Dr. Jesse Reimink: [00:00:00] Chris Bolhuis.

Chris Bolhuis: Hi, Jesse. How we doing? Or should I say Dr. Reimink?

Dr. Jesse Reimink: You should say Dr. Reimink, you definitely should say that.

Chris Bolhuis: I know. We should, we're gonna get doctory today.

Dr. Jesse Reimink: look at. what I got on.

Chris Bolhuis: Oh, look at you. You have on a Yellowstone shirt.

Dr. Jesse Reimink: got my Yellowstone shirt

Chris Bolhuis: How appropriate,

Dr. Jesse Reimink: You know when I got this.

Chris Bolhuis: um, when you came out and spent some time with me in my class?

Dr. Jesse Reimink: I did, Yeah, a couple years ago. This is when I got it. I'm, I'm rocking it. I didn't even think, uh, I just [00:00:30] grabbed it out of the closet this morning and then sat down to work on this. And as I was looking at the script, I thought, you know what? I'm wearing my Yellowstone shirt. It's a good day, man. It's a good day to talk about Yellowstone.

Chris Bolhuis: Every day is a good day to talk about Yellowstone, but today is some of my favorite stuff. I know I say that all the time, but this, this time I really mean it. You know? I really do.

Dr. Jesse Reimink: Chris. The. and for the listener, that's not just a, a recording We don't edit that in. We don't splice that into every episode, just verbatim. That's just Chris repeating the same thing every episode. So that's actually new audio. [00:01:00] Every episode he's saying the exact same thing.

Chris Bolhuis: is. I know, I know. But it is very exciting cuz today, doctor, we are gonna talk about Yellowstone's other volcanoes and then related to that, the fossil forests that are such a cool story regarding Yellowstone. so…

Dr. Jesse Reimink: I will say, Chris, that the fossil forest and the petrified wood and petrified forest you can see in Yellowstone are like, can't miss things. I mean, I didn't get to see 'em actually when we were there. Or did we, I think for some reason I missed [00:01:30] the, when I was visiting you with your class, for some reason I couldn't, uh, go on the hike or something to do maybe I came later after you guys had already seen that. Yeah. But so I, I had to miss that the last time I was in Yellowstone. And man, that was, that kind of hurt. it's a can't miss. And at the end of this episode, we talk about a few locations where you can see petrified wood.

Chris Bolhuis: So let's jump right into it, Jesse. give an overview of today's episode. We are gonna begin by talking about the Absarokas, and now I do want to, can I just disclaim this a minute here. I always pronounce it [00:02:00] Absarokas, but it's, It's often pronounced Absarokas. So there are slight variations on that. And we're gonna talk about what we know about 'em. And also equally important, and this is something you and I discussed in depth actually, is what we don't know about them. And so we're gonna talk about what they look like. And we're gonna talk about some interesting things that are like geologically that are found in the Absarokas, like radiating dikes, the massive accumulation thickness, this feature called reverse grading and lahars and things like that. We're [00:02:30] gonna talk about why Yellowstone has so many fossil forests and within them and within the sediments that are deposited by these volcanoes. We're gonna talk about the diversity of the flora and fauna, which is absolutely amazing and, and shocking actually. And then we'll wrap it up with places to see.

Dr. Jesse Reimink: Yeah, and I think Chris to kind of summarize that, these are Yellowstone's other volcanoes. You said that right away, and this is the really important point to drive home. We talk about Yellowstone as, you know, the [00:03:00] super volcano, the super big volcano that's kind of maybe active, or maybe inactive, uh, depending on what you're looking at. But, drives a lot of what's cool about Yellowstone and what we've talked about up until this point right now. We are talking about the other volcanoes, and so image number one is an overview of the rocks that are exposed there, and they're really these are old volcanoes. And so we're gonna go back in time, now think back to our 30,000 foot view, our balloon ride that we had in the first chapter, and now we're, we're kind of [00:03:30] getting closer to the present, but the hotspot and the mantle plume are not there yet. We have these other volcanoes and that's what we're talking about today. And, this is the rock record pre plume and pre supervolcano Yellowstone.

Chris Bolhuis: Image number one shows the top of Avalanche Peak, which is just stunning example of the breadth of these volcanoes and like you said, they're eroded remnants. One of my favorite places in the park, but we'll talk about that later on. Let's. Jesse jump [00:04:00] into, this is, again, my opinion on this. I, I think the best place to see these is coming in from the East Entrance Road, which is coming from Cody, Wyoming.

Dr. Jesse Reimink: So Chris, you know it makes some sense given where the Absarokas are, that the east entrance would be a good one, but what makes it better than the north entrance or the northeast entrance, in your opinion? Like, what do you see there? And we'll maybe get into this in the episode, but yeah. What's, what's unique about the east entrance?

Chris Bolhuis: I think go through the breadth of these mountains. I mean, [00:04:30] these things are, they're 165 miles in length and that's from like north to south. So they begin, yeah, they begin in Dubois, Wyoming, and they go all the way up to Livingston, Montana. When you come in from the East Entrance road, you drive the 60 miles worth of width of these mountains, so you get this like example of the whole breadth of them. To me, I just think it's absolutely beautiful. You get to see this kind of cross section of [00:05:00] them. Not to say that going up through Paradise Valley going from Gardner to Livingston, Montana, where, you're kind of cradled by the Absarokas on the East and the Gallatins on the west. It's. It's shockingly beautiful. It’s called Paradise Valley for a reason. It's just a different experience and so this is just my opinion. I think the best way to see 'em is through the East Entrance Road. Not to say going from Gardner to Livingston is beautiful in its own right. So, how about that?

Dr. Jesse Reimink: yeah, [00:05:30] I, I totally get that. I think, um, we also, in the East Entrance Road, you kind of pass right near one of these ancient volcanic centers. And so we're talking about these old volcanoes and the map, on image number three kind of shows the breadth of these, and we're gonna talk about this, but I just wanna point our attention to that? That this is a huge amount of volcanic rock and there were 12 volcanic centers. And on that east road entrance, you kind of pass very close to one. So you get to see some of the features we're going to discuss that relate to the volcanic centers [00:06:00] on that road in, because you're near one of the ancient volcanic centers there. and, and there were 12 of 'em. So that's kind of important to point out. And these were quite high mountains. Think of the modern day cascades. That's what we're visualizing - Mount St. Helens, Mount Shasta, any subduction zone related volcano with a beautiful postcard view of a volcano. That's what we're picturing in our head as these ancient volcanic centers.

Chris Bolhuis: I want to just add one thing. They are like the modern day cascades, but these are on steroids. These things rose about 10,000 feet [00:06:30] above the valley floor, not to be confused with 10,000 feet above sea level. These were massive features that just, they dominated the landscape. Like you said, 12 volcanic centers, what that means is there were 12 different geographic locations where eruptions tended to focus on. So we call 'em the volcanic centers that way. The other thing about the Absarokas, before we get into some of the weeds on this, is that this volcanic field was very active [00:07:00] in what we call the Eocene, which is 53 million to 43 million years ago.

Dr. Jesse Reimink: Oh, that's a great point. Yeah. To put some time on this, we're 53 to 43 million years ago. That's a great point. And Chris, this activity, I, It's hard to, again, overstate. The volume of volcanism that was happening here, and let's put this into context with some numbers. The volume of volcanic and also volcanically derived sedimentary rocks. So volcanic rocks is like ash and lava coming up onto the surface and crystallizing [00:07:30] forming a rock. But then we also have sedimentation that happens. Those rocks get broken up and they get deposited. Rivers carry them downstream, carry ash downstream deposited in what is actually a sedimentary rock, but it's actually sourcing volcanic material. So we kind of, when we think of the volume of stuff that came out of a volcano, we have to include those sedimentary rocks as well. But the total volume that's shown on image number three here, that purple field on the gif, is showing the aerial extent. The volume is massive. Over [00:08:00] 7,000 square miles of, of volcanic rocks was erupted through these 12 volcanic centers. And we compare that to the Yellowstone Supervolcano. it's way bigger. The Yellowstone supervolcanoes, like less than 1,100 cubic miles, and we're talking about five times bigger. Five times more material came out of the Absarokas in those 12 volcanic centers.

Chris Bolhuis: That's right. So these volcanoes deserve respect, and that's why I'm excited today. They get kind of overlooked because they're overshadowed by [00:08:30] the current active Yellowstone Supervolcano. But these volcanoes deserve respect. There are two broad kinds of rock in this kind of supergroup. And refer to them as a supergroup because it's this kind of like garbage canned term that is used to encompass all of the rocks that were deposited by these volcanoes. Which includes the volcanic rocks themselves and the sedimentary rocks that were deposited by streams and lahars and things like that.

Dr. Jesse Reimink: Let me jump in there real quick, Chris, and say, supergroup [00:09:00] is a way to divide up the rock record. So we talk about groups and supergroups, members, we have all sorts of terms that relate to the naming of rocks in a sequence of rocks vertically stacked, so from oldest to youngest. And supergroup is just a certain type of designation for a package of rocks that are all related to one another. So That's what you're referring to here. When we say supergroup, we're talking about the rocks from the Absarokas, and uh, you're right. Lava flows, breccia’s, all these sedimentary rocks that you just referred to, there's [00:09:30] a load of different stuff. And so if you're wandering around in Yellowstone, you're probably gonna see a bunch of these different rocks. They look quite different, even though they're all volcanically derived.

Chris Bolhuis: So you brought up a good point about the, the volcanic rocks themselves. These include lava flows and what we call volcanic breccia’s. A very. Awesome place to see an example of these is the Mount Washburn hike. It's moderately easy, it's six miles in length, and you're just walking through [00:10:00] these lava flows and what we call volcanic breccia’s, which is, where you have these flow kind of textures that has very angular, broken up, busted rocks within it. And we just geologically, we call that a breccia. These rocks dip about 30 degrees away from the volcanic centers. And so we get a rough idea of the slope of these ancient eroded volcanoes from that. The sedimentary rocks though…

Dr. Jesse Reimink: And Chris, let, let me, let me jump in here real quick and talk about these rock types cuz you know we have a lot of exp…

Chris Bolhuis: I was just hitting my jive there man.

Dr. Jesse Reimink: [00:10:30] I know, but, but I wanted, I gotta jump in here cuz they're so fun. And you and I I want to talk about just the variety of, of colors and shapes and stuff in these rocks. Cuz you and I, you know, we've obviously been in Yellowstone together looking at these rocks. You taught me Geology here in Yellowstone. Looking at these rocks and, we've been to Mount Saint Helen's together and looked at the modern equivalence of these things. I am always astonished by how, how varied these rock types are in one volcano. Like you kind of think of this textbook model volcano as like [00:11:00] ashfall, and it All looks the same. right. But they're so different. They're pinks and purples and lavenders and oranges and then these breccia’s with big clasts and stuff. So I don't know, what are your thoughts on this? How do you, what are your favorite ones? What are the most beautiful ones? The Absarokas. I just, I don't wanna move past it cuz it, it always astonishes me how varied they are. I don't know. What do you think?

Chris Bolhuis: Okay. Uh, I'm not gonna give you my favorite. I'm gonna what I'm gonna say is that, You know, I think this is such a good point. We've touched on this many times actually in our own [00:11:30] personal discussions. That volcanoes, we try to put 'em in a box and try to say, well, this is what happens, right? In reality, volcanoes snowflakes, and, and they have, you know, within even one volcano itself, you can get a tremendous diversity in what comes out of it because the path that the magma has to take to the surface is not a uniform path. The way that it traverses the crust to come up and out can be diverse and, its residency time is gonna [00:12:00] affect how much it assimilates and blends in from all the country rock and all this stuff. We talked about this with, our earlier episode on the supervolcano itself. I love the diversity of the rocks that they give, and it's such a good opportunity to show this to people that, you know, volcanoes are very difficult actually to pigeonhole and to put into a box and say, this is exactly what happened.

Dr. Jesse Reimink: Right, and And it's really hard to categorize the rocks. And I think, you know, one thing, we're not talking a lot about the rocks here in this Yellowstone, book. [00:12:30] And in part because it's so complicated. There's all sorts of stuff and they all relate to another. It's kind of, if you understand the main theme, rocks are coming out of volcanoes and then they're being moved around. That's enough to really get all of the geological awe that you can when you're on, you know, Mount Washburn hike or Avalanche Peak hike. Like just look around while you're hiking and notice the variation cuz it's really cool.

Chris Bolhuis: To wrap up the kinds of rocks that we get in this supergroup, then we talked about the volcanic rocks. Then you

also get the sedimentary rocks that was [00:13:00] this volcanically derived stuff that was transported away from the volcanic centers by rivers and streams and things like this. And so we're talking about conglomerates, which has rounded clasts and particles in it. Sedimentary breccia’s now, which has lesser transport and more angular pieces and clasts. We have sandstones and siltstones and things like this. And, these were often lahar deposits. And that, that's l a h a r, that's how that's spelled. And this is [00:13:30] just a, a volcanic mudflow, which we're gonna talk more about here coming up.

Dr. Jesse Reimink: The other thing about these volcanoes is we know if you're hiking around or you just go up to one of the peaks and you look around and you say, how the heck do you know where these ancient volcanic centers were? The reason we know this is because there are radiating dikes, and this is a really common feature in volcanic centers, is that when you have a, a sort of a, volcano, think of the center of that volcano. It's not just a single tube of magma going up underneath of that, there's [00:14:00] magma being fed from the sides into that plumbing system as well. And those sides will cool and crystallize and form what we call dikes, which are igneous rocks that are cross-cutting other rocks. And so you can see these radiating dikes again, Chris, on your east, entrance trip. The Chinese wall, I think right, is one of the better ones to stop at.

Chris Bolhuis: Let me come back to that a second because you asked me why the East Entrance Road. Well, here's another reason why, because you can see these things, these radiating dikes are very, [00:14:30] very obvious when you leave Cody and you start to climb into the Absarokas, for sure.

Dr. Jesse Reimink: That's the key indication that you're near a volcanic center. One of these ancient volcanic centers. These 53 to 43 million year old Absaroka volcanic centers, think of it as spokes on a wheel. They all point towards the center. You can map these out. Geologists, go around, map these things out. They point towards the center, towards where there used to be an ancient volcano there. So Chris, this Chinese wall thing, do you guys stop there on the trip you know, when we were going through, when we were on the trip, you would always be on the [00:15:00] radio, on the CB radio. You know, you'd be lecturing away while we're like hauling down the highway and all of us in the back are like, oh, Mr. Bolhuis is on the radio again. What do you, what do you think? Do you guys stop there or do you just hit it with the radio on the way past?

Chris Bolhuis: You know, I'm a little offended first of all, that you, you rolled your eyes when you said, oh, Mr. Bolhuis is on the radio again. Here we go.

Dr. Jesse Reimink: Hey, I was, I was 17. I roll my eyes only slightly less these days to you so,...

Chris Bolhuis: Okay. Well first of all, the Chinese wall is this dike that you described. It's one of the spokes of [00:15:30] the wheel, right? And it's two miles west of Wapiti. This is not to be confused with the much more famous Chinese wall that's in Northwest Montana. But it is just a glaring example of one of these. It's a plumbing network that fed the volcanic center. This is what diverted the, magma from deep down and it, it brought it to the surface through these radiating dikes. There's another cool feature.

Dr. Jesse Reimink: Well, hold on. Do you, hold on, Chris, do you stop

Chris Bolhuis: Oh yeah. I didn't answer the question.

Dr. Jesse Reimink: Yeah,

Chris Bolhuis: alright. You're right. I got too [00:16:00] excited and went into the meat.

Dr. Jesse Reimink: I know, I know. You're, you're, I know you're, you're putting yourself there right now. You're like visualizing it and you’re excited to get back out there.

Chris Bolhuis: I am, we don't actually do this on the trip anymore because we don't come in from Cody anymore. We used to when you were on the trip. Um, but now we take a different route because when we leave Yellowstone, we go up to Glacier National Park and so it makes sense to do the Tetons first come up the South Entrance Road from Jackson. And so we don't actually do this route anymore and that's disappointing. We still [00:16:30] come out this direction, but not this far. Another really cool feature, these are called Hoodoos, And this refers back to image number four in your stack. I'm a huge fan of hoodoos. You. You see these like geologically, these refer to kind of vertical spires that jut out. Sometimes they're called needles, but the technical term is that they're, they're called hoodoos. And here these are sedimentary rocks that have been eroded into these just really narrow spires. The one that I always refer to [00:17:00] when I take this road is what's called goose rock, cuz it looks just like a goose's head. It, I mean like you can't miss it. And it is eight miles west of Wapiti. So it's a little bit on than the Chinese wall. So Chinese wall is two miles west of Wapiti. This is eight miles west of Wapiti.

Dr. Jesse Reimink: So I think, Chris, let's move into talking about some of the more detailed history of, of these volcanoes and what they tell us about the world at that time - 43 to 53 million years ago. It's a really [00:17:30] interesting story. One interesting phenomenon is that these lahar flows, so these are like volcanic mud flows, volcanic mudslide, mud flows, think a lot of ash is deposited, and then a bunch of rain or glacial meltwater and these things just flow very, not super fast, but very violently down slope. So lahars are like these unstoppable, thick, gooey mud flows that are very, very large volumes. And so, normally if we have a flood deposit, like a water-based flood [00:18:00] deposit, what we do in Geology is we often see what's called graded bedding, where the high energy flood. Drops off big grains first, and then as the flood slows down, the water energy subsides and the size of sediment that that water's carrying gets smaller and smaller and smaller. So you'll see what's called a graded bed where we have course grain on the bottom, then medium, then fine, then very fine. As we work bottom to top, oldest to youngest within that, that flood deposit. These are a bit different though because this stuff is so thick and gooey and [00:18:30] sticky. What we call viscous is that the big particles, these heavy particles floated on top. They kind of got pushed up to the top of the flow. So we have what's called reverse graded bedding here, reverse grading in these lahar flows. And sometimes you can get a really tiny fine clay layer that sits right on top. And what that is, is as the flow, the weight of the flow kind of settled, the water oozed up on top and think of like drying concrete. When you pour a big concrete thing, that water kind of oozes up on the top and makes a [00:19:00] nice skim coat on the surface. That's exactly what this is. Basically, is a, a fine clay layer right on top. A cross section through a lahar deposit. It's a really interesting phenomenon and kind of unique in geology.

Chris Bolhuis: That's right. I want to interrupt you a second. I want to talk a little bit about these lahars if I can, because these volcanoes behaved much like the modern day Cascades. When they erupt, they tend to erupt very violently. It's on the order of hundreds of years-ish, maybe 200 to 500 years in between eruptions here. But the amount of ash that came [00:19:30] out from these massive eruptions - It filled the valleys, and so the streams had nowhere to go. They were filled with this like loose unconsolidated ash, and the water then just accumulates and it accumulates and it accumulates, and then, Gravity wins out and the weight of the water just punches through this soft ash and it begins then that's the beginning of this, this kind of volcanic mud flow, right? And it's ripping up it's got a lot of water, it's got a lot of material, and so they're just very, very powerful [00:20:00] events and they come down the valleys and kind of sprawl out in all kinds of directions, and they're just anything that's in their way; boulders, massive rocks and trees. Anything that's in its way is gonna be ripped up by these lahars. Absolutely. And carried down away from the volcanoes until it loses energy and begins the deposition process.

Dr. Jesse Reimink: In our camp geo course structure, Chris, when we talk about volcanoes, we show a couple of hazard maps

that people have made around the modern cascades and many [00:20:30] of the most, important hazards to map out are lahar flows. Like where those lahars are gonna happen is a really important thing to nail down cuz you wanna know like, which neighborhoods might have to evacuate for a lahar. Which ones might have to evacuate for an ashfall. Like these are very different hazards when we think of modern society. And so that kind of brings us back to this Cascades thing. This modern Cascades analogy. They, like you said, erupted like every couple hundred years very violently. And then like the Cascades, they probably had some oozing out and some, you know, intermediate volcanic [00:21:00] eruptions. But the formation of these is not really well understood. Like back up and say, why are there volcanoes here? It's not necessarily clearly understood why this is, they're in the age of the Laramide orogeny. So they had something to do with, the tectonic activity and the complicated tectonic activity that took place in the Laramide. But the actual formation of the Absarokas is not entirely clear. The, the magma source, like was it subduction zone volcanism? But it's really far inboard from subduction zone. Was it extension? Well, we had the Laramide [00:21:30] Orogeny going on and there wasn't a ton of extension in the region. So how do you get volcanoes in this area? Is… There's a bunch of viable options, I would say. It's not like there's no good options. We don't know how to explain it. I would say there's a bunch of decent options. We just don't know which one was actually going on.

Chris Bolhuis: But what we do know, we can transition into this now, is

Dr. Jesse Reimink: Uh, hold on. Chris, this is a cool, I wa just wanna say this is a cool story. This is such a cool story. I'm

excited to talk about It. This is such a cool story. Petrified wood!

Chris Bolhuis: I, I agree.

Dr. Jesse Reimink: Let's do it.

Chris Bolhuis: It's these sedimentary rocks [00:22:00] in the volcanic supergroup that give us this window into what was the climate like? Well, these sedimentary rocks, they have the flora. They have the fauna, and they tell us then about the climate that existed in the Eocene period between 53 and 43 million years ago. So here's what we have in Yellowstone. Beautifully preserved petrified wood. It's amazing how well this stuff is preserved. Look, inside [00:22:30] Yellowstone National Park, there are 27 Fossil forests of petrified wood buried one on top of another. So go back to the lahar, right? You have these volcanoes that erupted every 200 to 500 years ago. So these volcanoes, they would create these lahars, they would rip up the trees and carry 'em down into the valleys below, and then everything would just kind of slow and settle, right? And then 200 to 500 ish years go by - a new forest populates the top of [00:23:00] this old lahar and the flanks of the volcanoes and the volcano repeats itself. If you refer to image number five in your stack, you can see a great example of this where each of these colored layers. We, you know, we have a yellow layer and a gray layer, and an orange layer and so on. of those colors represents an event, a lahar event. And then, you know, the volcano goes dormant for a period of time. Hundreds of years go by. It gives it adequate time for another mature forest to [00:23:30] establish itself and the cycle repeats itself and so you just get 'em successive layers, one on top of another and, that 27 of them in Yellowstone. It's amazing.

Dr. Jesse Reimink: And, and Chris, this is, it's such a valuable thing because not only is it really cool, the volcanoes erupting, you know, volcanic rocks, lahars, capturing these trees. It's really an amazing preservational tool. So the reason that this is super interesting is because it gives us a window into what kind of trees and [00:24:00] plants were around 40 to 50 million years ago. There are over 200 different types of plants preserved in various, you know, types in needles, cones, pollen, trees, petrified stumps. There's all sorts of stuff. And the main summary point is that the climate was a lot different 40 to 50 million years ago. A lot different here. It was a lot warmer and a lot wetter. We have a lot of trees, flora, that is representative that grows in subtropical climates, so things like magnolia [00:24:30] trees, Cyprus, dog woods, breadfruit, avocado, these crazy trees that you don't find in Yellowstone National Park today, you find 40 to 50 million years ago. In these basically time capsules that are captured by these volcanoes.

Chris Bolhuis: A couple things I want to add to what you said is not only do we have these subtropical flora, but we also have examples of cooler climate trees such as spruce, pine, hemlocks, and larch. And there's this very, very neat story [00:25:00] that kind of ties these two things together. How do you get these trees that grew at the same time, but they grow in very different climates? That's a part of this geologic story, but I wanna say this, that this has been well established in terms of the climate during the Eocene time, but it's not because of tectonics. It's not as if Yellowstone had moved from the subtropics to where it is now, because the climate right now in Yellowstone is, is nothing like the flora and fauna that we see preserved in [00:25:30] these age rocks.

Dr. Jesse Reimink: It ain't subtropical there uh, definitely not.

Chris Bolhuis: no. Yeah.

Dr. Jesse Reimink: Go there in June and you’ll recognize this.

Chris Bolhuis: They have like, seriously about 30 frost free days a year in Yellowstone National Park. So very, very different

climate. So let's get into the logs, Jessie.

Dr. Jesse Reimink: yeah. This is a really cool story, right. there's a couple of really interesting parts to this, but we're gonna be talking about petrified forest. We're gonna be talking about the different types of trees you just laid out, subtropical, and then sort of [00:26:00] cooler climates, the spruces, the pines, the hemlocks, the things we kind of affiliate with a little bit cooler climate. There's that. We're gonna talk about the tree species and we're gonna talk about the stump orientation as it's petrified Is it upright or on its side? Right Chris? And, uh, break those apart for us a little bit.

Chris Bolhuis: Okay. Refer to image number six, please. If you look at image number six, this is just what we saw from lahar deposits of Mount St. Helens. These floods would rip down the valleys and they would just [00:26:30] snap massive trees off at their base and carry them as these horizontal logs down the valley until the lahar slowed and came to rest. Right? And so these, these. Massive trees were all lined up like toothpicks all in the same direction. We see that in

Yellowstone National Park in the petrified forests.

Dr. Jesse Reimink: Chris, let me interrupt real quick here cuz you just did a great job of restraining yourself cuz listener, Mount Saint Helens is the reason that Chris is a geologist and you did a [00:27:00] great job Chris. I just wanna say that you did a great job of both explaining that and also restraining yourself cuz you know, sometimes you get really excited talk about Mount Saint Helens

Chris Bolhuis: I I, don't know if I restraining myself is good, but I, I did, I'm, I'm working on it. Okay. It's a, it's a work in progress.

Dr. Jesse Reimink: Well, you said it clearly which is restraining yourself to me,

Chris Bolhuis: Okay. It's a, work in progress. But let's talk about these stumps. So the horizontal stumps, the ones that are lined up like toothpicks, as you can see in image six, these tend to be the trees that [00:27:30] grew in cooler climates. The pines. The hemlocks. The spruces. Okay. What we also see in these lahar deposits are vertical stumps with roots and rootlets and so on. But these trees are very different. The vast majority of the ones that are vertical - not lined up pointed like toothpicks. These are the ones that are magnolias and cypresses and things that grow in subtropical, warm, wet [00:28:00] climates. That's what we see in these lahars, and I'm gonna tell you this is one of my favorite things to talk about when I have students out there is, alright, here's the evidence, here's what we see. Make it make sense please.

Dr. Jesse Reimink: What's going on? And Chris, I'm not gonna interrupt you. I want you to explain it, but I just wanna highlight here that this is the beauty of Geology - is it just makes so much sense. But it's not entirely clear. Like right now, listener might be thinking. Okay, how do I piece these things together? But once Chris, you know, explains this, [00:28:30] it's beautiful. It is such a beautiful, intuitive science. I love Geology and this is a great one. So, okay, we've got knockdown trees are the cooler ones. Upright trees are the warmer ones. What's going on?

Chris Bolhuis: I wanna refer everyone to image number seven in our stack first, and I'm gonna keep on referring to this over the next minute or two as I talk about this. So the, trees that are lined up like toothpicks, colder climate trees, these are the ones that grew up. Remember what we said earlier, have 10,000 vertical [00:29:00] feet of relief. I mean, these are massive volcanoes, so you can be in a warm climate. But if you're up high enough in elevation, you don't have a warmer climate, you have a colder climate. So these trees that were snapped off and carried by these lahars - they grew high up on the volcano and were carried down by the lahar to lower elevations in the valleys. A big drop in, you know, elevation, where then as soon as it comes out into the valleys, the lahar [00:29:30] slows down. But what's growing in the valleys? It's a warmer climate, and this is the tropical trees, the cypresses and the magnolias. But the lahar was slowing down, so it lost its ability to snap off the trees, providing us then with vertical stumps. And that's the story.

Dr. Jesse Reimink: It's such a cool story, such a cool story. and Chris, it's such a amazing story because the trees that are knocked down are. Got hit by higher energy Lahars, right? They're closer, they're closer to volcanic center. They're higher [00:30:00] up, they're different style of tree, different species of tree. and this also represents in the numbers, Chris, like people have mapped this out, have looked at fossil forests, looked at the proportion of trees knocked down versus upright. And when we're close to these volcanic centers, we have a lot more knocked down trees, 72%. Of the trees are knocked down and only a third of them are left upright. When we're farther away, we have basically the inverse, more like 70% are upright and 30% are knocked down. And as we talked about, the species of tree, the average [00:30:30] species of tree changes as well. It's just such a beautiful story that you can look at these fossil forests across the area. And let's look at image number eight, which is one of these upright petrified trees that you can see. They're really just stunning when you're walking around looking at these things. You, if you go for a hike in Yellowstone, you'll probably be able to find and see petrified wood in these fossil forests. First thing is leave it be, never take it, always leave it there. But the second thing is. [00:31:00] appreciate the geological story that these things tell cuz it is really just spectacular and it's a spectacular bit of history that these things tell. It's so cool.

Chris Bolhuis: it is Jesse, image number eight. We're looking at a redwood. Okay. The, the kinds of redwoods you get to see in California, you know, but, here we are in Yellowstone National Park, which is a vastly different climate than where we find redwoods today. And you know, understanding that how that happened and the fact that we're looking at a tree that represents a climate that is so different than what we have today. That's just the [00:31:30] process of scientific discovery. Amazing. I love it.

Dr. Jesse Reimink: I agree. And Chris, I think this makes me think of a quote from one of our favorite geologists, I think who we interviewed for our podcast, Martha Gilmore. Marty Gilmore. She said that Geology's great because when you look at the rock record, you're looking at a world that does not exist anymore. And that is exactly what we're seeing here. When you walk around and see these things, you are seeing a planet that does not exist anymore. It did exist 40 to 50 million years ago. These types of stories give me a lot [00:32:00] of, uh, appreciation for how amazing Geology is really. So Chris, before we kind of wrap up the episode here, how about will you just tell us where your favorite spots to see petrified forests are? And in image number nine, really kind of has a few of these labeled there and, shows you a few of these, but I dunno, from your personal experience, What are your favorites?

Chris Bolhuis: I'm gonna do this in two ways actually. I'm gonna first tell you where my favorite place to see the Absaroka

Volcanoes, these ancient eroded volcanoes are, or these kinds of rocks. and so my [00:32:30] favorite, favorite, favorite place is Avalanche Peak. It's on the East Entrance Road. It's near Sylvan Pass. It's my, that place is warm and dear to my heart. It's a strenuous hike though. It's a five mile ish hike and it is difficult. But it's so worth it. Another more accessible place is Lake Butte overlook- also on the East Entrance Road. There are no buses or RVs that are allowed up there cuz the parking lot is small. But cars and so on are, allowed. It's like a mile off the main road [00:33:00] up a hill. And it's beautiful cuz you're, right near the edge of the caldera right there, and you're still in the Absarokas. It's that the, the part that did not get bitten out. when you sit on the edge of that, you're dangling your legs over the rim of the caldera. And that's pretty special place, you know, of course. Mount Washburn, I already talked about that. It's a great place to see these kinds of rocks too. And then Paradise Valley driving from Gardner to Livingston is, it's called Paradise Valley for a reason. it's pretty amazing[00:33:30]

Dr. Jesse Reimink: and those are three locations to see both the Absarokas and Petrified Forest

Chris Bolhuis: yes.

Dr. Jesse Reimink: what are the next, uh, the other couple?

Chris Bolhuis: the petrified wood itself, can be seen. This is, special. First of all, You can see it easily with just a short walk from a parking lot by going to see, what's called the Petrified Tree on Petrified Tree Road. This is just west of the Tower - Roosevelt Junction. Just a, a very short walk and it, it's a huge redwood that's - They put a fence around it because people take it. And again, I wanna reiterate what you said. Don't ever [00:34:00] take anything from Yellowstone National Park or any National Park. But then another one, you're like me and you gotta get up and you gotta go walk, Petrified Forest Trail or Specimen Ridge, this is 2.8 miles - or 3.6 if you take a side trip up to the top of Specimen Ridge. It's an out and back, moderately strenuous. It's not like clearly marked, if you will. It's fossil forest trailhead, and it's on the Northeast Entrance Road. Jesse, highly [00:34:30] recommended. I love this. I, I just, um, good recommendation, I think, is to go see that. And so you can see, if you look at image number nine again, kind of what we've been talking about with Specimen Ridge and Paradise Valley and Petrified Tree Road, avalanche Peak is on there and Lake Butte overlook. So those are all highlighted on this kind of gifified image, just for reference. All right. Before we do the FAQ at the end of our episode, which is the way we're ending these, just give us [00:35:00] a brief rundown of what we've done.

Dr. Jesse Reimink: Quick and dirty summary here. We talked about the Absarokas, Yellowstones other volcanoes. These were massive. They had a lot of volcanic activity. There's all sorts of very interesting rocks you can see here. We talked about radiating dikes. We talked about sort of how they might have formed potentially, and then. One of the really cool things about these is they served as these little time capsules. They encapsulated and made fossil forests, which give us an insight into what the place looked like, the flora that existed, what the climate was like in [00:35:30] this Yellowstone National Park area, 40 to 50 million years ago. And we kind of walked through that story. So, what’s our FAQ today, Chris?

Chris Bolhuis: The FAQ today is, What does petrified wood mean? What does petrification…

Dr. Jesse Reimink: Uh, yes, good one. The

Chris Bolhuis: field it or do you want me to go?

Dr. Jesse Reimink: I I'll, how about this, I'll take a crack at it, and then you, uh, you fill it in. So this is a common, I wouldn't say if it's maybe like a misconception, but maybe something that people have a lot of questions about. Typically, like what is petrified wood petrified wood [00:36:00] technically is wood that's become a rock. I think many people kind of understand that. But the way to envision the way this happens is we've talked about these lahars, these ash flow deposits that knock down a tree. That ashfall is really fine grain particles and it's really readily dissolved. And the silica is one thing that's really readily dissolved. When it's really fine grained in kind of powder form, it's really easy to kind of dissolve it and move it around with a little bit of acidic rain. And when it starts to move around, [00:36:30] it can flow through the trees. The trees will still kind of take up that water. It's a porous material, the wood, and so it takes up that silica rich water and that silica will then precipitate in and around the tree structure. And so petrification is a fairly complicated process. That means you're taking the structure and you're making a kind of a rock out of it. You're rockifying this biological structure and there are spectacular examples of this where it's mostly silica in there and the color variations are trace, uh, amounts of other [00:37:00] elements in there, but it's a lot of silica basically turning it into quartz or variations of silica and oxygen in the petrification process. But Chris, there's also actual wood preserved in some of these areas too. Like not all the wood is petrified. We do have actual wood fragments, like organic wood fragments, right. Yeah.

Chris Bolhuis: That's right. So you think of like these wood fibers as little tiny, pencil shaped, cylinders. Right? And the silica is on the inside of the cylinder, and the wood is still around [00:37:30] that. And so if we dissolve away the, the minerals that are deposited inside, we can test the, the DNA if you will, of the, of the treat. You know, and find out exactly what species these things are. So there is still some wood that can be preserved in this really, really old stuff.

Dr. Jesse Reimink: You know, Chris, it brings to mind, uh, that there are other volcanic eruptions in this same time interval. Actually, these kimberlite pipes that erupted up in northern Canada around the same interval, 55 to 65 million years ago. When these things erupted, trees would fall back down in and they kind of [00:38:00] contain the same record of a warmer earth. Uh, these trees would fall in, they'd be buried by a whole bunch of ash on top, and then they're sort of really well preserved and not even petrified a little bit. And so they're, they're actually wood. You can find them right now. And it's actually, there's no silicification cuz there's no fluid flowing around in there. They're actually wood. You can light 'em on fire. It's 40 million year old wood that you can light on fire. I don't think that's preserved in Yellowstone, but the, the point that this organic structure can still be preserved during electrification is [00:38:30] a, a really a cool thing. And I just love petrified wood. I think it's so cool. It is just such a cool story.

Chris Bolhuis: It's amazing.

Dr. Jesse Reimink: Yeah.

Cool. Hey man, that's a wrap. Good stuff.

Chris Bolhuis: All right. Cheers.