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”
-
Sometimes I think the term caldera is misused.. I mean you have calderas like Yellowstone, Long Vallley, Toba, Taupo and so on, and then you have calderas like Chaiten, Tambora, Pinatubo.. which although mighty eruptions look more to me like the hole left when you blow the top off a mountain as opposed to the first calderas that are formed by collapse in on an empty magma chamber.. How would you rate Chaiten’s caldera in this regard? Was it formed by collapse in on a shallow magma chamber or is it just the superficial hole after an explosive eruption?
Re the compressional / extensional thing.. what are the mechanics of rising magma.. (this gets back to a question I have long had) .. does the magma rise due to a combination of heat and buoyancy, melting the rocks above it and finding suitable cracks/faults to move upwards and if so, wouldn’t faulting play a major role? What is the geochemistry of rocks on a fault line.. a friend once described them as silly putty.. under great stress already and every now and again snapping… couldn’t the addition of heat from below cause a sudden phase change in rocks that were already close to snapping and therefore encourage upwards movement of magma? The extensional thing explains larger scale bodies like the TVZ because the crust is so thin but faulting is obviously at play locally as Tarawera and Taupo both show (Taupo erupted on a line of vents approx. 50 km long, Tarawera similarly though on a much smaller scale.
Recent posts
Quote of the week
“It’s not far-fetched that almost everywhere in the world where you have volcanoes you have mythologies or new gods being created.”
~ Werner Herzog
Eruptions 
Leave a comment