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Remapping Yellowstone National Park · PlanetGeo: The Geology Podcast

• 0:02
  SPEAKER_01: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:13
  SPEAKER_01: Hey, I've got recovered Chris.
• 0:18
  SPEAKER_01: You do.
• 0:19
  SPEAKER_01: You do.
• 0:19
  SPEAKER_01: You were down for the count for a little bit there, man.
• 0:22
  SPEAKER_01: We were we were supposed to record this uh yesterday, but I got a text, and Chris was not feeling so good.
• 0:29
  SPEAKER_01: Oh man, Brilliant.
• 0:30
  SPEAKER_00: It was an absolute wreck.
• 0:32
  SPEAKER_00: I mean, not good at all.
• 0:34
  SPEAKER_00: Yeah, you know, when I get the flu, all my skin hurts, my lower back hurts, and it just goes everywhere.
• 0:42
  SPEAKER_01: I feel you, man.
• 0:43
  SPEAKER_00: It does, it does.
• 0:43
  SPEAKER_01: Well, we're I'm glad we have recovered Chris here and excited Chris because we're talking about Yellowstone.
• 0:48
  SPEAKER_00: We are, but you know what else happens to me?
• 0:50
  SPEAKER_00: I have a recurring nightmare when I get the flu.
• 0:53
  SPEAKER_00: Do you get this?
• 0:54
  SPEAKER_00: Do you have a recurring nightmare?
• 0:55
  SPEAKER_01: No.
• 0:55
  SPEAKER_00: I have a recurring nightmare.
• 0:56
  SPEAKER_00: It's a toothpick, a big, gigantic toothpick that is floating and it's coming at me, and I cannot outrun this toothpick.
• 1:03
  SPEAKER_00: And I'm in my I'm in my childhood home.
• 1:07
  SPEAKER_01: Every time you get the flu, you have this.
• 1:09
  SPEAKER_01: Somebody out there has to know what the sort of Freudian implications of a giant toothpick are.
• 1:14
  SPEAKER_01: So hit us up.
• 1:15
  SPEAKER_01: Let us know.
• 1:15
  SPEAKER_01: Send us an email with the interpretations of Chris's dream.
• 1:19
  SPEAKER_01: That's very funny.
• 1:21
  SPEAKER_01: Wow, that's amazing.
• 1:22
  SPEAKER_01: All right, well, what a transition here.
• 1:23
  SPEAKER_01: How do how do I think of I'm trying to win the Segway Award by transitioning that to Yellowstone?
• 1:28
  SPEAKER_01: There's no connection.
• 1:29
  SPEAKER_01: There's no connection to get us there.
• 1:31
  SPEAKER_01: No, there's not.
• 1:32
  SPEAKER_01: We just got to hit them up.
• 1:33
  SPEAKER_01: What are we doing?
• 1:34
  SPEAKER_01: Let's do it.
• 1:34
  SPEAKER_01: So, Chris, yeah, what what are we talking about today?
• 1:37
  SPEAKER_01: And and I think importantly, why are we talking about this?
• 1:40
  SPEAKER_01: Because, well, it's Yellowstone, so that interests us for many reasons.
• 1:43
  SPEAKER_01: But what is it and why are we talking about it?
• 1:44
  SPEAKER_00: Absolutely.
• 1:45
  SPEAKER_00: So we're talking about something that's been hitting the news lately about Yellowstone National Park and this remapping project by one of the people that we interviewed, Dr.
• 1:54
  SPEAKER_00: Michael Poland, the scientist in charge at the Yellowstone Volcano Observatory.
• 1:58
  SPEAKER_00: He's headed up this kind of new project that is really changing the way the geologic map of Yellowstone National Park looks like.
• 2:06
  SPEAKER_00: It's awesome.
• 2:07
  SPEAKER_01: Yeah, so that caught our eye for many reasons, which we'll talk about.
• 2:10
  SPEAKER_01: One, it's Yellowstone.
• 2:10
  SPEAKER_01: Two, it's somebody we've interviewed in the past.
• 2:12
  SPEAKER_01: Three, it's geological mapping and it's sort of new interpretations and new interpretations of this very significant super volcano event.
• 2:20
  SPEAKER_01: And well, it's interesting for many reasons, which we'll get into, Chris.
• 2:23
  SPEAKER_01: But let me just say out front, too, that we also this is also timely because we've also just launched our Yellowstone visual audiobook course that's available, first link in the show notes, right next to the Camp Geo content.
• 2:35
  SPEAKER_01: So you can go there if you're going to Yellowstone, if you're not going to Yellowstone, go there.
• 2:39
  SPEAKER_01: There's, I don't know, 10, 11 hours of us talking about various features of Yellowstone, some really cool images and gifts integrated in the audio the same way that it is with Camp Geo.
• 2:48
  SPEAKER_01: So it's a timely sort of news article about Yellowstone geology.
• 2:52
  SPEAKER_01: And so go there if you want to learn more and get some deeper information about Yellowstone National Park.
• 2:57
  SPEAKER_00: So shall we go ahead and jump right into some things we want to talk about with this?
• 3:01
  SPEAKER_00: Yeah, Chris.
• 3:02
  SPEAKER_01: I think um I think we need to set the stage here.
• 3:04
  SPEAKER_01: So maybe just give us a review, really short intro review of the Yellowstone geology, the eruptions that we're talking about.
• 3:11
  SPEAKER_00: Okay, so we're only going to focus on Yellowstone proper, what is now Yellowstone National Park, and there are three major caldera forming eruptions.
• 3:19
  SPEAKER_00: We'll talk about a caldera again as a review and how they form and what they are.
• 3:23
  SPEAKER_01: Yeah, and we have a really great caldera gif when we're talking about the Yellowstone plume in our Yellowstone audiovisual book.
• 3:30
  SPEAKER_01: So go go there, you can see that uh that really nice gif that explains this.
• 3:33
  SPEAKER_01: We have a whole episode on calderas and how they form.
• 3:36
  SPEAKER_01: So anyway, short and short and quick.
• 3:37
  SPEAKER_01: Sorry, Chris, for interrupting.
• 3:38
  SPEAKER_00: No, you're all good.
• 3:39
  SPEAKER_00: So 2.1 million years ago, uh, there was this super eruption that happened.
• 3:44
  SPEAKER_00: This was the it's called the Huckleberry Ridge Formation, and this was like 2,500 times larger in terms of volume of ejected material than Mount St.
• 3:55
  SPEAKER_00: Helens in 1980.
• 3:56
  SPEAKER_00: Then we have the 1.3 million year ago eruption.
• 4:00
  SPEAKER_00: That's the Mesa Falls eruption, and that one actually did not qualify as a super eruption because it has to be about 1,000 cubic kilometers in order to qualify as a super eruption.
• 4:12
  SPEAKER_00: And this one was, I'm gonna do this quote unquote, only 240 cubic kilometers.
• 4:17
  SPEAKER_00: So it was still massive compared to Mount St.
• 4:20
  SPEAKER_00: Helens.
• 4:21
  SPEAKER_00: And then 631,000 years ago, you have the Lava Creek member.
• 4:25
  SPEAKER_00: And this was a super eruption.
• 4:27
  SPEAKER_00: It was, you know, smaller for a super eruption scale because it barely met the criteria, about 1,000 cubic kilometers ejected during this phase of eruptions.
• 4:37
  SPEAKER_01: So, Chris, I think that's a good time to talk about the timing of this, and this is something I'll let you talk about.
• 4:42
  SPEAKER_01: This so answer the question is Yellowstone overdue for an eruption?
• 4:46
  SPEAKER_00: You know this is one of the most irritating things out there, right?
• 4:49
  SPEAKER_01: Yeah, I could see the I wanted to see the vein.
• 4:51
  SPEAKER_01: I don't I wanted to see the vein bulge while I'm asking this question a little bit.
• 4:54
  SPEAKER_00: I don't know.
• 4:55
  SPEAKER_00: I don't quite understand the math.
• 4:57
  SPEAKER_00: You know, people say that Yellowstone's overdue for an eruption.
• 5:01
  SPEAKER_00: Where does this come from?
• 5:02
  SPEAKER_00: You know, you look look at the the interval between the first and the second eruptions, 2.1 and 1.3 million years, that's 800,000 years between eruptions.
• 5:12
  SPEAKER_00: You look at the interval between the second and the third eruptions, and you have 1.3 million years ago to 631,000 years ago, that's 700,000 years.
• 5:22
  SPEAKER_00: Where does this come from that it's overdue for an eruption?
• 5:26
  SPEAKER_00: The math just doesn't, first of all, this isn't the way volcanoes operate anyway.
• 5:31
  SPEAKER_00: But second of all, the math doesn't even make sense.
• 5:34
  SPEAKER_00: I don't quite understand uh where where maybe just people like to create drama.
• 5:39
  SPEAKER_01: I I think so.
• 5:39
  SPEAKER_01: You know, it's a it's a good clickable article uh title.
• 5:42
  SPEAKER_01: That's true.
• 5:43
  SPEAKER_01: So I think this is an important sort of lead-in to the next point, which is that these are not these eruptions are not singular events, these occur in pulses.
• 5:51
  SPEAKER_01: And we've known this for a while, that uh these eruptions, you know, we talk about them being, you know, a thousand cubic kilometers, which is the definition of a super eruption.
• 6:00
  SPEAKER_01: But what actually is occurring is these are more pulsed volcanic eruptions, so they're occurring frequently, kind of near each other, on the order of tens of thousands of years, you know, sort of so basically really quick in geologic time, but they're not singular events if we were standing there watching them, right?
• 6:15
  SPEAKER_00: So which is interesting.
• 6:17
  SPEAKER_00: Let me interrupt you, Jesse.
• 6:19
  SPEAKER_00: This is interesting because we had two kind of takes on why this publication caught traction in the popular news.
• 6:26
  SPEAKER_00: And we came at it from different angles, actually.
• 6:28
  SPEAKER_00: I think.
• 6:29
  SPEAKER_01: So let me let me just say, Chris, let me uh maybe just before we touch on that, let me just say what the conclusion was.
• 6:34
  SPEAKER_01: Basically, what happened is we went, you know, they there was this project, a bunch of geologists who went and remapped some of these things.
• 6:41
  SPEAKER_01: So boots on the ground, walking around, looking at the rocks, creating a geological map.
• 6:45
  SPEAKER_01: And they went and looked at this area, the Sour Creek Dome in Yellowstone National Park, and they remapped the layers, the the rhyolites, the tufts, all these volcanic rock layers.
• 6:55
  SPEAKER_01: And what they discovered is that some of the layers that were mapped as lava creek tough and importantly, Huckleberry Ridge, so the older ones are actually part of the younger ones.
• 7:04
  SPEAKER_01: So they took, you know, some of the rocks that were mapped as Huckleberry Ridge, the oldest super eruption in Yellowstone, and they remapped them and said, no, actually these are lava creek tough.
• 7:14
  SPEAKER_01: So these are the youngest ones.
• 7:15
  SPEAKER_01: And so they're kind of shifting about the timeline, the geologic timeline on the map.
• 7:20
  SPEAKER_01: So that's the the conclusion here.
• 7:22
  SPEAKER_01: And so sorry for interrupting.
• 7:24
  SPEAKER_01: We were talking about you know why how we both thought about this differently.
• 7:27
  SPEAKER_00: Right.
• 7:28
  SPEAKER_00: Well, the question is like, or why did this headline grab popular news traction?
• 7:33
  SPEAKER_00: And we kind of had two different takes on it.
• 7:35
  SPEAKER_00: Your take was what you just described is that, well, the geologic map looks really different.
• 7:40
  SPEAKER_00: And it does, because this this really changed the way the geologic map looks.
• 7:46
  SPEAKER_00: My take on it was that a lot of people think that volcanic eruptions are singular events.
• 7:54
  SPEAKER_00: And uh, you know, the realization that Yellowstone probably each of these eruptions, each of these quote unquote three super or two super eruptions and one other massive but not a super eruption, these were phases that probably lasted decades.
• 8:10
  SPEAKER_01: Yeah, right.
• 8:11
  SPEAKER_00: You know, and that's I think that was my takeaways that I I don't think a lot of people realize that.
• 8:17
  SPEAKER_00: And I could be wrong, I don't know, but I think the mass public thinks that eruptions are more singular things, and that's maybe what grabbed traction with this.
• 8:27
  SPEAKER_00: Yeah.
• 8:27
  SPEAKER_00: Because that's kind of what the headlines speak to.
• 8:29
  SPEAKER_01: Yeah, and I think that's right, Chris.
• 8:31
  SPEAKER_01: I think that you know, both both of these are kind of right.
• 8:33
  SPEAKER_01: And I think what was part of the confusion is because of the way we speak about calderas.
• 8:37
  SPEAKER_01: And so maybe we should have a quick interjection and describe what a caldera actually is.
• 8:42
  SPEAKER_00: And so Okay, you do get the Segway award for that one.
• 8:45
  SPEAKER_00: Nice one, huh?
• 8:46
  SPEAKER_00: Nice one.
• 8:46
  SPEAKER_00: Really nice.
• 8:47
  SPEAKER_00: That's good.
• 8:47
  SPEAKER_01: Yeah, there we go.
• 8:48
  SPEAKER_01: I like that.
• 8:49
  SPEAKER_01: So so these are these three eruptions that you talked about 2.1 million years ago, 1.3 million years ago, and 631,000 years ago, these have three different calderas.
• 8:57
  SPEAKER_01: And so if you look at a geological map, you can see there are three different caldera outlines.
• 9:02
  SPEAKER_01: And what a caldera is, is it's different from a crater.
• 9:05
  SPEAKER_01: We think of a crater as, you know, something that a volcanic eruption blows the top off of volcanoes.
• 9:10
  SPEAKER_01: So Mount St.
• 9:11
  SPEAKER_01: Helens, the top of the volcano is now gone.
• 9:14
  SPEAKER_01: The top of the mountain has been blown to ash.
• 9:16
  SPEAKER_01: A caldera is different, it's larger and it's formed by the emptying out of a magma chamber in the crust, and the crust collapsing down in on itself.
• 9:25
  SPEAKER_01: So it's much more about land subsidence more than explosion blowing stuff into obliteration up in the atmosphere, right?
• 9:32
  SPEAKER_01: And so the caldera can be huge.
• 9:34
  SPEAKER_01: And Chris, this is something we we really talk about a lot again in our our Yellowstone book, is that not all of Yellowstone National Park is inside the park boundaries, are inside of the most recent caldera, right?
• 9:47
  SPEAKER_01: So that leads to some really interesting geological phenomenon that some features are inside the caldera, some are outside the feature.
• 9:52
  SPEAKER_01: They have very different geological regimes, both inside and outside the caldera.
• 9:56
  SPEAKER_01: But to bring this back to the reason that people might think, like at least for me, the reason that I could see why people say, oh, that one volcanic eruption is one event, is because we assign it to one caldera, right?
• 10:10
  SPEAKER_01: So we it's like one caldera, one eruption.
• 10:12
  SPEAKER_01: We kind of think, oh, those go together.
• 10:14
  SPEAKER_01: But it's not actually the case.
• 10:15
  SPEAKER_01: One caldera could equal multiple pulses of volcanism.
• 10:18
  SPEAKER_00: That's a really good point.
• 10:19
  SPEAKER_00: Uh, you know, and and it is very difficult to see when you go to Yellowstone, you kind of have to know because the caldera is so big.
• 10:27
  SPEAKER_00: Look, when I'm standing on the rim of Mount St.
• 10:29
  SPEAKER_00: Helens and I look across the other rim and I look at this, the north facing side that's been blown away and emptied out, that you can't you can't mistake that.
• 10:40
  SPEAKER_00: You know, it stands up and smacks you in the face and says, Hey, I'm a crater.
• 10:43
  SPEAKER_00: I I blew myself apart here.
• 10:45
  SPEAKER_00: Yellowstone is not that way.
• 10:46
  SPEAKER_00: It's just it, you know, it had both.
• 10:48
  SPEAKER_00: It was cataclysmic, it was violent, but then it the caldera really formed by collapse after this happened.
• 10:54
  SPEAKER_00: And you kind of have to know where you're going.
• 10:57
  SPEAKER_00: You can sit in certain places and literally dangle your legs over the the rim of the caldera in certain places, and that's kind of cool.
• 11:05
  SPEAKER_00: Well, I think it's really cool.
• 11:07
  SPEAKER_01: It's very I mean, it's so cool.
• 11:09
  SPEAKER_01: Don't downplay that.
• 11:10
  SPEAKER_01: It's amazing.
• 11:12
  SPEAKER_00: But then when you sit there and you look across that, you you kind of you just sit there and wonder about man, this is just so big.
• 11:20
  SPEAKER_00: I wonder if I didn't have the knowledge that I have, if I would be able to recognize what I'm doing right now, what I'm looking at right now.
• 11:28
  SPEAKER_00: And it I don't think I think a lot of people struggle with that when they go to Yellowstone.
• 11:32
  SPEAKER_01: I think that also sort of highlights why this type of mapping, to me at least, this type of mapping is difficult.
• 11:38
  SPEAKER_01: Geological mapping is geologists walking around, looking at contacts between exposed rock units.
• 11:44
  SPEAKER_01: So, okay, you're walking across the sandstone, and then you hit a limestone, okay, there's a boundary there.
• 11:48
  SPEAKER_01: You can put a line in the paper on the map that says I went from a sandstone to a limestone.
• 11:53
  SPEAKER_01: You can do the same thing with a volcanic rhyolite versus a volcanic tuff, and volcanic rhyolites of different flavors and different characters and different ages.
• 12:00
  SPEAKER_01: So mapping these out, but this caldera forming event adds to the complexity because not only is the volcano erupting material on top and covering up older stuff, but the land is collapsing back down in on itself and creating these really complicated structural patterns as it collapses back down.
• 12:18
  SPEAKER_00: And so I think I can understand why not only to that, Jesse, then it gets buried by other lava flows that happen after this 631,000-year-old caldera collapse.
• 12:28
  SPEAKER_01: And and Chris, this was like one of the more, I think, sort of um interesting, sort of high-level things that stood out to me about this was that in Yellowstone National Park, one of the most geologically researched places on the planet, probably, there's new discoveries to be made by people walking around, knowledgeable geologists walking around and mapping this stuff.
• 12:50
  SPEAKER_01: Like that, that is a really cool high-level summary.
• 12:53
  SPEAKER_01: That wait, there's this stuff we don't understand.
• 12:55
  SPEAKER_01: And I view geological mapping, it's the oldest form of geology and the most basic form of geology, like you know, geochemistry, geochronology, seismology, these are all relatively new fields compared to people walking around looking at rocks.
• 13:08
  SPEAKER_01: And so even in Yellowstone, people walking around looking at rocks, doing the old school stuff can make valuable contributions.
• 13:14
  SPEAKER_01: That that resonated with me a lot.
• 13:16
  SPEAKER_00: Well, that brings me to a question that I want to ask for you, and it's something that I'm interested in discussing, and I hope the audience is as well is how long did these pulses last?
• 13:26
  SPEAKER_00: They said there were maybe four pulses and there were gaps in between, they think, but then they know that there were some gaps between some of these pulse phases, right?
• 13:36
  SPEAKER_00: So here's my question then.
• 13:38
  SPEAKER_00: What's our degree of accuracy with radiometric dating?
• 13:42
  SPEAKER_00: Can we nail that down using those methods, those lab techniques?
• 13:46
  SPEAKER_01: Before I answer that, I just want to come back to the time frame again and just highlight with the times we're talking about.
• 13:51
  SPEAKER_01: So this mapping, this remapping, they took what was mapped as one unit of Lava Creek, the youngest unit.
• 13:58
  SPEAKER_01: So that's the 631,000.
• 13:59
  SPEAKER_01: So there's a there's an area on the map that has Lava Creek Tough as covering this region, and also right next to it, Huckleberry Ridge Tough.
• 14:06
  SPEAKER_01: So there's the oldest eruptive unit, the 2.1 million Huckleberry Ridge unit, and then right on top of it is a 631,000 Lava Creek unit.
• 14:15
  SPEAKER_01: They remapped that and said, Oh, wait, actually, no, this is four units of Lava Creek.
• 14:20
  SPEAKER_01: What we thought was Huckleberry Ridge, the oldest part, is actually the younger part.
• 14:24
  SPEAKER_01: So there's four different units of Lava Creek, 631,000 year olds.
• 14:29
  SPEAKER_00: Can I interrupt you a second?
• 14:31
  SPEAKER_00: All right.
• 14:31
  SPEAKER_00: If you got boots on the ground, you got your little rock hammer out and you're you're trying to redo this map or you're looking at this from a different perspective.
• 14:39
  SPEAKER_00: Is it difficult to tell the difference in hand specimen?
• 14:43
  SPEAKER_00: Chunk that you just knocked off, the Huckberry Ridge and the Lava Creek, the 2.1 million year old and the 631,000 year old.
• 14:51
  SPEAKER_00: Is that tough to determine?
• 14:52
  SPEAKER_01: I yes.
• 14:54
  SPEAKER_01: I mean, with like hand sample, I would imagine.
• 14:56
  SPEAKER_01: Now I've not looked at this, so this is me just making something up a little bit.
• 15:00
  SPEAKER_01: It would take me, I've done a lot of mapping up in the north.
• 15:03
  SPEAKER_01: I've seen a lot of very old rocks, and it takes a long time to get your eye tuned into the rocks in any particular area.
• 15:11
  SPEAKER_01: You kind of are walking around in this like fog for sometimes weeks before you figure out, oh, wait, now I'm I remember I'm seeing this type of rock.
• 15:18
  SPEAKER_01: I've seen this rock before.
• 15:20
  SPEAKER_01: I've seen this one with this size biotite phenocris in it, and you know, these size plagioclases, and it looks very similar to the one I saw two weeks ago way over the other hill or three miles down the road.
• 15:31
  SPEAKER_01: So it can be really difficult.
• 15:32
  SPEAKER_01: Where I have done a lot of mapping, people mapped at a really big scale.
• 15:37
  SPEAKER_01: So it's like helicopters and you're flying and you're covering huge traverses where you do one 20-mile straight transect, and that's the only one you do for hundreds of miles north or south.
• 15:47
  SPEAKER_01: People haven't seen the rocks before.
• 15:48
  SPEAKER_01: This area, I would imagine, people have seen these rocks before.
• 15:52
  SPEAKER_01: They just hadn't pieced the story together in this different way, this reinterpretation way.
• 15:57
  SPEAKER_00: And so which brings me to this point that you made a long time ago that one of your research professors said, or your supervising professors said back when you were getting your degree, is Jesse, you really can't identify a rock until you get it in the lab.
• 16:12
  SPEAKER_00: Yeah.
• 16:13
  SPEAKER_01: It it is.
• 16:14
  SPEAKER_01: And I think this brings us really nicely back to the geochronology side, which which you sort of asked me about, I don't know, five minutes ago.
• 16:21
  SPEAKER_01: Um, because there's this really interesting feedback between mapping and geochronology.
• 16:25
  SPEAKER_01: And this is exactly the same way my PhD thesis went, is you collect a bunch of rocks, you kind of make a map in your head, and you you write it on a paper and you have a proposed sort of map.
• 16:34
  SPEAKER_01: Then you go back to the lab and you date these units, and then you go back the next year and say, okay, I have new geochronological and geochemical information to bring into the field and say, Oh, I was I was wrong about that field inference I made.
• 16:45
  SPEAKER_01: The geochronology is telling me I was wrong there, and I need to redo that and rethink it.
• 16:49
  SPEAKER_01: And so you kind of iterate back and forth, back and forth, back and forth.
• 16:52
  SPEAKER_00: Okay.
• 16:53
  SPEAKER_00: I just learned something there.
• 16:55
  SPEAKER_00: That is a really interesting perspective.
• 16:57
  SPEAKER_00: Obviously, because I have not ever had that experience.
• 17:00
  SPEAKER_00: I haven't had that opportunity to ever, you know, take field samples back, have them analyzed, then go back into the field and look at things through that lens.
• 17:09
  SPEAKER_00: That's a really cool thing.
• 17:10
  SPEAKER_00: You you alluded to it before.
• 17:12
  SPEAKER_00: Sometimes geologic mapping, um, it can be like drinking water out of a fire hose.
• 17:17
  SPEAKER_00: Yeah.
• 17:17
  SPEAKER_00: You know, at least when you first start, you know, and that's a so I mean, anybody that's ever gone through geologic mapping, say in field camp, finishing up your undergrad degree or in graduate school, they can certainly vouch for what I just said.
• 17:31
  SPEAKER_00: It it can be an overwhelming thing, at least when you first begin.
• 17:35
  SPEAKER_01: Oh, it's totally overwhelming.
• 17:37
  SPEAKER_01: And anytime you go to a new area, I mean, hey, if you drop me down in Yellowstone National Park, uh, I would be overwhelmed for a while.
• 17:44
  SPEAKER_01: If you said, hey, remap this area, I'd be overwhelmed.
• 17:47
  SPEAKER_01: I don't know, it would take me a while to get my eyes tuned into that to that region.
• 17:51
  SPEAKER_01: I think let me so, Chris, I I just want to keep me out of the weeds here, but there's some cool geochronology here.
• 17:56
  SPEAKER_01: Like this is an interesting field, I think, for me, because these are so young relative to a lot of other types of rocks that we analyze in my lab, for instance.
• 18:07
  SPEAKER_01: We don't really touch stuff that's younger than five million years old because our particular type of geochronology is not well suited to this.
• 18:15
  SPEAKER_01: These really young rocks.
• 18:16
  SPEAKER_01: So you're using uranium to lead mostly?
• 18:19
  SPEAKER_01: We're using uranium-lead and we're using kind of high volume analyses.
• 18:23
  SPEAKER_01: So we end up, I mean, it's not high volume.
• 18:25
  SPEAKER_01: We use a laser that is less than the width of your hair follicle, and we you know hit mineral grains, but that's high volume compared to what some people do.
• 18:32
  SPEAKER_01: So counterintuitively, young rocks are actually really hard to date.
• 18:37
  SPEAKER_01: And you and I have talked about this before.
• 18:39
  SPEAKER_01: There's some really, really poor information out there about radiometric dating techniques, and people usually use very uncertain ages applied to young rocks to argue that all of radioactive decay and all of radiogenic dating is false, which is a complete, complete falsehood, right?
• 18:57
  SPEAKER_01: Dating young rocks is really hard to do, and these are young rocks, so I just want to put some numbers here because there's a recent uh paper that hold on, hold on.
• 19:05
  SPEAKER_00: Before can can I interrupt you, Jesse?
• 19:07
  SPEAKER_00: Because uh I wanna we haven't talked much about this before, so this is new for our podcast.
• 19:13
  SPEAKER_00: What method is appropriate then for rocks that fall in this age?
• 19:18
  SPEAKER_01: Yeah.
• 19:19
  SPEAKER_00: What isotopes are used, real quick?
• 19:21
  SPEAKER_01: There's several that you can use.
• 19:23
  SPEAKER_01: We kind of briefly touched on it.
• 19:26
  SPEAKER_01: Actually, in the Yellowstone audiobook, we touch on dating like the uh deposits at Mammoth Hot Springs.
• 19:34
  SPEAKER_01: And one of the techniques you can use is this uranium-thorium-led decay system.
• 19:38
  SPEAKER_01: So it's a disequilibrium technique, and that's pretty good in this time range.
• 19:41
  SPEAKER_01: Sort of a few tens of thousands of years to hundreds of thousands of years to maybe into the million-year range.
• 19:46
  SPEAKER_01: It can be used for those types of things.
• 19:48
  SPEAKER_01: So, like cave deposits, petroglyphs, uh, hieroglyphic deposits in caves, people can date those things using those methods.
• 19:56
  SPEAKER_01: Actually, interestingly, there's a paper recently that Andy Kelvert, who we interviewed in our podcast, was on that dated the Lava Creek super eruption.
• 20:04
  SPEAKER_01: And they used argon-argon.
• 20:06
  SPEAKER_01: So this is based on the potassium-argon decay.
• 20:08
  SPEAKER_01: And what they do is they take big, big feldspar crystals that you find in some of these lava flows.
• 20:13
  SPEAKER_01: And if you go to Yellowstone, look at some of the rocks, you'll find some of these.
• 20:16
  SPEAKER_01: These feldspars have potassium in them, but there's so much potassium, it decays to argon, and there's enough potassium in the mineral that they can get ages.
• 20:25
  SPEAKER_01: And I'll just read a couple of ages here.
• 20:27
  SPEAKER_01: Some of them gave argon-argon ages, or potassium argon really, ages of 631,000 years, plus or minus 4,000 years.
• 20:36
  SPEAKER_01: So they're dating a mineral grain plus or minus 4,000 years.
• 20:40
  SPEAKER_01: That's an incredible like resolution, I think.
• 20:43
  SPEAKER_01: Isn't that amazing?
• 20:44
  SPEAKER_00: And that answer that answers my question that I asked you that I think led to this discussion, then, is are we able to then separate out these pulses if they happened, say, over a time span of several decades?
• 20:56
  SPEAKER_00: The answer is yes.
• 20:57
  SPEAKER_01: Exactly.
• 20:58
  SPEAKER_01: So one other thing here, another method they can do, which they did in the publication I was just referring to, is you can take a zircon grain.
• 21:04
  SPEAKER_01: And so we use in our lab zircon grains.
• 21:06
  SPEAKER_01: These are ones that are great for uranium ledger chronology.
• 21:09
  SPEAKER_01: And with a really sensitive mass spectrometer, you can just ablate or just hit the rim.
• 21:15
  SPEAKER_01: So you can kind of like just look at the rim of the grain and date the rim growth layer and think of minerals growing like a tree ring.
• 21:22
  SPEAKER_01: If you just date the outer ring of the tree, that's like the most recent part, probably the closest to the eruption.
• 21:28
  SPEAKER_01: And there they can get kind of numbers in the same range 626,000 years, plus or minus 6,000 years.
• 21:34
  SPEAKER_01: So that's just like crazy resolution, I think.
• 21:38
  SPEAKER_01: Um Exactly.
• 21:39
  SPEAKER_00: So hold on a minute.
• 21:40
  SPEAKER_00: Does that mean that the inside of the zircon will be older than the rim of the zircon?
• 21:45
  SPEAKER_00: Is that your point?
• 21:46
  SPEAKER_01: I mean, it's a great question, Chris, because that's where I was gonna go with this.
• 21:49
  SPEAKER_01: Is they they actually date the in part in they actually date the interior part of the zircon grains, and these record six hundred and sixty thousand years, plus or minus around about six.
• 21:58
  SPEAKER_01: So one's yielding Older.
• 22:00
  SPEAKER_01: 626, one's yielding 660.
• 22:03
  SPEAKER_01: So, yes, different, like definitely you're seeing the age span, which brings up some of the complexity, I suppose, because you were dating mineral grains, and as we've talked about, minerals don't grow in the world.
• 22:14
  SPEAKER_00: Hold on, Jesse.
• 22:15
  SPEAKER_00: Uh, can you just real quick explain to everybody why the interior part of the zircon crystal or grain will be older than the rim, just real quick as a review.
• 22:26
  SPEAKER_01: Yeah, you know, the inner part is growing first and it's growing in the magma chamber.
• 22:31
  SPEAKER_01: So the idea being like a tree trunk, the inner part's the oldest, the outer part is the youngest, grew most recently.
• 22:36
  SPEAKER_01: It's the same kind of thing.
• 22:37
  SPEAKER_01: And these minerals, especially the big ones that we can pluck out with tweezers or pick up with your fingers, those grew in a magma chamber, which adds some complexity.
• 22:46
  SPEAKER_00: And so then why would we want to know the rim age?
• 22:49
  SPEAKER_00: Well, because the rim age is going to show us the age of the eruption.
• 22:53
  SPEAKER_00: It's going to show us when this thing began to cool much, much faster than it was inside the magma chamber.
• 23:00
  SPEAKER_00: So we're interested in that.
• 23:02
  SPEAKER_01: And that's a great point, Chris.
• 23:03
  SPEAKER_01: It's the rim is going to be the closest to the eruption that we have.
• 23:08
  SPEAKER_01: It's actually really hard to date the eruption itself.
• 23:11
  SPEAKER_01: You know, when did the eruption happen is really hard to date that actual event.
• 23:15
  SPEAKER_01: So we're getting like sort of a maximum age here.
• 23:17
  SPEAKER_01: Like uh the grain grew and then eruption happened, and the eruption happened sometime younger than that last date.
• 23:23
  SPEAKER_00: That's right.
• 23:24
  SPEAKER_00: And and just for everybody out there, that you'll see in the literature for this most recent eruption a range between 631,000 years ago and 640,000 years ago, you see that all over the place.
• 23:37
  SPEAKER_00: And it's a complex reason for why that is the way it is.
• 23:41
  SPEAKER_00: But I think early on, 640,000 was was what we kind of settled on.
• 23:47
  SPEAKER_00: But as time goes on, we've gotten so much better at this that we've rested our best estimate on this is 631,000 years ago for this most recent calderaforman eruption.
• 24:01
  SPEAKER_01: Yeah, exactly.
• 24:02
  SPEAKER_01: I mean, this this sort of volcano stratigraphy, you know, putting together these volcanic eruption events in time order is really uh it's an impressive field.
• 24:11
  SPEAKER_01: I think it's totally cool.
• 24:13
  SPEAKER_01: And and I I think this is partially why this headline stood out to me because this the science backing up this this interpretation is really cool from the field mapping and the integration with the geochronology techniques and the geochemistry techniques, it's just a really cool story.
• 24:26
  SPEAKER_01: Really cool.
• 24:27
  SPEAKER_00: I agree.
• 24:28
  SPEAKER_00: So, all right, so Jesse, I have a question then that just popped into my head.
• 24:32
  SPEAKER_00: Oh boy, here we go.
• 24:34
  SPEAKER_01: Buckle up, everybody.
• 24:35
  SPEAKER_00: Well, no, I don't I don't think so.
• 24:37
  SPEAKER_00: I don't know.
• 24:37
  SPEAKER_00: I don't know.
• 24:38
  SPEAKER_00: We'll see where this goes.
• 24:38
  SPEAKER_00: But you have this radiometric dating facility and you have access to other, you know, instruments and so on.
• 24:45
  SPEAKER_00: Where does Mike Poland, the scientist in charge at YVO, where does he send his stuff?
• 24:51
  SPEAKER_00: Does the USGS do they contract that out to people like you?
• 24:56
  SPEAKER_01: It's a good question.
• 24:57
  SPEAKER_01: So, well, first of all, the the techniques they're using for these types of studies are not we aren't able to do those.
• 25:03
  SPEAKER_01: So we don't do this young, like I kind of side of alluded to before.
• 25:07
  SPEAKER_01: We don't do stuff this young.
• 25:08
  SPEAKER_01: Our instrument setup is not capable of the resolution.
• 25:11
  SPEAKER_01: We're much better at doing old stuff.
• 25:12
  SPEAKER_01: And even at Carnegie.
• 25:14
  SPEAKER_01: So Carnegie would be a bit different.
• 25:16
  SPEAKER_01: They could do some of this work at Carnegie.
• 25:18
  SPEAKER_01: There, so there are U.S.
• 25:20
  SPEAKER_01: Geological Survey has labs that they run in Reston, Virginia, in Denver, or it's in Lakewood outside of Denver.
• 25:28
  SPEAKER_01: There's a big lab there.
• 25:29
  SPEAKER_01: There's a big facility they run out by Stanford as well.
• 25:32
  SPEAKER_01: So there's both university and government labs that are run, and it kind of depends, right?
• 25:37
  SPEAKER_01: Like I don't know where Mike Poland would send samples to.
• 25:40
  SPEAKER_01: It sort of depends on like who's involved in the project.
• 25:43
  SPEAKER_01: You kind of, when you're thinking about, hey, we're gonna do uh a mapping project, I'm sure they would have thought through where are we gonna do the analyses?
• 25:51
  SPEAKER_01: And do we have a colleague or somebody that can do the analyses for us with us in collaboration who would go along and collect samples and and help guide the sampling strategy and all that stuff.
• 26:01
  SPEAKER_00: So does that mean that there's a possibility for you to transition in that direction?
• 26:06
  SPEAKER_00: Like, are you interested in that at all?
• 26:08
  SPEAKER_01: Like I I I'm I think the it's a good question.
• 26:10
  SPEAKER_01: That's a it's um there's two sides to it.
• 26:12
  SPEAKER_01: So scientifically, yes, it would be very interesting.
• 26:14
  SPEAKER_01: And I think sort of our in our lab, our scientific skill sets like our data interpretation, our igneous petrology, our sort of background knowledge would be very useful to address some of these questions and we'd be interested in that.
• 26:26
  SPEAKER_01: Technologically or instrumentation-wise, not super well suited to that.
• 26:30
  SPEAKER_01: And to become well suited to that, we would have to invest six to ten million dollars in a lab.
• 26:36
  SPEAKER_01: Like getting one of these instruments with the whole lab, it would require upfront cost to buy it, technical support staff to to run it and operate it, like that is a huge investment that universities are very rare to make.
• 26:50
  SPEAKER_01: And so there's probably labs that can do like this zircon dating, dating the rims at the precision that they've done, it's a it's a much bigger, more expensive instrument.
• 26:58
  SPEAKER_01: There's maybe a handful of labs in the United States that do this at that level of precision.
• 27:02
  SPEAKER_01: So yeah, uh, it's kind of in that ballpark.
• 27:04
  SPEAKER_01: There's several places, but not dozens of places that could do these types of analyses.
• 27:08
  SPEAKER_00: Okay, gotcha.
• 27:09
  SPEAKER_00: That makes sense.
• 27:10
  SPEAKER_00: Okay.
• 27:10
  SPEAKER_01: Yeah.
• 27:11
  SPEAKER_01: So like if I was gonna take some students and go to Yellowstone, we would collect some samples, we'd do some preliminary analyses in our lab, and then we'd send the samples to the really, really good facility at Stanford or at the USGS facility to do the the real measurements.
• 27:26
  SPEAKER_01: But we'd do some preliminary work in our lab, probably.
• 27:28
  SPEAKER_00: Cool.
• 27:28
  SPEAKER_00: That makes sense.
• 27:29
  SPEAKER_00: Well, Jesse, um, I think that's a wrap.
• 27:33
  SPEAKER_00: Yeah, I think so.
• 27:34
  SPEAKER_01: I mean, what was what's your what's your like takeaway?
• 27:37
  SPEAKER_01: Yeah, what do you think about the summary here?
• 27:38
  SPEAKER_01: Yeah, what uh for you personally, like what is I mean, it's sort of interesting.
• 27:41
  SPEAKER_01: I th I ask because you've taught so many people Yellowstone geology on this field course.
• 27:46
  SPEAKER_01: You're teaching students in Yellowstone the geology and you talk about these things.
• 27:50
  SPEAKER_01: You taught me geology there.
• 27:51
  SPEAKER_01: So like, you know, I'm curious if you if this has made you sort of re or I don't know, not rethink how you teach it, but are you gonna add little tidbits?
• 27:59
  SPEAKER_01: Because I know you're constantly modifying what you teach and what you cover in the summer science course.
• 28:03
  SPEAKER_00: Yeah, I'm I'm to the point in my career where I have to really curate what I'm gonna add and what I'm not gonna add because uh I, you know, I've learned so much over the years and I have so many personal stories that I want to incorporate into what I teach.
• 28:17
  SPEAKER_00: Um, I'm never satisfied, I'm never happy with it.
• 28:19
  SPEAKER_00: So 100% absolutely, I will be looking at things differently because of what we did with our our guidebook to Yellowstone for sure.
• 28:28
  SPEAKER_00: That's true.
• 28:29
  SPEAKER_00: And because of all the episodes that we've put out there on Yellowstone, including this one.
• 28:33
  SPEAKER_00: It's amazing to me that, you know, in terms of the takeaways, what did we talk about today?
• 28:38
  SPEAKER_00: We talked about how volcanic eruptions are usually events that span more than one just big event.
• 28:45
  SPEAKER_00: It's not a singular thing.
• 28:47
  SPEAKER_00: You know, that's a big takeaway.
• 28:48
  SPEAKER_00: And also what you said, you know, Yellowstone is a really intensely studied area, but yet we're finding out new stuff about it all the time, in large part to Mike Poland.
• 28:59
  SPEAKER_00: I mean, this guy's really prolific in terms of what he puts out there and what he's doing, but that's amazing to me that the map looks completely different.
• 29:08
  SPEAKER_00: The geologic map.
• 29:09
  SPEAKER_01: Yeah, it's so interesting.
• 29:11
  SPEAKER_01: It's so interesting and and really uh cool aspect.
• 29:14
  SPEAKER_00: And also, you know, the geochronology aspect to it.
• 29:17
  SPEAKER_00: I think that's a really I know we've talked about this a lot because this is what you do, right?
• 29:21
  SPEAKER_00: But this this aspect of it is not what you do.
• 29:24
  SPEAKER_00: You just happen to know about it.
• 29:25
  SPEAKER_00: It's amazing to me.
• 29:26
  SPEAKER_00: I it's exciting to me.
• 29:28
  SPEAKER_00: It gets my blood circulating uh faster, you know, when we talk about this, because I think it's just really, really cool that we can date the rim of a zircon grain versus the inside of a zircon grain, and there's enough of a difference between that to give us just unbelievably outstanding information.
• 29:51
  SPEAKER_01: It's a really cool technological advance that frankly was not available 15 years ago or 20 years ago.
• 29:56
  SPEAKER_01: Like this is this is sort of new, new stuff, new techniques.
• 29:59
  SPEAKER_01: And I think Chris, you you touched on it, but our Yellowstone, you know, audiovisual course, we go into a lot more detail on this stuff and a lot more detail into Yellowstone National Park.
• 30:08
  SPEAKER_01: So the first link in your show notes, it's sitting right next to the Camp Geo course content, or click on that first link in your show notes, and that's been really fun to put together.
• 30:15
  SPEAKER_01: And, you know, Chris, you and I are both extremely passionate about Yellowstone National Park, or all national parks for that matter, and it I think provides a deeper, more enriching experience when you're going to these places to know something about the geology, to look at Old Faithful and know, oh, that's how the plumbing system works.
• 30:31
  SPEAKER_01: There's this really cool camera footage that goes down inside of Old Faithful, and here's how a geyser is actually working.
• 30:38
  SPEAKER_01: Like that just adds to the experience of walking around in the same way that understanding how geological maps work and how these lava flows will stack on top of each other makes it more interesting to look at the hill where there's a bunch of rhylite or tufts interbedded, right?
• 30:52
  SPEAKER_01: It just makes it a better experience.
• 30:54
  SPEAKER_00: That's right.
• 30:54
  SPEAKER_00: Because the more you know, the more connected you are.
• 30:57
  SPEAKER_00: I mean, it's just as simple as that.
• 30:59
  SPEAKER_01: Absolutely.
• 31:00
  SPEAKER_01: Hey, that's a wrap.
• 31:01
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• 31:03
  SPEAKER_01: We're at Planet Geocast.
• 31:04
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• 31:12
  SPEAKER_01: There you can learn about us, see all the past episodes with transcripts, and support us.
• 31:17
  SPEAKER_01: A few of you have done that recently, and we really, really appreciate that.
• 31:21
  SPEAKER_01: Cheers.
• 31:22
  SPEAKER_01: Peace.