July 6: Living With the 1% Possibility of Caldera Collapse

USGS, July 6, 2018. Dawn at Fissure 8. (Full-sized)
Today’s Eruption Summary

The Lower East Rift Zone eruption continues pretty much as usual: Fissure 8 feeding a lava river with occasional short-lived overflows. The main lava channel no longer reaches the ocean, but crusts over a half mile from shore and dives into the lava delta, oozing out at multiple points on the northern side. One especially large “ooze-out” makes a short flow on the north side of the flow field near the last few Kapoho Beach Lot Houses, a few of which are hanging on. Fissure 22 is weakly spattering with a weak flow to its east. Today’s summit explosion occurred at 6:04pm, equivalent of M5.3. Thick fog obscured the livestream view.

July 6, 2018, USGS. Ocean Entry at Kapoho. (Full-sized)

So that’s all routine, if a volcanic eruption can ever be routine. The big news today actually took place last night (see what happens when I finish my posts early?):

July 5 Volcano Community Meeting

Thursday evening, there was an important community meeting in Volcano Village. Mayor Harry Kim, the USGS and Civil Defense outlined the extremely unlikely but potentially life-threatening (to people near the summit) possibility of large-scale caldera collapse. I’ve transcribed the meeting here. BigIslandVideoNews excerpted the crucial 4-minute presentation from HVO’s Tina Neal:

Preceding this meeting was a long-expected document from USGS: Volcanic Hazard at the Summit of Kīlauea UpdateWhile the Kīlauea Summit Earthquakes FAQ explained what is happening, this new update to a May 8th report summarizes what the USGS thinks might happen at the summit before this sequence is over, based on the volcano’s distant past.

During the Q&A session, a resident asked about the odds for the worst-case scenario, a large-scale caldera collapse with explosive activity. Harry Kim took the mike from Tina Neal and said, “Like you, we always like to know percentage odds. And she knows; I asked her that. And I’d like to answer because she said, ‘One percent.'” [Tina went on to explain how they arrive at such probabilities; she wasn’t being flippant.]

Another reassuring quote from the Q&A session:

Don Swanson: “I think that the evidence we have today looks to me as if [the subsidence/collapse] is going to be confined to within the caldera, because the outermost circumferential fractures that have been occurring on the caldera floor have not extended outward in the last 2-3 weeks or so. So to me, that suggests that they may be defining the outermost limit of potential caldera collapse.”

USGS: “The WorldView-3 satellite acquired this view of Kīlauea’s summit on July 3. Despite a few clouds, the area of heaviest fractures in the caldera is clear. Views into the expanding Halema‘uma‘u crater reveal a pit floored by rubble. HVO, on the northwest caldera rim, is labeled.” (Full-sized)

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July 5: Volcano Community Meeting

Informing the public without panicking them about an extremely unlikely but life-threatening hazard is tricky. So it’s taken the USGS a while to release this document which they’ve been promising the residents of Volcano:

On HVO website: Volcanic Hazard at the Summit of Kīlauea Update [summary: “This document is a guide for understanding current activity and hazard at and around the summit of Kīlauea Volcano. Here, we summarize activity from late April through the present, detail possible future outcomes, and review hazards associated with these outcomes.”]  Presumably it’s called an “update” because it supplements the June 26 “Frequently Asked Questions About Kīlauea Volcano’s Summit Earthquakes” FAQ. [EDIT: No, actually, it’s an update to the May 8th “Preliminary Analysis of Current Explosion Hazards at the Summit“]

This was the chief topic of Thursday’s Volcano Village meeting, led not by the National Park Service this time, but by Civil Defense Administrator Tal Magno.

Here’s the FULL video of the meeting. BigIslandVideoNews excerpted the most important part, HVO Scientist-in-Charge Tina Neal’s 4-minute talk:

Partial Transcript

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