The Geology of Eskers
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[00:00:00]
I hit record one. so, we we've got to back up, Chris. okay, so for,
Chris Bolhuis: You never know what you get with me, do you?
Dr. Jesse Reimink: just joined us here to this very podcast, my camera's out of focus. [00:00:30] So when I does that, I kind of stick my hand near the camera to try and get it into focus, to get Chris, you just go, wait, you have this thing on your hand and I've always thought it's a callus. It's like a callus kind of in the, near my like ring finger right hand, like, you know,
Chris Bolhuis: How long have you had this callus? Like forever, right? You've had it. Yes. Yes.
Dr. Jesse Reimink: my other calces kind of gone away or come back been there.
And you, what It's something you just went to your skin doctor and they
Chris Bolhuis: I went to my skin doctor. I, And I'm like, Hey, um, can I have this callus removed? [00:01:00] And he's like, that's not a callus. That's a I really should know what it is because I want to get it
Dr. Jesse Reimink: well, I want to describe it the way you just described it, which was a disorder.
Chris Bolhuis: Yeah, it's something like that. Yeah.
it's,
Dr. Jesse Reimink: so things about myself by doing this podcast with you.
I have
Chris Bolhuis: I, I'm a you actually do, and it, you should get it taken care of because it'll cause your tendon to contract so you'll lose flexibility in that [00:01:30] finger. So it's your ring finger on your right hand.
Dr. Jesse Reimink: Yeah.
Chris Bolhuis: That's that's that's where it is.
Dr. Jesse Reimink: Wow. Okay. I'm going to have to go get this dissolved or taken care of in some way.
Chris Bolhuis: Yes. So I've I've known about this for two years. No. Um, I keep forgetting about
it and, and I just went and saw him and I wanted to, I wanted to ask him what, like, what, hey, what's the name of that again? Because he recommended that I go to an orthopedic, surgeon and they, they put an injection in which [00:02:00] dissolves whatever you and I have going on.
Dr. Jesse Reimink: Amazing.
chris_1_08-24-2024_104332: I
Chris Bolhuis: I
Dr. Jesse Reimink: Wow. A diagnosis on, planet geo here. This is great. This is,
Chris Bolhuis: Yeah. I know you should ask your doctor wife about
Dr. Jesse Reimink: I will, I'll ask my doctor wife, she'll probably say, don't worry about it.
Chris Bolhuis: ha. Ha, ha, ha, ha, ha, ha,
Dr. Jesse Reimink: door and be like, he'll inject great. It'll dissolve my problem.
Chris Bolhuis: Yeah. Yeah. See, look at me your problems.
Dr. Jesse Reimink: stuff. I mean, this is the biggest contribution you've made to [00:02:30] this podcast in a long time, Chris. Well done.
Chris Bolhuis: That's not no, that's not true. That's not true. This is a small contribution,
I'm your trigger finger . Mm-Hmm.
Dr. Jesse Reimink: Today is going to be a big Today. I'm excited about this episode. we're talking about eskers today and well, I learned from you what eskers are in, high school geology class, probably even before that, you might even cover eskers in earth science, ninth grade earth
Chris Bolhuis: Little bit. Little bit. Really, really basic Yes. just identify an Esker, you know? 'cause they kinda look like these really sinuous, they're really cool ridges. [00:03:00] I dunno. So that's, that's all
Dr. Jesse Reimink: no, but, and then in geology, you know, you taught me the, the sort of intro level textbook version of, of an esker, which is, okay, here's how it forms. a river under, glacial river that's running and, and it kind of gets deposited this sort of shoestring sinuous, ridge of sediments.
that's true, but they're a lot more complicated than that. And important nuances, Chris, because, you know, that description, like, And I'm not saying you teach it this way, but, but if [00:03:30] you're describing it to somebody on the street and you're like, Hey, this is what an esker is.
If I'm describing it to my in laws or my, my parents, what is esker? I say, yeah, it's a, it's a glacial river that deposits sediments. You go away and say, okay, makes sense. Good. But then you go away and think about it a little bit. And there's a couple of like inconsistencies with that singular model, right?
If somebody pictures a glacial river, a lot of people listening probably have seen this, like you imagine, I've, I just recently saw a YouTube video of some guy kayaking on a [00:04:00] flung on top of a glacier, right, and it's beautiful, looks really
Chris Bolhuis: Yeah, because it's, it's this really, really blue water. it's
beautiful. Yeah.
Dr. Jesse Reimink: Beautiful. But the blue, Chris, it's clean.
This is clean water. it's not depositing anything. And it's also at the ground. It's on top of this glacier. So like, know, the simple explanation, it flies, it makes sense if you don't think about it too but as soon as you think about it deeper, it doesn't make sense.
Chris Bolhuis: Exactly, Jesse, but that's everything that you and I do in our intro level classes. The stuff that we teach [00:04:30] really, all of it is nuanced and none of it is quite as we depict it for this classic textbook model going right on back to, you know, how does granite form? Well,
it's the same thing.
Dr. Jesse Reimink: granite one, you can go a long time without realizing the inconsistencies in the granites. I think you just got to think about eskers for about five minutes and then be like, okay, wait, does this, this doesn't make sense. This is a little [00:05:00] counterintuitive.
Chris Bolhuis: well, let's go back to a couple of basic glacial principles. glacial deposits fall into two basic categories. You have what's called stratified drift and glacial till, and they're very different. And the feature that we're talking about today with eskers, it's a deposit that's made of stratified drift.
In other words, this is sorted. It has. Rounding. It has everything that any other stream deposit would have [00:05:30] because water is very discriminating in terms of, it can only carry certain size particles dependent upon the energy of the water and how fast it's moving and so on. Whereas glacial till.
is sediment that's deposited directly by melting ice. And ice is all inclusive. Ice doesn't care. It can carry anything. It can carry a, a boulder the size of my house and a grain of sand, and it doesn't discriminate between them. And it also doesn't do much rounding. So you don't [00:06:00] have any sorting. You have no rounding.
It just, wherever it gets plopped off, it gets plopped off. And so they stand in stark contrast to each other. Glacial till. Versus stratified drift. Strata implies water and layering and sorting and everything else that water would do.
Dr. Jesse Reimink: If you picture a continental scale glacier, huge glacier, many miles thick, where it starts to melt, it's a conveyor belt. It's like a massive conveyor belt where you get a conveyor belt at your grocery [00:06:30] store. If you just dump your groceries on there, the conveyor belt is not discriminating. It is just dumping groceries off in a pile at the end.
It's just going to keep going until they pile up at the end. That's what's happening with a glacial system that's forming till. So it dumps this blanket of till, relatively continuous blanket of till on the landscape. So if you go up to Northern Canada, and Michigan too. You'll see glacial till deposits that are, they don't have a ton of variability across them.
It's kind of like a big thick blanket of [00:07:00] unsorted Eskers are, as you said, water deposited sediments. let's dive a little bit more into the details here. the esker is a depositional feature from a stream, and the stream is forming the water in the stream is forming from melting glacial ice.
But we have to think, here's where the kind of nuances come in here, we have to where Chris does a glacier melt? Where on the glacier is it melting? And I think it's kind of maybe potentially obvious, is this an obvious one
Chris Bolhuis: I think so. glacial meltwater [00:07:30] is in abundance near the margin of the glacier. Because that's where it's warmer, whether that's, uh, you know, in alpine regions at lower elevations or continental ice sheets where it's, think about Greenland, most of the glacial meltwater is going to be near the ocean, near the edge of the continent, where the glaciers are terminating, where they're kind of ending.
Mm
Dr. Jesse Reimink: That's right. And they can be seasonal in the summertime when starts to up, the top layer of the glacier near the air is going [00:08:00] to have more seasonality to it. It's going to warm up, start to melt in the summertime, produce meltwater. That meltwater is going to flow downhill, which on a daily basis.
continental scale. We'll come back to this, but on a continental scale glacier, it's away from the center of the glacier. Think of the glacier as an ice cap or an ice sheet where it's thickest in the middle. It's thinnest on the outside, kind of like a pancake. You put your thick pancake batter on the pan and it kind of spreads out.
That's what the glacier is flows downhill, which is kind of radially outward from the center of the glacial ice sheet. so it's flowing out [00:08:30] there, but it's clean water. Think of that visual of some kayaker kayaking on glacial meltwater river. It's clean. There's not much
so we, and it's also not on the ground surface. So it's not depositing anything on the ground surface. it could magically deposit something right below itself, the glacier would scrape it away. So we would lose that record. So how do we get that water that's in on the top of the glacier to do the depositing of the esker that we're going to talk about?
Chris Bolhuis: Well, we have another intermediate [00:09:00] step that we have to get to, which is also near the margin of the glacier, near the, lower most elevation or where the glacier is terminating, You also have crevasses and moulins and moulins are these like vertical shafts or cracks that go from the surface down toward the bottom of the glacier.
So you have these very clean streams on the surface, abundant water that then dives down into a crevasse or dives down into one of these [00:09:30] moulins to the point where it hits the bedrock, the bottom of the glacier.
Dr. Jesse Reimink: These cracks go deep. As soon as you dump water into a crack, it's going to, especially an ice filled crack, it's going to start to melt the ice, erode the ice until it works its way pretty quickly, probably down to the bottom where there's no more ice, which is the bottom of the glacier ice sheet.
So Chris, quick question for you. You were just in Iceland. did see a lot of glacial meltwater? And did you see any, anything like this?
Chris Bolhuis: So yeah, we, what we [00:10:00] saw in Iceland were the abundant meltwater coming off. In fact, there was a day that was in the, near the town of Vík where they had, this glacial flood that wiped out the road, wiped out the ring road. And that's the main road around. And so, people were stranded because they would, they went to, let's say they went to Vík from Reykjavík And then they couldn't get back to Reykjavik without going all the way around from the South Shore [00:10:30] all the way around the North Shore back to Reykjavik.
So, either that or they had to wait a few days till they could open up the road again. So, because what they had is, you know, Lots of, well, I told you about this, lots and lots and lots of rain. And so, this is exactly what we're talking about. So yes, abundant water. And what we also saw is abundant cracking near the lower margins of the glaciers.
Absolutely. And it just, it was just beautiful.
Dr. Jesse Reimink: did this give you, you know, your trip and what you saw? Did it give you a new [00:11:00] appreciation for the, the specific processes we're talking about with eskers here? How like, how sense that this model makes sense.
Chris Bolhuis: A hundred percent. Absolutely.
Dr. Jesse Reimink: that's, that's cool. Oh man, I wish I could see that.
That, that, uh, I mean, I've seen this not at this scale anywhere near the, some of the, the, there's like, quote unquote, ice caps the Canadian Rockies. They're not huge, but they are they are alpine glaciers in a serious way, but you don't often see, you know, meltwater in these channels in the same scale.
Just, they're not the same [00:11:30]
sheet.
Chris Bolhuis: There are a lot of YouTube videos that really capture this well, all this melt water on top of a glacier, beautiful blue, clean water, diving down into a moulin. you can get this. It's a, it's a real quick, YouTube search. And there's a lot of it actually.
Yeah. Yep. Yep. Yep.
Dr. Jesse Reimink: to take a look at that. So, build upon this story so that we're, we got this glacial meltwater, it hits a crack somewhere, and it dives a crevasse or a moulin, and it dives down in, eventually works its way to the bottom.
Now, Chris, the [00:12:00] important thing here is we have this Pressurization. This is really important for esker deposition is because, and I don't know the best analogy, maybe it's like a water tower or something, but have water flowing kind of straight down into the glacier. It hits the bottom
Chris Bolhuis: it has nowhere to go. Right. That's where the pressure comes from.
Dr. Jesse Reimink: that's right.
It's got nowhere to go initially. And it starts to it has to sort of melt its way out of that. So there's a ton pressure. And even when it does, I think it's kind of like a pipe that's flowing downhill, water pressure in [00:12:30] your house. So you, you have. water pressure because there's a big water tower nearby that's putting the water up high I mean if you're on city water, that's the source of water pressure so you know, if you imagine glacial melt water flowing down through crevasse that's a lot of pressure that's building up there and backing this up and that's a key part because water under pressure, especially in ice, will start to do stuff to it,
Chris Bolhuis: that's right. Yeah. This pressurization is really important in the development of eskers. But I do wonder about [00:13:00] one thing because I do this with my, geology classes is, I want to show the effect that pressure has on ice, because if you think about it a second, Water, when it freezes, it expands by about 9 percent that makes water a bit of a chemical freak because most things, when they go from the liquid to the solid phase, they contract, but water does the opposite.
It expands. So if you take two ice cubes, put one on a lab table and then put it the other on the lab table, put a 10 pound weight on it and just watch what happens. The [00:13:30] one with the 10 pound weight melts. Much, much faster because of the pressure that you're exerting on that ice cube, but, because what you're doing is essentially you're contracting the ice, making it more like a liquid in less like a solid.
I wonder about the effect that pressurization has on its ability to melt its way through the bottom of the
Dr. Jesse Reimink: yeah, That's a good That's a really interesting question. I mean, I, I would imagine probably, certainly some right of, the ice at the bottom is [00:14:00] certainly under high pressure and probably a lot colder just the freezing point, right? So. It probably, it certainly has a bunch, but the important thing is that it is doing that melting for either pressure reasons or, or just erosion, like think of water erosion, erosional pressure, the important thing is, is it starts to melt, when it starts to melt, it is gathering all the sediment from the ice, that ice, especially at the bottom, is carrying it's the ice at the bottom that has done all the scraping from upstream in the glacial system, so it's
Chris Bolhuis: The and [00:14:30] the plucking.
Dr. Jesse Reimink: so this is the cool part, and this is where we start to form an esker, is we start to pick up sediment, this ice does a couple of really cool things, because it's under pressure, it means that it can flow uphill very easily, and I've seen this in eskers, Chris, in Northern Canada, we're flying in a float plane, or we're driving esker system, and you can see, You'll be flying along and you'll see that esker goes up a hill a long ways it's, continuous.
You think of a stream, when a stream hits a [00:15:00] hill, it'll sit there and pile up water, make a lake. And so the deposit type would be completely different if it was just a normal stream. But this is a pressurized conduit at the base of a glacier. the esker, the, The deposits we see now, they just go uphill and they don't change at all.
kind of amazing. Like you look at it and you're like, can't be a normal stream. That's something And it's this pressure that is allowing it to go upstream and it doesn't change the physics of
flow
Chris Bolhuis: right. And it's going to continually be under pressure [00:15:30] because remember water is still dumping down into the crevasse or the moulin. So even as it melts its way out, it's still being pressurized. And so flowing uphill because it's under so much pressure, no problem at
chris_1_08-24-2024_104332: all.
Dr. Jesse Reimink: It has no issue doing that at all. I mean,
it's a really, a really,
cool thing. And this water is melting the ice around it. It's eroding. It's, it can flow uphill. It can flow over stuff. It can flow sideways. does all the normal things that, rivers do, except it's probably kind of a short one.
It's [00:16:00] under pressure until it exits the glacial front. As soon as it kind of, I don't know if it spews its way out, but it will eventually flow its way out.
Chris Bolhuis: Hold on, Jesse. So let's about this without like talking about it right away. What happens once this becomes, where it loses pressure? What's going to happen to the flow velocity? just so you think about that a second, you know, it's obviously it's going to lose pressure.
Some of it anyway, not all of it, but it's going to lower its pressure, which is going to cause the water to slow down. What happens when the water [00:16:30] slows down?
Dr. Jesse Reimink: dumps its stuff out.
right.
out, right? So it'll lose pressure for two reasons. One, it's flowing out, it's flowing out into the open. And two, as this pressurized water is flowing through this, what we What we'll talk about next is this R channel, this, this cavity that it kind of cuts for It keeps cutting and getting bigger. So you take a high pressure water in a small little hose and you put that same amount of water through a larger diameter hose and the water pressure drops, right? So that's kind of what's going on too. So we're, we're decreasing the water [00:17:00] pressure as it's flowing through this, which is causing it to take all that sediment it and deposit it into a, usually a gravelly ridge. Sometimes it's two ridges that are parallel. Sometimes a little more flat top. Sometimes it's really sharp peaked, but it'll deposit all that sediment on its way out of the glacial front.
Chris Bolhuis: That's right, Jesse. And the sediment that's going to be deposited is going to be very, very gravelly, as you said, very coarse grained pieces that are all the way down to sand too. So you're going to have this, it's kind of like [00:17:30] sandy all the way up to gravel sized pieces.
They're rounded. They're sorted. it's this like long sinuous kind of ridge that follows the path that the water created, melting its way out of the glacier, melting its way out the glacial front.
Dr. Jesse Reimink: I mean, this is such a cool, such a cool process in detail. And it's so different. It's actually so different from I mean, it's, it's similar in like a very simple way, but so different.
Chris Bolhuis: let's take a step back, Jesse. If we look at this on a regional scale, there's a [00:18:00] geometry to eskers.
On a continental glacial scale, think about this a second, you have this continental glacier that's oozing out, like you said earlier, this kind of like thick pancake batter you pour in a skillet, it spreads outward from every direction. So what this kind of shoestring esker looks like they look like spokes on a wheel, if you will.
So you can see where the zone of accumulation was for that particular glacier. [00:18:30] Because the eskers, if you kind of extrapolate them back, they come to this relatively central point, the hub of the wheel,
if
you will. So that's another really cool thing.
Dr. Jesse Reimink: totally cool, Chris, and where we, I'll talk a little bit about our esker work up in, up in Northern Canada, but where where we were in Acosta, they're flowing basically due west, the eskers are all straight west. You go a hundred miles north of there and they're flowing Do Northwest and that's because the different ice sheet, you know, the central point of the ice They're kind of radiating out from the [00:19:00] central point So you can really easily see this as you're flying around and actually these Eskers especially up in northern Canada our floatplane pilot told us this but eskers used to be before GPS They were the main navigational tool of floatplane pilots and people, dogsled racers and stuff is you'd get on an Esker and you'd just follow it because you actually knew which direction you were going and you'd get on and you see an Esker and you'd be like, okay, I know that that's pointing northwest.
So I know my direction now.
Chris Bolhuis: What an awesome, [00:19:30] wow. That's so cool. that's amazing.
Dr. Jesse Reimink: there's a really like famous Esker system. it's a long Esker system. It's like 250 miles of continuous Esker. That's like the famous navigational corridor one that all the pilots, you were going somewhere, you'd be like, all right, I got to go 150 miles along this Esker system, and then hang a right, you know, it's that kind of thing.
Chris Bolhuis: cool.
Dr. Jesse Reimink: Right.
Chris Bolhuis: Well, Jesse, let's leave this then and head into, this pressure and the melting creates [00:20:00] what's called an R channel. And the name may be a little bit misleading. So let's, why don't you take this head into what is an R channel and why is it called that?
Dr. Jesse Reimink: the second part is easiest. called an R channel or a Roethlisberger channel for the author who wrote a paper that described this process and then, uh, know, somebody else some other scientist said, okay, we should call it a
Roethlisberger channel or an R channel. Um, but
Chris Bolhuis: real quick. Hold on. I'm sorry to interrupt your flow. But the reason why I said that our channel might be misleading is because we [00:20:30] often describe river valleys as v shaped valleys Glacial valleys as u shaped valleys and R has nothing to do with the shape of the
channel
Dr. Jesse Reimink: story about why it's called an R channel a Rothlisberger But anyway, that's why it's called that. this R channel, it's the channel that the river is following at the base of the glacier, so it's this pressurized tube that the river cuts for itself at the base of a glacier, [00:21:00] and basically what's happening is we described all the processes here earlier, but It can cut up river water is under pressure and it's going to follow the path of least resistance which is kind of you know downhill or out from the glacial front out towards the glacial front but it's also going to cut up because that's the place where there's the least pressure so this is it's like a stream morphology except flipped on its head because this pressurized water will start to cut up into glacial ice above it to get more
Chris Bolhuis: Or it [00:21:30] or melt up
Dr. Jesse Reimink: melt cut, melt up.
and as it's doing that, remember this ice is the stuff that has all the sediment in it. And so it starts to coalesce or aggregate all the sediment from the ice or really, I don't know, inherit all the sediment from the ice that it's eroding or melting in this channel. So we end up with is what's called an Esker Corridor, where you have a single ridge of sediment, and all that's, it's kind of like, I don't know Chris, the [00:22:00] river scraped all the sediment in from the sides and deposited it in a little ridge, so all the till gone from near the
Esker
Chris Bolhuis: what, well, hold on. Well, we're taking the till and now it's getting picked up by the water. And as it does this, cause till's unsorted, unstratified, unrounded on everything. Now it's getting all of the characteristics that any other water, the further it goes, the more rounded it gets, the further it goes, the better the sorting gets and so on and so on and so on.
Dr. Jesse Reimink: So let's play this [00:22:30] forward here. Now that water it's full, it's, it's, it's sorting this stuff. rounding it. It's going to dump it in a ridge right near where that R channel is, like it's going to start deposit sediment. As the R channel gets bigger, the water pressure drops, river starts to deposit the sediment in there because it's losing pressure.
It eventually hits the glacial front and flows out into the front of the glacier, and it's going to have lost all of its major sediment. It's going to have lost all the sand sized pieces, all the cobbles,
Chris Bolhuis: All the big stuff would have come out
already
Dr. Jesse Reimink: stuff comes out. All that's left is the [00:23:00] really fine particles. The clay size stuff is all that's going to be left in the water.
And so what that means is when the river flows out the front, there's no more esker being deposited. the esker is being deposited still in this like ice channel, the R channel in the ice sheet. once it flows out, then it flows into like a lake or an alluvial fan deposit and the stream really slows down.
Then it clay sized particles on itself. So if you have a, just a, a snapshot in time, our there's no [00:23:30] esker ridge when the river water is on top of the glacier. there's no esker. Deposit being formed when that water hits the base of the glacier And there's probably not much esker being deposited first several meters this r channel It's only at the later stage that the esker ridge starts to get built up And then you get an alluvial fan deposit at the outset.
So that's like a
see in the modern
that happening.
Chris Bolhuis: If you think about it, most of the deposition, [00:24:00] the ridge, the Esker ridge begins when it starts to depressurize as it's melted, its way out to the leading front of the glacier. So as deglaciation happens, as the ice retreats, the esker then is gonna follow the retreating of the ice.
So that ridge is gonna lengthen backwards. It starts at where the glacier was, but as the glacier continues to retreat, retreat, retreat, the esker then is going to lengthen because that loss in pressure [00:24:30] follows the leading edge of the glacier.
Dr. Jesse Reimink: Chris, I'm curious on your, your take on what I'm going to say here, but that process, you just described that process that, that the conveyor belt Glacial retreat is just so important to making an esker and to making these deposits.
So if you play that model out where you just said you play it out over time over 10, 000 years of ice retreat You're going to have the result is going to be a continuous esker ridge with alluvial fan [00:25:00] deposit Andesite coming after it, kind of draping over the esker, or sort of on top of the esker, the esker poking out of alluvial ridge deposits, which is exactly what we see, we can have 250 mile long ridges, individual ridges of eskers that go back, but that ridge was not deposited at the same time, it wasn't one long river system, or
debate about this, but, it's probably not that one, one 250 mile long.
Um, river system under a glacier. It's probably forming as the thing retreats. [00:25:30] So Chris, I'm curious. This is what I'm curious of your take on. I always, intro level Esker take is that they are much more rivers than they are glaciers. But this thing that we've just described, this process is actually I don't think I came away, after thinking about Eskers more deeply, like we have been talking about, I come away with.
Eskers are much more like glaciers than they're like rivers actually because this conveyor
belt process is so much more important.
Chris Bolhuis: yeah, the [00:26:00] formation of the Esker is intimately related to the glacier. I mean, you know, I don't know. It's a really good mix of both.
I think.
Dr. Jesse Reimink: yeah, It's like such a interesting, it makes them so interesting, such an
interesting sort of deep dive,
Chris Bolhuis: Yeah. I mean, you get the pressure because of the glacier, you know, the Esker builds from the front to the back because of the glacier, because of the deglaciation, because of the ice retreating. The Esker kind of lengthens with [00:26:30] that, which, okay that's interesting thought. I, I, I. Really hadn't ever thought about that before.
But one of the things, Jesse, that I want to talk real quickly about before moving to exploration, why all of this is important and why eskers can be very economically important, for mining companies, we should say, is the length of the, our channels, you know, with their, basically you have a short model, our channels and long model.
Our channels, so
that's self explaining.
Dr. Jesse Reimink: Let me, uh, let me interrupt and do the [00:27:00] visual, you know, painted a visual of a short version where river's flowing on top of the glacier for a long time, right near the front where there's a bunch of crevasses, it dives down and then only under the glacial bed for a little bit right near the front, the leading edge of the glacier.
That's the short model or short conduit. The long one is just a longer version of that. the river dives down to the base of the glacier way upstream. And how would that How would you get a river diving down? Like, why is that a viable
Chris Bolhuis: Well,
Dr. Jesse Reimink: guess?
Chris Bolhuis: the [00:27:30] same thing happens just further up in the glacier you maybe have crevasses there because of what's going on with the bedrock. Maybe there's a rounding of the bedrock and the glacier has to, The top part of the glacier can't expand. It's brittle. So it cracks. And so you have crevasses or moulins that develop higher up.
And so this process just is the same. It pressurizes the channel. It has to melt its way out. it's a much longer course,
because [00:28:00] of maybe the regional geology caused it to be just a longer course of action.
Dr. Jesse Reimink: So I think one thing before we talk about the exploration side again, is that I described a long Esker Corridor, like a 250 mile. It's called the Exeter Esker system. It's a really famous one in Northern Canada. That's like 250 miles long, continuous ridge of
the question is like, how do you form that with a short model?
those two kind of seem initially at odds, like a very short, a hundred meter [00:28:30] R channel doesn't really fit with that long of an Esker system, but you have to think about how this glacial flow, this progressive nature will happen as the. Glacier retreats, that river system dumping down into base of the glacier, we'll just keep reusing that pipe, that R channel will just get inherited as it goes upstream.
And so that's how you get like a continuous ridge is there's
channel at a time. And it kind of, it just evolves over time.
Chris Bolhuis: That's a little confusing. There, there can be several R [00:29:00] channels at the same time, but not for that esker. Only one R channel for that particular esker. So,
Dr. Jesse Reimink: Really quick, There's an interesting thing about that is that there's a spacing you can map. There's a relatively consistent spacing of esker system from, from one another and the place of Acosta,
kind of
kilometers away.
And the reason it has to do with how fast the glaciers melting, if you have more melt water, you're going to have esker systems that are closer spaced.
If you have less melting, they're going to be further apart. And so the spacing is [00:29:30] like such, that's such a cool
Chris Bolhuis: That's another thing that we could go into with this, right? It's like even as deep as we're going into eskers today, it's not as deep as you could go or even, it's just, it is, yeah. no, no, I was just going to say that the length of the esker is, the esker is going to go back to what created the water tower effect in the first place, the crevasse or the moulin that it's dumping into.
And then new ones will start in a different place. Right. But if you have that happening way, [00:30:00] way, way back away from the leading edge of the glacier, then you get these long model, potential systems. So
Dr. Jesse Reimink: Exactly right. So I think Chris, this leads nicely to exploration use. And these, we had talked a long time ago about, well, it's a great story for how useful eskers were in the diamond exploration days up in Canada discovering the diamond mines. I mean, it's just a, an amazing story of geological discovery.
eskers were really instrumental to that because [00:30:30] they are are pulling sediment from nearby, they're not pulling sediment from all over the place. So you can imagine how exploration can help test the long versus short conduit model. And then you can also see, I think pretty easily how eskers are really important for tracing material upstream.
It's kind of like, I don't uh, kind of like many stream chasing type things we do in geochemistry. If you, if have an anomaly somewhere, In a stream bed, you know it's coming [00:31:00] from uphill, upstream
that, that deposit, right?
There might be a
Chris Bolhuis: if you think about the stuff that gets deposited in Esker. was once glacial till. This was bedrock that got scraped. It got plucked by the glacial ice. Then it got picked up in these R channels and, was deposited then, well, I don't know, downstream somewhere, right.
part that's not, maybe not intuitive in this is that, well, then all of that stuff gets covered. With this [00:31:30] kind of uneven blanket that you talked about right at the outset of the episode. So the bedrock is now covered with this glacial drape, this glacial till material. So the esker if it has certain minerals in it, let's say, then we can trace where is the buried bedrock.
What's the source of it? if we're looking for something, let's say you alluded to diamonds and we find these tracer minerals in the Esker that, tell us that, Hey, this maybe [00:32:00] came from a Kimberlite deposit.
Then that Kimberlite deposit is now buried, right? But we can, zero us in kind of like a bullseye because we know where that came from.
We know where that glacial till came from.
Dr. Jesse Reimink: We can kind of say, okay, we see the signal, see the signal, see the see the signal. If we don't see the signal all of a sudden, we're we've gone too far, right? It's got to downstream from wherever that that stopping of the signal is. And it becomes really, really powerful, but we have to really understand this long versus short model too.
that [00:32:30] has impact because if it's actually a long R channel model, then, The till is getting mixed and sorted way downstream from where the gold deposit or The Right. as if it's a short model, till can be transported a long way still, but it kind of gets diluted quicker.
And the Esker will have a, a sort of a, a narrower window that it's exposed to of, uh,
sediment source
Chris Bolhuis: that's right. Because water is much more discriminating in what it can [00:33:00] carry. And then obviously then what it can deposit, it's way more discriminating than ices.
Dr. Jesse Reimink: the other thing, Chris, is that the esker, where is it inheriting the sediment from? The esker, or the river, is inheriting the sediment from right at the base of the glacier, which is the most locally sourced sediment in a glacial system. Sediment way up high in the ice could have from way the heck upstream, but sediment right at the base is most likely from just upstream.
It probably picked it up very close by before it gets kind of pulled up into the ice [00:33:30] sheet. So it's kind of inheriting locally sourced sediment. And this for, for me is why I got into Eskers and why we spent a bunch of time sampling Eskers, up in the Northwest Territories is because We're looking for old rocks and old rocks are very similar to a kimberlite deposit for instance.
And so we're starting to use the eskers we can look at the zircons in the eskers and sort of figure out are there old rocks just upstream because we don't really care if they're 250 miles upstream because that's going to be really [00:34:00] hard to find actually. But eskers kind of this intermediate window into what is the bedrock just upstream maybe 5, 10, 20 upstream. And remember, they also inherit this kind of narrow corridor. So eskers get this in the region we've studied, they're kind of every 10 kilometers. So you kind of get a 10 kilometer band where you can look 5, 10, 20 kilometers upstream and get a pretty good idea of what are the ages of the rocks just upstream.
and that's a ton of work to go map that, but you can look at the [00:34:30] esker sediments and kind of use this to get a rough idea.
Chris Bolhuis: I have a question for you. Did you ever in your wildest thoughts ever think that your quest to find old rocks? Would lead you back to eskers. Let's go back 15 years ago. Let's isn't that I I am just I am blown away by how Awesome, this is this is so cool that eskers aren't just cool to look at and they're not just a cool glacial [00:35:00] feature But they're also economically quite important
Dr. Jesse Reimink: a really, I agree with you, Chris.
Chris Bolhuis: This is exciting
Yeah,
Dr. Jesse Reimink: like the story we just told about how eskers form so cool, first of all, but they're also so useful other hand, it's a really, one of the, one of the, Everything's fun in geology, but this is a pretty fun juxtaposition of, uh, sort of storytelling and science and how it
Chris Bolhuis: absolutely, you know, geology isn't just good. Jesse geology is [00:35:30] good for you.
Dr. Jesse Reimink: I
Chris Bolhuis: It's
Dr. Jesse Reimink: like that. Where'd you pick that one up? That's really good
Chris Bolhuis: I just thought of it just popped into my head.
Dr. Jesse Reimink: we're gonna use that. That's a good one. We're gonna shirt Geology good for you. I like
Chris Bolhuis: I don't know. Like, I just, this is. this comes back to the heart of why we started making this podcast back in COVID is that, know, not only is geology awesome, but it's also, why should you know about this? I mean, [00:36:00] it's, it's, this fits that whole thing.
Dr. Jesse Reimink: Absolutely. You know, in those of you in Michigan or in a former glaciated terrain, you can see eskers. there's an esker somewhere. It might not be as obvious as up in Northern Canada, but you can, you can sure see them and they're cool. And even if you just Google an image of an esker, you'll get an amazing one.
They're, they're small, they're beautiful. the story behind them, the physics of how they work is just amazing. So I think eskers are. Just totally cool. And we're using them for research to look, like you said, at old [00:36:30] rocks in a way that I would have never ever guessed that this would be where we ended up
Chris Bolhuis: It's interesting. You and I read, each read a paper to get us like kind of primed to do this episode. And it was really written from the perspective of mining companies need to know as much about how eskers form they need to know as much about that process as they can, because that then affects where they start to look for what they're looking
Dr. Jesse Reimink: Exactly. And like, how do you [00:37:00] interpret your mineral data or your geochemical from esker system? Like, know, it's a really important thing. And as we're using eskers, we're starting to use eskers to sort of understand the distribution of basement ices that are exposed, underneath, you know, that might be upstream, they might be covered in till, they might be too complicated to really work on, or it takes too much effort to map 20 kilometers by 20 kilometers, whereas we can take one esker sample.
as we start to dive into this data, we're starting to realize, you know, there's always a feedback because there's a lot more to learn about eskers, then [00:37:30] maybe some of this work that we're doing could help you know, how we understand eskers so there's like always this kind of feedback where you can kind of kill two birds with one stone in a way.
So For me personally, it's an exciting avenue of research. and, and it also gets, gets the ability to learn more about Eskers, which are just
So fun.
Chris Bolhuis: So good. Hey, really good idea, Jesse. This was all you. going to give you the credit for that because I loved, I loved diving into this. was just fun.
Dr. Jesse Reimink: And [00:38:00] you know, and you were
Chris Bolhuis: it's
Dr. Jesse Reimink: seeing all this, that you saw all the component parts these Eskers work you just got to like play the clock forward for a thousand years and you will have right near where you're standing,
where you were standing.
Chris Bolhuis: trotted along the ridge of one to get a closer look at a glacier. It was driving rain and, you know, I didn't care. I put my stuff on and, and we just went for a little quick jog, maybe a half mile or so, out to see the leading edge of this glacier that had formed the
chris_1_08-24-2024_104332: [00:38:30] sesker.
Dr. Jesse Reimink: So you saw happening Ask your deposition.
right, Chris. Well, I think that's a wrap. Those of you who would like to support us, there's a couple of ways to do that. You can go to our website, planetgeocast. com. There's a support us link there and all of our old episodes with some transcripts, if those are helpful, uh, and a little bit about us, you can also download our Camp Geo mobile app.
We have A bunch of content with images. Basically Chris, the intro to geology, the first year geology class you'd take in a college level geology major is [00:39:00] there with a bunch of audio files, dozens of hours of content with bunch images that really, I don't know, geology is such a visual science, you kind of need the images to really understand some of these concepts we're talking about.
We also have some audio books for purchase there. So go to our Camp Geo app. Download it, leave us a rating and review. We really appreciate that. Send us an email, planetgeocastatgmail. com. We love getting listener questions and are always kind of putting together episodes based on some of them. And you can follow us on all the social medias at planetgeocast.
Chris Bolhuis: Cheers.
Dr. Jesse Reimink: Peace.
[00:39:30]
