Meanwhile in Italy, Etna had yet another paroxysm, this time less than a week since its last one. This one produced a significant ash plume with lava fountaining, but little-to-no lava flow activity. One of the more impressive videos I’ve seen for the eruption was one taken by hikers on Etna who had basaltic scoria rain down on them. VolcanoDiscovery also posted a time-lapse of yesterday’s eruption.
Etna in Italy erupting from two vents simultaneously on October 26, 2013. Image: Dr. Boris Behncke / Flickr.
Sometimes it takes as many days as the meeting to catch back up afterwards — which is clearly the case for me after GSA this year. Finally getting almost on track as we hurtle into November.
Volcano news!
Italy
So, like clockwork, right as I leave for Denver and the GSA meeting, a volcano decides to put on a show. This time it was Etna. After six months of relative quiet, the Sicilian volcano put on quite an impressive show (see above), with eruptions from two craters simultaneously: the New Southeast Crater and the Northeast Crater (see above). Both of these eruptions were explosive, producing plumes that reached a few kilometers over the volcano and spread ash across the area of eastern Sicily. At the same time, a lava flow issued from the saddle between the two crater, meaning that Etna has erupting from at least three different vents simultaneously during the October 26 eruption. Dr. Boris Behncke of the Osservatorio Etneo posted an excellent video of the action during the 10/26 paroxysm that shows the lava fountaining that occurred from the New Southeast Crater. Towards the end of the video, you can see some great examples of strombolian activity during the waning stages of the eruption from the New Southeast Crater as giant bubbles pop in the conduit of the erupting vent. Each “pop” of that bubble would send out thousands of lava bombs, and created the booming sound you can hear on the video. Dr. Behncke also posted a great sequence of images and a story behind the remnants of a former volcano observatory on Etna. Right now, only the antenna of the former building sticks out above many years of volcanic debris, but the October 26 paroxysm lava flow came with 1 meter(!) of knocking down even that last vestige of the structure. Things have settled down at Etna after this eruption, but as we all know, the volcano can ramp up quickly to a new paroxysm.
Indonesia
Across the world in Indonesia, Sinabung continues to produce explosive eruptions. Right now, these discrete event have been producing ash plumes that reach up to 7 km (23,000 feet) over the volcano. All of this activity at Sinabung prompted the PVMBG to raise the alert status at the volcano to its second highest setting (siaga – alert). This move increased the exclusion zone around the volcano to 3 km and ~1,300 more people have evacuated the slopes of the restless volcano. Elsewhere in Indonesia, looks like people want to add some fearmongering to the menu (as if actively erupting volcanoes weren’t enough). The IB Times has an article proclaiming “Lake Toba’s Volcanic Underbelly ‘Could Erupt at Any Time’“, snatching a poor choice of words by the president of the Indonesia Geological Experts Association, Rovicky Dwi Putrohari. The article itself sounds like an attempt by the IGEA to promote its annual conference that occurred this week — nothing like capitalizing on fear of the next eruption from a caldera to grab the media’s attention.
Landsat 8 OLI image of Iliwerung in Indonesia on Lembata Island, seen on August 12, 2013. The dark grey area is the volcanic complex, while the grey box marks where the new submarine eruption from the Hobal vent is likely occurring. Image: USGS/NASA.
Interesting news coming out the of the East Nusa Tenggara Province in Indonesia. An undersea volcano off of the southern coast of Lembata unexpectedly erupted over the last few days, producing strongly discolored waters and a plume (likely made dominantly of steam) that reached 2 km (6,500 feet). The latest GVP Weekly Volcanic Activity Report also mentions incandescence noted at the sea’s surface. According to news reports, the volcano is called “Mt. Hobalt”, however, in the Global Volcanism Program‘s database, no such volcano exist. There is a Hobal that is part of the larger Iliwerung complex in the right area of Lembata, so this seems to be the volcano that is erupting. This volcanic complex has been producing diffuse fumarolic activity since the beginning of the month and the PVMBG noted that seismicity has increased sharply in this area as well. This new eruption from Hobal has prompted the PVBMG (Center for Vulcanology and Geological Disaster Mitigation) to put Hobalt on a Level II alert and warned fishermen and tourists to avoid the area. There have been some fears that this activity near the coast could produce a tsunami, but so far those fears are unfounded. This would be the first eruption from Iliwerung since 1999 and much of the eruptive activity at Iliwerung has been from Hobal since 1973. The last known subaerial eruption from Iliwerung was in 1948 (but records can be incomplete across Indonesia).
Meanwhile, the continued eruptions at Rokatenda has caused a larger-scale evacuation of the region around the volcano. Seven hundred housing units are to be constructed for people who have had to leave their homes since October 2012 due to the ongoing activity. Recently at least 6 people died from a pyroclastic flow that swept across a beach where villagers were living on the island volcano.
Shot of a new lava dome seen on July 7, 2013 forming within the main crater at Mexico’s Popocatépetl after a week on continuous strong ash emissions and explosions. Image: CENAPRED.
Programming Note: I’ve now entered summer crunch time. Between lab time and field work with my students over the next month along with my own projects and manuscripts that need to move forward before the start of the next school year, I am going to be busy with a capitol B. I’ve going to try to keep up with posts as events occur, but I can’t guarantee that I can update as quickly and frequently as I normally do, at least not until this stretch is over. Hopefully this helps dispel that myth that someone college faculty have the summer “off” … !
Onwards to the update!
As noted in this space last week, Popocatépetl has had an active week, to the point that a multitude of flights in/out of the international airport in Mexico City were cancelled. This huffing and puffing at Popocatépetl, with ash plumes reaching 3-4 km above the volcano, has prompted the elevation of the alert status to Yellow-Phase III. This means that the eruption at the volcano has moved from sporadic explosions (Phase II) to frequent small to intermediate explosions, usually caused by a dome collapse (that can generate pyroclastic flows). Tremor is almost constant at the volcano, along with constant emission of ash-and-steam from the summit vent.
An overflight of that vent on Sunday showed that a new lava dome has formed within the crater during the past week’s activity (see above), meaning a new sequence of dome growth (and eventual collapse) is in full swing. As magma rises up under the active vent, a plug of lava forms (as the lava dome). The pressure rises under the plug and it is eventually destroyed (either by collapse or explosion), leaving the magma underneath to feel the drop in pressure, prompting an explosive eruption. Once the vent is clear, new lava can begin to fill in the vent to form another new dome and the cycle continues.
This type of eruption is common at many arc-related volcanoes like Popocatepetl like Mount St. Helens, Soufriere Hills and Merapi. You can check out this USGS page on this same pattern that occurred at St. Helens after the catastrophic 1980 eruption or if you want to get cozy with a dome, check out this video of the dome at Mexico’s Colima taken in 2008 — rubbly piles of extruding lava within the main crater vent. The collapse of these domes can be one of the most dangerous and unpredictable events at a volcano as the extrusion of the dome isn’t particularly violent, but the collapse can generate large pyroclastic flows. A collapse of a dome at Unzen killed the famed volcanologists Maurice and Katia Krafft and Harry Glicken in 1991. The dome at Popocatepetl likely needs to get larger so it extends out of the crater at the summit vent (see above) before it can generate a large dome collapse pyroclastic flow, but all of this means that Popocatepetl needs to be taken seriously in this new phase of activity.
Small (but still hazardous) explosive eruptions from Kilauea in 2008 might require a tweaking of the Volcanic Explosivity Index (VEI). Image: HVO/USGS.
Much of the discussion of volcanic eruptions tends to center on the big ones — those monstrous eruptions that really capture everyone’s attention, potentially plunging parts of the planet into a cool spell that could last years. Those eruptions are relatively rare, coming a few times a decade for the smaller ones and a few times a century (or longer) for the real colossal blasts. It is true that those are important events to understand, especially because humanity will need to face life after a giant eruption like Tambora or Taupo someday in the future. However, all this focus on the enormous eruptions ends up leaving those “everyday” events in the cold. Even if they are small, they can have a profound effect on local areas, especially if they are places that are highly frequented by tourists.
Some background on the scale of volcanic eruptions: The Volcanic Explosivity Index (VEI; see below) was devised as a way compare eruptions (mainly explosive eruptions) much in the same way we compare earthquake magnitude using the Richter Scale. It was developed mainly to discuss eruptions that have an impact on global climate (that is, the big eruptions). The VEI is based on the volume of volcanic tephra (debris of explosive eruptions, like ash and bombs) that the eruption produces, so VEI 0-1 eruptions produce small amounts of tephra, only ~10,000 m3 (picture a cube with ~21.5 meter / 70 foot sides) while the VEI 7-8 eruptions produce a remarkable 1,000,000,000,000 m3 (take that cube and make it 10 km / 6.2 miles on each side). A VEI 7-8 eruption is actually 10 million times more productive than a VEI 0-1, however across the Holocene (the last 10,000 years), there have been only 6 eruptions that make it into into the heady VEI 7-8 territory while there have been at least 2215 VEI 0-1 eruptions that we know of. I emphasize this idea because a VEI 0-1 eruptions leaves little to be preserved in the geologic record — maybe a mere dusting of ash or a small lava flow — so this value is minimum value for these eruptions*.
The Volcanic Explosivity Index with volumes and terminology as currently defined. Image: Table 8 from Siebert et al. (2010), Volcanoes of the World, 3rd Edition.
That being said, if you’re standing near the vent of a 0-1 explosion, well, you can still get hurt or killed. Volcanic debris is heavy and it is thrown out of the vent at high speeds, so even a small explosion can be hazardous in places where people frequent. You might notice on the VEI that these very small explosive eruptions, those under 10,000 m3 fall into the VEI 0 category, which is described as “gentle”. That is because this is where the VEI breaks down and treats all eruptions that produce small volumes of tephra (remember, explosive debris) as effusive eruptions — that is, eruptions that produce lava flows. However, this is not the case in many places. The eruption of Mayon in May 2013 was a tiny phreatic (steam-driven) explosion that was likely VEI 0 but it killed 5 climbers who were near the vent when it occurred. That would hardly be considered as “gentle”.
Similarly, in 2008, Hawaii’s Kilauea produced a series of small explosive eruptions from the Halema’uma’u summit vent and this is detailed in a recent paper by Bruce Houghton and others in Geology. These explosions only produced 10-310 m3 of tephra, but due to the close proximity of the vent to tourist attractions and roads, they could have inflicted significant damage and injury if, let’s say, a tour bus was caught in their path. Thankfully this didn’t occur in 2008. These explosions were very small strombolian- or Hawaiian-style eruptions that would likely never have been noticed in the geologic record except for the fact that the Hawaii Volcano Observatory is right there, next to Halema’uma’u, to see it all happen. Clearly, these eruptions, although technically VEI 0, were not effusive or gentle. How can we handle such events?
A revised version of the VEI to account for very small but still explosive eruptions, as suggested by Houghton and others (2013). Image: Figure 5 from Houghton and others (2013).
Houghton and others (2013) suggest we might need to tweak that VEI scale to account for smaller explosive eruptions. However, we don’t want to disrupt the definitions for VEI 1-8, so they suggest we project downward, so the 2008 eruptions at Kilauea would be VEI -2 to -4 (see right): clearly explosive, but small. The use of “gentle” and “effusive” would be jettisoned from the VEI — after all, it is an explosivity index — and instead those small strombolian and Hawaiian eruptions that would be lumped into VEI 0 could be discussed with more clarity, which is important for developing volcanic hazard assessments for highly trafficked volcanic vistas like Kilauea or Tongariro. The next challenge would be figuring out how to compare the effusive (lava flow) eruptions with the explosive eruptions, which is more of an apples and oranges issue. However, by adding negative VEI values, we can give those small explosions a little more of their due.
* Sidenote: If you do a rough estimate of the total volume over the last 10,000 years of all the VEI 0-1 eruptions (assuming 10,000 m3 per eruption, which is likely a very loose estimate), the total volume still only adds up to roughly a VEI 2-3 eruption (something like Redoubt’s 2009 eruption).
The forested dacite domes of Cerro Machín, nested within an older caldera. Pyroclastic flow deposits from Machín have been traced upwards of 40 kilometers from their source at the volcano. Image: INGEOMINAS, taken November 16, 2011.
I like to keep close tabs on the volcanoes in Colombia — with half of my family living in the country, it seems only appropriate. Some of my first volcanic memories are of seeing firsthand some of the lahar deposits at Nevado del Ruiz from the 1985 eruption. Now, at that time, only two Colombian volcanoes really made any noise: Galeras in the south near Pasto and the aforementioned Ruiz in central Colombia. Nowadays, thanks to increased monitoring on Colombian volcanoes by INGEOMINAS, we know a lot more about the restless nature of the volcanoes of the South American country. Five volcanoes are now on elevated alert status, meaning that they show some level of activity that could lead to an eruption: Ruiz, Galeras, Cumbal, Sotará, Huila and Machín.
Over the past week, Cerro Machín, a dacite dome complex to the to the south Ruiz near Ibagué, has been feeling some increased seismicity. The INGEOMINAS special bulletin details a M2.9 earthquake that occurred at a depth of ~4.7 km beneath the volcano that was felt by local residents. This was part of a swarm that produced over 210 earthquakes in a few hours on February 10 — all within 2 and 5 km depth, but all very small. Now, before you need to get too nervous about this activity, INGEOMINAS rightly points out that these swarms have occurred before at Machin and that sensitive new seismometers are likely to notice this type of activity that might not have been noticed in the past. Not a lot to see, but in the small chance that Machín does get more active, the Observatorio Manizales has a webcam pointed at the volcano. Machín’s last known eruption was over 800 years ago.
Right now, the most active volcano in Colombia is still Nevado del Ruiz. The volcano is still experiencing elevated seismicity, along with a ~950 meter steam plume that occasionally has minor ash as well — which can be seen via webcam, weather permitting.
The submarine eruption at El Hierro continued into 2011. Image: INVOLCAN
2012, for all the hype about apocalypse, was a volcanically-quiet year. No Eyjafjallajökulls, no Puyehue-Cordon Caulles, no Pinatubos. Sure, we had some notable eruptions, but most were small-to-moderate events that, many times, won’t even end up getting preserved in the geologic record. However, that didn’t stop me from posting way too much! No, really, it was still a great year for Eruptions, with decidedly more posts about the science of volcanoes when the actual volcanic events were low. Here is the 2012 Volcanic Year in Review!
I also tackled a topic that came up repeatedly during the year – the missing eruptions in the ice cap record. Namely, the ice cores suggest a large eruption in 1258 AD, but no source has been definitively identified (although inroads have been made). Another mysterious caldera eruption, the Kuwae caldera eruption in the 1450s, was also examined about whether it actually occurred.
Both Popocatépetl and Nevado del Ruiz kept on producing small eruptions as we headed into June, while Cleveland in Alaska had a explosive eruption, likely due to collapse of the dome that had been growing in the crater since earlier in the spring. We also saw the alert status raised at El Hierro in the Canary Islands for the first time in months after an intense seismic swarm occurred — but this swarm didn’t lead to any new eruption.
With all the excitement of the US Presidential election in early November, I looked at the perception of probability versus prognostication when it comes to volcanic mitigation. If you’re looking for a volcano movie to watch, I finally wrote up my guide to volcanic cinema and I described what a SHRIMP-RG is and how I use it in my research.
So, there you have it. The Volcanic Year in Review … and hopefully 2013 will bring us more volcanic excitement.
Erik Klemetti is an assistant professor of Geosciences at Denison University. His passion in geology is volcanoes, and he has studied them all over the world. You can follow Erik on Twitter, where you’ll get volcano news and the occasional baseball comment.
The plume from Tungurahua in Ecuador as seen on August 19, 2012. Webcam capture by Eruptions reader Kirby.
It is that time of year again – the summer is ending and classes begin within a week. Now, I am on leave for the fall, but that doesn’t mean the pace of things isn’t picking up. I spent the end of last week blasting zircons with a laser up at Michigan State in order to get some ages on those crystals and in about 2 weeks from now, I’ll be headed back to California for a week of field excursions across the Sierras. So, busy indeed.
Things have also settled down a smidge volcanically as well. After the New Zealand trifecta, we’ve had some rumblings around the globe … so I thought I’d just use today’s post to catch up with some news I’ve seen (or posted links to on Twitter).
It took a little bit to decipher, but it appears that the Grozny Group in the Kuril Islands may have had its first eruption since 1989. A couple of reports out of Russia suggest that the Ivan Gronzy (Ivan the Terrible; see above) dome in this cluster of lava domes within a caldera may have had a small eruption that spread ash across Iturup Island. One article says that the plume may have only been ~1 km, but it was enough to for people to note ash fall in Goryachiye Klyuchi (9 km) and Kurilsk (25 km).
Beyond this, the news is, well, hard to understand. The article in the Moscow Times claims that the eruption was caused by “increased water flows rushing into the volcano after heavy downpours” and that people noticed “hydrogen peroxide fumes“. Now, I’m hoping a lot of this is merely lost in translation as the ITAS TASS article talks about there no longer being a hydrogen sulfide odor in the area.
In any case, if this eruption is confirmed, it is the first at the Grozny Group since 1989. The complex of volcanoes is a very hydrothermally active area, with strong fumaroles, mostly at Machekh Crater. However, all the historic eruptions from the Grozny Group, including the one in 1989, have come from Ivan Gronzy, as this new eruption seems to be as well.
Aerial view by the New Zealand Navy of a pumice raft spotted near Raoul Island in the Kermadec Islands on August 10, 2012. Image from the New Zealand Herald.
Just think, one week ago I was saying that 2012 was a relatively quiet year for volcanic eruptions. We haven’t made up all the ground of the more active years like 2010-11, however New Zealand had one of its more exciting volcanic weeks in a century – White Island and Tongariro both had eruptions and yesterday a large pumice raft was spotted north of the island nation. This pumice raft (see above) is the product of a submarine volcanic eruption from one of the multiple of seamounts that are part of Kermadec arc north of New Zealand. Exactly which volcano is the source of the pumice is unclear – early on, it was suggested that Monowai was the source, but that seems to be in some question based on the location of the 26,000 square kilometer pumice raft (see below). The raft is located to the northeast of Raoul Island, one of the active volcanoes of the Kermadec Islands that is above the sea surface. The next known active volcano to the northeast of Raoul is Monowai, thus the suspicion that it may be the source. Likely the only way this actual source will be identified is through matching the composition of this pumice with that of known material from Monowai (or another Kermadec volcano). Rafts like this can travel great distances – some of the pumice rafts from the Krakatau eruption in 1886 washed up on African beaches months later – so trying to determine the exact source of the pumice when it is so widespread is challenging. However, this is likely a significant eruption based on the size of the pumice raft across the ocean surface. Monowai does seem reasonable, though, as it has produced significant eruptions in the last few years.
A raw Aqua/MODIS image of the pumice raft off Raoul Island in the Kermadecs, seen on August 10, 2012. Image courtesy of NASA.
Much like I said yesterday, none of these eruptions are directly connected – Tongariro, White Island and this submarine eruption in the Kermadecs are too far apart to be sharing any magmatism. However, the tectonics that control the formation of volcanoes are all the same – the subduction of the Pacific Plate under the Australian Plate.
