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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The water flowing down through the coulee was about 400 feet. And, uh, There we go. We're looking down. Yes, there is the, we're looking at the great cataract complex right there. So the water's coming towards us during the peak of the flood.
Now picture this, as the water's coming over, the shearing force, picture this, the water's pouring over and the shearing force is so intense, it's literally quarrying or plucking the stone from the cliff face. Where the cliff is now is essentially where it was at, where it had receded to at the time the spigots from the north finally stopped.
And so what we're looking at is a fossil feature there. It's completely a fossil feature. And again, this is like 350 million cubic feet per second, which is just almost unimaginable. The water level was about the same height, the same depth as the cliffs are high. So at the peak of the flood, it wouldn't have even been a waterfall. It was just a bump in this enormous five mile wide river.
And, uh, Pretty, yeah. This is the kind of thing, when you see this firsthand, it really drives home the scale of these events we're talking about. And then if you follow this South Ryan, you can see that there's all these distributary channels. And then you get down to the mouth there at Soap Lake. South of Soap Lake, you have an outwash plane.
But when you zoom in on, you won't see it here, but put in... Ephrata, E-P-H-R-A-T-A, Ephrata Fan. Let's see, so you've got a couple of thousand square miles of this stuff that you see over on the right, which is When these floods ripped through, creating Grand Coulee, of course, all that material that was formerly part of the bedrock has been ripped out.
And at the mouth of the Coulee, there you can see, you've got hundreds of square miles of that stuff, where it's just massive swarms of boulders. So this was the basalt. that was gouged out in the creation of the coolie.
Yeah. I've, I've lost, I've taken so many tours out here to teach people how to read these landscapes. But one of the, in talking about the terms of the fundamental forces at work, when you've got water flow and let's say you've got a bedrock constriction and that water is flowing through there. And then let's say you, it opens up into a basin, right?
Well, what happens is that you've got this conservation of flow. As long as the water from the source is more or less unvarying, of course, it did vary. At one point, the water declined. Initially, if you look what's called the flood hydrograph, it's got this steep upward limb with an outburst flood, which would be similar to a dam break flood. And then it has a long tapering tail.
And that's kind of what you saw in this event here. There we go, yeah, see, there we go. The large steep limb that comes first, then you have a longer, slower taping, like second row, second from the left is exactly what I'm talking about. Yeah, you have peak discharge, and then you have this long tail that forms the recession. This is the model of an outburst flood right here.
All of these floods that we're looking at so far are outburst floods. They're coming, it's enormous, almost like a tsunami washing over the land. I mean, literally.
So when you have this peak discharge, so let's assume now the water's flowing and you're in a constricted bedrock confinement, and it's hard bedrock, so the water is less erosive than if it was softer sedimentary rock or unconsolidated sediment. Then it comes into a basin.
Well, if you were to take a transect through the basin and through the channel, the narrow channel, the same amount of water is flowing here as here. Okay. However, it's got to flow faster in the constricted channel. As it flows faster, it becomes more erosive. So when you're looking at a hydraulic event or events like we're looking at here, you have basically two forms.
You have erosion, erosion, and you have sedimentation or deposition. So when I take people through these landscapes, we follow and we go, okay, we can see erosion here now. And, you know, we can actually see, for example, if we're in a bedrock constriction, you can look up and you'll see scouring on the cliff sides.
Then it opens into a basin and boom, now you've got all of this material that's been washed out and dumped. Because as the water slows down, it loses its competency to entrain and transport sediment. So that's what we have here. Now, zoom out once, Ryan, so we can get the big picture of the whole coulee. Stop right there.
Now, do you notice if you go up to, let's see, where it says Elmira and Govan, I believe they're up on Highway 2. Come down, come down, right there. Okay, now, do you see that shaded area that is almost parallel to Highway 2? Just north, it's between upper, right there. That is called the Cooley monocline. There you go.
Now, notice that the Cooley comes in at an angle and then it intersects the monocline. Now, what's a monocline? Now we're talking tectonic forces. If you have compression, let's say, and you have bedrock, Now in the bedrock warps, you can have a down warp. You're compressing. Like if I had a piece of paper, I oftentimes will use that or, you know, that's an anticline. Okay. This is a syncline.
And then if you have a single upwarp, so it's like this, that's a monocline. So you've got compression, syncline. There we go. Let's see what we've got there. Compressional, yeah, compactional monocline formed over inactive base. And yeah, so you've got, those are all examples of monoclines, right? So you have a single upwarp.
So go back to the map, and that's we're looking at the Coulee monocline. Now, when that upwarp happens, the forces cause the bedrock to fracture. Makes sense, doesn't it? Okay, so now you've got this huge water flow coming in at an angle. Now it intersects the monocline right there. And at that point, initially, that water poured over the monocline. It was a 900-foot drop.
So you had a waterfall that was a mile wide, 900 feet high. Wow. Then it began to eat its way to the north and ate its way all the way up to the Great Notch that we already saw. Now, lower Grand Coulee, if you look below Grand Coulee City, you can follow the monocline came down, and then just below Afrata Lake there, it makes a sharp bend to the west. You see that?
Okay, so what happened is once that water hit that fractured area, area of the monocline, a large flow then exploited that weakened rock. And that became Lower Grand Coulee. And then, look, you see Monster Rock right there? That's a big old rock that's sitting out in the middle of the field right there, yeah.
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