July 17: Steve Brantley USGS Talk at Pahoa

Here’s a transcript of this week’s presentation from HVO Deputy-Scientist-in-Charge Steve Brantley at the Tuesday Pahoa Community Meeting.

I’m going to start with a broad overview of the eruption so far. We’re 80 days into the eruption [since the floor dropped on Puʻu ʻŌʻō, I think] about now, so I want to provide a little bit of context, in terms of similar activity or un-similar activity in the past 200 years. And then we’ll do a quick summary of what’s happened in the past week.

So the main message is that what we’re observing now is unprecedented in the past 200 years in terms of size and scale, but not in terms of process. This has occurred before, particularly during the 19th century, where there were multiple collapses of the summit area and eruptions down in the East Rift Zone— at least one large one in 1840.

So at the summit— [glances at slide] I just said that.

This is the largest sequence of collapse that we’ve observed in the past 200 years.

In the Middle East Rift Zone, you remember Puʻu ʻŌʻō. Puʻu ʻŌʻō erupted for 35 years. That was the longest-lived eruption in the whole East Rift Zone in over 500 years. And it probably set up the conditions that were ripe for magma to be able to travel underground all the way from the summit out to this area.

And then the Lower East Rift Zone: this is the most voluminous eruption in the past 200 years. It’s the highest eruption rate that we’ve measured for Kīlauea. It’s many, many times larger or higher than the eruption rate for Puʻu ʻŌʻō. And that’s why there’s just so much darned lava pouring across the ground every day, every week.

And also, the emission rates of sulfur dioxide gas are very, very high. And they’re the highest that we’ve ever measured for Kīlauea, and that is creating quite a bit of poor air, to say the least.

So this is a summary of the dates and lengths of time and volumes of eruptions that occurred in 1840— it lasted for 26 days, erupted about 205 million cubic meters. So the exact number may not make that much difference, but look.

In 2018, so far, we’re 80 days into the eruption, and we’re on the order of maybe 450 million cubic meters that have been erupted. So this is about equivalent to 8 ½ million cubic meters every day, 8-10 million cubic meters. It’s just incredible to try to imagine that much lava coming out of the ground. But… so it is.

In 1955, the eruption lasted 88 days, and produced about 81 million cubic meters. These are all estimates, of course. We don’t have an exact volume. 1960 was 37 days, and 122 million cubic meters.

Clearly, this activity now is unprecedented in the past 200 years.

Ok, so in the past week, there’s been a little bit of channel modification down by Kapoho Crater. It was about a week ago, on July 10, that the channel became blocked just upstream of Kapoho Crater as sections of the levees broke off, floated downstream in the lava channel, and then basically kind of blocked when it—  they kind of got stuck in a narrow area. So that led to a backing up of lava, a filling up and overflowing of the channel, and within a couple of days, that resulted in a new channel completely going to the west of Kapoho Crater, through there:

So it took a more direct shot— in fact, somebody last week asked me, “Why doesn’t the lava just take a straight shot and go right down to the coast?” Well, it did.

So we haven’t seen any lava flowing in the old channel out through here [can’t see pointer but presumably somewhere along or past left-hand arrow] on the surface, but clearly lava is making its way through that part of the old flow, because you can see the steam rising along the edge of the coast. Some of these areas up here. So there’s a little bit of lava still dribbling into the ocean here and there from either the old flow that’s thick in the a’a flow, still molten core probably, or maybe some lava’s making its way beneath the surface that we just can’t see.

[Bruce Omori photo from July 16, same location as slide below]

This is a little photo taken this morning with some sketches. And right at the junction where the original channel went…

[Slide moves down to reveal “original channel” and arrow, laser pointer indicates area just to the right of word “Ahalanui”]

…there is still a little bit of overflow activity. So the situation is a little bit tenuous, and it wouldn’t be a surprise if there were additional overflows, and maybe the channel finds its way back in the old channel, or finds a new path somewhere. So that’s an area that we’re trying to track pretty closely with our overflights, and also with the use of the drones during the day and the evening.

[Not quite same photograph, but close:]

Not a very good photograph, but I wanted to show you, this is the ocean entry. On Saturday, it was about 950 meters from the Isaac Hale Park where the boat ramp is. Today it’s about 750 meters from the boat ramp. So it’s moved just a little bit in the past few days. Not as a main direction of flow, but as a lateral spreading on the south side of the open channel. So there is where Isaac Hale Park is located, right there, and you can see where the active lava is, with the white steam plume.

This is a photograph taken today about noontime from the 1960 Kapoho Cinder Cone, and we’re looking toward the active ocean entry, and you’ll see there’s quite a bit of vigor in the plume, the white plume in the background. And this may be similar to the kind of activity that occurred yesterday [littoral explosion that hit the lava tour boat]. This doesn’t look quite as strong as that activity.

And the mechanism for causing those explosions like what occurred yesterday is not really understood or known. They’re occurring offshore a little bit, but you can’t actually see what’s triggering it, but it may be related to lava from that open channel entering the ocean, forming a surface over it[self] that’s sort of a tube, that allows free flow of lava great distances down the submarine slope, and perhaps there was a failure of the surface of that lava tube or some sort of s calving effect that damaged that and led to the quick, sudden interaction of a lot of lava and a lot of water.

But the scale of the lave entry is so much greater than what we are used to seeing during the Puʻu ʻŌʻō activity, when lava sort of dribbled into the coast, a few cubic meters a second. This is on the order of 50 to 100 cubic meters per second. So much, much greater volumes and a higher rate. And so the extent of the hazards might be a little bit greater as this thing unfolds. That is along the shoreline.

This is a sequence of images that’s showing you the last couple of weeks, that’s showing you the advance of the ocean entry and the spread to the south.

And this was taken today— uh, the map was made on July 16.

So it’s still about 750 meters from the boat ramp.

Okay, just a few slides for the summit. Activity there is still continuing as usual. We’re waiting right now for another summit collapse explosion even that should happen at any minute or any hour now. And during each of those events, the inner part of the crater floor drops in some sections 2 to 2½ meters at a time.

And what I’m going to show you is a Digital Elevation Map that was made back in 2009.

#lidar DTM of Kīlauea caldera and Halema`uma`u Crater in June 2009. Data from 300 sq km NCALM survey available from OT: https://t.co/sYBIoXVZ9l #KilaueaEruption #Kilauea #hawaii pic.twitter.com/8762hyivWf

— OpenTopography (@OpenTopography) May 10, 2018

This is Halemaʻumaʻu [circles inner crater with dark green floor, although his slide was a greyscale version of this same model.]. And the little circle there [white spot on SE side of Halemaʻumaʻu’s floor] is the lava lake back in 2009.

And this is the same scale Digital Elevation Model produced from a series of helicopter overflights on July 10. So we go back and forth a little bit. [Flips between two. Unfortunately slide projector screen was moving slightly; between that and the distorted angle it’s just not worth my fighting it to try and make a gif.]

So, 2009, and here.

This is the part of the crater floor that’s dropping [outlines outer oval on caldera floor surrounding Halemaʻumaʻu] that 2½ meters or so every time there’s one of these collapse events almost every day. They’re averaging a little bit longer, 27, 28 hours, something like that.

Okay, I showed you this plot a number of weeks ago.

and it’s trying to capture the size of the collapse in terms of millions of cubic meters. Here’s zero to six hundred [y-axis] . When we started out, we were down here in 2018 [indicates lower point, can’t remember exact #.]  And now we’re up here, and actually you have to add another 90 million cubic meters, because it’s losing about 13 million cubic meters every day. And this was made from data from a week ago.

So clearly this collapse is quite large, and maybe next week I’ll try to see if I can get some slides to show you some of the sketches that were made of collapse events that have occurred when westerners visited the summit area in the 1800s.  And these collapse areas were in different locations and much further to the north than the current collapse.

So, so far it’s on the same process, magma draining away from the summit reservoir and entering the rift zone, and then the overlying material [of the caldera area] doesn’t have any more support, so it collapses into that reservoir, and probably will keep going until the magma reservoir stops draining away.

Thank you.