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Moving Boulders - The Geology of Fieldstones · PlanetGeo: The Geology Podcast

• 0:02
  SPEAKER_01: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:13
  SPEAKER_01: The lights on.
• 0:14
  SPEAKER_01: Blinking red.
• 0:15
  SPEAKER_01: So nervous.
• 0:18
  SPEAKER_01: Got my planet view hat on.
• 0:20
  SPEAKER_01: How do you like it?
• 0:21
  SPEAKER_00: I know.
• 0:21
  SPEAKER_00: I'm mad.
• 0:22
  SPEAKER_00: When is my merch gonna show up?
• 0:24
  SPEAKER_00: The White Glove service hasn't uh brought it to your door yet.
• 0:27
  SPEAKER_00: Man, what's up with that?
• 0:28
  SPEAKER_00: I was gonna surprise you with uh one size too small shirt, so my pipes pop.
• 0:34
  SPEAKER_00: Okay.
• 0:35
  SPEAKER_00: And and a hat.
• 0:37
  SPEAKER_01: I can't wait.
• 0:38
  SPEAKER_01: We're gonna turn the camera off for that episode when that happens.
• 0:42
  SPEAKER_01: Um yeah, man.
• 0:44
  SPEAKER_01: Got the merch, got the merch on.
• 0:45
  SPEAKER_01: You can get your own planetgeocast.com.
• 0:47
  SPEAKER_01: There's a merch page there.
• 0:49
  SPEAKER_01: Um, you got a text from your mom.
• 0:51
  SPEAKER_01: Did you get another word of the day from Joyce?
• 0:53
  SPEAKER_01: I did.
• 0:53
  SPEAKER_00: I did.
• 0:54
  SPEAKER_00: And I sent it right to you.
• 0:55
  SPEAKER_00: What was the word?
• 0:56
  SPEAKER_00: Oh, hold on now.
• 0:57
  SPEAKER_00: You're putting me on the spot.
• 0:58
  SPEAKER_00: I can't I can't remember.
• 0:59
  SPEAKER_00: She has a lot of things that she says.
• 1:01
  SPEAKER_00: But oh, I don't understand this.
• 1:04
  SPEAKER_00: Trucker.
• 1:05
  SPEAKER_00: Why is that the word of the day?
• 1:06
  SPEAKER_01: You know what?
• 1:07
  SPEAKER_01: That's a great question.
• 1:08
  SPEAKER_01: Why the heck is trucker the word?
• 1:11
  SPEAKER_01: We Chris, you and I, we say a lot of interesting words every podcast.
• 1:15
  SPEAKER_01: Yes, and she picks up Trucker.
• 1:17
  SPEAKER_01: Was it because we used trucker hat?
• 1:18
  SPEAKER_01: Because I said it's a trucker hat, right?
• 1:20
  SPEAKER_00: I think that's yeah.
• 1:21
  SPEAKER_01: That's not an interesting word, Joyce.
• 1:23
  SPEAKER_01: No, Joyce.
• 1:24
  SPEAKER_01: We must have said something better than that in that episode.
• 1:27
  SPEAKER_00: Hey, somewhere in her subconscious, she's hearing us say Joyce, and she's gonna wake up.
• 1:32
  SPEAKER_01: She's gonna just woke her from her slumber of listening to this episode.
• 1:38
  SPEAKER_00: She's we're gradually nudging her to uh be an alert.
• 1:42
  SPEAKER_01: Think about find a better word out of this episode.
• 1:45
  SPEAKER_01: Uh we have some pretty good words in this episode, Chris.
• 1:47
  SPEAKER_01: Don't you agree?
• 1:48
  SPEAKER_01: This is a fun word episode.
• 1:50
  SPEAKER_00: I think so.
• 1:51
  SPEAKER_00: Uh yeah, I absolutely do.
• 1:53
  SPEAKER_00: In fact, I called you one.
• 1:54
  SPEAKER_00: Just uh one of the words.
• 1:55
  SPEAKER_01: Yeah, well, I called you.
• 1:56
  SPEAKER_01: Yeah, some of them you might be able to call your friends uh in a joking manner.
• 2:00
  SPEAKER_01: There's an origin story to this episode.
• 2:02
  SPEAKER_01: The origin story here is I got a text from my uh uh an individual I call my uncle.
• 2:09
  SPEAKER_01: He's not really my uncle, but you know, close family friend, uncle, who texted me and said, I don't really get texts from my uncle, but I got a text from him, and he said, question I know from growing up in farming that boulders move up in the fields.
• 2:25
  SPEAKER_01: Do they move up in lake bottoms?
• 2:28
  SPEAKER_01: I thought, wow, that's a really interesting question, and that would probably do a pretty good job as a podcast episode.
• 2:35
  SPEAKER_01: But then we kind of went in we went into a deep dive on this one, Chris.
• 2:39
  SPEAKER_01: And it's like at first we're like, okay, that's a pretty short episode, that's really easy to cover.
• 2:43
  SPEAKER_01: Frostieving, pretty simple.
• 2:45
  SPEAKER_01: Uh it's actually more complicated.
• 2:46
  SPEAKER_01: I mean, I learned something putting together this episode for sure.
• 2:50
  SPEAKER_00: I agree.
• 2:50
  SPEAKER_00: I have a thought though.
• 2:51
  SPEAKER_00: I was wondering, since I'm an old family friend, can you maybe call me your uncle?
• 2:58
  SPEAKER_02: Absolutely not.
• 2:59
  SPEAKER_02: Can I be Uncle Chris?
• 3:00
  SPEAKER_01: Absolutely not Uncle Chris.
• 3:02
  SPEAKER_01: Why not?
• 3:03
  SPEAKER_00: I feel like I've earned them.
• 3:04
  SPEAKER_01: No, you haven't.
• 3:05
  SPEAKER_01: I've already got an Uncle Chris.
• 3:06
  SPEAKER_01: Thanks.
• 3:07
  SPEAKER_01: I don't need another.
• 3:08
  SPEAKER_01: Yeah.
• 3:09
  SPEAKER_01: You do Uncle Chris.
• 3:10
  SPEAKER_01: Yeah, my mother's side.
• 3:11
  SPEAKER_01: No, I I'm not gonna call you Uncle Chris.
• 3:13
  SPEAKER_01: Once?
• 3:14
  SPEAKER_01: Just one time.
• 3:15
  SPEAKER_01: Not ever, probably.
• 3:17
  SPEAKER_01: I'll call you other names, but not Uncle Chris.
• 3:20
  SPEAKER_01: Okay, so this was a fun episode.
• 3:22
  SPEAKER_01: People might have heard the term frost heaving.
• 3:25
  SPEAKER_01: Chris, you must cover frost heaving in G SI1, in Earth Science, even ninth grade earth science.
• 3:32
  SPEAKER_00: Oh, sure.
• 3:32
  SPEAKER_00: Absolutely.
• 3:33
  SPEAKER_00: It's such an important thing.
• 3:34
  SPEAKER_00: I don't like the term frost heaving, though, or frost wedging.
• 3:37
  SPEAKER_00: I don't like that.
• 3:38
  SPEAKER_00: So I don't use it actually.
• 3:40
  SPEAKER_00: I use the term ice wedging or ice heaving.
• 3:43
  SPEAKER_00: Yeah.
• 3:44
  SPEAKER_00: I just don't, you know, I think that's a more appropriate term, ice wedging versus frost wedging.
• 3:50
  SPEAKER_01: And it actually fits better with the sort of model.
• 3:52
  SPEAKER_01: But if we frame this, and I think people listening to this have probably heard this or seen this.
• 3:57
  SPEAKER_01: If you're driving around, you drive past farms, you'll usually see, at least in the northern latitudes where I live in Pennsylvania, up in Michigan for sure, you see boulders near the fields, like a big pile of boulders somewhere, right?
• 4:09
  SPEAKER_01: And this is very common.
• 4:10
  SPEAKER_01: This happens in farmers' fields, especially in farmers' fields.
• 4:14
  SPEAKER_01: It happens naturally, but it happens much faster in farmed fields because of the tilling process.
• 4:18
  SPEAKER_01: We'll talk about that.
• 4:19
  SPEAKER_01: But this is obviously a big problem.
• 4:21
  SPEAKER_01: A bunch of boulders or even little stones, damage equipment, decreases like the soil surface area over a big plot.
• 4:27
  SPEAKER_01: Like this is a big, a big, big problem.
• 4:29
  SPEAKER_01: They make devices that you can use to pick up all the boulders and then you pile them somewhere.
• 4:34
  SPEAKER_01: As geologists, Chris, have you ever just rocked up to a farmer's field and been like, hey, I see a pile of stones.
• 4:38
  SPEAKER_01: Can I take some?
• 4:39
  SPEAKER_00: Absolutely.
• 4:40
  SPEAKER_00: I have, but here's the thing: the point I want to make is that now they're selling them and for a lot of money, Jesse.
• 4:48
  SPEAKER_00: It's amazing.
• 4:48
  SPEAKER_00: I was just walking past, I was taking a dog for a walk, and they had uh this farmer had on a flatbed semi-truck all these boulders that he had taken from his farm field and placed on there, and he had price tags on everyone.
• 5:01
  SPEAKER_00: Oh, really?
• 5:02
  SPEAKER_00: On every one.
• 5:02
  SPEAKER_00: Wow, amazing.
• 5:04
  SPEAKER_00: Yes, and they were priced according to how pretty he thought they were.
• 5:08
  SPEAKER_00: And there were rocks that were maybe the size of two beach balls, if you will, that were like$750 a piece.
• 5:15
  SPEAKER_00: These were not cheap.
• 5:16
  SPEAKER_01: Yeah, well, this is the same.
• 5:17
  SPEAKER_01: I mean, it's amazing to me.
• 5:19
  SPEAKER_01: We were up in New Hampshire too, and it's the same thing.
• 5:21
  SPEAKER_01: I mean, rocks are everywhere in New Hampshire.
• 5:23
  SPEAKER_01: The rocks in Michigan, because it's just glacial kitty litter as you describe it, you get really beautiful rocks.
• 5:29
  SPEAKER_01: I mean, there are some of those rocks that I've seen in Farmersville's that I would pay a lot for because they are spectacular rocks, and they're big and beautiful, and people put them in their landscaping or all sorts of things.
• 5:40
  SPEAKER_01: So you can't just take them because there is value there, and I've noticed the same thing, you know.
• 5:44
  SPEAKER_01: Like maybe, maybe a while back people would just be like, Yeah, sure, get them out of my way.
• 5:48
  SPEAKER_01: But now it's like, oh no, you know, that's worth something to people.
• 5:51
  SPEAKER_01: And actually, people pay a lot to do to kind of put it in their landscaping, typically.
• 5:55
  SPEAKER_00: Yeah.
• 5:55
  SPEAKER_00: So I was talking to the farmer, and and he sells them also to landscapers.
• 6:00
  SPEAKER_00: Yeah, absolutely.
• 6:01
  SPEAKER_01: Because who doesn't want a big, beautiful rock in your yard, in your landscaping?
• 6:04
  SPEAKER_01: Everybody wants that.
• 6:06
  SPEAKER_00: They they are really pretty.
• 6:07
  SPEAKER_00: I mean, he had some just stunning rocks out there, you know.
• 6:10
  SPEAKER_00: Nice is you and I are a fan of nice.
• 6:12
  SPEAKER_00: Oh, yeah.
• 6:13
  SPEAKER_00: None of them struck your fancy.
• 6:14
  SPEAKER_00: I don't buy rocks.
• 6:15
  SPEAKER_00: I don't buy rocks.
• 6:16
  SPEAKER_00: Okay, there we go.
• 6:16
  SPEAKER_00: Because I go get my own.
• 6:17
  SPEAKER_00: So exactly.
• 6:19
  SPEAKER_01: Okay.
• 6:19
  SPEAKER_01: So that's the state.
• 6:20
  SPEAKER_01: We're talking about why this happens and specifically in farmers' fields.
• 6:24
  SPEAKER_01: Like, why is this happening?
• 6:25
  SPEAKER_01: Why do rocks continually come up?
• 6:27
  SPEAKER_01: Why do you have to keep removing the rocks year after year after year?
• 6:30
  SPEAKER_01: It's a good question.
• 6:32
  SPEAKER_01: We're gonna like tease a couple different threads here as to why this happened, but yes, it kind of happens around frost heaving is you you did a pretty good job here, Jesse.
• 6:42
  SPEAKER_00: You came up with uh a couple of analogies.
• 6:45
  SPEAKER_00: I think that they make sense.
• 6:47
  SPEAKER_00: Uh I guess maybe I don't know.
• 6:49
  SPEAKER_00: I have a question, but why don't you go ahead?
• 6:52
  SPEAKER_00: Because it's yours.
• 6:52
  SPEAKER_00: Why don't you throw your analogies out and then I have a question about that?
• 6:57
  SPEAKER_00: I'm not like I'm not setting up.
• 6:58
  SPEAKER_01: You mean say the analogies, not like get rid of them because they're terrible.
• 7:02
  SPEAKER_01: Like lose the analogies.
• 7:04
  SPEAKER_00: No, I like them actually.
• 7:04
  SPEAKER_00: They're good, but I have a question though about applicability.
• 7:08
  SPEAKER_01: Sure.
• 7:09
  SPEAKER_01: Okay.
• 7:09
  SPEAKER_01: So the first the first way we're gonna talk about this, we're generally we're gonna talk about how does big stuff move to the top?
• 7:16
  SPEAKER_01: Like that's uh bit counterintuitive in many ways, but also we've seen this in our daily lives.
• 7:22
  SPEAKER_01: There's a couple main mechanisms, three main mechanisms by which you can get big particles move up to the top, and that's what's happening in a farmer's field.
• 7:30
  SPEAKER_01: The first one isn't really applicable to the farmer's field, but it's applicable elsewhere in geology, is by shaking.
• 7:36
  SPEAKER_01: And so, Chris, I want you to sit there, Chris Boris, and imagine your big giant vat of Skittles that you have.
• 7:44
  SPEAKER_01: I mean, Chris's dream.
• 7:46
  SPEAKER_00: It's got to be a bag of Doritos, don't you think?
• 7:47
  SPEAKER_01: Okay, yeah, you're right.
• 7:48
  SPEAKER_01: Okay, Doritos is better.
• 7:49
  SPEAKER_01: All right, a big bag of Doritos.
• 7:51
  SPEAKER_01: Perfect.
• 7:51
  SPEAKER_01: All right, good, fair, fair point.
• 7:53
  SPEAKER_01: A big bag of Doritos that you bought at the grocery store, a big family size, party-sized one.
• 7:57
  SPEAKER_01: Bought at the grocery store, you chucked it in the back of your vehicle, you brought it home, you smashed it in the cupboard, and now you pull it out, and now you're about to eat it.
• 8:05
  SPEAKER_01: What's at the top?
• 8:06
  SPEAKER_01: And the same thing goes for cereal boxes, like what's at the top?
• 8:09
  SPEAKER_01: The first half of it is big, beautiful Doritos chips, right?
• 8:14
  SPEAKER_01: Yes, absolutely.
• 8:15
  SPEAKER_00: The big full chips, the big full ones.
• 8:17
  SPEAKER_01: We could get a lot of salsa on that one, you know, like all the good stuff, right?
• 8:21
  SPEAKER_00: The ones you pick out of the bag and you look them over, and you which side do you want to like have on your tongue?
• 8:26
  SPEAKER_00: The one with all the like stuff on it, right?
• 8:29
  SPEAKER_00: This is amazing insight into Chris Balless's Dorito habits.
• 8:33
  SPEAKER_01: I mean, my goodness, inspect which one's the best.
• 8:37
  SPEAKER_01: You don't do that?
• 8:38
  SPEAKER_01: I haven't had a Dorito in kind of a while, I bet.
• 8:42
  SPEAKER_01: So yeah, I haven't either.
• 8:44
  SPEAKER_00: I haven't had a Dorito in 12 hours.
• 8:46
  SPEAKER_00: 12 hours.
• 8:48
  SPEAKER_00: I'm into chili cheese now.
• 8:50
  SPEAKER_01: Yeah, the the chili like cheese, my goodness.
• 8:53
  SPEAKER_01: Okay, yeah.
• 8:53
  SPEAKER_01: All right, so big bag of family party-sized chili cheese.
• 8:57
  SPEAKER_01: Now, what Chris, what happens when you get to the middle, the bottom third of that bag, even?
• 9:01
  SPEAKER_00: Then you get some broken ones, right?
• 9:03
  SPEAKER_00: And then they just get smaller and smaller and smaller, which I like because when you get down there, you know, then that stuff gets all on your fingers.
• 9:11
  SPEAKER_01: Oh, yeah, okay, yeah.
• 9:12
  SPEAKER_00: I mean, but they get the chips get like smaller and smaller.
• 9:16
  SPEAKER_00: You get crumbs down at the very very bottom of it.
• 9:19
  SPEAKER_00: Absolutely.
• 9:19
  SPEAKER_00: Okay, and there's a reason for that.
• 9:21
  SPEAKER_01: That's what you're getting to.
• 9:22
  SPEAKER_01: That's exactly right.
• 9:23
  SPEAKER_01: There's a reason for this.
• 9:24
  SPEAKER_01: And the the classic, many classic examples of this, but it's like, okay, you could do this with an uh a jar of mixed nuts, you know, you get the big ones rise to the top as you shake them side to side and up and down.
• 9:34
  SPEAKER_01: The big ones always kind of rise to the top when you shake it.
• 9:37
  SPEAKER_01: So during shaking, what's going on?
• 9:39
  SPEAKER_01: Well, what's going on is when you shake stuff, the whole kind of package, you can imagine all the particles are kind of lifted up in the air during the shaking, which means that small gaps form between all the particles.
• 9:50
  SPEAKER_01: Now, as they fall back down, the small particles more easily fill in the small gaps.
• 9:57
  SPEAKER_01: And there are very few big gaps that get formed.
• 10:00
  SPEAKER_01: They are there, but they're very few.
• 10:02
  SPEAKER_01: So there's actually very few places for the big particles to go when the whole package of particles falls back down.
• 10:09
  SPEAKER_01: So if you do this enough, up and down, up and down, up and down, up and down, the little ones they find a nice home down lower.
• 10:16
  SPEAKER_01: They settle down in because there's a lot of small holes for them.
• 10:19
  SPEAKER_01: But the big ones don't find any home and kind of get filtered up to the top.
• 10:22
  SPEAKER_01: They're kind of the weird ones that get left behind, basically.
• 10:25
  SPEAKER_01: So that's the process.
• 10:27
  SPEAKER_01: It's a really simple process, but that's what's happening, why big stuff moves up when you shake it.
• 10:31
  SPEAKER_00: You get the same thing with cereal boxes like Raisin Brand does this, you know, the raisins kind of sink to the bottom.
• 10:35
  SPEAKER_00: So you gotta shake it up because everybody wants the raisins with, you know, you want an even distribution, right?
• 10:40
  SPEAKER_01: Exactly.
• 10:40
  SPEAKER_01: And we think that the raisins are heavy, but the raisins are small, is the reason they sink to the bottom.
• 10:44
  SPEAKER_01: The raisins are that's right.
• 10:45
  SPEAKER_00: I mean, heavy has something to do with the that's why this is counterintuitive, because the big rocks are heavy, right?
• 10:50
  SPEAKER_00: And so you have the same thing going on.
• 10:53
  SPEAKER_00: But here's my question, Jesse.
• 10:55
  SPEAKER_00: Where does this kind of thing happen then from a tectonic or geologic setting?
• 11:00
  SPEAKER_01: Ooh, where does shaking happen?
• 11:02
  SPEAKER_01: Yes.
• 11:03
  SPEAKER_01: Like, you know, earthquakes can do a lot of shaking.
• 11:06
  SPEAKER_01: So you can have these things kind of pushed up.
• 11:08
  SPEAKER_01: It does happen a little bit in like a field, in a farmer's field, for instance.
• 11:13
  SPEAKER_01: And we've talked about this before.
• 11:14
  SPEAKER_01: It's very similar to the sort of frost wedging.
• 11:16
  SPEAKER_01: It's the freeze thaw cycle.
• 11:18
  SPEAKER_01: The freeze thaw can do a little bit of lifting up and then it comes back down and lifts up and comes back down, lift up, come back down.
• 11:25
  SPEAKER_01: So that's it's like very slow shaking.
• 11:27
  SPEAKER_01: That is a force that can get big stuff to the top, but that's not fast enough.
• 11:31
  SPEAKER_00: And every freeze thaw, right?
• 11:32
  SPEAKER_00: Every freeze thaw, little ones.
• 11:34
  SPEAKER_00: The little stuff is gonna settle preferentially down to the bottom, thereby leaving the big stuff on higher up.
• 11:40
  SPEAKER_01: It's exactly Chris.
• 11:41
  SPEAKER_01: We talked about this with soil creep before, where you know, freezes and it gets pushed out away from the hill, like kind of angled out from the hill, and then when it thaws, it falls straight down.
• 11:50
  SPEAKER_01: So it goes out and down, out and down, out and down.
• 11:52
  SPEAKER_01: Here we're kind of shaking the it's kind of a a little bit like a shaking pattern.
• 11:56
  SPEAKER_01: But that's not really the process that's happening for farmers' fields, because you know, the freeze thaw cycles, there's a bunch of them in a typical Michigan winter, but not enough to move a big boulder all the way up to the top of the soil.
• 12:08
  SPEAKER_01: Like it's not going to move it that much during this process.
• 12:11
  SPEAKER_01: So there's got to be something more important that's happening in Michigan.
• 12:15
  SPEAKER_00: And that leads us to ice wedging or ice heaving.
• 12:19
  SPEAKER_00: Okay.
• 12:19
  SPEAKER_00: This is what everybody would come to.
• 12:22
  SPEAKER_00: This is such an important mechanical weathering process, right?
• 12:26
  SPEAKER_00: In the mountains and really anywhere where you get a cycle of freeze-thaw, freeze-thaw, freeze-thaw.
• 12:33
  SPEAKER_00: Because when water freezes, it expands by 9%.
• 12:36
  SPEAKER_00: That's the heaving part, and then it melts, and that water then seeps deeper down, and so on and so on.
• 12:44
  SPEAKER_00: And that can happen in a farmer's field, right?
• 12:46
  SPEAKER_00: Let's think about this a second.
• 12:48
  SPEAKER_00: You know, so you have water that's sitting in the pore space in this glacial kitty litter till in the soil that's got these boulders in it, and you get these freezed off cycles.
• 13:00
  SPEAKER_00: So the freezing is going to heave everything a little bit up.
• 13:04
  SPEAKER_00: Right.
• 13:04
  SPEAKER_00: And then when it thaws, the water's going to melt and it's going to also add that melting.
• 13:09
  SPEAKER_00: Not only is the water going to seep down further, but so are the small particles.
• 13:13
  SPEAKER_00: They're going to just go with it.
• 13:14
  SPEAKER_01: Yeah.
• 13:15
  SPEAKER_01: Right.
• 13:15
  SPEAKER_01: Exactly.
• 13:16
  SPEAKER_00: And so you kind of get the net effect is this like very slow but monotonous kind of heaving up toward closer toward the surface.
• 13:25
  SPEAKER_01: That's right.
• 13:26
  SPEAKER_01: And that's very similar to the shaking.
• 13:27
  SPEAKER_01: It's slow shaking, what we kind of talked about before.
• 13:30
  SPEAKER_01: The question is, can this drive big boulders very high?
• 13:33
  SPEAKER_01: Or if you've seen this, I mean, I had this in the road right outside of our old house, had a massive frost heave in it.
• 13:40
  SPEAKER_01: It wasn't huge, it was very high.
• 13:42
  SPEAKER_01: It was very pronounced.
• 13:43
  SPEAKER_01: It was maybe a foot high, but it was like three feet wide.
• 13:47
  SPEAKER_01: So it was actually like this was a big thing that pushed up through the asphalt.
• 13:50
  SPEAKER_01: And it was just a frost heave.
• 13:51
  SPEAKER_00: You know, it'd come up and then it would said asphalt right there.
• 13:54
  SPEAKER_00: You just said asphalt.
• 13:55
  SPEAKER_01: I said asphalt.
• 13:56
  SPEAKER_01: Okay, asphalt.
• 13:57
  SPEAKER_01: So it come, it's the Michigander in me.
• 14:00
  SPEAKER_01: I can't, I can't.
• 14:01
  SPEAKER_01: Some parts, sometimes it comes out, even though I have to fight it.
• 14:04
  SPEAKER_01: Try and suppress it.
• 14:05
  SPEAKER_01: No, I'm kidding.
• 14:06
  SPEAKER_01: Um so you know, one of these things, a frost heave.
• 14:09
  SPEAKER_01: Can't can we produce these big pronounced like little hills or hummocks or get a boulder several feet up in the course of a single winter?
• 14:16
  SPEAKER_01: The answer really is no, not that fast.
• 14:18
  SPEAKER_01: And we can kind of think about this.
• 14:20
  SPEAKER_01: You said 9%, ice expands broadly 9%.
• 14:24
  SPEAKER_01: So if we have soil that's 50% water, which is a lot, that's a lot of water in a soil.
• 14:29
  SPEAKER_01: If it freezes, it expands 4.5%.
• 14:31
  SPEAKER_01: So we can't really push stuff up dramatically with this process.
• 14:37
  SPEAKER_01: And here's where it gets more complicated.
• 14:39
  SPEAKER_01: And here's how what we learned putting this together, Chris.
• 14:42
  SPEAKER_01: I I think this is a new process or a more detailed process.
• 14:47
  SPEAKER_00: It's a absolutely a more detailed version of the story.
• 14:50
  SPEAKER_01: Of frost heaving, which is something I will bring to class now.
• 14:54
  SPEAKER_01: You know, this is a thing that I'm gonna bring to class.
• 14:55
  SPEAKER_01: I'm gonna talk about because we've seen it in Pennsylvania.
• 14:57
  SPEAKER_01: We see it all over the place is what's called ice lensing.
• 15:01
  SPEAKER_01: And it's a similar process but different.
• 15:03
  SPEAKER_01: And the the way to think about this is you have to think about what gets cold.
• 15:08
  SPEAKER_01: Where does the cold come from, right?
• 15:11
  SPEAKER_01: It's coming from the air.
• 15:12
  SPEAKER_01: So the surface gets cold, the surface freezes, and then that frozen soil freezes downward as it cools down.
• 15:18
  SPEAKER_01: So that deep down it's hotter, it's warmer.
• 15:21
  SPEAKER_01: And so there's liquid water down below this freezing front as the freezing front moves down.
• 15:27
  SPEAKER_01: And what you can get is you can actually get a capillary action where the freezing front attracts more water up.
• 15:35
  SPEAKER_01: And if that water can percolate through the soil fast enough upwards, it's warm, it'll hit the freezing face, and it can actually form a layer of ice.
• 15:44
  SPEAKER_01: And then these things grow outwards, much like kind of columnar jointing things, right?
• 15:49
  SPEAKER_01: They kind of grow perpendicular to the thermal gradient, and so you can grow these kind of ice wedges in a layer, and that has a lot of power.
• 15:58
  SPEAKER_01: If that continues to grow, that can just push a big wedge underneath of the material.
• 16:04
  SPEAKER_01: And this is actually how we get boulders moving up because this happens more under larger particles, it's more likely to happen under large particles than under small particles.
• 16:13
  SPEAKER_01: So if you have a boulder with a bunch of sand around it, you can get an ice lens that forms under that boulder.
• 16:18
  SPEAKER_01: As that ice lens grows, it pushes the boulder up.
• 16:21
  SPEAKER_01: It doesn't have anywhere else to go, but up.
• 16:23
  SPEAKER_00: It's like a nuanced version of ice wedging.
• 16:26
  SPEAKER_00: It's just more a little more complicated.
• 16:28
  SPEAKER_00: And again, I want to just make sure because maybe a lot of people are familiar with this, but maybe some aren't.
• 16:34
  SPEAKER_00: Capillary action is the way that water, because water is a polar molecule, it's water's attracted to water, it behaves like it has this electrical nature to it where opposites attract.
• 16:46
  SPEAKER_00: So it's kind of like if you take the edge of a Kleenex and you dip the corner of a Kleenex into a glass of water, just a corner of it, water will rise up through the Kleenex.
• 16:58
  SPEAKER_00: And it's rising up through those, yeah, it's rising up through those little hollow fibers of the Kleenex.
• 17:06
  SPEAKER_00: They're little tiny hollow fibers, right?
• 17:08
  SPEAKER_00: And they rise up through there, what we call capillary action.
• 17:12
  SPEAKER_01: Exactly.
• 17:13
  SPEAKER_01: That's a I really like that analogy.
• 17:15
  SPEAKER_01: That's a very good one.
• 17:16
  SPEAKER_01: And so, you know, what we're gonna picture here is that we have a stack of Kleenexes, you know, layered on top of each other, and we put a little water on the bottom one, and it can go all the way up through these layers of Kleenexes.
• 17:26
  SPEAKER_01: If the top is frozen, the water will go hit that freezing front and it'll freeze, and we could actually produce an ice wedge in between layers of the Kleenex, in between the stacks of the Kleenex.
• 17:38
  SPEAKER_01: Which gives you a much more efficient lifting.
• 17:41
  SPEAKER_01: And this can be kind of a runaway effect.
• 17:43
  SPEAKER_01: If you start one, start an ice lens somewhere, it's gonna start attracting water not just from right below it, but from the sides.
• 17:50
  SPEAKER_01: And as it kind of grows into this wedge shape, it kind of grows and pulls in from the sides, so it gets kind of more localized.
• 17:57
  SPEAKER_01: And that's a good way to do this.
• 17:59
  SPEAKER_01: And so here's one of the fun terms, Chris, that is applied to these is called frost jacking.
• 18:04
  SPEAKER_01: And this is where you you are pushing something, a single object up dramatically.
• 18:09
  SPEAKER_01: I mean, these things can be we've engineered ways around this, but sort of like concrete pilings in a soil layer that is very permeable could get pushed up two feet per year or something like that.
• 18:20
  SPEAKER_01: I mean, a massive amount of of frostjacking.
• 18:22
  SPEAKER_00: I think the you know, the main way you get the you can get the same thing with a deck, your corner posts and things like this.
• 18:28
  SPEAKER_00: The main way to avoid it is to get below the frost line, get deeper than the deepest place where these ice wedges or ice lenses can form.
• 18:39
  SPEAKER_01: I mean, then then you can't the the frost jacking can't get underneath of your concrete piling, basically, right?
• 18:45
  SPEAKER_01: Yeah.
• 18:45
  SPEAKER_00: And then this is if you dig shallow posts for a deck and you live in an area like I do, like let's say you only go down a foot.
• 18:52
  SPEAKER_00: So the bottom of your post sits a foot below the surface.
• 18:56
  SPEAKER_00: Well, if the frost line goes down below that, then you can absolutely you probably will actually get this mechanism that's gonna then throw your deck out of kilter.
• 19:07
  SPEAKER_01: Oh man, yeah.
• 19:08
  SPEAKER_01: You're just doing a deck edition.
• 19:09
  SPEAKER_01: Hopefully you went deep.
• 19:10
  SPEAKER_01: Hopefully you got your your tractor out there and go deep enough.
• 19:12
  SPEAKER_00: I know what I'm doing.
• 19:14
  SPEAKER_01: Chris's deck building services.
• 19:16
  SPEAKER_01: Also, give them a call.
• 19:18
  SPEAKER_01: I am a handy guy.
• 19:19
  SPEAKER_01: I know what I'm doing.
• 19:21
  SPEAKER_01: So, you know, you can imagine where in cold, very cold climates, places where there's permafrost, in in places like Michigan or Pennsylvania, where you do get you know relatively hard winters, this could be a big problem, especially out in like Dakotas, for instance, where it can freeze down five, six feet deep in the wintertime.
• 19:37
  SPEAKER_01: Sometimes you got to go deep.
• 19:38
  SPEAKER_01: There's an additional layer of engineering that you need to do to kind of drive this, so or to cut prevent this.
• 19:44
  SPEAKER_00: That's right.
• 19:45
  SPEAKER_00: So keep that in mind, these ice lenses that can form, like stacking the Kleenexes up on top, and you then you get wedges in between that really is more efficient lifting of that expansion.
• 19:55
  SPEAKER_00: But combine that with tilling.
• 19:58
  SPEAKER_00: You know, you're constantly tilling up this upper surface, which allows water to percolate and drain and leach through much easier.
• 20:06
  SPEAKER_00: Great point, Chris.
• 20:07
  SPEAKER_01: Like we have to think about why farmers' fields, why are there so many boulders coming in farmers' fields, but not in, you know, the grassland right next door or not on the in the forest right next door, right?
• 20:19
  SPEAKER_01: And think about what we've talked about.
• 20:20
  SPEAKER_01: First, there's a couple things, right?
• 20:22
  SPEAKER_01: And you talked about one of them.
• 20:23
  SPEAKER_01: You're constantly tilling up the soil.
• 20:25
  SPEAKER_01: Okay, what does that do?
• 20:26
  SPEAKER_01: It makes more room for water, fundamentally.
• 20:30
  SPEAKER_01: We're getting more water down deep.
• 20:32
  SPEAKER_01: Make it more porous, absolutely more porous.
• 20:34
  SPEAKER_01: So there's more water.
• 20:35
  SPEAKER_01: So therefore, this frost wedging or this frost jacking process, these lenses can get bigger because there's just a larger supply of water readily available.
• 20:44
  SPEAKER_01: Now, the other thing is that we have to think about it.
• 20:45
  SPEAKER_00: Can I hold on?
• 20:46
  SPEAKER_00: Can I just I wanted just to like double click on that a second?
• 20:50
  SPEAKER_00: Because the reason is because when you churn that soil up by tilling it, you get mostly percolation.
• 20:56
  SPEAKER_00: Whereas on a grassland or in my backyard in your backyard, you get a lot of runoff.
• 21:01
  SPEAKER_00: The water's going somewhere else instead of down to feed these kinds of ice lenses in the wintertime.
• 21:08
  SPEAKER_01: Yeah, totally.
• 21:09
  SPEAKER_01: So the other point that's relevant here is we have to consider what types of soil are good for really percolating water or uh this capillary action that you talked about.
• 21:20
  SPEAKER_01: And so think about soils that might be very good at driving this capillary action.
• 21:25
  SPEAKER_01: They're gonna be porous, they're gonna be permeable, so there's gonna be a lot of holes and they're gonna be all interconnected.
• 21:31
  SPEAKER_01: Okay, good, but conglomerate is a very porous, permeable soil, but it's not great at this, at this capillary action because the holes are big.
• 21:39
  SPEAKER_01: So we want fine particles that have a lot of holes in the soil, and also those holes are interconnected.
• 21:45
  SPEAKER_01: So loamy soil, really fine sandy soil, these are the ones that are really good for farming, and they get tilled a lot, and they're very good at having this capillary action happen.
• 21:58
  SPEAKER_01: So the same soil.
• 22:00
  SPEAKER_01: That are good for farming, like loamy, silty, fine sand, those are also excellent at transmitting water between them and driving this frost jacking process.
• 22:09
  SPEAKER_00: That's right.
• 22:10
  SPEAKER_00: So there's one final thing before we begin wrapping this up, Jesse, which is this tilled up soil.
• 22:18
  SPEAKER_00: I don't mean to contradict myself by saying that most of the water percolates down in, but you still are getting some runoff.
• 22:24
  SPEAKER_00: And because of the looseness of the soil, now you you churned it up, you're helping along the erosion process.
• 22:31
  SPEAKER_00: You're removing some of that loose, easily removed stuff at the surface, which is kind of like by default bringing those big rocks closer to the surface.
• 22:41
  SPEAKER_01: Yeah, yeah, exactly.
• 22:42
  SPEAKER_01: So you could expose by erosion, you can just expose the big rocks because they're not going to get carried away in the rainwater.
• 22:48
  SPEAKER_01: And this would happen, you gotta you gotta think like, okay, this frost wedging process, it's gonna happen in the temperate climates that you live in in Michigan and where I live in, it's a very active process in Pennsylvania, Michigan, the Great Plains, the northern Great Plains, especially, but it's not gonna happen much unless you have cold climates, cold weather.
• 23:06
  SPEAKER_01: So, how do you get boulders exposed in fields in southern climates?
• 23:11
  SPEAKER_01: This sort of soil expansion is one way, but especially on a slope, if you rinse away the soil around the boulder, you can get these things exposed too.
• 23:19
  SPEAKER_01: So, you know, if you're tilling it up frequently, you're always bringing new soil to the surface and it can get washed away.
• 23:25
  SPEAKER_00: But there was a tag-on question, which is does this happen beneath water or at the in bottoms of lakes or oceans, right?
• 23:32
  SPEAKER_01: That was the follow-on question.
• 23:35
  SPEAKER_01: And we can kind of work through this towards an answer, right?
• 23:39
  SPEAKER_01: Like on the bottom of a very, very deep lake that doesn't freeze all the way through.
• 23:43
  SPEAKER_01: It's not gonna happen because we're not doing this frost cycling, we don't have a lot of ice, there's no ice down there, it's all water all the time.
• 23:50
  SPEAKER_01: And also those lakes, they're depositing stuff.
• 23:53
  SPEAKER_01: There's deposition happening, even in these beautiful clear lakes in Michigan.
• 23:57
  SPEAKER_01: You're gonna get biological material deposited, etc.
• 24:00
  SPEAKER_01: It can happen, however, in shallower areas that freeze.
• 24:04
  SPEAKER_01: So if you have a big flat area that's shallow and it freezes all the way down to the bottom, you could potentially drive this process depending upon how deep the frost layer goes in the soil underneath of the lake bottom.
• 24:18
  SPEAKER_01: So, yes, it could happen in shallow water if you're freezing all the way to the bottom.
• 24:22
  SPEAKER_01: But I mean, in Michigan, shallow is like a couple feet, you know, we're not getting it.
• 24:25
  SPEAKER_00: And it's a lot less likely because you you have to get below the frozen layer of the water and then continue down.
• 24:33
  SPEAKER_00: And so you're it you're not gonna get as deep into the soil, therefore, you're not gonna be as likely to heave up these massive rocks that are buried in it.
• 24:43
  SPEAKER_01: Exactly right.
• 24:44
  SPEAKER_01: So, how would you get rocks exposed in areas like that?
• 24:47
  SPEAKER_01: Well, wave action is a great one.
• 24:50
  SPEAKER_01: Running water, if it's in a river, obviously is gonna sweep away the sand size stuff and expose the boulders, but wave action can do this too.
• 24:58
  SPEAKER_01: And we notice this in Michigan, Chris.
• 25:00
  SPEAKER_01: When we go looking for rocks on the shores of Lake Michigan, any big storm, and especially over the winter, you get a lot of turnover.
• 25:07
  SPEAKER_01: So big storms will do a lot of turnover and ice, ice coming, especially uh on the that that west coast of Michigan.
• 25:15
  SPEAKER_01: We have the wind blowing across, and you have ice piling up and doing a lot of erosion.
• 25:21
  SPEAKER_01: Maybe not erosion is not the right word, but moving the soil around, the beach sand around, exposing rocks, moving them around.
• 25:28
  SPEAKER_01: So there's a lot of stuff that happens on the beaches in ways to expose rocks every season, basically.
• 25:34
  SPEAKER_01: Different process, usually totally different process, yeah, than what we've we've been talking about.
• 25:38
  SPEAKER_01: But I mean, uh, Chris, as geologists, aren't we just always interested in getting rocks to the surface?
• 25:43
  SPEAKER_01: Like, this seems like a good problem, you know.
• 25:44
  SPEAKER_01: But I'm not a farmer who's dinging up the my equipment on boulders.
• 25:48
  SPEAKER_01: But personally, I'm happy that the boulders come to the surface because we get to go look at them and they're very cool.
• 25:52
  SPEAKER_00: I know, I I am too.
• 25:54
  SPEAKER_00: I'm just disappointed that they discovered that they're actually worthy of being sold, you know.
• 25:58
  SPEAKER_00: Like I want the days 15 years ago, 20 years ago where they they didn't care.
• 26:03
  SPEAKER_00: They're just like, yeah, take my rocks.
• 26:04
  SPEAKER_00: Yeah, get them out of here.
• 26:05
  SPEAKER_00: Get them out of my way.
• 26:06
  SPEAKER_01: Yeah, I know.
• 26:07
  SPEAKER_01: It's true.
• 26:08
  SPEAKER_01: I haven't asked uh anybody to do that in a while.
• 26:10
  SPEAKER_01: Maybe I should attempt it a little bit.
• 26:12
  SPEAKER_01: The problem is, you know, there's a lot of these areas that, especially around here in eastern Pennsylvania, there's some very cool outcrops that are very localized.
• 26:19
  SPEAKER_01: I mean, we were looking out in um where were we?
• 26:22
  SPEAKER_01: Right in Maryland, across the Pennsylvania border, there's this beautiful outcrop of a basalt that has been chuck full of epidotes.
• 26:30
  SPEAKER_01: So it's this bright pistachio green with quartz veins running through it.
• 26:34
  SPEAKER_01: It's a spectacular rock.
• 26:36
  SPEAKER_01: But it's exposed in a road cut, like a highway roadcut that's really busy and right next to the road.
• 26:41
  SPEAKER_01: So it's like pretty sketchy to go, you know, get up on the cliff and and collect anything because there's cars whizzing past, and and but you go right over the hill, and there's a bunch of people who have this stuff laying around in their yard because they're sitting on this outcrop, but it's a really like localized outcrop.
• 26:57
  SPEAKER_01: And we were over, I was over there with a buddy.
• 26:59
  SPEAKER_01: Uh, this was maybe six months ago.
• 27:01
  SPEAKER_01: We were gonna go knocking on doors, but it was getting dark, and we're like, you don't want to be the people knocking on doors right when it's getting dark.
• 27:06
  SPEAKER_01: That's a way to turn people off.
• 27:08
  SPEAKER_01: Um, you want to go there on like a Saturday morning, you know, and and knock on some doors.
• 27:13
  SPEAKER_01: But that's the last time I can see.
• 27:14
  SPEAKER_00: Well, I think you know, I think you need to do a midnight run to the outcrop when it's not as busy as true.
• 27:20
  SPEAKER_01: Bring some headlamps, and yeah, that's a good point.
• 27:22
  SPEAKER_00: Well, you just need to figure this situation out, Jesse.
• 27:24
  SPEAKER_00: Yeah, I know.
• 27:24
  SPEAKER_00: It's not that difficult.
• 27:25
  SPEAKER_00: Being a rookie over here, like, what's going on?
• 27:27
  SPEAKER_01: Well, when you come to Pennsylvania, we'll drink we'll maybe go check it out.
• 27:30
  SPEAKER_01: Deal.
• 27:30
  SPEAKER_00: Is it a vesicular basalt?
• 27:32
  SPEAKER_00: Is that where the epidote sits?
• 27:33
  SPEAKER_01: No, no, it's like pervasive.
• 27:34
  SPEAKER_01: It's per it's like throughout, it's kind of overprinted the entire almost entire basalt.
• 27:38
  SPEAKER_01: It's really spectacular.
• 27:39
  SPEAKER_00: So do you get any crystals or or is it just is it just a smearing of epidote?
• 27:43
  SPEAKER_01: It's like a big smearing, and those some of it's like big veins too, but it's not crystals of epidote, it's just like that pistachio green, the whole rock is that, and there's quartz veins running through it that are smoky or white quartz running through it.
• 27:56
  SPEAKER_01: It's very pretty.
• 27:56
  SPEAKER_01: But no crystals to speak of awesome.
• 27:58
  SPEAKER_01: So all right, well, Chris, that's a wrap, right?
• 28:02
  SPEAKER_01: Yeah, yeah.
• 28:02
  SPEAKER_01: That's a wrap.
• 28:03
  SPEAKER_01: I think if Joyce doesn't pick frost jacking as the word of the day, I'm gonna be a little upset.
• 28:07
  SPEAKER_01: I'll be honest with you.
• 28:08
  SPEAKER_00: I don't know.
• 28:08
  SPEAKER_00: There were a couple other ones.
• 28:09
  SPEAKER_00: There, yeah, there are options for her.
• 28:12
  SPEAKER_00: She'll, you know, hopefully she picks something other than till or you know, something like that.
• 28:18
  SPEAKER_00: You know what you know what it's gonna be.
• 28:20
  SPEAKER_01: It's gonna be Doritos.
• 28:21
  SPEAKER_01: That's gonna be the word of the day.
• 28:22
  SPEAKER_00: She knows I love Doritos.
• 28:24
  SPEAKER_00: Yeah, like she knows.
• 28:26
  SPEAKER_00: But when I was a kid, she bought me the knockoff brand, and there's no knockoff of Doritos.
• 28:30
  SPEAKER_00: You know, that's it's the real thing.
• 28:32
  SPEAKER_01: That's why she's gonna think, oh, Doritos, oh Chris, oh, I love my son.
• 28:35
  SPEAKER_01: Oh, I wish I'd given him real Doritos when he was growing up, and then that's gonna be the word of the day.
• 28:39
  SPEAKER_00: So if any of our listeners are Dorito executives, I will be glad to be the face of Doritos.
• 28:46
  SPEAKER_02: Chris will gladly accept an unlimited supply of Doritos at his house for mentioning Doritos on the podcast.
• 28:52
  SPEAKER_01: Yeah.
• 28:53
  SPEAKER_01: Oh Chris is just and Skittles, too.
• 28:55
  SPEAKER_01: If anybody out there works for the Skittles company or whoever makes the Skittles, that's right, let them know.
• 28:59
  SPEAKER_01: Because Chris is accepting donations at his house of Skittles and Doritos.
• 29:04
  SPEAKER_01: I can just see you munching away on Doritos in your tractor.
• 29:08
  SPEAKER_01: You probably got like a little homemade chip bag that you've made on your tractor just for the Doritos, don't you?
• 29:13
  SPEAKER_00: That and a beer holder.
• 29:15
  SPEAKER_00: So I'm good to go.
• 29:16
  SPEAKER_00: And a chapstick holder somewhere on that thing.
• 29:18
  SPEAKER_00: I don't have that yet, but I need that.
• 29:20
  SPEAKER_00: Gotta get on it.
• 29:20
  SPEAKER_00: Unbelievable.
• 29:21
  SPEAKER_00: Unbelievable.
• 29:22
  SPEAKER_01: All right.
• 29:23
  SPEAKER_01: Hey, that's a wrap.
• 29:24
  SPEAKER_01: Thanks for listening.
• 29:24
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• 29:55
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