Latest / PlanetGeo: The Geology Podcast / Eating Rocks For Breakfast

Transcript

Eating Rocks For Breakfast · 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.
• 0:15
  SPEAKER_02: Christopher, he's back.
• 0:20
  SPEAKER_01: Smudgy fingers is back.
• 0:23
  SPEAKER_02: That was that comment.
• 0:24
  SPEAKER_02: I forget if that was on Spotify or YouTube.
• 0:27
  SPEAKER_00: Whoever left the comment, smudgy fingers is back.
• 0:31
  SPEAKER_00: You made my week.
• 0:33
  SPEAKER_00: That was that was pretty good.
• 0:34
  SPEAKER_00: Made me laugh.
• 0:35
  SPEAKER_02: That was the greatest comment I've heard in a long time.
• 0:38
  SPEAKER_02: Oh, that was spectacular.
• 0:39
  SPEAKER_02: I got such good mileage out of that.
• 0:41
  SPEAKER_02: Just laughing to myself, walking to my truck.
• 0:43
  SPEAKER_02: Why?
• 0:44
  SPEAKER_02: That's so good.
• 0:45
  SPEAKER_02: Um, Chris, to today, uh, we I don't how okay, on a scale of one to a hundred, how conflicted are you about this topic?
• 0:54
  SPEAKER_02: Because I am deeply conflicted.
• 0:55
  SPEAKER_00: I'm all right, yeah, in the 80s range for me.
• 0:59
  SPEAKER_01: Oh, I was gonna go lower.
• 1:00
  SPEAKER_02: I'm like 70 to 75 conflicted.
• 1:02
  SPEAKER_02: Okay, all right.
• 1:03
  SPEAKER_02: I'm maybe more because well, I don't know.
• 1:05
  SPEAKER_02: I maybe not what more, but we are gonna talk about the role.
• 1:09
  SPEAKER_01: Well, I meant I meant like I'm I'm hold on.
• 1:11
  SPEAKER_01: I I think I miss misunderstood you.
• 1:13
  SPEAKER_01: I went the other way.
• 1:14
  SPEAKER_01: Like, I think I am more conflicted than you.
• 1:16
  SPEAKER_01: Oh, you think you're more?
• 1:17
  SPEAKER_02: Okay, no, I'm saying like I'm I'm really conflicted here, and like hundreds a lot.
• 1:21
  SPEAKER_02: So you're you're saying you're even more than that.
• 1:22
  SPEAKER_02: You're like super conflicted.
• 1:24
  SPEAKER_02: Yeah, I'm like 85 conflicted then, yeah.
• 1:26
  SPEAKER_02: Yeah.
• 1:27
  SPEAKER_02: The uh the the topic here is biology, and uh we try and stray away from it.
• 1:33
  SPEAKER_02: We've talked many times in this podcast, how you know both our fathers are our biology, we're former biology teachers.
• 1:38
  SPEAKER_02: Uh, we were inundated with it growing up, and uh we consider that to be the stuff, the crappy stuff that covers up all of our rocks.
• 1:46
  SPEAKER_02: But that's right.
• 1:47
  SPEAKER_02: What we're talking about today is the importance of biology, especially for breaking rocks, which for me, Chris, I have become newly aware of the importance of this process and how complicated and how perhaps future relevance of this process.
• 2:04
  SPEAKER_02: So, where do you stand on this and why are you conflicted?
• 2:08
  SPEAKER_01: Yeah, you you said something really interesting because one of my takeaways was that um you know, weathering does not just break rocks apart, but it also is weathering is kind of a hero, actually, in the in the history of our of our earth, in the history of our planet.
• 2:24
  SPEAKER_01: Oh, interesting.
• 2:25
  SPEAKER_01: Please elaborate.
• 2:26
  SPEAKER_02: That was an interesting phrase there.
• 2:28
  SPEAKER_02: I like that.
• 2:28
  SPEAKER_02: Yeah, yeah.
• 2:29
  SPEAKER_02: Well, okay, no, maybe, no, yeah, but maybe that maybe that's a good point.
• 2:32
  SPEAKER_02: Let's that's a I wanted to save that phrase though, because I've never heard you say that before.
• 2:36
  SPEAKER_02: That's interesting.
• 2:36
  SPEAKER_02: A hero.
• 2:37
  SPEAKER_02: Uh, I like that.
• 2:38
  SPEAKER_02: Okay, why are you conflicted?
• 2:41
  SPEAKER_01: Because it's biology.
• 2:42
  SPEAKER_01: Uh oh, so I don't know.
• 2:44
  SPEAKER_01: Um I'm just honest, but that that doesn't really matter.
• 2:48
  SPEAKER_02: Dave, what is Dave gonna say?
• 2:49
  SPEAKER_02: I have a question.
• 2:50
  SPEAKER_02: What do you think Dave's gonna say about this episode?
• 2:52
  SPEAKER_02: You're gonna go over there like you know, the Friday, maybe after this comes out, or two Fridays after.
• 2:56
  SPEAKER_02: You're gonna go over there and have a beer with your dad and your mom.
• 2:58
  SPEAKER_02: And what is Dave gonna say?
• 3:00
  SPEAKER_00: Chris, I just think that was the greatest episode you've released in the six years.
• 3:05
  SPEAKER_00: Is that is that what he's gonna do, or what do you think?
• 3:07
  SPEAKER_00: Yeah, probably, probably.
• 3:09
  SPEAKER_00: Yeah, just the most interesting episode.
• 3:13
  SPEAKER_01: That's a pretty good Dave rendition, right there, by the way.
• 3:16
  SPEAKER_02: I'll have to I don't have him pegged nearly as much as you do, but I I'm excited to hear uh how it goes with you and him after after he listens to this.
• 3:24
  SPEAKER_01: I will absolutely let you know.
• 3:26
  SPEAKER_01: Um, yeah, I I think like I was just torn because I this was never my draw to the geosciences.
• 3:33
  SPEAKER_01: I think some of the processes that that uh weathering involves are fascinating.
• 3:39
  SPEAKER_01: And you know, you can you can go in a lot of different directions.
• 3:42
  SPEAKER_01: You can go down the the chemistry path and the chemistry gets complicated real fast.
• 3:46
  SPEAKER_01: Um so if that's your thing, that's a draw, you know.
• 3:49
  SPEAKER_01: And I I like uh you know some of the some of the physical weathering processes have you know, you and I we both love Yosemite so much and and exfoliation is a a major player in a place like that.
• 4:00
  SPEAKER_01: Um and that's a really cool process.
• 4:02
  SPEAKER_01: And then to see that, you know, get captured on on somebody's phone actually happening, that's just a that's a really cool thing.
• 4:11
  SPEAKER_01: But it was it's never been my draw to the geosciences.
• 4:14
  SPEAKER_01: So I guess that's that's kind of my thing is you you you know you brought it to me, said, Hey, let's let's think about this, and and it took me a while to come around.
• 4:22
  SPEAKER_02: Yeah, so for me, this is I mean it's conflicting in the same reason it's it's biology.
• 4:26
  SPEAKER_02: We're gonna talk about the role of biology in weathering and specifically chemical weathering, dissolving rocks.
• 4:31
  SPEAKER_02: So, Chris, basically the the punchline here is that it's incredibly important, and actually really important at the big scale, which we kind of are in intuitive big scale, but it's also really important at the small scale.
• 4:45
  SPEAKER_02: And it's I think a really forward-looking discipline for jobs for like the future energy supply.
• 4:54
  SPEAKER_02: There's companies being started based on biomining and biomineralization, and the reactions that we're gonna talk about are incredibly complicated, require interdisciplinary skill sets, and I think there's a a really big sort of market future to them, to these skill sets.
• 5:08
  SPEAKER_02: So I think there's like a really um having something like a geobiology degree, it's actually a really promising time for for people at the intersection here.
• 5:18
  SPEAKER_02: So, with that note, like this is what we're gonna talk about.
• 5:20
  SPEAKER_02: It's a really important process.
• 5:21
  SPEAKER_02: I've underappreciated it my entire career thus far.
• 5:24
  SPEAKER_02: I think probably you have a little bit too.
• 5:27
  SPEAKER_02: Correct me if you don't feel that way, Chris.
• 5:29
  SPEAKER_02: But can you give us like the the intro level?
• 5:31
  SPEAKER_02: How do we normally teach weathering?
• 5:34
  SPEAKER_02: And then how is this a mod what are we gonna talk about here?
• 5:36
  SPEAKER_02: That's like a deeper level modification of that.
• 5:39
  SPEAKER_01: That's a really good lead, Jess.
• 5:41
  SPEAKER_01: Thanks for that.
• 5:42
  SPEAKER_01: Um, that's like you just nice softball.
• 5:45
  SPEAKER_02: I know what I cover, and like I I have a slide in my head that I show that's wrong.
• 5:50
  SPEAKER_02: And we're gonna talk about why it's wrong.
• 5:52
  SPEAKER_01: It's not really wrong, but it's kind of wrong, you know, right?
• 5:55
  SPEAKER_01: I mean it's semantics.
• 5:56
  SPEAKER_01: It's but you're talking about things like root wedging.
• 5:59
  SPEAKER_02: It's yes, it's a massive oversimplification.
• 6:02
  SPEAKER_02: So, like, get us to root wedging, and and then we'll go from there into this deeper topic of of sort of bioweathering.
• 6:08
  SPEAKER_01: Yeah, I actually just got done going over this with my own classes, the intro level that that you teach.
• 6:14
  SPEAKER_01: And and uh, you know, we all have these pictures where these trees are doing just amazing things to these rocks, they're splitting boulders apart or they're growing in places in these little tiny cracks and crevices, and they'll they're widening.
• 6:26
  SPEAKER_01: It's a it's almost like ice wedging, you know, and when water freezes, it expands by nine percent, and the roots do the same thing.
• 6:33
  SPEAKER_01: Can I interrupt real quick, Chris?
• 6:34
  SPEAKER_02: And just can you go back to weathering generally and just give us like the you know, two-minute weathering overview, and then ends with the root wedging process that you're talking about.
• 6:45
  SPEAKER_01: Any intro level geoscience class is going to cover weathering really as two parts.
• 6:50
  SPEAKER_01: You have mechanical or physical weathering, and then you have chemical weathering.
• 6:54
  SPEAKER_01: And you know, mechanical weathering, things like ice wedging.
• 6:57
  SPEAKER_01: It's just you're taking rocks and you're breaking them apart into smaller and smaller and smaller pieces, but there's no change in chemistry.
• 7:03
  SPEAKER_01: And so you're you're talking about things like exfoliation, ice wedging, and and like you said, we often will throw, I don't know, like we'll we'll throw root wedging, we don't really know what to do with it.
• 7:16
  SPEAKER_01: It's biologically kind of it's related to that, but it doesn't involve a change in the chemistry of the rocks necessarily, although we're gonna tell you, yes, it does, but not root wedging.
• 7:26
  SPEAKER_02: That's right.
• 7:27
  SPEAKER_02: So, Chris, the the image in your head you should have that we always show in these these classes when we're talking about physical weathering here and the biological like addition to that root wedging is basically it's a tree.
• 7:40
  SPEAKER_02: You can think of like a tree, there's this one from I think Pictured Rocks, where there's like a tree growing into a crack in a cliff, basically, and hang it looks like it's hanging on for deer life, but the roots are penetrating cracks in the rocks.
• 7:51
  SPEAKER_02: And you can imagine as the root grows, the the cracks in the rock get a little bit bigger just by kind of that expansion pressure is the way we teach you, or maybe there's a plant growing up through a sidewalk crack.
• 8:01
  SPEAKER_02: That's the kind of root wedging sort of model.
• 8:03
  SPEAKER_02: So that's the image that we show, and we kind of say, yeah, this is physical weathering.
• 8:07
  SPEAKER_02: This is breaking rocks, take big rock, make it small rock, right?
• 8:10
  SPEAKER_02: We usually in this intra-level way turn to chemical weathering, which is a very different process.
• 8:16
  SPEAKER_02: We talk about common reactions, we talk about kind of the oxidation, the uh weathering reactions, we talk about breaking silicate bonds and the calcium goes out into the river system and ends up in the ocean and then draws down CO2 and forms calcite in the oceans.
• 8:32
  SPEAKER_02: We talk about the the sort of chemical weathering cycle, but we kind of leave it as like at least I do leave it there as like chemical weathering, basic process.
• 8:40
  SPEAKER_02: We don't get deeper into the chemical weathering.
• 8:42
  SPEAKER_02: And what we're gonna talk about today is focusing on the biochemical weathering, which is way more important than that physical, it's a it's a much more dominant force than that physical weathering image that you have in your head of like tree root breaking into a rock.
• 8:59
  SPEAKER_02: That's actually not how it works.
• 9:01
  SPEAKER_02: The tree root actually is chemically working its way through the rock, it's not physically breaking the rock.
• 9:07
  SPEAKER_02: So I think that's like the that's kind of the take-home point.
• 9:09
  SPEAKER_02: You could hit stop on this podcast, and that would kind of be the take home point, but we're gonna get into more detail of how that happens, right?
• 9:14
  SPEAKER_02: Like that to me, that's something I had not appreciated.
• 9:18
  SPEAKER_02: And uh, it's the role of really organic acids in this process.
• 9:23
  SPEAKER_02: So um, so Chris, did you take organic chemistry in college?
• 9:28
  SPEAKER_02: You did?
• 9:29
  SPEAKER_02: Okay.
• 9:30
  SPEAKER_02: I I didn't, I avoided it like the plague.
• 9:32
  SPEAKER_02: That was for the pre-med students.
• 9:33
  SPEAKER_02: Um, that was not required for the BS major.
• 9:36
  SPEAKER_01: Right.
• 9:36
  SPEAKER_01: I I so for geoscience I had to take inorganic.
• 9:40
  SPEAKER_01: But as a teacher, I wanted to be as marketable as I could be.
• 9:44
  SPEAKER_01: And so I picked up a minor in chemistry so I could I could teach that.
• 9:49
  SPEAKER_01: And I actually did teach chemistry for the first, I don't know, three or four years of my high school, um, my career.
• 9:56
  SPEAKER_02: See, Chris, in this aspect, you are more overeducated than I am then.
• 9:59
  SPEAKER_01: Oh no, no, I'm not.
• 10:01
  SPEAKER_01: Don't ever say that.
• 10:04
  SPEAKER_01: Oh, that was too offensive for you.
• 10:05
  SPEAKER_01: That crossed the line.
• 10:07
  SPEAKER_01: Yeah, you did.
• 10:08
  SPEAKER_01: You crossed the line.
• 10:09
  SPEAKER_01: Okay, yeah, okay.
• 10:10
  SPEAKER_01: Um, yeah, so you're right, Jesse.
• 10:12
  SPEAKER_01: I mean, you're exactly right about how these with the roots or the chemical reactions that the plants are having in the soil.
• 10:21
  SPEAKER_01: Um, you alluded to it actually right from the outset when you talked about and I think maybe people are listening to saying, What is what was he talking about?
• 10:28
  SPEAKER_01: Uh like this career in biogeology or you know, geobiology is that these chemical reactions involved can actually um maybe concentrate rare earth elements or or other things like that.
• 10:43
  SPEAKER_01: And I that's where we're gonna go at the tail end of this episode.
• 10:46
  SPEAKER_01: But Jesse, I think first we should talk about some key points in time.
• 10:52
  SPEAKER_01: What do you think?
• 10:52
  SPEAKER_01: You you think so?
• 10:53
  SPEAKER_02: Like, okay.
• 10:54
  SPEAKER_02: Yeah, yeah, yeah.
• 10:54
  SPEAKER_02: Oh, we go back in time.
• 10:55
  SPEAKER_02: You know, I get excited about that.
• 10:57
  SPEAKER_02: The this is another, I would even say, you know, I'd actually very confidently say this is a frontier in research at the moment, right now, is we we have not had plants on Earth for the entirety of Earth history.
• 11:09
  SPEAKER_02: There's been life for a long time, three billion years, maybe 3.5, maybe 3.7, maybe 4 billion years, depends on who you ask.
• 11:16
  SPEAKER_02: But land plants are a really relatively recent thing.
• 11:20
  SPEAKER_02: Around 470, 450 million years ago is when land plants, plants started to colonize the land surface.
• 11:27
  SPEAKER_02: So you have to think that's one tenth of Earth history ago.
• 11:31
  SPEAKER_02: So for nine tenths of Earth's history, we had barren continental landscapes.
• 11:37
  SPEAKER_02: Like there was no land plants there.
• 11:39
  SPEAKER_02: That means we've talked about this before, river meandering dynamics were completely different.
• 11:44
  SPEAKER_02: The entire landscape was quite different.
• 11:45
  SPEAKER_02: The weathering process was quite different.
• 11:47
  SPEAKER_02: Uh, land plants came on the scene 470 to 450 million years ago.
• 11:51
  SPEAKER_02: Forests really started to emerge kind of just after 400 million, 390, 360 million years ago, and then really deep-rooted vascular plants only emerged relatively recently, like kind of after 140, 150 MA, something like that.
• 12:05
  SPEAKER_02: So there's these step changes, and and there's a really active field of research that's pointing to how the evolution of land plants really impacted not only just the surface environments, but actually igneous rocks through time.
• 12:18
  SPEAKER_02: So if you look at igneous rocks, the chemistry of igneous rocks have changed in dramatic ways at step function points in Earth history when land plants colonized or when forests emerge.
• 12:29
  SPEAKER_02: There's way more shale that's formed on Earth today than there was 600 million years ago.
• 12:36
  SPEAKER_02: Why is that?
• 12:36
  SPEAKER_01: Let's walk through that.
• 12:37
  SPEAKER_02: Let's let's that's worth it.
• 12:39
  SPEAKER_02: Because chemical weathering is a much more dominant process.
• 12:43
  SPEAKER_02: Because there are organic acids around in the environment, all these things that plants give off, the chemical weathering is a much more dynamic process.
• 12:52
  SPEAKER_02: Particularly the silicate process.
• 12:54
  SPEAKER_02: Yep.
• 12:54
  SPEAKER_02: Particularly for the silicates, so there's way way more clay produced.
• 12:58
  SPEAKER_02: That clay has when there's organic carbon dissolved in the water, it tends to flock, flocculate, and and you know, you get uranium in solution much more and things like that.
• 13:07
  SPEAKER_02: So there's all these feedback loops that happen when you have weathering processes on the land surface.
• 13:14
  SPEAKER_02: That's right.
• 13:15
  SPEAKER_01: And we talked about this, Jesse, a long, long time ago.
• 13:17
  SPEAKER_01: Sorry to interrupt, but we talked about this with you know, let's say spheroidal weathering, and how you know this happens because you know, feldspar is so abundant in rocks like granite, but it's also quite susceptible to chemical weathering.
• 13:32
  SPEAKER_01: And what we're saying in this episode is that biology plays a huge role in the lake of chemical weathering.
• 13:41
  SPEAKER_02: It does.
• 13:42
  SPEAKER_02: Biology plays a huge role.
• 13:45
  SPEAKER_02: I I I don't, it just grinds my gears hearing you say that, but it's true.
• 13:50
  SPEAKER_02: Biology plays a huge role.
• 13:51
  SPEAKER_02: Like we talk, and at the very basic level, the most intuitive level, this makes sense.
• 13:56
  SPEAKER_02: We I think we intuitively know this.
• 13:57
  SPEAKER_02: If you make plants on a hill slope, let's say you add a bunch of plants to it, the soil is locked in place.
• 14:03
  SPEAKER_02: It decreases the rate of physical erosion.
• 14:06
  SPEAKER_02: So basically, you have the soil locked in place by the root structures that's held in place.
• 14:11
  SPEAKER_02: Actually, the organic matter in the soil that the the you know dead or dead and decaying organic matter also helps hold the soil in place.
• 14:19
  SPEAKER_02: So this slows down the erosion of rock.
• 14:22
  SPEAKER_02: It it slows down the exposure of fresh rock, so there's less fresh rock exposed in the same time period.
• 14:31
  SPEAKER_02: So basically, it increases the the relative importance of chemical weathering because everything's locked in place and water is kind of getting flushed through it.
• 14:38
  SPEAKER_02: You've got all these, as we'll talk about, biologically produced organic acids that are being leached through the system as well.
• 14:46
  SPEAKER_01: Okay, but you just contradicted what I said.
• 14:49
  SPEAKER_01: So we need to like walk down that path.
• 14:52
  SPEAKER_01: You're saying that plants and roots and you know things like this, they actually lock things in place, they aggregate material.
• 15:01
  SPEAKER_01: All of that kind of protects the the rock below from being weathered.
• 15:06
  SPEAKER_01: But I just said that biology speeds up weathering, so we have to bridge that gap.
• 15:11
  SPEAKER_02: So in and this I think is touching on the complexity here.
• 15:15
  SPEAKER_02: I think a short a short summary of this episode would say biology matters a lot, but it's freaking complicated.
• 15:20
  SPEAKER_02: Like this is a this is a really complicated space because you're right, you've pointed to one of the the key kind of inconsistencies, and maybe this is where the kind of climate uh the the regulatory thermostat, why there's argument about the the thermostat on earth, like you know, we've talked about weathering as the thermostat, and we can think about weathering very simply as yeah, go ahead.
• 15:39
  SPEAKER_01: We never said it that way, Jesse.
• 15:40
  SPEAKER_01: We never said it that way.
• 15:42
  SPEAKER_01: We we've always said CO2 is the thermostat, and that's why right at the outset of this episode, I said that that you know, weathering is actually can be thought of as the hero of of our climate and in our existence here without being broiled away.
• 15:59
  SPEAKER_01: It's because of weathering, and so it's just a different take on maybe you and I have I don't know if we've looked at it incorrectly, as this is certainly going to change the way I think about things for sure.
• 16:12
  SPEAKER_01: In this like you know, we've talked about the carbon cycle and the role that weathering plays in it, but now we have to Jesse get into how does then biology, how do plants, land plants, speed up the weathering at the surface of the earth, and then we can get into how it sets the dial.
• 16:31
  SPEAKER_02: So this is I think we need to be we need to be careful on the the phrasing here, because you're exactly right.
• 16:35
  SPEAKER_02: I said that wrong.
• 16:36
  SPEAKER_02: Uh and and you know that's the same thing.
• 16:39
  SPEAKER_02: Well, CO2 is the important thermostat, not necessarily weathering, because weathering's a kind of a catch-all term.
• 16:45
  SPEAKER_02: We have chemical weathering, we have physical weathering, we have erosion involved in there too.
• 16:49
  SPEAKER_02: Erosion's an important thing.
• 16:50
  SPEAKER_02: And so plants at a very simple level hold stuff in place for longer, which means that you get more intense chemical weathering in a specific location if the plants are there.
• 17:04
  SPEAKER_02: And there are some locations, Chris.
• 17:05
  SPEAKER_02: I'm gonna jump ahead a little bit here because in Iceland, you were just there this past summer.
• 17:11
  SPEAKER_02: In Iceland, there's been the previous summer.
• 17:15
  SPEAKER_02: It's not been more than a year ago, has it?
• 17:19
  SPEAKER_02: A year and a half ago?
• 17:20
  SPEAKER_02: Well, I'm going on two, yeah, yeah, yeah.
• 17:22
  SPEAKER_02: Yeah.
• 17:22
  SPEAKER_02: Wow crazy.
• 17:23
  SPEAKER_02: No kidding.
• 17:24
  SPEAKER_02: That is not okay.
• 17:25
  SPEAKER_02: Yeah.
• 17:25
  SPEAKER_02: Holy smokes.
• 17:26
  SPEAKER_02: Okay, wow, time flies.
• 17:28
  SPEAKER_02: Uh, I don't remember the last year and a half, it turns out.
• 17:31
  SPEAKER_01: Um, so in in Iceland, you had a kid, I think, somewhere in there.
• 17:35
  SPEAKER_01: So something's happened.
• 17:36
  SPEAKER_02: I don't remember.
• 17:38
  SPEAKER_02: Um in so on Iceland and the basalts on Iceland, people have documented that if you have weathering, chemical weathering in one location without trees, and you go to the same location, kind of same hill slope, same suniness, same temperature, same humidity, same all that stuff, you get a two to ten times increase in the chemical weathering of basalt, which is basically plagioclos and pyroxine, when you have trees around.
• 18:02
  SPEAKER_02: So trees in that instance increase the rate of chemical weathering, and they usually document this.
• 18:06
  SPEAKER_02: This is kind of cool, by looking at the river chemistry.
• 18:09
  SPEAKER_02: So you can look at the river chemistry and just say, okay, how much calcium and magnesium is dissolved in this thing?
• 18:13
  SPEAKER_02: What's the total organic carbon content of this thing?
• 18:16
  SPEAKER_02: Like you can work out what's the total chemical weathering going on upstream in the catchment in the sort of river system here.
• 18:23
  SPEAKER_02: And two to ten time increase, that's a lot.
• 18:25
  SPEAKER_02: That that you know, that's an order of magnitude increase in the chemical weathering rate.
• 18:29
  SPEAKER_02: And so people have also documented this in the lab where they take, I mean, really kind of cool studies we're we're thinking about, um, kind of starting to try and replicate some of these, is to basically take a granite, crush it up really fine, take up a salt, crush it up, dump it into some vat with a you know, make up a chemical recipe that you want to test, and just let it sit there for like weeks and week, maybe even a year, or close to a year, and then measure the composition.
• 18:56
  SPEAKER_02: Look what comes off of it, look what's left behind, and you get kind of a weathering reaction rate, right?
• 19:00
  SPEAKER_02: So it's it's doing this chemical weathering process in the lab, and people have documented this um out in the in the field too.
• 19:08
  SPEAKER_02: But it's not always the case.
• 19:10
  SPEAKER_02: It's not always like plants increase chemical weathering.
• 19:14
  SPEAKER_02: It's not always clear that they increase total weathering because they obviously decrease the physical weathering rate.
• 19:19
  SPEAKER_02: They decrease the amount of fresh rock that's exposed at the surface because we're kind of locking in, we're we're making the soil horizon thicker.
• 19:27
  SPEAKER_02: So it's not always the total weathering is is a complicated thing.
• 19:30
  SPEAKER_02: They certainly increase chemical weathering.
• 19:32
  SPEAKER_02: Um, which I think is the goes back to our modification of the intro-level thing, because I always talked about throw that one slide up and say biology does physical weathering.
• 19:41
  SPEAKER_02: Done, move on.
• 19:42
  SPEAKER_02: But actually, biology is way more important for the chemical weathering, and actually that's kind of the big dog in this in this battle.
• 19:48
  SPEAKER_01: That's the takeaway, I think, here.
• 19:50
  SPEAKER_01: Right.
• 19:50
  SPEAKER_01: So, Jesse, I think skin level, skin deep, what is it that the biology is producing?
• 19:57
  SPEAKER_01: What are these plants making that speed up the chemical weathering process, right?
• 20:03
  SPEAKER_01: And everybody knows water's got to be involved.
• 20:06
  SPEAKER_01: The more water you have, the faster chemical weathering takes place, and the warmer it is, the faster chemical weathering takes place.
• 20:12
  SPEAKER_01: But maybe more importantly, is the more acidic the water is, the lower the pH, the faster the weathering takes place.
• 20:22
  SPEAKER_01: So, what is it with the biology?
• 20:24
  SPEAKER_02: What's the that's exactly right.
• 20:26
  SPEAKER_02: I mean, and we can think about pH with sort of normal acids.
• 20:30
  SPEAKER_02: We walk around as geologists with really dilute HCl as an acid that you know creates uh creates the the H plus ion there.
• 20:38
  SPEAKER_02: What we think about when it comes to plant life is organic acids.
• 20:42
  SPEAKER_02: And these are what people sometimes call low molecular weight organic molecules, but they're things like citric acid.
• 20:49
  SPEAKER_02: I mean, some people have this in their house sometimes as like a cleaning solution.
• 20:52
  SPEAKER_02: You know, citric acid is around, oxalic acid, acetic acid.
• 20:57
  SPEAKER_02: There's a whole bunch of these different sort of acids that are formed by biology, as the name implies.
• 21:02
  SPEAKER_02: And there's a whole, you know, intro-level, not intro-level, it's like the filter class for pre-meds, at least it was at Hope College, is organic chemistry.
• 21:10
  SPEAKER_02: That was like the filter class.
• 21:11
  SPEAKER_02: I avoided it like the flag, I never took it.
• 21:13
  SPEAKER_02: I was never interested in it.
• 21:14
  SPEAKER_02: I was like, I don't want to go through that.
• 21:16
  SPEAKER_02: I don't need it for my geology major, so why would I take that?
• 21:19
  SPEAKER_02: You know, so these acids are really, turns out they're very powerful reactants that rapidly increase the rate of chemical weathering.
• 21:29
  SPEAKER_02: And so, Chris, there's this article we read, and a lot of this comes from work, I should say, right now at Penn State University.
• 21:35
  SPEAKER_02: I am in one of the foundational homes of the field of what's called earth system science, which is thinking about we've talked to Lee Cump before about this, our our current dean, Sue Brantley, is a name who she's uh she just retired, she's emeritus now at Penn State, but kind of a huge name in this chemical weathering space.
• 21:55
  SPEAKER_02: She's done a ton of work, and she actually pointed me to one of these papers that a review paper.
• 22:00
  SPEAKER_02: That talked about the role of chemical weathering and organic acids in this chemical weathering process.
• 22:04
  SPEAKER_02: But this is her whole career, and she is an incredibly famous, highly prolific scientist based on a lot of this work.
• 22:11
  SPEAKER_02: I say that because I'm speaking way outside our expertise here, but there's a lot of work that goes into understanding these processes.
• 22:18
  SPEAKER_02: There's an image, Chris, in that article we read that uh Sue wrote this is a really cool uh sort of case study of looking at a rock, and they took a soil sample from the cascades.
• 22:32
  SPEAKER_02: So we're looking at like weathered volcanic, relatively fresh uh rock, volcanic rock from the cascades.
• 22:40
  SPEAKER_02: So this soil has a bunch of stuff in it, it's got some feldspar grains in it, it's got some quartz grains in it, you know, it's got some finer uh grain stuff, but it also importantly is from the soil resin had a tree root going through it, so a conifer tree root and several tree roots.
• 22:52
  SPEAKER_02: So you take these soil samples and they basically like flush epoxy through them so that you can make a mount of the soil sample, and then they take the soil with epoxy kind of solidifying it, and then you could do imaging on it and just kind of look at what was happening.
• 23:06
  SPEAKER_02: What are the grains look like?
• 23:08
  SPEAKER_02: And there's this amazing image where there's two felt bar grains right next to each other.
• 23:12
  SPEAKER_02: One felt bar grain is touching a root, the tree root is actually touching it, and the other felt bar grain is not touch the root.
• 23:20
  SPEAKER_02: The one that's not touching the root is completely fine.
• 23:23
  SPEAKER_02: Looks like a normal feldspar grain, you can see zoning in it even, like totally cool.
• 23:27
  SPEAKER_02: The one touching the root, I wouldn't even recognize the feldspar grain.
• 23:30
  SPEAKER_02: Like, this looks like it has been completely rotted out.
• 23:33
  SPEAKER_02: It looks like a rotted log, you know.
• 23:35
  SPEAKER_02: I I don't know what image, what did you think of when you saw this like former feldz bar grain?
• 23:39
  SPEAKER_01: Yeah, we were talking about it actually before we came on, and and you described it one way, and I didn't recognize your word.
• 23:45
  SPEAKER_01: You know, you you called it like this kind of mesh, or I don't know if you meant mush.
• 23:49
  SPEAKER_01: I I really was confused by that.
• 23:51
  SPEAKER_01: To me, it was more like a uh um like an etching kind of that's a good one.
• 23:57
  SPEAKER_01: Yeah, totally.
• 24:01
  SPEAKER_01: So that's kind of how I think of it.
• 24:03
  SPEAKER_01: You know, you you imagine like dropping some acid on it and it just finds its way and it just kind of etches down into the face of the crystal.
• 24:11
  SPEAKER_02: That's a good description, yeah.
• 24:12
  SPEAKER_02: It's like the entire grain has been etched out.
• 24:14
  SPEAKER_02: It looks like a it looks like a you know, a steel building that hasn't been filled in yet.
• 24:19
  SPEAKER_02: It's just the it's just like a it's just the lattice structure left behind.
• 24:24
  SPEAKER_02: There's like nothing to it anymore.
• 24:26
  SPEAKER_02: The in interpretation is pretty obvious, like the tree root touching the feldspar, organic acids from the root that are being produced by the tree root have leached this feldspar and totally eroded this feldspar grain.
• 24:39
  SPEAKER_02: So that it's just pointing to really quite obvious evidence that organic acids, biology, therefore, rapidly increases the rate of chemical weathering.
• 24:48
  SPEAKER_02: I mean, that's one really nice example of this.
• 24:51
  SPEAKER_02: But there's a whole bunch of different types of acids.
• 24:54
  SPEAKER_02: The the mining literature has started to experiment with organic acids for uh leaching out minerals faster.
• 25:01
  SPEAKER_02: So if you want to you know target a specific mineral, say I want to dissolve only monozoide and I don't want to dissolve the other stuff.
• 25:08
  SPEAKER_02: You could maybe experiment with different organic acids to target that one mineral, basically.
• 25:14
  SPEAKER_01: So um oh the that was a really interesting part.
• 25:18
  SPEAKER_01: These kind of um uh what were they called?
• 25:21
  SPEAKER_01: These um organomarkers, right?
• 25:24
  SPEAKER_01: That were based upon these kind of elements that would concentrate, right?
• 25:31
  SPEAKER_01: They only would concentrate due to certain acids.
• 25:34
  SPEAKER_01: Um and so they were able to then deduce kind of the plant history of that area based upon the concentration of these these what are the elements, Jesse, that were these organomarkers.
• 25:46
  SPEAKER_02: So Yeah, iron, the ones that were lit that that that I've seen listed, there's probably more, are things like iron, phosphorus, and yttrium are ones that are and this is kind of a cool study.
• 25:58
  SPEAKER_02: People have gone to look to look at just basically river chemistry and said, okay, let's look at the river chemistry, let's look at the the carbon in the river, the total organic carbon or the dissolved organic carbon.
• 26:09
  SPEAKER_02: So basically, how much life is happening in the river basin?
• 26:15
  SPEAKER_02: And so let's look at one that has a lot of carbon and one that has a little bit and say, okay, this is one river system that has a lot of life happening in the in the river basin.
• 26:25
  SPEAKER_02: There's another one that does not have a lot of life with the same underlying rock composition, the one with life has a lot more iron, phosphorus, and uterum in the river water, dissolved in the river water.
• 26:35
  SPEAKER_02: So the idea being that if you look at a sediment back in time and you see lots of iron, phosphorus, and nutrium in this sediment, you could say, oh, there was probably life, you know, on the surface, on the land surface.
• 26:47
  SPEAKER_02: This was a forested area as opposed to maybe some sort of desert area or high mountain region without plant life.
• 26:53
  SPEAKER_02: So those are kind of the organic marker stuff.
• 26:55
  SPEAKER_02: And it's it's uh it's a really interesting approach to this because to the the sort of forward-looking thing here, Chris.
• 27:03
  SPEAKER_02: I I know there's several companies, I mean upwards of dozens of companies that have been started that are kind of quote unquote in the biomining space, which is not all focused on this enhanced dissolution with organic acids, but they are in some way using biology and perhaps even tuning biology to find or enrich specific elements.
• 27:26
  SPEAKER_01: So that's that's a lot of and importantly some rare earth elements.
• 27:31
  SPEAKER_02: Importantly, some rare earth elements, specifically, you know, a lot like several of the rare earth elements get enriched and mobilized with these organic acids.
• 27:39
  SPEAKER_02: Um, things like copper.
• 27:40
  SPEAKER_02: There's this thing called an Irving Williams series that goes back to the 1940s.
• 27:44
  SPEAKER_02: People have documented this.
• 27:46
  SPEAKER_02: That is kind of the the order that metals bond with different organic acids or ligands, and basically the stability of that bond, metal to uh ligand or organic acid, copper is usually the highest.
• 27:59
  SPEAKER_02: And so that's really interesting because copper is a something we need a lot more of in society.
• 28:04
  SPEAKER_02: So people have been targeting, you know, this, and this is kind of one of the principles behind some types of supergene enrichment, copper deposits, is is kind of this biologically mediated enrichment process.
• 28:15
  SPEAKER_02: So you could separate like copper from cobalt, for instance, using biology with this this sort of series.
• 28:21
  SPEAKER_02: So it's a totally interesting space.
• 28:23
  SPEAKER_02: It's seeing a lot of activity right now in the the company creation and uh research, sort of uh fundraising side right now to to focus on these these sort of targeting aspects.
• 28:34
  SPEAKER_02: And I don't know, I it's another aspect of like geochemistry that's just fantastic.
• 28:39
  SPEAKER_02: It is just so interesting to think about these things.
• 28:42
  SPEAKER_01: Do we have any any idea, you know, how viable is this in terms of solving some of our rare earth element or copper problems?
• 28:51
  SPEAKER_01: I mean, this certainly is changing the way we look for these things, right?
• 28:56
  SPEAKER_01: But how what kind of concentrations are we thinking?
• 29:00
  SPEAKER_02: Is this so there's a couple aspects that's uh I don't really know.
• 29:04
  SPEAKER_02: I mean, I to I mean I'm not gonna try and predict the future here with these things.
• 29:09
  SPEAKER_02: I think some of them are some of these these ideas are actually getting traction with major mining companies.
• 29:15
  SPEAKER_02: So major mining companies are running trial runs of these products.
• 29:19
  SPEAKER_02: And I I wouldn't say that any of them have become like deeply entrenched in the the they're not normal operations for any industry yet.
• 29:26
  SPEAKER_02: There's three aspects that I think are really interesting though to this space.
• 29:29
  SPEAKER_02: One is the tuning of biology, like creating different, you know, bacterial types that that are very specific to copper or very specific to nickel or something like that.
• 29:39
  SPEAKER_02: So really the kind of bioengineering side of this, and you know, creating your thing and you're creating your kind of melting pot of biology plus your ore rock and dumping that in and getting some reaction to happen.
• 29:51
  SPEAKER_02: That's a really interesting space, very active space.
• 29:53
  SPEAKER_02: There's another one that's kind of the exploration space where people are going around, and even like in Canada, for instance, they're going around actually cutting tree, the tippy tops of trees, and measuring the metal content of those things and saying, hey, this is actually grabbing a sample of the soil underneath it.
• 30:11
  SPEAKER_02: So actually, I don't need to sample soils for exploration, I don't need to look at groundwater, I don't need to look at rocks, I could just sample the tree tips.
• 30:17
  SPEAKER_02: I can go around a helicopter, grab the tree tips, and I'll actually get an idea of what the rock type is underneath if there's a copper deposit or if there's a nickel deposit underneath.
• 30:26
  SPEAKER_02: Like, that's kind of interesting.
• 30:29
  SPEAKER_02: That's super interesting for looking for deposits.
• 30:31
  SPEAKER_01: That's crazy, to be honest with you.
• 30:33
  SPEAKER_02: You know, real quick, Chris, let me let me finish.
• 30:35
  SPEAKER_02: The third interesting space is like a mineral processing one.
• 30:39
  SPEAKER_02: Um, using these organic acids to dissolve selectively dissolved minerals or speed up chemical weathering, which is carbon sequestration, using biologically produced acids to do mineral dissolution selectively to get rare earth elements out of rocks or to maybe draw down more CO2 than we would normally be able to do, speed up reactions that we want to do.
• 31:02
  SPEAKER_01: And that, Jesse, was where I at the very outset said that, you know, we've always talked about carbon diox carbon dioxide setting the thermostat.
• 31:11
  SPEAKER_01: That's that's our dial.
• 31:13
  SPEAKER_01: Um, but then looking at it in terms of, well, okay, but weathering with higher rates of weathering, and now we've looked at how biology plays into that, that speeds up the drawdown.
• 31:22
  SPEAKER_01: So it's this kind of negative feedback loop, right?
• 31:25
  SPEAKER_01: Where weathering is the air conditioner for our planet, if you will.
• 31:29
  SPEAKER_01: You know, weathering is this negative feedback loop.
• 31:32
  SPEAKER_01: You know, you increase carbon dioxide, you increase temperatures, that increases weathering, and then weathering draws it back out.
• 31:40
  SPEAKER_01: So it's this negative feedback loop.
• 31:41
  SPEAKER_01: So maybe weathering can be thought of as the this kind of negative feedback hero.
• 31:46
  SPEAKER_02: Yeah, yeah.
• 31:46
  SPEAKER_02: No, I like that.
• 31:47
  SPEAKER_02: You know, because I think I always think I always have thought of it as just pure silicate weathering, like no life involved.
• 31:54
  SPEAKER_02: It's water, it's carbon dioxide dissolved in water, that's the acid.
• 31:58
  SPEAKER_02: Uh, you know, that breaks down pyroxines or whatever, and I've thought of it just from that process.
• 32:03
  SPEAKER_02: But actually, the feedback loop is if land plants start to colonize the land, that decreases physical weathering, decreases fresh rock, which decreases the physical weathering process, but it dramatically increases the chemical weathering aspect.
• 32:17
  SPEAKER_02: And so there's actually like a push-pull balance there too.
• 32:20
  SPEAKER_02: The teeter-totter of physical and chemical weathering is kind of governed by life in a way as well, right?
• 32:26
  SPEAKER_02: Like we know that if we have a hill slope and we remove all the plants, there's going to be more physical weathering, which is more fresh rock exposed, which kind of keeps the weathering process active.
• 32:36
  SPEAKER_02: But if we put plants on a hill slope that doesn't have plants on it, it'll lock the soil in place more, it'll hold stuff there, less physical weathering, but more chemical weathering because we've got all these organic acids now, we've got all you know much more uh water percolating through the system.
• 32:52
  SPEAKER_02: So it strikes me that Earth is amazing.
• 32:55
  SPEAKER_02: There's all these feedback loops that that kind of regulate, they kind of internally regulate themselves in some way, and it is utterly complicated.
• 33:02
  SPEAKER_02: Like we are just scratching the surface.
• 33:05
  SPEAKER_02: I mean, I read some of these papers, I consider myself a geochemist.
• 33:09
  SPEAKER_02: I read some of these papers, I'm like, I have no idea what they're talking about.
• 33:11
  SPEAKER_02: This, like, this is gonna take me hours to figure out exactly what's going on here because this is really complicated chemistry, and it sits at an intersection between life, geological time scales, rock compositions, different minerals.
• 33:24
  SPEAKER_02: I even read a paper recently, Chris, where feldspars are not off the same when it comes to organic acids.
• 33:29
  SPEAKER_02: Like some feldspars are attacked way more, way more rapidly than other feldspars.
• 33:36
  SPEAKER_02: So, you know, it gets really complicated because you got a ton of different acids that can do interact with a ton of different minerals in this really dynamic landscape.
• 33:44
  SPEAKER_01: So your point also um that was a part of my inner conflict with this.
• 33:50
  SPEAKER_01: This paper was a slog, Jess.
• 33:51
  SPEAKER_01: Like this was not this was not uh like hey, I'm gonna sit down for 30 minutes and and just soak all this in.
• 33:59
  SPEAKER_01: Uh, it didn't work that way at all.
• 34:01
  SPEAKER_01: At least not for my little brain.
• 34:03
  SPEAKER_02: Um No, I I agree completely with you.
• 34:05
  SPEAKER_02: It takes it, you know, it uh it takes time to develop this expertise, which I think is to me, Chris, which is back to the educational aspect.
• 34:12
  SPEAKER_02: This is to me the one of the exciting parts is that anything that is deeply complicated requires expertise and requires time to develop that expertise.
• 34:22
  SPEAKER_02: Which that means is like you got to go to a good school where you get good training, you might have to do a grad degree in this type of stuff to really develop, to really hone the skills and develop that deep knowledge.
• 34:33
  SPEAKER_02: Like you can't do it in half an hour with Chat GPT or Claude sitting there, right?
• 34:38
  SPEAKER_02: Like that you're just not gonna be able to get to the level of understanding you need to.
• 34:41
  SPEAKER_02: So this really takes expertise, which to me is enhances the value of a really nice interdisciplinary degree from a good institution.
• 34:51
  SPEAKER_01: Um I agree.
• 34:53
  SPEAKER_01: I did think of I thought of our podcast, I don't know, from a couple of years ago at least.
• 34:58
  SPEAKER_01: Everything to me is a couple of years ago now, but when we did a an episode on how to read a paper, when I read this one, I that's I kept coming back to this.
• 35:07
  SPEAKER_01: I'm like, all right, you just gotta slog it out.
• 35:10
  SPEAKER_02: You just you know get down in with it, yeah.
• 35:13
  SPEAKER_02: Exactly, exactly.
• 35:15
  SPEAKER_02: No, no kidding, man.
• 35:16
  SPEAKER_02: I I agree completely with that.
• 35:17
  SPEAKER_02: Like, yeah, it's some of these are it's organic chemistry, it's it's uh rocks, rocks are complicated, man.
• 35:23
  SPEAKER_02: But it's interesting, man.
• 35:24
  SPEAKER_02: It's interesting, and I think it's important for kind of future stuff.
• 35:27
  SPEAKER_02: So I don't know what the title of this will be, Chris.
• 35:30
  SPEAKER_02: Um, we'll we'll uh we'll have to do that.
• 35:32
  SPEAKER_01: Okay, I'm just gonna say that you you threw out biology wins, and I don't think we can do that.
• 35:37
  SPEAKER_02: I agree with you.
• 35:38
  SPEAKER_02: That's too extreme.
• 35:39
  SPEAKER_02: We can't just say biology wins.
• 35:40
  SPEAKER_02: That's not right either, because biology is more important than we've maybe sometimes give it credit for, but it is a win.
• 35:46
  SPEAKER_02: I mean, come on, challenge.
• 35:48
  SPEAKER_01: The marriage marriage of geology and biology.
• 35:50
  SPEAKER_01: How about that?
• 35:51
  SPEAKER_02: Okay, all right.
• 35:52
  SPEAKER_02: Yeah, that's right.
• 35:52
  SPEAKER_02: Uh that's sounding better.
• 35:54
  SPEAKER_02: Yeah, that's sounding better.
• 35:55
  SPEAKER_02: There's no colon in there, Chris.
• 35:56
  SPEAKER_02: You love a good colon in your title.
• 35:58
  SPEAKER_02: I do love, I do love that.
• 36:00
  SPEAKER_02: Absolutely.
• 36:00
  SPEAKER_02: Colons and hyphens.
• 36:01
  SPEAKER_01: Love them.
• 36:02
  SPEAKER_02: Well, Chris, I think this is a deep topic.
• 36:04
  SPEAKER_02: We could go a lot deeper into it uh with some more reading and probably with interviewing some people.
• 36:09
  SPEAKER_02: I would love to get some of these um the people founding these the sort of bio mining companies on as well to to talk through this process and kind of relate some of the things they're doing, they're doing here.
• 36:19
  SPEAKER_02: So I would say let us know if you have any questions.
• 36:22
  SPEAKER_02: If you are interested in hearing more about this, if you're interested in deeper dives on this kind of topic, let us know.
• 36:27
  SPEAKER_02: We've got a contact us link on our website, plantgeocast.com, follow us on all the social medias at Plant GeoCast.
• 36:32
  SPEAKER_02: Download our Camp Geo Mobile app, first link in your show notes.
• 36:35
  SPEAKER_02: We've got the intro to geology, physical geology textbook online and audiobook form there, and a whole bunch of other content on a bunch of cool national parks and other cool topics.
• 36:46
  SPEAKER_02: So check that out and uh let us know what you think.
• 36:48
  SPEAKER_02: Cheers.
• 36:49
  SPEAKER_02: Peace.