Eruptions


The Atherton Tablelands in Far North Queensland, Australia.

Nothing makes me shudder like any article titled “Blankety-blank volcano is overdue”. Typically the article that follows is full of nothing but vapid speculation and media fear-mongering. So, it wasn’t too surprising that an article titled “Volcano eruption ‘overdue’” in the Brisbane Times (amongst many other sites) didn’t disappoint (or, in particular, it did). Dr. Bernie Joyce is quoted as saying “It is much more likely to be a matter of when, rather than if…” in regards to potential future volcanism on the Australian continent. Well, OK, yes, there will, again, someday be volcanism again on Australia … and I am all for preparedness, which I think is the point that Dr. Joyce is trying to make. However, by saying any volcanism system is “overdue” based solely on the fact that there hasn’t been an eruption for a long period is foolish at best.

The “data” pointed out is that in Far North Queensland, there are eruptions every ~2,000 years over the last 40,000 years, yet now it has been 5,000 years since the last eruption. That is the sort of silly “predictive” science that gives volcanology a bad name. Sure, it there is a statistical chance, but to say that it is “overdue” because it hasn’t eruptive in the known repose interval, is tenuous at best. Sure, there is likely a close to 100% chance that a volcano will erupt in the region again, but that is the same as saying that if you sit at an intersection long enough, you’ll see an accident. It will happen, but it is definitely not “overdue”.

Australia is not typically considered a very volcanically active area, mostly because it is about as stable a continental craton as you can get, with no active subduction near the continental part of the plate. This means that most, if not all, of the volcanism on the Australian continent is related to a “hot spot”, similar to Hawai’i or Yellowstone (just with a lot less energy to create volcanism). There are a number of volcanic fields, including the Newer Volcanic Province field in South Australia. It is a small scoria cone and shield volcano field that last erupted in ~2,900-3,000 BC (based on 14C dating) from Mt. Gambier and Mt. Schank. The volcanoes produce basaltic lava flows and phreatic eruptions, which is fairly typical for this type of field. You can see that there is an awful lot of volcanism in the region over the recent (geologic) past. The volcanic field mentioned by Dr. Joyce in Far North Queensland is likely the Atherton Volcanic field (which, incidentally, doesn’t make it into the GVP). Similar to the Newer Volcanic Province, the Atherton field is a scoria/shield volcanic field that stretch back at least 3 million years.

Comments

  1. #1 Michael Simpson
    September 22, 2009

    In Jared Diamond’s book, Collapse: How Societies Choose to Fail or Succeed, he mentioned that the reasons that Australia was so infertile was a lack of volcanism, no glaciation and little uplift for mountain building. Reading this article, it appears that these volcanoes aren’t exactly at Mt. Ranier level, so I’m going to guess with or without increased volcanism from these sites, Australia is not going to get fertile all of a sudden.

  2. #2 Fitz
    September 22, 2009

    I love vapid speculation. Its better than no speculation at all, and if it gets a few folks to go off to sites like this and actually verify some facts, then its made a few people smarter.

    Besides, overdue is overdue. It is a poor use of statistics to say something that happens every 200 years will continue to happen every 200 years. But volcanoes arent exactly like intersections either. If you sit at an intersection where there is a wreck every day on average, and you watch 3 days without a wreck, it doesnt mean there will be 4 wrecks or a wreck 4 times as big.
    Its more of an engineering problem. If you put heat on a boiler and every 200 hours it pops the saftey valve, you can be fairly certain that if it goes 400 hours without popping, you might have a problem.

  3. #3 Erik Klemetti
    September 22, 2009

    Interesting analogy, Fitz, using the boiler. However, the key problem there is you don’t know if the “heat” coming to the boiler is constant over long periods. Sure, if you know the input isn’t changing and there hasn’t been a pop in 400 hours, that is cause for some concern. However, with volcanoes, it can never be assumed that the system will stay exactly the same over long periods, so even if you’re 200 hours “overdue”, you are likely well within the margin for geologic “error”, as it were.

  4. #4 Gijs
    September 22, 2009

    Pretty much the same thing is going on in the Eifel region in Germany. There hasn’t been an eruption in the area for 9.500 years, where quaternary volcanism started to occur around 970.000 ± 100.000 years BP.

    The Eifel can be divided into three volcanic areas. The West Eifel (240 monogenetic volcanoes since ± 970.000 years ago), the Hocheifel (± 300 volcanoes mostly from between 46 million and 6 million years ago), and the East Eifel (± 100 mostly monogenetic volcanoes that formed between ± 500.000 and 11.000 years ago, including the famous Laacher See volcano). To the East and Northeast are other volcanic areas close to the Eifel, all of tertiary age.

    – Map of the Eifel region: http://img508.imageshack.us/img508/7049/overzichtskaarteifelsie.png

    Currently the Eifel region is relatively quiet. CO2 emissions are low, but in some places visible, like at the ‘cold water geysers’ of Wallenborn and Andernach, and the ‘mofetten’ at the eastern shore of the Laacher See. The uplift of the Rhenish Massif (on which the Eifel is located) is about 1 mm a year, and the area with the most significant seismic activity is located between 50 and 80 kilometres from the Eifel volcanoes, in a graben system that lies to the North (the Aachen and Düren region). Micro earthquakes occur a lot just Southeast of Laacher See, but they’re probably caused by ground water that’s being heated over an area where there is a higher degree of partial melting. No signs of rising magma have ever been recorded, nor anything else happened that indicated impending volcanism or related threats.

    – ‘Cold water geyser’ in Wallenborn: http://www.geographie.ruhr-uni-bochum.de/ag/landscha/Wallende_Born.JPG
    – ‘Mofetten’ at the Eastern shore of Laacher See: http://static.panoramio.com/photos/original/17279049.jpg
    – Micro earthquakes Southeast of Laacher See: http://www.spiegel.de/img/0,1020,800872,00.jpg

    The cause of all this is probably an anomaly, of which some think that it is a mantle plume. That it probably isn’t, doesn’t change the fact that the anomaly is still present underneath the Eifel, like it has been for hundreds of thousands of years, if not millions of years. This is one of the main arguments for geologists to think that the area is probably only dormant, and not extinct. That, and ofcourse the fact that volcanism took place there only 9.500 years ago. What’s also interesting to look at, is that there have been some ‘breaks’ in volcanic activity in the past, which lasted between 10.000 and 20.000 years on average.

    To make the subject somewhat more popular, geologist Ulrich C. Schreiber wrote a book, called ‘Die Flucht der Ameisen’ (Escape of the Ants), discribing the events leading up to a fictive future eruption in the Eifel, the eruption itself, and the aftermath. Although it didn’t make the headlines everywhere in Europe, it did in Germany, and more people are now aware of what threats volcanism in the Eifel might pose in the future.

    Sources:
    – ‘Geologie der Eifel’, Wilhelm Meyer
    – ‘Volcanism’, Hans-Ulrich Schmincke
    http://www.mantleplumes.org/WebpagePDFs/Europe.pdf
    http://www.geokalypse.shayol.de/

  5. #5 MadScientist
    September 22, 2009

    I guess some people are getting volcano envy. Years ago some people were saying some mountain in Victoria (SE Australia) was likely to erupt. I said that would be fantastic except that I don’t see any truth at all to the claim. Earlier in the year (or was it late last year) Victoria did experience a few shocks that rattled houses enough for people to notice, but those were tectonic. I’m amazed by the cinder cones in northern Australia; as ancient as they are, they’re still instantly recognizable as cinder cones.

  6. #6 Rebecca
    September 22, 2009

    My geologist sister said that the hot spot that produced most of Australia’s volcanoes and the Great Dividing Range was now sitting out in the Southern Ocean and we were unlikely to experience volcanic activity in Australia. We had this conversation years ago.

    There is a lot of basalt and old volcanic activity in Australia and the soil is QUITE fertile as a result. I don’t think, personally, that Australia will see any further volcanic activity for a while.

  7. #7 Katherine
    September 22, 2009

    Oh, so I don’t need to fear obliteration every time someone tells me Taupo is overdue then? Phew.

  8. #8 Fitz
    September 22, 2009

    I’m from Kansas, I have MAJOR volcano envy. Earthquake envy. Hurricane envy. Exciting weekend envy, all of those.
    If you have tornado envy, we can trade.
    I would NEVER assume a system has constant heat, even if I was regulating the heat myself.
    Trouble is, the heat could be going up and Im sure that has about the same chance of making a long period happen as less heat would, theres just so many variables.
    Does Australia have a Failed Rift? I have Failed Rift Envy too.

  9. #9 MadScientist
    September 23, 2009

    Speaking of not assuming that volcanic systems remain the same over long periods of time, I find Stromboli to be amazing because it’s pretty much been doing the same thing for over 2000 years (probably longer, but I’m not aware of historical records giving a better fix on how long the activity has been going on). Tavurvur was another surprize; it was in continuous eruption from 1996 to late 2003 (I have no idea of its activity after 2003).

    One thing that bemuses me is that people have an absolutely ridiculous notion that these events must somehow be periodic, and yet a look at just about any volcano for which we have a few recorded historical eruptions (or eruption data deduced from digging trenches) shows no obvious pattern.

  10. #10 Michael Simpson
    September 23, 2009

    Fitz, through I live on a fault and not too far from THE San Andreas fault, I wouldn’t trade you my earthquakes for tornadoes! I would trade for some rain however. Lots of rain.

  11. #11 Bruce S.
    September 23, 2009

    well, the Aussies did just lose the Ashes. That’s probably enough excitement for them for a while.

    As for periodicity and prediction and all the rest of it… a lot of it has to do with the fact that we have about the same historical timespan as that of a gnat and are not that much better at coming to terms with it.

  12. #12 Mikhel
    September 23, 2009

    I’ve heard informed people talking of Vesuvius as ‘overdue’ – is that more soundly-based? I guess it depends on the volcano, but for sure is that ‘eruption overdue’ makes for a great headline.

    By the way, that Brisbane Times article is the most illiterate I think I’ve ever seen in a mainstream paper.

  13. #13 Adam
    September 23, 2009

    In my experience as an expat Australian I would have to say that there might be more pressing problems than the threat of volcanism in the somewhat near future. The fact that Sydney and much of the rest of the state in which it resides was nailed by a huge and very uncharacteristic dust storm (http://www.smh.com.au/multimedia/national/dust-storm-swallows-sydney/20090923-g19h.html) yesterday might be a heads up that global warming may not be all good.

    Having said that Eastern Australia preserves a pretty good record of basaltic (s.l.) volcanism since the Tertiary (http://volcano.oregonstate.edu/volcanoes/volc_images/australia/volc_australia.html). Dissected shields at Ebor, the Warrambungles, the Tweed region and many other places, as well as the Newer and North Queensland fields, show that the craton is not completely stable. These regions are almost among the most fertile in the country too, but the lack of recent glaciation is also probably more of a factor with regards to the lack of soil fertility.

  14. #14 Fitz
    September 23, 2009

    Tornadoes are a lot like earthquakes and volcanoes in one respect, you can run away from the little ones.
    I think fertility is more a function of rainfall amount than recent glaciation. They say the Sahara used to be a forest.
    They also say that there are lies, damned lies, and statistics.
    I would worry a lot more about a volcano like Vesuvius, that is well documented historically and has a period of eruption that can be verified pre-historically. The shorter the period, the more likely it will repeat in a meaningful timeframe. I bet theres a Statistical Term for that.
    Trouble with volcanoes is they make such lousy analogies.
    Tornadoes are about as good as any I suppose. You’re probably going to get an approximate number of them in any given period, and there are some warning signs before they occur, usually.

  15. #15 doug
    September 23, 2009

    Just to add to the complexity of this discussion, the movement of the various plates that give rise to subduction (as contrary as that sounds) are not constant with respect to each other in terms of both velocity and direction. So it is possible that a subduction zone can grow cold, choking off the source of material and energy to the volcanoes it once spawned.

  16. #16 MadScientist
    September 23, 2009

    @Mikhel: The “Vesuvius is overdue” would be made by people who know nothing about volcanoes. With modern tools the deformation of parts of the mountain can be measured manually or with a number of radar instruments on satellites. The seismic activity also gives folks some idea that something is going on – the challenge then is to work out what’s going on and whether it is likely to lead to an eruption. You can bet the Italian vulcanologists are watching Vesuvius very carefully; the area is now densely populated and a large eruption would be a huge crisis. You never hear the vulcanologists watching the volcano say it’s overdue, do you?

  17. #17 Phil Bock
    September 23, 2009

    An important point on Cenozoic eruptions in Australia is the really low proportion of explosive material (tephra). The maars of southeastern South Australia and southwestern Victoria are exceptional, but the volume erupted by them is tiny. These explosive eruptions are thought to be the result of interaction of lava with groundwater-saturated sediments.
    Most eruptions have been of fluid basalt lava, with localised cinders (scoria). With low volumes of lava, deep sources, and low volatile content, then surface deformation is not going to be an important predictive indicator.
    A rough figure for recurrence interval is of the order of 1 in 10000 years, and the most recent are about 5000 years old, so any guesses on hazard are just hand-waving. My guess is that the next one could be out to sea, somewhere south of Mount Gambier.
    On fertility: the land surface material over much of Australia has been exposed to deep weathering with little or no erosion for between 4 and 40 million years, and there is little phosphate left. Land clearing over 100 years ago ensured that the small amount of surface soil was lost by erosion. The introduction of cattle and sheep compacted soils, destroying the existing porous structure.

  18. #18 MadScientist
    September 24, 2009

    @Adam: the dust storm over Sydney is no big deal; that sort of thing is to be expected now and then. The dust storms over China and northern Africa are far more impressive and more frequent. In the case of China the dust has been getting worse over the decades due to the advance of the desert; about 30 years ago the Chinese government got scientists involved with the problem and for over 20 years they have been trying to slow or reverse the desertification by planting trees. I don’t see what global warming would have to do with the Sydney dust, nor is it advisable to make such statements without evidence. Too many people make unsupportable statements which the self-professed skeptics (i.e. deniers) just love to trumpet.

  19. #19 geologistfanatic
    September 24, 2009

    whoever believes there will be a volcanic eruption in Australia before i die obvisously just wants their name in the news and to get their 15 minuets of fame.
    Australia is one of the most geological stable countries on the earth, so saying that we are ‘overdue’ for a valcanic eruption is completely stupid!!!
    If the guy has scientific proof that the pressure inside the volcano is getting bigger then sure, i wouldn’t care if he said there might be a volcanic eruption soon, but he nothing but the past to say we are having another eruption.

    i love geology and hope to become a geologist one day, and i have read every book i have gotten my hand on thats about geology. I truly do not belive that there will be a volcanic eruption any time soon in Australia.

  20. #20 Mike
    October 10, 2010

    Klemetti seems to be at-least-as-guilty of bias as Joyce is, he just chose a different polarity.
    It is perfectly legitimate to refer to the geologic record for a hotspot and make generalized predictions based on previous behaviors.
    At most, one could say Joyce is blurring the distinction between human timeframes and geologic timeframes, which differ by several orders of magnitude. Just because Far North Queensland is due for volcanism doesn’t mean it will happen within the next 50 years; we probably cannot be more precise than +/- 1000 years. But in a relativistic sense, based on analysis of the geologic record, it is not at all unreasonable at all to say that it is “due”.

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    October 10, 2010

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  23. #23 Steve Savage
    November 9, 2010

    I am pleased that you liked one of our photographs so much that you used it in your blog. However, don’t you think you should give us credit for ownership of that pic (the one of the Atherton Tablelands)?

    Maybe a note under the image that it is courtesy of Cairns Unlimited, and a link to http://www.cairnsunlimited.com

    Cheers,
    Steve

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