June 11: USGS Press Conference (Halema’umau Subsidence, Ocean Upwelling)

At a 3PM press conference, Jim Kauahikaua (USGS geophysicist) described in detail the subsidence at Halema’uma’u. He also talks about a patch of “upwelling” where lava has entered ocean at Kapoho and seems to be traveling along ocean floor, heating water above it.

(Transcript below the cut)

“So, Jim Kauahikaua, US Geological Survey’s Hawaiian Volcano Observatory. Fissure 8 is still very active. Fountains are up to 180 feet and also as low as below the cone which is about 115 feet above its base. We’re just wrapping up— there was an explosive eruption this morning, of course, just before 5 o’clock. Seismicity’s ramping up for the next one. Hard to say exactly when that’ll be, because it’s become a bit more variable than normal.

“We also have some new information about the subsidence of the summit crater. Parts of it appear to be moving towards the crater and subsiding rather rapidly. The north rim of what was formerly Halema’uma’u, the old Halema’uma’u Crater, has dropped as much as 40 yards vertically, and moved towards Halema’uma’u— so it looks like it’s sort of slumping in, along with the piece that was slumping in from the west earlier. Let’s see.

“So lava’s— just to jump around a little bit—lava is flowing through the channel; it’s fairly full, but it hasn’t spilled over today, as far as we know.  [Unintelligible] the ocean entry, which is simply a point entry right now, it’s got a fairly large upwelling offshore, directly offshore of the entry.
“Some minor activity at fissure 16/18 still. And I think that’s it.”

Q: Can you explain upwelling, especially for folks interested in going out on the lava boat tours, who wonder if that’s an inherent additional risk? 

A: Additional risk, you mean, to being out there in the first place? (chuckles) Yeah. The upwelling, we think, is due to lava flowing on the ocean floor, so it’s hot in a relatively cool medium. We think it probably sets up a convection cell right over the lava flow, and when you’re out there you can see this patch of relatively calm water that’s somewhat circular or elliptical. Right at the moment it’s splitting the issuance of colored water, if you will, the stuff that has, you know, the fine black sand particles in it. The upwelling is right offshore to two very distinct colored patches of water that are flowing off the entry, around it [the upwelling]. Is it a greater risk? It’s a little bit cooler than the patches of water around it. It’s not a huge circulation thing, you know, so it probably won’t affect boats— but I’m not a boat person, so I can’t really say that.

Q: Could you go over again the rim of Halema’uma’u, how it’s being reshaped? What’s the significance?

A:  Well, we’ve been talking about the subsidence of the summit for quite some time. It’s been going on for weeks. It appears to be accentuated by the explosive eruptions, but in general there’s a background of the crater’s collapsing. The edges are coming in a little bit. The floor is subsiding. Parts of it are subsiding rather rapidly. The 100-120 feet or so, 40 yards of subsidence of the north rim is probably of a block that’s moving towards the big puka inside Halema’uma’u, the big hole.
That hole is about 1000 feet deep from the rim of Halema’uma’u. But the rim of Halema’uma’u itself is probably deeper than it was pre-event. So it’s sort of a massive collapse. I would say that’s pretty significant. And on top of that, there are these multiple explosive events. There have been 22 so far. They seem to be settling into somewhat of a pattern, but I hesitate to say that because it’s the death-knell of patterns, usually.

Q: Is it conceivable that it could all become, you know, the puka could just become the whole thing? 

A: Well, right now, the collapse is consuming the edges of Halema’uma’u itself while the floor of Halema’uma’u is progressively dropping. So that about half, roughly half of the floor of Halema’uma’u has fallen into the crater. The western remnant part seems to be sliding into that hole. And now it seems clear that the northern part is also sliding into that general vicinity. So this is a major landscape change, if you will, and a big change for—

Q: A significant change to the greater Kilauea Caldera floor adjacent to Halema’uma’u as well? 

A: Yes.

Q: Any immediate potential impact to Jaggar and to the HVO headquarters that sit right on the edge there?

A: Uh, well, HVO building has been affected by this general subsidence. I’m not sure about Jaggar Museum.  I know that there’s been cracking on the overlook, but that’s about it— that’s all I know, not that that’s all there is.

Q: There was talk this morning about the increased SO2 levels and what that might indicate?

A: Well, the increased SO2 emissions in the Lower East Rift Zone is probably due to an increase in eruption rate. The two kind of go hand in hand. It’s become a little clearer what’s happening at the summit, and it appears that the overall emission rate in between explosive eruptions is a little bit lower than what it was pre-eruption, but then during each explosive eruption the emissions become higher for a brief time. So overall, it’s a lot of SO2 coming out. And it’s in such a way that the trade winds kind of collect it all together as it goes around [Aleau?] and Pahala and Oceanview Estates and Kona, ultimately.