What’s happening at Kīlauea Volcano’s summit?

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Detailed Description

Kīlauea Volcano's summit has been in an eruptive pause since the 2018 events ended over a year ago. Nevertheless, it remains a dynamic place. Ongoing inflation and seismicity indicate that the summit magma chamber is gradually recharging. A water lake, unprecedented in the written historical record, appeared at the bottom of Halema‘uma‘u in late July 2019 and has steadily risen. What are the potential hazards at Kīlauea’s summit? Could explosive activity return? What is known about the water lake? How is it monitored? USGS Hawaiian Volcano Observatory geologists Matt Patrick and Tricia Nadeau answer these questions and more in this Volcano Awareness Month talk presented on January 14, 2020. Volcano Awareness Month is spearheaded by the USGS–Hawaiian Volcano Observatory, in cooperation with Hawai‘i Volcanoes National Park, and provides informative and engaging public programs about the science and hazards of Hawaiian volcanoes. Photo caption: Crater lake within Halema‘uma‘u at the summit of Kīlauea Volcano as it appeared on October 19, 2019. USGS photo by M. Patrick.
 

Details

Image Dimensions: 1600 x 1200

Date Taken:

Length: 00:49:27

Location Taken: HI, US

Video Credits

Video production: Katherine Mulliken, Geologist, Hawaiian Volcano Observatory, kmulliken@usgs.gov
 

Transcript

[Speaker: Matt Patrick, USGS Hawaiian Volcano Observatory]

 

I'm Matt Patrick. I work for the Hawaiian Volcano Observatory. Tricia Nadeau is here, as well. We'll be going back and forth talking about different aspects of the summit activity. We're here to give a summary of what's been happening and the recent changes of the past year.

 

This is a recent view from the western caldera rim showing Halema‘uma‘u and the sections of the caldera floor that dropped during 2018 and other levels of the caldera floor here. This water pond that's a new feature over the past several months, since summer. To give a basic overview of Kīlauea Volcano, this is probably review for most of you…

 

Kīlauea is on the southeast portion of the Island of Hawaiʻi, and the summit caldera is a center of much of the historic activity. Kīlauea has two rift zones, the Southwest Rift Zone, which is not labelled here. The East Rift Zone, which extends out along here. There's been a large amount of historical activity, including a lot of recent activity, [there] including the Pu‘u ‘Ō‘ō eruption from 1983 to 2018, and the big 2018 eruption occurred on the lower flank of the volcano on the lower East Rift Zone. The lower East Rift Zone contributed to, or was associated with, the collapse of a portion of the caldera floor here.

This is a recent view of the summit. Here we are at the [NPS] Visitor Center, and here's the caldera, a couple miles across. We have this new scarp, this new cliff, in the center of the caldera, and that formed during the subsidence of this portion of the caldera floor during 2018. And we have Halema‘uma‘u in the southwest portion of the caldera that enlarged and deepened during the 2018 activity.

Halema‘uma‘u is … we're going to be talking a lot about it.  It's important to recognize that this is a sacred place. The Park [Hawaiʻi Volcanoes National Park] has a lot of great background on the cultural context of the summit and Halema‘uma‘u, in particular. It’s the home of Pele. This is related to the fact that Halema‘uma‘u has been a center of activity for many years.

There was a lava lake activity through much of the 1800s, into the early 1900s. Nearly continuous lava lake activity.

The lava lake activity at the summit in Halema‘uma‘u was a big reason that HVO was founded in 1912. The reason that it started was to make direct, close observations of continuous volcanic activity, to try to better understand volcanic hazards and to make better forecasts.

 

That lava lake activity from the 1800s—basically a century of lava lake activities from the 1800s into the early 1900s—came to an abrupt end in 1924, when there was explosive activity that widened the crater, and ended that 100 years of lava lake activity.

 

Through the rest of the 20th century, there was still summit activity, but it was sporadic and episodic, usually short-lived—days or weeks. The last [summit] eruption of the 20th century was in 1982. Then there was 25 years of eruptive pause at the summit.

 

Lava lake activity returned in 2008, and that lava lake activity lasted for 10 years.

How many of you stood at Jaggar [Museum] and watched the lava lake? Most of you. Many times, you could just see the glow because the lake was a little bit too low to see directly from Jaggar. But there were numerous times, particularly in 2016, when the lake was high enough, that you could see it on many days. This was a really spectacular phase of activity on Kīlauea. There are not many persistent lava lakes on Earth. This was one that was very accessible. It provided a lot of new insight into lava lake behavior.

 

That came to an abrupt end in 2018. So, let's talk about the 2018 activity.

There was a large eruption, lava flow eruption on the lower flank of the volcano, on the lower East Rift Zone. That eruption caused magma to drain from the summit magma chamber. That removed support from the roof of the chamber and portions of the caldera floor dropped, causing enlargement of Halema‘uma‘u and also subsidence of the broader area around Halema‘uma‘u.

That 2018 activity ended the long-lived Pu‘u ‘Ō‘ō eruption. Thirty-five years of activity there ended very abruptly. It also ended that 10-year-long lava lake that we had at the summit. There had been previous collapses at the summit, a handful in the 1800s, but the one that occurred in 2018 was the largest one that we know of that’s been recorded in the past 200 years.

 
Unfortunately, the lower East Rift Zone eruption has distinction of being the most destructive eruption in Hawaii in the past 200 years. Over 700 structures were destroyed.

 

This gives you an idea of what the lower East Rift Zone eruption looked like. This is the dominant vent, fissure 8. You can get a sense, just from the size of this channel, and the rate that lava was flowing through it, that these were very high eruption rates. Eruption rates 50 to 100 times greater than what we observed during the previous years of Pu‘u ‘Ō‘ō activity.

That high eruption rate was draining magma from the summit magma chamber, causing the floor of the caldera to drop. This is a time-lapse camera that we had near Keanakākoʻi, looking north, and showing the drop of this section. This used to be flush with this, and it dropped over 100 yards. Other sections around Halema‘uma‘u dropped much more.

To give you a sense of the topographic changes at the summit, this is what the caldera looked like before the 2018 eruption. This was taken in early 2018. Here, we have the main caldera floor. We have Halema‘uma‘u here, about a kilometer or 0.6 mile in diameter, and have a lava lake a few hundred yards across. These were recent overflows from 2015.

After the eruption, this is what the caldera looked like.  So, we have this section, this is down-dropped block, that sank in a piston-like manner. And we had an enlargement and deepening of Halema‘uma‘u.

We'll go back and forth here so you can get a sense of what changed. Dramatic changes at the summit.

Now, Tricia is going to talk a little bit about sulfur dioxide.

 

[Speaker: Patricia Nadeau, USGS Hawaiian Volcano Observatory]

Matt talked about lava and the physical changes that we've seen. But, especially if you live here or visit the park, you're also concerned about what the gases are doing at any given time. Let's start big picture with the SO2 [sulfur dioxide] emissions by year.

 

Here's a plot of SO2 emission rates since that type of measurement started, which was in the late 70s. Here's where Pu‘u ‘Ō‘ō started erupting in 1983, and here's when that summit eruption, that lava lake began. This really high peak over here, that’s the 2018 eruption. If we look at this Pu‘u ‘Ō‘ō era, we had about one megatonne per year, which is 1 million tonnes of sulfur dioxide per year. That's this plateau here. There are some variations, but it was relatively steady for a long time. Then that lava lake opened up at the summit and things jumped, especially early on. It did tail off a little bit, but it was still pretty high, at least 2 million tonnes a year of sulfur dioxide that was being emitted.

Then we hit 2018, 10 million tonnes or more of SO2 came out. Remember, the eruption wasn't even that long, it was only a few months. That wasn't the whole year, so if it had continued for a longer portion of the year, we would have been looking at a much higher peak over there. That's obviously a record breaker in terms of Kīlauea, since these kinds of measurements began in the late 70s.

 

Then, 2019 is over, so now we can total those emissions up and this teeny tiny amount that came out last year. That's actually the lowest that we've had since the measurements started, and 2018 was the highest. So, we just swung from one extreme to another within a year.

 

For context… because some of you may not be from around here and didn't experience these high SO2 emission rates.

 

For context, the so-called dirtiest power plant in the U.S. that emits SO2 (in Ohio) is not even 1 million tonnes a year. That's about this red line. Even at these low emission rates, we’re still on par with SO2-producing power plants. When we do have active eruptions and active lava happening, our numbers are way more than any individual source like that.

 

Since this talk is about what’s going on at the summit, I'm going to focus on and jump to 2018 and 2019, specifically. These are emissions from during the lava lake era. They're pretty noisy, they're scattered, but they're in the thousands of tonnes a day range that was coming off that lava lake of sulfur dioxide. This light purple band here, those are the events of 2018. You can see early on here, when Kīlauea was having those ash explosions early on in the 2018 eruption, up at the summit, we did have a bit of a spike related to those ashy explosions. But pretty quick things died off. Here's our average of about 200-300 tonnes a day from before the lava lake. So, like I said, the lava lake was about 5000, plus or minus a few thousand [per day].  Before that lava lake existed, it was only a couple 100 tonnes a day. That's what that red line is.

 

We had that for a little while, in early Fall 2018. Since then, all these purple dots way down here on the bottom, we maxed out at about 70 tonnes a day in recent months. More often than not we're in the realm of 30 tonnes a day, which is very low, given that we've had such constant activity at Kīlauea since 1983 that brought with it more SO2 than that.

 

“Why is it so low now?” is people's question. Well, we don't have any lava. But how is that related?

 

When magma is deeper, that gas, especially SO2, stays dissolved because you have more pressure on that magma and the gas can’t escape. It's like when you have a bottle of soda. When that cap is on, before you've opened it, all those bubbles are still dissolved in your liquid, because that cap is keeping the pressure on that liquid and keeping the gas in solution. So that's the same thing that happens with gas in magma. When the magma is deeper, the gas stays in it.

 

The difference between magma and a bottle of soda is that your soda only has carbon dioxide in it. Magma has a bunch of different gases, and they all behave differently. So, the SO2, right now, where the magma is, the magma is deep enough to keep the SO2 dissolved. But, carbon dioxide, CO2, wants to escape, even at those greater depths. So, we do have CO2, that carbon dioxide, currently being emitted from the summit. But there's a lot less of SO2—that's what's mostly staying dissolved. A little bit, averaging about 30 tonnes a day, is coming out.

 

But the thing about deeper magma is that you don't have a heat source as close to the surface as you used to. So, we've got cooler conditions, which means water can persist. A throw-back to high school chemistry… and I see some kids here—you’ll get this when you get to high school chemistry. If you take sulfur dioxide and add water to it, you’re going to get this, which is sulfuric acid, which I'll talk a little bit about more later, and hydrogen sulfide.

Hydrogen sulfide is a different form of sulfur gas. That's the one that smells like rotten eggs. If you're a local resident, you may have noticed there's a little bit different odor in the sulfur smells now than we used to have with the vog from the lava lake or the Pu‘u ‘Ō‘ō era. That's because we're getting this hydrogen sulfide. There's still not much of it, but you can detect hydrogen sulfide with your nose at much lower concentrations than you can sulfur dioxide. So even though we have a lot less of that hydrogen sulfide now, and a lot less of the sulfur gases in total, you can still detect it because it’s hydrogen sulfide instead of sulfur dioxide.

 

It's this deeper magma and the fact that things are cooler at the surface, that’s why our SO2 emissions are so low. A lot of what we do have, then hits water and gets converted to a different gas. That's why the sulfur dioxide emission rates are so low.

 

We are still constantly measuring sulfur dioxide. We recently added these real-time plots of concentration to our public webpage, so you can always log in and check. There are a few different stations. This is called Sand Hill, which is about a kilometer [0.6 mile] downwind of the summit crater. You'll notice these are concentrations, not emission rates. This is how much SO2 is in that spot at any one given time, not tonnes per day, or anything like that. You can see we've got a little spike here to half a part per million, which looks like the highest one on this plot. But if I had a longer plot from this station, back to the lava lake era, we’d be way up, past the ceiling on the third floor that doesn't exist. So, things are still very low in terms of concentration and emission rate of SO2.

 

One thing that we've done recently is add a different kind of gas monitoring station, called the Multigas. That's what this guy is over here, and this lives on the caldera rim, just off Crater Rim Drive. We added that because we now have a new focus on all the carbon dioxide coming out and that hydrogen sulfide that's coming out now. So, instead of just SO2, this Multigas can detect those other gases. That's still in developmental mode at this point, so that's why it's not on the website yet, but hopefully, it'll eventually get there after we work out some of the kinks in the station.

 

That's the state of the gas right now. I'm going to turn it back over to Matt to talk a little bit about our other new feature at the summit.

 

[Speaker: Matt Patrick, USGS Hawaiian Volcano Observatory]

 

This is a recent bird's-eye view of what the summit caldera looks like today, more or less, taken from aerial images that we collected on December 18.

Here, we have this down-dropped block from 2018 and this here is Halema‘uma‘u. The  new feature since July [2019], is this water pond. This is the first time that a water pond like this has been observed at the summit in at least 200 years.

This is a virtual fly-through of the summit giving you a sense of the topography. Here’s the scarp that formed in 2018. This is that lower block, other blocks that subsided during the 2018 activity. Here's the deepest pit, this is Halema‘uma‘u, and the water pond at the very deepest portion of that.  

This exposure here is new, it exposed an area that used to be called the south sulfur banks. There's actually a small portion of the original Halema‘uma‘u crater floor in this lowermost block here.

This morning, this is the view from the webcam, taken from the western caldera rim. We have Halema‘uma‘u… we have these fumaroles, these have been pretty steady. We have the down-dropped block… the broader caldera floor… and the water pond here. As you can see, it has this yellow, kind of brown orange color.

You can also see this haze—and people who live on the island can appreciate that—but this is some water, some moisture, that has gotten into the camera enclosure because of all this heavy rain. So, on our to-do list, we have to go out there and open up the case, dry it out and put in some desiccant.

This water was first observed in late July [2019]. At that time, on this overflight, it was a tiny pond, very shallow, and it started to rise. It has risen ever since. This is just showing the first month of rise. You can see it’s filling the lowermost portion of Halema‘uma‘u here.

 

At the start, it had this greenish yellow color. Every time we go out and measure it and look at it, it's a little bit higher than it was the previous time. It's been showing a very steady rise rate, about 5 inches a day. No major changes in the rise rate. Currently, it is about 74 feet deep. So, pretty deep.

Going out there on our visits, we make these measurements with the laser rangefinder, but just with the naked eye you can often see how much it's risen just by comparing the water level on rocks along the shoreline here.

This steady rise… at first there was a question of whether this was surface runoff, rainwater, or if this was groundwater seeping in. The fact that, in this first month of activity that we observed, this level kept rising at a relatively steady rate, regardless of rainfall amounts, that was suggesting that this was groundwater, the broader groundwater table, seeping in.

This is what it looked like this morning when we went out.  You can see a lot of color variation across the lake—kind of a blue-green color here in the eastern end. This is from the western caldera, so we’re looking east. You see the color variations. Tricia will talk a lot more about how color corresponds to the chemistry.

The size… like I said, it keeps rising every day. It keeps growing because of the flared geometry of Halema‘uma‘u. Right now it's 190 meters, over 600 feet long, and almost 300 feet in the north-south direction. This is east-west, north-south.

What we observed is that this color variation is … these blue-green areas in the time-lapse videos that we take seem to be areas of influx. Maybe fresher water that's seeping into the lake. You can also see these distinct color bands here.

This is a time-lapse, two hours of activity, taken from the east, so a different direction. There's a lot of steam, suggesting the water surface is hot. You can see the motion along the surface here. What you can't really see in this video, but you can see in others, is that these areas, these blue or green areas, seem to be areas where water is migrating into the pond or flowing in. You can see a little bit of that here.

We take thermal images of the lake from the ground and from the air. They show that the water surface temperature is between 70 and 80 degrees Celsius, or about 160-170 degrees Fahrenheit, relatively consistent over the past couple of months. This is the water pond. This is hot, obviously, heated by the magmatic system.

 

To give an idea of how a water pond could form in this kind of setting, we can go through some cartoons. It shows a schematic of cross-sections beneath the ground. When we had the lava lake between 2008 and 2018, we had this large lava lake, a couple hundred meters across. We know from when it drained, that cavity did not go down too far, it went down a few hundred meters. Then, it was presumably fed or supplied by a narrow conduit, a feeder conduit, connected to the magma reservoir, or chamber. This is hot, obviously—this is magma. Presumably it would drive away any liquid water, and you’d have what’s called a “steam sleeve.” We know from a well that’s about a mile away on the caldera floor that the water table here is high.

After the 2018 eruption, when this area collapsed, Halemaʻumaʻu collapsed and disintegrated. Presumably, the water then had an opportunity, once this area that had been heated started to cool, it gave an opportunity for water to start seeping back in.

Now we have water seeping back in, but also trying to attain equilibrium with the surrounding water level of the broader groundwater table.

 

Presumably, in the coming months or years, we will see this continued rise of the water level as it seeks to attain an equilibrium with the water level measured, the broader water table. Again, this well is about a mile away.

 

How much could arise? We don't know with certainty, but we know that the water level at that well, a mile away, is about 50 meters higher, about 160 feet higher, than the current water level of the pond. If we translate that to what the level is in Halema‘uma‘u, this is it, and it shows that this pond, if continues rising to that level, would get quite a bit larger.

 

Now, Trish will talk a little more about chemistry.

 

[Speaker: Patricia Nadeau, USGS Hawaiian Volcano Observatory]

 

You haven’t escaped the chemistry yet, there’s more. This top equation is the one that I showed before, that's producing hydrogen sulfide, that rotten egg smell. But the same reaction can also produce native sulfur. If we look back at those fumaroles that Matt was showing, there is yellow bright sulfur deposits forming where some of that gas is coming out. But what you see here is this commonality, this guy here. That's sulfuric acid.

 

When you have things like that being formed at a volcano, you can end up with an acid lake. Kīlauea isn't the only lake, or only volcano with this weird-colored crater lake. There's a bunch of them found around the world in all sorts of different volcanoes—Central America; Mexico; Korovin, up in Alaska; Indonesia. There are a lot of these. Why do they look that color? What's going on with the chemistry? It's not the same color, it’s not clear like your drinking water. So, what is happening?

To get at the chemistry, one of the first things you want to think about is pH, or how acidic that water could be. Like I said, we're producing sulfuric acid with some of these gas reactions. So, it's likely that acid can end up in that lake water, but it doesn't have to.

 

This is a plot of pH, or acidity, of all sorts of different volcanic lakes around the world. This is just frequency—how many of them. You can see there's two bumps here. It's not uniform across the board. We have either this acid bunch here, that cluster around the pH of 1, or—so neutral, like regular drinking water, is [pH] 7—you can have volcanic lakes that are roughly neutral. We didn't know what we're dealing with. We can‘t just walk down to that lake, take a scoop and send it off to the lab.

 

This is where drones came in. Some of you may have seen some of these videos on Facebook or Twitter from the USGS volcanoes feed. The lake showed up in July [2019]. We didn't know if it was going to stick around. There are a lot of logistics with using a drone in a National Park, and we had never dealt with water sampling with one. So, we had to figure out a lot of logistics. This is October 26, so the lake was three months old when we were finally able to use a drone in cooperation with the National Park—we had to do safety permits and things to make sure we’re going about this the right way. This is a far-out view. This is our little hexacopter here, and there's a string with a special water sampler—I think it was 20 feet—hanging off the bottom. I'll jump to the next video because it's got a better view.

 

It’s a little hard to pick out, but here's the drone descending. Here's the line with a sampler on the bottom. You'll notice that there's little flags in different neon colors—a yellow one there, the other ones are a little hard to see. That was so the pilot of the drone could use the downward looking camera and see which flags were under the water surface, so he knew how far down he was and how close he was to the water surface. There's the drone, you can still see the little yellow flag. That one didn't get all the way in the water, but there's pink going under. We ended up getting a sample from about 10 to 12 feet down below the surface of the water. We got about 750 milliliters, not quite a liter. It's a bottle of wine volume. You don’t want to drink this though. There’s our water sample. Successful, up and out from the lake, it still had to come all the way back to us on the crater edge, which is not trivial. It's heavier, at that point, so it's harder to steer the drone. I'll jump to one more video, which has a really cool point-of-view.

 

This is the camera on the drone itself. It's looking down or hovering over the surface. There's our neon flags on the line as it descends. Some of the other videos were sped up, this one is slower—the suspense is building. This is what our drone operator, a pilot that we were cooperating with from the Department of the Interior, Office of Aviation Services, [was seeing]. There's our splash. When people saw this video online, they had questions about what happened to the flags. They thought it melted or dissolved. It just got wet and stuck to the rope. You can see the pink line there—it’s just wet. Once it's back up in the air, you can see it flopping around again. There's the water coming back out. We're happy with that—almost a success. But we still have to get it back to us, which we finally did.

 

We did a couple of measurements right in the field to measure pH as soon as we got the water. Then, for more… we've never had a water lake here before, so we don't have a lab meant for doing all the advanced chemical analysis on the water… so we ended up sending the water away to our colleagues in California to do the more advanced analyses in the lab.

 

If we jump back to this pH or acidity plot. Like I said, most volcanic lakes in the world are going to be in this neutral cluster, or this really acidic cluster. We are not. We’re weirdly in the middle. We had seen this plot. We figured it was probably acid. We had sulfur gases, so it's probably going to make that sulfuric acid and send it down this way, which it is trying to do. But the thing is, it's a new lake. The water is rising. All that acid water, or what would be more acidic water, it keeps encountering more and more new rocks to react with.

 

Those rocks are tempering that acidic tendency and pulling it back more toward a mild acid. A pH of 4, it is an acid, but it's not going to melt your hand off or anything like that. Different foods and juices, things that you consume all the time, are in that same range. The bottle of soda that I referenced before… that's more acidic than the lake. So, it's not as acidic as we might have thought it would be. If it sticks around for a long time, to the point where it reacts with enough of the rocks so that it's only in contact with already-reacted rocks, then we might start seeing that acid buildup and dragging it more toward a more common hyper-acidic pH. But we don't know how long that will take. We don't know, it may already be changing. 

Other things about that chemistry. Matt showed some pictures of those weird colors—it’s not regular water. This is some of the basics of the chemistry… there's our pH of around 4. Other things that you notice… that's a whole lot of that sulfate, and that's coming from that sulfuric acid, which is coming from that SO2 that the water is dissolving.

 

That high level of that sulfate is showing that we have that dissolving of SO2 into the water, which is a process called “scrubbing.” They were able to determine that this mineral, called gypsum or anhydrite, is saturated in the water, so we have little solid bits of that mineral suspended in the water or raining out of the water as a solid. The little bits of this solid gypsum or anhydrite in the water. If that wasn't happening, this calcium number and the sulfate number would be even higher. We're actually losing some of that sulfur to that solid phase.

 

The other thing you notice is we have this really high number for magnesium. That's because Kīlauea’s rocks are really high in magnesium, so that reaction of the acid with the rocks is dissolving those rocks to some extent, and all that magnesium is ending up in the water as well.

 

Then we have these weird colors. This is a picture of a filter that the gross weird yellow water was filtered through, and the filter ended up with this mustard-orange crust on it. In some cases, you can do analysis on that solid material and figure out exactly what those minerals are. Unfortunately, that didn't quite work out. We have some guesses as to what that might be based on the chemistry of the water, the chemistry of the rocks, and the colors, so it could be some minerals that are rich in that same sulfate, because we got a lot of that, and iron. Minerals like jarosite and schwertmannite, which I had never heard up until we had this lake. Matt alluded to this… that color is not static. Any volcanic lake can change color.

 

These are some examples from Indonesia, Kelud volcano. This is the only volcanic lake that I could find a picture of online that has a similar orange-rust color as our lake currently does. But, as you can see, at different times that same lake at that volcano could be sort of greenish-yellow, or this orange-brown. Someone's hypothesis was that the orange-brown was related to it being a dry season. It’s currently not dry here, but our lake is still orange. So, something's different about our lake.

 

Then… this is really cool. This is another volcano that has three different crater lakes, all in close proximity. It's crazy; you can see at any given time all three lakes are different colors. Then they change to different colors, and they're different from each other still. Unfortunately, I couldn't find any literature about the actual chemistry of these lakes.

 

But I did find an example of a volcanic lake in Japan. Their color change is more subtle, but it is in that yellow-green range that our lake was originally. What they did is use a device called a colorimeter, which can look at the surface of the lake, or anything, and quantify the color and the contributions of red versus green versus blue into that ultimate single color.

 

They were able to get samples of their lake, measure the chemistry, and then compare it to that quantified color at any given time. They were able to say, the blue stuff, that's sulfur. Native sulfur, like I showed you in one of those equations, is depositing and the interaction of light with that sulfur can make the water look bluer. But once you start getting different forms of iron interacting with the light in the lake water, you can head in a green direction or a yellow-orange direction.

 

They stuck mostly in this green to blue area. We are definitely in the yellow-orange range. Matt is currently… we didn't buy one yet, but he's renting a colorimeter and just got to try it for the first time today because the clouds finally parted. That is a tool that we're thinking about using in the future to try and quantify these color changes that we're seeing, because we have had color changes.

 

This is about a week or so after the water was first noticed. It’s sort of greenish, maybe a little blue tinge in there. Then as time went on, we started getting yellow, especially in the middle. Then it was a more uniform green-yellow. This was just a couple of days after we got the water sample via the drone. You can start to see a more orange patch forming over here. Then it's gotten progressively more orange, rusty color.

 

But, like Matt said, you can still see these greener tinges at the edge where we have what’s probably that influx of groundwater that hasn't yet reacted with as much volcanic gas. So, like I said, we got a water sample here a couple days before this. It was somewhere in the middle, so somewhere yellow-colored sample. We're hoping in the next week or two... We've been working with the Department of the Interior to get permission from them to do a sampling mission again. Now we're in the phase where we're working with the National Park to secure permission from them. Hopefully within the next week or two, we'll be able to get another water sampling mission done. This time, because we know we have these different colors, we're going to try and get more than one sample. Maybe get one right at the edge of that greener color. Then something in the yellow range, and then from the darkest rusty-brown to see how that those different colors vary with the different chemistries, or if there's different chemistries.

 

Maybe everything's playing a trick on us and there's really not that much of a chemical difference between the colors, but we're hoping that in the next few weeks, we hope to have some more news on whether the chemistry has changed much, whether the pH has changed much. At other volcanoes around the world, some of those chemical changes can give indications about how much sulfur is coming out. We're measuring low sulfur emissions right now, but that's because a lot of it is ending up in the water. So, we're trying to better quantify how much we're actually losing to the water by getting another water sample and looking at the chemistry of that.

Now, Matt is going to talk about some other aspects, or implications, of what this water lake may mean.

 

[Speaker: Matt Patrick, USGS Hawaiian Volcano Observatory]

The water pond is interesting, but it's also a potential concern because when magma interacts with water, it can trigger explosive activity. That obviously would be a hazard at the summit, or a potential hazard at the summit. This happens at many volcanoes worldwide. These are two crater lakes that have had frequent explosive activity, Poas in Costa Rica, and Ruapehu in New Zealand.

 

This is obviously our minds… the potential for explosive activity, in particular, because there is precedent at Kīlauea in the geologic record and there is a long history of explosions at the summit that have affected the entire summit region. This is the Keanakāko‘i explosive sequence that occurred in the 1500s, 1600s, and 1700s. Some of these explosions are thought to have occurred or have been triggered by magma rising up and interacting with water—groundwater or surface water.

 

This is one of those units, and it gives you an idea that the deposits in the summit area are up to 11 meters [36 feet] thick. That's the kind of cumulative deposits from 300 years of activity. But this is just one unit, unit D, and you can see 10 centimeters [about 4 inches] of ash deposited. This is the [Volcano] Golf Course subdivision.  

 

These larger scale explosions that have happened in the past at Kīlauea have the potential to affect areas outside the caldera. So, this is obviously on our minds, and one of the concerns related to the presence of water at the summit. The difficult thing is that the exact processes that triggered this explosive activity—because this is long ago, there wasn't modern instrumentation to track this—the exact conditions that trigger the explosive activity are still not completely understood.

 

Most likely, explosive activity in the future would be preceded by detectable precursors, such as rapid inflation or increased seismicity, that indicates magma is rising. However, at crater lakes there's always a small chance that small steam blasts, or phreatic explosions, can occur with little or no warning.

 

The presence of water alone doesn't guarantee explosive activity. We know that there's an extensive water table at the summit. We've had many previous eruptions, fissure eruptions, that presumably traveled through that water table. Fissure eruptions in the 70s and 80s, for instance, that did not trigger explosive activity. So, there must be other factors, in addition to water, that controls whether an eruption is explosive or non-explosive. For instance, perhaps it relates also to the rate at which magma rises. Faster-rising magma might leave less time to drive or boil off the surrounding water and lead to explosive activity, whereas slower-rising magma might allow time to boil off and have a non-explosive eruption. It’s still not completely understood.

Because of this concern for the potential of explosive hazard at the summit, we're continuing to keep a close eye on the summit. We have webcams. We are making routine measurements of the water level, because abrupt changes water level alone at other crater lakes has been a potential precursor to explosive activity. Thermal measurements again—tracking the temperature of the water pond at other places has been a sign of changes and hazard. Of course, we're going out and making routine visual observation. Changes in the color, like Tricia talked about, at other volcanoes and other crater lakes have also been potential precursors to changes in activity. Routine overflights. Kīlauea has one of the densest geophysical monitoring networks of any volcano on Earth. So, we have this existing network that we're always keeping an eye on.

What's happening beneath the surface? Over the last year, we have inflation that began earlier in 2019. This inflation rate is higher than what was happening in the years before 2018. This basically makes sense… we had a large draining event of the summit magma chamber and now magma is recharging that chamber. We also have elevated seismic activity at the summit when you compare it to the years prior to 2018. Over the last 6 months or so, we’ve had occasional small swarms of tiny earthquakes.

 

Overall, there's no detectable signs or obvious signs of imminent unrest or precursory activity that would lead to explosive activity in the near future. There are no signs of imminent unrest at the summit. We have this water pond… it’s relatively stable, with slow and consistent rise in water level. We have things minor moderate changes in color. We have this inflation… this is indicating that the magma chamber is recharging, as we would expect. We know the magma is still relatively deep in the system. Tricia talked about the SO2 emissions and how some of that's complicated by the presence of the pond potentially absorbing some of that SO2. We have seismicity that's elevated compared to pre-2018 levels, but it's not at an alarming level.

Don Swanson, who's worked at the summit for many years has said something along the lines that this is the most exciting period of activity at Kīlauea that he's seen in his career because we’re in a new era that we haven't seen in many years. I think we're all interested to see what's next.

 

I’ll share future talks and activities that are going on with volcano Awareness Month. I'll just leave this here. Janet is here and can provide more details on these events. There's more information on our website. What I didn't mention is that this is an exciting time on Kīlauea. Because things will eventually change, I encourage everyone to keep an eye on our website and keep an eye on our updates. We have monthly updates about activity, regular updates that can be found here.

 

On behalf of Tricia and myself, we want to thank you.