HomeArticlesWhat will you do when Earth’s largest active volcano erupts?
What will you do when Earth’s largest active volcano erupts?
February 16, 2020
Thank you for coming. And afterwards, if you have some questions about those maps or any other questions once the presentation is done, I’ll be here to entertain them. Can the screen come down? That screen come down? The sun’s already down. That’s a national park down. (audience laughs) Alright, so we’re gonna talk about Mauna Loa. I am gonna assume that people don’t know anything about Mauna Loa, so I’m gonna start very basic. And then we’ll move through talking about its history, and then we’ll talk about some of the potential hazards. Then we’ll look at what’s the current status of the volcano. The Big Island of Hawaii is comprised of five volcanoes. In the north is Kohala. And Kohala last erupted about 60,000 years ago. The next oldest volcano is Mauna Kea, and it last erupted about 4,000 years ago. Hualalai last erupted in 1800, 1801. And yet, in 1929, it tried to erupt and it failed. (audience laughs) Mauna Loa last erupted in 1984. And Kilauea, as you know, last erupted in 2018. Lo’ihi is the submarine volcano, the next potential Hawaiian Island. Mauna Loa comprises 51% of the surface area of the Island of Hawaii. And by itself, it’s almost as large as all the rest of the Hawaiian Islands put together. Okay, so where can lava effuse from on the mountain? Where can be the potential sources? So we’re gonna look at the structure of Mauna Loa. At the summit of Mauna Loa is the caldera. The caldera is roughly six kilometers by three kilometers. And these vents shown in blue are fissures from the summit. Mauna Loa has a northeast trending rift zone that heads off in this direction, and lava flows from this volcano. And the distal part of the rift zone are underneath the younger flows from Kilauea. Mauna Loa’s dominant rift zone is this south-southwest trending rift zone. And it extends for another 30 kilometers offshore. But Mauna Loa’s sort of anomalous vent system, or potential hazards from Mauna Loa that other Hawaiian volcanoes do not have, are these class of vents up here, called radial vents. And we call them radial vents because if you envision the summit caldera as the hub, and the radial vents are the spokes like on a bicycle wheel, they radiate away from the summit caldera in the north, and northwest and west flanks. In 2002, I was on an oceanographic cruise, and we mapped 11 additional radial vents just offshore here, off Kealakekua Bay, extending all the way down to Ho’okena. These radial vents can occur from the submarine environment, all the way up to the caldera. So, if these vents pop out at low elevations, then your response time to an eruption is foreshortened. So in 1877, there was one such radial vent out here in Kealakekua Bay. And these are some accounts of what happened. In the summit, there was a large cloud that rose up very rapidly from the summit, and went to an elevation of 14 to 17,000 feet. Now, I just concluded a study on the summit of Mauna Loa, looking at explosive deposits that are surrounding the caldera. And when Wilkes went there in 1841 to look at the summit caldera and map, where he set up camp, he said there was just flow after flow, and that’s all he could see. If those of you who’ve been to the summit caldera and hiked to where the Wilkes camp is, it’s right in the vicinity of the summit cabin. It’s like you’re walking on a beach. There’s these sandy deposits that are there. And so, we presume that during this eruption, that that material was deposited there. Subsequent to the summit phase of the eruption, there was a series of earthquakes. And then, the people recorded a remarkable bubbling was seen in the sea three miles south of Kealakekua, and one mile from shore. People went out there in canoes, and they found blocks of lava two-feet square that came up from below. And then they said it was red hot, and there was a sulfur smell in the air, and fish had died. Some of these specimens were collected. If any of you guys know where those specimens are, we’d like to have a sample. (audience laughs) Anyway, in that same oceanographic cruise, we were offshore here, and we were able to go and map out what we think is the 1877 vents. Here are pillow lavas from those vents. You can see they don’t have any heavy sediment on them. When we picked up the samples, they were very glassy and fresh-looking. They didn’t look altered. And then we actually stumbled upon here, which looks like a vent with some drain-back. Okay, so now we’re going to look at the historical eruptions of Mauna Loa. The historical eruptions are the most well-documented. Actually people were here that actually wrote these down and charting what happened during the course of these eruptions. The first eruption that we can actually find evidence of on the ground is 1843. The summit, oop. The summit caldera is the source for about half of the eruptions. So that means, the summit, there’s a breakout in the summit, lava flows will fill the caldera. And then, some flows may actually leak out of the caldera, either to the north or the south, because that’s where the topographic low is. But these lava flows don’t generally threaten any communities. The Northeast Rift Zone is the source for about 25% of Mauna Loa historical eruptions. You can see that the flows emanating to the north basically buttress up against Mauna Kea, and there’s a shallow valley-like structure between the two volcanoes. So when the flows hit this natural drainage, they turn and head downslope in the direction of Hilo. The Southwest Rift Zone is the more dominant one, and it has flows that have basically gone to both sides. If you look at the northeast rift, there seems to be a majority of the flows heading towards Mauna Kea. On the Southwest Rift Zone, we have flows on both sides and about 20% of the eruptions go down that rift zone. Now there are three radial vent eruptions. Probably the one that most people are gonna be familiar with is the 1859. It started up here at 11,000 feet, behind Hualalai in the saddle but high on the flanks of Mauna Loa. And the flows go all the way down here to Kiholo Bay. The other flow I just talked about was the 1877 flow in the submarine environment. And then up here high on the flanks is a radial vent from 1852. Now, for Mauna Loa, we like to pride ourselves with this volcano. Probably it’s going to be, when it’s finally done with geologic mapping, the best geologic map of any volcano and the best dated. So far, we’ve been able to map over 500 different lava flows on it, and we’re only mapping the surface. And we have over 300 radiocarbon ages. So about 35 to 40% of the flows have been dated. And then we can take this information and compile a long-term history of the volcano. What we’ve done here is we’ve broken out the lava flows into epochs of time, so roughly 1000-year intervals, excluding the historical and pre, and near-historical lava flows. So the warmer the color, the more recent the lava flows. Here are the flows in the historical period of time from the Northeast Rift Zone, and you can see that they had a tendency to go to the north. If you look at the prior epoch of time shown in orange, you can see that they go to the south. Now we don’t completely understand why this is happening, but there sort of seems to be a self-righting effect of erupting one side and then the other side. The other important thing about this is the distal part of the rift zone here has all these cooler colors, which means it hasn’t erupted as frequently in time as the other portions of that rift zone. And so, the colors here, the hypothesis is that Mauna Kea and Kilauea are squeezing the volcano, making a compressive force so that dikes won’t intrude into the distal portion of the rift zone. And so, the geologic record is very suggestive of that because the colors are much cooler. If you look at the Southwest Rift Zone, you can see the colors of lava flows, no matter what epoch of time, are more evenly distributed. There isn’t a preference. Also, the entire length of the rift zone has been active in recent time. The one thing that stands out, well, there’s several things that stand out, but down here, you can see on the southeast coast, these colors are old-age lava flows. The oldest rocks on Mauna Loa are these rocks here, known as the Ninole Hills. How many of you guys know where the Ninole Hills are? Those of you familiar with the island, if you go to the Black Sand Beach at Punalu’u and to see the turtles, if you turn around and you face mauka, you see these large flat-topped mesas. Those are the Ninole Hills. Those are the oldest rocks at the surface of Mauna Loa, and they’ve been dated at about 110,000 years ago. The other portion down here is down by South Point. This area hasn’t been inundated by lava in a while. But if we look over to the other side of the rift zone, you can see very warm colors. The distance between the rift zone and this coastline is shorter compared to this distance from here to the coast on the southeast side. Another thing from one of our studies that we just concluded, well, several years ago, was that the rift zone on Mauna Loa used to extend from the summit caldera past the Ninole Hills, out past the Green Sand Beach. Okay? So that was the original orientation of the rift zone used to be over here. And then when we had a catastrophic landslide on the east side of the island, we actually had the rift zones migrate over to where there was a free surface. Okay, and then, if we look over on this side here, all of these dark flecks that I’m showing here are the radial vents. And the radial vents were spread over times from present, all the way up until about 2,000 years ago. If there are any older radial vents, they’re probably buried, ’cause the lava flows on this side are fairly young. As I said, the radial vents can occur at almost any elevation. So to put this in context, the missionaries were here when you see the red colors. The Hawaiians got here under the yellow color regime. Okay, so we’re looking at eruption rates now. Here’s a map showing the slope of the volcano, the steepness. And so, the warmer the colors that we have here, the steeper the slopes. These big numbers here are average effusion rates in millions of cubic meters per day. So we have on the southwest side of the island, we have high effusion rates, we have very steep slopes. And the combination of those two results in very abbreviated times from when the vent opens, to the lava actually hitting the ocean. See that, these are hours. Three hours, 18, 24, 29, three and a half. The one anomaly is the one in 1926. In 1926, the eruption broke out right at the rift crest, and so lava went both ways for a while. And then eventually the eastern lobe dried up, and lava then, the bulk of it, went into the southwestern lobe, and that’s where it threatened the town of Miloli’i. So high effusion rates and steep slopes result in rapid advance of lava flows. On the Northeast Rift Zone, we got basically about half the effusion rate. The town of Hilo is located there. And the one thing that the Hilo side has that the Kona side doesn’t is that up here in the Saddle Road area, you have this hint of green. So the slopes are gentle. The lava flows come down from the rift zone very rapidly. And then they hit gentle topography. They start to pancake. The flow front velocity actually slows down. And yet, the source doesn’t know what the flow front is doing, it just keeps shunting lava. So if the flow front doesn’t move rapidly enough, you create a log jam situation at the inflection point, lava ponds, and the lava will jump out and make a subsidiary flow. It did this three times in 1984. So topography up here is facilitating a strategy of divide and conquer. The one lava flow that actually made it within the city, actually this is the, the one that actually made it right into almost downtown Hilo, is the 1880-1881 lava flow. That was a slow, oozing pahoehoe lava flow, and it took over 200 days to get down there. We really have only one benchmark for the radial vent eruption. That one was in 1859. The ‘a’a phase of this lava flow hit the ocean in eight days. The pahoehoe hit it in 120 days. So, ‘a’a, ‘a’a, ‘a’a, ‘a’a, ‘a’a for eight days, 120 days, 200 days. Okay, so we’re gonna take a tour of some of the couple flows from the Southwest Rift Zone of Mauna Loa, because that’s where we are, the province. And so, we’re gonna take a look at the 1926 lava flow, and then the 1950 lava flows. Here you can get your bearings on the years of the different eruptions along the Southwest Rift Zone. In 1926, here’s a view of the Ho’opuloa lava flow, and this is the regional village of Ho’opuloa. Miloli’i is a little bit further to the south. You can see the wall of lava was about 30 feet high and 1,000 feet wide. And you can see here the orientation map. Here’s the view from the actual harbor there. So the lava flow, you can see how tall it is, and it just grinds and pulverizes and burns up everything in its way. The lava then came right down and it’s right in the middle of the village. You can see this, it’s taken out a few of the homes there. Now it’s 40 feet high and 2,000 feet wide. And so, here is the lava flow superimposed on what we have as the current. So here’s Miloli’i village. This is the first extension of that, and then this is the current. Most of the people live over here in the subdivision. This is mostly the Hawaiian community from the regional fishing village. Here’s some other pictures of that. This is taken from almost the same place. You can see the lava flow there. There’s the new houses on top of the flow. And there’s the thickness of the lava flow. Okay, so now we’re gonna take a little tour of the 1950 eruption. Some of the people say that the 1950 eruption was Mauna Loa’s most spectacular eruption because the effusion rates were just basically, as a volcanologist would say, out of this world, because it was many orders of magnitude higher than what we’ve been able to see in the recent past. Here we have the fissure vent. The fissure was 21 kilometers long. And effusing lava across the fissure system, at different points in time, it activated, if you take the original trace all the way back 21 kilometers. So the eruption had effusion rates on the order of 1,200 to 1,800 meters per second. During the Pu’u ‘O’o days, we had about two meters per second. And in the 2018 eruption, we had about 350 meters per second. And Mauna Loa still was three times higher in its effusion. This is the view from Ho’okena. And we’re looking at those lava flows, and you can see, they came down across the highway and entered the ocean in three different locations. So the question is, if you live in South Kona, which way would you drive? (audience laughs) All right, we can talk about that later. So here’s a clip of the lava coming across the upper highway there. And look at the size of these blocks. Wow. Look at that one. (audience chatters) Yeah, look at that part. The average rate of advance of this flow was on the order of 10 kilometers an hour. (audience chatters) You can you look at it one more time. (audience chatters) Look at that. Wow. The other question is how many of you would like to be standing right, oop. (audience laughs) (laughs) Sorry. How many of you would like to be standing right there? (audience laughs and chatters) Budding volcanologists. (audience laughs) They wouldn’t let us today. (audience chatters) Is that the front of the flow? No, that’s just looking at the channel from the mauka highway. So it’s going from mauka to makai. You’re watching transit, yeah. How far away are those people from that? I’m guessing that they’re standing on a ridge here, and then it goes down and goes back up. And so, this part here has overflowed the ridge that was holding the lava in that channel. But there’s still another ridge right here. From what I’m seeing, you can’t really see it in this video. Okay, let’s talk about lava inundation maps. Some of the things from learning from what we gain from the long-term history. We decided that we needed to make some products that people can use, be helpful for planning purposes for emergency managers. And so, instead of it being top down, where the lava flow is going to come and then shift downward, what we did was we identified communities on the blank of the volcano, and we went from bottom up. We tried to delimit segments of the rift zone that can shed lava into the different communities. And then we lumped them into those lava inundation zones. Okay? As I said, we have these maps, and they’re online. You can download them if you want to. To illustrate how these maps are intended to be used, here’s an example from Hilo. This is the lava inundation map that we created for Hilo. This yellow zone right here represents the rift zone. The rift zone has both positive and negative topography, so it can act as lava diversion structures. So the path of a flow is not very predictable when you have complicated topography. So if you read the maps, one of the caveats is, the lava has to actually exit the rift zone in order for the inundation zone to be valid. Okay? We had an eruption in 1984. And so, if you were the emergency manager, the idea is we’re gonna use this map for planning. I have limited resources on the Big Island of Hawaii. Where am I gonna put my resources for a 1984-like eruption? Using this map, you can actually delimit an area up here that would be impacted, or one there, or a different one here. Instead of, in 1984, they closed the roads all the way down here, all the way over there, all the way across the Saddle Road. Okay? This is what people saw in 1984 from Hilo. All the people of Hilo saw this. They look out their windows and they’re like, ah. They see this glow, and everybody is in kind of a state of uneasiness. (audience laughs) Yet, if the maps existed, some people could actually go to sleep at night and not worry that the lava’s coming to their house. So this is what happened in 1984. The fissure propagated down here. The initial breakout sent lava flows in this direction. Here’s the Kulani Correctional Facility. So they thought, oh, the lava flow’s gonna get to the prisoners, and how we gonna get the prisoners out of there? One idea floated was they’re gonna take the Robert’s buses and drive them up there, and load the prisoners on and drive ’em away. Fortunately, 24 hours later, these flows stopped already. And the main lava flow headed off in this general direction. And so now, if you’re the Civil Defense Director, you basically have a very limited geographic region if you need to evacuate, or how many beds you’re going to supply, and so on and so forth. Those other people in Hilo that lived in Waiakea looked out their window and, wow, the lava flow’s coming, but it’s not coming to my house. So then they go to sleep instead of everybody having sleepless nights. Okay, so that’s the intent of how these are supposed to be used. We have other tools that we’re using now to actually further delimit. We use the steepest lines of descent. And they actually, several lines can be within one inundation zone. So we can use those lines to further guide where flows might impact. We can also do some flow modeling things, so we are building up our tool set. Okay, so now I’m gonna move over to monitoring and what we do, and what’s the status of Mauna Loa. This is a map showing all of our sensors across the Island of Hawaii. The various sensors are represented by the different dots here on the map. And you can see that Mauna Loa and Kilauea are the two most active volcanoes and, therefore, they have the densest array of monitoring equipment. Even though my boss is in the back, I’ll say this. It should be no surprise that Mauna Loa is going to erupt. Okay? All right. And that’s my personal opinion. (audience laughs) Anyways, so these are the sensors that we have on Mauna Loa specifically. And as I said, we are monitoring these volcanoes. But, if let’s say, if Hualalai was to show some signs of reawakening, then we would put additional instruments to better monitor that volcano. Right now, Hualalai is not showing any signs of life. We have a seismic station there that’s a 24/7 sentry and it sends back data. All quiet. Okay, so now I’m gonna do a series of cartoons, sort of a general way of how we monitor volcanoes. Let’s call it the layperson’s guide to volcanic monitoring. Before there’s any ingress of magma to the reservoir, we have our sensors out here collecting data. And if there’s no ingress of lava, we basically show no change. Everything’s sort of the status quo. We can look at elevation changes. We can look at X-Y changes on these GPS stations. We have tiltmeters that tilt upward when there’s influx of magma to the reservoir. Okay, so now the magma starts to come in, ever so slowly, into the reservoir. We actually notice deformation changes, or these changes in these instruments first, before we have increased seismicity. So we have influx of material into the volcano, and as more material comes in, then we notice elevation changes, and we notice increased tilt. And there might be an occasional earthquake. But for eruption forecasting, it’s when these magma comes into the reservoir and starts to stress the edifice, and generate many more earthquakes, is when we start to look at forecasting the eruption. No earthquakes, there’s not gonna be an eruption. You gotta have earthquakes to have an eruption. Okay, so then we stress the edifice, we noticed these changes all up here. If there’s a failure or there’s a propagation of molten material, the way we can track these earthquakes, the direction and the depth of the earthquakes, will actually track where the molten material is. If you had instruments on the distal flank of the volcano, these would be all going up, and the tilt will tilt away from this area. And response, the summit is providing magma on the distal area so the summit will drop correspondingly. Okay, so what did it look like precursory seismicity before the 1975 and 1984 eruptions? Why do I just choose all of these based on all the 33 historical eruptions? Because these are monitored in the modern era. The other ones had older instruments. A lot of them were people-felt earthquakes and would write them down, and their observations. But these ones we actually collected seismic data, et cetera. So, as the volcano starts to have ingress of molten material, we start to see these deeper earthquakes on the northwest side, and the color is reflective of the depth if you look at the charts here. Then, as the volcano becomes more and more distended, then the migration of earthquakes comes in a shallower and shallower environment. And then eventually we have an eruption. And these are earthquakes of magnitude greater than magnitude 1.6. And the reason why we use the cutoff of 1.6 is because the older instruments aren’t as good as the new ones. So the new instruments can get negative magnitude, whereas the old instruments would never even shake under a negative magnitude. In order to compare apples to apples, we take the new data, we filter it at 1.6, and the punch line isn’t there yet. (audience laughs) So right now, we’re just looking at seismicity, a plot of seismicity on Mauna Loa for the last week. And we see there’s about 14 events. This is looking at the earthquakes per week over a six-month period. And this is looking at earthquakes per week over a one-year period. If we look at this, the one-year period, you can see we have higher numbers of earthquakes. Right about here is about 100 earthquakes. So we go up to a 100, approach 100, and then we drop back down, go up to 100, drop back. So we’ve got this sort of sawtooth pattern of seismicity on this volcano. If we were gonna have an erupting volcano, we would expect this number to just kind of be going upward. The blue would go up. Ignore the red line, ’cause that’s a cumulative. But we’d expect these to go up and up and up. In 1974, we had on the order of a few hundred earthquakes per day. This is per week chart. In 1984, we had in the mid to, we had like 50, 60, 80 earthquakes per day. And this is per week right now. Okay, so now we’re looking at seismicity from now. And then you say, well, that sort of looks like the other two. And it does, it does look sort of like the other two, if we’re looking at two years of seismicity. Okay, so let’s see what the other indicators tell us. Now we’re looking at deformation. The earliest deformation that we had was using a laser ranging device and measuring the length across here. Imagine two dots of a balloon. You inflate the balloon, and then you measure the dots before and after, and you see the line, actually the dots moving further apart. It’s reflective of inflation. Nowadays we have GPS. And so now we don’t need to use the laser ranging device. And actually from the GPS, we get a very large synoptic view where we can see down the flanks. You don’t even have to see across the summit of the volcano. The world’s largest volcano we can measure across the flanks of the volcano. So that really enhances our ability to monitor this volcano. Here we have three years of GPS data. You can see, here’s the summit caldera. And you see the GPS vectors on this side are smaller than the ones on that side. And so, at the base of each arrow is a GPS station. And down here is the scale of motion of these arrows. Okay? And you can see that the volcano is moving towards Kilauea faster than it is moving in, like a balloon, a radial pattern. If we look at one year, we start to say, oh, look. Look at that. These arrows are starting to show a radial pattern, so Mauna Loa is slowly inflating. And if we look at six months, we can see a radial pattern here. These vectors are still a little bit smaller than those, but the pattern is more radial, so we have slight inflation of the mound. Okay, we also have other tools in our tool kit, and this is satellite data. We have a satellite that passes over, and then it passes over another time. And we’re looking at elevation changes between time A and time B. And so, what you’re looking at, this bull’s-eye pattern. And each one of these fringes, let’s say from magenta to magenta to magenta, is about 1.5 centimeters of change. So we have one, two, three, four, five. We have about 7.5 centimeters of uplift. Okay, and that was from January to June of 2019, last year. We just recently got a new one, which is a one-year view of Mauna Loa. And so what you see here is you see these same fringes out here except, you look on Mauna Kea, an inactive volcano, you can see it has fringes as well. Those fringes over Mauna Kea are due to atmospheric conditions, okay? The clouds and the moisture in the air can actually give the impression that there’s deformation. So in reality, if we’re looking at the changes for Mauna Loa, we’re really just looking at this little area right in here, ’cause these are also atmospheric. We have to ignore that, and you can see there aren’t as many fringes as the prior record. So, it’s still inflating, but the rate of inflation is less. So, what’s happening? We have small inflation at the summit. We have above background seismicity intermittently. We have slightly above background seismicity in the summit and in the upper Southwest Rift Zone. But it’s sort of episodic. I showed you that sawtooth pattern. What are we missing in order to have an eruption of Mauna Loa? We really need to have more consistent and persistent seismicity. The rate should just be going gradually up and up. Instead of us counting at earthquake per week, we should be counting at earthquakes per day. And then we expect and hope to see increasing rates of deformation and seismicity as we get closer to the actual eruption. What is HVO doing in response to these above background levels at Mauna Loa? We are upgrading and increasing, we’re maintaining always, and upgrading our monitoring equipment. We’re adding new instrumentation. We’re starting to do internal planning. People on our staff, most of them were born after the Mauna Loa eruption. So, they have no idea what that is. So we’ve got to kind of build up and plan for what may happen. We’re starting to coordinate with our partners in CD. We’re looking into different kinds of assets to include drones. We are going out and briefing essential personnel, people that should be briefed. And then we have community outreach, like this, Volcano Watch, and other things that we have. We have web presentations and community meetings. Thank you. So, people should be aware of the hazard. You should stay informed. And the take-home message is an eruption is not imminent. (audience laughs) In 2002, we had a meeting like this where we said there’s a slight swelling and this is what the press did. (audience laughs) So the take-home message is an eruption is not imminent. Okay, questions? (audience applauds)