Randall Carlson
speaker
1,469 appearances
2 recordings
2 series
first heard Apr 2025
last heard 11 Mar
Randall Carlson’s voice in public audio — every appearance, attributed to the second.
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It'll form, you'll have this glacier and right down the middle of it, you'll have this big dark streak, which is, which is the lateral mooring, meaning it's on the side. So you've got different kinds, but it's all composed of the same material, this stuff we call till.
So, um, when you look at the tail, there's the other thing that we might get into this here a little bit when we start really looking at the slides is that there's also evidence that you had tremendous high pressure floods moving under the glaciers. So, and they don't have a free surface. So the pressure on the bottom of the water flow is much more conducive to, yeah, this is good.
Look, ground moraine, recessional moraine, and moraine, that's what I was calling terminal moraine. And then you have your, your retreating glacier and right up there, you see newer till, which is being produced right at the snout of the glacier. Um, older till, outwash, um, Now, that's not quite right because the outwash would be that whole green area or the whole tan area.
That's what's referred to as the outwash plane. So you can see there, like you're driving along and it's flat. You're on the outwash plane. Then you get to this hummocky, a bunch of hills and stuff. Now you're at the mooring. And so that's where you can tell, okay, the ice sheet came here and it stopped. It didn't go any further south. It stopped. Um, let's see what we got here. Okay.
There's your kettle Lake. So a kettle Lake is when you have an ice piece of ice, a big chunk of ice it's embedded in the moraine. And then when it melts, it leaves a depression it's filled with water. So where I grew up, there were kettle lakes all over the place. Uh, in fact, our property was what I now recognize was probably a kettle Lake. Ah, look at there. Okay, we've got Drumlin.
We've got Eskers. Terminal Moraine. Out, there, yeah, Outwash Plain. So you can see there, you've got the flat area. And then when you hit those hills, boom. And there, look, see where it says came? You see those, the hills? So that was one of the things I used to wonder about. Like, you'd see this farmer's field, and out in the middle, there'd be this big rounded hill.
So growing up in a landscape where the glaciers would advance and retreat and advance and retreat multiple times, it created this whole landscape. And I remember even being a little kid, like having this sense that there was, you know, I'd be looking at things and there was like, I don't know, it's almost like there was like this hidden story in the landscape.
I mean, I remember even being seven years old one time and standing on this hill looking and just getting this overwhelming sense that there was something about the landscape. And then Later on in life, of course, I have learned all of this. So I can give you an explanation for everything you see on this picture here.
An esker, like if you've got a fracture in the ice sheet and water is flowing through that fracture and it's laden with sediment, and then when the final flow disperses, it leaves this sinuous trail of till, serpentine almost like, and that'll be an esker. Drumlins are extremely interesting. Drumlins only show up where the glaciers have been.
Because you can see if water is discharging from the glacier, like you see in this image here, as soon as it moves outside the glacier itself, it now has a free surface. So it changes the whole... pressure regime of that water flow. When it's still under the ice sheet, you know, you've got this roof, you've got this lid.
So if you've got a lot of water melting, flowing under there, it's now, it's got much greater pressure on its bottom. So what it does is it takes that ground mass, the till, which is completely chaotic and disorganized, and it begins to shape it into these aerodynamic or fluvial dynamic would be a more correct term, uh, elongated shapes that are almost like the inverted hull of a boat or a canoe.
Um, and there can be thousands of them. Um, tell you what, Ryan, if you go, uh, go to Google maps, are we still in terrain view? Uh, perfect. Okay. So now go over to Lake Ontario, New York, Western New York. You're going to see something that's pretty amazing here. Okay, you see Rochester there. Okay, before you zoom in, stop right there for a second, okay?
So you got the southern shore of Lake Ontario, and then you see the Finger Lakes? Okay, the Finger Lakes are produced by catastrophic outburst flooding. And when they were formed, it's almost certain that the margin of the ice sheet Corresponded with the northern edges, the northern end of the Finger Lakes. One thing to notice if you look at the lakes, they actually are radial. You can see they...
They converge onto an area. If you draw along the axis of those Finger Lakes, they converge on a point in a basin in Eastern Ontario. Now, yeah, now start zooming in just above. Okay, we're starting to see the Drumlin swarms. Zoom in a little more, Ryan. Go up. There we go. Zoom in on those. You see all those forms, those elongated hills? That is a drumlin swarm.
And this was formed by catastrophic subglacial, highly pressurized water flowing. And then when it discharged from the ice sheet, it carved the finger lakes.
And as soon as the water emerges from under the ice sheet, it now has this free surface and the whole pressure regime changes. And so the, the, uh, the drum lens are only going to be found where there were glaciers. And so, I mean, there's thousands of them. Yeah.
And interestingly, just like if you start scanning to the west, Brian, sorry, you're going to see, look at the orientation of the drumlins changes. Wow. So the orientation of those drumlins converges on the same spot as the finger lakes. And I think there's a reason for that. And I have a theory as to how you explain that.
Yes. But then you've got to explain, okay, why is the water discharging from a central, an epicenter? Why is it? Oh, I knew you were going to ask that question. Well, okay. So my speculation, after thinking what are all of the possible explanations, I think there's one that, Oh, sorry. One that sort of, uh, explains it better than any others. And that is, uh, a hypervelocity impact. Yeah. Okay.
Yeah. I, in fact, my studies on the Carolina bays probably preceded Chris. Okay. Okay. I have aerial photographs of the bays that I took in the early 90s when I was trying to figure out what the hell they were.
I don't know. And I'm not convinced this is an impact. But I would lean in the direction that it's the most likely explanation. And I don't think that, yeah. See, my first awareness of the bays, yeah, look at that. They're amazing. Whatever the explanation is, it's amazing. They're incredible. And so I think I first learned about the bays around 1980. I was reading a book called...
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