On June 26, 2018, Deputy Scientist-in-Chief of the Hawaii Volcano Observatory, Steve Brantley, gave a ten-minute slideshow at the Puna Community Meeting in Pahoa. Video of the meeting is posted here. Steve Brantley’s talk starts at 35:00 in that video.
BigIslandVideoNews excerpted half of his talk in this video, which they overlaid with footage from a June 24 USGS drone overflight of the summit:
Below is my transcript of the complete talk, including images that match or approximate his slides.
Steve Brantley (USGS):
Hello, everybody. Thank you for coming out.
I’ll just describe a few things occurring in the Lower East Rift Zone and then summarize the activity up at the summit at the very end.
Before I do that. Because the lava flow channel and entry area have been relatively stable for the past few weeks, we’ve reduced the number of helicopter overflights that we do every day from, ah— I’m afraid there’s still dozens more by visitors— from 3 a day to 1 a day. So we just fly in the morning, and so you may have seen fewer images on our website to show you what’s going on out there. But we’re still staffing the field crews 24/7.
So we run three different crews, 2 or 3 people on each crew, and just tonight— last night, we started utilizing and working more closely with Department of Interior drone crews that are here and supported by FEMA, so that we can reduce the number of people we have all night. It’s getting a little hard to track the channel, especially at night, because it’s so long, and access is a little difficult.
Okay, so this is this morning’s view of Fissure 8, the small, uh— short, tall? — small [they’re not really small. but they’re not as tall as they were, no longer rising above the cone very often] lava fountains inside the growing spatter and cinder cone. The lava channel’s been relatively full for the past week. There’s a little bit of fluctuation that happens, but not very much.
So there’s still a high discharge of lava from Fissure 8. And it’s flowing in an open channel all the way to the ocean, as you already know.
In this image, you can see a little bit of a few overflows, these little gray patches here and here. There’s a little bigger one right here [back close to the fissure, just past the rapids] that overflowed and went to the edge of the original flow. These kinds of overflows don’t last very long, an hour to three hours perhaps, and you can see there’s not very much volume there.
One of the other things that we’re looking for, that is a little bit more of concern if we were to see them, are things that we call “seeps.” And these are… dense lava that we’ve observed in earlier lava channels back in 2007. And these seeps would exit out toward the edge of the lava flow. So it’s lava from the channel that’s somehow making its way down through the sides of the perched channel, and then coming out to the side. And if you get a very large one, it can sort of wholesale take that whole side with it. So that’s what we’re really looking for, and we’ve only seen one, so far, and it’s very, very slow-moving, and didn’t present a danger or a potential failure at that time. That was a little bit earlier this week.
So so far, the channel’s remained very stable.
I mentioned— this is an image from the drone crew that we’re working with, so we’ll be working with them this coming week to see how well we can work together and minimize some of our people’s time out there. But it increases their time.
This is a photo from this morning looking across toward the open lava channel.
The ocean is up here [blue-gray hazy area on left side of horizon.] And there were a few little seeps coming out of the a’a flow. Not very strong, very short-lived, but those seeps can still happen out toward the edge of the a’a flow toward the ocean.
The lava entry was spread out over a pretty broad area this morning. There’s a main channel that enters the ocean, and then there are these breakouts occurring from within the flow, and were pretty spectacular this morning.
So the lava entry does change from day to day. Sometimes there’s more than one entry; sometimes just one; sometimes they’re spread out like this over a wide area.
So what I’m going to do here is show a sequence of the way in which the lava entry area has grown or moved in the past couple of weeks.
We’re starting with a map of June 8th. And the red here is showing you the changes between June 8th and June 6th or June 7th, in terms of the addition of new land to the island. And if we go ahead here, we’ve got June 15th…
I’ll go back to June 8th. June 15, and you notice how it’s spreading out to the south.
And then to June 26. And so this is something that we’ll track. We’ll update the maps, and you can see— you’ll be able to track that to see if the entry area continues to move to the south, or maybe it’ll move back inland. And this morning the main entry was up this way [labelled on map], so not directly to the south.
Ok, up at the summit…
Halema’uma’u continues to grow larger as more of the adjacent crater floor slumps inward. And this is all related to magma that’s withdrawing from beneath Halema’uma’u and going into the volcano, into the East Rift Zone most likely.
It’s really hard to get a sense of the scale of what’s occurring up there. We have some instruments on the crater floor up there that show during these collapse explosion events, that these instruments are dropping 1.5, almost 2 meters, so, up to 6 feet in one drop. And then they’re also moving toward the center of Halema’uma’u.
I showed you this figure a little while ago. It’s a plot of the collapse volume of earlier collapses on the lefthand scale, and time [X-axis]. Here we are, 2018, early in the eruption [laser pointer indicates dot at bottom of arrow]. Now— we were there last week [indicates top of arrow].
[Now] the area has lost even more volume. These numbers kind of change a little bit, so it’s not actually doubled in just a week. The way we do those calculations and so on, we continue to refine them, and so this is just a larger number.
It’s… almost 400 million cubic meters of volume has been lost at the summit, and that’s about 13 million cubic meters a day. So we’re still losing more and more material as the magma withdraws down deep.
As a consequence of the faulting and the slumping, there are lots of earthquakes. This is a map showing you the earthquakes just in the past seven days.
The number up there is about 4,400 earthquakes. If we just look at the magnitude 3 and above earthquakes, there have been about 290. And the larger circles here are the… earthquake locations associated with the collapse explosion events. Those are the magnitude 5.3, 5.2 events.
So in the past week, these have occurred about once a day.
This is a weeklong plot showing you the hourly earthquake counts, and you can see that the counts vary. And the quiet time in between here [one of the troughs] happens just after one of these collapse explosions events. So after the ground just— phhhht [motions] — drops, the volcano kind of takes a little bit of a breather, but the magma’s still withdrawing.
So as it continues to withdraw, it loses support of the material that just dropped, and so then things start to drop a little bit at a time. You start getting more and more earthquakes. It builds up to a plateau here [top of one of the peaks] and continues for a while, 12 hours or so, or more. And then the thing drops again.
So what does it look like when one of these events occur? Early on, we talked about ash plumes forming, and some of the earlier ash plumes went up to 20,000 feet perhaps, a little bit higher.
So this is a view of the crater area yesterday afternoon, mid-afternoon. Not much of a plume coming out of Halema’uma’u, which is located right here.
And then, this is what one of those collapse explosion events is now producing that you can see visibly. It’s not very much. It’s a white plume rising here, from this part bof the crater. There’s— you see it’s a little colored, so there’s a little bit of ash, primarily from rockfalls. There’s also a little extra volcanic gas, sulfur dioxide gas mixed in with that.
So because we’ve had several of these events producing very little ash and very little height gained in these plumes, this past week we lowered the aviation color code, the sort of threat code, from RED to ORANGE, which is where it’s been for the last ten years or so.
So at this point, we’re waiting for another seismic event to occur. It can occur at any minute. The last one occurred yesterday about 5:07, so just 24 hours ago. So [raises hands] the next one is going to happen at any time.
[It happened at 10:41pm.]