I wanted to post the new MODIS image of Chaiten that caught the volcano erupting on September 3. I won’t go into too much details, there are a lot of great updates over on the Volcanism Blog, but needless to say, the volcano is still very active, producing tall ash columns (you can see the ash blanket around the volcano in the image above as the plume drifts off to the northwest), earthquakes and pyroclastic flows as the dome in the caldera continues to grow. I’ll be interested to see what geologists know about the eruption and volcano when the AGU meeting rolls around in December as there will be a special session on the Chaiten 2008 eruption.
I’ll be brief (as I’m in the middle of moving), but I did see a report that activity at Chaiten is increasing yet again. This seems like the operating mode for this volcano, with a waxing and waning of intensity, since the volcano started erupting on May 2. The latest report indicates renewed ash emissions producing an ash column that reaches ~20,000 feet (4,000 meters), with ash falling on nearby areas. There is also mention of some increased seismic activity at the Chilean caldera. The picture above shows the extent of the mobilized ash and volcanic debris that has wiped out much of the town of Chaiten (taken from the space station at the end of May).
So, August rolls in and who would have thought in early May we’d still be talking about the Chaiten eruption with such intensity. Jorge Munoz of the SERNAGEOMIN is wondering whether the current eruptive activity and seismicity at Chaiten is a precursor to the end of the “first cycle” (as he calls it) of activity that started in May or that this is all leading up to another major explosive eruption (the “plugged volcano” scenario). The most puzzling part of the current activity is the high amount of seismicity: 105 earthquakes over the last few days, some of them up to magnitude 4. The question becomes: is this magma moving, or volatiles collecting under a “cap” in the volcano’s conduit/plumbing system (or, well, both)? If it is magma moving, we might be seeing the system getting a new input of magma to feed the ongoing, almost continuous ash eruptions. If it is pressure building, then we might be seeing the prelude to another large explosion that could (I repeat could) take out the new dome entirely.
We really don’t have a good idea of the timescales of these giant rhyolitic eruptions, i.e., how long between the initial eruption and a potential cataclysm event like a caldera collapse. The reference points we do have – Krakatau (although not rhyolite) or Katmai, Alaska – suggest that it can take only a matter of days. However, there is also evidence, such as at Santorini in the Aegean Sea, that the initial eruptions/activity could be years before the “big one”. Chaiten might be taking the middle road – or it just might be setting itself up to eruption away for months without ratcheting up to a caldera-forming event.
While we’re on the subject of Chaiten, I wanted to mention a great set of pictures from the area around the eruption on Photovolcanica (thank you to Richard Roscoe). There are some real stunners (see below) of the havoc wreaked by the ash fall, flooding, lahars and pyroclastic flows, along with the state of Chaiten and the towns neighboring the volcano. It is well worth it if you want to see what the region around the volcano has gone through over the last few months.
There haven’t been any major developments volcano-wise over the weekend, just a few updates on some current rumblings:
- Soufriere Hills (Montserrat) coughed up more ash, producing ash columns to “thousands of feet” according to reports from the MVO. The eruptions/explosions were centered at the lava dome on the summit of the volcano, Seismicity has also increased, suggesting that a larger eruption might be in the works.
- Chaiten continues to worry Chilean geologists. Although the eruption seems to have reduced in intensity over the weekend, the fear of a blockage that could lead to a major eruption persists with the SERNAGEOMIN.
- Llaima erupted for the third time in 2008 (see above for a picture of the January eruption) as more lava and ash is erupting from the main summit and a lava flow continues to work its way down the snow fields near the summit.
- Meanwhile, in Alaska, the AVO still lists Okmok’s alert level at Red as it continues to issue ash, upwards of 40,000 feet according to pilots flying near the volcano.
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.
I am beginning to feel like a broken record, but the latest reports from Chile indicate that the ongoing eruption at Chaiten is ramping back up again, almost 3 months after the initial eruption began. As usual, the nitty-gritty details are limited, but reports of increased ash emissions and seismic activity are heralding this increase in activity.
For certain, Chaiten is one of the most important eruptions in any of our lifetimes. This is really not because of the amount of material that has been erupted (although when all is said and done, it will be a significant volume), but rather for the style and longevity of the eruption. A volcanologist friend of mine with more access to details of the Chaiten eruption has said that what we are really seeing is an eruption like might have produced Little Glass Mountain in the Medicine Lake Caldera. However, what is surprising is that the eruption to produce such a feature – a rhyolite dome – has had such longevity and produced so much ash along with the dome. Chaiten had not erupted in ~9,000 years, and more likely than not, a batch of eruptable magma was not sitting just below the surface for that time period – if that was the case, we would have likely seen signs of it such as degassing or seismicity. This means that more likely than not, there was some sort of intrusive event that triggered the eruption, such as the intrusion from depth of a hot basalt magma into a “crystal mush” of rhyolite that tipped the system and caused the eruption. Of course, this is complete conjecture on my part as we really have no samples of the magma itself beyond ash, which can tell us that it is, in fact, the first rhyolite erupted since 1912, but cannot tell us much about the timescales of storage and crystallization. What is really needed as samples of the dome lavas so the crystals (however sparse) can be analysed and dated and any inclusions of basalt(?) in the rhyolite can be sampled. Then we can really start having fun to pick apart the evolution of such a remarkable eruption as the 2008 eruption of Chaiten – remember, even here in the continental US, we have very similar volcanoes (Crater Lake for example) that could see similar eruptions to Chaiten in the future.
The latest eruption at Llaima is beginning to slow down according to Chilean state geologist, Hugo Moreno. The volcano has been erupting for most of the month, forcing limited evacuations. The eruption has (so far) produced lava flows, ash falls and some bombs thrown from the crater. However, the SERNAGEOMIN is keeping the “red alert” on Llaima.
With persistently active volcanoes like Llaima, it is not surprising that they see multiple eruptive periods during each year. In a sense, this is actually better for the people living around the volcano because the more often the volcano erupts, the smaller the eruptions tend to be (however, this is not an unbreakable rule).
I’ll add a link to a youtube video I found for Llaima. I can’t tell from the video which 2008 eruption this is (edit: this is the January 2008 eruption), but some of it is very impressive.
It has been a while since we’ve seen a Chaiten update, but today there is a report that LanChile has had to cancel flights to Puerto Montt due to ash from the volcano. Chaiten has been erupting since early May, so now we’re almost 2 1/2 months into the eruption – quite a feat for such a large eruption! The report also mentions that some residents of the town of Chaiten have been able to visit their homes to collect belonging and the government might just try to rebuild the town in an entirely new location. The USGS plans to send geologists to the volcano later in 2008 or early 2009 to survey the area and collect samples as well.
Llaima (Chile) is experiencing an increased tempo in its current eruption. The National Emergency Office in Chile is reporting that the eruption has begun to take a more explosive character, with pyroclastic material being shot hundreds of meters from the main vent. Although the officials have not changed the current status of the evacuation, which has been limited to 50 people closest to the volcano, they are pondering their next step if the week-old eruption continues to escalate.
The current eruption at Llaima in Chile is causing some concern about flooding in the Rio Calbuco near the volcano. The lava flows are melting snow on the volcano and this is being exacerbated by heavy rain in the area as well. The eruption seems to have waned some according to the governor of the region. This all follows the evacuations of people near the volcano and the red alert issued by the Chilean government. (The picture of Llaima is from the January 2008 eruption.)