Is Chaiten a clogged volcano?


ONEMI, the Emergency Office of Chile, is expressing concerns that Chaiten might be readying an even bigger blast than what we’ve seen already in the past few months. In particular, ONEMI direction Carmen Fernández is concerned that the volcano might have a major explosion with accompanying ash fall and pyroclastic flows. They are pointing to the increased seismicity at depth under Chaiten as potential evidence that the conduit to the surface is partially blocked, and thus building pressure for a large explosion – think Augustus Gloop in Charlie and the Chocolate Factory if you want a mental picture.
Now, it is hard to tell from the evidence in the article whether this seems likely or not, but usually deep seismicity under a volcano means that magma is moving – and when magma is moving, it is usually moving upwards to the surface, which means eruption if it makes it all the way. The SERNAGEOMIN agrees with some of the ONEMI suggestions (covered nicely on the Volcanism Blog), but overall, the feeling I get from reading these reports is that the Chilean officials are playing this with an abundance of caution, and rightly they should. As I’ve mentioned, we are now in somewhat uncharted seas when it comes to historical volcanic eruptions in the modern era, so making a prediction for Chaiten’s next move is tricky business.

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12 thoughts on “Is Chaiten a clogged volcano?

  1. Hello,
    I think we cannot clearly answer the question weather Chaiten is a clogged volcano. How do you defined clogged? Of course the mechanism is rhyolitic and therefore we are talking about viscous material.
    A seismic network registering local earthquakes before the Chaiten eruption showed clearly activity along the Liquine-Ofqui fault zone and earthquakes below Chaiten volcano:
    a.) One type of earthquake activity related to the volcanoes Chaiten, Corcovado and Michinmahuida, and another one related to the Liquine-Ofqui Fault zone. There were unusual stronger events in the crust before the eruption, these events occurred August 2005 about 10 km S of the city of Hornopiren with magnitudes up to 3.8 M.
    b.) Chaiten is located on a SE-NE striking secondary fault of the Liquine-Ofqui Fault. The events along the fault and below Chaiten occur in 10 km depth which is normal for this kind of mega strike slip faults. Because all the events are strike slip events there doesn’t have to be necessarily compression everywhere.
    On the AGU I’ve seen a Poster showing the actual seismicity in the same depth range, about 10 km. Which depth range you mean when you write about unusual deep events below Chaiten above?.
    There were some unusual events before the eruption
    The background seismicity of the northern part and the southern part of the LOFZ shows some seismicity, while the central part did not had any bigger crustal earthquakes clearly related to the crust during the last decades.
    Before the eruption Chaiten had at seismicity up to magnitude 3.6 M, from the seismicity and fault plane solutions it looks like if there is a conjugated fault system below Chaiten and Michinmahuida. Beside the Aysen events 2007 in the South there was another unusual deep earthquake in the region around 2007. The north-south extension of the Liquine-Ofqui fault zone coincides spatially with the NS extension of the 1960 earthquake.
    For a detailed discussion about the tectonic setting and seismicity of the region and the Liquine-Ofqui fault i would like to refer to our article in Tectonophysics from 2008:
    doi:10.1016/j.tecto.2008.04.014
    Regards
    Dietrich

  2. Tom, Add two more “specials” to the 1950 earthquake storm:
    1950 03 07 0803 -8.00 -71.00 8.60 MsPAS
    1950 12 09 213848 -23.50 -67.50 100 8.30 MsPAS
    The first one, although shows no depth, surely was at the 550-600 Km deep range, since it is followed by several major earthquakes at that depth in a few days time lapse. This makes it the bugger ever earthquake at extra deep range.
    The seconf one took place 100 Kms under the “aguas caliente” salar complex where at Lascar volcano is located and surely is the strongest earthquake at that depth known so far.
    The 1994 06 09 Bolivian extra deep earthquake at 8.2 Mw magnitude is another example at 631 Kms depth.
    Regards from the Arica at the Nazca Plate Subduction Zone!

  3. Sorry, about two posts. I didn’t think my first post went through and I condensed the post into a shorter post that I thought would fit through the filter as I supposed there was an unstated limit on the size of a post.
    BTW – have you read the article at
    http://news.bbc.co.uk/2/hi/science/nature/7435324.stm
    which deals with an apparently very promising method of short term earthquake prediction?
    “Researchers say they have found a close link between electrical disturbances on the edge of our atmosphere and impending quakes on the ground below.”
    Apologies again,
    tom

  4. Eric and Rafael,
    In an article about the large Vilama Caldera, which – “may, in fact, be just one of several unappreciated supervolcanoes hidden in a veritable mega-volcano nursery called the Eduardo Avaroa Caldera Complex, located in the inhospitable Puna-Altiplano region near the tri-section of Argentina, Bolivia, and Chile.” – there is a complex process described of producing magma.
    The article is at
    http://www.sciencedaily.com/releases/2006/03/060328183109.htm
    Quoting geologist Miguel M. Soler of the National University of Jujuy in San Salvador de Jujuy, Argentina, the article says,
    “Vilama’s magma was probably created by a more complex melting of the crust caused by the South American Plate colliding with and overriding the Nazca Plate to the west. The resulting kneading of the crust — the thickening and thinning, pressurizing and depressurizing — caused large pockets of rock to melt and eventually led to a series of gigantic caldera eruptions.”
    I am not sure what “extensional” forces are Eric. (I am not a geologist – and have no training in it.)
    I don’t know if the link above postulates different forces producing that eruption than what either you or Rafael are suggesting.

  5. Eric and Rafael, there is an article on the large Vilama Caldera, which says that it – “may, in fact, be just one of several unappreciated supervolcanoes hidden in a veritable mega-volcano nursery called the Eduardo Avaroa Caldera Complex, located in the inhospitable Puna-Altiplano region near the tri-section of Argentina, Bolivia, and Chile.”
    As far as compressional forces leading to a volcanic eruption, it certainly may be one factor.
    The article at
    http://www.sciencedaily.com/releases/2006/03/060328183109.htm
    Quoting geologist Miguel M. Soler of the National University of Jujuy in San Salvador de Jujuy, Argentina, the article says,
    “Vilama’s magma was probably created by a more complex melting of the crust caused by the South American Plate colliding with and overriding the Nazca Plate to the west. The resulting kneading of the crust — the thickening and thinning, pressurizing and depressurizing — caused large pockets of rock to melt and eventually led to a series of gigantic caldera eruptions.”
    Another possible trigger creating current volcanic conditions is the recent huge earthquake in Indonesia. “”The four biggest earthquakes of the 20th century all happened within 12 years of each other, a pattern we see repeated with other quakes over many decades,” said Vladimir Kossobokov of the International Institute of Earthquake Prediction in Moscow.” He says, “They found that quakes such as the one in Indonesia can destabilise the whole of the earth’s crust, so that one is followed by others, often thousands of kilometres away, within a few years.”
    The article mentions specifically the big earthquakes of the 1950s and 1960s.
    “The series of four last century that exceeded magnitude 9 on the Richter scale began with a quake in 1952 in Kamchatka, …
    Another hit the Andreanof Islands in Alaska in 1957, …
    The biggest and most destructive quake hit Chile three years later,… producing a 23m-high tsunami that caused chaos across the Pacific.
    The last of the cluster hit Alaska in 1964, killing 130.”
    Another large transcript of BBC show titled
    Earthquake Storms – transcript – is available to read at
    http://www.bbc.co.uk/science/horizon/2003/earthquakestormstrans.shtml
    They give strong evidence for an earthquake storm around the Mediterranean for a twelve year stretch.
    From approximately the 360 AD this article says, “EMANUELA GUIDOBONI (WITH TRANSLATION): There had been seven earthquakes before 365 and three afterwards, so in 12 years there were 11 earthquakes, almost one earthquake a year. There was a seismic crisis in the Mediterranean.”
    The transcript provides evidence of various sorts that this earthquake storm took place.
    So we shouldn’t rule out that there can be periods of time of heightened earthquake or volcanic activity.
    My points –
    1) Various forces not just extensional can result in eruptions. (However, I am not a geologist and really don’t know for sure what “extensional” means. However, the article I cited on the Vilama Caldera spoke about complex process resulting in the eruption there. (Are these forces all extensional?)
    2) Earthquakes prompting other earthquakes and earth movements elsewhere do happen – but of course the science of predicting how and why this will happen needs more work. Earthquake and volcanic eruption prediction right now is not much more advanced than aviation was in the decade after the Wright brothers flew their first plane. It is still dangerous and unreliable – showing much promise for the future. There needs to be much effort and inter-disciplinary cooperation for this science to advance. And there is – I am pleased to be learning a little of what is happening.
    PS. Now Chaiten apparently does not emit much SO2 (Sulfur Dioxide) which can cool the planet. Now if Chaiten has an explosive enough eruption (and I think it mostly has a lot of Rhyolite perhaps with a lot of pressurized gases stuck in its very viscous magma probably rising upward to be de-pressurized) – if it puts lots of ash particles high into the stratosphere this too can change the climate somewhat? Correct?

  6. Rafael:
    Que tanta teoria, cualquier paisano sabe que “donde mucho se aprieta la salsa, algo rebalsa”.
    Estuve mirando tu blog, muy bueno!!

  7. Thanks for some of those clarifications, Rafael, along with some of those interesting theories on the interconnected of events. At this point, you’d be hard pressed to be able to match events up one-to-one in a cause-and-effect fashion, but coincidences are there – what they mean is up for conjecture. Technically, I’d be surprised if compressional movement would cause volcanism as typically one associates volcanism with extensional movement. And I’m sure if we had more monitoring of Chaiten prior to the eruption, we might have seen more signs of this eruption, however you can’t wire up every volcano that has erupted in the last 10,000 years – well, at least not on most countries budget for science!

  8. 1.- The USGS report rates the Chaiten eruption as VEI 5.
    2.- The Chaiten caldera is the large crater at the top of the mountain, not the mountain or its surroundings. Within this crater there was an old dome which has now been obliterated by the first eruption on May 02. On May 24th, a second dome began to form at the side of the first eruption’s one.
    Pictures can be accessed at:
    http://sismoaysen.blogspot.com/
    3.- What is going on under the chaiten mountain, or for that matter under the Hornopiren (dormant volcano) mountain or the now erupting Llaima volcano is anybody’s guess. My guess is that since the Puerto Aysen seismic swarm from Jan 23rd 2007 through April 24th 2007 (thousands of microseisms, several magnitud > 5.0 Mw and two of magnitude = or > 6.0), and subsequent movement of the eastern portion of the Liquiñe-Ofqui Fault in a northernly direction (several meters), the compression caused by this eastern territory movement has resulted in: first the Chaiten volcano VEI 5 eruption (May 02 2008) which has now been going for almost three months, secondly the Hornopiren seismic activity further north (May 24th 2008) and the Llaima volcano even further north which has been active on and off since Jan 01 2008.
    4.- What caused all this activity is also anybody’s guess. My guess is that the chaos theory that has been accepted by scientist so far has impeded science to look beyond or far back from a particular event and see what might otherwise be obvious. That is, seismic and volcanic activity in a fault system such as the southern chile subducting arc and corresponding fault could be considered as a continuing series of events and movements. In the case being reported today, the origin of these events could be the mega earthquake of May 22nd 1960, a series of Big, Major a Strong earthquakes which started on May 21st 1960, run in a southernly direction for AS LONG as the corresponding Liquiñe-Ofqui FAULT and parallel to it, for months, even years, recurring once and again until at least 1974/1975 (last two Major earthquakes 7.0 and 7.8 Mw magnitude). On 2004 two strong earthquakes took place close to the 1974/1975 sites and since then, nothing happened until the people at Puerto Aysen began fearing for their lives under the stress of the seismic swarm starting on Jan 23rd 2007. The mega earthquake seismicity map can be accessed at:
    http://rafaelperalta.blogspot.com/2007/02/map-of-big-earthquake-1960-05-21-has.html
    Much regards from Arica, at the center of the Nazca Plate Subduction Zone

  9. Brian – I think I’ve heard it is somewhere in the vicinity of a VEI 5-6 although there is some debate about the magnitude of the initial eruption. I would imagine that any new increased eruption would be in that same vicinity. It is actually pretty hard to get higher than VEI 6 without going into that Yellowstone/Toba vicinity.
    As for the mountain vs. caldera, based on what I know about Chaiten, the “mountain” itself is a resurgent dome within the Chaiten caldera itself. The resurgent dome is formed by eruptions after the caldera-forming eruption, usually close to the middle of the caldera. If, for some reason, Chaiten does have a new caldera-forming eruption, then yes, likely the mountain that people are familiar with at Chaiten would likely not survive.

  10. Just curious, how big approximately was the last eruption a few months ago, on the VEI scale? If this one is bigger, it could be real intersting.
    Also, I understand the caldera is actually bigger then the mountain (please understand I am not a scientist). Could this eruption expand outside of the crater and even destroy the mountain that is there?

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