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Your Questions! Road Collapse in the United Kingdom (GeoShort) · PlanetGeo: The Geology Podcast

• 0:02
  SPEAKER_02: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:16
  SPEAKER_00: Chris.
• 0:17
  SPEAKER_00: Hold on.
• 0:17
  SPEAKER_00: Hold on.
• 0:18
  SPEAKER_00: Let me adjust my microphone.
• 0:19
  SPEAKER_01: Yeah, please.
• 0:20
  SPEAKER_01: Just you know you'd like it when I do that.
• 0:23
  SPEAKER_01: It's so much better.
• 0:24
  SPEAKER_01: I like it.
• 0:24
  SPEAKER_01: Click around.
• 0:25
  SPEAKER_01: Make a whole bunch of noise that I have to edit out.
• 0:27
  SPEAKER_00: Oh, okay.
• 0:27
  SPEAKER_00: You want me to?
• 0:28
  SPEAKER_01: Here.
• 0:28
  SPEAKER_00: Watch me go mute.
• 0:30
  SPEAKER_01: Oh, oh, unmute.
• 0:31
  SPEAKER_01: There we go.
• 0:32
  SPEAKER_01: It's kind of better when you're muted.
• 0:34
  SPEAKER_01: Oh man.
• 0:35
  SPEAKER_01: What's going on, Jesse?
• 0:37
  SPEAKER_01: Not much, Chris.
• 0:38
  SPEAKER_01: How you doing?
• 0:38
  SPEAKER_01: Awesome.
• 0:39
  SPEAKER_01: Sun's out.
• 0:40
  SPEAKER_02: We're getting towards spring.
• 0:41
  SPEAKER_02: It's beautiful.
• 0:42
  SPEAKER_02: Hey, these are kind of fun episodes.
• 0:44
  SPEAKER_02: We we got a really good listener question recently.
• 0:46
  SPEAKER_02: So a quick shout out to Valeria in the United Kingdom, who sent us a really interesting question about roads in southern England sort of buckling and breaking.
• 0:55
  SPEAKER_02: And there's this one particular road near the village of Lynnham in Wiltshire.
• 1:00
  SPEAKER_02: And uh it will put a link to this news article in the show notes.
• 1:03
  SPEAKER_02: But it was kind of cool and well, true, I mean crazy.
• 1:06
  SPEAKER_02: Crazy.
• 1:08
  SPEAKER_00: It looks like it got rocked by a 9.2 earthquake.
• 1:12
  SPEAKER_00: I mean, the it's absolutely destroyed.
• 1:14
  SPEAKER_00: The roads and um unbelievable.
• 1:16
  SPEAKER_02: Yeah, I should not say cool.
• 1:18
  SPEAKER_02: The road is completely messed up.
• 1:19
  SPEAKER_02: And you know, the article said there's gonna be, you know, hundreds of thousands, if not millions, of pounds worth of damage done here.
• 1:25
  SPEAKER_02: But the question was, how does this happen?
• 1:28
  SPEAKER_02: And I had no idea looking at this image, right, Chris?
• 1:33
  SPEAKER_00: Yeah, I same thing.
• 1:34
  SPEAKER_00: I immediately started looking into it.
• 1:36
  SPEAKER_00: First I read the article and start digging around.
• 1:39
  SPEAKER_00: And there isn't really a consensus yet on this.
• 1:43
  SPEAKER_00: You know, they do have uh um, what did they call it, like a geophysical company that's looking into this?
• 1:48
  SPEAKER_02: Yeah, looking into sort of why this happened.
• 1:51
  SPEAKER_02: And I think Chris, you and I both stumbled independently across an actually an AGU blog written by Dr.
• 1:56
  SPEAKER_02: Dave Pettley from the University of Sheffield in the UK.
• 1:59
  SPEAKER_02: And Dr.
• 2:01
  SPEAKER_02: Pettley was not conclusive, uh, and definitely highlighted that there's more research needed and in more surveys of this particular region, but suggested that maybe it was due to some reactivation of old solar fluction soil movements.
• 2:15
  SPEAKER_02: Right.
• 2:16
  SPEAKER_02: Which is an interesting phenomenon and one that I think requires a definition and kind of makes for a nice little geo short.
• 2:22
  SPEAKER_00: Yeah, I think too, it was associated with recent storms, right?
• 2:27
  SPEAKER_00: Like heavy, heavy precipitation.
• 2:30
  SPEAKER_00: So it makes sense.
• 2:32
  SPEAKER_00: Um yeah, let's talk about what solar fluction is because this is kind of a it leads to really interesting patterned ground and yeah.
• 2:40
  SPEAKER_02: Yeah, so solar fluction, it's S O L I F L U C T I O N.
• 2:46
  SPEAKER_02: So sola fluction.
• 2:47
  SPEAKER_02: So l fluction.
• 2:48
  SPEAKER_02: Yeah, right.
• 2:48
  SPEAKER_02: So it's kind of a hard word to to hear and know how to spell it.
• 2:52
  SPEAKER_02: But um, yeah, sorry, Chris, go ahead.
• 2:54
  SPEAKER_00: This is something that you can get in like you, I think you come across this in the Northwest Territories, don't you?
• 3:00
  SPEAKER_00: Solar fluction.
• 3:01
  SPEAKER_00: You see this probably a lot, right?
• 3:03
  SPEAKER_02: Absolutely.
• 3:04
  SPEAKER_00: I've seen it up in um tundra areas, uh, like at high up in the Rockies.
• 3:09
  SPEAKER_00: Um, you get some solar fluction, this kind of patterned ground.
• 3:13
  SPEAKER_00: And you have to have something first in order for solar fluxion, like in the proper sense.
• 3:19
  SPEAKER_00: I don't think this is what happened in the UK, but where you have what's called permafrost, this permanently frozen ground beneath the surface.
• 3:28
  SPEAKER_00: You know, that's going to be up in really like the northern territories or really, really high up in the mountains, this kind of permanently frozen ground.
• 3:37
  SPEAKER_02: Yeah, high latitude or high elevations.
• 3:38
  SPEAKER_02: And the other thing you need, you need so you need a permafrost layer that does not melt, and the soil can't move, and then you need a layer of saturated, typically water-saturated soil, on top of that permafrost.
• 3:50
  SPEAKER_02: And then that water saturated soil at the top level can flow.
• 3:54
  SPEAKER_02: And up in the Northwest Territories of Ridework, you get maybe six to eight feet of soil that is above permafrost.
• 4:00
  SPEAKER_02: So this is sort of the soil that melts during the summer and then freezes during the winter, but it's melted for some time of the year.
• 4:07
  SPEAKER_02: And because there's permafrost below, that's an impermeable layer.
• 4:10
  SPEAKER_02: The water can't make its way into the permafrost.
• 4:12
  SPEAKER_02: So instead it saturates that soil.
• 4:14
  SPEAKER_02: And this creates this really cool pattern where the f the soil just sort of flows like molasses downhill.
• 4:20
  SPEAKER_02: I don't know, that's the way I sort of think of it.
• 4:23
  SPEAKER_00: And if you No, that's a that's a good description of it.
• 4:25
  SPEAKER_00: Yeah, it's I you think I always solar fluction.
• 4:28
  SPEAKER_00: I always uh say this like think of it as solar flows and you know that's that's a good one.
• 4:33
  SPEAKER_02: That's a good one.
• 4:33
  SPEAKER_02: Soil flow, yeah, yeah.
• 4:34
  SPEAKER_02: Soil flowing, right?
• 4:35
  SPEAKER_02: It's soil flowing downhill.
• 4:37
  SPEAKER_00: It is, and like you can see the flow had happened a long time ago.
• 4:42
  SPEAKER_00: It looks like the ground was just kind of oozing and this kind of really thick, viscous material.
• 4:48
  SPEAKER_00: Um, and like you hit it right on.
• 4:51
  SPEAKER_00: It has to do with that permafrost because that permafrost allows the upper part of thawed surface to get saturated because it can't seep into that permafrost.
• 5:01
  SPEAKER_00: And yeah, it's uh pretty cool thing to see when it's in the mountains and away from roads and things like that.
• 5:09
  SPEAKER_00: But I think in the case of the UK here, right, they had these heavy precipitation and the ground just got saturated, right?
• 5:17
  SPEAKER_00: That's what happened.
• 5:20
  SPEAKER_02: It's an interesting point, and I think we have to highlight that we don't exactly know in this instance if this is exactly what's happening.
• 5:26
  SPEAKER_02: It's one sort of idea out there.
• 5:27
  SPEAKER_02: But in southern England, where this occurred, there is no permafrost.
• 5:31
  SPEAKER_02: So, right, so it's not actually solafluction doing it, it would be reactivation of old solar fluction like layers, basically.
• 5:38
  SPEAKER_02: So this was a really kind of an interesting point, is that there's no permafrost there.
• 5:43
  SPEAKER_02: So it's not solar fluction like we think of it, but it's saturated soil that's kind of moving because solar fluction used to be there.
• 5:50
  SPEAKER_02: In the Little Ice Age, back you know, several hundred thousands of years ago, there was permafrost in southern England, and there was solar flexion going on, and you can map out these boundaries, and that stuff can be reactivated by heavy rainfall.
• 6:02
  SPEAKER_02: So it's a really interesting thing that you need to.
• 6:05
  SPEAKER_02: I'd never really thought about this in detail, that you really need to map out the soil horizons and the ancient soil movements in an area to figure out how susceptible it is to sort of mass wasting, what we call these processes that are moving soil.
• 6:19
  SPEAKER_00: That's right.
• 6:20
  SPEAKER_00: I want to ask you though, what do you mean by reactivation of an old sol deflection thing?
• 6:26
  SPEAKER_00: Why is that important?
• 6:27
  SPEAKER_02: Well, I think it I guess it would be important.
• 6:29
  SPEAKER_02: I'm not a soil expert.
• 6:30
  SPEAKER_02: So I th but I th I'm imagining that it would be important that if you you have this really complicated soil structure.
• 6:35
  SPEAKER_00: You just got irritated with me for asking this question, didn't you?
• 6:38
  SPEAKER_00: You just you got a little short of me right there.
• 6:39
  SPEAKER_00: You snapped at me.
• 6:40
  SPEAKER_00: Oh, did I?
• 6:41
  SPEAKER_02: I'm not a soil expert.
• 6:42
  SPEAKER_02: I am, I am not a soil expert.
• 6:44
  SPEAKER_02: I just no, I wanted to I wanted to say because I clarify, because you know, I this is not speaking from uh uh an area of expertise, but you generate with solar fluction, you can generate these really strange soil boundaries that are not stable.
• 6:57
  SPEAKER_02: So they can become unstable if you add a lot of water into it.
• 7:00
  SPEAKER_02: Just like landslides in the western US, Chris, I suppose, right?
• 7:04
  SPEAKER_02: If you add a lot of water to a really kind of slippery, steeply dipping rock layer, that can break off and fall into a big reservoir or something like that and create a landslide.
• 7:15
  SPEAKER_00: That's right.
• 7:15
  SPEAKER_02: It's the same sort of thing on a smaller scale.
• 7:17
  SPEAKER_00: You think about it in terms like a from a mass wasting standpoint, water really does three things.
• 7:22
  SPEAKER_00: If you add a lot of water to the regolith to this like outer skin of the earth, it makes the stuff really heavy, it can make clay slippery, and it can also, if it saturates it, it can make everything runny.
• 7:37
  SPEAKER_02: Right.
• 7:38
  SPEAKER_02: That's a great point.
• 7:39
  SPEAKER_00: It's kind of like you know, if you take um if you're walking along a beach area where you have sand, uh take moist sand and you can make a ball out of it, right?
• 7:48
  SPEAKER_00: But if you add more water to it, now it just turns into this it oozes between your fingers as you squeeze it and try to make it, it just won't make a ball.
• 7:56
  SPEAKER_00: It just totally loses its internal cohesion.
• 7:58
  SPEAKER_00: And so that's probably the at least that's what they're thinking happened with this in this case.
• 8:05
  SPEAKER_02: The other thing that's interesting about this, Chris, I think is that it shows how powerful small soil movements can be.
• 8:12
  SPEAKER_02: I mean, I always think of it, you know, soil creep is another mass-wasting phenomenon, which we don't need to go into.
• 8:18
  SPEAKER_02: But when I'm walking, uh, you know, I lived in DC for a while, you came and visited me in DC, and we were walking along streets, right, with old stone boundaries on the streets.
• 8:27
  SPEAKER_02: So you got the hill, the house is built up on the hill, and there's a stone uh wall that is between the yard and the sidewalk, right?
• 8:35
  SPEAKER_02: And that old stone wall is like totally tilted into the sidewalk, right?
• 8:39
  SPEAKER_02: Like it is leaning massively.
• 8:41
  SPEAKER_00: You see this all the time.
• 8:42
  SPEAKER_00: You know, seriously, people what happens is like when people build retaining walls, which is essentially what you're describing here, whether they build it for a bike path or terracing their yard or what doesn't matter.
• 8:54
  SPEAKER_00: You build a retaining wall, you're holding back that sediment, right?
• 8:58
  SPEAKER_00: In most of the cases, you had to remove a bunch of sediment to build that wall.
• 9:03
  SPEAKER_00: And you have to give the water a place to go, right?
• 9:07
  SPEAKER_00: Because water, if it flows through the soil and it encounters that wall, it's just gonna pile up behind the wall, and that's what's causing the rock to lean into where you don't want it to go.
• 9:20
  SPEAKER_02: Exactly, especially these like freeze-throw cycles.
• 9:22
  SPEAKER_02: I mean, it just kind of shows the power of a whole bunch of little tiny sand grains or little tiny dirt particles.
• 9:28
  SPEAKER_02: If they all move in the same direction slowly, that's a really powerful force and really, really hard to stop.
• 9:34
  SPEAKER_02: Like we have a hard time engineering around this sort of soil creep process.
• 9:37
  SPEAKER_02: It's it's really kind of um, I think it's kind of cool.
• 9:40
  SPEAKER_02: It can be very damaging, uh, but but quite cool.
• 9:43
  SPEAKER_00: Do you remember ever walking along the dunes that we have all over you know the Lake Michigan shorelines and and oh yeah, totally.
• 9:52
  SPEAKER_00: You can see great examples of soil creep along those dunes because they're steep slope, right?
• 9:58
  SPEAKER_00: And so the sand, when it freezes, gets lifted perpendicular to the slope, and then it thaws, and the sand gets let down straight down, then it you know keeps on doing this zigzag motion, right?
• 10:09
  SPEAKER_00: Well, it affects the trees, and so right on the slope, the trees are like they're curved, they're curved down slope, but then the tree and its quest for light straightens itself back out.
• 10:23
  SPEAKER_00: So whenever you see that really steeply curved trunk of a tree down a slope, that's a sure sign of soil creep right there.
• 10:32
  SPEAKER_02: Yeah, it's such an amazing process.
• 10:33
  SPEAKER_02: So powerful.
• 10:34
  SPEAKER_02: Yeah, so powerful.
• 10:36
  SPEAKER_02: So I think I mean, I don't know, there's no answer.
• 10:39
  SPEAKER_02: Valeria, that's our best answer.
• 10:41
  SPEAKER_02: There's no clear answer to this particular example that you highlighted to us, but I think it's a good possibility.
• 10:48
  SPEAKER_02: And so it sort of sh highlights how powerful soil and water and soil can be and and how damaging it can potentially be if not properly mitigated.
• 10:58
  SPEAKER_00: And also we really appreciate the question.
• 11:00
  SPEAKER_02: Oh, totally.
• 11:00
  SPEAKER_02: Fun for us to look into.
• 11:02
  SPEAKER_02: Yes, and in your email, you promised several more, so we expect to see those coming our way.
• 11:07
  SPEAKER_02: That's right.
• 11:07
  SPEAKER_02: That's right.
• 11:08
  SPEAKER_02: All right, hey, we always appreciate listener questions.
• 11:10
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• 11:12
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• 11:15
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• 11:23
  SPEAKER_02: What?
• 11:24
  SPEAKER_02: All right, I mean, you're just staring at me.
• 11:26
  SPEAKER_02: Come on, Chris.
• 11:26
  SPEAKER_02: What's going on?
• 11:29
  SPEAKER_00: You just stopped talking all of a sudden.
• 11:31
  SPEAKER_00: I don't know.
• 11:31
  SPEAKER_00: I don't know.
• 11:32
  SPEAKER_00: You didn't give me any cue or anything.
• 11:33
  SPEAKER_00: What do you got me to say?
• 11:34
  SPEAKER_00: Yeah.
• 11:34
  SPEAKER_00: Really good job, Jesse.
• 11:35
  SPEAKER_00: Yeah, thank you.
• 11:36
  SPEAKER_00: That's what I'm saying.
• 11:36
  SPEAKER_00: You're awesome.
• 11:36
  SPEAKER_00: A lot of really good, really nice work, Jesse.
• 11:38
  SPEAKER_00: I don't get enough compliments around here, I don't think.
• 11:42
  SPEAKER_00: They're earned, they're not given.
• 11:44
  SPEAKER_02: That's true, that's true.
• 11:45
  SPEAKER_02: All right, that's a wrap.
• 11:47
  SPEAKER_02: See you next week.
• 11:48
  SPEAKER_00: See ya.