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Yellowstone's Other Volcanoes · 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: Take that last gulp of coffee there, boy.
0:15
SPEAKER_01: Watson is giving me the eye.
0:17
SPEAKER_01: Like, should you be quiet over there?
0:18
SPEAKER_01: It's nap time.
0:19
SPEAKER_01: What is going on here?
0:21
SPEAKER_00: See, Tubbs can't hear a thing.
0:23
SPEAKER_00: So he's he doesn't even move.
0:28
SPEAKER_00: All right.
0:29
SPEAKER_00: Hey, let's get the show on the road.
0:30
SPEAKER_00: Dr.
0:30
SPEAKER_00: Rymank, what do you say?
0:32
SPEAKER_00: Christopher, what's up, man?
0:33
SPEAKER_00: How you doing, Jesse?
0:34
SPEAKER_00: I'm great.
0:35
SPEAKER_00: Hey, look at look at me.
0:37
SPEAKER_00: Oh, you got your Yellowstone shirt on today.
0:39
SPEAKER_00: I'm wearing my Yellowstone.
0:40
SPEAKER_00: Did you plan that?
0:40
SPEAKER_01: I did.
0:41
SPEAKER_01: I didn't.
0:41
SPEAKER_01: Did you plan that?
0:42
SPEAKER_01: Well, actually, to be honest, I put I put it on yesterday, knowing that we were going to record today, and knowing that whatever shirt I took off last night, I was going to put on this morning before recording.
0:53
SPEAKER_01: So I was thinking ahead.
0:54
SPEAKER_01: But yeah, I'm wearing my Yellowstone National Park shirt today.
0:56
SPEAKER_01: Because we're talking about Yellowstone, man.
0:58
SPEAKER_00: We are.
0:59
SPEAKER_00: We're actually going to talk about an underappreciated part of Yellowstone today.
1:02
SPEAKER_00: I'm excited to go because I don't know why it's underappreciated.
1:06
SPEAKER_00: It shouldn't be.
1:06
SPEAKER_00: They are awesome.
1:07
SPEAKER_00: So, Jesse, what are we talking about?
1:10
SPEAKER_01: Yellowstone's other volcanoes is the title of this one.
1:13
SPEAKER_01: And it's really the Absaricas.
1:15
SPEAKER_01: This is a volcanic, uh, a suite of volcanic rocks that exists in just in the park and a lot outside of the park to the northeast side.
1:24
SPEAKER_01: Basically, it runs kind of northwest to southeast orientation, right?
1:28
SPEAKER_01: The observa volcanics, right?
1:30
SPEAKER_01: But it's a huge amount of rock.
1:32
SPEAKER_01: So underappreciated.
1:33
SPEAKER_01: Why do you say underappreciated, Chris?
1:34
SPEAKER_01: I mean, you go and you teach Yellowstone geology to the summer science class every year.
1:39
SPEAKER_01: You spend, what do you spend, a week?
1:40
SPEAKER_01: Actually, I got this shirt.
1:41
SPEAKER_01: Last time we were together in Yellowstone was when I got this shirt in 2019 when I was out with your class.
1:46
SPEAKER_01: Do you spend a week there?
1:47
SPEAKER_01: Five nights?
1:48
SPEAKER_01: What is it?
1:49
SPEAKER_00: Five days, yes.
1:50
SPEAKER_00: On a three-week geology field course, we spend five days there.
1:53
SPEAKER_00: It's varied over time because I've done this a long time, like 25 years.
1:57
SPEAKER_00: And so in the early days when you went with me as a student, I think we probably spent seven or more days there, but we've incorporated other things into it.
2:06
SPEAKER_01: So you say the obsuricas is an underappreciated part of Yellowstone.
2:10
SPEAKER_01: How much time do you spend on it?
2:11
SPEAKER_01: And how much time do you spend on it?
2:16
SPEAKER_01: And well, I want to I'm curious how much time you spend talking about it, but also like what percentage of the boardwalk signs in Yellowstone National Park talk about the obsericus?
2:25
SPEAKER_01: Like you know, that's that's kind of my question.
2:29
SPEAKER_00: I call them the underappreciated aspect or the underappreciated volcanoes because there is no boardwalk around it, there's no park signage that speaks to the observas.
2:41
SPEAKER_00: By the way, I do want to say this too.
2:42
SPEAKER_00: Pronunciation-wise, I don't know what's correct.
2:45
SPEAKER_00: It's I've heard them pronounced abserokas.
2:48
SPEAKER_00: I've always said absoricas, and I've heard them pronounced both ways by people that I respect.
2:54
SPEAKER_00: And so I don't know if there's a real consensus on the bigger thing.
2:59
SPEAKER_01: You we won't ask you, and in the phrase that comes to mind is old dog and new tricks.
3:04
SPEAKER_01: So we won't ask you to repronounce them.
3:06
SPEAKER_01: What I'll try and do, I'll try and say absorkas, just to kind of let's play, you know, be fair about this.
3:11
SPEAKER_01: How about that?
3:12
SPEAKER_00: We got our field basis covered.
3:14
SPEAKER_00: But you asked me how much time I spend in the absericas.
3:19
SPEAKER_00: And I'm gonna I'm gonna say a solid day and a half, because one of the best places, in my opinion, to see the absericas is on a hike, the Avalanche Peak hike, which is on the East Entrance Road.
3:34
SPEAKER_00: In my opinion, and it is just my opinion, it is the best hike in the park, and you just get these absolutely stunning views of these highly eroded ancient volcanoes.
3:46
SPEAKER_00: And and so that's a whole day.
3:48
SPEAKER_01: Let me interrupt you there, real quick, Chris, because I want to interject and say that we're part of the reason we're releasing this particular episode right now is because we are also releasing on the Camp Geo website, geo.campcourses.com, we have just made available something we're super excited about a Yellowstone National Park geology visual audiobook.
4:08
SPEAKER_01: It's kind of the same theme, the same style as Camp Geo, audio discussions with images deeply embedded, and we cover a lot of different content there.
4:17
SPEAKER_01: Currently, we've got 12 chapters up there.
4:19
SPEAKER_01: It's available if you just go to geo.campcourses.com.
4:22
SPEAKER_01: We cover everything from human history of the park to the really important sort of Hall of Fame geological features like Old Faithful, Yellowstone Lake.
4:29
SPEAKER_01: We talk about the Absaricas or the Absorokas as well.
4:33
SPEAKER_01: Um, so we have chapters covering these major themes, and it's all about really the geology of Yellowstone Park, which is a super special place that, and I want to come back to why we chose Yellowstone to do this for Chris.
4:46
SPEAKER_01: But I think we should highlight one thing.
4:47
SPEAKER_01: It's not a field trip guide, it's not like a road trip guide.
4:52
SPEAKER_01: Is that right?
4:52
SPEAKER_01: What like because you do a road trip guide, Chris, and we talked about like should we do that or not?
4:58
SPEAKER_01: I don't know what Right.
4:59
SPEAKER_00: We did.
4:59
SPEAKER_00: We had a lot of discussions about this.
5:01
SPEAKER_00: This is a complete guide book, if you will, but it's not a tour guidebook.
5:05
SPEAKER_00: It's not go to this stop first, then go to stop two.
5:09
SPEAKER_00: All of the chapters cover the in-depth uh story behind all of the features inside of Yellowstone National Park.
5:17
SPEAKER_00: And so you get to pick and choose where you're gonna be on a particular day, and you can listen in on this and bone up on those particular aspects of Yellowstone, or you're on a drive to the park and you've got time, and you can just go through chapters one through twelve.
5:35
SPEAKER_00: I mean, it this is a complete thorough geologic understanding of everything inside of Yellowstone National Park.
5:43
SPEAKER_01: And Chris, you phrased it really nicely in this.
5:45
SPEAKER_01: You sort of said early on, I don't want to impose my field plan, my trip plan onto anybody else.
5:53
SPEAKER_01: Like, I want to let people experience the park the way they want to experience it.
5:56
SPEAKER_01: If you have two days to spend somewhere and you really want to spend two days, go do that.
6:00
SPEAKER_01: Like, we shouldn't be telling you how to spend your time in Yellowstone, but we want to give you all of the background knowledge you need to really fully, deeply appreciate the park more because you got to learn and listen and see some images and the sort of deeper geological dives that we go into in this Yellowstone book.
6:18
SPEAKER_00: That's right.
6:19
SPEAKER_00: Our idea is to give the listener a different lens to view the park through the lens of understanding, and it just deepens your appreciation.
6:29
SPEAKER_00: I don't know.
6:30
SPEAKER_00: It our hope is that this will make you look at things I'm gonna say quite differently.
6:35
SPEAKER_00: I mean, that's our goal.
6:36
SPEAKER_01: Like I agree, I agree completely, Chris.
6:38
SPEAKER_01: And yet, you know, we have a thing on mud pots.
6:41
SPEAKER_01: Like you should look at mud pots and you should be able to understand how the reason it's a mud pot is because there's limited water and there's more acidity, and so it's dissolving the rock, like all those extra things.
6:51
SPEAKER_01: Mud pots are one of the most fun things to just sit there and watch.
6:55
SPEAKER_01: And watching them with the geological knowledge that we convey in this book, it makes it a more fun, more intimate experience, I think.
7:03
SPEAKER_01: So, yeah, I'm just it's really special.
7:05
SPEAKER_00: That's right.
7:06
SPEAKER_00: And this also brings us to that point.
7:08
SPEAKER_00: I've been teaching geology inside Yellowstone National Park for the better part of 25 years.
7:14
SPEAKER_01: Um, this is a place that I feel very comfortable with which is at least one third of your life, right?
7:19
SPEAKER_01: 25.
7:21
SPEAKER_00: Okay.
7:22
SPEAKER_00: Yeah, yeah.
7:23
SPEAKER_00: Nope.
7:23
SPEAKER_00: I'm not I'm not 75.
7:25
SPEAKER_00: Not that that would be a bad thing, but I I'm not.
7:28
SPEAKER_00: But yeah, it's uh I feel very comfortable with my knowledge, my expertise with all things Yellowstone.
7:36
SPEAKER_00: And and you know, you're Dr.
7:37
SPEAKER_00: Rymank.
7:38
SPEAKER_00: You you're one of my former students, and you've eclipsed me educationally a long time back, but you bring to the table this kind of research background kind of thing.
7:49
SPEAKER_00: But we come at this from two very different angles, and I think that's a it's a chemistry that works.
7:55
SPEAKER_00: And I I really think this is just a it's an uh outstanding product.
7:59
SPEAKER_01: Yeah, I think so too.
8:00
SPEAKER_01: I'm very excited to have this be available.
8:02
SPEAKER_01: And again, you can go to geo.campcourses.com.
8:05
SPEAKER_01: It's the first link in your show notes.
8:07
SPEAKER_01: If you've already logged into our Camp Geo product, it is available there for you.
8:12
SPEAKER_01: The home screen now shows another course, it shows Camp Geo, which is still free and available.
8:17
SPEAKER_01: You can look at that, you can learn all the basics of geology, the way we teach it in our introductory class.
8:22
SPEAKER_01: There's also a Yellowstone audiobook there, too, and that has 12 chapters, and we've talked about what we cover in there, but that is just available on the same platform.
8:31
SPEAKER_01: So head to geo.campcourses.com.
8:33
SPEAKER_01: It's available there.
8:35
SPEAKER_01: Okay, Chris.
8:36
SPEAKER_00: I think I want to say one other thing before we move into that.
8:39
SPEAKER_00: And if you happen to see an out-of-place yellow, big yellow school bus, that's probably me.
8:46
SPEAKER_01: That's right.
8:47
SPEAKER_01: If you see a big yellow school bus in Yellowstone, go say hi because it's Chris Bullheis leading the trip.
8:52
SPEAKER_01: You could probably go for dinner at the campsite with the students or go hang out and go on a hike with them the next day or something like that.
8:59
SPEAKER_01: So go say hi to Chris if you see the huts of a public school's bus driving around.
9:03
SPEAKER_01: All right, Chris.
9:04
SPEAKER_01: Hey, let's get back to Yellowstone's other volcanoes.
9:06
SPEAKER_01: And like we said, there is a chapter in the Yellowstone book on the Camp Geo app that covers the Abserkas or excuse me, Abserokas, let me say it properly, and uh in my version, the Abserokas.
9:17
SPEAKER_01: But let's cover, we're gonna dive deep into some of the geology aspects of these things because they're really unique and kind of curious things, I think.
9:25
SPEAKER_01: So maybe you can set the time frame for us, Chris.
9:27
SPEAKER_00: I think we need to differentiate between these volcanoes and what Yellowstone is known for, the Yellowstone hotspot.
9:34
SPEAKER_00: These are two very different eras of volcanism.
9:38
SPEAKER_00: The absericas, we're talking about volcanoes that are old.
9:41
SPEAKER_00: These are 43 to 53 million years ago.
9:45
SPEAKER_00: So these are old, eroded, dormant, extinct volcanoes, as opposed to the Yellowstone hotspot, where there have been three cataclysmic eruptions in the last 2.1 million years.
9:59
SPEAKER_00: That's what everyone knows about Yellowstone.
10:02
SPEAKER_00: So these are kind of like neglected, kind of these other volcanoes, and they shouldn't be, but they are.
10:08
SPEAKER_01: They are.
10:09
SPEAKER_01: That's exactly right.
10:09
SPEAKER_01: And these are also older than anything else in the Yellowstone hotspot track.
10:13
SPEAKER_01: So if you're familiar with that region, you know the Snake River Plain is a hotspot track.
10:17
SPEAKER_01: We've talked about this in our old Yellowstone episode.
10:20
SPEAKER_01: The one of our first episodes we ever released in Planet Geo was a Yellowstone National Park one.
10:24
SPEAKER_01: We talked about the hotspot track.
10:26
SPEAKER_01: The oldest eruptions in the hotspot track are just under 17 million years old.
10:30
SPEAKER_01: These are 43 to 53 million year old volcanic rocks that we're talking about.
10:35
SPEAKER_00: Right, Jesse.
10:35
SPEAKER_00: But I want to ask you, why do I keep saying these volcanoes deserve respect?
10:41
SPEAKER_00: They should not be underrepresented.
10:44
SPEAKER_00: They should not be undervalued.
10:45
SPEAKER_01: Why?
10:46
SPEAKER_01: Chris, you're asking me to get into your mind, which is always a difficult place to go, man.
10:52
SPEAKER_01: But let me, I think the reason is because they're massive.
10:55
SPEAKER_01: The volumes here are enormous.
10:57
SPEAKER_01: So let me just list some numbers.
10:58
SPEAKER_01: Is that right, Chris?
10:59
SPEAKER_01: Is that your your main?
11:01
SPEAKER_01: Yeah, this is where you're going, right?
11:02
SPEAKER_01: This is why you spend a day and a half out of five in Yellowstone National Park on these volcanoes and these rocks.
11:08
SPEAKER_01: They're huge.
11:09
SPEAKER_01: The cumulative volume that was erupted out of the Abserokas is greater than 7,000 cubic miles, which is equivalent of greater than 29,000 kilometers, cubic kilometers of volcanic material.
11:23
SPEAKER_00: Compare that to what Yellowstone has done.
11:25
SPEAKER_01: Oh, yes, good point.
11:26
SPEAKER_01: The current Yellowstone hotspot, so the three major eruptions in Yellowstone in the last 2 million years or last 2.1 million years have erupted less than 1,100 cubic miles.
11:35
SPEAKER_01: So Abserokas greater than 7,000, Yellowstone hotspot less than 1,100, and that's 4,600 cubic kilometers, so 29,000 cubic kilometers compared to 4,600 cubic kilometers.
11:48
SPEAKER_01: A dramatic difference.
11:49
SPEAKER_00: A couple things, Jesse.
11:50
SPEAKER_00: That means that these volcanoes dwarf what the Yellowstone supervolcano has done, these biblical eruptions, these last three eruptions in the last 2.1 million years.
12:01
SPEAKER_00: Jesse, how do we know this?
12:02
SPEAKER_00: Like, how are we getting these numbers?
12:04
SPEAKER_00: You said greater than 7,000 cubic miles.
12:07
SPEAKER_00: How where's that coming from?
12:09
SPEAKER_00: How do we know?
12:10
SPEAKER_01: Yeah, this comes from geologic mapping.
12:12
SPEAKER_01: So going out looking at the volcanic rocks themselves, understanding, okay, if you sort of map the aerial extent, the thickness of an ash bed or the thickness of an ignimbrite, the lava flow, and add those all up, and you kind of get a rough estimate of the cumulative volume of stuff that comes out.
12:27
SPEAKER_01: But it's not just the lava flows, it's not just the igneous rocks that get incorporated into this average, Chris.
12:33
SPEAKER_01: And why is that?
12:34
SPEAKER_01: Why do we not just focus on lava flows or ash flows or ignimbrites?
12:38
SPEAKER_00: Because another really important piece of the puzzle are these volcanic mud flows called lahars.
12:44
SPEAKER_00: We're talking about all of the associated rocks from these volcanoes, which includes a significant amount of sedimentary rocks because of these mud flow kind of deposits.
12:54
SPEAKER_01: And let me just paint a picture here, Chris, because you love Mount St.
12:57
SPEAKER_01: Helens, and I think Mount St.
12:58
SPEAKER_01: Helens provides a great visual for understanding this.
13:00
SPEAKER_01: So, you know, Mount St.
13:01
SPEAKER_01: Helens erupts.
13:02
SPEAKER_01: We all see these pictures of knockdown trees everywhere and ash fall, and those ash falls would become potentially an igneous rock, an igneous lava flow or igneous ash fall.
13:13
SPEAKER_01: But you and I went there, Chris, in what 2010, maybe for the Geological Society of America conference?
13:19
SPEAKER_01: Was it 2011?
13:20
SPEAKER_01: Somewhere in that case.
13:21
SPEAKER_01: I don't know, somewhere in there, yeah.
13:22
SPEAKER_01: And we went on a hike and and you walk through, we walk, we didn't walk into the crater, but we walked up on the flanks and we walked through this landscape.
13:29
SPEAKER_01: And even 30 years later, this is still like a desolate landscape, but there are streams flowing through this area.
13:36
SPEAKER_01: There's all sorts of erosional activity happening to this ash deposit because it's not yet lithified into a rock.
13:42
SPEAKER_01: So this is like relatively recent sedimentary remobilization of the material.
13:47
SPEAKER_01: And so if you want to calculate the volume of stuff that came out of Mount St.
13:51
SPEAKER_01: Helens 10 million years into the future, if you're looking back 10 million years, you obviously want to look at all the volcanic rocks, but you also want to look at those very recently or very rapidly derived sedimentary rocks, what we call volcanoclastic or volcanogenic sedimentary rocks, which are basically like sediments formed right on the flanks of the volcanoes.
14:10
SPEAKER_00: Well, Jesse, let's transition then into what formed these volcanoes?
14:14
SPEAKER_00: What are the tectonics of the absericas?
14:17
SPEAKER_00: And this is a really interesting part to this, and it it bothers me, I think, more than it does you.
14:22
SPEAKER_00: And I I don't that's an interesting thing.
14:25
SPEAKER_00: But you and I have had this discussion because it bothers me that there's no real consensus on exactly how the absericas formed.
14:34
SPEAKER_00: We have two leading ideas, but both of the ideas have problems, and that part of it bothers me.
14:40
SPEAKER_00: And you're like, Well, Chris, you need to relax a little bit.
14:42
SPEAKER_00: You know, it's okay that we don't know.
14:44
SPEAKER_00: And so that was the discussion.
14:46
SPEAKER_01: I I sort of, well, here's the thing.
14:48
SPEAKER_01: I think the the reason that I get excited, maybe more than worried by these sorts of unknown questions is it's job security for me, to be honest.
14:56
SPEAKER_01: Okay.
14:57
SPEAKER_01: All right.
14:58
SPEAKER_01: All right.
14:58
SPEAKER_01: You're a real piece of work.
14:59
SPEAKER_00: The more things we don't know is uh, you know, better job security.
15:02
SPEAKER_00: So well, Jesse, there are two ideas here, two leading ideas in the formation of the absericas.
15:08
SPEAKER_00: Like I said, both of them have problems.
15:10
SPEAKER_00: One is that they're related to the Laromatarogeny, this odd subduction zone, mountain building event that formed a massive part of the Rocky Mountains.
15:20
SPEAKER_00: The reason why this is a leading theory and a leading idea is because the chemistry of the rocks, the chemistry of the obsericas, fits the typical chemistry that we see with subduction-related volcanoes.
15:32
SPEAKER_00: In other words, go back to the Mount St.
15:34
SPEAKER_00: Helens analogy, the same kind of rocks that we see at Mount St.
15:37
SPEAKER_00: Helens, these are the same rocks that you're walking all over and around when you're climbing in the obsericas.
15:43
SPEAKER_01: So, Chris, let me just we were mentioning geochemistry, so I have to try and go down a rabbit hole and you have to pull me back out, right?
15:49
SPEAKER_00: That's our Because you're the geochemist in the house.
15:52
SPEAKER_01: The subduction zone signature, this chemical signature, what we're talking about is fluid elements or elements that like to be in fluid or can be in fluid.
16:00
SPEAKER_01: So a subduction zone like Mount St.
16:02
SPEAKER_01: Helens, there's a lot of water involved in the generation of that magma.
16:06
SPEAKER_01: The subducting slab, the oceanic slab, is bringing water down in the mantle, it's melting the mantle.
16:11
SPEAKER_01: So there's water around.
16:12
SPEAKER_01: So things like uranium, barium, rubidium, a lot of these elements that are mobilized in water will be enriched, will be a higher concentration in subduction zone rocks like Mount St.
16:22
SPEAKER_01: Helens.
16:23
SPEAKER_01: And the absorokas have that sort of quote unquote fluid signature in it, where there's fluid involved in the generation of the magma, like water involved in the generation of the magma.
16:34
SPEAKER_01: So that's the chemistry signal we're talking about.
16:36
SPEAKER_01: That's a quote unquote subduction zone signal.
16:39
SPEAKER_00: But the problem is, is really two things that are like uh barriers to this as being like, oh, the accepted theory.
16:47
SPEAKER_00: One is the absericas are a thousand miles away from the nearest subduction zone.
16:52
SPEAKER_00: And that's that's a long way.
16:56
SPEAKER_00: That's a long ways.
16:57
SPEAKER_00: The other thing is they're a little too young.
17:00
SPEAKER_00: They happened after the Laromiterogeny.
17:03
SPEAKER_00: And so those are barriers to entry for this, like the accepted idea.
17:07
SPEAKER_00: So, Jesse, what's the other one?
17:09
SPEAKER_01: Well, the other idea is uh another common feature we see in the southwestern U.S.
17:14
SPEAKER_01: specifically, and up in this part of the northwestern United States as well, is basin and range extension or just extensional melting.
17:21
SPEAKER_01: And so the way to think about this is, Chris, we've talked about this before.
17:24
SPEAKER_01: We talked about it in the Camp Geo Igneous Rocks chapter, is there's a couple ways to melt rocks.
17:29
SPEAKER_01: You can either add water, you can decrease the pressure, or you can increase the temperature.
17:34
SPEAKER_01: And extension, when you pull apart the crust, the mantle underneath upwells, and that is decrease in pressure.
17:41
SPEAKER_01: So that upwelling mantle, just like what happens at a mid-ocean ridge setting, the mantle could melt and form magma that then ultimately differentiates to form these volcanoes.
17:50
SPEAKER_01: And this happens a lot.
17:51
SPEAKER_01: We know that this type of thing is.
17:53
SPEAKER_00: So, Jesse, hold on.
17:54
SPEAKER_00: What you're talking about is if you take rock that has a very high temperature, but it's under a lot of pressure.
17:59
SPEAKER_00: It has high temperature and high pressure.
18:02
SPEAKER_00: If you reduce the pressure but leave the temperature alone, that rock, or maybe some of the rock anyway, will melt, right?
18:10
SPEAKER_00: You're that's what you're talking about, right?
18:12
SPEAKER_00: That's that's that pressure relief melting.
18:14
SPEAKER_00: Take a rock that is at a very high temperature, reduce the pressure, and some of that rock is gonna melt.
18:20
SPEAKER_01: That's exactly right.
18:21
SPEAKER_01: And so this happens.
18:22
SPEAKER_01: We know this happens in a lot of areas in the western United States.
18:26
SPEAKER_01: This extensional melting is going on, producing little volcanoes.
18:30
SPEAKER_01: The problem here is that the chemistry doesn't really fit.
18:33
SPEAKER_01: So remember, I said that that water signature, you had mentioned that the chemistry matches subduction zones.
18:37
SPEAKER_01: So we have this kind of watery signature in the chemistry.
18:40
SPEAKER_01: That's not typical of extensional melt regimes or extensional melting.
18:45
SPEAKER_01: It's not typical of decompression melting.
18:47
SPEAKER_01: And the other problem is that extensional melting map.
18:49
SPEAKER_00: Well, hold on a minute, Jesse.
18:50
SPEAKER_00: I have a question for you then.
18:51
SPEAKER_00: What would the typical rock look like with extensional melting?
18:54
SPEAKER_01: Great question.
18:55
SPEAKER_01: It's usually low volumes of melt.
18:58
SPEAKER_01: Well, it's usually basaltic.
19:00
SPEAKER_00: There's usually a lot of basalt that comes up because you're Which is a very black basalt is the most common rock on the surface of the earth anyway, because it's what makes up all of the ocean floor, basically.
19:10
SPEAKER_01: Exactly.
19:10
SPEAKER_01: So, okay, sorry to interrupt.
19:12
SPEAKER_01: Go ahead.
19:12
SPEAKER_01: No, that's a great question.
19:13
SPEAKER_01: So, first of all, it's like more mafic typically, and also doesn't have this fluid-y signature, this fluid chemical signature to it.
19:20
SPEAKER_01: And so it's usually dry, quote unquote, dry melting.
19:23
SPEAKER_01: And so it the chemistry doesn't fit, and the volumes don't really fit.
19:26
SPEAKER_01: Usually, extensional environments are relatively low volumes of melt, not more than 29,000 cubic kilometers of lava coming out.
19:34
SPEAKER_01: Okay, yeah.
19:35
SPEAKER_01: So too much and not the right chemistry.
19:37
SPEAKER_01: Exactly, exactly.
19:38
SPEAKER_01: So there's a bit of debate about this tectonic setting, which I think is a really interesting problem.
19:42
SPEAKER_01: That these are this is a massive volcanic episode here, and this should have been figured out by now.
19:48
SPEAKER_00: It is very unsettling.
19:49
SPEAKER_00: This should have been figured out.
19:50
SPEAKER_00: Like you, you PhDs, you doctors need to figure this out.
19:53
SPEAKER_01: Uh, what are we doing?
19:54
SPEAKER_01: Just we're just sitting around on our duffs over here, not doing anything.
19:57
SPEAKER_01: I mean, my goodness.
19:58
SPEAKER_01: Somebody get on this.
19:59
SPEAKER_00: Jesse, let's talk about some things that you can see.
20:02
SPEAKER_00: One of the things that we can see is these really cool features that are called radiating dikes.
20:06
SPEAKER_00: A dike is a is a term in geology that we use for this, it cuts across the rocks.
20:11
SPEAKER_00: It's this igneous intrusion that kind of cross-cuts rocks.
20:15
SPEAKER_00: But these radiating dikes, they resemble spokes on a wheel that lead to these volcanic centers.
20:21
SPEAKER_00: Yes, and there are twelve.
20:23
SPEAKER_01: Yeah.
20:23
SPEAKER_01: What is a volcanic center first?
20:25
SPEAKER_01: Define sort of what we mean by volcanic center.
20:27
SPEAKER_00: I think the best way for me to explain this is a volcanic center is where the plumbing system beneath the surface of the earth leads to one area where the volcanism is concentrated.
20:40
SPEAKER_00: And so we have these 12 volcanic centers or areas where this all the volcanic activity is kind of concentrated within this Absarica mountain range.
20:50
SPEAKER_00: Does that make sense?
20:51
SPEAKER_00: Is that right?
20:51
SPEAKER_01: Yeah, for sure.
20:52
SPEAKER_01: Like you imagine the Cascade subduction zone on the northwest of the United States, a subduction zone going down, but the volcanic centers are Mount St.
20:58
SPEAKER_01: Helens, Mount Hood, Mount Shasta, right?
21:00
SPEAKER_01: Those are the volcanic kind of centers that are aggregating all of the melt along this.
21:04
SPEAKER_01: So, okay, spokes on a wheel.
21:06
SPEAKER_01: These radiating dikes are really cool.
21:07
SPEAKER_01: And I think the visual, Chris, for me is always thinking about these spokes on a wheel.
21:11
SPEAKER_01: These things are the plumbing system, as you said, feeding into the middle, the sort of main conduit, the central conduit to the surface.
21:18
SPEAKER_01: And the way to visualize this is punching your fist up through like a cake or a loaf of bread or something like that, right?
21:25
SPEAKER_01: It kind of bulges up in cracks, and those cracks expand out radially.
21:29
SPEAKER_01: Maybe punching your fist up through a bunch of mud.
21:32
SPEAKER_01: And the cracks will kind of happen radially away from this thing to the central plumbing point, the point that comes up to the surface.
21:39
SPEAKER_01: And so we can see these in this area and help identify the 12 volcanic centers, right?
21:44
SPEAKER_00: And the other thing that I think is kind of neat and maybe counterintuitive to people that are don't have a deep background in geology is that what feeds these volcanic centers is not really tubular.
21:55
SPEAKER_00: It's more tabular.
21:57
SPEAKER_00: These are sheet like intrusions.
22:00
SPEAKER_00: That you can just clearly see as you're driving.
22:02
SPEAKER_00: I think one of the best places to see these radio dykes is coming from Cody into Yellowstone National Park on the east entrance road.
22:10
SPEAKER_00: Very, very obvious.
22:12
SPEAKER_00: It doesn't take a trained eye to see these tabular-like things that kind of go towards a central point.
22:18
SPEAKER_01: That's a great point, Chris.
22:19
SPEAKER_01: And there's very few things, and we talk about this in the Yellowstone book as well.
22:23
SPEAKER_01: There's very few things that are actually circular or tubular in geology.
22:27
SPEAKER_01: Even Old Faithful.
22:28
SPEAKER_01: You know, the plumbing system to Old Faithful is not tubular, right?
22:31
SPEAKER_01: And that that's this is a sort of there's very few things that are really circular tubular things.
22:36
SPEAKER_01: Most things are like veins, quartz veins.
22:39
SPEAKER_01: They're kind of long tabular things.
22:40
SPEAKER_00: Well, Jesse, let's go ahead then and talk about one other really cool aspect to the absorption volcano.
22:46
SPEAKER_01: This is one of the best features of the whole region, too.
22:49
SPEAKER_01: It's so cool.
22:50
SPEAKER_00: I we go into this in a lot of detail in the book.
22:54
SPEAKER_01: With some really cool images, Chris, with some beautiful graphics as well that we can't show on a podcast, hence the book.
23:00
SPEAKER_00: That's true.
23:01
SPEAKER_00: And this is the fossil forests of Yellowstone National Park.
23:04
SPEAKER_00: And it really, this story is to me one of the coolest stories of scientific discovery.
23:11
SPEAKER_00: It's an inspiring kind of thing.
23:13
SPEAKER_00: Because what I'm alluding to are we have in Yellowstone buried like stacked books are these deposits that have petrified wood, beautifully preserved petrified wood in these layers.
23:28
SPEAKER_00: And they tell just this amazing story of the climate that existed during this time period.
23:34
SPEAKER_00: And again, this is 43 to 53 million years ago.
23:37
SPEAKER_00: It was a very different climate.
23:40
SPEAKER_00: And we know this because of the flora and fauna that is preserved in these layers.
23:45
SPEAKER_00: Jesse, what was the climate like?
23:47
SPEAKER_00: Just a real brief summary.
23:49
SPEAKER_01: Yeah, without going into too much detail, it was a lot warmer.
23:52
SPEAKER_01: There was a lot of the species of trees, the types of plants that are fossilized here represent a much warmer, much wetter climate than we currently have.
24:02
SPEAKER_01: And looking at the species of trees can tell us actually ancient paleotopography as well, because assuming the climate's the same in a region, you can look at, okay, well, are there cooler trees at higher elevations and trees that like warmer, wetter stuff down in the swampy regions?
24:18
SPEAKER_01: And we can see this by looking at the fossil forests.
24:20
SPEAKER_01: And it's, you're right, Chris, just a totally cool story, an amazing.
24:24
SPEAKER_01: I was never really that excited about fossils, like in my undergrad and even grad school days.
24:30
SPEAKER_01: Like I didn't really enjoy that aspect of geology.
24:35
SPEAKER_01: Like I very much was focused on cool sedimentary rocks or mostly igneous and metamorphic rocks.
24:40
SPEAKER_01: Like that's really what kind of grabs me and gets my passion going.
24:44
SPEAKER_01: So fossils have it always take a little bit of convincing to you know really pay attention if there's a seminar on paleontology or something.
24:52
SPEAKER_01: I always uh kind of drift a little bit more, Chris.
24:54
SPEAKER_01: I don't know.
24:55
SPEAKER_01: Do you do this too?
24:55
SPEAKER_01: Do you feel this way?
24:56
SPEAKER_00: Or I do, I do, but not with this, because the fossils tell the geologic story.
25:01
SPEAKER_01: And that's where I was gonna go, is that this is one of those where I just do not need any convincing that these petrified forests, and that word says it all, is that you have forests of petrified wood.
25:11
SPEAKER_01: It's not just one petrified stump sitting somewhere, it's forests of this stuff, and it tells this amazing story.
25:16
SPEAKER_00: Jesse, we're gonna go ahead and kind of wrap this up because we're getting a little long in the tooth here.
25:21
SPEAKER_00: But in the guidebook, in this audio visual book, we do point to specific locations that you can go and see this petrified wood.
25:31
SPEAKER_00: And some of them are easy, just a short little walk from your car, and some of them involve for those of you that have to get out and do some some you know exploration and go get a little sweat going on and so on.
25:42
SPEAKER_00: There are other recommendations for those as well.
25:45
SPEAKER_01: If you're Chris Bullis and you just gotta get a little walk-in every day, then you know there's some places for you as well to go check it out, right?
25:52
SPEAKER_00: You did allude to us, you and I at Mount St.
25:54
SPEAKER_00: Helens, and you said that we were walking around, and that is not a true statement.
25:58
SPEAKER_00: We had a very limited amount of time.
26:00
SPEAKER_00: I think we only had about four hours, and we ran probably 75% of the time.
26:07
SPEAKER_00: Yes.
26:07
SPEAKER_00: I mean, we were jogging and we were going from place to place to place, literally running along the trail.
26:13
SPEAKER_01: And I think, Chris, we were up at 3 a.m.
26:15
SPEAKER_01: that day, too, to to drive there to like be able to even just get a whiff of Mount St.
26:20
SPEAKER_01: Helens hike in, right?
26:22
SPEAKER_01: And that was an absolute just super time sensitive one.
26:25
SPEAKER_01: We crushed it.
26:26
SPEAKER_01: Do you remember finding a sandwich?
26:29
SPEAKER_01: Yes, we did find a sandwich.
26:31
SPEAKER_01: That's right.
26:32
SPEAKER_01: Just a random sandwich laying along the side of the path.
26:36
SPEAKER_00: That was fun.
26:37
SPEAKER_00: It was all wrapped up and it was neatly wrapped up, and we were like, well, we're not gonna let this sandwich go to waste, which I can't believe we did that, but we did.
26:44
SPEAKER_00: You know, we ate the sandwich.
26:45
SPEAKER_01: Yeah, there we go.
26:46
SPEAKER_01: Hey, on Mount St.
26:46
SPEAKER_01: Helens, on a Mount St.
26:48
SPEAKER_01: Helens sprint slash hike.
26:51
SPEAKER_01: Oh, that was fun.
26:52
SPEAKER_01: Hey, Chris, I I you know, this uh story about the Ab Sirokas is just really cool.
26:57
SPEAKER_01: I think the really cool thing, and I'm I don't know, yeah, you're right.
27:00
SPEAKER_01: Somebody's got to figure this out.
27:02
SPEAKER_01: Somebody's gotta like understand or really kind of nail this down.
27:05
SPEAKER_01: How did they form?
27:06
SPEAKER_01: What's the ancient tectonic setting?
27:08
SPEAKER_01: It's a really interesting geological curiosity that a problem that needs to be solved for sure.
27:13
SPEAKER_00: Hey, isn't this right up your alley?
27:15
SPEAKER_00: Why don't you tackle this problem?
27:16
SPEAKER_00: Get one of your doctoral students on it.
27:18
SPEAKER_01: There we go.
27:19
SPEAKER_01: Get one get a PhD student working on this.
27:20
SPEAKER_01: We'll try and get a grant funded to go work, go out there and work with uh some of the Yellowstone Volcano Observatory people.
27:26
SPEAKER_01: That'd be pretty fun.
27:27
SPEAKER_00: I'm not sure if you're joking right now because I'm being 100% serious.
27:30
SPEAKER_00: No, I'm not really joking.
27:32
SPEAKER_01: Actually, as we're just putting this script together, I thought, ah, you know, there's there's a really good opportunity here.
27:36
SPEAKER_01: I know a couple good volcanologists that we could easily collaborate on something super interesting, a super interesting project like this.
27:41
SPEAKER_01: That'd be awesome.
27:42
SPEAKER_00: And then you'll make your little partner feel a lot better about himself.
27:45
SPEAKER_01: There we go.
27:46
SPEAKER_01: Maybe Chris can come along on the trip and we can do a big field trip, it'll be awesome.
27:50
SPEAKER_00: Yeah, right now.
27:51
SPEAKER_00: Chris can relax.
27:52
SPEAKER_00: It's a plan.
27:53
SPEAKER_01: Just decrease the stress in Chris's life.
27:55
SPEAKER_00: I'm gonna push this.
27:56
SPEAKER_01: All right, there we go.
27:57
SPEAKER_01: Hey, as we wrap up here, just a reminder, you can go to geo.campcourses.com.
28:02
SPEAKER_01: There you can learn all of the basics of geoscience in our Camp Geo product.
28:06
SPEAKER_01: You can also look at Yellowstone and learn about the wonderful, amazing, spectacular geological story of Yellowstone National Park.
28:13
SPEAKER_01: Whether you're going there or not, it's valuable.
28:16
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28:18
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28:21
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28:24
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28:25
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28:29
SPEAKER_01: Cheers.
28:29
SPEAKER_01: Take care.