The Shape of Yellowstone - Dr. Mike Poland, Scientist-in-Charge, Yellowstone Volcano Observatory
Dr. Jesse Reimink: [00:00:00] Hey there today, we are really excited to release a short clip from an interview we did with a really, really, truly exceptional geoscientists. Dr. Mike Poland, who's the scientist in charge of a really special place, both in geology to Chris and myself, and [00:00:30] really in us national history, which is the Yellowstone volcano observatory. Our discussion with Mike covered a super wide range of topics. So we decided to cut out this little bit and release it this week. Mike is an expert in geodesy, which as he says, is studying the shape of the earth. And it's a technique used to investigate a wide variety of processes. On an, in the earth. So we focused this discussion on geodesy before we get to the interview, just do one thing for us. If you enjoy our show, head over to planet geo cast.com and [00:01:00] there you can support us. Or if you prefer leave us a rating and review, that really helps us spread the word about geoscience. Enjoy the short clip and tune in next week for more from Dr. Mike Poland.
so, uh, we're, we've been talking about earthquakes quite a bit and, we've seen this stat where Yellowstone has, hundreds thou a few thousand, uh, earthquakes a year. can you talk about those, and then we'd sort of like to get into sort of your expertise in, in jealousy. [00:01:30] But these earthquakes, they occur, occurring kind of swarms. They're pretty small. Uh, do people feel them? Are they often felt if like people who are visiting Yellowstone? Can you kind of describe these for people?
Dr. Mike Poland: Sure. So Yellowstone is one of the more seismically active places in the country. , and this is one of the reasons that there is this, , broad public concern, I'd say for Yellowstone as a volcanic.
Dr. Jesse Reimink: A and why is it one of the more seismically active in the
Dr. Mike Poland: well, there are faults everywhere. So [00:02:00] Yellowstone is sitting right on the edge of the basin and range extensional province. So if you drive from, as I did many times as a kid from say, central California to, salt Lake City, you go over these mountain ranges and then into a valley, and then a mountain range and a valley, each one of these mountain ranges has a fault associated with it. That topography exists because the entire west is being stretched, so it's being stretched in an east, west way, and you get all these north, south mountain ranges. =Each one of these has a fault, and that's why you get [00:02:30] these magnitude six earthquakes, , in the middle of Nevada or Utah or Idaho. All the way down to Sonora in Mexico. So those faults, exist in the Yellowstone area as well. You can see them to the South Grand Teton. You, it's in the north in Montana. He lake is one of these faults. so there are faults. Anyway, the area is weak because it's hot. that is the magma chamber beneath Yellowstone and there is a lot of water moving around. Yellowstone is the [00:03:00] highest part of the Rockies on average. Buoyed up by all of that heat from the magma system. And so it gets a tremendous amount of snow and rain. , and so there's a lot of water moon around in the substitute. There's water that comes off the magnetic system as well. Water releases magma and water is, is a component of, gas and, and the volatile content, these are these fluids that come outta magma. So there's a lot of water moving around. Hot, weak crust that's got a lot of faults in it. That is a recipe for small earthquakes. And there are typically [00:03:30] 1500 to 2,500 earthquakes a year. They're 99% of them are magnitude two and less. No one feels those. But yeah, every, every year we have a few that are felt. , there's, , typically, you know, a magnitude four every few years, and those are always felt, , every so often. There's a magnitude five. We had a magnitude six in 1975, , and then there was that magnitude seven just west of the park in 1959. So, , yeah, but the common question is, well, isn't that magma moving? And there's only one seismic swarm [00:04:00] that we know of that had any characteristics that were even remotely reminiscent of magnum moving around that occurred, um, in 2008, 2009 beneath Yellowstone Lake. But even then, it's, it's sort of suspect. We don't really know. But everything else has these characteristics of water interacting with faults.
Dr. Jesse Reimink: I think a lot of people listen to this might ask the question of how do you know, how can you tell when a swarm is magma moving versus. A fault reactivating or hydrothermal fluid circulating and expanding.[00:04:30]
Dr. Mike Poland: Well there's, there's something to the way the Seism mission you may propagate. So if it's moving in a certain direction, like, uh, a magnetic intrusion magma underneath the ground, that's moving in the, in the direction. And then the question of whether or not there's defamation associated with that seismicity. If it's just water infiltrating a fault and causing the fault to move because you're sort of ratcheting up the poor pressure or making the, the fault a little bit easier to slip, you're not necessarily gonna see a lot of defamation associated with that because the faulting [00:05:00] is really small. But if you had an earthquake swarm that was associated with, for example, spreading, so you could see, say from GPS sites on either side of the seismicity, that the GPS sites were moving apart, and that was a sign that volume was increasing. You were pushing something in there. That's not something we typically see with earthquakes that are associated with water interacting with faults. And there was a slight amount of deformation that occurred with that oh 8 0 9 swarm beneath the Yellowstone Lake. [00:05:30] Uh, it was really, really small, , but it was detectable and, and frankly it's sort of a testament to the technology we have these days to be able to detect that kind of motion. , so that's still ambiguous, but that's the only one that's ever been recorded in Yellowstone that had deformation associated with.
Dr. Jesse Reimink: okay. And this is a really great, lead into the next sort of thing we wanna talk touch on is, is your, your expertise here. Uh, which is, I, there's a lot of hard words and there's a lot of fun words in Geology. And Geodyssey is one of the ones that I find as like the most fun [00:06:00] and the most mispronounced perhaps. So this is like geo Desi is what it
Chris Bolhuis: wait a minute. How do you geo dessi? Is that what you usually hear or what?
Dr. Jesse Reimink: Desi, geo, desi, Giada. Yeah. So all sorts of different pronunciations, but can you like just, what is this word? What is your expertise at a really broad level? And then I think this is probably a place where we're gonna go into the weeds.
Dr. Mike Poland: great place for it. Um, GI Odyssey, it is a study the shape of the earth, basically, , the shape and the gravitational field of the earth. And so a [00:06:30] geist would be, uh, someone that studies the shape that changes the gravity field. , those kinds of parameters. And my specific area of interest in volcano geodyssey is how volcanoes change shape and how they change their, their gravity field.
Dr. Jesse Reimink: uh, it's a cool party trick. You know, say I'm a and oh, I study the shape of the earth. You know, that's a pretty cool party trick I'd say. So how do you go about doing this? What are the techniques? You referred to the, the technological advances, which are incredible. I don't know a lot about them, but [00:07:00] I, they're amazing and always blow my mind.
Dr. Mike Poland: Oh man. I could go on, like, I could go on about this for a long time, but I'll spare the, the gory details and the key technologies today I'd say are effectively gps. GPS is the US system for navigation and positioning. , the kind of global method that name for it is gnss, global Navigation Satellite systems, because different countries have different, systems. So we can use those and, and record positions with receivers, [00:07:30] basically the same thing that's in your phone or in your car. But we record a different, kind of, the part of the signal that allows us to get millimeter level precision with positioning. And then you repeat that measurement on a daily basis and you can see how your, , antenna, which is cemented to the ground, how it's moving around with time, which is how
Chris Bolhuis: Oh, okay, Mike, so wait a minute. You're saying that you do this gacy at the ground level? So, Well, okay. How often do you use satellites [00:08:00] versus like walking the contact? I mean, how's that work?
Dr. Mike Poland: So for uh, gps, we would generally, , take a, an antenna GPS antenna that receives the signals and we would install it in such a way that it is very well coupled to the ground. , you would usually, you know, drill a hole into the ground, put a, a monument there so that it's very well coupled and then you just sort of screw the antenna onto the top of the monument. And now when the ground moves, the antenna moves.
Dr. Jesse Reimink: Would you only anchor that in bedrock or put it in soil [00:08:30] too,
Dr. Mike Poland: well bedrock is easy, right? Cuz you don't have to, you know, dig a, a giant hole or drill a giant hole. If you wanna put it in someplace that's not bedrock, you can do it. You can basically, uh, drive a, a survey rod down into sediment. And you keep sort of attaching Robs, you know, and driving it into the ground and you go until it won't go any further. And that sort of is anchoring it. And, and sometimes you're going down like hundreds of feet. It's like it [00:09:00] takes you days to do it. Um, but that, that is really not preferred because, the sediment can expand and contract as water gets in and freezes and thaws and, and so you could get all kinds of spurious signals. Those are not really stable places. So I would not choose to put something in an environment like that unless there was a really compelling reason. And, been a couple places where we've, where we've done that. But usually you look for bedrock,
Dr. Jesse Reimink: So how many GPS antennas are there in Yellowstone right now for
Dr. Mike Poland: uh, in terms of continuous [00:09:30] sites. There are about 15 in the park and there are about another 15 that surround the park. We supplement that during the summer months with. Something we call semi-permanent gps. The continuous ones are connected via radio links, so we get the data in a continuous stream. But there are some places where radio communications are hard, and of course you're not gonna just go and put, you know, radio towers up all over the place in Yellowstone. It's mar the landscape. It'd be really expensive. Yeah, it's, it's a bad idea. So we will put [00:10:00] temporary sites, uh, and we'll put them out for the summer months. They're pretty low to the ground. They run off solar panels. They don't have radio links. So you let them run for the summer and then you come at the end of the summer, you pick 'em up, you download the data, and you have sort of five, six months of data for this subset of sites. There's about another 15 of those in the park.
Chris Bolhuis: you don't have a ton of bedrock inside the Caldera to put these, do you?
Dr. Mike Poland: There's enough, um, the lava flows, there's a lot of lava flows in the Caldera. Uh, you can get to,[00:10:30] , and there are outcroppings even in, you know, Hayden Valley, which is mostly like lake sediment and glacial sediment. , you can find the loud croppings of rock and, and drop a put a put a monument there. , the key is finding the sort of environment that will get you the data you want. You need it to be in the right place, or you don't want 'em to have all 15 of these in the same place, right? They need to be spread out. , you don't want them in areas that are gonna be affected by processes you're not interested in. So we have actually avoided to this point putting GPS [00:11:00] stations in hydrothermal areas because those deform light crazy because water's moving all over the place. And if you're interested in whether or not the whole volcanic system is going up or down, you don't want to have your GPS station next to a geyser, which is, you know, going crazy. Um, And that's a whole nother can of worms there because okay, now we've, we've got the volcano system monitored pretty well, but shouldn't we also be monitoring these geiser systems? Cause we talked earlier, like they explored from time to time. So we need to get into that as well, , at some point and install [00:11:30] GPSs in the places we've avoided. But, , yeah, there's enough bedrock, but you gotta be careful about where you put them. It, it's not, uh, it's Not a
willy-nilly
Dr. Jesse Reimink: Not a will. Hey, thanks for listening and tune in next week. For much more from our interview with Dr. Mike Polin scientists in charge of the Yellowstone volcano observatory. Before you go, please check out our camp geo conversational textbook for geoscience there, we combine audio discussions about key concepts with all the images you need to learn the basics of our amazing [00:12:00] field of study it's free and accessible at the first link in your show notes. You can follow us on all the social medias, where at planet geo cast, you can send us an email at planet Jocasta, gmail.com. We promise we will get to those eventually probably in a big office hours episode. We're putting that together now. So send in your questions and you can, , follow subscribe, support us@planetgeocast.com.
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