As I have perused the internet in the last few days I have noticed that the “gargantuan landslide causing a mega-tsunami” meme is in full swing again, now in relation to Kilauea. Therefore, I think it is time to write a more laidback article about what is happening in that regard with Kilauea.
But before that I think we could do with a brief update on what is happening at Kilauea.
As some might remember I jokingly said that the most likely time for the sinking lava in the caldera to hit the watertable was at 10.14 CET today Sunday. It was based on the known rate of ascension and the depth estimated by the USGS of the watertable.
So far, the amount of visible steam has increased, but not enough for it to be a done thing. It is though in the making. After that it is just a waiting game for rockslides to cause ash explosions.
As long as you are not around you are not in any grave danger. But, if you are down wind and there is ash in the air you can if you wish wear a particle filter to avoid getting ash into your lungs. Do note, if you are planning to be in an area with a lot of gas, go for an acid gas classed filter.
Or, if you can’t get hold of that, make a simple mask of five layers of gauze that you keep damp. The moisture will catch the sulphuric gases turning them into sulphuric acid. Best is though always to be upwind of both ash and gas (if possible). It is a neat and cheap trick that I learned about in Indonesia.
To reiterate, ashy detonations in the caldera will not be a danger to life and limb, and there will not be a pyroclastic flow. This is not that type of volcano.
The tiltmeters have started to flatline. This is a sign that the temporarily low pressure in the dyke has started to go up. This was bound to happen from the inflowing magma. This may mean that the vents around Leilani Estates could have a longer duration and erupt more lava.
The vents at Leilani seems to have started to migrate further east sparing houses and homes of the locals. As I am writing this we have come up to 17 confirmed vents. I do suspect that there will be more vents opening up in the next few days. Or, one will open up and stabilize as a more permanent fixture. With a bit of luck such a vent will be away from the houses.
And just to clarify things, this is a very small eruptive phase in relation to what Kilauea can sometimes do, and at this point there are no signs that this will turn into a major eruptive phase.
Slump or slide?
In my latest article I wrote about gravity and it’s affect on volcanoes. Because, the simple truth is that what comes up, must always come down. The question is more about when, and in what manner, it will come down.
There are a lot of factors that will decide when, at what speed, and in what manner. I will try to go through at least the most important of those factors below, but first we have to go through the 3 most common types of mountain movement that affects volcanoes.
This was not widely discussed before around the year 2005. Then slides around volcanoes became sort of a fashion thing with geologists. As usual the hysterical English tabloid press got hold of it, and we became inundated by magnitude 69 earthquakes causing 1000 meter high tsunamis of doom as entire continents fall out into the ocean. We are still mopping up things after this PR-slidemageddon.
So, let us instead look at things calmly. What is what, and specifically, what is Kilauea doing? Before that I will though go public with the following public service announcement: If your greatest wish in life is to stand on a surf-board and do the largest possible rock-slide surf, Kilauea is not your best bet.
The slide – This is when a volcano (or mountain), due to the effects of gravity (or magmatic intrusions), develops faultlines and a portion of the mountain rapidly slides down and outwards.
The slump – This is when instead of rapidly sliding downwards, a portion is slowly gliding down and outwards. This gentle meandering of a mountainside happens at speeds measured in centimetres to metres per year.
The hybrid – This is when smaller portions rapidly slide off as a large portion of a mountain is gently slumping downwards.
I will now go through 4 factors that apply to how a mountain will behave as it is galumphing downwards. These are gradient, rock-or-rubble, fault-layout and buttressing.
Gradient – or in other words, how steep the edifice of the volcano is. The general rule here is that the steeper the edifice is, the more likely it is to catastrophically fail. A tall and steep strato-volcano is far more likely to slide than a gently sloping shield-volcano like Kilauea.
The grade needed for a mountain to start sliding depends on a lot of factors and is hard to calculate. And sometimes a volcano can happily be stable at let us say a 45-degree angle but will become extremely unstable at say 48 degrees. If such a volcano inflates rapidly from intruding magma it can fail, say hello to Mount Saint Helens.
Kilauea is a gently sloping shield volcano above the surface. It is steeper below sea level, but not so much so that it is prone at this geologic point in time to fail rapidly.
Rock-or-rubble – the type and constituency of the rock in the volcano also plays a significant role in how it will be moving about. These lava layers are far more stable than ash, lapilli and pumice. Kilauea is predominantly erupting lava in thick stable flows.
Below the ocean level it tends to produce pillow-lavas in the shape of big round balls. These are not as stable as lava layers, but deeper into the mountain these balls are welded together by lava, and then pillow lava turns stable.
Strato-volcanoes like for instance Fuego in Guatemala, or Hekla in Iceland, produce far more ash, pumice, lapilli and lava-bombs than Kilauea ever will. In these cases, you end up with volcanoes that are loose rubble piles made up of what feels like ball-bearings (at least if you try to walk up them). To compound things, this ball-bearings are produced by strato-volcanoes and not shield-volcanoes, and as you now know, strato-volcanoes are also far steeper.
To sum it up, Kilauea is a gently sloping thick-lava-layered volcano. Not many points on the slideometer so far.
Fault-layout – This is where Kilauea actually get a few points. It does have a fault system of a type associated with movement in volcanoes and mountains. But, here it grows boring once again. The angles of the faults are not in angles conducive to rapid large movements.
Instead they are of a type associated with slow down and outwards movement. At strato-volcanoes like Fuego you get steep faults forming prior to flank-failure. And there is nothing like that here.
I should also here point out that there is no risk that Kilauea will go and do something as boisterous as the Mount Saint Helens flank-collapse. Kilauea is just to gently angled and too big for that to be possible. It would require hundreds of cubic kilometres of rapidly intruding magma for it to happen, and that will never happen since Kilauea is leaking lava like a sieve all over the place.
So, that leaves us with Kilauea having gotten a few points on the slow slumpometer.
Buttressing – this is any force or matter that will hold back, or slow down, a slide or a slump. In Kilauea’s case there are at least 3 things buttressing the volcano.
First, we have Mauna Loa, it is holding the north flank of Kilauea in check. So much so that the slumping of Mauna Loa’s 75 000 cubic kilometres of rock is slowly pushing the entire Kilauea towards the ocean. So, the north side will not go anywhere.
On the other side we have a rather big seamount called Loihi. It is the next volcano growing in the chain, and even if it is not of Kilauea’s size, it is big enough to create a resisting force for the bottom of the south flank. In other words, it slows things down.
The third thing has a smaller, but in many ways more profound effect, and that is water. The Pacific Ocean packs a lot of mass. And that mass equals a rather sturdy brake on things trying to move fast.
Now many people will shake their heads and say that water is flexible. Yes, it is, but it will still work as a brake. We know this very well from historical data. 20 000 years ago, the ocean level was far lower due to the water being pent up in the continental glaciers of the ice age. It is around this time we have most of the large slides at volcanic islands around the world.
So, Kilauea is quite high on the buttressometer.
By now our aspiring slide-surfer is crying into his can of board-wax as he realises that he will have to go and find a better volcano to surf down.
Parts of Kilauea is slowly slumping down into the ocean, but at such a sedate and majestic pace that even houses close to the ocean will remain above water for quite some time.
Small parts will now and then break off at a more rapid pace, but this is mostly lava edges that grow steep cliff faces as lava pours down into the ocean. Last time this happened was during the ocean-entry phase of the 61g lava-flow.
Now and then there will be earthquakes, but that is the nature of things. Those earthquakes will not be so bad that they will kill a lot of people, if the houses are built to cope. And now and then lava will come up out of the ground along the rift zones of Kilauea.
But what will not happen is that there will be a large slide and a big tsunami, regardless of what the English tabloids write.