Let’s start with a question. Which country do you think has the most frequent volcanic eruptions? Before you read on (or peek below for the answer), take a minute to think about it. You can probably guess that Australia is not a front runner. In fact, only two or three countries readily come to mind. Iceland is up there, with an eruption on average every 3 to 4 years. It is hard to beat. Indonesia is also plausible, which its plethora of active volcanoes. It is responsible for some of the worst eruption of the past millennium: Tambora and Rinjani account for two of the four largest eruptions over this period. But which country is the worst?
The previous post triggered some discussion on what next year would bring, in terms of the next VEI-4 eruption. After all, the predictions that were made for 2018 turned out to be pretty insightful. Of course, those predictions weren’t ours – these were professionals sticking out their necks. Can VC do as well?
Let’s start by looking back. What do we know about such eruptions of the recent past? Where were they? The 21st century is still young, but there have been some memorable eruptions. Wikipedia helpfully contains a list of major eruptions. The list defines ‘major’ as VEI-4 or higher; this deliberately excludes effusive eruptions. With the benefit of hindsight, this seems a missed opportunity: how can the volcanic history of the 21st century not include Holuhraun, Pu’u’O’o or Leilani? (And should Pu’u’O’o and Leilani count as one eruption? According to the standard definition, yes. Leilani was very much it own event and I would happily count it as separate, but it doesn’t qualify.)
Another point of contention is when to start. We celebrated the turn of the millennium at the start of Jan 1, 2000. But in fact, the old century didn’t end until 31 December that year. Our time keeping suffered a millennium bug: there never was a year zero, and therefore the century begins at year 1. I will therefore liberate the rebel within and discount eruptions of the year 2000 as so-last-century.
So what was this century like, so far? The first decade was decidedly busy: there were 11 VEI-4 eruptions in the period 2001-2010. The most destructive eruption was Merapi in 2010, and the most expensive Eyjafjallajökull, also 2010. (This was also the world’s first carbon-neutral eruption, as you may recall.) The decadal leader board for 2001-2010 runs 1. PNG (3 eruptions), 2. Indonesia and the USA (2 each), and several countries with 1 including Iceland. So how did you do?
The second (and current) decade still has 2 years to run (according to my time keeping). In terms of explosive eruptions, it has been quiet. There have been five VEI4+ so far, including Puyehue, which in 2011 suffered the largest explosive eruption so far this century. I’ll add Holuhraun and Kilauea (for now). Over the 21th century, this gives the following order:
- Chile (3)
- Iceland (3)
- Indonesia (3)
- USA (3)
- PNG (2)
- Russia (2)
- Ecuador (1)
- Eritrea (1)
Does the appearance of Chile surprise you? Perhaps it shouldn’t. Going back another century, there have been 31 different volcanoes erupting in Chile since 1900. It has about the same frequency of volcanic eruptions as Iceland; admittedly these eruptions come from many more sites and a 7 times larger footprint than Iceland. Cerro Hudson in 1991 reached VEI-5 and in fact was very close to VEI-6, at a DRE of 2.7 km3. And this was the second Chilean eruption of this size in the 20th century: Cerro Azul in 1932 was also a VEI-5 to 6.
But looking harder, it is surprising after all. The list of post-1900 eruptions shows that Indonesia contains more than 60 separate volcanoes that have erupted since 1900, twice as many as Chile. Indonesia has an eruption frequency that is well above Iceland and Chile. Nine or ten Indonesian eruptions reached VEI-4 since 1900, and one of these (Agung) reached VEI-5. Over the same time, Chile had five eruptions of this size. The numbers indicate that Indonesia is twice as volcanically active as Chile. That is still respectable. (One may also query whether some eruptions may have been missed in the inhospitable deserts of Northern Chile or its icy southern regions.)
So how does the 21th century compare so far? The 20th century had up to 65 VEI-4 eruptions (for a few of these it is questionable whether they reached this high). Over 18 years the 21st century has shown 16. (Now I am not counting the two effusive eruptions as the VEI scale does not really apply to them). Scaling from the 20th century, a total of 11-12 would have been expected. So this has indeed been a fairly busy period. In fact, the current decade is pretty much on schedule, whilst the period 2001-2010 was quite over-active.
Can we use this to improve our statistics of nations? To do this, I have combined the lists of the 20th and 21st century, but removed the doubtful cases and also left effusive rift eruptions out. That left me with 75 VEI-4+ eruptions since 1901. They are distributed over the decade as follows:
- 1901-1910: 5
- 1911-1920: 9
- 1921-1930: 3
- 1931-1940: 6
- 1941-1950: 4
- 1951-1960: 6
- 1961-1970: 6
- 1971-1980: 5
- 1981-1990: 9
- 1991-2000: 6
- 2001-2010: 11
- 2011-2018: 5
In this list, two decades stand out: the 1980’s and the 2000’s. In contrast, the current decade is not exceptional. (But this discounts the two effusive eruptions so it is not the full story!) Overall, we can expect a VEI-4+ eruption about once every 1.5 years, or 6 per decade. There was one exceptionally long period without such eruptions, from 1933 to 1945. This is likely a political gap: the world was too busy with nationalism to be concerned with volcanology. (There was an eruption from Rabaul within this period, but it was not documented well enough to qualify). Apart from this, the longest wait was 5 years: this occurred twice.
So going back to the original question, which countries stand out? The list below is the answer. Chile is now number 5, and Iceland number 6. Top of the list is Russia, Indonesia is second and third is the USA. Does this surprise you? I must admit that when I picked countries for the next VEI-4, I missed three of the countries in the top four. Ouch.
- Russia: 16
- Indonesia: 12
- USA: 11
- PNG: 8
- Chile: 7
- Iceland: 5
- Ecuador, Guatemala: 3
- France, Japan, Philippines, Mexico: 2
- Eritrea, Vanuatu: 1
This needs a bit of explanation. The numbers for Russia contain 6 eruptions within the chain of the Kuril islands, possible the biggest concentration of events in a small area. The ownership of these islands is disputed, as they are also claimed by Japan. The US numbers are boosted by eruptions in the Northern Mariana islands. Ecuador includes the Galapagos, and France is responsible for all VEI-4 eruptions in the Caribbean.
In the comments on the previous post, a number of ideas were floated for which volcanoes could cause a VEI-4+ eruption within the next year (or two). The following volcanoes were mentioned:
Iceland: Grimsvotn, Thordarhyna, Oraefajokull, Katla, Askja
PNG: Manam, Rabaul
USA: Kilauea, Augustine
Indonesia: Merapi, Sinabung
Chile: Nevados de Chillan, Puyehuhe-Cordon Caulle
Mexico: Colima, Popocatepetl
Russia: Shiveluch, Avachinsky, Kliuchevskoi
The top-8 of the country list are all represented. On the other hand, France, Vanuatu and Eritrea are not. The most notable absence is perhaps the Philippines, home of the largest eruption of the past 130 years but not seen as a likely contributor over the next two years.
So after this, what do I think myself? My opinions have changed. Based on the numbers, Russia is the top candidate, and especially the region of the Kuril islands. But Iceland should not be ignored, especially since Oraefajokull is building up to activity and it has a VEI-4 history.
And which particular volcano? That is a very long shot. But it is worth noting that VEI-4 eruptions can be a repeat offence: such an explosion is not strong enough to fully disarm a volcano, and a repeat occurrence is possible. In the list of eruptions several volcanoes indeed appear more than once: Avachinsky, Mount Lolobau, Kelud, Augustine, Rabaul. Therefore, It is worth keeping an eye on those volcanoes who have done this before.
And here I’ll end and leave the conclusion to the commenters. Did you change your mind? Where do you think the next event will be? Or do you think that the 50% chance of no VEI-4 eruption in the next 1.5 years will come up trumps, and we will have two years of volcanic solitude? Or do you think this is meaningless if the large rift eruptions are not included? DO you think the wikipedia lists are wrong or incomplete? (And yes, I am aware that the VEI’s listed in the wikipedia list for the 20th century are on the high side.) We are looking forward to your thoughts!
Albert, December 2018