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.
12 responses to “Is Chaiten a clogged volcano?”
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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 -
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! -
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 -
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.
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