New eruption at Sinabung in Indonesia

Sinabung on Sumatra erupting on August 29, 2010.

Eruptions readers were quick on the news about the new eruption at Sinabung in Indonesia. There isn't much known about the eruptive history of the volcano - checking out the Global Volcanism Program, the last activity at Sinabung might have been an explosive event in 1881 with persistent fumaroles up until 1912. However, most news sources are quoting 400 years as the last known eruption of the volcano, apparently information from the Indonesian government.

The eruption itself appears to be an ash-rich explosion with ash fall reported up to 30 km from the volcano although the ash column from the explosion was only 1.5 km (~5,000 feet) tall. The volcano had been showing signs of activity with smaller explosions and minor steam-and-ash plumes on Friday, but the explosion on Saturday was much larger than expected. From the details I've read, [speculation] I wouldn't be surprised if there is no new magma (juvenile material) in this eruption, but rather just older material that was in the conduit. My hunch is that this explosion might be the start of more and the heat from the magma interacted with groundwater near the summit to cause the explosion - a very common precursor activity at a composite cone like Sinabung (think about the events leading to the eruption at Redoubt).[speculation] However, Surono, head of the Indonesian Center for Volcanology and Geological Disaster Mitigation, warned that "we have little knowledge in terms on its eruptive patterns and general forms."

A closer look at the August 29, 2010 eruption of Sinabung. Image by Binsar Bakkara/AP.

Thousands of people have needed to evacuate their homes around the volcano on Sumatra after this explosion - however, some have stayed behind to prevent the looting of their property. A 6-km exclusion zone has been set up around the volcano by the Center for Volcanology and Geological Disaster Mitigation as well.

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This could be a very nasty surprise. Like Krakatau or worse.
Composite Volcanoes are not to be complacent about (ask us
in the Pac NW. of the US..)

By Douglas Dc (not verified) on 29 Aug 2010 #permalink

I think this image from yesterday taken by Terra/MODIS may show the eruption. (Warning: large image.) There's some high level gray clouds that may be ash, and a small grey mark underneath in the vicinity of Sinabung. The volcano is just slightly to the northwest of the Toba caldera.

(My posts seem to be getting caught in the spam filter. Hopefully this one will go through.)

@PeakVT Your posts might get trapped because you use the 'named' link feature.

Here is your Terra/MODIS image juxtaposed with the Google Earth location image. "A" marks Sinabung

Thanks for the warning and the image. It looks to me like the small grey puff definitely is Sinabung. There's not much of a plume compared to Eyjafjallajökull. Hopefully it will stay that way.

It looks like that the volcano is doing cleaning house, or a small pre-eruption phase to a larger eruption. So there might be more to come. But due to lack of data it is hard for me to know when that might happen, so I am not going to speculate on that.

Only time is going to tell us what happens. But given the fact that his is around the area where several Mw7.0+ earthquakes have happened, I am surprised that this didn't happen sooner that a volcano started erupting in this area.

Hi everyone!
That panoramio pic is quite interesting. Does anyone know the story behind all those words made with rocks?

By Princess Frito (not verified) on 29 Aug 2010 #permalink

Here's another shot. Messages to the Gods?

By Princess Frito (not verified) on 29 Aug 2010 #permalink

this erupting vulcano lies only 30 km or so from the supervulcano Toba... i wonder why nobody worries about that...

wikipedia says:

Lake Toba is the site of a supervolcanic eruption that occurred 69,000-77,000 years ago, a massive climate-changing event. The eruption is believed to have had a VEI intensity of 8. It is believed to be the largest explosive eruption anywhere on Earth in the last 25 million years. According to the Toba catastrophe theory to which many anthropologists and archeologists subscribe, it had global consequences, killing most humans then alive and creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today.

By peter van rooij (not verified) on 29 Aug 2010 #permalink

#5 #7 I don't like this... After 400 years of dormancy, how many volcanoes are known to wake up "peacefully"? Any records of other such examples? According to Google Earth and SIV, there is a neighbor volcano (15 km to the NE), Sibayak, that emitted an ashcloud in 1881.
And actually, this is not only an area of 7+ quakes. There were too megathrust EQs in the last 6 ys or so, with epicenters less than 300 km apart, revealing a complex net of faults in the area. Besides, it is less than 35 km away of the deadliest caldera in historical time, Toba, a lake stretching 90 km across. Too bad we lack of data on this because I think there is some reason to get worried.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

#11 I meant "two" megathrust EQs. (9.0 - 2004; 8.6, 2005)

By Renato Rio (not verified) on 29 Aug 2010 #permalink

@ Princess Frito (#8): I've seen it in other craters as well, one of them being Puy de Pariou in France:…

I guess it's kind of the same as those little rock piles that can be found on a lot of mountains.

Anyway, it's way too early to even think about words like 'Krakatau'. I was even somewhat surprised that the eruption made the headlines of Dutch national radio this morning.

@ Jón FrÃmann: after December 26, 2004 an increase in eruptions in northwestern Sumatra wouldn't have surprised me. But then again, so relatively little is known about the effects of major tectonic earthquakes on volcanic systems. Btw, haven't you thought of maybe putting some helicorders in the Eifel ;-) ? I guess the area could use some ^_^ .

#10 #13 #11
@Gijs de Reijke: Even if there aren't such effects (EQs triggering eruptions), we are dealing here with an intricate faulting system relatively close to a triple junction. If you look at the image posted by Princess Frito you can see two of the various dormant volcanoes in the area (my guess).
And here is another dormant volcanic complex 110 km to the NW of Sinabung according to Wikipedia:
"Mount Kembar is a Pleistocene volcano, located in the northern Sumatra island, Indonesia. It contains a fumarole field, named Gayolesten. The volcanic complex is located in the junction of two geological fault systems and it is a shield volcano."
I'm no expert, like Jón, and I think he's absolutely right in his concern.
There's no reason to take for granted that the whole region is out of risk and maybe this small eruption is an alert to Indonesian authorities to be more careful with this particular zone.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Im not a scientist...but this happening now...I dont like...Is it some links, data to observe this vulcano?
pardon for my english...and thanks guys in this forum helping to educate/inform us!

By Lena Andersson (not verified) on 29 Aug 2010 #permalink

Thanks Gijs. I've never seen that type of environmentally-friendly graffiti before so I did a double-take. Sadly, in a few other shots of Sinabung, there are rocks with spray paint on them. :(

By Princess Frito (not verified) on 29 Aug 2010 #permalink

In the list of Sumatra volcanoes at Wikipedia Mt. Kembar is the only shield type volcano (Lake Toba labeled as a tectonic-volcanic type and Sinabung, a stratovolcano).
My questions here are:
1. How many instances of shield volcanoes, which are generally associated with rifting and hotspots, do we have at subduction zones (really don't know the answer).
2. Could we even think of another type of deeper source of rising magma related to this area between Toba and Kembar?
This is mere speculation of an amateur. @Passerby?

By Renato Rio (not verified) on 29 Aug 2010 #permalink

@ Renato Rio (#14): Yeah, I agree that it is a very interesting setting. That's why an eruption any time between now and 2004 wouldn't have surprised me at all. But like I said, the area's complexity probably makes it all the more difficult to understand what's going on there.

@ Peter van Rooij (#10): huge systems like Toba usually require more time (hundreds of thousand of years, if not more) to produce enough eruptable magma for an eruption the size of what produced the 'Young Toba Tuff' around 74.000 years ago. I don't think a big earthquake by itself 'shakes the bottle' enough to produce an enormous eruption at Toba at this point in time.

Looking for entryway to Indonesia Geological Directorate, Center for Volcanology and Geological Hazard Mitigation, Bandung, Indonesia.

None of my old links work, which is a shame because they had a crackerjack website with daily updates on 60 major volcanoes that span the Center's monitoring program; Indonesian government has undergone a de-centralization process. The old eruption volcanic monitoring site is gone. The public portal to the geological directorate isn't helpful - zero direct links. WOVO links are old.

@Passerby: Only director portal works for me. Of course, in Indonesian. For some reason Google translator works better in Portuguese(!!!??) Because of East Timor?

By Renato Rio (not verified) on 29 Aug 2010 #permalink

@ Renato

There are a lot of known shield volcanoes in subduction zones, for instance the Masaya volcano in Nicaragua (that is close to the Apoyo crater lake which could be a resemblance)and several shield volcanoes in the Kamtschatka Peninsula. I'm also doubting wether the Simbalung is connected to Lake Toba. Such as the proclaimed connection between Eyjafjallajokull and Katla. It is interesting to think about however without any proof.

Off Topic...
i continue to watch the earthquakes in Iceland
and was wondering if anyone else thought
Upptyppingar might erupt?
Anyone who knows more than i got an oppinion?
And that would be everyone ;)

Thanks in advance.

#22 @Maik:
Thank you very much for the information. I was just doing my research and found many "andesitic shield volcanoes" in USA (Alaska, Cascades) and elsewhere . Kempar, Indonesia, happens to be of this type. (…)
As for the Toba connection, it was pure speculation on my part. I try to be careful about such things as to look for imminent catastrophes, but since we had been discussing earlier about other possible mechanisms involved in intraplate volcanism (which is not the case here), such as crustal thinning due to underlying faults, I thought that, like it has been supposed for Krakatoa (Wikipedia), a thinner underlying crust could also explain the explosive origin of Toba's caldera, and that such thin crust could also be present under the segment of Sumatra Fault from Toba to Kempar, since a similar faulting pattern is present there.
As for Katla and Eyjaf's connection, for what I've been reading, I'm still not 100% convinced there are no connections, but I'm getting there too.
#23 @Motsfo: According to more knowledgeable people at this blog, those quakes are purely tectonic (see earlier threads).

By Renato Rio (not verified) on 29 Aug 2010 #permalink

@Passerby @Maik:
The more I dig in my quest for understanding the more puzzled I get. I thought the question about the existence of shield volcanoes at subduction zones was solved. But I went on, and here I am again, sharing my doubts with you guys. Feel free to ignore it, but I thought that maybe they could heat up the debates over this thread. (OK. After this post I must say good night and go back to my errands).
Shield volcanoes = volcanic edifice formed either by more fluid, mafic magma, poor in SiO2, or pyroclastic surges (???!!!! - which means "very explosive eruption"), providing a wide angle of magma deposit.
Andesitic magma = felsic, high SiO2 content.
Then I stumbled on this article ( - abstract, calling for "A dearth of intermediate melts at subduction zone volcanoes and the petrogenesis of arc andesites"
My question: how come there be "andesitic shield volcanoes" other than formed by SiO2 rich pyroclastic flows of explosive etiology? We are supposed to find conical-shaped "andesitic stratovolcanoes", because of their highly viscous lavas, but not "shield-shaped".
So, I'm kind of back to where I started:
Could Kembar be one of this type of "explosive" andesitic shield volcano, relating it to Toba's explosive genesis?
Thanks for reading this.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

RR pointed out: According to Google Earth and SIV, there is a neighbor volcano (15 km to the NE), Sibayak, that emitted an ashcloud in 1881.

If you look at the near neighbor, you're struck by the visual similarity of these two stratovolcanoes.

I think Erik is correct. A push of magma up under the volcano has caused ejection of old material and brought Sinabung to the same state of simmer as it's neighbor.

I would, therefore, look also at Mount Sibayak for clues of increased activity.

Geothermal Setting:
'Thermal manifestations Hot springs and steaming grounds are distributed in the southwestern part of the Singkut caldera. High-temperature fumaroles and solfataras exist on the top and also on the southeastern part of Mt. Sibayak. Temperatures of hot spring water range from 30 to 63°C.

'Hot springs are also situated outside the caldera; at Sinabung area about 14 km southwest of Mt. Sibayak, and Negeri Suoh area about 7 km southeast of Mt. Sibayak.

Discharge waters at Sinabung are of low to moderate
temperature and of bicarbonate-sulphate type. Discharge waters at Negeri Suoh have temperatures in the range 40-60°C.

Geological setting (excerpt):
There has been a complex volcanic history in the area with a number of eruption centres developing over a considerable period of time within the Quaternary.

The geological structures in the Sibayak area are mainly controlled by volcanic and tectonic processes. The caldera structure, elongated NW-SE, developed after the Mt. Singkut volcanic eruption. Some fault structures within the caldera are oriented NW-SE, and are parallel to the Great Sumatra fault...

Source: Optimization of power production, SIBAYAK GEOTHERMAL FIELD. (Geothermal Training Programme, Report 16 (2004) ReykjavÃk, Iceland.

Righto. We have a roughly triangular area rich in hot springs that parallels the Great Sumatra Fault.

'The Indonesian island of Sumatra is located in a highly seismic area of the world. In addition to the subduction zone and the associated Sunda Arc off the west coast of the island, Sumatra also has a large strike-slip fault, the so-called Great Sumatran Fault, running the entire length of the island.

This fault zone accommodates most of the strike-slip motion associated with the oblique convergence between the Indo-Australian and Eurasian plates. The fault ends in the north just below the city of Banda Aceh, which was devastated in the 2004 Indian Ocean earthquake.

>>>>After the December 2004 earthquake, pressure on the Great Sumatran Fault has increased tremendously, especially in the north.

We have the northern end of this island dominated by a constrained and very large and powerful fault, that has increased in activity *markedly* since 2004. The volcanoes of interest lie parallel to this Great Fault.

Now we have a jump in magmetic intrusion below a very quiet volcano considered 'safe' until a few days ago, having a more active neighbor with 2 active vents. We have geothermal field that supported the first power plant in Indonesia, one that is slated for expansion shortly.

I wouldn't be worried about an eruption. I would be very, very worried about another massive earthquake in the area.

Somebody tap on PVMBG's horn and get their attention. They have dozens of able geologists who should be looking for signs of rapidly increasing groundwater pressure, pronto!

Couldn't resist a quick lurking and... bingo!
Hope the guys at PVMBG show your lucidity, Passerby.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Sorry about the lack of posts....well the volcano bussiness is off season
I've been not only frantically prepping for class and my Eyja talk....any news from Pall Einerson?
or from the volcano front
i dont see nothing coming from icelandic univ's
at least some sismic data

Looks like another eruption, this time to at least 20,000 feet.

DTG: 20100830/0038Z
VAAC: Darwin

VOLCANO: Sinabung 0601-08
PSN: N0310 E09823
AREA: Sumatra


OBS VA DTG: 30/0030Z
SFC/FL200 N0315 E09830 - N0305 E09720 - N0205 E09810 -
N0315 E09830 MOV SW 10KT

FCST VA CLD +6HR: 30/0630Z
SFC/FL200 N0315 E09830 - N0255 E09655 - N0130 E09725 - N0315 E09830
FCST VA CLD +12HR: 30/1230Z
SFC/FL200 N0315 E09830 - N0240 E09550 - N0100 E09645 - N0315 E09830
FCST VA CLD +18HR: 30/1830Z
SFC/FL200 N0315 E09830 - N0205 E09500 - S0020 E09625 - N0315 E09830

[lower case]

By Chance Metz (not verified) on 29 Aug 2010 #permalink

Really nice little reference maps of the tectonic setting of Sumatra, the Great Fault and volcanoes of North Sumatra.

Pay particular attention to the Interceptor FZ, the Central Domain, and the velocity vectors in the top map, before opening the large lower map and locating our two volcanoes of interest.

@motsfo, The Upptyppingar case is interesting and that would be a understatement. According to my ideas, and the ideas that I base that on. The Upptyppingar appears to be a volcano in formation. It has not erupted yet as a volcano with a magma chamber. But it is going to do so at one time in history. When that might happen I do not know.

If we are extremely lucky we might get one off cone volcanoes there in less then 5 to 10 years. But I am expecting big eruption in 30 to 50 years, based on current models and given the number of earthquakes. But only time is going to tell me what is going to happen, and how this is going to evolve at Upptyppingar.

According to an article in the German news magazine 'Der Spiegel' locals reported seeing lava flowing from the Sinabung volcano:,1518,714420,00.html

The google translation reads as follows:

"Local media reported, citing witnesses, leaking lava was seen from miles - even in the tourist area of Berastagi to the north of the island. Volcanic ash from the 2451 meter high volcano had reached the provincial capital Medan.

"At midnight there was a severe blow - one suspects a volcanic earthquake," said Irsal. "Soon after we saw lava running down from the top of Sinabung and fire burned the forest at the foot of the mountain."

Here the original:

"Lokale Medien berichteten unter Berufung auf Augenzeugen, auslaufende Lava sei aus mehreren Kilometern Entfernung zu sehen gewesen - auch in der Urlaubsregion Berastagi im Norden der Insel. Vulkanasche aus dem 2451 Meter hohen Feuerberg habe die Provinzhauptstadt Medan erreicht.

"Um Mitternacht gab es einen starken Schlag - man vermutet ein vulkanisches Erdbeben", sagte Irsal. "Kurz darauf sahen wir Lava vom Gipfel des Sinabung herunterlaufen und Feuer verbrannte den Wald am FuÃe des Berges.""

But I don't know, if those observations were confirmed from independent / qualified sources.

By Holger, N California (not verified) on 29 Aug 2010 #permalink

Not much to look at... I can't find any listings with lower magnitude quakes, so your not gonna get much more than an overview. That is one of the beauties of Iceland and Italy, nice quake lists.

Mag 4.0+ 1973 - 2010, Sinabung location +200km circle. Perspective view. USGS data source. (easier to pull and has depth info, unlike the site in country)

So, I come back and what we have here? - an eruption with a significant ash plume, wood fires from lava emission, a huge earthquake in perspective and a magnificent plot showing the subducting slab under Eurasian plate!
You guys want me to get "fired" too?

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Yep the volcanes are acting up again. This one may be big so I will be sure to keep track of it for the coming weeks.

By Chance Metz (not verified) on 29 Aug 2010 #permalink

I'm just passing by and looking for some information related with the recent eruption of sinabung this morning at 6 AM (Local time). I'm indonesian and know too little about volcanism, could u all give a opinions of worst case scenario that might happen here with this mountain?

Could you show us a N-S and a E-W view? Or maybe just a flat view to get a perspective of the Sumatra Fault.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Good morning. Hope you're doing well. From what part of Indonesia are you typing? So far, we are having some news of an ashcloud (post #30) and rumors of some lava pouring out from the summit (#33). Maybe you are more up to date with local information.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Try the Figures

to this paper: Nature 440, 46-51 (2 March 2006)

Plate-boundary deformation associated with the great SumatraâAndaman earthquake.

The last figure will help you put Lurkings timely plot into perspective. The first figure is a neat graphic, showing the fault segments and the last dates of rupture.

Although you might not be able to read the paper, in this case the accompanying figures speak for themselves.

On the reference maps of Sumatra tectonic settings, could you please explain what is the red dotted circle across Toba lake?

By Renato Rio (not verified) on 29 Aug 2010 #permalink

@Adibrata Could you translate the main story here for us? With more information, we might be able to help you. Thanks.

The Sama dengan kejadian hari sabtu story? Also, is the Dua Ruko di Surabaya Hangu Terbakar story related to the eruption? If so, where are the office buildings that caught on fire? Thanks very much.

By parclair, NoCal (not verified) on 29 Aug 2010 #permalink

Thank you @Passerby. Now it is Good Night!

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Sibayak, Sinabung and Toba share a common feature. They straddle the Sumatra Fault.
Sinabung sits out on a lava plain by itself. Sibayak is a volcanic cone straddling the side of the Singkut Caldera.
There are domes every where around the surrounding area in between Toba and Berastagi. Sibayak and Sinabung are obviously active as they emit sulfurous fumes.

Local history states that both Sibayak and Sinabung showed some activity in 1881. This may be coincidence but I'm not sure of the two cones share exactly the same magma source.

There are around 500,000 people in the surrounding areas of the eruption area. 60kms to the Northeast sits Indonesia's third largest city - Medan. If a major eruption took place at Sinabung there would be a bit of a problem for all these people.

The fertile plains around this volcano are a major food producing area with a huge export business with Singapore and Malaysia.

By Les Francis (not verified) on 29 Aug 2010 #permalink

@Renato Rio: Well, I'm in Jakarta right now, but still, with a country like Indonesia, we don't expect another natural disaster happen in indonesia soil, because the impact will be huge..
@parclair, NoCal: I believe those two news is not connected, the two Ruko (office building) is located in Surabaya (East Java).

@42, RR Subducted fault zone, in line with the yellow arrow.


>Sibayak, Sinabung and Toba share a common feature. They straddle the Sumatra Fault.

They do not. They *may* straddle a transverse fault system not shown on the Cal-Tech map. The geothermal field-power station engineers will know.

News report on the 2nd eruption that occurred Monday, as reported by Chance, #30, ash to ~2 Km.

Re: Renato Rio[39]

Okay, but like I said, it's not much to look at. Remember, this is a plot of all quakes since '73 as they appear in the USGS catalog. It was used because the in-country catalog was less than helpful (no depth info). That doesn't mean that there isn't a better catalog that I just haven't found or have access to.

North view, looking through the the fault plane:

East view (looking east), not fully in line with the fault plane:

And a plan view:

The lack of sub mag 4.0 quakes pretty much rules out being able to plot magma paths, cracks and creaks.

There's a huge discrepancy surrounding the height of the 2nd eruption. Post #30 says 20,000 feet whereas post #49 says 2 kilometers.

Which is it?

By Princess Frito (not verified) on 29 Aug 2010 #permalink

Plan view: almost like a back arc volcanic group from subduction melt upwelling. Super interesting to see the fine structure from 3 directions and in 3-D.

Oh Goodie! Deep-focus EQs.

Excellent work; thanks again Lurking!

@Adibrata 53. Wow. That eruption looks serious. Thanks for the link.

By parclair, NoCal (not verified) on 29 Aug 2010 #permalink


I'd be interesting in knowing the time relationship of that image verses the the one linked in post 53.

The plume on the left is definitely being shot out almost horizontally, then turning upward from the heat.

If the vent was partially obstructed, did it clear, making the image from 53 possible? Or is this something that fell and obstructed the vent shown by 53, possibly causing the twin plumes?

Very nice photos there Adibrata, thanks for posting that link.

I'm due to get into Medan tomorrow afternoon, around 3pm local time. I'll be there for about 4 or 5 days and will endeavor to post photos and updates on the eruption here...

The situation at Sinabung reminds me of a number of very different volcanic events, some of which culminated with large, destructive eruptions, whereas others calmed down after some time without growing really big and dangerous.

So far the eruption appears to be phreatic, maybe the initial explosions unleashed hot material (you can see incandescence in video posted on YouTube: but certainly NO LAVA FLOW. Fluid, Hawaiian-style lava does not come out of this type of volcano, especially not at the start of a new eruption after long repose. Maybe there is a lava dome pushing from the summit, although I would expect this to happen later on, after the path for the rising magma has been cleared.

There are indeed spectacular photos at Daylife, which show that there are several vents at the summit and on the side of the volcano:

Three scenarios can be envisaged:

(1) Soufrière de la Guadeloupe (1976-1977) - phreatic explosions and probably magma uprise, without culminating in a magmatic eruption; similar events have occurred at Fourpeaked (Alaska) in 2006, Koaryaksky (Kamchatka) in 2008-2009 and numerous other volcanoes. One particular example is Ontake in Japan, which erupted in 1979 after possibly up to 30,000 years, but all that happened was a few phreatic bursts and then the volcano calmed down again.

(2) Unzen (1990-1995) - phreatic explosions followed by lava dome growth without much explosive activity. Much of the disaster caused by the Unzen eruption was due to collapse of the lava dome, which grew on a very steep, unstable flank and thus often crumbled, generating pyroclastic flows. A variation on the theme is Soufrière Hills (Montserrat) where initial phreatic explosions were also followed by dome growth and frequent dome collapse, but there was also strong explosive (Vulcanian to sub-Plinian) activity.

(3) Pinatubo (1991) - initial phreatic explosions followed by dome growth and then a massive cataclysmic, caldera-forming eruption, which in turn was followed by lava dome growth.

A Pinatubo-like scenario is possible but less likely than the other two scenarios. If Sinabung behaves like Unzen, i.e. if it builds a lava dome at its summit or on its steep upper flank, there is a high risk of pyroclastic flows generated by dome collapse. Seismic and deformation monitoring is imperative here, to see whether a large volume of magma is making its way to the surface, as at Pinatubo, or whether it is rather modest and will produce a lava dome-building eruption.

Out of topic but certainly of interest, a little Etna update:

Since the strong 25 August phreatomagmatic explosion at the Bocca Nuova at Etna's summit, there have been numerous smaller and 8 medium-intensity explosions, the latter of which generated conspicuous but short-lived ash emissions. Observations made at close range disclose that these events are virtually noiseless, and the ejected ash is altered, lithic (old, not new hot magmatic) material so far.

Access to the summit craters of Etna is now prohibited by decree of the Prefecture of Catania. The situation is considered highly dangerous; during a strong phreatic or phreatomagmatic explosion at the Bocca Nuova on 12 September 1979, nine tourists were killed and more than 20 injured.

It is likely that the current explosive sequence is a vent-clearing activity, as magma is reoccupying the conduits of the summit craters. Evidence for magma uprise is also in the fact that fumarole temperatures on the crater rims and on the outer southwest slope of the central summit cone (which hosts the Bocca Nuova and Voragine craters) are rising, leading to increased sulfur deposition (at temperatures above 120° C).

Updates are posted in Italian and English at the INGV web site -

@#60 - Heh. Literally at cockcrow.

By Kultsi, Askola, FI (not verified) on 29 Aug 2010 #permalink

There's an outstanding concentration of EQs under Toba (rather than at Sinabung) and since they aren't from the Great Sumatran fault, what are they? An unknown fault or Toba's own faulting system? - if I understood it right.
@Boris and all:
Thanks for the stunning pictures and posts. We we'll have a busy week from Indonesia and Italy. Keep safe you and Adibrata.

By Renato Rio (not verified) on 29 Aug 2010 #permalink

Don't like this. Hope it follows the more innocuous paths proposed by Boris. This could become a Plinian event hugely affecting nearby population (500 000). We need more tremor plots and GPS measurements. Where can you get them, Lurking?

By Renato Rio (not verified) on 29 Aug 2010 #permalink

A local newspaper (Google translated) is unsure of what to expect from this:
"Identification Difficult Vulkanolog Sinabung" (...)
"The team from Bandung Volcanology led Surono still can not decide what type Sinabung," says Head of Department of Energy and Mining, North Sumatra, Untungta Kaban." (...)
"Sinabung eruption in the middle of the night when it came to a radius of 10 kilometers. Even the dust up into the sky vulkaniknya Medan, a distance of approximately 150 kilometers from the eruption site."…

By Renato Rio (not verified) on 30 Aug 2010 #permalink

Sinabung does not look like your normal (strato)volcano with a regular summit crater. Judging by the photos, it has more of a "flank" crater running from summit to about 2/3 of the way down...

By Henrik, Swe (not verified) on 30 Aug 2010 #permalink

I would be very suspicious of any volcano that suddenly starts erupting after centuries of dormancy.

By mike lyvers (not verified) on 30 Aug 2010 #permalink

I would be very suspicious of any volcano that suddenly starts erupting after centuries of dormancy.

Posted by: mike lyvers | August 30, 2010 6:42 AM

Like Chaiten for example?


There was news-footage of lava earlier today at the same place where you can actually see it at #53 pictures. Nice to see that even experts can be surprised by volcanos now and then.
Thanks for the list of possible things that can happen at Sinabung.

By Carl on Lava (not verified) on 30 Aug 2010 #permalink


For those who cannot read swedish the article Henrik cited states that there are now 4 times as many dead from this eruption than the Eyja (8).

@Carl on Lava #69, I did in fact refer to the news footage where you see incandescent material - but that is not fluid lava. It is rather hot blocks falling from a lava dome, or vegetation set on fire by hot material. We should remember that also phreatic explosions can throw out rocks at temperatures of up to 800° C, which means they're incandescent, even though they are not derived from new magma!

Tragically (but not surprising), the news media are mixing up the Sinabung news with photos of all sorts of eruptions (including old Eyjafjallajökull).

I guess that some idiot then had clipped in some nice bubbly burping lava in the news here in Sweden. Unusual that they do things like that here.

@Renato Rio [62]

That has more to do with how the plate is being subducted and in what regions stress and fractures build up.

The Toba caldera forming event was an easy 75 kyr ago.

It's very unlikely that a bag-o-quakes at 150+ kilometers deep on the folding area* of a subducting plate in the 1973 to 2010 timeframe has anything more to do with it than it does any other volcano on the island.

Remember that the plots do not have any quakes under 4.0. Just the larger ones.

Likely, a large quantity of quakes are there but just not available for plotting. If the ratio is anything like Iceland, then that number is HUGE, and is probably why they don't report every creak and pop. They also might nor have the same gear coverage as Iceland.

* I'm going with the folding idea, I think Passerby and others of that camp are dead on accurate.

We know that a prominent fracture zone is being subducted in the area of Toba and Sinabung. I suppose there might be a chance that bending crust that is 'prefractured' in an opposite orientation to bending axis could provide a route for magma flow to the surface. Just enough to provide hydrothermal heat source and fumaroles, but not vigorous eruptions in the recent past.

So one could guess that a build up of stress on the Great Sumatran Fault, perhaps near the segments which haven't been active in several hundred years - note that the old rupture dates roughly correspond to the approximate period of last known large eruption for Sinabung) - are under considerable stress buildup from the 2004 Aceh quake.

This is why I fear that a major EQ is much more likely than any large eruption, and why I concur with Erik that we're seeing old material being expelled under a sharp rise in pressure under Sinabung and perhaps under adjacent volcanic centers, given the anecdotal evidence of paired minor ash eruptions in early 1880s (same period as Krakatoa to the south, and mid-island Dempo and Kaba eruptions - all part of the southern domain subduction region of the GSF).

This is the provenance of the Cal-Tech group who has been chugging away on the tectonics of North Sumatra for a decade. We'll give them a buzz and see what they make of our idea.

planet-wise , the dates to watch out for are :- 5th to 9th
September , there are 6 planets in a 30 deg corner of space
around the sun .

@All: if anyone needs a hand in translating indonesian article from a local news, just let me know, sometimes even google translate not with a right grammar.. :)

little update from several local news today, there's no high activity today at mount sinabung, some analyst said that because the pressure at the magma chamber under the volcano is decrease..

but the Presidential Special staff of the Disaster and Social Affairs said that it's not end yet, from the size of the volcano, a big eruption could happen and the effect will be catastrophic to third biggest city in indonesia, Medan and surrounding country like Malaysia and Singapore.

in the other hand, Head of Geological Agency Ministry of Energy and Mineral Resources,R Sukyar said this morning that a new crater creates after the second eruption and creation of a new crater on the top Sinabung can reduce the pressure of magma under the volcano.

What u guys think about this?

[quote] Hi everyone!
That panoramio pic is quite interesting. Does anyone know the story behind all those words made with rocks?

Posted by: Princess Frito [quote]

i just googling about Mt.Sinabung then arrive here ^_^ thanks God cause i get more information unheard before about this Mountain, anyway I'm living here in 'Kabanjahe' [the capital of Tanah Karo] near Mt.Sinabung just about 20km [the Mount looks quite clear from here]
about Princess Frito question i guess the Rocks written was names [perhaps the names of the people who ever came there]
i also hope like Adibrata, maybe u guys who knows about geologic could share information for us, especially for us the people around this we know what we have to face here... Thanks a lot ^_^ [i'm sorry if my english bad ^_^]
next time i'll share more pics i get during the eruption...

By Mayhend's (not verified) on 05 Nov 2010 #permalink