Chaiten to bury Chaiten

I’ve been trying to keep up with the Chaiten eruption in Chile, but the news is just beginning to sound like a broken record: eruption continues, ash falls, don’t know much else. However, it does sound like Chile is being realistic about people’s chances of moving back to the town of Chaiten – 10 km from the vent(s) – in the near future … and those chances are zero to none. This doesn’t entirely surprise me. If the town isn’t already buried, when the pyroclastic flows do start, whether they be from the collapse of the the eruptive column or from the vents themselves, the town will be wiped out. Chilean President Michelle Bechelet is quoted as saying ““We have never had a situation quite like this in Chile” and she’s quite right. In fact, I don’t think there is any country in the last 100 years within quite this sort of situation short of the Philippines and Mt. Pinatubo, but that is beginning to look like small fry in comparison. 
However, I do have to take umbrage with this paragraph from the Patagonia Times report:

The Chilean daily La Tercera reported on Sunday that a SERNAGEOMIN study had put the odds of such a collapse as at least 50 percent. The document said that there was increased build-up in the dome of magma currently covering the volcano’s crater. Futhermore, the material accumulating in the area was “highly dense,” and thus more prone to collapse. SERNAGEOMIN said that any implosion would cause complete destruction of everything within a 15 kilometer radius around the peak, an area which encompasses Chaitén, Santa Barbara, and several rural farming villages.

OK, well, that is a surprise that the SERNAGEOMIN thinks that we have 50-50 odds of a collapse of the edifice now. Alright, that is not that much of a surprise, but to say it at this point likely means it is becoming more likely than not. However, I can assure you it has nothing to do with lava erupting from vents in the caldera being “very dense”. One, volcanoes don’t collapse from piling stuff onto them, the collapse from emptying what is underneath. Two, the magma being erupted is likely rhyodacite or rhyolite, which is the least dense of all lavas. Three, I’m guessing this is reason given is probably caused by something being lost in translation. If Chaiten does collapse, it will be because the eruption has emptied so much material from the magma chamber below the volcano that the edifice itself no longer has a foundation and it will collapse into that space (see also, Crater Lake, 7700 years ago).

On my random speculations

Before we get too far, I wanted to make sure that folks understand that I’m just making educated conjectures on the nature of the eruptions I read about and by no means do I have any extra insight over those scientists on the ground at the eruption. I have a very limited set of data to examine – whatever the media reports – so I am just speculating based on what I know about the eruption style, volcano in question and whatever other variables might come into play. So, please, don’t think that I know exactly what is going on or what will happen better than the scientists tackling the volcano firsthand.
That being said, I might not be a big fan of Donald Rumsfeld, but he does divide things up nicely when it comes to assessing a situation, so here we go.
For Volcan Chaiten:
Known knowns: The volcano has been erupting for the past week; large ash column up to possibly as high as 90,000 feet (!); thick ash deposits (>30 cm) out 10s of km from the vent; potentially lava extrusion at the vent; no pyroclastic flows, no lahars (so far); two discrete vents have coalesced into one vent; upwards of 2 cubic kilometers of erupted material (thus far); last known eruption at Chaiten was 7450 BC, or roughly 9,500 years ago.
Unknown knowns: How long will the eruption last?; how long until the supply rate of pyroclastic material from the vent drops below the rate needed to keep the ash column aloft?; when the ash column collapses, how big will the pyroclastic flows be?; will lahars begin to be generated?; will the volcanic edifice collapse due to the eruption? if so, will there be pyroclastic flows generated by the collapse and/or ring vents forming?; is this the main eruption or will things get bigger? how much lava will be extruded at the main vents? will more vents open?; how long until people can get near the vent to see what has occured firsthand?
Unknown unknowns: Well, I can’t really speculate of these, now can I?
At least we know that Chaiten spared the berry crops!

The Chaiten eruption hits one week

This marks a full week of eruption at Chaiten and the volcano shows no signs of abating.
You have to feel for Luis Lara. He is apparently the pointman for the SERNAGEOMIN in regards to this eruption and really, I think its anybody’s guess what might happen next. Heck, we haven’t seen many eruptions of this scale – and this out-of-the-blue – since the birth of modern volcanology, so we’re testing a lot of hypotheses now. What Dr. Lara says is that the eruption is still going strong, lava flows seem to be occurring at/near the vent but not spilling out of the caldera, the two vents have coalesced and the ash column still hasn’t started to collapse. Interestingly, rivers coming from the Chaiten area have risen in temperature 7-17 C, which is quite remarkable. My guess (emphasize guess) is that the water from the two (former) lakes in the caldera is mixing with the erupting material, however I have yet to hear any real reports of lahars (a volcanic mudflow). Ash has made it all the way to Porto Montt, 200 miles to the north (prevailing winds in southern Chile head east) and Dr. Lara says at least 2 cubic km of pyroclastic material has been erupted thus far. For comparison, Mt. Saint Helens 1980 was much less than 1 cubic km.
So the question becomes: how big is this eruption going to get? Are we talking about an eruption that is Pinatubo scale? Crater Lake? Valley of 10,000 Smokes? Taupo? Toba? (OK, it has got a long way to go before we hit those last three magnitudes). Nevertheless, this is quite a rare event. Too bad (for me) that it is about as far away as it could be from my present location in California.
Of course, to go with this eruption and the cyclone in Myanmar, there is a lot of real shoddy journalism going around, trying to make links between events. This article (from Fox News!) tries to break the links, but in such a way that is sure to make the folks waiting for Ragnarok or the Rapture gleeful. I always hate it when students use the phrase structure “Scientists say …”, which is, of course, in the title of this article. Yes folks, the Earth is a hazardous place … well, at least to us humans.

Ubinas, Peru

There are, indeed, other volcanoes erupting right now worldwide other than Chaiten. Of course, when you have an eruption like Chaiten going on, it is hard to pay attention to other eruptions.
Ubinas, Peru

Ubinas, in Peru, has been having intermittent ash eruptions for the past few months, depositing ash on the surround communities. Apparently these eruptions have been causing some respiratory ailments to the local Peruvians due to the ash & volcanic gases. Ubinas is one of the most active volcanoes in Peru. This picture shows Ubinas erupting in 2006, as captured from the International Space Station (ISS).
Edit: Fixed “Ubinas is one of the most active volcanoes in Chile” to correctly say “Peru”. Yeah, I always seem to have Chile on the brain. Darn Aucanquilcha and Chaiten! Thanks Jon!

Chaiten Eruption, Day 7

Another day, another development at Chaiten. Military stationed near the volcano helping with evacuations reported “booming noises” and saw incandescent blocks getting hurled from the vent area. This suggests that lava is at the surface and potentially that the edifice itself is beginning to crack/strain from the loss of material from the eruption. Remember, when you erupt all this volcanic material, you leave a void under the volcano where that magma used to be, so suddenly you have a volcano with no foundation. Sometimes they can founder into that space, forming a caldera. We already know that Chaiten has experienced a caldera-forming eruption before, so it isn’t out of the question.
At the same time, the SERNAGEOMIN says this eruption could go on for days, weeks, maybe months. The big question on everyone’s mind is when the pyroclastic flows will begin, either from eruptions from ring vents in the caldera or from the gravitational collapse of the ash column. Either way, these pyroclastic flows are hot (>>300 C), fast (>100 km/h) and deadly (see also, Mont Pelee). Once the pyroclastic flows start, everything remaining close to the volcano (10s of km) will likely be wiped out.
Looks like we might have a new champion for “largest eruption of the 21st century”!
Edit: Fixed first link (Thanks Bloodfist)

Air travel in Patagonia

The eruption at Chaiten has now begun to have widescale effects on the region of Patagonia, beyond the ashfall. Air travel has been disrupted due to the amount of ash in the air. It is well-documented that ash posed a significant hazard to aircraft, so this seems like a wise move on the parts of Argentina and Chile. 
Not much else new to report beyond that the fact that this eruption is now into day 6 without any signs of letting up. Impressive to say the least.

One more Chaiten Image

NASA captured this great image of the ash plume from Chaiten, which has reached 15-km into the atmosphere.

Following this eruption, I’m sure there will be a lot of work into why no one had any clue an eruption of this magnitude was about to occur.

Chaiten gains force

Well, this is getting rather harrowing. Volcan Chaiten, the Chilean volcano that sprung back to life last Friday after anywhere between 2,000 to 7,000 of quiet, is apparently erupting lava along with ash now. Sounds like its a good rhyolite/rhyodacite lava based on the description: “very small and very thick and as such was moving slowly so it is moving very slowly”.
Chilean officials are now fearing that the volcano is in “worst case scenario” mode – although, they never mention what that might be: full-on caldera? topography-erasing ignimbrite? Pinatubo-scale eruption? However, the SERNAGEOMIN says the eruption has “reached its climax.”
The real problem right now is less the eruption (which is still a problem) but more the collateral issues like water/food supply that can be easily spoiled by ashfall. Look for this to become a humanitarian effort soon, but luckily the region isn’t densely populated. Upwards of 30-cm of ash has fallen on many parts of the area. Currently, 12,000 residents of the area have been evacuated.

Chaiten Images

Monsters and Critics has some truly fabulous images of the ongoing eruption at Chaiten in Chile.

The pictures of the extent of ash fall are quite remarkable. It is hard to tell exactly how deep the ash is or how far from the vent these pictures were taken, but one can imagine that if a helicopter took them, then they are relatively far from the action. The Chilean President, Michelle Bachelet, toured the area to see the damage. Stunning stuff.

Chaiten Eruption Update 2

Update 5/4/08: Looks like there is now officially a deathtoll for Chaiten, as an elderly woman died during the evacuations. The volcanoes continues to spew ash and I wouldn’t be surprised if it did so for at least a few more days. There have also been reports of a sharp increase in earthquakes in the area since the eruption. Now, before everyone goes nuts, this could be just a response to the dramatic release of pressure caused by the eruption, possibly faulting in the caldera walls activated by the eruption, or possibly magma working its way to the surface as the eruption progresses. Now, whether this means the eruption is waxing or waning, it is hard to say from the information I’ve been able to find, but it definitely will keep us on our toes.