Dr. Jesse Reimink: [00:00:00] Chris, what's up dude?

Chris Bolhuis: How you doing, Dr. Reimink?

Dr. Jesse Reimink: Oh, I'm great. I think you are. I can see the vein a little bit coming out in the forehead over there. You're pretty excited for this episode, I think.

Chris Bolhuis: I am. Yeah. I'm always excited to talk about Yellowstone. I love Yellowstone.

Dr. Jesse Reimink: In particular hydrothermal features. This is like, I don't know. I'm, I'm, I'm gonna speak for you cuz I like to speak for you, especially when you're not around. But this is I think one of your [00:00:30] more. This is one of your most favorite parts about Yellowstone. I think you, I remember when you were teaching me Geology when I was in high school and we, we went on this field trip that you've led for like 25 years out to Yellowstone. You just get so fired up. It's great. Like whenever you're doing the little schematics or you're doing the, the demonstration on the boardwalk, uh, you, you just came with such intensity to talking about the hydrothermal features. It's so cool. So, uh, this is gonna be a fun chapter to dive into.

Chris Bolhuis: You know, this is what defines Yellowstone for most people - is it's all things. It's all about the hot springs. It's all about [00:01:00] the geysers and mud volcanoes, and this is, one of the main reasons why people go to Yellowstone is for this, and, I think it's natural to be excited about it.

Dr. Jesse Reimink: It's what makes Yellowstone great. If you're listening to this and you're planning on going to Yellowstone, or you want to go to Yellowstone, or you're on the way to Yellowstone, or you're in Yellowstone, you're there probably in large part because of the hydrothermal features. And so Chris, this, is gonna be just an overview. I just wanna highlight that out front. This is an overview of hydrothermal features, and we're gonna talk about specific ones later on [00:01:30] in different chapters. So we'll have a chapter on Old Faithful, on Grand Prismatic Spring. This is not that. This is a high level overview of hydrothermal features.

Chris Bolhuis: Today what we're gonna talk about are geysers, hot springs, mud pots or mud volcanoes and fumaroles.

Yellowstone has all of these hydrothermal features. Hydro means water, thermal means hot, and last chapter we talked about the hotspot of Yellowstone. And that hotspot drives everything that we're gonna talk about [00:02:00] today. Because Yellowstone has over 10,000 hydrothermal features and it has over half of the world's geysers.

Dr. Jesse Reimink: It's an absolutely incredible number. I mean, half of the world's geysers are crazy. And Chris, before we just move on, I wanna paint that. Picture again, we talked about the deep earth. We talked about magma, plumbing systems down in the earth and, and really the super volcano we're zooming in now to the upper part, so imagine that schematic of a continental crust. We had this mantle plume really, really deep-seated at the core mantle boundary. We started to [00:02:30] zoom in on Yellowstone, the hotspot track. Now we're zooming in on the upper couple kilometers at most of the crust. We're really talking about the interaction between the water and heat, which comes from the magma, which came from the mantle plume. So that's the kind of connection, bringing it back to what was going on in deep Earth. But we're zooming in on this upper, upper lens here now.

Chris Bolhuis: That's a great segue to talk about then what does this upper thing look like? Last chapter, we painted a picture. We had some images and gifs of [00:03:00] what the magma chamber that is just below the surface, you know, three to five miles below the surface. So let's look at this. We have this sponge-like magma chamber - mostly solid under Yellowstone National Park. It's three to five miles down below the surface, and this is the heat engine. That drives the hydrothermal activity. Right on top of this, we have what's called a brine, and this is very hot, salty water,[00:03:30] and it's over 400 degrees Fahrenheit at this depth. And we're talking about like from 1.5 to three miles below the surface. You might think, right, Jesse, I want you to explain this a second for everybody. How can you have water? If water boils and Yellowstone about at 197 degrees Fahrenheit? How can we have water at depth that's over 400 degrees? What's going on with that?

Dr. Jesse Reimink: Yeah, it's just the pressure and, you know, the pressure of the overlying rocks, the overlying earth is compressing [00:04:00] that stuff. And as we talked about briefly before, when we have high pressure, basically stuff wants to be a liquid, not a gas stuff wants to be a solid, not a liquid. So high pressure compresses stuff into the more dense, form - which is liquid in this case. And Chris, image here to think about this, brine, is I think some people have seen these videos of, uh, what are called black smokers. These big hydrothermal vents down in the sea floor that are pumping out really, really hot, really crazy composition brine. That's exactly what this type of stuff is. It's really [00:04:30] stuff that came out of the magma system and also there's a little bit of groundwater mixed in there too, but it's kind of this weird amalgam somewhere between magma and water. Like we think of it. Brine is the word we use for that.

Chris Bolhuis: So we have this sponge-like magma chamber that heats this dense, salty, super hot brine that is circulating. It's convecting. It gets super hot, it rises up, cools off a little bit. So you get these circular motions within this brine, and it's that brine deep down that [00:05:00] is heating the fresh groundwater above it. So you think of it as three layers. We have this sponge-like magma chamber. We have this very hot, salty circulating brine, and that brine is transferring heat to the fresh groundwater on top of it. And the fresh groundwater sits on top because it's less dense. It's less dense than the salty water, and it's this fresh water that comes out at geysers, hot Springs, fumaroles. This is the fresh water that we're talking about that's [00:05:30] driving all the beauty inside Yellowstone National Park, and especially inside the Caldera.

Dr. Jesse Reimink: So Chris, I'm gonna make one more point, and then I'm gonna throw a question your way. So the first thing is that, think of this fresh water. This is circulating, this stuff circulates through. And so water, cold water will come down, it'll interact, it'll hit that hot area, you know, heated up by the brine. It'll get hot, which makes it less dense. Then it rises back up to the surface and eventually comes out in these geysers and fumaroles and hot springs. And so, think of these like big [00:06:00] circulation cells, cold water sinks, hot water rises, much like air does. It's happening at this scale in the first sort of upper kilometer or two of the crust. But Chris, this is a common question and I'd be curious to know if you know your students ever arrive at this question while you're out on the trip or if the random passersby that, that kind of tag along. Whenever you're giving a lecture on a boardwalk, you always get the random strangers who kind of just migrate along with your class. If anybody asks this question, cuz I, I think it's might be a common one. What is the age of [00:06:30] the water in this? Like, how long is this water taking? How old is it? How long has it been since it came down as rain or snow? Do you get that question

Chris Bolhuis: Oh, okay. Yeah, that's a good question. I don't get it commonly, but I do have an answer for you. So listen, this water, this is a long winding journey. So it falls as rain or snow. It has to percolate then down as much as, you know, 12,000 feet to get heated by this brine down there. And then it's gotta flow into the geysers, into the [00:07:00] plumbing network beneath these things, and we're able to determine when this fell as rain or snow by looking at one of the isotopes that's in the water, the H2O molecule. It's tritium, which is heavy hydrogen. It's hydrogen that has a couple of extra neutrons on it and so on. Anyway, the thing is, is that it's radioactive, and, you know this, I mean, this is your field. Anything that is radioactive decays, it spontaneously decays, but it decays at a constant rate, and it's called the half-life. Bottom line is this, let me [00:07:30] simplify this, is that rain and snow have a fair amount of tritium in it. But the water that comes out of hot springs and geyser's inside Yellowstone National Park has very little tritium in it. And so by looking at the half-life, we know that this fell as rain or snow about 500 years ago. That's crazy. Crazy in an awesome way. I mean, it is pretty cool stuff.

Dr. Jesse Reimink: It's really cool stuff, really. And that's something I think that is for me is really, uh, it's just something I love [00:08:00] to think about when you're looking at these features - is think about how old that water is, because this is unlike much of geologic time. 500 years is something we can wrap our head around. And think about what was going on 500 years ago in the world and that's when this rain or snow was, was falling that we're eventually seeing coming out to the surface. Just a totally cool thing, to think about here. So, Chris, the way we're gonna work through this chapter is you laid it out before, but I just wanna highlight it again. We're gonna talk about Hot Springs and Geysers First, in that order. Hot Springs, then geysers, then Mud Pots, and then Fumaroles. And in [00:08:30] general, we're going in order from most water in the system to least water in the system. So Hot Springs and Geysers kind of have the same sort of amount of water in the system. There's some slight differences that we're gonna tease apart here, but we're gonna work from a lot of water in the feature to very little water in the feature. And that's the order we're gonna work through here. So hot springs, where do we start?

Chris Bolhuis: Where do we start with this? All right, well first of all, hot springs geologically in and of themselves, they are not that uncommon. It's [00:09:00] actually a fairly common geologic feature. And now we wanna point you to image number one in our stack. You get going with this. This is an image of the plumbing network that feeds hot springs at the surface. Keep in mind that this is just a schematic. This is an idealized diagram, but there are many different avenues. Think of it as like a plumbing pipe system below the surface that feeds this pool that you have at the top. That's really how you get a hot [00:09:30] spring. And, and again, the heat engine of this is that layered system of the magma, the brine, and then the fresh water. And that's what we're mainly showing here, is that fresh water near the surface of the plumbing network.

Dr. Jesse Reimink: and Chris, I think they're very common, like you said. I mean, they're hot springs all over the place. Some people probably have gone and sat in hot springs, you know, in various places you can go. Where was it that we went? Was it Colorado Springs that we went and sat in Hot Springs that one time?

Chris Bolhuis: No, it was not. This was by the Collegiate Peaks in southwest Colorado, near Buena Vista.

Dr. Jesse Reimink: Oh, that's right. Yeah, yeah, yeah. We [00:10:00] went to a, a little, uh, hot spring spa after a long week of camping and, and collecting rocks. That was totally, it was very refreshing. It was very nice. And, and, but these things are all over the point is that these are very common and they're not very complicated features. To form hot springs, you need four discreet things. You need to have a heat source. That's pretty obvious. It's, it's in the name hot Spring. So you need to have heat. Again, this is groundwater that goes down and touches this brine. There's various ways to get heat. It doesn't always need to be a magma system with [00:10:30] brine in the earth, but you need heat. You need abundant water. Again, hot spring, there's water involved, so we need water, usually rain or snow, melting, something circulating down, getting heated up and brought back to the surface. You also need porous and or permeable rock, which means the rock can have water passing through it. And that can either be percolating through the rock, like a sandstone has a lot of porous space and permeability space. Or it could be a highly fractured rock, which has a bunch of cracks in it that water can traverse through. So [00:11:00] porous and permeable rock. And you also, importantly, really importantly, and what sets them apart from geysers is that you don't have any restrictions or kinks in the plumbing system. And so you basically have this free path to the surface through a fault or a porous rock unit for hot water to rise up, buoyantly rise up and make its way to the surface. And then that can pond and form like a hot pool at the surface. And so Chris, I think before we move into geysers, we need to [00:11:30] talk about biology and this is something that we, we definitely have to hit. And it's unfortunate cuz your, father was a high school biology teacher. My father was a high school biology teacher. My sister is a high school biology teacher. So our family's, we have this like long running biology versus Geology, family battles I suppose. And so, we're gonna interject some biology cuz it's Yellowstone and it's totally cool biology. But it's the rare instance where it's worth noting, I think.

Chris Bolhuis: It absolutely is because what we're [00:12:00] getting at Jesse, is we're gonna talk about the colors of the hot springs. And if you look at image number two in your stack, this is the iconic hot spring. This is Grand Prismatic hot spring in midway Geyser basin. It is unbelievably huge. Grand Prismatic is a huge hot spring. It's one of the biggest on the planet and it's beautifully colored. And so we're gonna talk about a little bit anyway here, the colors and what's responsible for some of this. But I do want to say first [00:12:30] that when you talk about colors, it gets complicated really, really fast. Because this is a complex interaction between the temperature of the water, the water chemistry, such as what it has in it. Does it have iron in it? Does it have hydrogen sulfide in it? What's the pH of the water or the acidity of the water? All of these things interplay we're not gonna get that. That's beyond the scope of this kind of thing, what we have going on here. But there are some common things that are going on. This is just [00:13:00] a broad overview, but in the center of most of the hot springs, you have this beautiful aqua marine blue color, and…

Dr. Jesse Reimink: It is so beautiful. Uh, this Grand Prismatic, go there when you're planning your trip. You, you gotta go check it out. It is like the hot spring of all hot springs. It's so beautiful. And image number two captures it pretty well. Uh, obviously not like real life, but it captures it, you know, it does a pretty good job of talking about these colors. So on the left there, Chris, of that image is, is the blue you're talking about? Sorry.

Chris Bolhuis: That's right. And the reason for this, this [00:13:30] the blue color, first of all, the center of the hot spring in the center of the pool, it's usually too hot there and so organisms can't live in that water. And the blue color is the same reason why the sky is blue. Blue light - the wavelength of blue light is preferentially scattered. It gets scattered more than other colors, and it's randomly scattered to your eyes. It just has to do with the properties and the wavelengths of visible [00:14:00] light. And then the color that we see next to the blue is usually a beautiful ring of yellow. I mean, it's, it's stunning. And living in these waters, it's cooler here now. Living in these waters are organisms and they're called extremophiles, and this is a field of biology that is exploding and is continuing to do so. But basically these are organisms that thrive in extreme environments - high pH or low pH, high temperatures. They [00:14:30] can live in it and they actually thrive in it. Well, anyway, These organisms are so abundant in this color range, which is typically about 153 degrees to 167 degrees. They emit, they give off this bright yellow color. Outside of the yellow is a beautiful orange color. And you can see this in image two, this beautiful orange indicates, again, extremophiles, that give off this orange color. And the temperature of that water is [00:15:00] about 140 to 155 degrees. So we're seeing the colors often represent temperatures in the water.

Dr. Jesse Reimink: Yeah. And they're all slightly different. I mean, you won't always see this exact color pattern right. When you go to different hot springs. But I think one last thing that's worth noting, was that you touched on these extremophiles and one of the extremophiles is a bacteria that is called Thermus aquaticus, which was discovered in 1967. And this was really instrumental into basically our everyday [00:15:30] lives, even today. Is that this organism had this, this bacteria had a unique enzyme called taq polymerase and taq polymerase is famous because it is the polymerase in pcr - polymerase-chain-reactions, which basically is how we get to amplify DNA strands and do all sorts of dna. Quantification and DNA testing is using this pcr, which is a method that was discovered in 1985, won the Nobel Prize, and, you know, my family [00:16:00] actually uses, my biologist family uses what is called qPCR, which is,

Chris Bolhuis: Oh they do in their, yeah. That's cool. Bring this in. This is awesome.

Dr. Jesse Reimink: And, they use qPCR, which is quantitative polymerase chain reaction, which basically allows you to count the number of DNA particles in a sample. So they use this for like groundwater testing, to look for invasive species in groundwater, or in lake water or stream water. And so this PCRlike we can't say enough about how important PCR is to [00:16:30] our everyday society, right Chris?

Chris Bolhuis: We absolutely cannot. I mean, this has changed the field of forensics in terms of crime labs and so on, because you can take a tiny speck of, of blood or a speck of saliva or a tiny little strand of hair, and we can amplify the DNA in that sample. We can get as much as we need. So it has revolutionized that kind of field. And I think everybody walking out there has heard of PCR recently because PCR is that, you know, the, the famous [00:17:00] PCR test for Covid that we've been using, you know, for the last three years. So it's, it's a big deal. It's a very big deal. And I want to, I want to emphasize something. This came from a hot spring in Yellowstone National Park in the lower Geyser Basin. That's pretty cool.

Dr. Jesse Reimink: And, you know, I think, Chris, to summarize this - it just means that we've talked about how the Geology makes this really cool unique feature. So really Geology controls the biology. I just want to, you know, highlight that point as we move forward here. Uh, is that [00:17:30] Geology is the most important part.

Chris Bolhuis: Undoubtedly, there's no question. Yep, that's right. Geology always determines the biology.

Dr. Jesse Reimink: It does, it does, and mostly biology gets in the way of seeing the Geology, I think, but,

Chris Bolhuis: It does. It covers up our rocks.

Dr. Jesse Reimink: It covers 'em up, so, Is it a good time to move into geysers now?

Chris Bolhuis: All right. Let's talk geysers Jesse.

Dr. Jesse Reimink: Let's do it and you have a great analogy, which is summarized in the gif. That is figure three in your stack. And Chris, what I'd like is for you to just walk us through what is going on in that gif. Because the [00:18:00] GIF is based on an exercise you do every year when you're teaching this field course. You bring out your, you bring out your glass beakers and your hot plate, and you, you do it on the boardwalk. I think when I was there. I think you did it by Steamboat Geyser, maybe. I remember there's this huge like deck - platform, maybe not Steamboat, but as this big deck platform, we were all like sitting on the railing and there's people walking past and you've got this, apparatus that you're doing this exercise in and, and showing us how geysers really [00:18:30] work. And it's a beautiful analogy. So I kind of want you to walk us through that.

Chris Bolhuis: So the, the setup here in image number three, which is a GIF of what I do and what I show, it's a flask that we use in chemistry. It's filled with water. I have a black rubber stopper and I drilled a larger hole through the top of it, and then I put this long skinny glass tube in the stopper. But if you look closely at the bottom of it, it has a kink in it. It has a restriction in the bottom of [00:19:00] that glass tube. Now, this glass tube is about three feet, uh, three or four feet tall. Okay, so I need that. I need to, I need to have this long column. No,

Dr. Jesse Reimink: Yeah, you don’t miss it when you're walking past it on the boardwalk.

Chris Bolhuis: No, I've got a big glass rod sticking out of my backpack.

Dr. Jesse Reimink: Yeah. And 25 students piled around like, what's, you know, everybody's like, what's going on here?

Chris Bolhuis: What is going on here? So anyway, this is a beautiful simulation of how geysers work. In order for geysers, you have to have a kink. This is what [00:19:30] separates it from just being a regular old hot spring. Geysers don't have a free flow of water to the surface, and the kink is instrumental in this. So here's what's going on. You take that flask, it's full of water, The glass tube is down in it, and the rubber stopper makes it pressure tight, airtight. So then I just turn the heat on. And hot water expands, and so it'll expand into the tube. It'll push water as it gets hotter and hotter and [00:20:00] hotter. It'll push it up toward the top of that four foot tall glass tube that you can see in the gif. And when it gets to the point where you get really close, we're down at the bottom. It's starting to boil, but it is above what its boiling temperature should be. And the reason for that is the weight of the water that's in that glass tube, the weight of that water is acting like a pressure cooker. So the water down there is what we call super [00:20:30] heated. Well, when the water expands to the point where it pushes water out of the top of the glass tube, that instantly lowers the weight on the water. At the bottom of the flask, which remember is superheated, that reduction in weight causes it to flash into steam. The bubbles rise up. They kind of all get caught in that kink until they're just. Burst through it, and as they're rising up through that glass tube or through [00:21:00] the plumbing network in a geyser, it's pushing water above it - ahead of it, and it just comes out. It's kind of like a snowball effect, right? Once I lower the weight and I get some boiling going on. Now I'm gonna push more water out of the top that it's really gonna flash into steam and it explodes. I mean, it, it really is a cool demonstration cuz it, it pops at the surface.

Dr. Jesse Reimink: Chris. It is exactly right. It's a runaway effect. I mean, once this process starts, once you lose the weight, it flashes, to steam. It [00:21:30] blows out more water, it loses more weight, flashes more to steam. It runs away until the end stage, which is just, it runs outta water. It'll run away until it runs out of water. The plumbing system has been evacuated from all this water and steam, and then it settles back down until it builds up water. But when it builds up more water, it's pulling in cold water. And that cold water will like fill back up and then it takes some time to heat back up. And it starts this process over. And back to your analogy, if you refilled your flask with cold water and you just [00:22:00] kept the heat on at the base, this. Process would just cycle over and over and over depending on how much water and how much heat is going into the system. So that's the process here.

Chris Bolhuis: But the one thing that we need to note, Jesse, is point everybody to image number four, which is this video footage of one of the geysers in Yellowstone National Park, a very active geyser. And you can see this process. Those, the waters getting pitched out of that pool at the top by rising gas bubbles from below. It [00:22:30] exceeded the boiling point, flashed into steam and it's pushing water out ahead of it. And it just erupts at the surface. and you can really kind of see this cuz we're looking top down on this, you know, you can see the process that we're describing.

Dr. Jesse Reimink: And you can see how it kind of gets really activated. It kind of bubbles a little bit and then it takes off and you can see this feedback loop really take off there where it gets more violent and bigger and throwing more stuff up into the air as that stuff loses pressure.

Chris Bolhuis: I think, Jesse, we need to talk a little bit about why Yellowstone is so unique. Yellowstone has over [00:23:00] half of the entire planet's geysers. Which means it has something unique. And what it is is rhyolite. The rock that is inside the caldera of Yellowstone. Rhyolite is so rich in quartz, and quartz is just one of these minerals that is very hard to dissolve. It's very stable. Well, what happens though in Yellowstone because of all the quartz and it has a potent heat source? Well, [00:23:30] hot water. Is a very powerful solvent. Hot acidic water is even more powerful of a solvent. Hot, acidic, salty water is more powerful as a solvent. So Yellowstone has all of that. The bottom line is then you have this mineral that's called sinter, which is basically…

Dr. Jesse Reimink: Let me interrupt you real quick there, Chris. Uh, and I just want to bring this home to what people have probably seen before. People have probably seen quartz veins or quartz crystals somewhere around and. [00:24:00] That's what we're talking about. The reason that quartz veins are so common is because silica is really easy to dissolve in really high temperature, really acidic water. It gets picked up really easily and then it gets carried away and it gets deposited somewhere else when stuff cools down. So that's just hot water, hydrothermal water, moving silica around by dissolving it in one location, dumping it off in another location. That's what a quartz vein is. And quartz veins are everywhere. If you walk around in a backyard somewhere, you're probably gonna see some quartz veins without going too far. And so that's the [00:24:30] process That we're talking about and the reason why Yellowstone is really unique is this rhyolite, which is super rich in silica, and rhyolite is a lava. So it's, easier to dissolve stuff out of a former lava flow.

Chris Bolhuis: And this quartz that you described is getting precipitated, it's getting deposited on the plumbing network,

leading to the surface. Here's an analogy, but I, I think this works when sometimes when we get sick or we get this upper respiratory infection, we get phlegm. And stuff in our [00:25:00] esophagus, and that's very similar. And it looks a lot like the plumbing system that feeds geysers. And you cough and you kind of rip that stuff out, right? Well, geysers, this is what makes the kink - is deposition of this quartz, this sinter, inside the lining, leading to the surface of geysers. It makes then this system pressure tight, and that's what makes Yellowstone so unique. It has a potent heat source, it's got a lot of water. It's got fractured [00:25:30] and broken up rock, and it has the ability to create pressure tight systems by depositing quartz in its lining. That's the key.

Dr. Jesse Reimink: And that's what makes Yellowstone, you know, totally different from any other place. The hot spring, you and I went and sat in, you know, near the Collegiate Peaks. There wasn't abundant rhyolite everywhere to constrict this stuff. So there's mostly hot springs. And image number five in our stack shows again, a really schematic view of this. Basically the geyser plumbing system right in the center there is [00:26:00] more convoluted. It has these little steam chambers, but it's a convoluted thing. And there's a lot of constrictions in that plumbing system that a hot springs plumbing system does not have. And so geysers are just more complicated. Those big cavities were maybe areas where the rhyolite was dissolved and then up above it's constricted. And that's where that silica was precipitated on the throat forming this sinter. And so, Chris, just to, to wrap up the geyser and hot spring discussion here, the stuff with a lot of water in them. I think there's a couple interesting things to note. [00:26:30] And first off is that because it's all to do with this constriction, a really violent geyser eruption. Think of, when you have that, that sort of phlegm in your throat and you cough really hard, you get it out. Geysers can do that too. They can blow through this sinter and this restriction and open up their airway, their waterway, and become a hot spring if they erupt violently enough. So hot springs and geysers are not kind of stagnant things. They're constantly changing as their internal plumbing system in dynamics evolves over time. Likewise, [00:27:00] hot springs can become geysers. If they build up a bunch of sinter over time, they can turn into a geyser. And I mean, it doesn't happen immediately necessarily, but it can happen progressively over time. Right.

Chris Bolhuis: I think one other point that I wanna make regarding the regularity of geysers, most geysers are very irregular - Old Faithful being an exception. So what's going on with that? Why are geysers some geysers regular and others are not? It all comes down to the water and how [00:27:30] interconnected the plumbing system is with one geyser and another one. If it's isolated, for instance, Old Faithful is not connected with any nearby geysers or hot springs. It's not gaining or losing water. It's not taking water from other things. And likewise, another hot spring is not taking water away from Old Faithful. It's something that they call the exchange of function. Basically, if you have an isolated system, then a geyser can [00:28:00] behave very regularly. But if it's diverting water from one place to another and so on, it's, it's unpredictable then…

Dr. Jesse Reimink: Yeah.

Chris Bolhuis: water supplies unpredictable, therefore, the geysers are unpredictable.

Dr. Jesse Reimink: I think the analogy here, Chris, is, uh, you know, think of a, a new house. If you build your own new house, big, beautiful new house. Plumbing systems, relatively simple, straightforward. You turn your hot water on, you're getting hot water. Doesn't matter if somebody's upstairs taking a shower or not.

Compare that to a really old apartment building where you know, if you get hot water, you're lucky in your neighbor two [00:28:30] doors down is not getting hot water if your shower's on right, like. That's a really complicated old plumbing system, really intertwined and, and, you know, not isolated. And the other thing is that Yellowstone, as we've talked about before, is this active geologic environment. So little faults can happen. There's a lot of ground movement as the volcano is kind of breathing in and out. And so these things change pretty regularly and the plumbing systems can become isolated or intertwined and really dramatically shift. But they're so complicated. They're like incredibly hard to work this stuff out, how they're connected and, and [00:29:00] in what proportion they are.

Chris Bolhuis: That's a really good point, Jesse, and it makes me think of something that I want to bring up here too. I'm shocked. That old faithful is still as regular as it is. Because when you look at you know, Yellowstone is, it's very seismically active. Lots of earthquakes. All it takes is one fault to cut through the plumbing system, changing the water supply to Old Faithful, and then all of a sudden Old Faithful becomes anything but faithful. You know? [00:29:30] And but, so I'm amazed that it's still that way. I have thought about this a lot. I think I even say it to my students that at any time, Old Faithful could become very irregular.

Dr. Jesse Reimink: Uh, it's a great point Chris. It's a great point and it's worth thinking about while you're in Yellowstone looking at these things is to consider the fact that this might not be this way for, it probably won't be this way for very much longer necessarily. I love the geysers and hot springs. They're just so fun and geysers, you know, they're, they're more interesting in many ways than the hot springs, but the hot springs are particularly [00:30:00] beautiful. The next one, Chris though, I think, is maybe my favorite hydrothermal feature. And I'd be curious where you rank Mud Pots, because for me, these are just so funny. They, they just, it's like, I don't know. There's something about them that just cracks me up and they're really kind of mesmerizing in a weird way, these mud pots. So,

Chris Bolhuis: They’re very satisfying, I think.

Dr. Jesse Reimink: Yeah.

Chris Bolhuis: Mud pots, often called mud volcano. there's a place near Hayden Valley that's called Mud Volcano, but [00:30:30] geologically, we refer to them as mud pots. I think they're fascinating. We need to know a couple of things about them. Refer to image number six in your stack. This is just a, video footage of very thick, soupy, satisfying mud that pops at the surface. And it is, it, it is. And. You know, sometimes these things get to be quite active and they'll splatter mud out onto the boardwalk. Some of the boardwalks are so close that you can get hit with mud by these popping bubbles.[00:31:00] That's happened, to me a couple of times. It's, but it's okay. It's, it's awesome. Um,

Dr. Jesse Reimink: Chris is just having the most fun in the mud.

Chris Bolhuis: I am.

Dr. Jesse Reimink: getting hit by the mud pots

Chris Bolhuis: A couple key ingredients to this right is one, we need the water to be very, very acidic. So not any water will do, that's the thing about Yellowstone's Waters is dependent on where you are in the Caldera. The water can be very different from a chemical standpoint, so it has to be very acidic [00:31:30] water. What this does is it breaks that Rhyolite down the, remember we just talked about that the Rhyolite is key with almost everything. It breaks that Rhyolite down into clay. And here's the thing about mud pots, mud pot areas is, you can always smell them. It's one of my favorite things. It is a very pungent, rotten egg smell every summer, Jesse, when I pull into the mud volcano area with all my eager students [00:32:00] behind me, I sit there in the parking lot I sit back in my chair and I take a big, deep breath, and I just bring in that rotten egg smell, and I stretch my arms out and I'm like, okay, I'm home.

Dr. Jesse Reimink: Chris, I, it, I don't know what it says about you that, that makes you feel like home, the rotten egg

smell, but, um,

Chris Bolhuis: It does, uh, it…

Dr. Jesse Reimink: It makes me suspicious of being friends with you. Um, I think these mud pots are totally cool and image number six. I could just watch this on loop for [00:32:30] hours. I think it is just so satisfying and they're really definitely worth seeing and I think you nailed it. There's not much else to say, what…

Chris Bolhuis: Hold on. There is, there is. I got a couple other things. Oh, no, no, no. You're not doing that. No, no, you don't. We're not glossing over mud pots. Jesse, we got, we got some more things to talk about so you

Dr. Jesse Reimink: I just want to watch him. I'll just tune out here, Chris, and I'll just watch this, this video looping.

Chris Bolhuis: All right, you, you, you go, I got this. All right, that's fine. You but the, the smell is hydrogen sulfide. It's H2S and [00:33:00] we are very, very adept at smelling this. We can smell it in very low concentrations, and yet it's still very pungent. But if you have mud pots, you have acidic water from the H2S. And what happens are extremophiles, these, again, extreme loving bacteria, they use the H2S in the presence of oxygen, and they make sulfuric acid, which is a very potent acid. This is like car battery [00:33:30] kind of acid. Okay? And the other thing, so we need this very acidic water to break the Rhyolite down into mud, but we also need a shortage of water because if you had more water, the mud pot area would wash away the mud and you would just be left with normal hot springs. So the shortage of water here is also critical to keep the mud in place and not wash it away and dilute it.

Dr. Jesse Reimink: And it makes it, you know, it concentrates that [00:34:00] acidity as well. You know, having less, there kind of concentrates acidity so you can derive more acidic water, in this way. But, they're really cool. There's a lot of good spots to see mud pots and I think, Chris, we should interject. One thing at this juncture, and probably should have said this before, is that you gotta stay on the boardwalk. These things are, you said, you know, you can get splashed on the boardwalk sometimes with this mud, but you gotta stay on the boardwalk. Like, these hydrothermal features are really hard to predict. It's pretty easy to fall into them without knowing that you're walking [00:34:30] over, a mud pot that's soon to break through the surface or, falling into a fumarole hole or something like that. They're not to be toyed with these hydrothermal areas. I think that's an important thing to note right now, because mud pots, cuz I think, um, yeah, we've seen. Well, there's been examples of, you know, bison falling into mud pots and dying because, you know, they fall into the mud pot or they break through and fall into the mud pot and that can just as easily happen to, to humans as well. And there's been examples of that.

Chris Bolhuis: When that happens to bison, they are gonna close down that, thermal area because a [00:35:00] dead bison on the edge of a mud pot and the edge of a hot spring is gonna attract grizzlies. And it's just not a good combination. But I wanna just maybe go a little bit further than that. I see this every year. I see people that step off the boardwalk. I think it's important for people to… in, maybe in a polite way, but in a forceful way is to remind people not to do that. These are our national parks. Yellowstone is ours. And taking ownership means having the courage to stand up and [00:35:30] say, no, please don't do that. Not only can you hurt yourself, but you can also damage the hydrothermal features for future people to enjoy and love and yeah, so it's just, it's not a good idea. We see it all the time. All too often. Okay. Jesse,

Dr. Jesse Reimink: Let's wrap up the hydrothermal features here by talking about fumaroles, which again, we were

moving from most water to least water. We're now at the end, fumaroles have the least amount of available water, and I think people can visualize these pretty well. It's in effect a [00:36:00] steam vent coming out of the earth. It's an area where steam, often carbon dioxide, usually that's sourced from the magma itself down below, like magmatic gases are escaping. H2S is also a part of that. And this sort of smelly combination of gases, can escape through holes and cracks in the plumbing system. And the water, it just boils away. And they can make these really fun, interesting, crazy hissing noises as the gas is escaping through these vents, kind of whistling or hissing noises as they're [00:36:30] escaping. They're very cool, they're very common. And also they can be, again, sort of to reiterate, kind of dangerous. Like this is super hot, super reactive gas that's coming out. You don't really want to be too close to any of this stuff.

Chris Bolhuis: It's basically, you know, it's water that's boiling away before it gets to the surface, you know, which makes that hissing so. I don't know, I think it's common sense. That means it's gonna be super hot.

Dr. Jesse Reimink: so yeah, they can be extremely hot Chris, and I think there's one thing that's interesting to note that kind of covers the next two images, but image number seven is again, a [00:37:00] schematic view of where in really general sense where these types of things occur. We talked about hot springs and geysers as having the most access to water or the most water around. Mud pots having slightly less or substantially less water. And then fumaroles having far less water. Now, one general way to think about this, and this plays out when you look at the hydrothermal basins or where geysers and hot springs are in Yellowstone National Park, they're often low down in sort of low [00:37:30] relief areas. They are closer to heat source.

Chris Bolhuis: Hence the name Basins.

Dr. Jesse Reimink: Hence the name basin, right? They are, they're in basins. This is where water collects. They're also closer to the heat source, but this is where groundwater can collect more frequently and so you get more groundwater in these basins and that's why we have hot springs and geysers there. So this image number seven is just showing that fumaroles and mud pots will often occur a little bit more on hill slopes, away from a ponding groundwater supply.

Chris Bolhuis: Can I interject to your second Jesse? On the left of image number [00:38:00] seven - think of that as a lava flow. These really thick rhyolitic lava flows that happened after the last eruption. Being high up on the flow, it's further away from the water source. It's further away from the heat source, so that's where you're gonna get the fumaroles a little bit further down maybe on the hillside, you get the mud pots, and then down in the basin itself, that's where all the hot springs and geysers are gonna be, and that's really kind of cool. As you drive around in Yellowstone National Park, this is something that you should see. I think that [00:38:30] that enriches the experience is knowing, oh my gosh, look at that. That's a lava flow. That big hill, there's a lava flow and I can see the steam coming out of the hillside and you know, it's just it's just this understanding about what's going on and how that understanding enriches your experience driving through Yellowstone. Such a cool thing.

Dr. Jesse Reimink: Let's just point to image number eight here, which is just a gif that is highlighting the more popular geyser basins in Yellowstone National Park. So this is just showing sort of in a really general sense. This is not [00:39:00] all of them, but some of the more popular ones that people will, will probably visit. Just showing where those things actually are. And so Chris, I think this brings us to the end and we have a couple FAQs that we're gonna cover here related to geyser's. And, the best one to first year given looking at image number eight, the, distribution of the popular Geyser basins. I think the question is what actually defines what a Geyser Basin is? Like, what is that? What does it mean?

Chris Bolhuis: Um, the question is what exactly is a [00:39:30] geyser basin? Is that what you're asking me?

Dr. Jesse Reimink: yeah,

Chris Bolhuis: All right. It's just, there's no set criteria. It's just basically, it's a, it's a low area. It's a basin that has a lot of hot springs and, and geysers and hydrothermal activity. And so we call that a geyser basin. and it can have all the features. It can have mud pots, fumaroles, hot Springs, and geysers, or it can just have some of the features. It just has a cluster of them. It's got a lot.

Dr. Jesse Reimink: Yeah, that's pretty, uh, pretty easy. And then I think a lot of people ask the, the question as [00:40:00] well. What's the most active thermal area in the park? And I think, let's put “active” here because there's different definitions of what that might be. But what is the most active, and maybe Chris, I'd be curious, what's your favorite thermal area in the park as well?

Chris Bolhuis: I can't answer the favorite one. It's like asking me what my favorite kid is. Uh, I can't do that. But I think it's widely regarded as Norris Geyser Basin. Is one of the more active thermal areas in Yellowstone. [00:40:30] It's certainly is the hottest water near the surface. It's interesting because it has this intersection of three major faults there you know, it has the biggest geyser - Steamboat Geyser that has been more active in recent times. It garners a lot of attention. Norris Geyser Basin is often described as the, as the playground for the demons of the underworld. Um, and you get to see... You, you see this when you drive, you [00:41:00] know, near Norris in the morning when the, when the air is nice and cool and brisk and so on, you get this more dramatic effect of the fumaroles putting steam into the air. Just, it, it looks like a playground for the demons of the underworld. It, it really does and you know what else Norris does? Norris feeds the water to mammoth hot springs, 20 miles to the north. It has a lot going on. And so I think, it gets, maybe the most attention is the most active [00:41:30] thermal area in the park. I don't know if I agree with that, but, it's up there.

Dr. Jesse Reimink: Yeah, a very, very, very cool, uh, place. And, and these temperatures can get really hot. I just want to put a number on what you said there. It's 459 degrees Fahrenheit. Was the, the, the highest temperature recorded, in a scientific drill hole. This was a thousand feet below the surface, but that's so hot. You can see why this is dissolving rock at that temperature. So, just totally cool.

Chris Bolhuis: I have one thing that I wanna bring up that we should have talked about earlier, but I think it's noteworthy, is when you go to a [00:42:00] mud volcano or a mud pot area, it depends upon when you're there. The mud will take on very different characteristics, like early on in the summer or late spring, it's gonna be very soupy -very wet - cuz it has a lot of water there. As the summer goes on, these mud pots become much drier because Yellowstone tends to have dry summers and that's when the mud takes on I think that really cool dynamic that you and I like, where the, that mud's just like fried eggs. It's, it's, you know, [00:42:30] it, it spits the mud up. It's very thick and gooey and anyway, it just. The dynamic of that area changes according to the water supply, and that's the seasons.

Dr. Jesse Reimink: so fun. I could sit and watch a mud pot all day. Happily. That's a very, very, very fun thing to watch. Okay. Yeah, a great day. That's, and a really interesting point to, to again, pay attention to while you're driving around, depending on the season that you go to Yellowstone and, and you know, take note of all this stuff cuz there's cool explanations for them. So, Chris, that is wrapping up chapter [00:43:00] four, the overview of hydrothermal features. What do we have in the next chapter? Chapter five.

Chris Bolhuis: in chapter five, we talk about the Grand Canyon of the Yellowstone River.

Dr. Jesse Reimink: Ooh, that's a very fun one. Excellent. All right. Check you next time.