Chaiten Week 4: Potential for dome collapse?

Chaiten 2008 SERNA
We’ve been hearing a lot of conflicting reports about the state and future of the Chaiten eruption. Now ending its fourth week of eruption, Chaiten was said to be easing up a bit, but recent reports have Luis Lara from the SERNAGEOMIN still worried about a potential collapse, followed by a devastating eruption. I’ll have to take his word for it as the explanations in the article don’t really make a lot of sense. It sounds like both Lara and Dr. Petrinovic (Argentina) are worried about dome collapse, but that would just form large pyroclastic flows … unless the dome collapses enough to release the pressure on the underlying magma, then maybe you could get a large eruption (see Mt. Saint Helens, 1980). I also have some compositional data from ash erupted at Chaiten (big thank you to reader Werner Luis for finding these). Most of the ash is rhyolite (73-75 wt% SiO2), but at least a couple are dacite (64-65 wt% SiO2), which indicates that the composition of the lava/ash erupting has changed during the eruption. There isn’t much context to the data, but it is still interesting nevertheless.
An added note on the flight cancellations by LanChile, apparently the problem is more related to wind direction than increased activity, but both are likely playing a role.

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6 thoughts on “Chaiten Week 4: Potential for dome collapse?

  1. Thanks for both of those reports … the first one has Na2O of ~4.4 wt% for the Chaiten ash, which is in line with the previous eruptions at the volcano. My guess is the initial batch of analyses are suspect with no Na2O reported. Good stuff.

  2. That is a good question … I’m not sure what to expect for lavas from Chaiten (if there are any previously published results at all?) Just looking at other rhyolites, those Na2O values seem real low, although the K2O seem reasonable … Just all the more reason to be able to get there and take our own samples, eh?

  3. Hi Erik,
    really interesting post. What do you make of the low-to-no sodium numbers in the rhyolite? Is that common?
    adios,
    jon

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