The Science of Elevation - Hypsometry
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[00:00:00]
Good old mom coming through again.
Dr. Jesse Reimink: It was a good day when we get an email from Joyce, Chris. Have you read the email from Joyce?
Chris Bolhuis: no. She said one one's on the way. She like, I
Dr. Jesse Reimink: she did. Okay.
Chris Bolhuis: texted me and said, Hey Chris, I've, I've got, um, A question for [00:00:30] Jesse or something like that. Right. Is that, is that what it is? A
Dr. Jesse Reimink: don't know if it's not really a question. It's A comment. It's Joyce's word of the day, which is a theme I would love to continue on with. Cause what was one, we had one word of the day, which was feldspar. Was it feldspar or something like that? Or anorthosite? She had some word that she really enjoyed.
That was a mineral from way, I mean, years ago that you don't remember this.
Chris Bolhuis: Now I don't remember, but she is, she does make a lot of comments about words that we use and she's, she's enthralled by this new vocabulary.
Like [00:01:00] she,
Dr. Jesse Reimink: good, good. We're introducing you to a whole new world of geology vocabulary. This one's not. So Joyce's word of the day is bedraggled.
Chris Bolhuis: bedraggled. How does that fit into, was it like a recent episode that we
Dr. Jesse Reimink: Yeah, yeah, so she says bedraggled is an adjective, and it's of a person or person's appearance. Messy, dirty, and often wet. Jesse's description of Chris being under the weather. I think when You, were sick a while back, I called you I said we had [00:01:30] bedraggled Chris, and
Chris Bolhuis: wait a minute, you actually used the word
Dr. Jesse Reimink: I used, I said, we have a bedraggled
Chris with us, or something along those lines, and messy, dirty, and often wet.
That just fits you. It fit you perfectly,
Chris Bolhuis: was mom Bolhuis offended that you referred to her, youngest as bedraggled.
Dr. Jesse Reimink: No, no, she ends with, I just love that. So,
I,
think it's a compliment.
Chris Bolhuis: I, have to have words with my mom. Apparently, don't know. I'll find out. I'll find out. I'm going to see [00:02:00] her later today. I think so.
Dr. Jesse Reimink: Okay. ask her if it's a compliment.
I like this. Joyce's word of the day. and tell her we need more, words of the day. Send in her word of the day emails more frequently, because they're always a delight.
Chris Bolhuis: Okay. Well, I'm really trying to think of that word that we used that she was so impressed by.
Dr. Jesse Reimink: my memory's terrible, but,
Chris Bolhuis: it was not a geologic word. It was just a,
Dr. Jesse Reimink: No, I think it was a geological word. I think it was, uh, I think we were talking about anorthite or, I'm not sure, plagioclase or something. Some, some feldspar composition. I could be way off,
Chris Bolhuis: I don't know. [00:02:30] I can't keep up with my mom's, wonderings about what we talk about. I, I, they get, they get shoved to the way back of my head sometimes.
Dr. Jesse Reimink: course. Of course. Of course. Well, have they had any good comments when you go over there on Fridays recently about the pod?
Chris Bolhuis: I just have to wake her up.
Dr. Jesse Reimink: Oh, okay.
Chris Bolhuis: Like, or, or I'll just start, talking about what we're talking about and I'll wake her up that way and kind of bring her
back into the world of reality. So, yeah,
Dr. Jesse Reimink: good. That's good. Hey, we got one regular listener. It's Joyce. Love [00:03:00] it. So
good. Well, Chris, today we're talking about a big fancy word that's actually really basic. I'm curious just your thoughts on this. Is the word hypsometry needed?
Do you think?
Chris Bolhuis: Um, so know. Short answers. No, uh, hypsometry or hypsometric curve. I, I did not know. I had to look this up, actually the root. What does hypso mean? And
I didn't know.
Dr. Jesse Reimink: I didn't know the root either.
Chris Bolhuis: So, think [00:03:30] about that, our listeners, please, just for a quick second. What does hypso mean?
Dr. Jesse Reimink: Yeah. If you could take a guess, because this is a really fundamental, this is something you learn in every intro level class. not this curve, but you learn the underlying principle and then the fancy scientists over here, we have to add some complex word to it and, and add metrics, so we're measuring something, but a hypso is a loft.
Or high or height or something to that effect. So it's, it's height, it's aloft, it's high. so it's a [00:04:00] completely unnecessary term, right, Chris? Do
You
Chris Bolhuis: You guys doctored this up real good.
Dr. Jesse Reimink: we did, we made it, we have to make it inscrutable to the average person who doesn't know all these words. I mean, it's ridiculous. So hypsometry, but this is a really, really, I love this concept, Basically, it's the crustal distributions. It's think about Earth. Let's take all the oceans away.
And if we had a map, we don't actually need a map. All we need is a elevation distribution. So like, how much area, how much [00:04:30] percent of Earth's surface is between zero and one Above sea level. How much of Earth's surface is between 0 and 1 kilometers beneath Earth's sea level, etc, etc, for all the elevations.
How much of the Earth's surface is more than 6 kilometers above sea level, or more than 5 kilometers, like, it's a distribution.
Chris Bolhuis: that's right. and it's expressed as a percentage really of like, all right, here's the earth, here's the surface of the earth. What percent of it is just above sea level, just below sea level, really, really far below sea level, [00:05:00] and then really, really high above sea level. So as you said earlier, you would come across this in any intro level.
Geology course or Geoscience course, we think of it as a passive continental margin this would be the trailing edge of a continent, basically, where you have this continental shelf, just really, really flat area, just above sea level and just, a little bit below sea level. And then you get this continental slope where it dives down toward the deep ocean basin, where you have this [00:05:30] transition, the continental rise.
And then finally the abyssal plane. So every geology course is going to show this very idealized profile of the earth. And then this hypsometric curve just adds in the high, high elevations and the really low elevations, like the deep sea trenches. So it's
a little bit different take on a basic concept.
Dr. Jesse Reimink: you nailed it here. the curve itself. So this is a curve that is, database, but It looks exactly like a profile of, [00:06:00] a continent, a continent transitioning to an ocean. let's build this a minute because it. And, and let me back out of this.
Why are we talking about this? To me, this is an entire lecture that I give in my intro level class. And Chris, I'd be curious to know how you, how you aggregate these concepts or how you talk about these concepts. But I spend an entire lecture on this because it's really, really cool to me that you can look at just the distribution of elevations on earth and we can infer.
As geologists and people have done this back in the day, you can infer a [00:06:30] ton about our planet just from that. Some really, really important first principles. So the kind of thought exercise here is what happens if we fly our spaceship into another solar system and we look at planets and all we have is like LIDAR or, all we can actually measure is the surface temperature.
The topography of the planet. What can we tell about that planet from just topography? that's kind of the thought exercise. We're turning that on Earth. What can we tell about Earth from just the topography of Earth? And there's actually some really amazing stuff that we can [00:07:00] tell, I think. So that's why I spend entire lecture on this. Chris, how do you, How do you get these concepts across? I'm guessing you don't talk about the hypsometric curve because it's like useless for high school students to know that word.
Chris Bolhuis: know, I talk a lot about the profile of the earth and like the continental margins and then leading into the deep ocean. It's just classic. it's an important process. It's important. thing to learn. So hold on a second. you actually do a whole lecture. Do you use the term hips, hypsometry or
hypsometric?
Dr. Jesse Reimink: I, I Do and although it's, uh, This is, my
third [00:07:30] year doing it, I think.
It was one of these things, I was, reading some papers, and I was working on this, I started working on, you know, The idea of when continents emerged above sea level, which this hypsometry is, kind of, you know, really deep involved in that.
So I started like reading papers about this curve and it's a really basic concept, but it's used a lot. And so then I was like, Oh, I could probably use this as a way to explain a bunch of features of earth. And, and actually was used in early plate tectonic theory to derive plate tectonics. So I don't know if [00:08:00] it lands totally well or not, but
Chris Bolhuis: because I'm actually going to use this now because I'm looking at the hypsometric curve for earth right now. And basically, you you already described it, but it shows the elevation. Whether it's above sea level at sea level or below sea level, it shows the elevation on the Y axis and it shows the percentage of earth that is represented by that on the X axis.
And so
you get this kind of longitudinal profile.
Dr. Jesse Reimink: let's build this a minute because I think it's really important [00:08:30] just to visualize so the listener can visualize, and this is going to be a little bit hard to do, but that's exactly the chart. You have elevation on the Y axis, and we're going to go percent of Earth's surface on the X axis, and we're going to go from zero to a hundred percent.
We're just going to, we're going to compile this. So it's basically a, it's a total curve. We'll add up to a hundred percent by the end. So what we do is we say, okay, Chris, how much of Earth's surface is above, let's say four kilometers. Above sea level. Let's start high and go low. So how much of our service is between four and six or seven kilometers [00:09:00] above sea level?
And the answer is like, what, a couple of percent.
Chris Bolhuis: Yeah. It, it's, so I would say maybe, um, looking at the curve, I would say maybe 5% of the
Earth is above two kilometers.
Dr. Jesse Reimink: so really high mountains. There's a very few percent. So we're gonna go from like, An intersection with the y axis is at like seven kilometers. It's going to steeply go down to start So by the time we're on the x axis about five percent, we're down to like two or four on the y axis.
We're dropping down, down into [00:09:30] the right. Then Chris, we hit continental interiors, which are kind of, what, let's say, One kilometer to sea level. what percentage of Earth's surface is that kind of like one to two kilometers to sea level area?
Chris Bolhuis: So I would say maybe from 15% to, to sea level you said?
Dr. Jesse Reimink: Yeah, to sea level.
or let's
say, take
it all the way past sea level, take, yeah, take
it all the way
Chris Bolhuis: where it dives down. So yeah. Pl from 15 to 40 [00:10:00] percent?
Dr. Jesse Reimink: Okay. Yeah. So that's like, That's like 25 percent of our surface is kind of between one kilometer above sea level to one kilometer below sea level, roughly somewhere in there.
So our curve goes, it steeply goes down when it hits like 10, 15%, it flattens out because a large percentage of earth's surface is right at that narrow interval between one and minus one kilometers relative to sea level. So the curve flattens out. Then we hit the edge of the continental shelf and we get to this, [00:10:30] sort of transition towards the abyssal plane, which is how much of Earth's surface is between minus one kilometer and minus four kilometers.
There's not much that's in that transition
area. So our curve. less than 10%. Yeah.
Like five, 7%. And so our curve now is going to steeply drop again. And once it hits about minus four, four, kilometers below sea level, we hit the abyssal plane, which I mean, you could just look at a map of earth. There's a lot of, of the ocean [00:11:00] basin.
That's that area, right? I mean, I don't know. I'm looking at this chart. It's like 50 percent probably
Chris Bolhuis: Yeah. It's, It's, 50 plus percent
is
Dr. Jesse Reimink: plus, right?
Chris Bolhuis: ocean. Yes.
Dr. Jesse Reimink: So that curve again kind of flatlines for a long time and goes until we're far to the right on our x axis, we flatline farther on our x axis. Now the question is, how much is really deep, deep trenches?
The deep trenches, again, a couple percent, five,
Chris Bolhuis: Very, very small percent.
Yeah. Probably less than 5%. Yep. [00:11:30] When we're talking about things like the Tonga Trench or the Mariana Trench, these deep ocean trenches.
Yes.
Dr. Jesse Reimink: much area is that? It's not much on earth, right? We can look at a map and determine that. So our curve again plunges down until it hits 100 percent on the X axis in like minus 11 minus 12 kilometers on the Y axis.
So our curve, let me just summarize that. It's like. starts at the top left at the Y axis, dives down quickly, then flatlines in the continental interiors, then dives down again pretty quickly till we hit the ocean [00:12:00] floor depth.
And the ocean floor depth flatlines for about 50 percent of the X axis until we get close to 100. And then it dives down again really deep where the trenches are.
Chris Bolhuis: So Jesse, my plan now, as you've been rambling on here forever, I, I, I formulated a plan.
Dr. Jesse Reimink: Okay, good.
Chris Bolhuis: So I
Dr. Jesse Reimink: Chris, let me rephrase that. While I'm trying to paint a beautiful visual for the listener.
Chris Bolhuis: My mind is elsewhere that at that point, sorry. Um, and so was everybody else's, I think, but anyway, Sorry, [00:12:30] Dr. Reimink.
I
Dr. Jesse Reimink: It's quite all right. And guess what? So were my students last week, Tuesday.
Chris Bolhuis: Here's what I think I'm going to do, Jesse, is I'm going to use the hypsometric curve, I'm going to give it to them, they're going to get into their lab groups, and I'm going to have them think about this without me talking about it, I'm
going to have them,
Dr. Jesse Reimink: Chris. Do a lab on this. That's a
Chris Bolhuis: yes, exactly, exactly, like what you just did of breaking down the percentages of the different segments of earth.
we have the mountains, we have the [00:13:00] plains,
we have the broad continental shelf.
Dr. Jesse Reimink: Okay. This is a really good lab exercise that I want to know either how it goes, or if I keep teaching the intro level class that I currently teach, you know, revising our labs would be good. And adding a lab in like this, where So, are you thinking you look at a map and actually.
derive this curve, like make up this curve by looking at the topographic map of earth and
Chris Bolhuis: No, I wasn't thinking that I was thinking about looking at the hypsometric curve, something that I've really never used before in [00:13:30] saying, all right, well, let's first get the breakdowns. What do we have here? they're going to be able to derive what we have mountains.
We have this really broad plane that is just above sea level or just a little tiny bit below sea level. Then we have this deep dive to the Deep ocean basin, right? And so they're going to come up with, we've got mountains, we've got this broad shelf, we have the rise, we have the abyssal plane, and then we have these deep trenches and then assign percentages to that.
Right.
so that's a start. Okay.
Just
interpret the [00:14:00] graph. then what I want to do is, All right. Well, what kind of inferences can we make then
from this data? This is real data. what can we, can we make inferences about the small percentages and let's have our listeners start thinking about that a second,
if we have a
Dr. Jesse Reimink: Because this is where we're going. This is the point. And this is where we're both sitting up straight in our chair. I mean, this is this is where we're going with this entire episode. So
yeah, I like this idea. This is great. So Do you envision taking student? I mean, how much, I'll be curious [00:14:30] about this and we can use this for the podcast too.
How much help do you think students are going to need to get to the inferences that we're going to talk about here that you and I've talked about it? We're going to cover, like, do you think your students are going to need a lot of help
Chris Bolhuis: No, I, I don't
Dr. Jesse Reimink: No. Okay.
Chris Bolhuis: know. They're going to need some help.
Dr. Jesse Reimink: Let me ask another, a second question.
When do you envision over the course of the course doing this in the beginning, at the end, like how much information do they need? I guess those are two related questions.
Chris Bolhuis: okay. It won't be right at the beginning because they're going to need [00:15:00] some background information that, uh, you know, they're going to need to know, the types of crust that we have on earth. We have two types of crust. We have oceanic crust, we have continental crust. So I want to already have talked about that.
And no, I don't think I will have already discussed the longitudinal profile of a passive continental margin, of the continental shelf, slope, rise, and abyssal plane. I won't have, I won't do that yet. So kind of in between those two
things is I want to introduce the hypsometric curve.
Dr. Jesse Reimink: Gotcha. Okay.
Chris Bolhuis: so I think what they're [00:15:30] going to need, they're pretty quick. My students are pretty quick. And so they're not going to need a lot of help. They're going to be
able to, to get. they're going to get to, they're going to be able to deduce, all right, we've got mountains, we've got this broad plain and so on.
They're going to get the, five basic areas that I'm looking at on this hypsometric curve and assign percentages to it. They'll be fine with that. They don't need any help. Then what kind of inferences they'll need a little nudge.
And so I'm going to maybe give them keywords about,
maybe like,
all right, think about stability.
What [00:16:00] is stable and what's not stable
based upon the percentages.
Dr. Jesse Reimink: I like this a lot, Chris, I want to know how this goes for sure. And if you're listening to this podcast and you're a teacher and you want to know how this goes to send us an email and you want to use something like this, cause I love this idea and I want to use it.
I couldn't use it this semester, but next year I could certainly, we could revise the labs and there's aspects. we have labs that are kind of old and I would love to revise a few of them and do something like [00:16:30] this would be, would be kind of very thought provoking and cool.
So
Chris Bolhuis: Okay. All right. So it's going to be a minute because
I don't get my geology students until November.
Dr. Jesse Reimink: No, that's
Chris Bolhuis: So right now I'm, I'm teaching astronomy. So I'll get my geology students in November. Then it'll take us a little bit to get that far.
And then I'm going to definitely do this.
Dr. Jesse Reimink: Sort of in the new year or something like that. I like that idea a lot. A lab on this. Okay, so let's walk the listener through this lab. to the end goal is to get to these, these really, really amazingly basic, but really [00:17:00] important inferences. So the first thing that we can do, Chris, for me, this is the one that stands out to me again, we're pretending we're like, From outside the solar system coming in.
And all we can do is map the earth in topography. So we've got a LIDAR thing that goes around and that's about it. what stands out is the flat parts of the curve and the flat parts here mean that there's a lot of crust that's very similar elevation to a lot of other crusts. So the continental interior is that plus one to minus one kilometer elevation.
There's like, wait, what'd we say? [00:17:30] 25, 30 percent of earth is that. That's all one. thing. And then the other flat part is the abyssal plane, minus four to minus six kilometers below sea level. That's like 50 percent of Earth's surface. So those two things stand out. And what what basic inference can we say with that?
Chris Bolhuis: Well, if I'm going to nudge him and I'm going to say, all right, let's think about stability then well, because there's such a big percentage of those two types of crust. when you look at the curve or where you look at that longitudinal profile of a [00:18:00] passive margin, the part that is just above.
At and just below sea level it looks thicker, right? And so, and they will, they'll know this, you know, my freshmen know this, that the continental crust is thicker, it's more buoyant, it's less dense. And this curve clearly shows that. And then the other kind of crust is the oceanic crust. And that's the, deep part of the ocean.
That's the abyssal plane. It's much thinner. It's denser and it is, the antithesis of [00:18:30] buoyant, you know, it's with plate tectonics. That's what's involved in subduction and so on.
So
those two things.
Dr. Jesse Reimink: Exactly. We have two plateaus. there are different elevations and what we can infer from that is we have two different types of crust on earth, which is very basic, very first principles thing. We have two types of crust. One of them's thicker or more buoyant. It's actually both.
One of them's thinner or more dense. It's actually both. We have oceanic crust and continental crust and, you know, we wouldn't need to name them that. We wouldn't need to know that one of those below the [00:19:00] ocean floor and one of them's at near the surface understand that there's two types of crust.
One's thicker, more buoyant, one's thinner, more dense. Like that's a really fundamental thing about earth that we have on earth that is pretty unique to earth that we can look at and figure out from the hypsometric curve.
Chris Bolhuis: that begs the question then, since there's so much of it, does that mean you know, earth has this bimodal crust that you just described? both types of crust then stable?
Dr. Jesse Reimink: Yeah. And I love,
Chris Bolhuis: inference can be made?
Dr. Jesse Reimink: I love your intro with The word [00:19:30] stability or your, your, your sort of, um,
Chris Bolhuis: The nudge?
Dr. Jesse Reimink: the nudge with stability because it's such a great one. It brings up this question. What do we think? I mean, let's think through this. Do we think that it means that they're stable? At first, I would say Yes.
because there's a lot of it.
So either, I think the two options are either you're creating a ton of it very quickly, or it's stable. It's created and it doesn't decay away and it doesn't actually change elevation much. It's kind of bobbing up and down, you know, it's very stable.
And so let's work through that. Like [00:20:00] continental crust, we're producing some, we're producing a decent amount, at volcanic arcs and um, Subduction zones, continental subduction zone systems, but there's arguments that we're kind of destroying continental crust too, so that one to me is More of a stability thing.
so Yes. I would say that answers that checks the box. There's a bunch of it. So it means it's stable over long time periods. We know that from earth.
What about oceanic crust?
Chris Bolhuis: Well, it's different because in oceanic crust, is it being eroded? does that [00:20:30] process happen in a way that happens above sea level?
And, the answer's really no. It's not, not, not really, not much anyway, not significantly because it's underwater,
Dr. Jesse Reimink: But is it
Chris Bolhuis: it
is, it is, it's stable. And, and if you look at, happen to oceanic crust or what is inevitable with oceanic crust is that it's going to, because of plate tectonics, it's going to be involved in subduction at some point.
during its lifespan. this is why, [00:21:00] you know, one of the questions that Dr. Maddox loves to ask my students on the exam is, how old is oceanic crust? And, and, geologically, you, it's hard to find oceanic crust that's older than 200 million years.
And geologically, that's really young.
And so, why? Well, that's because it gets recycled in subduction zones of it
eventually. and So, it's not stable,
Dr. Jesse Reimink: it's not stable,
Yeah. Okay. I, totally agree. It's not stable. So I don't know that we could use, [00:21:30] we could really argue for stability, on a large amount of, of these two types of crust. Now let's come back to that because maybe we can, once we kind of put the other puzzle pieces in place that we, we can figure out using this hypsometric curve, we might be able to get there.
At least we can have a hypothesis about it. so let's move on to the next one. And Chris, I want to, let's move away from the two peaks in distribution or the, the two large, areas of earth that are a certain distribution. Let's focus on mountains first, because I think that flows nicely.
[00:22:00] high mountains, a small amount of very high mountains. Okay. We can tell a lot from this, but it's not, I don't think this is necessarily intuitive. The first one. It's certainly intuitive. Like when I asked my class, I say, okay, what do high mountains tell us? And usually it might not be the first answer, but one of the first three answers is there's stuff being pushed up.
know, they often kind of get too complicated with it first. And then I need to back them up and say, no, no, no, basic stuff. They're like, oh,
well it's stuff's being pushed up. Like there's stuff going [00:22:30] up, which. You always say there's two forces on earth, stuff that pushes stuff up and stuff that pushes stuff down.
And we're going to talk about both right. now, but,
Chris Bolhuis: That's right. I'm just saying that because we have such a small percentage of it, means that stuff is getting shoved up, but it also means that the second force is also very much at play. The belt grinder of weathering and erosion is an active process. So if this process is going on and has been for billions of years, then if it was stable, once it's created, it's [00:23:00] there.
But this curve says that not so they get knocked down.
Dr. Jesse Reimink: And so I think Chris I always have this discussion in my class before I talk about plate tectonics, because I want them to come at this without having plate tectonics in their mind, because I don't think that in my opinion, the fact that we have high mountains and we know that stuff's being pushed up does not mean plate tectonics yet, because There are other forces that people have talked about that could potentially create high mountains, you know, there's buoyancy stuff, there's this old expanding earth [00:23:30] kind of theories, which have been disproven now, but, but on a different planet, maybe there are forces that could push stuff up, To these extreme elevations that are not plate tectonics. On earth, we know it's plate tectonics. But that last point you made, the thing about erosion, that's one that my students rarely get to, because again, I haven't talked about erosion yet. I haven't talked about any of these forces. I give it near the beginning of the semester, like week two or three. But it's an important question. It's an important thing. we know there's stuff being pushed up there. So why isn't there a lot of it? Well, it means [00:24:00] the process only just started recently on earth, or it means erosion. It means that something is knocking it down.
That to me is a really cool conclusion you can make
just by looking at this curve. I don't know. What do you, what are your thoughts?
Chris Bolhuis: Yeah, I think so. what we're doing is we're looking at something that is a very, very basic idea in geoscience, the force that lifts things up, the force that tears things down, but we're looking at it from. a data standpoint. I've never [00:24:30] thought about it in this regard before, actually, before you brought this to my attention, this hypsometry, it's not a word that I've ever heard before.
and I love it though, actually, because this is something that maybe, like you said earlier, that we can look at Mars, maybe, With lidar or just, topographic profile and maybe make some inferences about what's happening on this planet or what has happened on this planet before.
Dr. Jesse Reimink: I mean, it's all hypothesis. If we, if this is the only data we have, we generate [00:25:00] hypotheses about the earth, but a very, very solid one is that there's something knocking these mountains down. There's something pushing them up and there's not many of them. So there's something pushing the mountains down.
That's very fundamental that there's erosion go up. There's some. There's something knocking these things down and I don't know that to me is just such a cool leap, or such a cool little bit of intuition. This is the beauty of geology to me is it's fundamentally this like very artistic storytelling science where we look at data and interpret it over long time scales.
But it's like we've talked about many [00:25:30] times, the basic things about geology, like cross cutting relations, it's not that obvious. Unless you've heard it, but once you've heard it, it's really cool and actually kind of obvious and incredibly powerful. This to me is kind of in that category of stuff,
Chris Bolhuis: Yeah. A hundred percent.
Dr. Jesse Reimink: little bits of intuition.
So
Chris Bolhuis: This is something that is like in education, just in general, the more we can expose younger minds to this idea of looking at real data and then making inferences from it it's a difficult thing for them to do [00:26:00] but it's definitely something that is emphasized on all of the standardized tests.
Dr. Jesse Reimink: Oh, is that right? Okay.
Chris Bolhuis: Oh,
absolutely.
Dr. Jesse Reimink: analysis, you know,
Chris Bolhuis: graphic analysis is absolutely,
Dr. Jesse Reimink: Oh, I didn't know that. Actually, I probably should have known that. But, um, on the standardized testing, this is like a big deal for
Chris Bolhuis: Oh,
it's huge. Yeah, this is so the more we can come across like really good examples of this and the hypsometric curve is, this is perfect
for that kind of
thought experiment.
Dr. Jesse Reimink: This'll be cool. Yeah, this is cool. I, I, [00:26:30] if this would be fun to kind of build a lab that would,
that, I mean, you're, you can go like we've talked about before into more detail than, than I do in the, in the college class. and so we might have to make a shorter version for my, for my class or shorten the one
you make in some way, shape or form, but, okay.
So can we move on to the trenches,
Chris Bolhuis: Yeah, the last one, the last tiny little sliver, the last aspect of the hypsometric
curve is these really, really deep sea
Dr. Jesse Reimink: We're going to jump all the way to the right in the hypsometric curve, you know, between 95 percent [00:27:00] and 100%. So 5 percent averse area is like really deep trenches. And you said it before talking about the Tonga Trench. talking about these trenches that are in the ocean floor that are really, really deep.
And.
Chris, this was used. There's a really cool, we'll talk about this in an upcoming episode, but there's a really cool story to this where people who were doing back in the early days of plate tectonics, like pre plate tectonics ideas, people were doing a lot of gravity measurements and they'd take ships and they'd have a a Gravitometer.
in the chip and they'd, they'd drive around and [00:27:30] measure the gravity field. And you know, you could see mountain ranges. You probably talk about this in class. You can see mountain ranges. You can see the gravity of mountain ranges. You could see the lack of gravity.
They drive over trenches. They could see the lack of gravity in the trench. they actually started to piece together plate tectonics because of this or proposed. Plate tectonics. And this is kind of, this is a bit of a leap. This is a bit of a, this is certainly in the hypothesis that needs to be tested category.
But okay, if we back up number two, high mountains told us that first of all, stuff was being pushed [00:28:00] up and they were being knocked down and that's likely erosion. So that material, that mass has to go somewhere. And it's not too hard to understand that it probably goes into the ocean. So then where's That connection between there's erosion happening, but there's a trench. How do we get to plate tectonics from there? That's like a tricky equation. Erosion plus deep trench equals plate tectonics is complicated. how will you like nudge your students in this direction?
Chris Bolhuis: Well, again, thinking about stability, you'd think, well, maybe because there's [00:28:30] such a small percentage of deep, deep, deep sea trenches are they getting filled? By some mechanism, like is the erosion from the high stuff on the, continental side, is that getting, shoved out into the deep oceans and, and to the deep sea trenches and filling them,
thereby removing them.
Dr. Jesse Reimink: Okay. There we go. It is right. Like we know erosion is going out. It would fill up the trenches. That's. A pretty sound interpretation, right? In your mind, do you, do you think
Chris Bolhuis: Yes. Yeah. Because these deep sea trenches are not that far off the shoreline.
they're [00:29:00] nearer the source of the sediment,
it will make its way that far for
Dr. Jesse Reimink: So the sediment would fill these up if they were stagnant.
So therefore the fact that
the trench exists means what?
Chris Bolhuis: you have two forces going on there as
Dr. Jesse Reimink: Exactly. Oh, it's so good.
You're actively creating the trench too. it's an active process of creating the trench. So, it's so cool. I find this so cool. The fact that the trench exists [00:29:30] means, erosion, that we're dumping stuff into the ocean basin, the fact that the trench exists and that it's so cool.
Yeah. Freaking deep, six kilometers of trench below the abyssal plane. The fact that it exists means that it has to be actively being produced. It's like mountains. The fact that they exist means they have to be actively, being pushed up because they otherwise they'd be destroyed. The earth wants to be flat everywhere.
It was just like the fit, the processes want to make it flat. this is where the plate tectonics theory. one of the ways that it originated is like, oh wait, there has to be an active [00:30:00] process creating a trench. What's a good one? A good active process creating a trench is this oceanic plate diving down into the mantle.
That's
a pretty good way to keep a trench active over long time periods. so That's
certainly a hypothesis, if this is the only data we have. But it's a sound one when we get more data. Like it's, it's a, it's the simplest explanation for keeping a trench active for a long time. So I love that one. cause you were kind of building this.
We're saying we have two types of crust on earth. We have mountains that are going up. We also can tell that they're being knocked down [00:30:30] because there's not many mountains. So because there's stuff being knocked down, that stuff's going into the oceans. We know it's going into the ocean. So therefore, because we have trenches, they would be filled up if, you know, The trench wasn't being actively created.
So the trench is being actively created. So we can look at this curve And, say, we live on an active planet. it's a,
pretty good bet that there's erosion and, plate tectonics going on
all from the hypsometric curve.
Chris Bolhuis: and, you know, it's really, this is interesting thing because, I think all of our listeners know that we live on an active planet and they [00:31:00] knew that before this episode, but this is just looking at it from a different standpoint than I think many, and most maybe, most people have
Dr. Jesse Reimink: Totally.
Chris Bolhuis: it
Dr. Jesse Reimink: I would bet. I wanted to kind of end with this, but you kind of answered it already. Cause I know that some of the textbooks have this hypsometric curve, you know, in it
and talk about it, but it doesn't, it doesn't feel to me that it takes, it's not fundamental. Whereas I've kind of structured my lectures a little bit around it being kind of a fundamental process.
And I keep alluding back to the [00:31:30] hypsometric curve throughout the rest of the course a little bit, just because it's kind of this fundamental thing, especially when I get to play tectonics. Do you think I mean, okay, you've answered it. Cause you, you want to make a lab. So I was going to ask, like, do you think this is a useful, like teaching tool?
but you've kind of already answered that. But that's interesting. It comes from this data driven standpoint that that students, there's an emphasis on getting students to like read and understand and infer stuff from data. That's a really, I hadn't thought about that before.
so of with that, I want to ask you a question about this to [00:32:00] back to the stability thing, I could see a way that we here with there's deep trenches, therefore there's plate tectonics, and, and What, we mean is that oceanic crust is likely diving down into the mantle, so there's, the oceanic crust is diving down into the mantle.
can we bring that back to the stability question? Do you think students would be able to make that connection to bring it back to stability where we talked about stability in the beginning?
Chris Bolhuis: so what you're asking is, do you think that they will be able to deduce that the deep sea [00:32:30] trenches are not stable?
Dr. Jesse Reimink: Or that oceanic crust is not stable? whereas continental crust is. high mountains get knocked down to continental crust level. The ocean floor gets subducted down trenches.
I think we can make a hypothesis link, if you really think about this for a long time, I think you might get there.
My question is like, could students get there to back to
the stability thing and say oceanic crust is not stable, but kind of crust is stable
Chris Bolhuis: I don't think right at the outset, but what I envision happening is they're going to then, put the, [00:33:00] you know, They're going to identify the different parts of earth based on the hypsometric curve. Then they're going to assign percentages to it. Then they're going to start thinking about what's stable and what's not stable.
And they're probably going to say that oceanic crust looks like it's stable. I would, I would expect them to get to that, but then we're going to have a class discussion about that. And so just by asking more questions. Kind of like what you and I did walking down from the Tetons 20 year plus years ago, is they're going to be able to [00:33:30] deduce that.
No, it's not without me answering it. I'm just going to ask them other questions because they do have a fundamental background in geoscience already because they took, you know, my class as, freshmen, just. Earth science.
Dr. Jesse Reimink: Yeah. Yeah. Yeah. Totally. Okay. Gotcha. Yeah. I mean, that's impressive. That's very cool. I'm so interested to know how this goes. And, uh, you know, we keep talking about this, but,
Chris Bolhuis: When I, when I think about I just said to you, Jesse, I think I am so [00:34:00] proud of the school that I'm a part of, that I work for in that we provide a really Good background in and then with electives, know, thrown into that, like my geology course and, and then astronomy, there's a lot of planetary geology that goes into a class like that.
Also, it's so unusual. I think for a public school to have that deep of
Dr. Jesse Reimink: definitely. And it [00:34:30] speaks, you know, it speaks to two things, you know, it's, it's it's 90 percent you and it's 10 percent your administrators, like allowing this freedom and flexibility to navigate. And, you know, I, I went through Hudsonville public schools and the science department was great then.
And it's been great for a long time. I mean, your dad was a great biology teacher there. My dad was a great biology teacher there.
The science department has been very, very good in many different fields. And,
geology is, you know, one of the big dogs that barks
there, I,
think now, and you, you produce, but, but, you know, to brag [00:35:00] for you, you produce or Hudsonville produces, I forget what the long term average is, like seven or eight.
Geology majors who end up going on into geoscience and usually that gives a college geoscience degree in some way shape or form and be either teachers or researchers or professionals in the industry, various industries, that's a high number for especially for the state of Michigan. That's a very high
number.
and
Chris Bolhuis: I would not say I want to push back on one thing though. It's not 90 percent me because only one of four people that [00:35:30] teach freshmen, all the freshmen that come through our
school, they, they, they,
You know, they actually do the most of it because I teach these other electives to, for the upper classmen.
I teach geology and, and astronomy. And so, I'm not,
Dr. Jesse Reimink: No, that, that's totally fair. And the summer science thing, you, you know, you've done that for a long time, but you're half of that team always. And I was more speaking of the upper level stuff, you know, like you, you got to create astronomy. You created the geology thing
and somebody is going to inherit that, but, and, and hopefully, [00:36:00] keep, running with it, but, um, got, someone's got to,
Chris Bolhuis: Yeah. Yeah. Right. Yeah. Yeah. I don't, you know, I don't know. Yeah. Okay. All right. I just want to, like, I don't want to slight anybody. I work with amazing people and, uh, we do a really, I'm just proud of it because I, when I think about what my geology students are going to be able to do with this hypsometric curve, I think they're going to do a lot with it because they already have a really good background in geoscience. So I, I will be able to hit this Out having talked about a lot of these [00:36:30] concepts in my geology class.
Dr. Jesse Reimink: Well, I think again, I think that, you know, okay, somebody sitting there listening is probably, Joyce is probably like, what the heck are we talking about here? Why are we talking about this? And to bring it back for Joyce, I hope the term of the day for Joyce is hypsometry. that's H Y P S O M E T R Y, hypsometry. and it's a completely unnecessary term for the vast majority. So,
why are we making an episode about it? It's a cool, I think it's an amazing bit of intuition of [00:37:00] geological intuition that you can piece together these really fundamental things about a planet, our earth, because of this curve.
And so, although it's a useless term. I think the term is valuable because it describes the data that we would use to, get to these inferences. And it kind of aggregates all sorts of ideas about the earth. Really basic ideas from like different parts of an intro level class. I mean, you, talk about erosion until the weathering and erosion chapter.
And there'd be one chapter on plate tectonics and there'd be one Chapter on the oceans and stuff, but linking [00:37:30] them all together, the hypsometric curve, the value of it is that it links them all together in this really fundamental way, I think. So
that's why we did an episode on it,
Chris Bolhuis: but perhaps
Dr. Jesse Reimink: a tedious episode.
Chris Bolhuis: no, I don't think so at all. This is fun, actually. For me anyway, you and I had fun
talking about this, but I think maybe, yeah,
she always says, um, I think maybe it could have been, called the elevation curve or
something like that, just Much, simpler.
Dr. Jesse Reimink: A topographic curve. I mean, something
simpler, but Hey, we got to
get it. We got to
get Latin with it. And the hip [00:38:00] symmetric, you know, it's so good.
Well, I don't know, Chris, what do
you think? Is that a wrap?
Chris Bolhuis: I have, it is, but I have not gotten my merch yet. I ordered merch and I haven't gotten my hat and
shirt yet. So.
Dr. Jesse Reimink: way.
The
white glove delivery service is coming.
Chris Bolhuis: I
Dr. Jesse Reimink: on your door
Chris Bolhuis: to, uh, to, be able to surprise you with it today, but no go.
Dr. Jesse Reimink: you gotta be patient, man. It's coming.
Chris Bolhuis: All right. I'm not a patient person. I'll tell
you that. It was not
one of my
Dr. Jesse Reimink: person. No, we'll, uh, we'll have to record what [00:38:30] planet geo hats on
next
time. All right. Plan geo hat, plan geo shirt. On that note, there's a couple ways to support us. You can go to our website, planetgeocast. com. We have merch now.
There's a hat, a shirt. We're going to be adding some stuff to it as well. A couple different varieties of hat with the planet geo logo. So that's one way to support us. Another way is download our mobile app. First link in your show notes. we have a ton of visual podcast series.
The main one is this course that Chris and I teach. I teach the college level and Chris teaches basically it's college level to high schoolers. We have most of that entire course In [00:39:00] visual podcast series there for free. You can also buy audio books and some of them are Podcast plus images and some of 'em are standalone audiobooks on the geology of the amazing national parks that our country has to offer.
You can send us an email, planet geo@gmail.com. You can also follow us on all the social medias at Planet Geo Cast
Chris Bolhuis: Cheers. [00:39:30]
