What’s happening at Kīlauea Volcano?

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On December 20, 2020, an eruption began in Halema‘uma‘u at Kīlauea Volcano’s summit, ending a two-year eruptive pause. The water lake that appeared at the bottom of Halema‘uma‘u in late July 2019, which had grown to be over 50 meters (55 yards) deep and more than 10 acres in surface area, quickly vaporized and was replaced by a growing lava lake. The eruption began as three fissure vents in Halema‘uma‘u and has remained dynamic. In this talk, USGS HVO scientists who monitor the eruption with permission from Hawai‘i Volcanoes National Park will share their insights and observations as of January 21, 2021. Were there eruption precursors? What does the new eruption mean for hazards at Kīlauea’s summit? How is the lava lake monitored and what is known about it? Join USGS Hawaiian Volcano Observatory scientists David Phillips, Matt Patrick, Tricia Nadeau, Ingrid Johanson, and Peter Dotray as they answer these questions and more.

Talk section timestamps

  • Intro and HVO update – David Phillips – 00:22
  • Geology update – Matt Patrick – 04:43
  • Volcanic gas update – Tricia Nadeau – 16:43
  • Ground deformation update – Ingrid Johanson – 27:23
  • Seismology update – Peter Dotray – 43:24
  • Exit and closing comments – David Phillips – 59:22


Date Taken:

Length: 01:02:13

Location Taken: HI, US


What’s happening at Kīlauea Volcano?

David Phillips, acting Scientist-in-Charge

Hello, welcome to Volcano Awareness Month 2021. I'm David Phillips, the acting scientist in charge of the USGS Hawaiian Volcano Observatory [HVO]. I'd like to start by saying a few words about the Hawaiian Volcano Observatory. HVO is part of the US Geological Survey’s Volcano Hazards Program. HVO’s mission is to monitor, investigate and assess hazards from active volcanoes and earthquakes in Hawai‘I, to issue warnings, and to advance scientific understanding in order to reduce impacts of volcanic eruptions. Communicating the results of our work to the public, emergency managers, and the scientific community is another important aspect of our mission.

The HVO facilities at Uēkahuna Bluff within Hawai‘i Volcanoes National Park were evacuated during the 2018 eruption. The main building on the bluff was damaged and we are currently operating out of temporary facilities until new until new buildings are constructed. Current plans call for a new primary USGS science center facility to be built in Hilo, as well as a smaller field station within Hawai‘i Volcanoes National Park. We hope that these new facilities come online within the next several years. Besides working out of temporary facilities, at the present time most of us are also teleworking when we’re not doing fieldwork.

Volcano Awareness Month was actually initiated back in 2010, primarily from the efforts of Janet Babb. Janet retired from HVO this past March, but Volcano Awareness Month lives on and has grown over the years. Activities typically include presentations by HVO staff given in-person at community centers throughout the Big Island, as well as HVO-led field trips. However, Volcano Awareness Month routine is very different this year.

First and foremost, all of our talks and even our field trips are virtual this year, instead of in-person. And this is because of the ongoing COVID-19 pandemic. So, we miss interacting with the community directly and we hope to do so again in the future. But for this year right now, we hope you find these HVO presentations enjoyable and informative.

Second, HVO staff have also been pretty busy responding to the current Kīlauea eruption that began on the evening of December 20, 2020, and which continues to feed a lava lake within Halema‘uma‘u. The response to this eruption compressed activities related to Volcano Awareness Month, down to Volcano Awareness Week! But we're getting these out now and we hope that that you will find them informative and interesting and we hope they provide some additional insights about what's happening with the current eruption, as well as in general about the past, present, and future of volcanic activity in Hawaii.

So we have three virtual talks planned, focusing on Kīlauea and Mauna Loa volcanoes, recorded conference presentations from December's American Geophysical Union conference, and we even have a virtual hike up at Kīlauea summit with Don Swanson. The hike with Don was always one of the highlights of Volcano Awareness Month and so this this virtual field trip, made possible thanks to Don and the recording by Katie Mulliken, is not to be missed. So, without further ado, let's start the festivities with this roughly one hour-long presentation about what's happening at Kīlauea Volcano. And I will turn it over to my fellow HVO colleagues to give you updates on the geology, the gas geochemistry, the ground deformation in the seismology. Mahalo.

Matt Patrick, geologist

My name is Matthew Patrick I'm a geologist at Hawaiian Volcano Observatory, and I'll be talking about some of the geologic observations of the ongoing summit eruption at Kīlauea that HVO has been making. The eruption has been going on about a month now.

This is a view of Kīlauea caldera and in the southwest corner we have Halema‘uma‘u crater and this is where the active lava lake has been. And this thermal map we'll be talking about later, what these colors represent.

It's important to realize that if you go back just three years ago, Halema‘uma‘u looked very different. This is before the very large eruption that we had in 2018. Before 2018, we had Halema‘uma‘u crater here—it's very circular, about six tenths of a mile across, pretty shallow, just 80 to 90 yards deep, and we had this lava lake that had been active for about a decade.

But then in 2018, we had this very large eruption on the lower flank of the volcano, on the Lower East Rift Zone, that drained magma from the summit magma chamber at a very high rate, and it caused the caldera floor and the floor of Halema‘uma‘u to collapse. And so, this is what it looked like after that. So you can see big changes at the summit here, the floor of Halema‘uma‘u collapsed, dropped more than 500 yards, a really significant distance and you can see big changes to the topography of the other parts of the caldera floor.

And what's also really interesting is in summer of 2019, we started to see water seep into that very deep pit. And that water Lake, which was really unprecedented for the past 200 years, was there right up until the current eruption. So I think the other talks will mention some of the activity that happened before the eruption, but at least on the surface, there really wasn't any change, any detectable change in say the temperature of the water lake or hot steam cracks appearing, let's say. There really wasn't any indication of that, so the magma came up to the surface pretty quick.

For me personally, the first indication that I got of the eruption was an automated alert on my smartphone, because we have this thermal camera that's running and it has an algorithm that detects anomalously high temperatures and I got an alert at dinnertime saying, hey, there could be lava, as you can see here. In this case, the computer was actually right so then we all, obviously, headed out in the field to start our work.

HVO geologists got to Jaggar Museum overlook about 10:30 [p.m. HST]. And what we could see was this enormous, just towering steam plume. It was pretty obvious that this was that water lake being boiled off, presumably by lava that was pouring into the bottom of the crater.  This steam plume was really impressive and actually somewhat similarly, we happened to be down in the 2018 Lower East rift zone eruption when we saw green lake in Kapoho crater boil off—another towering steam plume. But it's important to realize that that water lake was quite large, it boiled off in just about an hour and a half.

On the first night around 11 [p.m. HST], we got to the western caldera rim and this is what we saw. This was the first view in Halema‘uma‘u. And we can see here numerous fissures, fountains that were active and they were all pouring lava into the bottom of the crater. The water lake is gone at this point, it's about 11 p.m. [HST]. And what we have is the development of a lava lake.

This is a closer view of that dominant fountaining source on the north side of the crater. It's about 50 yards high. You can see it's producing this really vigorous cascade of lava that's just pouring and plunging into the lake. So at first light, we flew and were able to get the first daytime views of this eruption. And you can see the lava is filling in the bottom of the crater but then there's also this island. Closer later looks of this island seemed to reveal that this was kind of ejecta that may have been formed in the initial stages when lava was pouring into the water lake and creating maybe small explosions, but still we don't have hand samples or close views of the lake so its origin is still a little bit enigmatic. But you can see on this first day, first morning, we can see lava from the fountains pouring into the lake and filling in the bottom of the crater.

So this is a time-lapse taken from the thermal camera looking in Halema‘uma‘u. It starts off with the water lake here, and we'll see the whole month of the eruption just in this sequence. We're going to start it. There is the start of the lava lake and you can see it rises and fills the bottom very quickly, we have this fountain on the north side and then that dies off and the fountaining switches to the western fissure here. Throughout this time you can see this island, this cold island, is kind of shifting around, presumably carried by the currents in the lake. And you also see these minor islands that are active in the east part of the lake. And I should say that we're looking towards the east. So, this area here at the top of the image is the east and the bottom of the image is the west. And then you can see around January, 8, the eastern side of the lake starts to be kind of abandoned or starts to crust over and solidify, and the active lava on the surface is really just limited to the western part of the lake. Watch that again. So here we have this rapid placement of the lava lake, we have this northern fissure that's active, we have this island that's moving around in the currents, then we have this shift to the western fissure here at the bottom of the image. And then we'll start to see the eastern side of the lake start to solidify. That happens around the eighth of January. Then we have active lava that's more or less limited to the western part of the lake here.

So, that's kind of the state of what we have now and in the past week or so we've seen some minor changes in the vent activity at the western fissure, which is the active vent area. We see occasional small collapses that can trigger minor switches in the vent location or crusting over of the channel, but overall relatively minor. The western fissure remains active.

One of the things that we track when we go out is the elevation of the lava lake. And this is important because we know the topography of Halema‘uma‘u crater before the eruption. By comparing the elevation of the lake to the pre-eruption topography, we can figure out the volume and also the eruption rates. We use a laser rangefinder for that. Anyway, this is the results of all that data that HVO geologists have collected over the past month. This is the depth of the lake in meters so roughly yards and you can see the rapid rise or filling of the lake in the initial days and then it kind of slows down. We've been at this kind of slower rate in the past few weeks. Right now, the lake is roughly 200 meters deep, or about 650 feet deep, it's pretty deep. If you go online, you can find points of comparison. Here is the closest one I could find, is the Space Needle in Seattle. I've never been there, but it's about 184 meters [603 feet] so the lake is deeper than the Space Needle is tall. The volume is about 30 million cubic meters. That might not be necessarily very intuitive but for a point of comparison again, 10,000 Olympic swimming pools. And I've never been to the Great Pyramid of Giza but I've always imagined it is a place that's really enormous, and this lava lake is almost 13 times the volume of that. Pretty impressive.

So this is another view of that map of the summit caldera, and we have this is most recent thermal map that was made. And we have again in the southwest portion of the caldera we have Halema‘uma‘u crater, and we have this lava lake that's filling up a portion of that crater. This is a thermal map so the colors here, the blues to the yellows to the reds, give a sense of the temperature on the surface. The blues, you see this eastern portion here is cooler and it's actually solidified in the active lava here. The hotter temperatures, the hotter colors, are limited to the western side.

So as of today, January 20, the eruptive activity is stable. We have seen there's been a little bit of deflation over the past day and that's associated with a slight decrease in the vigor of the eruption. We've seen this pattern before. We've seen how, when we have these small deflation phases, they’re followed by inflation. So, the eruptive activity can then pick up again. It'll be interesting to see how eruption develops over the next few days with this kind of deflation inflation cycle. But of course, the bigger question is how will the eruption play out in the long run? Overall, of course, Halema‘uma‘u is the home of Pele and this is very fitting because it has such a long history of lava-lake activity. There were decades, well almost 100 years, of lava-lake activity in the 1800s and early 1900s. This is an example of one of the beautiful perched lava lakes formed in Halema‘uma‘u, and of course we had 10 years of continuous lava lake activity from 2008 to 2018. But what we've seen is that these previous eruptions in Halema‘uma‘u there's a wide range in eruption durations. They can last for a day or they can last for decades. So, it's still unclear how long this eruption will last. There's no indication of it stopping, but it doesn't necessarily have to last as long as these previous eruptions. In any case, we're watching this very closely, we're out in the field on a daily basis. We have a very robust monitoring network that's keeping a very close eye on the eruption. Thank you.

Tricia Nadeau, gas geochemist

Hi everyone, I’m Tricia Nadeau, and I will be giving you a bit of an update on what the gases have been doing during this recent Kīlauea eruption. Before we get to what it's doing now, I’ll give you a little bit of background on what the gas was doing before the eruption. As many of you might know already, SO2 emissions or sulfur dioxide, were very very low since the 2018 eruption. And that meant all eruptive sites. We were measuring about 30 tons a day at the summit, but sites on the East Rift Zone were below detection. And what that means is that magma was deep enough to keep that SO2 dissolved. So, just like a bottle of soda that you might open, we essentially had the cap on our magma chamber, so no bubbling/no gas is leaking out until the eruption.

We did also have this water lake that you can see on the right, and it is possible that some SO2 that was escaping from the magma ended up dissolved in the lake water so we couldn't measure it in the atmosphere. Now, people might also be wondering if we saw anything in the degassing before the eruption, that could have been a clue that an eruption was coming. And that's a fair question because you do see signals like that at many volcanoes around the world. And we've even seen it at Kīlauea in the past. This is sulfur dioxide emission right here for a lot of 2007. This is the lead up to the 2008 eruption. And you can see that sulfur emissions were pretty low and pretty stable at only a few 100 tons of SO2 per day until we hit December of 2007, when we started seeing this increase. Nothing was erupting here yet but we were seeing an increase. And then in the middle of March of 2008, that's when the eruption started. So here, seeing that increase of SO2 was a clue that there could have been an eruption coming, and it did come.

This time we didn't see that. This is a slightly different kind of unit. This is a SO2 concentration. This is measured at a site about a kilometer [about half a mile] downwind of Halema‘uma‘u and it measures about half an hour, every three hours. You can see—this is the day of the eruption—0, 0, 0, all zeros. The eruption happened right about 9:30 [p.m. HST], just after our nine o'clock sampling window. We didn't see any change, even though the eruption was about to start. You can see that the station definitely did measure more SO2 after that, once the eruption had started, but no precursors this time around. No SO2 showed up to clue us in that something was happening.

And now for gas emissions since the eruption started. This is back to SO2 emission rate again and this graph starts the day the eruption started. You can see right away, we were pretty high with SO2 emission rates—this is almost 40,000 tonnes per day of SO2. It did start to decrease right away. And for context here we sort of crossed through this zone where we had lava lake, what the previous lava lake level was. Early in that eruption, SO2 emissions around 2008 were close to 20,000 tonnes a day. We started higher than the previous lava lake, crossed down through that, and then most of the 2008 to 2018 lava lake averaged around 5000 tons per day. And we actually did, with this new eruption, see that for a while. We're a little bit lower than that right now, although there is variability. So we have this one point jumped back up to almost 5000, but our most recent point is 2500. So in general, we're slightly lower than emissions from the previous lava lake.

People may also be wondering about Pu‘u ‘Ō‘ō. We did go check on it. We took a helicopter out there on January 7 to make sure that there was no excess degassing out there, and there's not. SO2 remains below detection limits around Pu‘u ‘Ō‘ō.  These sort of rainbow dots are measurements from along our flight track. And if there was a significant degassing plume, you would see all of the red dots concentrated in one place, but you don't you see it. It's just noisy data, there's blues and reds and yellows all over the place. So that's telling us theres’s essentially no plume coming out of Pu‘u ‘Ō‘ō in terms of sulfur dioxide.

What is out there is a little bit of H2S, hydrogen sulfide, and human noses are actually more sensitive to hydrogen sulfide than they are to SO2. So even though there's just a tiny amount of that hydrogen sulfide, if the winds change and blow that gas toward nearby communities, people may smell a rotten egg smell. So that's not SO2, that’s H2S, and it's only under certain conditions.

We can also see SO2 emissions from space. TROPOMI is a satellite sensor that detects SO2 once a day. And you can see in this image from the day before the eruption, there's no plume. This is just background noise. Once we had the eruption, we see a pretty big plume on December 22, but already by the 25th—by Christmas—we were having a bit of a decrease, there's less of a plume. And since then, we've had even less it's certainly still detectable by satellite, but it is lower emissions than early in the eruption. It's showing the same decrease in emissions that we've been seeing from our ground-based measurements.

People who may visit the [Hawai‘i Volcanoes] National Park or live here on the Island of Hawai‘i may be wondering about gas hazards. And if you've lived here long enough you likely know about vog [volcanic air pollution]. So, the vog is back unfortunately, and it can be a hazard. But as I mentioned, the emission rates right now are actually a bit lower, just a little lower than that 2008 to 2018 lava lake level of emissions. And there's actually much less vog than there was during the 2018 eruption. That released far more SO2 than we're measuring right now. So, the vog is not as bad as during that eruption. If people are wondering more about vog, you can head to this website called the vog dashboard. And there you can get information from the Hawai‘i Department of Health about how the vog and the SO2 might affect your health. You can get forecasts about where the vog will go on any given day, and that's what this image on the right is showing. And you can also get real time air quality data if you're curious about whether the vog is near you at any given time.

I've talked a lot about just sulfur dioxide, but we can actually monitor other gases in some other ways. One of the ways we get a better picture of gas chemistry is by unoccupied aircraft system, or drones, as most people call them. We have permission from the National Park Service to do some of those gas measurement flights within the park. And this picture on the left is just showing sort of a slice through the plume, and the red is where we encountered sulfur dioxide. And I could have also just as easily put this profile showing where we encountered carbon dioxide or hydrogen sulfide. On the right is showing where the gas concentrations were highest when we flew actually in and over the erupting crater. That's a place that we cannot go ourselves, but that's where the drones come in handy—they can go places that we can’t, so we were able to measure the chemistry right in the erupting plume right close to the vent.

We can also get gas chemistry using what's called infrared spectroscopy. So there we don't have to go so close to the vent, we can just measure the gas that's in between our infrared source, which, when there's an eruption we can use lava as our infrared source, and our spectrometer. We can also just physically go grab some of the gas and send it off to the lab to analyze the chemistry. So again, we can't go in the erupting crater to do any of this, but there are some degassing sites in public areas in the National Park—at Sulphur Banks [Ha‘akulamanu]. We do this sampling with this bottle to sample the gases every three months anyway and we added some extra sampling because we had an eruption.

Now, we can learn things about the eruption by looking at the gas chemistry and the combinations of gases. Both of our multi gas sensors, meaning our ground base station and our drone-mounted multi gas sensors, plus that infrared spectroscopy, all of those methods are telling us the same thing. There's a low ratio of carbon dioxide to sulfur dioxide. Sulfur dioxide is dominating the degassing during this eruption. And what that means is that this lava that's erupting right now sat around in a magma chamber for a while before it erupted. So, like in this top panel, if we had brand new magma coming right out from deep in the mantle, all of its dissolved carbon dioxide and sulfur dioxide would all come out during this one eruption and that would mean there's a higher proportion of carbon dioxide, or a higher C to S ratio. But we don't see that. We're actually down in the second picture here, where the magma comes up, sits in a magma chamber for a while, and while it's sitting there, it is able to lose or degas some of that carbon dioxide. It just comes up without erupting, it leaks out through cracks in the ground. And then once it finally does erupt, we end up with that sulfur dioxide coming out. So that's what we see right now. The gas chemistry is telling us that the lava that's erupted so far in this eruption did not come quickly from deep in the mantle, this is magma that was sitting in a magma chamber for a while so it's sort of pre-degassed. It has lost its carbon dioxide already. So that's one of the things that gas chemistry has shown us.

We still have a lot of data to look at and interpret and understand, and we'll certainly keep making measurements, both for these chemistry issues that we can figure out, and to make sure we're keeping an eye on hazards for all of you in the public. Thanks for listening.

Ingrid Johanson, geophysicist

My name is, Ingrid Johanson, I’m a geophysicist with the Hawaiian Volcano Observatory, and I'm going to talk about deformation during the December 2020 eruption at Kīlauea volcano and show you some of the data that we collected during that time.

First, I want to introduce you to two of the data types that I'm going to show. These are the primary ways in which we monitor the volcano in real time at least via deformation measurements. The first is continuous GPS [Global Positioning System], the GPS antenna is underneath this grey dome here. It's fixed firmly to a monument, which is itself fixed firmly to the ground. It operates, not too dissimilarly from the GPS in your phone or in your car, but instead of measuring the position of something that's freely moving around, we're very precisely tracking the change of position of the ground, to which this antenna is attached. The other instrument is a borehole tiltmeter, which is this long cylinder here. Inside the cylinder are two bubble levels. One oriented north-south, the other oriented east-west, so not too different from bubble levels you might have used around your own house, except that they're extremely sensitive—capable of measuring tilt down to a fraction of a microradian. And for comparison one micr radian is about 50,000,000th of a degree, so very very small amounts of tilt. These cylinders are lowered down into a hole where they're kept a little bit protected from temperature changes and other noise sources at the surface.

When magma starts to move into a reservoir, it bulges the ground above it. This has the effect of tilting the surface outward and moving points on the ground up and outward from the magma reservoir. So this is what we're measuring and how we're interpreting these data. When an eruption happens, it taps into that magma reservoir, moves material out of it and we see the opposite type of motion. So now, the ground is moving downward on top of the magma reservoir. The ground is tilting inwards and points on the surface are moving down and inwards towards the magma reservoir.

Here we're now looking at three tiltmeter plots for tiltmeters around the summit—UWE, SDH, and IKI. This is a map of Kīlauea’s summit, showing the locations of these tiltmeters—here's UWE at Uēkahuna Vault,  SDH at Sand Hill, and IKI near Kīlauea Iki. These plots are showing 12 hours of data around the onset of the December 20 eruption. You'll see two lines here, a blue line and a green line. And as I mentioned before, the tiltmeters have two bubble levels—a north-south and east-west, but we often find it convenient to mathematically rotate those into different azimuths in order to emphasize different signals. So for example, the blue line here for UWE has been rotated to 310 degrees, and this emphasizes deformation from the shallow Halema‘uma‘u reservoir. This direction has been chosen specifically so that downward motion of this blue line is consistent with deflationary type motion, and upward movement of the line would be consistent with inflationary motion. And the same is true for SDH and IKI, even though they're rotated to different azimuths, those azimuths were chosen such that upward motion of the blue line is consistent with inflation and downwards is consistent with deflation of that shallow Halema‘uma‘u reservoir. If the source is different, then we can expect different patterns of tilt, that might not all resolve onto the blue line.

We first started seeing changes in tilt on December, 20, at about 8:30 p.m. [HST]. This was only an hour before the fissure opened at around 9:30 [p.m. HST]. So you can see about this period of one hour prior to the eruption, we saw a mix here of deflationary and inflationary motion, somewhat complicated pattern was probably caused by the opening of the fissures. After the onset of eruption, we see on all of our summit tiltmeters data that's very consistent just gradual steady deflation of the shallow Halema‘uma‘u reservoir. It's interesting to note that the changes here prior to the eruption were very modest—only a couple microradians. It was actually not enough to trip our tilt alarms, so that this was an event that happened with very little precursory deformation. It did trip other alarms, so [earthquake] swarm alarms and the thermal [camera] alarm that really alerted us to what was going on. You might be interested to know that this spike that you can see on several of these tiltmeters, this is when the magnitude. 4.4 earthquake on the south flank occurred. And what's happening here—these are really noise—what's happening is the shaking from that event really sets up sloshing in the bubble level.

In the days following the onset of the December 20 eruption, we continued to see steady deflationary motion. This plot is showing GPS positions for station CALM. CALM is located centrally on Kīlauea caldera, on what we call the downdropped block. This plot is showing its vertical motion, so you can see it moved very steadily downward following the onset of the eruption but then had a change in behavior on around December 26. This was when the north vent in Halema‘uma‘u crater was drowned by the lava lake. After this time period, we saw a little bit of uplift, but overall deformation was much lower amplitude following December 26 than it was in the days before.

A nice time series like this, we can start to model the decay using different kinds of curves. In this case, I fit an exponential curve to this time series. We can do this for all of the GPS stations around the summit region and come up with a sense of the spatial pattern of this deflationary component, which is what I'm showing in this plot. So, these arrows are representing the amplitude of an exponential curve fit to the time series for all these GPS stations in Kīlauea summit region. The size of the arrow corresponds with the magnitude of the exponential—how much deformation happened and here's the key here, and the direction indicates the direction that this exponential decay was oriented towards. So as you can see, the vectors here at the summit are all pointing inwards, very consistent with deflation of a source here in the summit, which could very well be the shallow Halema‘uma‘u source. There's a little bit of asymmetry here in the sizes of the arrows, which might indicate something more complicated than just a simple sphere here.

One of the interesting observations from this eruption was the observation of contraction out into the East Rift Zone. Here, I've expanded the size of the map to show GPS stations out around the East Rift. So you can see some inward direction motion appear around Makaopuhi crater, and also some motion here near Pu‘u ‘Ō‘ō, where stations are being drawn up-rift. This is a unique observation that hasn't been observed in other events that have also caused deflation at Kīlauea summit, with the exception of 2018, where there was deformation all over the volcano.

What this might mean is that magma may have actually been drawn backwards, out of rift into the summit. Typically what happens is that magma comes first up to the summit and then it's transported down the rift, but this might be telling us that in some cases in fact magma can flow backwards and be drawn from the rift back into the summit, which would be an interesting and unique observation. I should point out that no contraction or inflationary type motions were observed down-rift of Pu‘u ‘Ō‘ō, including at the site of the 2018 eruption. So, these data—GPS stations in these areas—didn't show anything that looked clearly related to the December 20 eruption.

Now I'm looking at a tilt plot again. This is again the UWE tiltmeter, which is at Uēkahuna vault not that far from Jaggar Museum. Here we're looking at two months of tilt, in order to put the eruption of December 20 in context of what happened after and what happened before. So, you can see here, December 20, in the days after, until the drowning of the north vent, there was about 50 microradians here of deflationary motion. Since December 26, we've seen modest inflation and deflation but much lower rates overall. Prior to December 20, we saw a lot of these events where there'd be deflation and inflation. We call these DI events—deflation inflation events—and they are extremely common at Kīlauea’s summit. So, in fact, these DI events are part of the background activity at Kīlauea. But the most prominent signal prior to December 20 was this inflationary signal on December 2. This was associated with a small magma intrusion in the southern portion of Kīlauea caldera. It's worth pointing out that this intrusion happened in a different part of the caldera than the eruption; it's unlikely that the eruption is actually tapping into the magma from the intrusion. Instead, it's more likely that both the intrusion and the eruption are being fed from a slightly deeper, more central reservoir. The size of this tilt excursion as you can see is about 20 microradians. Both of these events are dwarfed by the 2018 eruption and collapse signals. During that time period, we recorded tilt changes over three months of on the order of 600 microradians. Still, compared to what happened in 2018, which was a century's-level event, these are relatively modest.

Now, we're zooming out to the past year of tilt data. Tilt data from tilt meter UWE at the top, and then vertical motion from GPS stations CALM at the bottom. You can see in the tilt record, the repeated DI events, which are very common at summit. You can also start to see this steady slow inflationary deformation. This actually started not long after the end of 2018 eruption. This signal has been very typical of the summit in the years since. You can see that here at CALM as well where the station was slowly moving upwards throughout 2020. This sort of gives you an idea of what a departure both the intrusion and the eruption were from the pattern that had been established in the previous year. The sizes of the motions that we have seen in the last month and a half can maybe be compared to tilt changes that were observed in the 60s and 70s. In the era before the Pu‘u ‘Ō‘ō eruption started, there are records at multiple locations throughout Kīleaua Volcano that would cause deflation at the summit. This record here is from a water tube tiltmeter. So, this is the era of before borehole tiltmeters or GPS; tilt during this time was recorded using an instrument called a watertube tiltmeter. And those of you who have been to Jaggar Museum may remember that this was on display there. This was read manually once per day, which is what gives us this nice continuous two-decade-long record. However, you can see here many instances—the scale goes from minus 400 to 400—of 100 microrad 50 microrad type motions, both deflationary and sometimes inflationary. What this means is that it's not unreasonable to think that as we go into the future we may see more events similar to the eruption on December 20. We're still learning what this new regime at Kīlauea Volcano is going to be like and this era of the 60s and 70s might be what we're moving into.

To summarize—throughout the December eruption, we saw deformation consistent with that summit reservoir deflating, magma moving out and feeding the eruption in Halema‘uma‘u crater. We also observed contraction in nearby portions of the East Rift Zone. And this was a unique observation that suggested that magma might have actually been flowing backwards towards the summit. Overall, the levels of deformation were low compared to 2018, but not too different from what was observed in the 60s and 70s. So we're continuing to learn how Kīlauea Volcano is different, and similar to the Pu‘u ‘Ō‘ō era, and very much looking back at previous times in Kīlauea’s history to learn what we might be moving into. Thanks.

Peter Dotray, seismologist

My name is Peter Dotray, and I'm a seismologist here at the Hawaiian Volcano Observatory. I'm here today to talk to you about the most recent seismic activity, so the activity over the past month, and we'll focus on some of the events that led up to and occurred during the December 20 Kīlauea summit eruption.

So first we'll take a look at this island map of the earthquake locations, and you can see they're colored based on depths and sized based on their magnitudes. And you can really see some of these seismogenic regions that we're used to seeing being very active continue to be quite active over the past month. So here we have the East Rift/South flank activity that's been occurring. And then we can focus on Mauna Loa and the Northwest flank and Ka‘ōiki fault system continues to stay very active. And then of course is the deep Pāhala activity that has been very prevalent over the past couple of years; we'll dig into that a little bit as well. Then, we'll focus on this activity at Kīlauea summit. And you can see here it looks very quiet and we'll talk about what we're seeing there and maybe why it's been quiet over this past month period.

Over here to the left and we have a histogram. This is a two year plot—a bar graph—that shows you the number of earthquakes per week. So, each bar is a single week and it's showing you the number of earthquakes. Up here, we had a week of island-wide seismicity of over 1000 counts and then the next week we dropped down below 600. We'll take a look at a lot of other histograms as well.

These histograms are actually focused just on Kīlauea summit. This is activity at Kīlauea summit over the past two years, and you can see these weekly counts really fluctuate and Kīlauea is very dynamic so it's expected we have weeks of swarms, and the next week will be event counts of under 100 a week.

October 20 to January 18 activity—but we can see there's a few spikes here—so now we're actually looking at earthquakes per day so each bar is a single day. And you can see there's a few spikes here in late October, late November, and then this little spike with a drop off in mid-December. We'll take a look at those independent.

That first little spike—here's a video of that activity—and you'll notice there's a couple of episodes, a lot of earthquakes that focused on these lower Ka‘ōiki faults. And we call these the Nāmanakanipaio swarms. A swarm of earthquakes is just a group of earthquakes that occur very closely in space and time.

The Nāmakanipaio swarms on this density plot, they occur very closely to Nāmakanipaio Campground. Here this density plot is showing you different squares of concentrations of earthquakes in that square, so your cooler colors are going to be lower concentrations while your warmer colors are higher concentrations. So you can see we have some of these grids of these warm dark reds, which are very high counts of earthquakes. So most of that swarm is occurring right there on these lower Ka‘ōiki faults. And again, this is that first spike we're looking at these daily counts.

If we take a different look at the same swarm. Now we're looking at this histogram which is earthquakes per hour over this two-day period. And you can see it really flared up right after midnight. It produced the highest rate of earthquakes at 25 earthquakes in an hour before it really quieted down, and then picked up for its second episode. And if we come over here and look at this map—this map is now showing you colors based on time—your cooler colors actually happened early on October 22 while your warmer colors were more on October 24 and sized based on magnitudes again.

 You can see this large earthquake right here, that was the magnitude 3.5. And this map has these depth panels, so these longitudinal and latitudinal depth panels, and you can think of those as we took a slice out of this map, and we're able to look North at the sort of subsurface activity, we would see where these events are occurring, which is a great way of looking where the depths are clustering. You can see here, these are the same events all looking at different views, and the latitude again, we're going to cut this way and look West, and this is what you can see. You can see these events all really clustered in this two to four kilometer [1 to 2 miles] depths. And this is in regards to sea level, so 2-4 kilometers [1 to 2 miles] below sea level. You can see both of these episodes, very concentrated right there at these depths and on these Ka‘ōiki faults. We expect these events [that] there's some stress redistributions between the Kīlauea Volcano and Mauna Loa volcano. Two volcanoes pressed up against each other produce all these faults, and that activity occurs there relatively often.

And now we'll jump into this second spike that we were looking at, which is more sort of focused in the Kīlauea caldera and upper East Rift. You'll see a lot of activity in this upper East Rift connector. You see a little flare there and some activity, and then it'll sort of focus on the southeastern part of the caldera before a few large events occur on this upper East Rift connector. If we take that same look we were looking at the Nāmakanipaio swarms and look at it for these caldera swarms, we’re going to look at this density plot again. And there's a slightly longer time span November 29 to December 3, but we can see again some of these darker colors are occurring where most of the earthquakes were concentrated, which was the southeastern part of the caldera and this western part of the caldera. But with some blues and greens, these moderate colors, forming on the down-dropped block, so this shelf of the caldera that fell during the 2018 eruption and a lot of activity up there in that upper East Rift connector as we saw in that video.

And now we'll go take another look at these histograms—these hourly histograms—to see this swarm really had two episodes as well: this first episode flares up and it peaked out about 17 earthquakes in an hour. And then it quieted down, and then it picked up again, and this time they topped out at 23 earthquakes in an hour before it really fell off. And again, these are colored based on the time so cooler colors are earlier, warmers later, and their sized based on magnitude. You have this large 3.1 event right here. And this map is interesting because you see the colors are actually quite separate. You can see these blue, these early episodes happen in the downdropped block in the western part of the caldera before you get these oranges and yellows in the upper East Rift connector. And then finally it moved into these darker reds, up here in the southeastern part of the caldera, and we'll take a look at these longitudinal and latitudinal depth panels. Again, if we cross cut and look in, you can see the depths are actually quite a bit more shallow, we're looking at about zero to one and a half to two kilometers [around one mile] below sea level. And these swarms really had different implications with the shallow depths and them occurring right under the caldera, along with some geodetic signals we're seeing with this second episode especially. These are believed more to be results of some shallow magma intrusions under the volcano, which is very different from those Nāmakanipaio swarms which were really more just stress redistribution on some faults. These had some more magmatic implications.

And then finally, about a month, not quite a month later, we have this eruption activity. So this is a longer time span video, you're going to see it builds up. There's just some micro seismicity, really nothing obvious until the day of the eruption. We get a little flare, right there, and then we get this large south flank event that I think most of us felt on the east side of the island. And then a very interesting part of this video actually a few days after the eruption began, activity got very very quiet. You see occasional microseismic events popping out but for the most part, time is still running and the map looks empty. And we'll get into that a little bit—of why we're seeing such little earthquakes at the summit and what we are seeing since the eruption began.

So again, we'll take a look at this final little spike and the drop off. The eruption began on the 20th, through the night and early December 21. And you can see on this density plot, you have a very different scale—only one to four mostly light blues with just a couple of these warm colors occurring on the south part of the caldera on this sort of ring fault, and still some upper east rift connector activity as well. Now I'm actually going to show a slightly different view, so here we're looking at waveforms from different stations which are highlighted on this map to get nice coverage around the caldera. And this map is still the earthquakes colored based on time, sized based on magnitude. And this plot down here is slightly different because we're showing depth in regard to time so this is no longer a cross cutting view, simply where the depths were occurring over time. And you can see this red dotted line is when lava was seen at the surface when it broke the surface, and up to. Before that, and even after that, we have this slight shallowing of earthquake activity, which would make sense. Even after lava breaks the surface, the conduit and the path that the magma is taking is still trying to establish itself and get a stable path that it can pour lava out of. We see some of this shallow later as well.

Now we'll focus on some of these waveforms. But I actually want to shift this view to spectrogram. So these are the same stations, the same time, except now we're looking at the frequency content. You can see some of these darker colors are the events, the darker reds, and the darker the red you see are generally the stronger the events. You can see this hour leading up to the eruption, we have these spikes of broadband. They have low frequencies and up to 20–25, high frequencies. These broad signals that are really signature of earthquakes—rock breaking, rock fracturing, and you can see some of these high frequencies attenuate over time, just very classic for any sort of volcano-tectonic earthquake. You can see these are occurring every minute, every 30 seconds, leading up to about 10 minutes before lava broke the surface. Then you can clearly see the sort of volcano-tectonic events start coming in more rapidly and more strongly and becoming not even single events anymore, it's almost multiplets. Many events stacked on top of each other. And then the lava breaks the surface about 10 minutes after that activity picks up, then even 15–20 minutes after we had that strong vt [volcano-tectonic] multiplets occurring before things really got sort of mixed together. You still see in this time period about 15 minutes after lava broke the surface, you can see these pulsing vt—volcano tectonic multiplets on top of this band of tremor that began.

We had geologists on the ground at that point and they were seeing different events pop up, they weren't just one event where everything came out. There's different events, and the path is really trying to establish itself. The magma needs to establish a nice least/low resistance path to reach the surface, and then you can see about 40 minutes after it was first seen on the surface, it really did establish its path. You can see that nicely because you have less of this pulsing broadband sort of rock-breaking activity, and more of this steady low frequency sort of humming, this tremor, which is a signature signal you expect with material pouring out or liquid movement and here we have an open event that lava was pouring out of/it created.

Then we can focus on this event that occurred about an hour after lava reached to surface that most of us felt. I remember being slightly concerned when we first felt the shaking of this event. But then we saw that it was a south flank event, which is expected and occurs often. This event—you can see this map it shows where the felt/did-you-feel-it reports were submitted from—felt very strongly on the east side of the island, really on the Big Island, in Maui, and Moloka‘i. It had a maximum Mercalli intensity of four which indicates light shaking and really no damage, and it had about 620 did you feel it, or felt reports, It occurred at 6.3 kilometers [about 4 miles] depth and that, along with the sort of a shallow dipping fault plane, really indicate it occurred on the decollement, which is the detachment fault of the islands sitting on top of the ocean floor. We get a lot of events there. Here, if we sort of zoom in and focus on the East Rift, you can see a lot of these events occurring. These are now colored based on depths, and they're occurring from five to 13 kilometers [three to eight miles] below the surface. That’s about what we would expect for these decollement events, and you can see the rift is pretty clear right here—the East Rift of Kīlauea—we have events that are happening south of that, which is a pretty clear indicator they're not migrating through the rift. These are really south flank detachment faulting events. Here if we focus and look at the lower East Rift, you can see it is very quiet. There’s really been no migrating activity out there, a few microseismic events, a couple of moderately sized events, which we had a handful of felt reports for, but overall very small and very quiet. And then over here you can see the histogram of weekly counts. It stayed pretty consistent in terms of recent activity, with Kīlauea summit being as quiet as it is, it's really just mostly south flank activity we’re seeing over the past month.

And then finally—the Pāhala seismicity. It catches a lot of attention, including ours. We’re focused on this area because the activity has really picked up. But the activity stays at these 25–40 kilometers [15 to 25 miles] depths. You see some shallow activity up here but it’s very separate activity. You don't really see any migrating or shallowing right under Pāhala. It's really just these deep events, which past studies have linked that to deep magma upwelling, maybe where it comes into the volcanic edifice—the Big Island—where it first enters from the sort of upper mantle area to the crust.  You can read more about that in this “Volcano Watch” that was written in 2019; it will talk slightly more about that, but again this activity has been observed for decades, and it did pick up in August 2019, but it stayed pretty consistent since that time.

Thank you very much. If you have questions, please feel free to email and we'll get back to you as soon as possible. Stay safe. Thank you.

David Phillips, acting Scientist-in-Charge

Hello again. I hope you enjoyed that presentation about what's happening at Kīlauea Volcano. Just reminder that activity is ongoing and things likely evolved from when this presentation was recorded in mid-January until the time that you're watching it. So please visit the HVO website for the latest information about the activity Kīlauea. There are regular updates on the activity, we have photo and video chronologies for some unique perspectives on the activity and the interpretations, as well as live webcam feeds so you can see what things are like in real time. I would also like to say that at this time, all activity from the current eruption is taking place within Hawai‘i Volcanoes National Park. The lava lake itself is not currently visible for many safe viewing locations within the Park. So please carefully follow the Park’s guidelines to have the best and safest experience that you can. HVO is performing our critical monitoring activities within the closed area of the park. And we're doing this with permission and in close collaboration with Park authorities. HVO field crews are also equipped with a full complement of specialized personal safety equipment, and communications equipment while we perform the volcano monitoring work as part of HVO’s mission.  Again, I would like to acknowledge Janet Babb for initiating Volcano Awareness Month, and we wish her a very happy and healthy retirement. I would also like to acknowledge Tina Neal, who served as HVO Scientist-in-Charge up until this past June. She was in charge of HVO and the response throughout the dramatic events of 2018, and Tina sends her aloha from the Alaskan Volcano Observatory, where she is now. And finally, I'd like to acknowledge the tremendous efforts and talents of Katie Mulliken, who organized and made this year’s HVO Volcano Awareness Month possible, so thank you very much Katie. A lot of work goes into these, especially in the middle of the pandemic and in the middle of an eruption, so mahalo, Katie. Happy Volcano Awareness Month to everyone. Happy New Year, in general. Please be safe. Take care and stay aware. Aloha.