Geologists explain the science behind Kilauea Volcano’s latest eruption

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Kilauea Volcano continues to erupt with at least ten fissures observed in the Leilani Estates subdivision in the lower East Rift Zone.

Unlike the Pahoa lava flow in the in 2014-2015 that came from the Puu Oo vent, which has been a long established vent on the East Rift Zone and was basically a new breakout feeding one long pahoehoe flow that moved through a lava tube system, this event is a new outbreak on a different part of the rift tone.

This is a new injection of magma coming to the surface, intercepting the surface at each of the fissures, and each of those fissures can become points of infusion to create lava flows.

What Caused the Current Outbreak?

On Saturday, Christina (Tina) Neal, Scientist-in-Charge of the USGS Hawaiian Volcano Observatory, gave a rough timeline of events:

We know that the Kilauea Volcano plumbing system includes some continuity between the summit magma reservoir which is right below Halemaumau and the rift zone going down as far as lower Puna. So this event began with the collapse of Puu Oo that sent, in a sense, a surge of molten material in the rift zone further down to the lower East Rift Zone.

Some days after that, the Halemaumau lake started to respond and also recede as material was leaving the summit reservoir and also going down into the rift zone and we see that, based on just visually the lava lake going down, but our instruments are also recording the passage of that molten material in the rift zone, so, yes, the answer is they are connected.

The additional material coming down the pipeline literally could involve itself at some point and actually lead to more high volume lava flows. We’ve seen that before historically in 1955, 1960, and other times. So we’ve been saying from the beginning that even though these are small fissure outbreaks which have enormous impact on Leilani Estates obviously, but we’re not seeing big lava flows coming out, yet. But that could be a phase that we move to.

Each fissure is several hundred yards long, officials say, with spatter and lava collecting within tens of yards of the vents.

Scientists with the U.S. Geological Survey’s Hawaiian Volcano Observatory flew over the area Friday. Geologist Janet Babb explained:

“The lava is a spattering from the fissures. A fissure is just a ground crack that the lava comes out of.

They weren’t terribly vigorous. There was certainly lava spattering out of the fissures, at least a couple of them, and kind of piling up. The spatter was piling up um on either side of the fissure. The lava wasn’t flowing very far from the fissure.

This is pretty typical activity when you have an intrusion in the East Rift Zone. This is what happened in 1955. There were breakouts along the East Rift Zone that went downrift. Some went uprift.

So we’re seeing this on kind of a smaller scale in Leilani Estates, where a fissure will open up, then one will open behind it, and then it goes back down so they’re kind of moving back and forth.

Unfortunately, we did see some of the destruction caused by the fissures opening up and the lava. I think that we could confirm that there were two homes that were destroyed, but there looked like there was another one in peril while we were flying.”

Another area with significant activity is Halemaumau Crater at Kilauea’s summit.

Earlier Friday, a massive plume of smoke, ash, and volcanic debris billowed skyward and could be seen for miles. Babb explains the plumes are caused by rockfalls.

“There’s a definite connection between a summit and the East Rift Zone.

What’s happening at Halemaumau is that the lava lake is dropping. As the lava lake drops, some of the support of the vent walls is removed, and so we’re getting a number of rockfalls, and so as the lake drops deeper and deeper, there are more and more rockfalls.

Each time there is a rockfall, it kicks up a dust cloud and so we see this billowing cloud of gas and ash and spatter that comes off the lava lake.

The summit is now noticing that there’s been a change in the East Rift Zone and as far as we can tell, is that the summit is deflating and that means that there is magma leaving the summit, possibly moving down into the East Rift Zone.”

Can We Predict New Fissures?

Volcanic activities can take place with little or no warning. Could scientists have predicted this would happen?

Cracks appeared on roads in and around the neighborhood in the days prior to Thursday’s eruption. Geologists confirmed they were caused by an underlying “intrusion of magma,” but said they were nothing to worry about.

Scott Rowland is a geologist with the University of Hawaii at Manoa who specializes in volcanoes. He said:

“When the multitude of very shallow earthquakes in Leilani Estates, and especially once the ground started to crack, it was pretty clear that magma was near the surface and passing underground there. Whether it would erupt there or continue downrift, I don’t think anyone really knew. It did seem to stall there. The earthquakes seemed to stall there, so I’m not surprised that it did erupt. I certainly couldn’t have predicted exactly where or when, and I don’t think anyone could have.

We can definitely know in general what kinds of things are going to happen. The earthquakes tell us that magma was moving underground, and when those earthquakes  localize, that gives you a sense that probably this is the most likely place, and certainly when the ground cracks occur, that means the ground’s being pushed apart for  something under there. But again, the details of exactly when or where, we don’t have the ability to do that.”

Tina Neal, Scientist-in-Charge of the USGS Hawaiian Volcano Observatory, added that they have noticed patterns when fissures occur:

I’ve never been out on the field when a fissure opened up nearby, but many of my colleagues have an combining their stories with what we’ve seen down in Leilani Estates, typically the ground starts to crack and the cracks may form days before a fissure outbreak, and the cracks may widen a little bit, and then you get some steam coming out of the crack as temperature rises as magma gets close to the surface, and then you start to also give off volcanic gas because as the magma approaches the surface the gases come out of solution. So that progression from cracking to steaming to steaming plus gas that seems to precede the outbreaks.

Our field crews are actually running around down there, noting places where we’re seeing those signs and radioing back and saying hey it looks like we might be getting ready for a new outbreak in this location.

So far, there have not been earthquakes associated with those individual events and I think that’s because the ground down there is already very broken so you could say it doesn’t take a lot of work for this magma to break the surface.

We do see increases in ground vibration, which is something we refer to often as tremor. You can see that on our seismic stations. In fact, we look back now and each fissure outbreak, we can see a nice little uptick in tremor, so hopefully we’ll get smart enough that we can see those coming or at least be able to use that as a proxy for having people on the ground watching these things.

Severe Possible Scenarios

Tina Neal, Scientist-in-Charge of the USGS Hawaiian Volcano Observatory, was asked if there was the possibility of more severe events for Leilani Estates and Hawaii Island. She said that even people outside of the rift zone should prepare with an evacuation plan as things are dynamic and unpredictable. While she said it is safe to visit the island, visitors should also be prepared and keep up to date with Civil Defense alerts.

Neil outlined three possible severe possibilities:

Well again there’s a high degree of uncertainty in my answer, but there are possible next phases that are severe and I can give you a couple of them. One is that the eruption in Leilani becomes more intense, spreads out along a larger section of the rift zone and basically threatens more homes, more people, more infrastructure.

The big earthquake yesterday, if you look at some of our maps on the website, it basically relieved stress along a certain part of Kilauea’s south flank, but there is yet another patch that did not move and so another even larger earthquake. It is possible and I have to put that out there that it is. That’s why we’re stressing that people should be prepared for earthquakes and even large aftershocks that can be damaging. 

That’s another potentially more severe outcome.

And I think probably the one that we’re just getting our heads around now is that if the lava lake drains so deeply that it gets down to the level of the water table, which is 500 to 600 meters below ground surface.

We could have a scenario as such occurred in 1924 where the lava lake drained deeply, there was a large intrusion of magma into the lower East Rift Zone. There was no eruption that we’re aware of, but we know a lot of melt went down the pipeline and so this deepening of the magna amount of the summit allowed ground water to flush into the system and when you mix water with 2,000 degree magna, you get explosions.

So in 1924 there was a period of time of explosive activity from the Halemaumau region which put out a lot of ash, a lot of big blocks. They didn’t travel outside the current closed zone, but they were certainly a more severe hazard than what we’ve seen more recently.

That kind of activity went on for many days maybe weeks, but that’s another kind of scenario that’s more severe than what’s happening now.

We’ve been talking about that and what we’re gonna be doing is we’ve got some geophysicists whose eyes are trained on the data and we’re looking for changes in the rate of the lava lake drop. We would expect to see a couple of things, more earthquakes right in the region because the system is going to start adjusting to this build up of steam explosions and we also would expect a little ash explosion start coming up from deep in the column so we think we would have some signals of warning.

Believe me, I’m very interested in this because my laboratory is mile away from there so we’ll be watching that for that outcome and at the right time, elevating awareness of that as a possibility.

But we’re not there yet and I should also point out that we would expect many days to pass even after the lava lake got to that level before activity would intensify.

That is absolutely something we’re concerned about.

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