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Granite Wars: The Debates That Built a Science · 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.
0:14
SPEAKER_01: Oh man, that's pretty good.
0:16
SPEAKER_01: Um, all right, Dr.
0:18
SPEAKER_01: Ackerson.
0:18
SPEAKER_01: How's it going, man?
0:19
SPEAKER_00: Good, Dr.
0:20
SPEAKER_00: Remink.
0:21
SPEAKER_00: How are you doing today, buddy?
0:22
SPEAKER_01: Good.
0:23
SPEAKER_01: We don't actually call each other that uh frequently.
0:27
SPEAKER_00: Exclusively make our wives call us.
0:29
SPEAKER_01: That's exactly right.
0:30
SPEAKER_01: Exactly right.
0:31
SPEAKER_01: Um, all right, so you have joined us before.
0:33
SPEAKER_01: Chris and I interviewed you a while back uh about granite, about granitoids.
0:38
SPEAKER_01: We you and I decided that we wanted to do something kind of deeper level, and this is a large part based on feedback from listeners.
0:46
SPEAKER_01: We get a lot of listeners that are like, we love the weeds, we want to spend more time in the weeds.
0:50
SPEAKER_01: So this is gonna be the weeds.
0:52
SPEAKER_01: Um, if you want, you the listener, if you want an introduction to igneous rocks, we'll give a little intro.
0:58
SPEAKER_01: But we have on their Camp Geo mobile app, Chris and I have recorded basically the you know intro level textbook there.
1:03
SPEAKER_01: So you can go listen to the intro to igneous rocks and and the basics.
1:07
SPEAKER_01: What is granite, what is basalt, etc., that type of stuff.
1:09
SPEAKER_01: Go first link in the show notes, go there, listen to that.
1:13
SPEAKER_01: But this episode is not that.
1:15
SPEAKER_01: We're gonna go a little bit more into the weeds here as part of a series on granites and grenatoids because it's a really exciting time in this field, I think.
1:22
SPEAKER_01: In the field of petrology, granite petrology, which is your field, Mike, my field uh in a research space.
1:28
SPEAKER_01: It's a really exciting time.
1:30
SPEAKER_01: And you are uh I I would say, dare I even say, on some of the forefront of why it's exciting at the moment and thinking about these problems.
1:38
SPEAKER_01: So you also give an amazing historical view of uh the history of granite research.
1:46
SPEAKER_01: So this is the intro episode to the series we're gonna do, and we wanted to focus on the history of the field.
1:50
SPEAKER_01: So why is the history of the field important in your mind?
1:55
SPEAKER_00: Yeah, you know, when we were talking about this kind of oh, let's let's let's force people to listen to us talking to weeds about granites for a couple episodes, you know.
2:03
SPEAKER_00: Yeah, exactly.
2:05
SPEAKER_02: How exciting.
2:06
SPEAKER_00: I I think one of the ways to get people engaged in and interested in in granites is the fact that they play a central role in the evolution of our thought on the geosciences writ large.
2:21
SPEAKER_00: Like granites since uh the founding of our field have been a critical component of every kind of major argument or discussion within the geosciences.
2:32
SPEAKER_00: And so to give the historical perspective on saying, oh, well, okay, so why do I care about granites today?
2:39
SPEAKER_00: Uh, well, maybe part of that can be um supplemented by an interest in how they've played a role in the evolution of our field.
2:47
SPEAKER_00: And as we talk today, I think some people that, if you're a geoscience nerd, you may have heard of some names will pop up, but there will definitely be at least one name that I'm gonna mention that you might not have thought about in terms of the geosciences and granites.
3:00
SPEAKER_00: And this guy is intimately related to the evolution of our field in the 1800s.
3:05
SPEAKER_00: So, you know, giving a bit of historical context, I think is really fun and interesting.
3:09
SPEAKER_01: Yeah.
3:10
SPEAKER_01: You do this exceptionally well in introduction to talks that you give.
3:13
SPEAKER_01: You kind of give this historical view um at the outset, and it is really important.
3:17
SPEAKER_01: You're exactly right.
3:18
SPEAKER_01: It's important, it has been central to geology.
3:20
SPEAKER_01: The discussion about granites is central to geology, and we're gonna talk about reasons why, like why is granite so central to geology, but let's define granite first before we get into that.
3:32
SPEAKER_01: Um, so a large part of this series is going to be focused on granite, the not the strict definition.
3:39
SPEAKER_01: There is a strict definition of granite, which if you look at an igneous rock, an intrusive igneous rock, so coarse-grained igneous rocks, the idea being this is magma that crystallized underneath the surface slowly.
3:49
SPEAKER_01: If you look at igneous rocks, you can just take that and look at the minerals and say, all right, I'm only gonna focus on quartz and feldspar.
3:56
SPEAKER_01: Take the quartz and feldspar, and the relative proportions of quartz to alkali feldspar to plagioclase gives you the name of the rock.
4:03
SPEAKER_01: And that granite has a really strict definition in that name.
4:06
SPEAKER_01: We're not gonna be focusing, we're not gonna be using the word granite strictly in this conversation.
4:11
SPEAKER_01: More accurately, we would probably say granitoids, which means like igneous rocks that have a high silica content, SiO2 over 68% of the total amount of the rock is SiO2.
4:23
SPEAKER_01: We are probably not gonna be very strict about uh very rigorous about saying granitoid instead of granite.
4:29
SPEAKER_01: So when we say granite here, we're referring to granitoids typically.
4:32
SPEAKER_01: Um, but that's the definition of the rock that we're dealing with here.
4:36
SPEAKER_01: So let me maybe give an introduction to this topic or why I think let me pause it to you why I think granite is so central to the field of geology.
4:47
SPEAKER_01: And we've read a couple papers here, um, a review of granite concept through time and Earth Science Reviews from just this year by a large group, um several people in Europe, uh Spain and Germany.
4:59
SPEAKER_01: And then we also read a paper by Mike Atherton, who's uh in Liverpool on granite magmatism, which goes back to 1993.
5:06
SPEAKER_01: And they're really nice papers that have a kind of an overview of the history of the field.
5:10
SPEAKER_01: But in particular, this Earth Science Reviews paper had a lot of diagrams that kind of show geological maps, early geological maps of various regions.
5:22
SPEAKER_01: And these are going back to really the 1700s, these maps or these sort of geological sketches.
5:29
SPEAKER_01: And what you see is that Chris and I talked just recorded an episode a while back about mountain building events and what you see as you drive into a mountain range.
5:39
SPEAKER_01: So you start in flat sedimentary plains, you start seeing little folds as you get close to the mountains.
5:45
SPEAKER_01: The first front range of the mountains is often sediments.
5:48
SPEAKER_01: As you get into the interior of the mountains, you often see igneous rocks in the interior core, and that's what these sketches show is igneous rocks in the interior core.
5:56
SPEAKER_01: And that's what people observe going back to the 1700s was that sort of systematic framework.
6:01
SPEAKER_01: So you can see if you're an early worker in the the new, newly born field of geology, you'd be like, Oh, granite is pretty important for more forming mountains.
6:13
SPEAKER_01: How do mountains form?
6:14
SPEAKER_01: How do granites form?
6:15
SPEAKER_01: Because they're always in the core of the mountain range.
6:18
SPEAKER_01: Is that a good framing to you?
6:19
SPEAKER_01: Like to me, that that that makes sense, that that logic, why granite's important and intricately linked to all of geology, but it that's probably not the whole story.
6:27
SPEAKER_01: So, what do you think?
6:29
SPEAKER_00: Yeah, no, yeah, I I I agree.
6:30
SPEAKER_00: And you know, that's that's that's what I think is another interesting aspect of geology and the history of geology is that it's it's rooted in just pretty basic observations, right?
6:42
SPEAKER_00: You know, so like you're saying, granites, if you go into a mountain range, granites are kind of the roots of mountain ranges.
6:50
SPEAKER_00: You know, Mount McKinley is a massive blob of granite, and all around it is a bunch of sedimentary rocks, right?
6:58
SPEAKER_00: You know, that's kind of a first-order observation, is that these granites kind of form the cores of mountains.
7:03
SPEAKER_00: And and you know, just to talk briefly about the the bring it back to this like kind of history of geology and the and the philosophy of geology stuff, too.
7:12
SPEAKER_00: You know, it's uh an observation that is made in a time and space, right?
7:17
SPEAKER_00: So if you go out in the 1700s and you look at a bunch of flat-lying rocks and you go closer to the mountains, you see some folded rocks, and you see grass at the cores.
7:26
SPEAKER_00: You know, you are going to interpret those rocks within the context of science and the society that you have at that time.
7:34
SPEAKER_00: So in the 1700s, the field of geoscience was a lot different than it is today.
7:40
SPEAKER_00: You know, we have we have we have plate tectonics, a plate tectonic framework today, right?
7:46
SPEAKER_00: They didn't have that back then.
7:47
SPEAKER_00: And so, you know, you're exactly right.
7:49
SPEAKER_00: So maybe do you want to just like rewind the clock 300 years?
7:53
SPEAKER_01: Let's do it.
7:54
SPEAKER_01: Let's go back then.
7:55
SPEAKER_01: What did we know then?
7:56
SPEAKER_01: What what were the words people were using to describe the ideas here?
8:00
SPEAKER_01: Uh like yeah, give it give us the give us the long form of this.
8:04
SPEAKER_00: Yeah, so maybe we'll frame this in terms of controversies.
8:07
SPEAKER_00: Okay, because people love controversy, right?
8:10
SPEAKER_00: Oh, yeah.
8:10
SPEAKER_00: So uh and you know, different competing scientific models breed like really some fun drama, and you know, there's there's some quite some characters in the geosciences.
8:23
SPEAKER_01: You know what I appreciate?
8:24
SPEAKER_01: One thing on that, Mike, is I appreciate going back to the older literature, is it was less formal in a way, it was still very formal, but it was more personal.
8:32
SPEAKER_01: It was formal but personal, let's say.
8:34
SPEAKER_01: So there's a lot of like reading these old papers, they refer to each other by name a lot.
8:38
SPEAKER_01: Like so-and-so said this, and I respectfully disagree with this because of etc.
8:44
SPEAKER_01: etc.
8:44
SPEAKER_01: etc.
8:45
SPEAKER_01: And they wouldn't often say respectfully, but there was like it was a very personal space because the field was smaller, so it was individuals arguing with each other, uh, as opposed to this big community, this sort of you know, hive mentality kind of thing.
8:58
SPEAKER_01: So, I mean, it they're really fun to read these papers because of that process, but still everybody liked a good debate.
9:04
SPEAKER_01: So, uh anyway.
9:05
SPEAKER_00: Oh, yeah, they did.
9:06
SPEAKER_00: And if we if we get around to it, I have a quote here from one of the fathers of Rfield, Norman Bowen, from a letter he sent to a colleague.
9:14
SPEAKER_00: Oh, awesome.
9:15
SPEAKER_00: Yeah, I think that's a good idea.
9:16
SPEAKER_00: That is exactly in line with this.
9:18
SPEAKER_01: We definitely got to get to that.
9:20
SPEAKER_00: Um, but yeah, but you know, that that's the 1940s.
9:23
SPEAKER_00: If we go to the 1780s, I think what one of the big um, and this is like geoscience-wide, and it just happens to relate to granites.
9:32
SPEAKER_00: So one of the big debates at the time was this idea of Neptunism and the competing idea of Plutonism.
9:41
SPEAKER_00: So Neptunism was this notion uh championed by a guy named Um Abraham Werner, and the basic idea, like you're saying, if you go out and you look at uh flat lying sediments, and then you have some more folded sediments, and then you have granites on the bottom, and you have volcanoes uh uh piercing through all that stuff.
10:04
SPEAKER_00: The conceptual framework that he had and others had was based on this idea of a global ocean.
10:10
SPEAKER_00: So basically, we had a global ocean that was in some ways rooted in a religious conception of the world.
10:17
SPEAKER_00: So the idea was basically that the granites and stuff precipitated out of this global ocean first, and then subsequently other layers of material deposit on top of that granite, and then volcanoes shot up from uh fiery hells below between all that stuff.
10:32
SPEAKER_00: So this is kind of this basic framework was a global ocean, relatively fast, you know, say in the order of thousands of years, precipitation of all the rocks that we see from said global ocean.
10:43
SPEAKER_00: And that was a not an unreasonable like interpretation within the societal framework at the time, right?
10:50
SPEAKER_00: Like that kind of to the first order makes sense.
10:53
SPEAKER_00: Yeah.
10:54
SPEAKER_00: So that was a Neptunism idea.
10:56
SPEAKER_01: And the name Neptunism comes from the Roman god of the sea, Neptune, right?
11:00
SPEAKER_01: So the Neptunism is everything's kind of precipitating from the ocean or getting deposited, and and igneous rocks are lumped into that everything category.
11:08
SPEAKER_01: So igneous rocks would not be called igneous rocks, they would be called precipitates from the ocean in the Neptunist uh view, right?
11:16
SPEAKER_00: Yeah, crystalline precipitates.
11:18
SPEAKER_00: You know, they they have they have words for it in German that I don't even dare try to pronounce.
11:24
SPEAKER_01: Fair enough, fair enough.
11:25
SPEAKER_00: I can only do German if I have uh an Arnold Schwarzenegger accent, and of course he's Austrian, so I can't win.
11:35
SPEAKER_01: Oh, that's great.
11:36
SPEAKER_00: Yeah.
11:36
SPEAKER_00: So so yeah, so this is the Neptunist.
11:39
SPEAKER_00: This is kind of like the leading idea, kind of at the one of the birth points of geology.
11:44
SPEAKER_00: You know, it has a long history going back thousands of years because everybody lives and deals with rocks, right?
11:49
SPEAKER_00: So you know, it's not like geology just sprung up in the 1700s.
11:53
SPEAKER_00: People were thinking about rocks for a long time.
11:55
SPEAKER_00: So this was like this kind of predominant idea.
11:58
SPEAKER_00: But one of the key points from this Neptunism idea is that granites are older than all the rocks on top of them, because they are primitive and they crystallize at the bottom and everything precipitated on top of them.
12:12
SPEAKER_00: So then along comes this guy, James Hutton.
12:15
SPEAKER_00: He is often referred to as like the father of geology.
12:19
SPEAKER_00: Scotland produced a lot of really good geologists, totally, right?
12:22
SPEAKER_01: And uh Hutton has an unconformity, probably the most famous unconformity.
12:26
SPEAKER_01: There's the Siker Point one, there's a couple of them uh from Hutton's work there.
12:30
SPEAKER_01: So anyway, yes, continue.
12:32
SPEAKER_01: So Hutton comes around, and so Neptunism was the original interpretation, right?
12:36
SPEAKER_01: Like the earliest one, slightly before this sort of Plutonism thing.
12:40
SPEAKER_00: Yeah, within like modern, you know, Western context, this was kind of like the major predominant theory at the birth of geology.
12:48
SPEAKER_00: And then James Hutton comes along, and he was in pretty a vigorous debate with these Neptunists, you know.
12:54
SPEAKER_00: Uh Werner was one of them, but there were other other people as well.
12:58
SPEAKER_00: And James Hutton was a guy who would, you know, hike around on rocks.
13:02
SPEAKER_00: You know, you mentioned Sycrett Point.
13:03
SPEAKER_00: This is this famous, you know, angular unconformity that has a huge time span between it.
13:10
SPEAKER_00: Uh but since we're talking about granites, I'm going to focus on the one thing that he did, which was with related to granites, which was he was hiking out this place is called Glen Tilt.
13:20
SPEAKER_00: There's this river valley, and like a little stream bed, actually.
13:24
SPEAKER_00: And there's a bunch of sedimentary rocks, and there's granites.
13:27
SPEAKER_00: But what he noticed there is all these granites were intruding these meta-sedimentary rocks.
13:35
SPEAKER_00: So a bunch of little fingers of granite cracking through and intruding into all these other rocks.
13:39
SPEAKER_00: And then so the logical extent there is that, well, if granites are supposed to be older, they're not going to be cracking and intruding through these other things, right?
13:48
SPEAKER_00: So this is where the idea, I mean, this is like to the modern brain, it it seems like so obvious.
13:55
SPEAKER_01: Yeah, but you know, I think that's true for geologist people, but I I find these things, these sort of classic rules of geology, you know, cross-cutting relations is the one we're referring to here, right?
14:05
SPEAKER_01: Where the the thing that cross-cuts is younger because the thing that is cross-cut had to be there first, right?
14:11
SPEAKER_01: That that's obvious when you point it out, but I don't think it's intuitive.
14:15
SPEAKER_01: I don't think you like kids recognize that as like being truth.
14:20
SPEAKER_01: So it is, it does require it's something that once you point it out, you're like, oh, that makes a ton of sense.
14:26
SPEAKER_01: But it's not something you kind of stumble upon on your own necessarily.
14:29
SPEAKER_01: So at least what I I've found in teaching, you know, the intro-level physical geology classes, these things have to be pointed out to people.
14:35
SPEAKER_01: But it's a really important observation, right?
14:37
SPEAKER_01: In this this sort of Neptunist versus um the you know, the other concepts at this time versus Plutonism.
14:43
SPEAKER_00: So yeah, yeah, yeah.
14:44
SPEAKER_00: You know, I I agree with you completely on this, like kind of things like there, you know, it's obvious uh in the rearview mirror kind of things.
14:51
SPEAKER_00: Like, you know, I because I'll talk about you know, right here, I just this is the Jack Hills, this is the rock that contains the oldest earth materials.
14:58
SPEAKER_00: And so, you know, I'll hand people this rock and I'll say, you know, this rock is three billion years old, but the minerals inside of it are much older than three billion years old.
15:06
SPEAKER_00: And they say, Wait, what do you mean?
15:08
SPEAKER_02: Yeah, what?
15:08
SPEAKER_00: Well, you know, it's a sedimentary rock.
15:10
SPEAKER_00: And so, you know, the analogy I always say is, well, if you go to a beach right now, that beach is made up of minerals that are all older than the beach itself, right?
15:19
SPEAKER_00: And so if you just took that beach and turned it into a rock, the age of the rock would be today, but the crystals that are in there could be billions of years old.
15:25
SPEAKER_00: That's basically the same thing.
15:27
SPEAKER_02: Same thing, yeah, yeah.
15:28
SPEAKER_00: It makes sense, but you just have to like if somebody tells it to you, then it instantly just kind of clicks in the parts.
15:32
SPEAKER_01: Yeah, yeah.
15:33
SPEAKER_01: It's not a hard concept, but it needs to be taught to you or told to.
15:35
SPEAKER_01: Yeah, okay, exactly.
15:37
SPEAKER_01: So this is Hutton, um, and he's walking around and sees the granite inter uh, you know, injecting kind of into the cracks in the sediment surrounding it.
15:45
SPEAKER_01: Okay.
15:45
SPEAKER_00: Yeah.
15:46
SPEAKER_00: So that's one of the key observations that kind of solidified this different idea, which is that m granites are actually magmas or or liquid rocks intruding into other rocks.
15:58
SPEAKER_00: So this was kind of this burst of this Plutonism movement, and that was one of one of many death knells for the Neptunist movement.
16:06
SPEAKER_00: So, you know, I think the Neptunists get a lot of like, oh, you can't believe how silly the Neptunists were.
16:12
SPEAKER_00: But, you know, honestly, like I you can get it.
16:15
SPEAKER_00: I understand like the way that they were thinking about these things, you know, and like there's one place uh on the beach in Scotland where there's like a bunch of dolo stones, like some like kind of like muddy, kind of crappy sedimentary rocks that have like fossils in them, but they're intruded by like basalt seals and things.
16:33
SPEAKER_00: And honestly, like unless you're have a really keen eye, the difference between two microcrystalline dark rocks is like extremely different.
16:42
SPEAKER_00: Yeah, oh my god.
16:43
SPEAKER_00: Yeah, you know.
16:45
SPEAKER_01: Identifying these things sometimes is really, really hard to do in the field.
16:48
SPEAKER_01: I mean, I remember in my uh my my qualifying exam, you know, the third or three-hour PhD oral exam that's kind of like a go no-go uh exam for are you gonna do a PhD or not?
16:58
SPEAKER_01: I got handed a rock to identify, and it was a high it was a pretty highly grade, highly metamorphosed tonalite or granodiorite, really.
17:09
SPEAKER_01: Um, from you know, it was an Eorchean rock, 3.8 billion years old, from Issue Supercrustal Bell.
17:14
SPEAKER_01: But it was like an igneous rock.
17:15
SPEAKER_01: It had been metamorphosed to high temperature, and it was really hard to tell the difference between that and a sandstone or a quartzite.
17:21
SPEAKER_01: It's like this could be a quartzite or this could be a high grade metamorphosed igneous rock.
17:26
SPEAKER_01: Like, so of course, walking around 300 years ago, it'd be way harder because we don't have any of that background.
17:32
SPEAKER_01: This is just it's not it not easy all the time.
17:34
SPEAKER_01: Geology is not an easy field to make those observations and and make reliable interpretations of the observations.
17:41
SPEAKER_01: So anyway, yeah, I agree with you completely.
17:44
SPEAKER_00: Yeah, and so with hindsight, we're like, oh, you couldn't so you so you think that that basalt could have been the same thing as this rock that has fossils in it, but I mean I could easily have made made that mistake myself.
17:57
SPEAKER_00: Absolutely, absolutely.
17:58
SPEAKER_01: And then you know, a hundred years we'll look back and think, oh my goodness, they actually thought this, you know.
18:02
SPEAKER_01: Uh there's no doubt that what idiots.
18:05
SPEAKER_01: I know, I know, absolutely.
18:06
SPEAKER_01: Okay, so Hutton comes along and Plutonism uh becomes this this competing battle between Plutonism and Neptunism.
18:13
SPEAKER_01: You know, how long does that last and what's the what what's the end state between them?
18:17
SPEAKER_00: I mean, we know Plutonism ends up winning, but I think Neptunism pretty rapidly dies off at that point, you know.
18:24
SPEAKER_00: I mean, it's it's not just these Ignis rocks and Glenn tilt.
18:28
SPEAKER_00: There's a series of observations that are made by people across Europe that really kind of put the death knell in the Neptunist world.
18:38
SPEAKER_00: So one of the things that is kind of missing from this particular conversation is is time.
18:45
SPEAKER_00: And you know, obviously time is so important for us as geologists, but you know, both Neptunism and Plutonism could, to a certain extent, uh exist in a world where all the rocks we see were created over a couple of thousand years in in a global ocean or something.
19:00
SPEAKER_00: And so the the time component is still a bit nebulous here.
19:04
SPEAKER_00: And then so there's this kind of this crucial uh interperiod between you know these arguments in the 1700s and the early, I think about early 1800s, Neptunism was uh pretty much uh dawn and Plutinism was kind of this this major idea.
19:19
SPEAKER_00: But there's still kind of a gap between Plutonism and where we ended up having some more heated debates about grants in the 20th century.
19:28
SPEAKER_00: And and in that time, so if we go from the early 1800s to the mid to late later 1800s, one of the big movements, including Hutton and some other people, includes another famous geologist, Charles Lyell.
19:45
SPEAKER_01: Okay.
19:46
SPEAKER_01: Lyell.
19:47
SPEAKER_01: You know Chuck?
19:48
SPEAKER_01: Yeah, yeah, I know of him.
19:50
SPEAKER_01: I don't know him personally, but I know of him.
19:51
SPEAKER_01: Yeah, I've heard the name.
19:53
SPEAKER_00: So, you know, so Charles Lyell, of course, is one of the people who well, I said I apologize for saying of course, if you're a freaking nerd who's read all these things.
20:02
SPEAKER_00: Um, but so Charles Lyell is one of the people who comes up with this idea of uniformitarianism.
20:09
SPEAKER_00: And so, you know, uniformitarianism is this idea that geologic processes, mountain building events, the deposition of sediments happen over long periods of time, and that we can see rocks that are being deposited or eroded or built as volcanoes today, that we can use those to understand what's happening in the past.
20:33
SPEAKER_00: And this kind of also brings up the idea of deep time.
20:37
SPEAKER_00: So instead of having you know a global ocean from which everything precipitated in 6,000 years or something, we're talking about uh processes happening for hundreds of thousands or millions of years.
20:49
SPEAKER_00: So that is kind of this grand theory of uniformitarianism.
20:53
SPEAKER_00: And so, and part of this uniformitarianist idea is that if you have granite magmas intruding into rocks, that's not going to be an instantaneous process.
21:05
SPEAKER_00: That's gonna happen for over longer, long, very, very, very long periods of time.
21:11
SPEAKER_00: So, you know, granites are related to this uniformitarianist idea in that we have large bodies of granite that were intruded into the crust for really long periods of time, longer than like a couple thousand years.
21:24
SPEAKER_01: Right, right.
21:25
SPEAKER_00: So that's how granites kind of in a certain extent relate to uniformitarianism.
21:30
SPEAKER_00: Does that make sense?
21:31
SPEAKER_01: Yeah, absolutely.
21:31
SPEAKER_01: So we're kind of extending uniformitarianism's kind of separate idea based on uh, you know, largely based on sediments and looking at rivers and how much sediment's being dumped into the ocean, and then therefore how long does it take to create a big pile of sedimentary rocks, and then what happens when we have to tilt this and erode it and then redo it, you know.
21:49
SPEAKER_01: So these are things that take uh a long time.
21:52
SPEAKER_01: And then that just extends the l the time frame for plutonism to occur, basically.
22:00
SPEAKER_01: Yeah.
22:01
SPEAKER_01: And I think this is really so the kind of this is more of a blend as opposed to like two different ideas conflicting with one another.
22:07
SPEAKER_01: It's kind of a uh enveloping or you know reframing Plutonism in the context of uniformitarianism.
22:13
SPEAKER_01: So go back and say, oh, there's a granite there.
22:16
SPEAKER_01: Uh I see a volcano happening right now.
22:19
SPEAKER_01: Maybe that granite used to be the roots of a volcano or something, something along those lines in the uniformitarianist perspective.
22:25
SPEAKER_01: Okay, cool.
22:26
SPEAKER_01: And that brings us to the more modern, the sort of uh academic great-grandfathers of of you and I that that existed in the 1900s.
22:38
SPEAKER_01: Is that the next sort of major debate that we have with regard to granites?
22:42
SPEAKER_00: It it is, but I wanted to mention another important person around this time.
22:49
SPEAKER_00: So Charles Lyell had another a buddy, another Charles from the British Isles.
22:56
SPEAKER_00: Um, you may have heard of him.
22:58
SPEAKER_00: His name's Charles Darwin.
23:00
SPEAKER_01: Of the Beagle fame.
23:01
SPEAKER_01: I've heard of the Beagle Fame, yeah.
23:04
SPEAKER_00: Yeah, HMS Beagle.
23:05
SPEAKER_00: Yeah.
23:06
SPEAKER_01: So little little facto it.
23:07
SPEAKER_01: I don't know how how factual this is, but but uh Darwin was actually a geologist by training, right?
23:13
SPEAKER_00: Yeah, something like that.
23:14
SPEAKER_00: Yeah, like you know, I'm not gonna fact check you, but yeah.
23:17
SPEAKER_01: The words are are what what does that mean back in the day?
23:19
SPEAKER_01: But he was a naturalist who focused on rocks and then became I like to give my uh you know, my family a little bit of crap for the founder of their field, basically, and was you know was a geologist, yeah, exactly.
23:32
SPEAKER_00: Well, he actually wrote a he wrote a book about the geology of South America when they were traveling around in the Beagle.
23:39
SPEAKER_00: Yeah, so he wrote a book about it, and so he was corresponding with Charles Lyell this whole time.
23:45
SPEAKER_00: And so, you know, Darwin actually wrote about the granites of the Andes and the Andes, the other side, Brazil.
23:52
SPEAKER_00: So, you know, Darwin was writing about all these massive outcrops of granite along the coast of Brazil, and in communication with Charles Lyell, talking about you know, how could you form all these masses of granite that just extensive and everywhere?
24:08
SPEAKER_00: And of course, one of the things that Darwin struggled with was this time perspective, right?
24:14
SPEAKER_00: Like, how can you, if you are undergoing something like natural selection, it it requires a lot of time, it's not an instantaneous process, right?
24:23
SPEAKER_00: And so Charles Yell in conversations with him and this birth of this uniformitarianism idea actually provided a temporal window for Charles Darwin to understand these concepts of natural selection.
24:36
SPEAKER_00: So, you know, the geology and his geologic knowledge gave him the time frame within which he could develop this concept that is so important for our understanding of evolution.
24:48
SPEAKER_01: Another reason why geology is so important for biology, just kind of controls the whole thing.
24:53
SPEAKER_00: I know, I know.
24:54
SPEAKER_00: Hey, you know, plants eat dirt.
24:55
SPEAKER_00: So exactly.
24:58
SPEAKER_00: But yeah, so like that that was just that's just like a little a little Suzanne of interest for the biologists out there is, you know, like conversations with Charles Lyell between these two geology nerds kind of and the I mean, but that is like such a huge uh uh conceptual uh framework shift to go from thinking that everything you see is a couple thousand years to being you know, making observations and say, well, sedimentation rates are like we see them today.
25:25
SPEAKER_00: We're not talking a couple thousand years, we're talking millions of years.
25:28
SPEAKER_00: You know, that is such a I mean, you know, I think about the scientific discoveries that you or I have, and they're so minuscule relative to the to the grand scope of of like completely reframing the entire history of Earth.
25:42
SPEAKER_00: Like it's insane.
25:43
SPEAKER_01: Yeah, tell me you just you just get the opportunities for viable explanations just expand so much when time expands.
25:51
SPEAKER_01: So I agree with you.
25:52
SPEAKER_01: That like those things are just you could imagine the light bulb moment going on when they're kind of piecing these things together and being like, oh wait, if if things take that long and rocks take that long to form, then maybe you know there is enough time for evolution to happen.
26:07
SPEAKER_01: It's just a complicated.
26:09
SPEAKER_01: I mean, it is like a the veil is lifting, you know, the fog is lifted.
26:13
SPEAKER_01: And I could imagine that that sense of discovery, or like, hey, things are making sense now.
26:18
SPEAKER_01: And we get little hints of that in our job, luckily, but not at the scale of of those things, those those discoveries.
26:24
SPEAKER_01: So, all right, so so that leads us to you know, the time frame we're kind of we're we're we're verging on here.
26:30
SPEAKER_01: We've got uniformitarianism, we've got plutonism within that context, so we're kind of understanding igneous rocks.
26:35
SPEAKER_01: There's a lot of time for these things to actually occur and actually crystallize, they don't need to come from precipitation of an ocean.
26:41
SPEAKER_01: And then we we enter into a big debate period in the early night, late 1800s, early 1900s, right?
26:48
SPEAKER_01: Another kind of debate.
26:50
SPEAKER_01: What is that?
26:51
SPEAKER_01: What was the origins of this?
26:52
SPEAKER_01: What were the observations?
26:54
SPEAKER_00: Before we get to that big debate, which is I think like for us, like the framework, there's there is another shift that I want to mention before we get to that debate, which is this shift which aligns with the ability for people to uh understand the chemical composition of rocks, right?
27:12
SPEAKER_00: Because before all this, they were just looking at a rock and being, wow, that's a granite.
27:17
SPEAKER_00: That rock has crystals in it, and it's sticking itself into that other rock, so it must have been molten, so it must have been liquid and injected into another rock, but we don't know anything beyond that.
27:28
SPEAKER_00: And so there was uh concurrently with the evolution of our ability to do chemistry, people started doing the chemistry of rocks, and so you know, they also started making um petrographic slides so you could actually take a rock and slice it real thin, put it under a microscope and look at the minerals, and you could actually get out the chemical compositions of the rocks, and so that was really important because the reason I'm mentioning that is because that shift in chemical understandings is critical for the debate that happened in the 20th century.
27:58
SPEAKER_00: Because we go from primarily just field-based observations toward a chemical perspective on igneous rocks.
28:08
SPEAKER_00: And this is really kind of where like petrology and geochemistry are started, right?
28:12
SPEAKER_00: Because before that, you weren't doing chemistry, you were just kind of doing like, oh, this rock is sticking into that rock.
28:18
SPEAKER_01: Yeah, no, and this is like a parallel development, right?
28:21
SPEAKER_01: As the field of chemistry came to be, and then the field of geochemistry soon came soon after that.
28:26
SPEAKER_01: Um, you know, in the same way that the Manhattan Project spawned geochronology and and all the research into uranium decay and fission and nuclear nuclear physics, all that spawned geochronology.
28:38
SPEAKER_01: It's the same way here, just a generation earlier, a couple generations earlier.
28:42
SPEAKER_01: So no, it's exactly right.
28:43
SPEAKER_01: And our field is based on that, right?
28:45
SPEAKER_01: So, you know, you're a geochemist, I'm a geochemist.
28:48
SPEAKER_01: We use this information every day uh in our in our lives, and and understanding igneous rocks is really important to that.
28:54
SPEAKER_01: So we've got this new geochemistry framework or new new geochemistry toolkit, let's say it's a toolkit for understanding the rocks.
29:02
SPEAKER_01: Why does that spawn a new debate and what is the new debate?
29:06
SPEAKER_00: Yeah, so so it spawns this new debate, but there was always this small before we get into that debate, because this debate centers around this conundrum that people always had in their heads for hundreds of years.
29:22
SPEAKER_00: When we first started understanding the Plutonic or Plutonism debate, people had this issue, which was the fact that, okay, well, if you've got these granites that are intruding into other rocks, how do you do that?
29:39
SPEAKER_00: Like because the issue is that you don't just create space out of nowhere.
29:44
SPEAKER_00: So you have to somehow accommodate space for these rocks on the planet.
29:52
SPEAKER_00: So this was this little worm that was always in people's brains for like 150 years that we know is the room problem.
30:01
SPEAKER_00: How do you make room in the crust to put in a granite?
30:03
SPEAKER_00: If it's injected into the crust, how do you make room for it?
30:06
SPEAKER_01: And the room problem can be, I think, best explained by uh the movie The Core, which a generation of listeners will probably not understand uh this reference, but I think it was in a 1990s movie, right?
30:17
SPEAKER_01: Like at some point, yeah, somewhere in there.
30:20
SPEAKER_01: But basically they're drilling down to do something, I can't remember the plot line, but basically drilling down, and they fall into a cavity of diamonds in the earth.
30:27
SPEAKER_01: And this is, I think, is is I think that's the thing as they're drilling.
30:30
SPEAKER_00: I think there's like it was like amethysts in like the mantle or something.
30:33
SPEAKER_00: Then they get some diamonds.
30:41
SPEAKER_01: I remember like being an undergrad and being like, as soon as you start to figure out geology, then you get really cynical.
30:46
SPEAKER_01: You're like, oh, all these movies are wrong.
30:48
SPEAKER_01: You know, there's like there's this Pierce Brosner movie where he finds a trilobite, you know, in the volcanic cliff, and it's like that can't happen, you know.
30:55
SPEAKER_01: You get really cranky about movies, but this one is like you can't actually have a cavity in the earth because it you it it cannot survive the pressure.
31:05
SPEAKER_01: The pressure in the earth is too high.
31:07
SPEAKER_01: Think about you know, uh, if anybody's dove down into water before, you you know that it gets higher pressure down underneath the water.
31:15
SPEAKER_01: Now, if you were doing that under rock, the pressure is way higher.
31:18
SPEAKER_01: And so, you know, you just cannot have free empty space or room in the crust that exists for a long period of time, and it's and you can't have big vats of liquid really that exist in the crust for for any long period of time because it'll just get squished out, like it's not a stable configuration.
31:37
SPEAKER_01: So that's the room problem.
31:38
SPEAKER_01: Like, how do you get walk across the Sierra Nevadas and it's just miles and miles and miles of granite?
31:45
SPEAKER_01: How did that get there?
31:47
SPEAKER_01: Did it it can't just all come in as one big vat that sits there, you know, a couple kilometers down in the crust?
31:54
SPEAKER_01: What gives?
31:55
SPEAKER_01: So that's the room problem that you're describing, right?
31:58
SPEAKER_00: Yeah, exactly.
31:59
SPEAKER_00: So, what where does all that stuff come from?
32:01
SPEAKER_00: You know, you're talking about the core, how you get cranky, is it is a gel, just you know.
32:05
SPEAKER_00: Do you ever ruin movies for people?
32:07
SPEAKER_00: Like, I I find myself, you know, my wife will be like, Stop, don't nobody cares.
32:12
SPEAKER_00: Because it'll be like a movie that's supposed to be set, and like, you know, it's supposed to be set, you know, somewhere out east.
32:17
SPEAKER_00: And I'm like, they film that in Southern California.
32:20
SPEAKER_00: Like, I mean, that's Joshua Tree.
32:23
SPEAKER_00: Like, what are you talking about?
32:23
SPEAKER_00: What are you talking about?
32:24
SPEAKER_00: We're in Tennessee, and she's like, nobody cares, nobody cares.
32:29
SPEAKER_01: Shut up.
32:30
SPEAKER_01: That's funny.
32:31
SPEAKER_01: No, that's a good one.
32:32
SPEAKER_01: Yeah, this really doesn't match.
32:35
SPEAKER_00: Yeah, so so yeah, so this room problem was this little thing that's always in people's heads.
32:40
SPEAKER_00: Like, how the heck do we make space with these rocks?
32:43
SPEAKER_00: Okay, if they're magmas, how do we make space for them?
32:46
SPEAKER_00: And so that kind of leads to this other major debate in geology, especially surrounding granites called I guess it's would be the magmatists versus the granitizers.
33:00
SPEAKER_00: Uh in that one paper we were reading, it's called the Transformists.
33:05
SPEAKER_01: Okay.
33:06
SPEAKER_01: Magmatists.
33:07
SPEAKER_01: So what is magmatists?
33:09
SPEAKER_00: Magmatists are people that think that granitic rocks have a magmatic origin.
33:14
SPEAKER_00: So every granite you see was a magma that uh by some mechanism was uh intruded into the upper crust and cooled as a magma in the upper crust.
33:27
SPEAKER_00: So that's the magmatists, and the transformists or granitizers you know, I struggle to actually uh uh define what the debates of the transformists or granitizers was because it's uh kind of occluded.
33:40
SPEAKER_00: But basically their idea was that uh you have uh fluids.
33:48
SPEAKER_00: So if it's wet granitization, the idea would be like basically there's a bunch of fluids like water and stuff that are coursing through the crust at all times, and then those fluids or if it's dry without fluids, you do it just by diffusion, but that those uh things can actually transform uh the uh rocks that are in situ into a granite.
34:12
SPEAKER_00: So, like if you had a red sandstone like we have, like if you go out into the American West and you see these beautiful redbed uh sandstones, and you have a red granite like the Pikes Peak A-type granite there, the idea for these people is that basically you are coursing fluids through these sediments and you're transforming them into a granitic rock via replacement uh of that material.
34:40
SPEAKER_01: Yeah, okay.
34:41
SPEAKER_01: And and and I I want to come back to this.
34:43
SPEAKER_01: Let's let's let's nail this definition because I I want to come back to this, and I think this will center a bunch of the discussions that we have in in future episodes.
34:51
SPEAKER_01: So magmatists is this is magma.
34:53
SPEAKER_01: It's molten rock is moving up from somewhere down below, i.e., hotter, up to an area that's cooler, and there it crystallizes, right?
35:01
SPEAKER_01: And the room problem is the problem for the magmatist.
35:05
SPEAKER_01: The transformus or the granitizers would say you don't need to worry about room because it's not actually happening that way.
35:11
SPEAKER_01: It's all chemical.
35:12
SPEAKER_01: It's like fluids moving through or moving elements up and and they're depositing igneous rocks.
35:16
SPEAKER_01: So it's all it's kind of like the Neptunism thing, except you don't need an ocean.
35:20
SPEAKER_01: You just need fluid moving through the crust from hot down below to up shallower in some kind of way, right?
35:26
SPEAKER_01: Or the sediments, the sediments give off their water as they're metamorphosed and they kind of transform into transformism, transform into what we see at what looks like an igneous rock now, what is an igneous rock, but it it never was magma.
35:40
SPEAKER_01: So this this is the 1900s, late 1800s, early 1900s.
35:44
SPEAKER_01: This is where Norman Bowen comes in, and and I think is it fair to say that this magmatism versus transformism debate, magmatism eventually wins?
35:55
SPEAKER_00: Oh yes, yeah, yeah.
35:58
SPEAKER_00: That's very fair.
35:59
SPEAKER_00: Yeah, but you know, this one this is but you know, you know, in our discussions going forward, you know, there are consequences of of having one worldview become such firm canon.
36:11
SPEAKER_01: And we we'll talk about that later, but we'll come back to this because there's a lot of um you know observations that transformism does happen in some ways, maybe not at large scale, but like there's a lot of stuff moved by fluids in the crust, a lot of elements get moved around by fluids in the crust.
36:27
SPEAKER_01: Uh so I want to come back to this and get your perspective right at the end of this episode.
36:31
SPEAKER_01: But but um magmatism versus transformism, how does this debate, this is a debate that takes place over the 1900s?
36:38
SPEAKER_01: How does it end?
36:39
SPEAKER_01: What's the what are the main key points here?
36:41
SPEAKER_01: Who are the players?
36:42
SPEAKER_01: And I also want to hear your um your your note.
36:44
SPEAKER_01: The quote, yeah.
36:46
SPEAKER_00: So yeah, I mean, there's a lot of colorful characters, and like you're talking about, they used to have such vibrant conversations between each other, and they were and they were all really good with language, you know, it was a primary mode of it's always a primary mode of communication for us, but these guys would take a lot of time to write very thoughtful comments and things.
37:04
SPEAKER_00: But there's so one of the major proponents, like if you had to pick, you know, like the the Michael Jordan of the Grand Tizers, it would be this guy, H.H.
37:13
SPEAKER_00: Reed, who was a famous geologist, and he he has come up with all of these quotes that everybody's read about geology.
37:20
SPEAKER_00: Yeah, like if you just Google H.
37:22
SPEAKER_00: H.
37:22
SPEAKER_00: Reed quotes, you know, he's so good.
37:26
SPEAKER_01: I love these quotes.
37:27
SPEAKER_01: Yeah, they're awesome.
37:28
SPEAKER_00: But yeah, like you know, the more one of the more famous ones I'm paraphrasing it, but it's like, you know, he who was seeing the most rocks wins.
37:34
SPEAKER_01: Yes, exactly.
37:34
SPEAKER_01: Chris Bois loves this one, he just loves that quote and cannot stop talking about it.
37:38
SPEAKER_01: I like the one.
37:39
SPEAKER_01: Well, this guy was wrong, so yeah, granites are very big things, not hand specimens, like those things, like so.
37:47
SPEAKER_01: Yeah, exactly.
37:48
SPEAKER_00: Yeah.
37:49
SPEAKER_00: So he spent a lot of time in the field, and you could convince yourself going in the field of some of these observations.
37:56
SPEAKER_00: So, you know, one of the things that the the transformationists really held on to was the fact that if you look at what we would call now like a high grade, like migmatized gice or a really high temperature and pressure rock that ended up getting so hot from our perspective now as modern geoscientists that it actually melted.
38:15
SPEAKER_00: So you've got little lenses of melt inside these rocks.
38:19
SPEAKER_00: You know, those are those are little mini granites.
38:23
SPEAKER_00: Those migmatites are little mini granites.
38:25
SPEAKER_00: And so they had this idea where you have okay, you have enough heat in the crust and fluids around you can actually melt rocks to create granite.
38:33
SPEAKER_00: So those fluids are then going to move up through the through the crust and and transform these rocks along and and so basically the idea is you don't have a room problem because you and we can see this in the field, like you have these migmatites, and you can go up through granites and you can see in some granitic rocks, you can actually kind of see leached zones around the granite.
38:54
SPEAKER_00: So the the the rocks that the granites intruded, or what we would call intruded, the rocks around the granites have been leached or parsed or baked by the granite.
39:04
SPEAKER_00: So we would call that contact metamorphism now, but to them that was just the the zone of transformation around the granite, right?
39:13
SPEAKER_00: I mean, so again, like totally reasonable uh field-based observations to uh interpret rocks and to solve a problem, which is the main problem.
39:24
SPEAKER_00: But then you got guys like Norman Bowen, and Norman Bowen, you know, for us he's the father, one of the fathers of our field.
39:31
SPEAKER_00: We're also both alumni of the Carnegie Institution in Washington, which is where Norman Bowen spent most of his career.
39:38
SPEAKER_00: And so, you know, Bowen and guys like uh Frank Shirer and Tuttle did a bunch of experimental petrology.
39:46
SPEAKER_00: So basically they took, because we have chemistry now, they took the chemical components of granites and they put them in crucibles and they heated them up at different temperatures and pressures and water contents, and they looked at the chemistry of those experiments, and they saw that you can actually produce uh granitic compositions from melting of different rock types.
40:10
SPEAKER_00: So, this is this this idea of uh magmatism is really centered around the observation that you know you can.
40:17
SPEAKER_00: I mean, the first observations they made were that you could take quartz and feldspars and melt them to produce granites, but you can actually go further than that and you can take a basalt and incrementally crystallize that to produce granites as well.
40:29
SPEAKER_00: So there's this holistic framework that kind of quote unquote proved that plutonic rocks or granites could be formed from magmas.
40:37
SPEAKER_00: So this is the using chemistry.
40:40
SPEAKER_01: I think this is a a very classic kind of setup, the framework of a field geologist, someone who's out in the field all the time, like H.
40:47
SPEAKER_01: H.
40:47
SPEAKER_01: Dreed, who is making observations on the field.
40:51
SPEAKER_01: And then you have the chemists or the experimentalists in this case who are like cooking things up in their lab and then comparing them chemically to natural examples.
40:59
SPEAKER_01: So, you know, one of the the Tuttle and Bowen things, right, is to say granite, true granite, like the granite in the very strict definition of the word, granite, like we see on on the planet, there's a bunch of granites, look at those compositions, those compare very well with the experiments that they were doing chemically that said, okay, this is what a minimum granite looks like in chemistry.
41:18
SPEAKER_01: So therefore, our experiments have some bearing on reality.
41:22
SPEAKER_01: And so the process that's on that's happening in our experiments, whether it's partial melting or fractional crystallization, is related to what's happening in nature.
41:30
SPEAKER_01: And then you have the field geologist going on and say, wait, wait, wait, the room problem.
41:34
SPEAKER_01: You haven't solved the room problem.
41:35
SPEAKER_01: Like this is a classic setup of like field people making observations and very descriptive things, and then the experimentalists or the geochemists or the people sort of more lab-based, kind of trying to replicate processes in the lab.
41:47
SPEAKER_01: And then this conflict between the two or this tension between the two is very common and exists today in our field of granite petrology, today, big time.
41:56
SPEAKER_00: Oh, yeah.
41:57
SPEAKER_00: I mean, I mean, myself and colleagues will always give people like you, isotope geochemists, a bunch of a bunch of guff for just like taking a beautiful rock and grinding it up and dissolving the whole thing, you know?
42:08
SPEAKER_01: Yeah, exactly.
42:09
SPEAKER_01: I mean, so it's it's just uh, you know, it's such a classic setup that people with different cut back to your point about people with different perspectives are coming at, you know, are are making different conclusions, is because if your perspective's in the field the whole time, you're like, I don't ever see a bunch of room to put a granite somewhere.
42:26
SPEAKER_01: Where is this magma going that you're proposing?
42:29
SPEAKER_01: If that's your field, your your point of view, it's a totally valid one and it makes a lot of sense.
42:33
SPEAKER_01: Uh, especially if you see move fluids moving through the crust and moving elements around.
42:37
SPEAKER_01: If you're an experimentalist and you got this new tool called experimental petrology and you're melting rocks and saying, look, these compare really well to nature.
42:44
SPEAKER_01: I don't know where the room problem gets solved, but like it's happening, you know, that's your perspective.
42:49
SPEAKER_01: And so it's a totally natural tension to have so 100 100%.
42:54
SPEAKER_00: Your quote is your quote from a bowen a bowen to read, or or is there uh what's no, no, it's not bowing to read, but um, but one more thing while I'm while I'm grabbing the quote.
43:04
SPEAKER_00: Okay, two or listen to the quote.
43:06
SPEAKER_00: Well, no, this I this quote can go anytime.
43:08
SPEAKER_00: It's it's it's kind of a it's kind of a long quote.
43:10
SPEAKER_00: It's actually a letter he wrote to a guy, but to kind of bring this magmatist thing around full circle, you know, what we what you and I have been ignoring, which frankly I do too much of, is ignoring, which is volcanic rocks.
43:22
SPEAKER_00: Most people ignore granite so focus on volcanic rocks, I think, but there's no argument that you know volcanic rocks were magmas that erupted.
43:33
SPEAKER_00: The the transformationists aren't out there saying, well, volcanic rocks are just like water that like oozed out at the surface.
43:41
SPEAKER_00: They understand that these were hot magmatic rocks.
43:45
SPEAKER_01: And so one of the other kind of listeners, and also let me let me touch on that too a minute, Mike, is that they also understand that in certain eruptions a ton of magma comes out, so there is a lot of magma stored in the crust somewhere.
43:58
SPEAKER_01: This is understood.
44:00
SPEAKER_01: This is not a hard uh conclusion to make, but it's more like what is the dominant mechanism, right?
44:05
SPEAKER_01: It's it's is the dominant mechanism magmatism or transformism or or um granitization.
44:11
SPEAKER_00: Exactly.
44:12
SPEAKER_00: And so one of the, to my mind, one of the death knells of the transformationist or granitizer side is the fact that Bowen and Tuttle and Shirer's experiments show that granites can be made through these processes and that their compositions match exactly on the rhyolites that are erupted.
44:35
SPEAKER_00: So erupted rhyolytic magmas, these high silica and volcanic eruptions have the identical composition to the great rock.
44:43
SPEAKER_00: So there is a magmatic chemical link between the two.
44:48
SPEAKER_00: And so that was kind of one of the uh death knells of the transformationist debate.
44:53
SPEAKER_00: And and and frankly, like the transformationists, the models are a little confusing and occluded.
44:59
SPEAKER_01: So it's much simpler to look at Bowen's reaction series and say, oh, that makes sense how we end up with quartz, two felt spars, and some muscovite, because you know it's and it can uh experimentally be derived there.
45:11
SPEAKER_01: So okay, so that leads us pretty much to to sort of modern-ish times and plate tectonic the origin of plate tectonic.
45:19
SPEAKER_01: Well, yeah, please, sorry, quote, of course.
45:21
SPEAKER_01: Okay, I forget the quote.
45:22
SPEAKER_00: So, you know, there there's all these fun back and forths between these these guys, and it's it's really fun to read like their correspondence because one of them will give some presidential address somewhere, and then the other one will go presidential address, and they just kind of are like talking smack at each other.
45:39
SPEAKER_00: So there's this other guy, um uh Professor Galuli, who's another famous petrologist, geochemist, a field guy from from back then.
45:48
SPEAKER_00: Uh and he was, you know, I've read a little bit about him, and multiple people uh from different sources have said the same thing is that he would sit in when you're giving a talk at a conference, he would sit like close to the front and he would loudly say, Oh, that's uh horse shit.
46:06
SPEAKER_00: So he would like uh he would say that like in in these conferences, like sitting like front row and being like, Oh, that's horse and and so Bowen was good friends with these guys, you know, like good like uh scientific rivals.
46:20
SPEAKER_00: So Bowen uh wrote this letter to him in 1948.
46:23
SPEAKER_00: He goes, Dear Professor Galouli, uh having had occasion some years ago to learn the art of lip reading, I noticed yesterday when I was giving my paper that at the end of each of my sentences you said horse S word.
46:37
SPEAKER_00: Evidently you had made note of the word equilibria in the title of my paper and were from time to time reminding yourself and your neighbors of the gist of the discussion.
46:47
SPEAKER_00: You are, however, under the misapprehension as to the derivation of the word equilibrium.
46:53
SPEAKER_00: It does not come from equus equaling a horse to Libria, things liberated or discharged.
47:01
SPEAKER_00: But it is from quite different roots.
47:03
SPEAKER_00: And then he goes on to just kind of give a little crap.
47:05
SPEAKER_01: But you know, it's like all good natured.
47:08
SPEAKER_01: I mean, I I I must say that's that's pretty impressive.
47:11
SPEAKER_01: If I was giving a talk and somebody sat up in the front row and just yelled at every sentence or mouthed it to my neighbors, I would not have I don't think I'd have like the confidence or I don't know, the good naturedness to be able to write a letter that sort of does this in jest clearly.
47:25
SPEAKER_01: That you know, that I think it harkens back to a a more a less sensitive time or something.
47:30
SPEAKER_01: I'm not really sure.
47:31
SPEAKER_01: Or maybe more personal.
47:32
SPEAKER_01: They're all like friends and they just debated science and discussed it and then went went back and had a beer together or something like that.
47:40
SPEAKER_00: Yeah, there's a much smaller community of people back then too.
47:43
SPEAKER_00: And you know, you can't just, I mean, you you can only have so many enemies, right?
47:48
SPEAKER_00: You know, now are you or I could really dislike someone and I'll never interact with them because I can go to a conference with you know thousands of people.
47:55
SPEAKER_01: Yeah, yeah, yeah.
47:56
SPEAKER_01: That's right.
47:58
SPEAKER_00: Not the same back then.
47:59
SPEAKER_01: So, okay, so so we we end up here and then you know we we we are basically ending this discussion.
48:07
SPEAKER_01: Um is it time to wrap up or do you have another another kind of point here, Mike?
48:11
SPEAKER_00: No, I'm I'm good.
48:12
SPEAKER_00: I'm good.
48:12
SPEAKER_00: So I mean we could go on and on about this, but yeah, that's so that basically the experiments kind of ended the debate.
48:19
SPEAKER_01: Ended the debate, yeah, that's right.
48:20
SPEAKER_01: And but it does not end the debate about the room problem.
48:23
SPEAKER_01: Like there is a room problem, right?
48:25
SPEAKER_01: We don't act, and seismically, we don't see big magma chambers like we draw in the intro-level textbook uh, you know, in the earth.
48:31
SPEAKER_01: We don't see those.
48:32
SPEAKER_01: We see disaggregated melt pockets, right?
48:35
SPEAKER_01: So the the the big vat volume of magma of pure liquid probably uh isn't a thing, and that actual granites we know now, as we'll talk about maybe in the next episode or one of the coming episodes in this theme, we'll talk about the the timing of these things and how actually we look at a big granite body, and it's not all one big event.
48:54
SPEAKER_01: This occurs over millions of years.
48:56
SPEAKER_01: It's kind of an incremental emplacement type thing.
48:58
SPEAKER_01: But I want to come back to the well, kind of uh I want to I want to come back to the granitizer thing a minute because in one of these papers, your original, well, one of your one of your high profile papers that you've written, your nature paper in 2019, got cited in this review.
49:17
SPEAKER_01: And it got cited in an interesting way.
49:20
SPEAKER_01: The the Earth Science Reviews paper.
49:22
SPEAKER_01: Oh, you didn't read that, you didn't catch up to catch this part?
49:25
SPEAKER_00: No, I don't I don't generally go I don't generally go and say, or did they cite my papers and no, well, no, but uh it's it's still up to me because it's in a section.
49:34
SPEAKER_01: I'll just read this to the observational and analytical approaches, etc.
49:38
SPEAKER_01: etc.
49:39
SPEAKER_01: So it's in this kind of section where sort of modern, we're talking about modern rocks now and talking about modern processes.
49:44
SPEAKER_01: Um, a noteworthy finding from titanium and quartz thermobarometry is a significantly low formation temperature obtained by Ackererson et al.
49:52
SPEAKER_01: 2018 for the Tuamini Intrusive Suite.
49:54
SPEAKER_01: Although low temperature magma storage has already been inferred, the results from Ackererson may result in one of the paradigm shifts of the 21st century regarding the knowledge of granitic rocks with major implications for their petrogenesis.
50:07
SPEAKER_01: So that's high praise.
50:09
SPEAKER_01: Um, and I it brings to mind because it sounds like something my mom would have written.
50:14
SPEAKER_01: Well, what what yeah, yeah, that's right.
50:16
SPEAKER_01: Yeah.
50:17
SPEAKER_01: Well, I I mean, there's a lot of people who disagree with that, that statement, first of all.
50:22
SPEAKER_01: Um including maybe parts of uh maybe you, I don't know exactly.
50:27
SPEAKER_01: But what you and I end up talking about.
50:28
SPEAKER_01: I yes, I disagree with that statement.
50:30
SPEAKER_01: Okay.
50:30
SPEAKER_01: Well, what you and I um talk about scientifically, that's exciting, is this kind of fluids, low temperature granites, fluids in the crust, like elements moving via fluids or via something that's not the intro level version of magma.
50:47
SPEAKER_01: It's not like I melt rock.
50:48
SPEAKER_01: It's not even the Norman Bowen version of magma necessarily.
50:51
SPEAKER_01: It's not like I melt this rock completely, and then I get granite eventually out of that.
50:55
SPEAKER_01: It's more like, hey, fluids are really involved here.
50:58
SPEAKER_01: Fluids meaning like water-based liquids, and they can move a lot of material.
51:03
SPEAKER_01: You know, we were just talking about this the other day about some of my colleagues working here at Penn State, and they're moving a lot of material, they're doing stuff in the Earth's system.
51:10
SPEAKER_01: So is there any it's not granitization at all, but it is there like a middle ground between granitization and magmatism that can be accommodated or that can be is like part of the current debate in granite patrology?
51:27
SPEAKER_01: Would you reframe it as a as like a rekindling of the granitizer ideas in the modern world, or is that too far?
51:35
SPEAKER_01: That's a bridge too far to say it that way.
51:37
SPEAKER_00: I will say that that I think that might be a bit of a bridge too far.
51:42
SPEAKER_00: Um yeah, so one of the famous petrologists of the later 20th century is a guy, Ian Carmichael, and he is like the academic father of a lot of who I would consider are modern like giants of petrology, like the P Line and Mark Girlso and others.
52:02
SPEAKER_00: And he would take his students out every time I talk to somebody about this, you know, they'll say, Oh, well, Ian always said that granites are metamorphic rocks.
52:12
SPEAKER_00: And that observation is partially based on the fact that textually they're very different from volcanic rock, that they, you know, that they must have had some sort of history that is not purely magmatic in the sense that we think about, right?
52:26
SPEAKER_00: And so I think in that sense, like the debate is it's not are granites created from fluids, but how are magmas modified from something that could erupt as a volcano to something that ends up as a granite?
52:43
SPEAKER_00: So I think those are two different things.
52:45
SPEAKER_00: Like granitizers said you could take a sandstone and turn it into a granite.
52:49
SPEAKER_00: Whereas I think what we're these conversations we're having now are more nuanced about when you have a magma that goes into the upper crust, it will potentially have a lot of water around it and it'll be injected at higher temperatures and pressures.
53:03
SPEAKER_00: So how do you go from something that can erupt to something that we see as a granite?
53:09
SPEAKER_00: And that is where I think the interesting conversation is.
53:12
SPEAKER_00: But it's not um that's not the granitizers debate.
53:15
SPEAKER_00: Although I have had people um come up to me and be like, Oh, I'm so excited you're revitalizing the granitizers versus magmatist debate.
53:22
SPEAKER_00: I'm like, I am not doing that.
53:23
SPEAKER_00: I'm not doing that.
53:24
SPEAKER_00: Don't don't don't lump me into that.
53:26
SPEAKER_01: Yeah, no, I totally get that.
53:28
SPEAKER_01: There's some really interesting ideas that that that are sort of um well, I okay, let me let me put it this way.
53:35
SPEAKER_01: Where does the future lie?
53:36
SPEAKER_01: Where's the most exciting stuff for the students out there who are like interested in this kind of thing?
53:41
SPEAKER_01: What what are the interesting debates or interesting discussions in this in the current Kranite literature?
53:47
SPEAKER_01: I mean, because to me, the interaction, this kind of medium temperature space with a lot of fluid around, whether it's low temperature granites or high temperature metamorphism, things that they're the 400 degrees to 600 degrees, relatively high grade metamorphism, that's a really exciting space for all sorts of applied reasons, meaning, you know, high temperature enhanced geothermal systems, or you know, what how how do we get critical metal extraction?
54:15
SPEAKER_01: This is where ore deposits are formed.
54:17
SPEAKER_01: Like this is a really exciting scientific space at the moment.
54:20
SPEAKER_01: Did you agree with that?
54:21
SPEAKER_01: And and what what else would you add to that?
54:23
SPEAKER_00: Yeah, no, I I agree.
54:24
SPEAKER_00: And I think, you know, one of the interesting things I think we probably have a similar scientific philosophy in that uh new techniques enable new observations, which enable new science.
54:37
SPEAKER_00: And uh currently, to me, it feels like we have uh really incredible analytical capabilities, but the uh tools we can use uh with those analytical capabilities aren't caught up to that.
54:51
SPEAKER_00: So for example, you know what I mean is like, you know, we can measure titanium and coarse crystals on uh ICPMS or a microprobe, but we really are under we don't really have a consensus on you know how that titanium concentration of that coarse crystal relates to temperature and how fast titanium diffuses through that crystal.
55:13
SPEAKER_00: We'll get into that stuff later.
55:15
SPEAKER_00: But you know, I think for me, like one of the interesting things is we've got a ton of analytical capabilities, but the calibrations and tools we use to apply those analytical capabilities to the natural world are under-resourced.
55:30
SPEAKER_00: Right, right.
55:30
SPEAKER_00: I see.
55:31
SPEAKER_01: We have some catching up to deal with between our analytical capabilities in the real world, we got to make that link more, meaning more experiments to to calibrate these things, more ideas, more empirical tests, go out in the real world and and you know, make the measurements in a known and known location where you kind of think you should get the right answer um or know what the right answer is, for instance.
55:51
SPEAKER_01: So that yeah, okay, that's good.
55:52
SPEAKER_01: I like that.
55:52
SPEAKER_01: That's a good framing.
55:53
SPEAKER_01: And you're not a granitizer, um, that's good to know.
55:56
SPEAKER_01: But you're but but there are variations on the magmatist approach, and we'll we'll dive into some of those things in the coming discussions, as well as some you know, deeper petrology type stuff that is important to know um and I think is is becoming more relevant for sure.
56:12
SPEAKER_01: In you know, people students now should know phase diagrams, knowing phase diagrams will benefit you in your career if you go into a field, because there's a lot of fields that are going to be using this type of information, and there's a there's a big runway for this type of stuff, I think, in the future.
56:27
SPEAKER_01: It's a good time to be a petrologist, I think.
56:29
SPEAKER_01: Not only a good time to be a geologist, but a good time to be a petrologist thinking about these things and doing uh doing some work on it.
56:35
SPEAKER_00: So yeah, I agree.
56:36
SPEAKER_00: I agree.
56:37
SPEAKER_00: And we still haven't resolved the room problem.
56:39
SPEAKER_01: Um, you mean you and I haven't resumed the room problem?
56:42
SPEAKER_00: We haven't we haven't talked about it here.
56:44
SPEAKER_01: Okay, so what's the what's the resolution to the room problem?
56:46
SPEAKER_01: Or should we save that for another episode?
56:48
SPEAKER_00: I was gonna say maybe we'll save that.
56:50
SPEAKER_00: We'll we'll we'll save the a teaser for the episode about how granites are in place in the crust and the time scales of granite formation.
56:58
SPEAKER_00: That sounds good.
56:59
SPEAKER_01: Because we get to you talk about geochronology in there, which is my favorite.
57:02
SPEAKER_01: So yeah, and and this was this was one of the yeah, I don't know if you had this, uh you you scientifically matured a lot sooner than I did in my career.
57:09
SPEAKER_01: But in my Oh, give me a break.
57:11
SPEAKER_01: Come on.
57:12
SPEAKER_01: Well, in my PhD, I had these the you know, this this time frame, how long do granites take to form.
57:19
SPEAKER_01: I heard a talk from Ursch Schaltiger came and gave a talk at this, and it just blew my mind the idea that a granite is not like a point in time.
57:27
SPEAKER_01: You can't just put a pin in the time that the gr that this whole body I'd always thought of igneous rocks as like a single point in time, and the fact that they're not was a mind-blowing thing to me in graduate school.
57:39
SPEAKER_01: So we'll we'll give listeners um the the history of that field, which is a much shorter history because it's geochronology, but the 20-year history of that field in a coming episode, I'd say.
57:49
SPEAKER_01: Let's do that.
57:50
SPEAKER_00: Yeah, yeah.
57:51
SPEAKER_00: I think we'll we'll keep the room problem for that conversation.
57:53
SPEAKER_00: Perfect.
57:54
SPEAKER_00: But I'm I'm gonna come back and I'm not gonna let you say I'm mature and fascinating.
57:58
SPEAKER_00: That's a bunch of bullhogs.
57:59
SPEAKER_00: Like you were you knew what you wanted to work on way soon.
58:01
SPEAKER_00: No, no, no, no, no, no, no.
58:03
SPEAKER_00: You know, you're you're saying, like, you know, we see a talk from URS, you know, about like the timescales of granites, but the error bars on the measurements that you're making on four billion-year-old rocks are bigger than the entire placement of the Sierra Nevada Batholith.
58:18
SPEAKER_01: So like it's true.
58:20
SPEAKER_01: It's true, yeah.
58:21
SPEAKER_01: Yeah.
58:21
SPEAKER_00: You didn't have to think about processes happening on a hundred thousand.
58:25
SPEAKER_01: That's a good that's a fair point.
58:26
SPEAKER_01: Definitely was not forced to.
58:27
SPEAKER_01: Definitely not.
58:28
SPEAKER_01: No, for sure.
58:29
SPEAKER_01: All right, man.
58:30
SPEAKER_01: Hey, that's uh that's wraps this episode.
58:32
SPEAKER_01: We are gonna have more on Granit's uh coming up with me and Mike.
58:35
SPEAKER_01: I'm I'm uh I'm excited to talk to you about it and continue this conversation.
58:38
SPEAKER_01: You can follow us on social media at Plant GeoCats, download the Camp Geo Mobile app, first link in your show notes.
58:43
SPEAKER_01: There we have all the intro content Chris and I made.
58:45
SPEAKER_01: So the first class you take in an intro level uh geology degree, the physical geology class is mostly there, including a whole bunch of Indian instructs.
58:53
SPEAKER_01: You can go see what Bowen's Reaction Series looks like when you click on that episode, a whole episode on Bowen's Reaction Series.
58:59
SPEAKER_01: So check that out, and uh and then we can continue the deep dives here.
59:02
SPEAKER_01: So appreciate it, man.
59:04
SPEAKER_00: Yeah, of course, just you always fun buddy.