 It's one o'clock on Tuesday, May 3rd, so you must be watching Science at Soast. I'm your host Pete McGinnis-Mark, streaming live from beautiful downtown Honolulu. Every week we get a new graduate student to come in and talk about her research, and today I'm really excited. We've got Rose Gallo, who is a volcanologist and a patrologist, and she's going to be talking about the 2018 eruption of Kiloway, a volcano. And that's really good, because Science at Soast is all about the school of ocean, earth, science and technology. So Rose, welcome to the show. I'm delighted to have you on. Kiloway is one of my favorite research areas. So welcome again. Thank you very much. And I usually ask the students if they can just say a little bit about themselves. I understand you're a second year PhD candidate, but where have you done some of your earlier studies? So prior to joining UH Manoa, I did my master's at Northern Arizona University, and I did my bachelor's degree at the University of British Columbia. And I understand that your master's degree at Northern Arizona was on a different type of volcano? Yes, very different from Kilowaya. I studied Kempiflake Great Caldera, which is a very large, very explosive volcanic system, though it has in common that it's also still active and in an area where even more significant population could be affected by future eruptions. And I think I'm quite insane. Kempiflake Great is just west of Naples in Italy? Yes. Well, part of Naples is actually in it, but most of Naples is east of Italy. So you're trying to study a little bit safer volcanic eruption for your PhD. I know you weren't here during the 2018 eruption, which is what we're talking about today, but if we go to the first slide, maybe you can just lead us through a little bit of what the eruption history of both Kilowaya and perhaps even the big island as a whole was like. So this map is highlighting first on the left where the most recent eruptions have been since, I think, about the 1500s. So you can see that most of the surface of Kilowaya has actually been covered in new lava flows since that time period. And there's also been quite a number of lava flows on Mauna Loa, but Kilowaya is by far the more active of the two. And then on the right hand side, it's showing the east rift zone of Kilowaya. Kilowaya has two rift zones, the southwest and the east rift zone. And my area of study is the lower east rift zone, so the furthest east portion on the eastern flank of Kilowaya. Okay, well, viewers, can you explain a little bit more about what you mean by a rift zone? Sure. So Kilowaya's sort of areas of concentrated eruption are the summit crater, Halimaumau, where you can sometimes, such as now, see a lava lake. And then there's two other areas where eruptions tend to be concentrated, sort of curvy linear features that go off to the southwest and to the east from the summit of Kilowaya. And these are just locations where eruptions tend to be concentrated because of the structural features of Kilowaya where openings can be created for magma to flow through and eventually come to the surface. So think of the rift zone as having an underground pathway, perhaps, for the movement of magma. And I think, you know, the older viewers might remember Kapoho eruption in 1960 or Mono Urulu in the late 60s, or even Poohua from 83 onwards. They're all on the rift zone. Is that right? Yes. Okay. And so does Kilowaya produce these lavas along the rift zone, or do they come from, like, beneath Halimaumau? Typically, a combination in the 2018 eruption and also in most of the other historic eruptions in the Lower East Rift Zone. So there's the 1960, as you said, the 1955, the 1840, and the 1790 are considered the historic eruptions, and most of them include a combination of magmas that have been stored underneath the rift zone since some previous eruption, when they traveled there and they've just been sitting there cooling under the ground, changing in composition a little bit. So that will usually be combined with some magmas that are coming down along the available pathways from the magma chambers beneath the summit. I always think of a rift zone as the plumbing system of a volcano. So I know they're not pipes in the traditional sense, but yeah, sometimes pipes get blocked and that's where the magma resides and things like that. But the 2018 eruption was truly spectacular. I think the second slide will show much more detail what was going on. This is close to Kapoho again, right down by the coast. Yes, the main phase of it entered into that area. And the map just shows some of the phases into which the 2018 eruption was divided by researchers based on a combination of the chemical composition of the lavas and the eruptive styles. Okay, and we see some nice colored lava flows. Over what kind of time period were these erupted on the surface? Do you know what the dates were? They all were in 2018, but is it a matter of days or minutes? The entire eruption took months. It began on May 3 and ended approximately August 4. The majority of that time period from sort of the end of May to the end of the eruption was just phase three, the dark blue, which makes up the majority of the eruptive volume, a lot of which cannot even really be truly perceived on the map because so much of it went into the ocean in this form, sort of a vertical pile off the coast. Okay, okay. And I think you got some great pictures from the US Geological Survey inside three just showing what are these typical kinds of fumes in your studies. You must have looked at the eruption types. What do we have here and any idea of the scale of these lava flows? Yeah, so the upper two images are from the earlier phases of the eruption and they're showing that in the very early phase of the eruption, there wasn't a large volume of lava being erupted and the lavas were sort of sticky and slow moving and didn't travel very far. So in some places like in the top right picture it's all that was formed was a small fissure opening in the forest and a pile of spattery lava and in other places there were short lava flows that moved mostly slowly through the community whereas in the lower two images that's from the last phase of the eruption, when these enormous lava flows and flow fields were developing and then you have the large flow channels and the centralized cone. Some of our viewers, I think the first two images, is that Leilani estates where the vent started to open up? Yes. Okay, so any idea why did the eruption evolve this way? Why did it start off with just small volumes being erupted on the surface and then the last two, the bottom two slides you showed, quite spectacular. Any understanding on why it sort of changed its character? What we believe happened in this eruption and also in a similar fashion in prior eruptions is that you have these small ish magra bodies sitting within the rift zone that were placed there during previous eruptions they've been sitting there cooling for some time and then when an eruption begins magma is coming down through the piping of the rift zone from the summit but before it can come out at the surface it pushes out the old magma ahead of it which is cooler and thicker because it's been sitting around and crystallizing for probably decades so when that magma comes out first it begins erupting it there isn't very much of it and it comes out slower but then once that lava has been mostly pushed out it begins to mix in with the new magmas coming down from the summit reservoirs and then that magma takes over so the last phase of this eruption was really not entirely but almost exclusively the magmas that would have been coming down from the the central reservoirs and they are much more fluid, hotter and quite a large volume of material. You mentioned something that it might lava or magma might still be fluid after several decades so they don't chill very quickly is it possible that you have hot magma underground for decades after the eruption? Yes absolutely I think we should assume that the 2018 eruption probably in place some small magma bodies of its own perhaps into the spaces left behind by previous things that were evacuated and we should expect that the end of that magma to be cooling beneath the Lower East River Zone right now and it will be changing the composition as it cools and perhaps in some future eruption it will be pushed out at the beginning of the eruption. I think slide four will be a good time to just tell us a little bit more here we're seeing part of the East River Zone but particularly your kind of work which is I believe a patrologist she studies you know the chemical composition of the rocks can you talk us through this really elegant diagram here with the five different labels at the bottom? Yeah so this represents sort of one model for how the plumbing inside the East River Zone of Kilauea is set up so you can see that there are two magma bodies shown underneath the summit of Kilauea stacked above one another and it's not like entirely known which one the magma would come more directly from during a rift zone eruption most people tend to think the deeper body but it's it's not certain so you have connectivity between the summit magma chambers and the rift zone and then in the rift zone you have all these small magma bodies associated with the previous eruptions that are just kind of sitting there and you can see that the magma that would be flowing down from the summit gets interacting with those. And just to help the viewers the gray part presumably is the land surface and then the light ground is essentially going deeper and deeper on the ground right so this is a three-dimensional image or artist rendition. And what do the numbers mean? You've got different types of I see mafic basalt and and day site at different places. What is the significance of that? So that's showing a hypothesis for where the different chemical components of the 2018 eruption come from. So you have there was three chemical end members involved in the eruption. The dark blue is what erupted at the end of the eruption and that's proposed to come from the summit magma chambers. The green high titanium basalt is what erupted at the very beginning of the eruption and that's thought to be derived from magma bodies that were perhaps formed around 1955 or 1960. And then there is the andesite which erupted at just one fissure sort of midway through the early part of the eruption. The very unique composition for Kilauea nobody was aware of any andesites erupting prior to 2018 and all of the compositions in the eruption are derived from one of those three end members or some combination of them. So it's showing the potential magma bodies each of these would be sourced from and then it's showing the Puna day site magma body next door. Now I sort of imagine activity at Kilauea was being fed by a mantle plume a hot body of rock deep beneath Hawaii. But you're seeing five different types of magma being erupted. Is that just because some of these magma bodies have sort of sat on the ground changing their composition? How do they change their composition? Yes precisely if they've been in the shallow crust for some period of time they begin to cool and they begin to form minerals as they cool and then the remaining fluid magma will have a different composition than it had before the minerals were taken out because the chemical composition of the minerals will be subtracted from the composition of the magma. Okay so the original magma coming up beneath Halimaumau starts to differentiate to produce these other minerals and I think slide five will show just some examples of what you might be able to see and these are what the images of what kind of rock. So these images are showing melt inclusions in the three common mineral types that are found in Kilauea basalts, olivine, peroxines, and plagioclase and they're showing one of the before subject of my study is trying to look at the compositions and particularly that of the volatile molecules like water and carbon dioxide that would be in these magma chambers beneath the rift zone and to get the best preserved compositions of these things as they were in the magma chambers we have to look at the magma that was trapped inside the minerals that formed in those magma chambers. So the melt inclusions are volcanic glass that represents that trapped magma inside the minerals. These are fascinating images but can you explain to the viewers a bit more first of all what the size is but they don't look like rocks to me. They almost look transparent. How did you get these images? So these are thin sections microscope slides they're very thin slices of rocks and so when you have them sliced that thinly and you look at them out of a microscope the light passes through them and you're able to see them in this way. So these images are quite small. They're we're looking at individual minerals that are probably a couple millimeters across and the melt inclusions inside them are tens of microns at most. Okay and would it be fair to say that each one of the five different types of magma you've been studying have different numbers of crystals or different crystal sizes or even compositions? Yes each of the like the different phases in the 2018 eruption where there's plenty of overlap for example all of the phases contain some olivine. The olivine has slightly different chemical components in the different phases of the eruption and for example the last phase has almost exclusively olivine whereas the other two phases have a lot more platruchlase and peroxins as well. Okay would it be fair to think of these almost as different fingerprints of different rock types that you know you can take a thin section like the ones we just saw and you could say oh it must have come out of the vent at this time or something like that? Yeah I mean I feel like that's kind of the first step of patrology is that you look at a little sample of a rock that's meant to represent some phase of the eruption or some rock body and distinguish them based on the minerals and their shapes and sizes and textures and compositions that you can determine. I guess what I was thinking of is if I just handed you a thin section like the ones in the slide could you tell me either where it was in the whole sequence of activity on the volcano or which vent it came from? Are they that different that you can pinpoint the phase of the activity where it was erupted? Within the 2018 eruption? Yes if you told me it was just this is from the 2018 eruption tell me which phase it is? Yes if I had the whole history of Kilauea? No there is a lot of similarity Kilauea produces a very limited range of compositions and lots of rocks that look quite similar to one another but the 2018 eruption was pretty unique in terms of the compositional diversity within it. Interesting interesting now we've seen some slides of where the eruption was down at the coast but I think slide six will show us that it wasn't just restricted to activity down at the coast that these are a couple of air photographs can you tell us a little bit about what we're looking at here? Yeah so these are images showing the summit caldera of Kilauea before and after the 2018 eruption and what they're showing is that the caldera significantly collapsed throughout the eruption there wasn't really a distinct eruption occurring in the summit caldera and that there wasn't really any new lavas erupting from that location but because of the withdrawal of the magma from the magma chambers below the summit so that it could go to the rift zones there was no longer support underneath the rocks at the summit of Kilauea and the caldera began to fall in and as the rocks sort of were falling into the withdrawing magma and bashing against one another they did put up sort of a plume of ash but it wasn't mostly fresh material at all. Thank you some of our viewers have been out to the volcano area but the size that we're looking at here the caldera is about what three by five kilometers in size and that on the left image the white smoke that's coming from Halimao which was what 500 meters across or something like that so it's a quite a big feature and what you're saying is that the collapse that we saw was due to magma that was once underneath Halimao moving down the rift zone so that's the source what about the the mental plume beneath Halimao that was unable to keep things going? Yeah I mean there should be at least constant sort of new supply of magma from the mantle plume but it's only coming up at well we don't I don't think anybody knows exactly that the rate that it's coming up but there there's sort it cannot come up as fast as it likes to replenish relative to the rate of the eruption that's recurring so it's probably still refilling now and it has refilled enough to put a lava lake back in the summit crater but it took a few years to fill up the magma chamber again to the degree that we were going to see lava at the surface and probably would that slower supply rate be one of the reasons the eruption stopped it just ran out of the new molten gut? I think yes I mean it did not run out of magma in the summit caldera like it did not empty the summit caldera but at a certain point the pressure was low enough that there wasn't the magma was no longer being forced down into the rift zone because the pressure was low in the summit of the chambers. Now this collapse the next slide slide seven starts to show us a little bit more of this amazing collapse event I think these are radar images aren't they? Yeah they are it's a digital elevation model so I believe it comes from some sort of radar survey that's done fairly. Yeah and we've got two time periods here and I think so for viewers look up where Halimao Malpreau is and we go on to the next slide it starts showing huge changes and the scale of one kilometer yeah it's like five eighths of a mile. Do you know how much the collapse how deep the collapse was? Yeah so inside Halimao crater it's subsided by approximately 500 meters I believe whereas the sort of full caldera floor it was a little bit more than 160 meters. Right so that's like a 1500 feet drop in the middle and you know maybe 400 feet on the outsides they're incredible that you know the landscape can change that much so what's it like now? I know you're not doing research on the co-inactivity but I think the next slide would show us a little bit about how even this was I guess just over a month ago the survey put this map out what's happening now? So right now there is once again an eruption just in the summit crater there is an active lava lake which it's possible for visitors to view from a designated viewpoint within the natural park and this eruption has been ongoing since late last year and there was another eruption that occurred in early 2021 started in late 2020 after there having been a gap since the end of the 2018 eruption where there was no activity in the summit so now there's an active lava lake again and you can see the molten lava. Right have you seen the lava lake but they're meant to be spectacular particularly at night? Yes it's beautiful I went at night a couple of times several months apart and it looked quite different both times in terms of well the center of the activity was the same but in terms of the degree of exposure of molten material and one of the times I went there was sort of a waterfall of lava cascading down a feature in the lava lake so it's quite changeable in its small features at least over time. That was terrific Rose well unfortunately we've run out of time I wish I could spend more time talking about Kilauea volcano but let me just remind the viewers you've been watching Science at Soast I've been your host Pete McGinnis Mark and my guest today has been Rose Gallow talking about the 2018 eruption of Kilauea volcano so thank you for watching please join us again next week and thank you Rose for being on the show and so until next week it's goodbye for now. 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