Taupo is one of those volcanoes I do not like to write about in Volcanocafé. It is one thing to write a historical retrospect of what it has done in yon olden days, and something completely different when it is doing something interesting.
The reason is simple, Taupo is one of those volcanoes that have the word “super” attached to it. It is both a super-erupting volcano and a super-volcano. Most volcanologists do not like the phrase super-volcano, but I do not have any qualms using it. It has a certain descriptive panache to it.
After all, that super-suffix says it all, these are not the volcanoes you want to be around when they go off with gusto. That being said, far from all eruptions from a super-volcano are big, far from it.
I should also here probably state that the Taupo Volcanic Zone is one of the volcanoes I work with professionally, obviously I do not work for the GNS (Geological Survey of New Zealand). I work for a private company that has other volcanic interests there. So, by necessity I have to know a lot about the volcanoes on the Taupo Volcanic Zone.
During the last couple of years Taupo Caldera has been inflating, mainly at the Horomatangi Reef at the Western side of Lake Taupo.
This is a resurging dome on top of the main magma reservoir. I have interpreted this as influx of fresh magma from depth into the reservoir in combination with heating of water-carrying layers under Horomatangi Reef.
This increase in pressure has caused smaller swarms, but not enough to write about really. But it merited lifting the volcanic alert level from 0 to 1.
This is when volcanologists decide to look at things with a bit more interest since the volcano is doing something unusual that may, or may not, lead to something in the future.
At 23.37 local time on the 30th of November an M5.6 earthquake occurred at 9km depth under the southern part of the Horomatangi Reef.
This has been followed by 200 aftershocks, with a M4.5 being the largest. There has been a general increase in seismic activity at the volcano since May 2022.
The M5.6 caused a minor tsunami in the lake that killed two slightly innocent pedalboats, no pedalboat is ever completely innocent.
Inflation due to magma, increased earthquake activity, and a larger earthquake is definitely enough for me to find it worthwhile to write an article.
We have previously covered the region more in depth, so this will be a short recap of the geologic setting.
Taupo Volcano is technically a resurging large caldera volcano situated inside a larger volcanic field called the Taupo Volcanic Zone, which spans from Whakaari (White Island) all the way to south of Taupo itself.
It contains famous volcanoes like Okataina, Rotorua, Ruapehu and Tarawera, just to name a few. TVZ is an intra-arc volcanic rift producing basalts as base magma and it is historically among the most prolific large eruption centres.
The rifting is at it’s largest at Taupo (around 8mm per year) and diminishes towards the north. Previously the spread rate was higher to the north, and several large calderas formed there during VEI-7 and VEI-8 eruptions.
But as the spreading increased to the south and to Taupo it gradually became more explosive, and it started to erupt rhyolite in ignimbrite eruptions around 100 000 years ago. For the first 200 000 years the volcano was more benign, but benign should probably be taken with a pinch of salt. Everything is relative after all.
26 500 years ago, Taupo entered the big league with the VEI-8 Oruanui Caldera Collapse. It caused 430 cubic kilometres of pyroclastic fall deposits, 320 cubic kilometres of pyroclastic density current flows (ignimbrite base surge), and a further 420 cubic kilometres of intra-caldera material. All of that is equivalent to 530 cubic kilometres of rhyolite magma.
In the year 232 came the very violent Hatepe eruption. At 120 cubic kilometres of material, it is the second largest eruption in the last 5 000 years after the 1628BC destruction of Mount Aniakchak that came in at 150 cubic kilometres.
Hatepe was unusually explosive with 25 percent ejected in mere minutes, another trait it shares with Aniakchak.
Thankfully it takes quite a bit to get volcanoes of this size going, especially after a prolonged nap of 1 800 years. This means that it will take a bit more for an eruption to occur.
Here it is good to remember one thing, it is in the job description of large volcanoes to erupt now and then. It is up to us mere mortals to figure out when it is time to be somewhere else. It is therefore important to follow any advice or evacuation order from the competent authorities. In this case that is GNS.
If they say it is time to head out, you do not ask yourself if you should bring old Aunt Agatha’s Saxophone collection. No, instead you open the door and start to galumph as hard and fast you can in the recommended direction.
Anyway, we are not at the galumphing stage yet. All we know is that the volcano has indigestion and is moving towards an eruption that can come in a few weeks, or in a few years. It may though be a good idea to have your essential papers, medications, and some empty water bottles handy near your door for the next couple of decades.
After all, better to be prepared and nothing happens, compared to wonder where your heart medication is when you need to run like Usain Bolt…
What I am trying to say is that sooner or later Taupo will erupt, but right now it is up to volcanologists to watch it, and for you to go about your day as per usual. After all, Taupo could go back to sleep for a few hundred years. We are not beyond the point of no return.
So, you are curious about what an eruption would look like? We need some figures for that.
Thankfully we have a pretty good record of all the eruptions in the last 10 000 years at Taupo, and since all eruptions are not equal it is good to look at the sizes, and how many they have been in each size-bin.
The smallest one in the record is a minor VEI-3 at 0.01 cubic kilometre. I will add a reference eruption for each size. And even though it was 26 500 years ago I will chuck in Oruanui for good measure in the statistics.
VEI-3 8 0.01 – 0.09km3 Hekla 2000
VEI-4 10 0.1 – 0.9km3 Eyjafjallajökull 2010 & Grimsvötn 2011
VEI-5 2 1 – 9.9km3 Cerro Hudson
VEI-6 0 10 – 99km3 Pinatubo, Hunga Tonga
VEI-7 1 100 – 999km3 Thera, Tambora, Aniakchak
VEI-8 1 1000km3+ Toba
It is here good to remember that out of 22 eruptions 20 was of manageable size with 18 being more of a nuisance that you just do not want to be around. A VEI-5 is something that you definitely do not want to be around since it can produce pyroclastic base surges that travel up to 50km.
That there is no VEI-6 is debatable, one of the VEI-5s was so large that it is likely to have been a small VEI-6, it is not easy to get the figures exactly correct after thousands of years of washing away of the evidence. But I will leave it as is.
For a VEI-6 it is a very good idea to be further away, not all of them are as nice as Pinatubo, Hunga Tonga packed a far larger punch since the eruption was short in its penultimate explosive phase.
Even though volcanologists are getting better and better at forecasting when an eruption will occur, we are not good at knowing the size of an eruption in advance.
Now we come to repose time. Many volcanoes tend to have a larger eruption after a long nap. And we know that Taupo tends to be cyclical with periods of dormancy and periods of heightened volcanic unrest.
Are there any patterns there?
3 eruptive periods started with VEI-3 eruptions, we have 3 VEI-4 starters, 2 VEI-5 starters, and no known larger first eruption in the period.
I would though not really trust this with my life, there seems to be a trend towards it being able to start with any size, and the statistic material for the big ones is to small to say anything at all. In other words, it could be any size.
Would I go to Taupo?
I think the best question to ask is if I would go there right now? Yes, I definitely would, and in fact I am going there come spring. Well, down under it will be fall, but you catch my drift.
After all, dealing with huge honking volcanoes is my line of work, and it is an awesomely beautiful place.
But, if I see anything I do not like, or if GNS tells me to go, I will be the one galumphing first in the heard towards anywhere else far away.
Trust me, when an eruption will be around the corner it is not one of those nice Icelandic tourist eruptions that you travel to.
A sizeable VEI-5 can kill you up towards 50km, and a VEI-6 with a pyroclastic base surge will kill everyone within 50km and may kill you at 100km. You do the math for anything bigger yourself, it ain’t gonna be pretty up and close.