagine a storm comes ripping down, out of the mountains, across these chips that have curled up, they rip 'em up and then it comes to rest. When the water slows down it lays down this quart sandstone. It has these bright red chips of mud in. And so those are the inclusions. Those are older than the rock that they're included in. So it's just a great example, but you're right. This one can be harder for students to, like recognize right off the bat.

Jesse Reimink: And, you know, this is, you could see this everywhere. We we've been talking about going out in the mountain stuff. You could see this in city buildings a lot. You go walk into the city, wherever you're living, and you go past the building stones, a lot of the granite, or even the sandstone that is used to make the building, a lot of those will have inclusions in them. And so you can kind of work through this inclusion and crosscutting relations, , principles just by looking at buildings in a city. It's it's kind of fun.

Chris Bolhuis: Or go out and look at concrete. Go look at pavement. Okay. And the pavement has gravel in it. the gravel are, those are pieces of rock. Right. And they're included in the concrete and they're older than the concrete themselves. So yeah.

Jesse Reimink: Absolutely. So Chris, that brings us to number five correlation or continuity. Um, this, again, for me, best represented in the Western us, but it's, relatively simple, like a sequence of rocks. If a sequence of rocks forms in one side of a valley. You could correlate that across to the other side of the valley. Think of the grand canyon. I mean, the rocks on one side have a certain sequence, the rocks on the other have the same sequence. , there used to be rocks in between, I guess that's kind of the way, they didn't form with this valley. They used to be rocks in between. They used to be one continuous, correlated unit.

Chris Bolhuis: most sedimentary rocks are laid down laterally continuous. In other words, think of it as this really broad blanket that's distributed across a relatively flat area. That's lateral continuity. So what happens often in geology is you get this deposition spread out over the same rock layer, spread out over a massive lateral area. Right? Well then later on rivers come through and mess it all up. So they dissect it. Okay. And like what you said, you can stand at the grand canyon with a Colorado river that dissected that whole place. And you can stand on a very prominent layer of limestone and look way across the valley and see that same layer of limestone. And that's the principle of lateral continuity. It has the same sequence of rocks above it, the same sequence of rocks below it. And so using that, you can start to put things in their proper order because you know, Oftentimes in geology, we can't see the other side of it. So it's, Hey, get in a car, go to this. Outcr chart it all out on a piece of paper, get in your car and drive 15 miles down the road. And there's another outcr and you do the same thing and you're now putting things in their proper sequence in that way. And that's stratographic correlation. That's what we're talking

Jesse Reimink: Yeah. And this is used again at a variety of scales. We've talked about, the canyon or driving 15 miles away and you see the same rock unit. Okay. , they used to be a continuous sequence. you can extend that out to. Regional and actually global correlation. So for instance, the Southwest of the us is a great example of this, the grand canyon units of rocks. You can correlate similar ones all the way over to Las Vegas and into California. The same. General sequence of rocks that was deposited. Now they're offset from one another, some are missing in some places, but if you're careful and do very careful work, you can correlate the general timing all the way across an entire region. And then when we start to leverage things like index fossils, which we're gonna talk about here in a minute, we can start to do this across the world. We can link rocks in China. With rocks in the us with rocks in Africa, we could link them all up and determine when they formed relative to one earth using this really valuable thing called index fossils. And Chris, what could we go into that a briefly here?

Chris Bolhuis: we can, but first I wanna say that was impressive. My Youngs. Wow. Well, well put that was, that was extremely well put, nice job. Yeah. Um, okay. Index fossils so important. So. E everybody knows what an index is, right?

Jesse Reimink: Well, I don't know this generation, the Google, you

Chris Bolhuis: know,

Jesse Reimink: generation. Maybe not, maybe not.

Chris Bolhuis: That's true. All right. Well, alright.

Most books, especially textbooks at the end of the book, you know, the last few pages has an index where you can look up keywords and it'll tell you what page to go to. And you can read about those. So an index is something that we use to look something up, right? So an index fossil is the same thing. It's an index to look up the certain ages of rocks. And here's what we're talking about. There are certain fossils that have existed over geologic time that were really, really widespread. In other words, they lived in all corners of the world. Right? Most of the time we're talking about oceans. , so they were very prolific, but they lived during a very specific time period.

Jesse Reimink: Narrow a very narrow time period, right? Like a, a

Chris Bolhuis: Yes, those are the best ones, if it's a very narrow time period. So if a rock has that fossil, then we know this rock existed during this bracket of time. and so that's what index fossils are. They're very, very common and they lived during a short period of. So it tells us specifically then, Hey, this rock is this age so we can correlate it. Then back to what you said. Iraq in China is the same age as a Iraq in the United States because they have the same index fossils in them.

Jesse Reimink: That's exactly right. Chris, any global event you can correlate across the globe, right? And certain species of fossils or certain species of organisms will, live for a million years. They lived from 251 to 250 million years ago. And they were all over. They were in every ocean around the world. And so they're deposited those fossils are found in sediments around the world at that time. And so if we go and we find a rock in Michigan, or if we find a rock in, you know, Nevada, if we find a rock in China and it has that fossil and it'll say, ah, okay, this was alive. Between 251 and 250 million years ago, it must have formed. Then this sediment is now that old, we have a pin in time for that Rock's age. And then we can link that using this correlation to regional rocks around that particular discovery place. So these index fossils are really valuable and the index fossils are usually a specific species of organism you know, there are classes that will go through a little bit. I think Chris, there's a couple classes that are important here too.

Chris Bolhuis: should we just go through like a couple example?

um, so a couple really good examples of, index fossils are Ammonites and trilobytes. And I, I, we were talking about this before, like, don't you think most people have heard of these before? And he said, ah, I don't know. Maybe trilobytes trilobytes are, are They were very, very, very common and a lot of people have trial bytes and a lot of people have seen them, but. Let's describe 'em a second Ammonites. These are the spiral shaped fossil shells. on the side, they look like, , tightly coiled, Rams horns, like a big horn sheep. Okay. these were indexed fossils for the Mesa Zoic. In other words, they were common from 245 million years ago to 65 million years ago. And they met an abrupt. extinction at that point. And that was related to the KT boundary extinction, the meteor that wiped out the dinosaurs and too, it also wiped out, , the vast majority of Marine life too, which is what Ammonites, lived in. Um, the other one is trial bytes. Jesse, what did trilobytes look like To

Jesse Reimink: Oh, we were, I mean, they are, I they're like, oh, I don't know. They're like strange, you know, ocean they're like sea millipedes with antlers, I, or something gross like that. , know, they're, they're like very strange looking. ah, they're, they're

kind of gross looking. I would, I would not wanna see one alive.

People say they look like horseshoe, crabs, Maybe people have seen these, uh, horseshoe crab kind of things. They look sorta like that a little bit. but they're sort of strange things, but they're around from about 540 million years ago to about 245 and much like Ammonites. They're really valuable as index fossils because there are very specific species that formed at given times. It only existed during given times. So they're kind of this evolutionary branch. Bunch of different species and they kind of \ one species would come out and then it would proliferate around the world and then it would die off in another species would take over.

Chris Bolhuis: And these organisms were primarily like filter feeders. They would just feed on the bottom of a shallow sea floor and just filter through the sediment and they would leave tracks and things like that. And then they would live and die and get buried quickly. So because of all that, they're very, very common. I, I have some trial bytes that I break out in class cuz I'm a fan of 'em. They they're a little horrifying to me, but I also think they're really cool looking too. So.

Jesse Reimink: Yeah, I actually don't have any trail lights I need to, I don't have that many

Chris Bolhuis: Wow.

Jesse Reimink: I was, you know, uh, I wasn't super turned on by fossils, but, uh, they

Chris Bolhuis: yeah,

yeah,

So Jesse, go ahead. Finish. Let's wrap this up.

Jesse Reimink: Okay. So we covered the five really important, but very simple. If they're already pointed out to you, very simple principles in geology. First superposition, bottom sediments are oldest or bottom lava. Folds are oldest. Top are the youngest two horizontality. The sediments were originally deposited horizontally. If they're tilted or if they're folded, that happened afterwards. Principle of crosscutting relationships where the younger event, crosscuts the older stuff. , the stuff that is cut is older. The fourth one principles of inclusions, the stuff that is included is older than the younger thing that does the inclusion. Think about a chocolate chip cookie chocolate chips are older than the cookie itself. And then the last one correlation and continuity in, in there, we talked about index fossils and with those five tools, you can go. Into the world, either look at buildings in your city, go out on a hike, look at some rocks anywhere you find stuff sediments in a riverbank, you can do geology. You could do the basics of geology. If you think about it and just ponder it a little bit. So I find this very fun exercise. Like I said, go hiking with people who are not geologists. It's fun to kind of give them that basic idea. Like we did most recently a, a hike with a couple friends TES, and I went with a couple friends in the grand canyon and, you know, on the way down for about a half an hour point out these very simple principles and then the rest of like the four hour hike, they're having fun testing it, experimenting with these new tools they have. They're like, oh wait, I see crosscutting relationships. Okay. This one's older. Right. Jesse. You're like, Well done. It's amazing. So it doesn't take a lot to build these tools and they're very, very valuable. I think.

Chris Bolhuis: And I think for the most part too, students like working through these exercises, whether you're out in the field or whether you're doing it in a lab with a cross section drawn on a piece of paper and they're using the fault, the inclusions, the horizontality to put things all in order too. So it's you're right. It's just good practice. It's good thought process. It's like it's logical is what this is. This is logic. This is the way geologists think.

Jesse Reimink: If you like puzzles or you like crosswords, you'll like doing this. I guarantee it. They're very fun. So, all right, Chris, with that, that's a wrap follow on social media. We are at planet geo cast, Twitter, Instagram, Facebook. Those are the main ones. send us an email planetgeocast@gmail.com and that like subscribe button and a review. That would be great. If you could stop and do that right now for us, we would love it.

Chris Bolhuis: That's right. And we just want you to share the podcast with somebody that you think might love to learn about the earth.

Jesse Reimink: that's right. Take care.

Chris Bolhuis: Cheers.