A virtual walk through Kīlauea Volcano’s summit history: Part 3

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Join USGS Hawaiian Volcano Observatory scientist emeritus Don Swanson on a virtual walk, during which you learn about the past 500 years of Kīlauea Volcano’s history as revealed by rocks, craters, and cracks.

This virtual walk will be released in three parts, covering different sections of the Keanakākoʻi Crater trail. Along the walk, Don points out and explains some of the features that formed during the 2018 summit collapse events, as well as the best publicly accessible display of explosive deposits erupted from Kīlauea around 230–370 years ago, one of which probably relates to an important oral tradition. Don also shows two contrasting vents for the July 1974 eruption, highlights the thick deposit of pumice and scoria erupted in 1959, and ponders the origin of Keanakākoʻi Crater.

You can visit the Hawaiʻi Volcanoes National Park website to learn about walking the 2-mile round-trip Keanakākoʻi Crater trail, which begins at the Devastation Trail parking lot on Crater Rim Drive in Hawaiʻi Volcanoes National Park.
 

Details

Date Taken:

Length: 00:44:14

Location Taken: HI, US

Transcript

 

Well this is as far as we're allowed to walk now. During mid-May until mid-June 2018, I could drive in here and drive down to the Halema‘uma‘u parking lot to collect the ash from buckets there that were collecting ash and also to examine the development of the cracks along the road. These cracks, just beyond the gate here, were smaller than they are now of course, but nonetheless, it required me to  go around them, too, because you couldn't just drive/stay in the same lane all the way. Finally, things got too nasty and I had to back off.

 

This road-cut here is the only place in the National Park now where you can see a cross section of explosive deposits from the last 150 years of the past explosive activity, from about 1650 to 1800. It's the only place unfortunately that you can see that. I know that you're not concerned about the details of these deposits, but I do want to tell you some things about them because it's such an important part of Kīlauea’s history. Virtually every bed there would reflect a separate explosion ,or maybe several beds can be lumped into a series of closely-spaced explosions.

 

Any of these explosions, had you been here, would have been lethal to you. The explosions we think were mostly driven by heated groundwater—the steam hypothesis that we can't be sure about. The exposures here in the road-cut extend from about 1650, as I said, this deposit there, up to a little bit younger than 1790. So we have 150 years of Kīlauea’s history exposed here. Now, the work that’s been done in the past 20 years has shown that the explosive part of Kīlauea’s history is far more important than we realized beforehand. It turns out that explosive periods and effusive periods can be recognized. By that I mean that there were periods of time lasting a few hundred years in which the dominant kind of eruption was an explosion. And then that period ends, and you start into a period dominated by effusive eruptions of lava flows with few explosions taking place. At Kīlauea since the early 1800s, we've been in an effusive period and that's one reason that people didn't realize that the explosive part of Kīlauea’s history was so important.

 

But if we, rather than being in the early 21st century, as we are now in 2020, but if this were, say 1720 or 1620, our view of Kīlauea would be very, very different. This would have been quite an explosive place. There were no lava flows being erupted up here at the summit or anywhere that we know of. The caldera was growing, much deeper than it is now except for the Halema‘uma‘u part. And so things were very different. And we just need to realize that and try to understand the changes that have taken place.

 

I've done a lot of work trying to correlate Hawaiian chants and oral traditions with the eruptions, and we can’t see the earliest explosive deposits, which I think the chants describe quite nicely. It's an R-rated story so I'm not going to tell it here, but I published it actually in a scientific journal so if you're into R-rated stories, you can read it there. But I think it tells about the development of the caldera after a long period of lava flow extrusion

 

There were 150 years—the caldera formed about 500 years ago and then 150 years—of explosive deposits, the oldest one of which we can see here is this one. This is a very different kind of material than was erupted either before or after the eruption. This is scoria resembling in some manner the 1959 scoria except that 59 is very glassy and this is not glassy, not very glassy at all.

 

Then you go up above that and you get into a unit here which has lots of accretionary lapilli in it—they're little balls of fine ash stuck together when they were wet indicating a wet eruption. Then, you get into a lot of different layers. As I said, each major layer at least, probably reflecting a significant explosive eruption. And then the prominent ledge below the gravel is the footprints ash and the gravel is related to the footprints ash. We’ll talk about footprints ash and the gravel just right up here at the end of the outcrop—that's 1790 deposits.

 

But I want to talk about this one here a little bit because this one also has significance to Hawaiian culture, I think. This is a deposit that came from a high lava fountain. This is a map showing the 1959 Kīlauea Iki deposit and this the outline of this deposit. This went very much farther down toward the southeast and came from a column height we think was 10–12–15 kilometers high [6–7–9 miles]. This deposit, I think, relates to one of the famous stories told frequently about a battle that Pele was having with an erstwhile suitor of hers named Kamapua‘a.

 

Kamapua‘a was a real handsome hunk at times, but pua‘a means pig in Hawaiian and he was literally a pig other times. He had a changing, schizophrenic personality. One time, as the story goes, Pele and Kamapua‘a were having a big fight and Kamapua‘a finally poured a lot of water on Pele to try to put out the fire and drown Pele. Pele almost succumbed, but she finally mustered all of her strength and she rose up out of the crater and she threw rocks at Kamapua‘a and chased him all the way to the ocean.

 

This is a deposit that is the only one in the relevant time period that sent rocks as far as the ocean. Now, where the Chain of Craters Road reaches the coastline and make its big bend, you can find small outcrops of this deposit down there—still centimeter, or half a centimeter [less than an inch] sized rocks in that deposit.  So I think that that is the eruption that produced the deposit here, it’s the one that Pele used to send Kamapua‘a away and that would have taken place in about 1650 or so based on carbon 14 dating that we've done on charcoal above and below this deposit.

 

Parenthetically, I might say that I think that Pele’s reputation for having a terrible temper derives from this period of explosive activity. What do some of us do when we get angry? We throw erasers or dishes or something, right? Pele was angry, I think, and that reflects a temper that I don't think is reflected by the slow effusion of pāhoehoe, of lava flows. So I think it was this period of time from about 1500 to the early 1800s that really gave Pele her reputation, and probably the first part of that was the most important in deriving Pele's personality.

 

So then after 1650, just as before, there were lots of repeating explosions until we get up to most famous one of all—that's 1790. We'll go take a look at that next.

 

We’ve now reached the deposits that I think are related to the famous or infamous lethal eruption in 1790. I want to go through the reasoning related to this eruption both because it's an interesting sort of detective story, but also I think it tells us what could happen in the future. This layer here, which you can see extends farther along the outcrop here, it's very prominent. It's the same one that we can see along the road farther up. That is a fine ash deposit made of fine ash and little spherical BB-size and a little bit bigger balls of ash that are stuck together. They're called accretionary lapilli or pellets or whatever, and they are pretty good evidence that the ash was wet when it was falling. Whether it was wet because it was erupted wet or whether it got wet in the air as it fell through rain is always the big question, but it was wet when it landed.

 

There's even better evidence than the geologic evidence that this was wet. That is at other localities down the Southwest Rift Zone in another lobe of this eruption, there are thousands of human footprints indented on the surface of this deposit. We've tried to figure out something about the people who made the footprints, so we've measured the size of almost 500 footprints. The footprints have to be well-preserved to do this, but we were able to find almost 500 footprints. What you do is to measure the length of the footprint—these were, of course, barefoot people—you measure the length of the footprint from the back of the heel of the tip of the big toe. That length will be 15 percent of your height. Measure your feet tonight and try it. Check it out. There’s very little plus or minus with that, you know it's pretty amazing. So we did this, we measured footprints and it turns out that when you calculate the height of the people who made the footprints, the average height is five feet.

 

Now, contemporary Europeans, or Europeans who arrived in the 1820s and missionaries later,

commented on how tall Polynesians in Hawaii were relative to the European heights. A very famous missionary, Titans Coan, estimated that the height of Hawaiian warriors averaged 5 [feet] 10 [inches].  And male skeletal remains over in Kona—pre-European contact remains—have been found to average about five [feet] eight [inches] or so.

 

When we calculate a height of five feet—those are women. Most of the footprints were made by women. Occasionally, you can see tiny little footprints. There's one place that I know of where there was a woman's footprint and right alongside, there's a little child’s footprint. It's as if she got tired of carrying the kid and plopped him down on the ash. There are taller people of course, men, involved and the ratio of men to women is something on the order of 1 to 4 or four and a half, something on that order, sort of family-grouping size. But anyway, so the footprints, people were walking on this wet ash, mostly women, some men for 20 kilometers [12 miles] down the rift zone from the summit area here.

 

It must have been kind of horrifying walking on this—wet, slippery—and the air was probably still chock full of fine ash and so forth. Now what also occurred around the summit, not where most of the footprints are, is that the eruption of this material up here took place and the footprints ash was still so wet and soupy that rocks from this eruption plunked into and sunk into the footprints ash. So if we go up here and look any place where you find the footprints ash in the summit area you can find that there are rocks embedded in it that came from and sunk into it from this second eruption. So that means that the time between the eruption of footprints and from the time of this unit, which I'm going to call unit J1, was short—minutes to a few hours probably. Otherwise it would have dried out quickly. As we know around here, when the sun comes out, mud dries very quickly. So I would say that the two events were very closely spaced in time.

 

But how do we know what year they were? How do we know that it was 1790? Well, the story is this: there was a marooned English sailor up at Kawaihae, at the north end of the island. He was keeping a ledger. The reasons for why he was marooned there are suspicious, we don't really know why, but anyway, he was there keeping the ledger. In it he wrote that, this was early in November, he saw a cloud rise and tower above the summits of Mauna Loa and Mauna Kea—he said the mountains.

 

Well, in order for him to even see the top of the column from where he was, we know where he was in Kawaihae, the column had to be about 19,000 feet [6 kilometers] high and it was towering over the summits. So [Thomas] Jaggar and a lot of people including myself have all estimated that the column height was probably at least 30,000 feet high, 9 kilometers high, and could have been even a lot more than that. So what's the significance of this—John Young, the name of the marooned sailor—what's the significance of his observation?

 

Well that means that the upper half or so of that eruption column, carrying ash with it, got up into the jet stream. The jet stream—the subtropical jet stream—blows across Hawai‘i at elevations of between 4 and 15–17 kilometers [1300 and 50,000–55,000 feet] above sea level out of the west, northwest—north, usually, year-round.  It doesn't change directions as it does in many tropical areas. At least that's the way it's been for as long as the records have been kept. So if John Young sees an eruption column 9 or 10 kilometers [30,000 or 33,000 feet] or more high. that means that the upper part of that column got into the Jet stream and so that the ash would be blowing toward the east and the southeast.

 

This contrasts with the trade wind direction that I showed you a bit ago, that would go toward the southwest because the trade winds are blowing out of the north and northeast instead. This is not this deposit but it had a similar orientation. It was blown by the trade winds toward the southeast. So what you do, what a geologist does, is to “go southeast, young woman,” go southeast and look for deposits—ash deposits. And you find them. There are ash deposits interbedded in soils and usually bioturbated into the soils and so it's kind of a mess but you find rocky material in organic soil down there. Then, you start walking back toward the summit area, digging pits along the way, and examining.

 

What you find is the youngest of those ash deposits in the southeast correlates with this thing up here. You can walk right into it with J1. I found J1 now as far as Kaimu, and it's still going—I gave up there. Since that's the most recent of these deposits and it corresponds to what John Young saw—the column—we assume that this is 1790 and by extension then the footprints ash, which was still wet, it's also 1790 and the footprints were made in 1790.

 

So what happened in 1790? Well there was sort of a conflict going on for supremacy of the island. Kamehameha was rivaling his cousin Keōua and they had a skirmish at the north end of the island. Then, Keōua had gone down to Waiākea in Hilo, and got wind of Kamehameha’s advance down the Kona coast into Keōua’s home country of Ka‘ū, down toward South Point. And so, Keōua mustered his forces together and started across the volcano.

 

Hawaiian forces brought their families with them, so there'd be a lot of women and children as well as their warriors with them. They got up into the summit and Pele was angry—huhūloa—she was a throwing rocks and so they couldn't go beyond for three days, three nights. Finally, there was apparently a break and Keōua split his forces into thirds. The first third got through unscathed. The second one was totally annihilated. The third group was injured—some of them were—but for the most part survived. The middle group was just in the wrong place at the wrong time.

 

This probably occurred on the west side of the volcano because there was prominent mauka–makai trail, or mountain-to-seacoast trail, and that’s where all the footprints are. So it seems as if that's where the fatalities were—somewhere close to the summit along that trail. There's a place out there where I found a large patch maybe about as big as the area we're sitting on here now; it's trampled on—footprint on footprint. You can't measure the size of footprints because they're one on top of the other. I just wonder if that isn't a place where a lot of fatalities occurred.

 

What caused the deaths? We think it was a pyroclastic surge that swept across the western, especially the southwestern, flank of the volcano. We find surge deposits there that are just younger than this fall deposit here. I've mapped them out and it's not a terrifically large surge but it certainly would have been hazardous. A surge is a rapidly-flowing hot mixture of gas and rocks. The air moves at hurricane velocities across the landscape and it's one of the most lethal kinds of volcanic events that can occur. At Mount St. Helens in 1980, there was something called a lateral blast, which was a surge it turns out. We would now apply the term surge to that, which killed 57 people.

 

And then the condition of the bodies suggests that they were killed by a surge. Now, all of this was written down several decades after the fact, so you need to take everything with a grain of salt, but the description of the bodies is that the skin was scorched but in no place deeply burnt. This suggests a rapid passage of hot. They weren't bombarded with large rocks so it wasn't falling ballistic blocks that got them. And one of the most intriguing things to me is that the later missionaries put their spin on it. They found people or corpses were found clasping on to one another and the missionaries said that they were holding on to one another as if they were taking final leave. I have a more practical solution—I think they were trying to keep from being blown away by this hurricane-velocity surge that was blowing past them, they had nothing else to hang on to except themselves.

 

I’ve seen this on videos taken of typhoons in southeast Asia, and you will find that people are grasping on anything—light-poles or whatever, themselves—to keep from being blown away. So I think that's what what was happening. I think that a surge probably related to this eruption but in places at the end of that eruption is what would kill the people. It killed a large number of people—the estimates range from about 80 men to 400 countrymen to 400 warriors to 800 warriors. All these estimates are for men. The warriors had their families with them so I just figured that there were a few hundred people killed probably by the surges within a kilometer or two [less than a mile] of where the former HVO site was.

 

I told this story because it's kind of interesting how you piece various different kinds of observations together. But it tells you the kind of thing that It can happen in the future. And if it can happen, it probably will happen. Maybe not in the lifetime of any of us now, we can't be sure. But surges can occur, it can be very important. And although there haven't been that many large ones at Kīlauea in the past—if one were to occur at the wrong time, when people are around, bad things can happen. So that's the story of 1790, a tragic event.

 

Because the 1790 event made such an impact and killed so many people, it was thought before 20 years ago that all of the explosive deposits that we were looking at down there, and even earlier, were related to this one eruption in 1790.  You'll see a lot of older papers and the geologic map of the summit area here that refer to this as the 1790 deposit. It's an important part of the deposit but as you can see, it's only a fraction of the total deposit. It was probably the largest eruption that occurred, but it’s not necessarily the most dangerous. If people had been around during the earlier eruptions, they could have suffered as well.

 

I think looking at the scoria down there of unit E and on top here, this is I and J1, you can see that the volcano has impacted people in some negative ways, but I don't want to leave you with a negative impression. It turns out that the volcanic ash that's erupted during these explosions, particularly the big explosions when the ash can be blown by the jet stream toward the southeast, the ash has produced deposits that have been important for agriculture by Hawaiians, pre-contact agriculture for Hawaiians.

 

Imagine, you have bare pāhoehoe surface stretching for miles [kilometers]. Pretty hard to manage sweet potatoes, your sugar cane and so forth. Maybe people do it in places, but then you put some ash on there; you get a nice soil developing and that's what made it possible, I think, for Hawaiians to have their agriculture as you get into the ahupua‘a that are south/southeast from here, between here and Kalapana. The explosions that would have been devastating at the summit are beneficial in the far field.  

 

You guys have any questions now? Well let’s go over and peek into Keanakāko’i Crater.

 

This is Keanakāko’i Crater. That means the cave or the place of the adze. Keana, the cave or place and, ko‘i, adze. The pit crater formed probably after the caldera formed, but we don't know how long after or maybe contemporaneous with caldera collapse. Kīlauea iki, the double craters there, may be similar in age, we just don't know. It's hard to date a hole.

 

The crater has its name because there are there are stone tools that were purportedly made from a fine grained rock in Keanakāko’i, cave of the adze. Now, I don't know of a single lava flow at Kīlauea that would be fine and even-enough grained and free of vesicles in order to be a good parent material for making stone tools. On the west side of the caldera, there are more than 100 workplaces that have been found by archaeologists where Hawaiians chipped away at fine, evenly grained thermally-metamorphosed ballistic blocks that were thrown out. And they didn't use lava flows, they used these ballistic blocks that had been thermally metamorphosed for their tools.

 

Here, I can't imagine lava flows in the walls of Keanakāko’i being good enough for tool making. Now it could have been that there were some intrusive rocks down there, fine dikes or sills that they found, that's a possibility. The other possibility is that there could be ballistic blocks in this area—and I’ve shown you some of the ballistics—that were found by Hawaiians to be good parent material for stone tools. So this could have been an area around the crater that had these good rocks and so the crater became the site of the adze. Or there could have been some blocks that fell into the crater for that matter, we just don't know. So this is something that we’ll never figure out, I don’t think, because there's been enough filling in of the crater since the area was being used for tool making. We just don't know, but I'd like to raise the issue with archaeologists that it's not entirely clear as to exactly what's going on here.

 

Now as you can tell from looking at the crater and what we've seen around here, this crater must be a collapse feature. Just as the caldera is a collapse feature. So, the pit craters are collapse features. The alternative is that these features were formed by explosions. Now there are explosion calderas, and one of the best known ones is was Crater Lake in southern Oregon, where the material that was erupted from the caldera has about the same volume as the caldera itself and so this suggests that the caldera formed because of material that was exploded. But around here in Hawai`i you just don't have evidence of explosive activity around calderas and craters. You would expect a raised rim around the caldera or around the craters and you don't see them. So that's the evidence that these are collapse features.

 

It's not entirely clear what the features collapse into but I subscribe to the old view that they collapse into evacuated magma reservoirs, just like Halema‘uma‘u collapsed into the partly evacuated summit reservoir [in 2018]. But there are other hypotheses, as well. So this is the last eruption, the most current/recent was in July of 1974, that's the same date for the spatter rampart that we looked out at. In fact, the eruption sort of began here, and then migrated into the caldera as well as migrating down the east rift connector down to Luamanu into that area. So it's quite an interesting, interesting eruption.

 

So with that, this is the end of a formal trip. I'll walk slowly back. If you want to hear a story at the end, go ahead of me and then just stop at the gate. Wait for me to catch up at the gate and I’ll tell you a story that sort of puts the icing on the cake.

 

 

In late May and into June [2018], we were having once or twice a week evening meetings with the people who lived in Volcano Village. We’d meet at the Cooper Center and [National] Park [Service] people and sometimes county people/USGS people. After one of those meetings I'd given a presentation and I told people that I was sitting at a dining room table in the Volcano House Hotel, looking across the rock wall, watching what was happening in the caldera.

 

After the meeting, a Hawaiian woman came up to me. I didn't know her, and she asked me, “Don, could you do me a favor?” I said, “Well, what is it?”

 

“Could you put this Koa false leaf on top of the stone wall in front of the dining room for me?” She had collected it from in front of KMC [Kīlauea Military Camp] and I guess had pressed it, and I said “Sure.” So she gave me this Koa thing.

 

Well, the next morning I arrived at the dining room and had forgotten about it. I'm sitting there and then I remembered. I went back to the car and got the false leaf and I put it on the rock wall, put a couple of small pebbles on top of it to keep the wind from blowing it away. I took two or three steps back towards the stairway that went in the dining room, and we had one of those 5.3 earthquakes. It was strong, I grabbed on the railing of the stairs. It was really shaking like mad.

 

After the next meeting, this woman came up to me and said, “Don, did you put out the Koa thing for me?” I said, “Yes” and then I explained to her what happened. And she said, “I have chicken skin. I have chicken skin from this.” And then after the third meeting, she came up to me and said that she told some of her friends that story, and they got chicken skin too.

 

To me this really illustrates the importance of how Pele can be important to some people, to some Hawaiians. The offering was for Pele and Pele was responding by the earthquake. And to me that kind of illustrates in a microcosm how important the volcano is to a certain segment, probably a fairly large segment of Hawaiian culture today.

 

So that's my story. I think it's kind of a nice one.