At a public talk in Pahoa, Hawaiian Volcano Observatory Deputy-Scientist-in-Charge Steve Brantley gave a 10-minute talk on the 2018 Kilauea eruption sequence so far.
I was going to summarize it in my June 6 Kilauea daily digest. However, it’s so useful I’ve transcribed it in full below.
The full community meeting is archived here, with Steve Brantley’s presentation starting at 44:30. BigIslandVideoNeed has excerpted it below, but they don’t usually show the slides he was showing. I’m going to be putting those back in, matching or approximating the photos he selected.
Steve Brantley, HVO/USGS: “Good evening and thank you for coming out tonight. […]
“I started my day this morning visiting the Volcano Observatory. I haven’t been at my normal place of work for about a month. And I think most of you know that the summit of the volcano has experienced many thousands of earthquakes in the past 4 or 5 weeks. It was a remarkably clear day at the summit. And I was extremely humbled to see the changes that had occurred at Halema’uma’u in the past several weeks— and actually, just in the past several days, based on some earlier photographs.”
“And I’m also equally humbled to be here before you tonight to talk about what’s been in your face and in your lives for the past several weeks. I’ll try to be brief, and just provide an update of what we think we know about the eruption and the eruption status.
“So in overall summary…
“This is a cross-section through the volcano that I’ve presented before, showing you the cutaway from the summit area, Halema’uma’u, and all the way down through the Lower East Rift Zone to the eastern tip of the island.”
[Powerpoint Bullet points on screen below this slide:]
- Activity at summit & LERZ continuing
- No sign of slowing or acceleration
- Continued changes are expected
“This whole sequence started on April 30, when magma withdrew from Pu’u O’o, and magma then began a march down into the Lower East Rift Zone, and within a few days, the first eruption started in Leilani Estates [May 4].
“Then there was a large magnitude earthquake, 6.9 [May 4], beneath the south flank of the volcano. And that earthquake resulted in the movement of the south flank of a couple of meters, and may have opened up a little bit of space in the rift zone to allow magma to move into it.
“And so just after that earthquake, the summit area began to subside, and the lava lake disappeared within a few days, went out of sight.”
“And at the same time, the overall surface at the summit subsided. And now it has subsided over three feet, and in some places right adjacent to Halema’uma’u Crater rim, it subsided 15-20 feet. And I’ll show you some pictures at the very end (Talmadge [admin of HI Civil Defense], I ask for your patience; I’m going to show a few more than you asked me to) so that you can get an idea of the scale of what’s happened up at the summit.
“So an overall picture is that the activity at the summit is continuing, and so it is in the Lower East Rift Zone.”
[ Slide on screen shows 3 bullet points:
• Activity at summit & LERZ continuing
• No signs of slowing or acceleration
• Continued changes are expected ]
“We don’t see any change in the vigor of the eruption. It’s not slowing down. It doesn’t seem to be accelerating. It’s continuing at both locations. And so just based on that, and based on what your own experience in the past few days to a week, we can continue to expect to see changes both at the summit, maybe more dramatic changes, and also continued eruption here in the Lower East Rift Zone.
“So this is a view of Fissure 8 from this early morning.We’re looking pretty much right into it.”
[Caption on this slide in Brantley’s slideshow: “Fissure 8: high eruption rate (early June 6-9 mcm/day = > 15-25 times Pu’u O’o long-term eruption rate”]
“The eruption rate has been fairly high. In early June, we were able to make some measurements of the lava channel spreading away from Pu’u O’o— excuse me, from Fissure 8, and by doing some calculations, we think that somewhere between 6 and 9 million cubic meters per day was spreading away from Fissure 8. And that would explain the rapid advance of the lava flow over the past week.”
“And just for comparison, that rate is on the order of 15-25 times the eruption rate over the 35 years of Pu’u O’o. So if you think there’s a lot more lava coming out of the vent now, you’re absolutely right.
“This lava spreading from fissure 8 has formed a very pronounced lava channel that’s extending off to the east. And the important point here is that the lava channel has become kind of elevated above the ground, and there are levees created alongside that lava channel.”
[Hawaii County Fire Dept photo, June 2]
“And so one of the concerns is that those levees or part of the levee can fail, can slip away, and if that’s the case, you can see all of the lava that’s sitting in here— and if it happens to fail in the right place, that can become a new lava channel. It can drain the lava out of the main channel and go into that side levee. So that’s one of the things that we try to monitor, keep track of, if we see seeps or small drains. But those levees can fail rather quickly and suddenly.”
[Hawaii County Fire Dept photo, June 2]
“So the lava flow spreading from fissure 8 has entered the ocean in the past couple days as we all painfully know. And it’s continuing to supply lava through the channel and to the lava entry area as of this afternoon. This will probably result in the intermittent laze plumes that will be blown downwind depending on which direction the wind is blowing.”
“So, an overall map showing Fissure 8 right here in the center, the lava channel, and the flow going into Kapoho Bay.”
“One of the things that we’re going to be doing and have been doing for the past several weeks with our field crews working 24/7 out in the field and also when we do our helicopter flights and our drone flights is to track the area uprift [WSW] of the main fissure complex across Highway 130 and just a little bit uprift.
“And what we’re trying to do is monitor those ground cracks that many of you know are there, and you see steaming, and have been plated over. And so far, we’ve noticed a little bit of increase in temperature, maybe a little bit of widening, but no substantial widening across that part of the rift zone.”
“And if you remember, a couple weeks ago, when lava really began pouring out of the ground, the ground cracks appeared, and within hours, they deepened, they widened several meters, the whole ground above the rising magma dropped. So that’s the kind of warning that we’ll all have, if the magma that’s beneath Highway 130 area begins to rise towards the surface. And that can happen very quickly, within an hour or two. And we may not be actually there when that happens, if it happens, but it’s one of the things that we’re trying to keep an eye on.”
“Okay, so two more slides. I wanted to show you some dramatic changes that have occurred up at the summit of Kilauea and Halema’uma’u Crater. This is a view, 2009. It’s a sort of shaded relief map, you might say, of the crater. This is the lava lake as it appeared in 2009. [left] And this is about 1 kilometer in diameter— it’s about half a mile. [right] And this is an image put together based on some satellite data from June 1, so, a week ago.”
“And you’ll notice that the little vent here has gotten quite large. And the more important thing is that there are circumferal fractures out here. So as the magma withdrew from beneath Halema’uma’u, the crater floor dropped and now is a rubble-filled depression, and it’s continuing to grow outwards.”
“This is a view taken from just this afternoon. We’re looking toward the west. And if you’ve been up there before, this is the Halema’uma’u parking lot. And this used to be the overlook where you could walk up and look down into the crater. That overlook has fallen into the crater. This is the original crater floor right here. But some of these features that you see here, including this big scarp back here, this one, are all new.”
“So as the magma withdrew, the crater floor subsided. And as it subsided, there have been earthquakes. And this is my last— well, here’s a— over 3,000 earthquakes occurred in the summit area in the past week.”
“And if you look at a sequence of these earthquakes in time, earthquakes per hour, since May 28, you’ll see that there’s a change in the frequency of the earthquakes over time. And the important point here is that— you’ve heard about the explosions that have occurred up at the summit? When those explosions occur, it’s right at this peak, here. [points at one of the spikes on graph, just before dropoff to right.] ”
So when there’s an explosion, the earthquakes drop off dramatically. Over a period of 30 to 50 hours, the earthquakes build back up, and then there’s another explosion, and probably is accompanied by the additional collapse of the ground up at the summit of the volcano.”
“So what’s happening up there is very closely related to what’s happening down here. We think there is a connection, although my colleagues argue about it for hours. There’s a lot of details that we don’t know about. But that’s the state of things as we know it. Thank you for listening.”
ADDENDUM (— Ellen, transcriber). I’ve had the Kilauea summit livestream open in a spare window. Most of the day it’s been fairly easy to see across with just a white plume, probably steam. For example, I took this screengrab from the still webcam about 4 hours ago:
But in the past…fifteen minutes, at least? I haven’t been watching the livestream closely… it seems to have a plume of what looks like ash. Wanna bet another explosion happened while I was typing?
Manual screengrabs over about 12 minutes…
At this point a vigorous poof of white steam came up from inside the rim closest to camera. (Did a bit of the wall fall in, or is just reacting to a quake?)
BINGO!!!! 5.6, 4:06pm.
About half an hour before I noticed, whups.
(I’m on PST, and the quake monitor page is apparently displaying times in my own timezone, so subtract 3 hours to get Hawaii time.)