This is the time of the year when people like to look back. What was the year like? Good or bad – or, as is almost always the case, a bit of a mix? And if looking back is not your thing, newspapers run columns where specialists (of varying level of expertise) are given a go at predicting the year ahead, in the safe knowledge that no one will ever check up on their predictions. After all, which newspaper would like to admit that they were wrong? Some predictions were rather easy though. That the UK would end the year in turmoil was always a safe bet. Wars and rumours of wars are also annually guaranteed, although perhaps few saw one coming between the US and Canada. Similarly, that there would be fire in the Ring of Fire was certain. That the main fire would be right in the middle of it was harder to see coming.
Twelve months ago, three volcanologists (Sylvain Charbonnier (South Florida), Katie Preece (Glasgow) & Ralf Gertisser (Keele)) took the plunge and pointed at the volcanoes most likely to erupt in 2018. (To be a bit more precise, they said that these volcanoes were worth keeping an eye on.) It is interesting to see how well they did, knowing that volcanoes act on time scales of a decade, not a year, and if one of their candidates did not erupt, it does not mean that they were wrong -just a bit early. Which ones did they pick?
1. Kirishima, Japan. This volcano was at a state of alert a year ago, so perhaps this was an easy prediction. And indeed, it suffered a series of explosions in the first half of 2018. The events were not severe, which was a good thing.
2. Merapi, Indonesia. They wrote: With a death toll of nearly 400 people, its 2010 eruption is so far the deadliest of the 21st century. One may argue that another eruption of Merapi is overdue, although there are no immediate signs of increased volcanic activity or unrest. They were spot on: on May 11, Merapi erupted and an area up to 5 km from the summit had to be evacuated. The slopes of Merapi are both steep and densely populated: this is one of the most dangerous volcanoes on the planet.
3. Öræfajökull, Iceland. as the volcanologists wrote: Öræfajökull appears to be waking up. We have all seen this and the awakenings are continuing. But as usual when long-dormant volcanoes come back to live, the process can take years. There are teenagers who wake up faster. The re-activation has continued and 2018 far exceeded 2017. But no eruption has happened: it could be years away, or it could be in a month. With volcanoes, it is hard to tell.
4. Popocatépetl, Mexico. This volcano is the most active in Mexico. Since the early 1990’s, activity has been increasing and a warning for 2018 was entirely appropriate. And indeed, explosions happened, and minor activity was almost continuous. There was a large explosion this weekend. Popocatépetl has only seen minor events in historical times, but also has a history of major events, including a VEI6 around AD 800. There is danger here.
5. Villarrica, Chile. Not many volcanoes in the world have a lava lake. This one does, albeit a small one. The summit is easily recognizable by its shape. There was a significant explosion in 2015, and late 2017 there was an increase in activity. However, it came to nothing. This one did not perform according to expectations.
6. Kilauea, US. What can I say? The team came up trumps on this one, although it did not do what they expected. It is hard to believe now that one year ago, this was the most predictable volcano in the world. It was erupting from Pu’u’O’o, had been for over 30 years, and apart from brief interruptions and rift events, was not going to change. The team wrote ‘There is no reason to expect this eruption will end any time soon.‘ The Kilauea lava lake had been growing but was not dangerous apart from its sulfur emissions. The danger was at Pu’u’O’o, which was beginning to feed lava north, towards inhabited areas. Look at it now. Leilani devastated, Kapoho destroyed, Pu’u’O’o dead (presumably for good), and Kilauea collapsed. Who saw that one coming! The positives are that no one was killed, and the gas eruptions have ended making the Big Island a far healthier place to live. Hawai’i may even look forward to a decade without lava. But I would keep an eye on Mauna Loa. So how did the team fare on this one? The picked out the right volcano – but nothing they expected was correct. That is the way of volcanoes. Full marks.
7. Hekla, Iceland. To be fair, they did not predict activity here. Instead they wrote: Volcanic unrest can also start suddenly at dormant volcanoes such as Hekla in Iceland which, based on its past record of decades of quiescence followed by sudden huge eruptions, may awake with little warning. And that remains true.
So how did they do? Very well, actually, although in the case of Kilauea some luck was involved. Villarrica was the only misfire, whilst Öræfajökull decided to wait. I would grade the result first class.
One can also look for the ones they missed. For there were more eruptions in 2018, and perhaps more dangerous than the events in Hawai’i. Kadovar erupted in early January, and the island had to be abandoned by its inhabitants. And do you remember Mayon? It was active from January until late March. In the end the eruption remained minor, but for a while things looked dangerous for Legazpi, the major city build in the firing line. Sinabung had significant blasts in February and April, with pyroclastic flows around the summit. It has grown steadily more active since it woke up in 2010.
Fuego was the worst volcanic event of the year. An eruption on June 3 led to pyroclastic flows or lahars. 109 people are confirmed dead and 200 are missing.
The prize for the most photogenic volcano of 2018 goes to Anak Krakatau. It is the most rapidly growing volcano in the world and has been active for much of the year. Being an island to itself, with no one living here (not since the disaster of its famous parent), this is also a relatively safe volcano – as long as you keep your distance.
Overall, this was probably the most interesting volcano year since Krakatoa!
We should not forget the two big earthquakes this year, Sulawesi (where Soputan erupted today) and Anchorage. We are interested in the earth under our feet, and that includes earthquakes. Liquefaction was a major factor in the damage done by both events.
My personal recollections of our volcanic year are dominated by Kilauea. This was an amazing eruption. Rift eruptions are of course not uncommon. Most lava perhaps comes from rifts rather than summits – in contrast, explosive eruptions come mainly (but not exclusively) from the summit. But we have learned a lot about how rift eruptions actually happen, having had two major and well observed events in the past 5 years. They had much in common: the earthquake sequence down the rift, the multiple potential eruption sites until it focusses on one place, the sudden end. Both events combined the rift eruption with a caldera collapse, and in both cases the volume of the collapse and the volume of the eruption agreed well – in the case of Kilauea, very well. Two is too few cases to generalize but let’s anyway. The equivalence between ejecta and collapse shows that the rift eruption is fed by magma stored below the summit:the magma does not come directly from the mantle below. Kilauea first erupted old magma, showing that there is magma stored in the rift, left over from previous intrusions which is pushed out. It is not clear that that happened in Holuhraun as well. As the magma came from the summit store, the gravity model where the weight of the summit pushes it out into the rift works well. HVO has now introduced the concept of ‘magma head’ where the stress in the rift and the magma head counteract each other. A sudden breakthrough in the rift reduces the stress and the magma begins to flow. In Kilauea, the major earthquake reduced the stress further. The sudden end occurs when the summit pressure becomes insufficient to overcome the stress. In Kilauea, there was a phase towards the end where the eruption became intermittent, and restarted after each summit earthquake. This shows the importance of the summit. Finally, both eruptions has a large series of these summit earthquakes, in which the caldera dropped step by step. Calderas are made of layers of solidified lava – tough enough to keep the magma down. As the magma drains out, the layers drop down as solid blocks. Both eruptions caused earthquakes of magnitude around M5.3. The fact that they were so similar suggests that the strength of the rock (solid lava) was very similar in both calderas.
Now that we have a model, we can make predictions for what will happen in the next rift eruption. The only questions that remain are when and where that will be!
The disappearance of the lava lake at Kilauea is regrettable. It provided great, and safe, viewing. One of the endearing images is that of the smile in the lake. As the lava withdrew, the smile too went. This was the Kilauea cat, like the Cheshire cat in Alice in Wonderland, disappearing while leaving its smile behind. In the case of the Kilauea cat, the image of its smile.
Alice in HVO land
‘Please would you tell me,’ said Alice, a little timidly, for she was not quite sure whether it was good manners for her to speak first, ‘why your cat grins like that?’
‘It’s a Kilauea cat,’ said the HVO, ‘and that’s why.
‘I didn’t know that volcano cats always grinned; in fact, I didn’t know that cats could grin.’
‘They all can,’ said HVO; ‘and most of ‘em do.’
‘I don’t know of any that do,’ Alice said very politely, feeling quite pleased to have got into a conversation.
‘You don’t know much,’ said HVO ; ‘and that’s a fact.’
And that is indeed how we felt during the eruption – so much to learn!
The remaining conversation of Alice in Wonderland explains why the Kilauea magma came out in such an unexpected location, downtown Puna.
Alice was a little startled by seeing the Kilauea Cat sitting on a bough of a tree a few yards off.
The Cat only grinned when it saw Alice. It looked good-natured, she thought: still it had very long claws and a great many teeth, so she felt that it ought to be treated with respect.
‘Kilau Puss,’ she began, rather timidly, as she did not at all know whether it would like the name: however, it only grinned a little wider. ‘Come, it’s pleased so far,’ thought Alice, and she went on. ‘Would you tell me, please, which way magma ought to go from here?’
‘That depends a good deal on where you want it to get to,’ said the Cat.
‘I don’t much care where—’ said Alice.
‘Then it doesn’t matter which way it goes,’ said the Cat.
‘—so long as it erupts somewhere,’ Alice added as an explanation.
‘Oh, it’s sure to do that,’ said the Cat, and vanished.
Alice was not much surprised at this, she was getting so used to queer things happening. While she was looking at the place where it had been, it suddenly appeared again.
‘By-the-bye, what became of the lava?’ said the Cat. ‘I’d nearly forgotten to ask.’
‘It turned into a hole,’ Alice quietly said, just as if it had come back in a natural way.
‘I thought it would,’ said the Cat, and vanished again.
Alice looked up, and there was the Cat again, sitting on a branch of a tree.
‘Did you say hole, or pole?’ said the Cat.
‘I said hole,’ replied Alice; ‘and I wish you wouldn’t keep appearing and vanishing so suddenly: you make one quite giddy.’
‘All right,’ said the Cat; and this time it vanished quite slowly, beginning with the end of the tail, and ending with the grin, which remained some time after the rest of it had gone caldera.
What will next year bring? Perhaps we should leave the predictions to the experts. There is however a fair chance of an eruption in Indonesia, a low chance of one in Hawai’i, and a 30% chance of one in Iceland. And 100% chance of an event in Westminster.
Finally, there has been the usual variety of posts this year. I like writing background stories, about space, history, or geophysics. But there have been a fair number of stories about volcanoes as well, by the other VC writers. We welcome your submissions!
Here is an overview of the posts published at VC over the past 12 months.