It is hard to believe that the eruption at seem to come out of nowhere at Chaiten started over 8 months ago now, and apparently is still not showing many signs of abating. I did get a chance to see some great talks and posters at AGU last month about the Chaiten eruption, with the key points I took away being that Chaiten is erupting a very crystal poor rhyolite (<1% crystals) and that it seems that the source of the magma is relatively deep in the Andean crust. Also, there are some indications that the eruption at Chaiten may have been tectonically instigated – i.e., that earthquakes in the area might have helped the magma to erupt – at least that is what Luis Lara of the SERNAGEOMIN believes (hat tip to Thomas Donlon for the link). The eruption at Chaiten also wreaked more havoc on aviation in South America than we thought, effecting airports 1000s of kilometers away and almost bringing down a number of aircraft. Most everyone I talked to seems to think what we are seeing is very similar to what happened at Little Glass Mountain in California about 1,000 years ago.
Moreover, the eruption hasn’t really stopped since it began in May of 2008. In fact, just last week we saw a collapse of part of the new dome that have produced some pyroclastic flows within and outside the caldera (see above and the Volcanism Blog) and fed more ash into the choked rivers near the volcano. It is anyone’s guess (well, at least at AGU) how long this eruption might go on – weeks? months? years? – but the consensus is that this might be a once-in-a-lifetime eruption (but we already knew that, didn’t we?)
13 responses to “Chaiten update for 2009”
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Just read one of the abstracts (Lara, Pallister et al) and the word “compression” appears several times… QUOTE: “We propose a model for magmatism at Chaitén, in which the timing and compositions of eruptions are controlled by tectonism along the Liquiñe-Ofqui Fault Zone (LOFZ), a 1200 km long structure that is part of a dextral transpressional arc domain. In this model, silicic magmas are trapped and stored at deep levels of the crust (10 km?) during periods of upper crustal localized compression, and eruptions are triggered by tectonic shifts that open tear faults and promote magma transport to the surface. Consistent with seismicity along the LOFZ and subsidiary branches before and during the eruption and with new InSAR data that indicate fault-controlled syn-eruptive deformation, we suggest that such a process triggered the 2008 eruption and that re-establishment of compression, following the initial Plinian phase, has sustained an anomalously high-rate of lava production for the past four months. ”
Dr. Klementi, Do you remember your doubt in previous “Is Chaiten a clogged Volcano” entry? QUOTE: “Technically, I’d be surprised if compressional movement would cause volcanism as typically one associates volcanism with extensional movement.” Technically it has been answered. -
Have not read the abstracts yet, but a tectonic cause has been in my agenda for long. Other points of interest in the agenda are:
1.- The eruption is part of a process of tectonic “accomodation” going on since May 21st 1960. It should involve other volcanoes along the Liquiñe Fault. It has involved so far two Major earthquakes (1974 and 1975), the 1991 Hudson eruption (VEI 5), the Aysen fjord swarm.
2.- The Chaiten eruption is a “vent” eruption from the Michimahuida Volcano a few miles northeast. (Deep magma, lots of water from melting ice or from sea basin)
Regards from the Nazca Plate Subuction Zone! -
A little off topic here but looks like things might be heating up at Redoubt.
Check out AVO’s site:
http://www.avo.alaska.edu/activity/Redoubt.php -
Bruce – I don’t think we have a good idea of that exactly the effect of a deep source might be on the chances of a caldera-forming eruption. However, we know that Chaiten has had a caldera-former before, so unless the processes that form the magma at Chaiten has changed dramatically since that time, it isn’t out of the question.
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