Thursday 1 pm USGS briefing to media. Most important part of briefing:
Full 1/2 hour audiofile here.
- Leslie Gordon, USGS Public Affairs
- Janet Babb, geologist, USGS/HVO
- Patricia Nadeau, geochemist, USGS/HVO
- Jessica Ferracane, Hawaii Volcanoes National Park
- Matthew Foster, meteorologist, NWS
Janet Babb, Kīlauea Update: Good afternoon, everyone.
On the Lower East Rift Zone, Fissure 8 is still active. It continues to erupt lava into the perched channel that extends down on the west side of Kapoho Crater and feeds lava into the ocean. This morning, the main ocean entry was a little bit west of Ahalanui, with the flow margin about 500 meters, or 0.3 mile, from the Pohoiki boat ramp. There’s still some weak ocean entry points to the north of this main entry over near the Kapoho Bay lobe of lava where there were some weak, wispy plumes there. The flow front along the ocean, along the coast is still about 6 kilometers wide or 3.7 miles wide. On the Lower East Rift Zone, the sulfur dioxide emissions remain high, and the ocean entry hazards include the laze plume, as well as the possible hydrovolcanic explosions, what we referred to on Monday as “littoral explosions.” Hydrovolcanic is a little more intuitive word to explain the lava-seawater interaction.
Up at the summit, as we speak earthquakes are occurring at a rate of about 25-30 per hour as the volcano builds up to the next collapse event [this phonecall at 1 pm, collapse came at 4:33 pm.] The previous collapse event weas at 1:28 am July 18, so it’s been about 36 hours. We are within that time interval where we typically see these collapses occur. At the summit, the sulfur dioxide emissions are low. We’ll be posting some new photos and a new map shortly after this media call. That’s all.
Jessica Ferracane, NPS: Aloha and good afternoon everybody. I don’t have much new to report. It’s almost ditto of what I reported last Thursday. Today is day 71 of the closure, and damage continues to happen to the park infrastructure on a daily basis. There’s a lot of sinkholes as the ground-fill on trails and roads and overlooks in the park fall away. It falls away due to the subsidence at the summit. [Ranger talk Thursday, artist-in-residence Friday morning]
Matthew Foster, meteorologist, NWS: [Dry and stable trade winds Thurs, dropping to moderate speeds over weekend. Moisture moving in late Sunday through first half of the week, showers possibly enhanced over lava area. Late Sunday, Monday, winds shifting a bit east to blow vog west, but shifting back to NE by late Monday, Tuesday.]
Q: [More info about Thursday night meeting, USGS to discuss scenarios for explosive event. What’s the reason for this meeting?]
Janet Babb: The meeting was organized by the county, and USGS was invited to speak there. It’s similar to the meeting that was held in Volcano on July 5 where there was— you know, there’s been concern about the summit collapse, if it could lead to more serious or more catastrophic activity. And while the probability is quite low, it’s not zero, and so the Mayor called the meeting to talk about what the possibilities are. We do have a document on our website. So if you go to the USGS Hawaiian Volcano Observatory website, on the homepage, in the lower left corner, under the heading “HVO News,” the document is there. And it talks about the possibilities of the scenarios. And so the meeting tonight will be similar. HVO will give a short presentation talking about what’s happening and what the low probability could be. But then my understanding is that also there will be the county speakers talking about the more practical matters of: if there is an ash event, what to do and how to shelter, and keeping roads open, and so on and so forth.
[Note: during the July 5 meeting, USGS told the residents what MIGHT happen and how likely it was to happen (including worst-case scenario), but Civil Defense was in early planning stages and still figuring out WHAT to do about it. Presumably in this followup meeting, CD will have a more concrete disaster response plan for the various possible scenarios which they can pass on to residents. In particular, residents at the July 5 meeting were very concerned about how to know when to evacuate, which way to go, and what to do if some routes cut off.]
Q: Puʻu ʻŌʻō has been silent for two months— is this different from past pauses in its eruption activity?]
Janet Babb: Well, it is different in that we’re not seeing any signs of volcanic activity at Puʻu ʻŌʻō right now, but I don’t know that we’re ready to declare it completely dead and gone, until we see really what takes place with the activity in the Lower East Rift Zone. And so you’re correct that Puʻu ʻŌʻō was the site of activity for 35 years from the time it started in January 1983, up until April 30 of this year when the magma was withdrawn from Puʻu ʻŌʻō and migrated down the Lower East Rift Zone. But I don’t think we’re ready to declare Puʻu ʻŌʻō dead and gone forever because we just really don’t know.
Q: Is Cape Kumahaki still easternmost point of the Big Island?
Janet Babb: I would agree with you that by looking at our map it does appear that point east of Kumakahi is still slightly more east of the easternmost point of the new land that has been created from the ocean entry. That area where the new land extends the farthest to the east, that’s in the area where the ocean entry has slowed down quite a bit that I mentioned this morning. There’s lava still oozing into the ocean up there on the northern side of this delta but not like it is on the southern side, and so it’s really hard to say if it will continue growing and extending out and may become the new easternmost point of the island.
Q: What are risks of Fissure 8 surges? And could Monday’s littoral explosion have been caused by a surge?
Janet Babb: The surges are really more noticeable closer to the vent. And… […] Risks from the surges: if and when the lava channel is at a high level, and there is a surge, we can get overflows over the channel levees. And so that is probably the greatest risk. And then as the volume of lava is increasing, moves on down the channel, you know these overflows can happen anywhere along the channel. Many of these overflows have not extended beyond the existing flow field. There have been some overflows though that have entered into land that had not yet been covered. As far as the relationship between the surge and the hydrovolcanic explosion that occurred early Monday morning, that probably isn’t the cause. These hydrovolcanic explosions can happen at any time. Any time lava enters the ocean, there is potential for hydrovolcanic explosions. There can be this explosive interaction between molten lava, the hot lava, and the cooler seawater. So I don’t think we would attribute that explosion to one of these surges.
Q: What’s relationship between Puʻu ʻŌʻō and current Leilani eruption? Do you have any more understanding of event than we did in May?
Janet Babb: Well, there is some relationship in that Puʻu ʻŌʻō had been the active vent for — or the site of activity for 35+ years, and the magma that had been feeding that vent and supporting the crater floor of that cone drained away and drained into the lower part of the East Rift Zone. And so the magma now that is applied to the summit reservoir— I mean, the reservoir of magma that is fed from the Hawaiian hotspot, is near the summit of Kīlauea, and from there the magma migrates down the East Rift Zone, starting with the upper, through the middle, and down to the lower part of the East Rift Zone. But right now, it’s flowing on through— by Puʻu ʻŌʻō and into the lower part of the East Rift Zone. And that’s where it’s erupting now.
Q: [SO2 emissions in this eruption are high. What are the normal levels, and how do SO2 levels influence decisions about evacuations?]
Janet Babb: So, sulfur dioxide emissions are part of volcanic activity. Any time there’s a volcanic eruption, the three main gases are water vapor, carbon dioxide, and sulfur dioxide. So sulfur dioxide has been part of the ongoing eruption for the past 35+ years. The levels of sulfur dioxide emitted vary depending on the activity. It is common that when a new vent opens, that sulfur dioxide emissions increase. We’ve seen it throughout this activity. In 2011, when the Kamoamoa Fissure erupted, we saw a spike in SO2 emissions. When the summit vent opened in 2008, we saw a spike. And so the pattern is holding true with the opening of the fissures in the Lower East Rift Zone, in the Leilani Estates area, we’ve seen a sharp increase in sulfur dioxide emissions. Because the volume of lava being erupted down in the Lower East Rift Zone is much greater than what had been erupting from the most recent activity, these SO2 emissions have remained high. Oftentimes when a new vent we’ll see an initial spike, and then SO2 will kind of settle down. But down in the Lower East Rift Zone, there’s much more volume being erupted than we saw in the previous Puʻu ʻŌʻō lava flow, and so the SO2 emissions are remaining high.
Now as far as affecting evacuations, the evacuations were initially a concern of the lava flows overrunning property. But yes, the SO2 emissions remain a concern. And depending on wind direction, the area that’s impacted is really dependent on the wind direction. So I will stop there and ask Tricia if she wants to add anything.
Patricia Nadeau (HVO geochemist): I’ll just say before this event started, the emission rates at the summit were the main source of SO2, and we were looking at on the order of thousands of tons per day of sulfur dioxide, whereas now the Lower East Rift is emitting tens of thousands of tons of sulfur dioxide. But back at the summit, emissions have dropped off, so the summit has not remained constant. The summit is now down to just 100-200 tons per day of sulfur dioxide. Puʻu ʻŌʻō remains low. It was in the low hundreds before and it’s down to about 150 tons per day right now.
Q: Thursday’s update says lava is 0.3 miles from Pohoki; will ramp be covered by end of the day?
Janet Babb: There’s no way to forecast that. It really depends on the advance of the lava which as you know can change at any time. It can slow down, it can speed up, it can stall altogether. So we’re watching it closely, and we will continue to update folks.
Q: Why is volume of this eruption so high compared to previous flows?
Janet Babb: Well, essentially, right now, we have magma from the summit reservoir headed down through the rift zone, and there’s more leaving the summit than is being resupplied to the summit area. That explains the collapse of the summit as well as the volume of lava moving down through the rift zone. [Was magma not coming down from the summit reservoir in 1955, 1960, or Puʻu ʻŌʻō? What made it come down from the summit this time?] And as far as an exact reason for why, I don’t know that we have an exact reason why, other than there’s just greater supply going through the East Rift Zone conduit.