Disqus - Friends of tietoukka

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Wed, 28 Sep 2011 12:35:55 -0000

Just a short note on Etna - the New Southeast Crater is starting a new
paroxysmal eruptive episode, the 15th since January 2011, as of the late
afternoon of 28 September. This event comes after a quiescent interval
of 9.5 days, and thus the tendency of progressively lengthening
intervals between paroxysms has been broken. Currently weather clouds
are hampering visibility but it is hoped that with dusk the clouds will
go away and the Greatest Show On Earth will be visible in full splendor
:-D
The event comes one day after a peak in sulfur dioxide emission,
which has often been observed before recent paroxysmal episodes at Etna,
but not always as pronounced as this time.

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Wed, 28 Sep 2011 12:43:47 -0000

Your're right --- Diane has done the good guess this time. I have, however, always said that "if Etna was to maintain the tendency of the past two months, of intervals between paroxysms lengthening by one day each time" the next one would have to be expected by 1 October. This tendency has obviously been broken, also this, I have often remarked, would sooner or later happen. Unfortunately, you can't really predict or forecast such events on tendencies alone - only once we get the typical premonitory signs such an increase in volcanic tremor amplitude, audible or visible explosive activity, a shift of the volcanic tremor source from its usual position below the center of Etna's summit toward the New Southeast Crater and so on. We had none of these until about three hours ago ...

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Wed, 28 Sep 2011 12:52:49 -0000

hahahaha, no it's the same New Southeast Crater as during all previous episodes, but we have an unusual wind direction (toward southeast), so that the plume seems to be coming from a position more to the left than usual

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Wed, 28 Sep 2011 13:17:53 -0000

Tremor is not getting lower, it's just automatically corrected after a while ... Renato I am sure you have seen this happen already a number of times before :-D
In any case, the tendency is UP - but there are still clouds interfering with the view.

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Wed, 28 Sep 2011 18:28:12 -0000

WOW. That was one brief but extremely powerful paroxysm of Etna's New Southeast Crater. Fountains were taller than during the previous episodes, though maybe not as tall as during some of the paroxysms in the year 2000. It was also spectacularly loud, especially during the first few minutes of high lava fountaining. We were having dinner at home with guests from Germany, who were totally blown away - sitting at the kitchen table, eating tasty cous-cous accompanied by an excellent red Etna wine and seeing that roaring volcano outside. One particular detail is that intense activity occurred also from fissures on the southeast and northeast flanks of the New Southeast Crater cone. It will be interesting to see how that thing looks in daylight ...

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Thu, 29 Sep 2011 01:45:15 -0000

hahahaha it was actually Etna's paroxysm that was late (the GVP weekly was on time) :-D
On the morning after, all is perfectly quiet at Etna.
Well, and there is this little video that a friend of mine shot - the sometimes slow, sometimes fast motion might not be everybody's taste (it's the artistic freedom of the author), but it's got some details that are beyond description, check out the explosion at time 02:07-02:08 causing a pressure wave which displaces the weather clouds around the crater ...
http://www.youtube.com/watc...

Re: Increasing Indications of a Potential Eruption at El Hierro?

Boris Behncke — Thu, 29 Sep 2011 15:00:23 -0000

aw this is sweet :-D

Re: Etna’s Latest Fireworks Show

Boris Behncke — Fri, 30 Sep 2011 15:14:35 -0000

Indeed there is currently no sign of an imminent large eruption; the swelling of Etna is rather slow (after a phase of accelerated swelling between May and July, which was followed by an intensification of the summit activity), there is none of the seismic activity that we usually see for months before a major eruption (like 2001 or 2008), and so it is rather likely that the activity will for some time go on more or less like in the first 9 months of this year. It is amazing that the media ignore the press statement released by our institute a few weeks ago, where it was explicitly stated that currently there is no indicator of a large eruption. Etna can go on making intense summit activity even for more than 10 years without any "big" (which means, flank) eruption, like in 1955-1971. Indeed between 1995 and 2001, Etna made about 150 paroxysmal episodes (compared to 15 in 2011 so far), but it took 6 years until the flank eruption of 2001. The number and intensity of summit eruptions does not say anything about an imminent flank eruption - it only says that the volcano is receiving magma input from the upper mantle, and that is pretty much the normal state of Etna :-D

Surely enough, one day we will start to see the signs of a nearing flank eruption, maybe in a few months, maybe in a few years. Just for the moment, it is not happening.

As for the break (3 minutes) in the activity before the latest paroxysm really let loose, it's not easy to explain, but it is possible that the upper level of magma in the conduit somehow rapidly lost its gas content and therefore stopped exploding, and then more gas-rich magma rapidly rose to the surface and instantly decompressed, causing violent degassing and the onset of intense explosive activity. It may also be that some magma found its way into the fissures extending southeastward and northward through the flanks of the new cone, which may have caused some withdrawal of magma in the conduit for a brief interval. In any case, there have been many cases in the past 20+ years, where the buildup to a paroxysm was not a linear increase, but rather a repeated waxing and waning, before things got really crazy. I particularly remember 16 April 2000, when for many hours it repatedly looked like the (old) Southeast Crater would finally go bang and then the activity subsided, then resumed, increased, subsided once more, and then increased again ...

Re: Peddling Fear of an Icelandic Volcanic Eruption

Boris Behncke — Fri, 13 Apr 2012 07:10:49 -0000

Those are good questions Bruce, and not all that easy to respond to ... we're still trying to figure out what these flows are exactly - they behave like pyroclastic flows, they look very much like pyroclastic flows, but those that we've again seen yesterday, and also on 4 and 18 March and on a number of earlier occasions both during paroxysms of the new and of the old Southeast Craters, are something different. Their mechanism of formation is not pyroclastic (i.e. formation by magmatic fragmentation processes) but it's phreatomagmatic, mostly due to explosive interaction of lava flows with water - wet ground, or melting snow and ice. Supposedly they are also colder than typical pyroclastic flows, more vapor-rich, and it seems that their basal portion rather resembles lahars - yet, unlike lahars, they generate conspicuous gas and ash clouds, and so they are something new, which yet have to receive their proper name in the volcanological terminology. After all, though, they do represent one end member in the broad spectrum of what is generically called "pyroclastic density currents" (PDCs), because if base surges are included, their fragmentation mechanism is also phreatomagmatic, and maybe these lava-snow-interaction-related PDCs we're now seeing at Etna during nearly all paroxysms in the winter (I guess we will not see them in summer when all the snow will be gone) are most similar to base surges.

I guess what keeps these specific flows buoyant is the continued mixing of lava and snow/meltwater during their advance; some video footage obtained of these recent flows show how explosions occur repeatedly within them while they descend. However, an important detail is that they seem to form mainly where the mixing of lava and snow/meltwater is turbulent, and this happens where the lava is flowing fast on steep slopes. You don't seem to get this sort of phenomenon where lava moves slowly on a rather gentle slope, no matter how thick the snow is. There you get only small explosions, which tear some blocks from the lava and throw them to a few tens of meters away, but none of the rather "Surtseyan"-looking explosions that occur when there is turbulent mixing, and where you also get those peculiar pyroclastic-flow-like phenomena.

So the phenomenon has always been the same, in the paroxysms of 29 March 2007 (one of the last at the "old" Southeast Crater), on 10 May 2008, on 10 April 2011, on 4 and 18 March 2012, possibly also on 1 April (less visible at night, but someone filmed a black cloud moving down the slope to some distance in that event), and again on 12 April 2012.

This is work in progress, and we would really need to get to study and sample the ddeposits created by these flows, problem is that they nearly always form in areas that are extremely difficult to access. But as long as these paroxysms go on and there is enough snow on the volcano, we will probably see these phenomena over and over again, and eventually - hopefully - get to see their deposits close-up, shortly after emplacement. The only deposit of this type that I was able to see and sample was that of 4 March, but only 12 days after emplacement, with a lot of wind and precipitation in between.

Re: Ash Falls on Manizales as Colombia’s Ruiz Ramps Up Explosions [UPDATED]

Boris Behncke — Thu, 31 May 2012 09:01:06 -0000

Hello Randall, good to see you again here! Love your last sentence, hahahaha ... best from the island of Martinique, where some small-scale sort of doomsday happened 110 years ago, when Montagne Pelée erupted and exterminated the town of Saint-Pierre with about 28,000 inhabitants - go figure if something similar happened today

Re: Ash Falls on Manizales as Colombia’s Ruiz Ramps Up Explosions [UPDATED]

Boris Behncke — Thu, 31 May 2012 11:13:44 -0000

Well --- currently I am enjoying my belated honeymoon with Catherine and our little Ida on the lovely volcanic island of Martinique in the Caribbean. Right, that's the one with the notorious Montagne Pelée volcano, which wasted the entire city of Saint-Pierre with approximately 28,000 people on 8 May1902, leaving only two people alive in the city. Known also as "Mount Pelée", the volcano is deeply asleep since its latest eruption in 1929-1932, and certainly no one would miss and misinterpret the signs of a new imminent eruption as soon as they are recorded by the dense network of monitoring instruments. There are currently no indications that Pelée will wake up in the foreseeable future, rather it seems it is determined to go on sleeping for a long, long time.

http://www.flickr.com/photo...

As for the New Southeast Crater of Etna, I think it will go on for a while, before there will be yet another new crater in the summit area. Certainly its position is a bit more precarious than that of the older Southeast Crater. However, for the moment it appears quite stable, and from all data that we have, a major eruption is not imminent. The most likely events in the near future are more episodes of lava fountaining from the new Southeast Crater, and possibly also activity at one or more of the other summit craters ... and then, sometime in the future, no one can say when, there will be an increase in the seismic activity and deformation and that will be the buildup to a new flank eruption.

Re: Volcanic Crystal Forensics: What Minerals Tell Us About the Evolution of Mount St. Helens and Long Valley

Boris Behncke — Thu, 31 May 2012 20:09:17 -0000

That is one really good article on what is really a dilemma ... I've said this a zillion times on this and other blogs, is earthquake prediction really something we want? Everybody here should read this.

Re: Eruption Update for June 4, 2012: Popocatépetl, Nevado del Ruiz, Kilauea and more

Boris Behncke — Tue, 05 Jun 2012 07:57:40 -0000

I've been having the same problem lately ... but maybe volcano images are considered "red light images" ???

Re: 2012 Volcanic Year in Review

Boris Behncke — Fri, 04 Jan 2013 10:33:49 -0000

Let's not forget the spectacular eruptions (lava fountains, lava-ice/snow interactions) of Llaima in 2008-2009. Chile in any case is packed with active volcanoes ...

Re: 2012 Volcanic Year in Review

Boris Behncke — Sat, 05 Jan 2013 02:33:41 -0000

Vesuvius is a volcano that erupts in cycles, that means, not the same way all the time. There are people who say that it makes a major eruption every so and so many years, but this is wrong. In reality, Vesuvius has periods when it goes on almost continuously, much like Etna, for many centuries (like 1631-1944), and then it stops and remains totally silent for rather long periods that can last centuries to millennia. At the end of a quiescent period, it goes off rather violently, like in the famous 79 AD "Pompei" eruption, which came after 800 years of quiescence, or the slightly less violent but still deadly and devastating 1631 eruption, which had been preceded by 500 years without activity. So what (and many colleagues) guess is that the current repose period, initiated in 1944, might last for another few hundred years. I do not count on seeing Vesuvius erupt during my lifetime. However, I am quite concerned about the other, much less famous volcano, on the other (western) side of Naples, Campi Flegrei, which since several decades is showing signs of unrest ...

Re: 2012 Volcanic Year in Review

Boris Behncke — Mon, 07 Jan 2013 02:00:20 -0000

It's a vent emitting very hot (500-800 degrees C) gas, capable of heating the walls of the vent to incandescence. That happens sometimes when magma gets a bit closer to the surface, but does not necessarily lead to an eruption. There was a similar thing at Vulcano, in the Aeolian Islands, in the late-1980s to early-1990s, where some of the gas vents were seen to glow at night, but the volcano has not erupted since. Note that the web cam is rather sensitive, capable of "seeing" things difficult to discern even with the naked eye (there are a couple of those surper-sensitive cams also on Etna).

Re: 2012 Volcanic Year in Review

Boris Behncke — Mon, 07 Jan 2013 08:35:08 -0000

Since this morning, there is a new lava flow issuing from the northern part of the summit crater platform of Stromboli - there have been similar lava flows during the period 23-28 December 2012.

Re: Rising Sea Levels Might Promote Increased Volcanism

Boris Behncke — Thu, 10 Jan 2013 01:28:44 -0000

At last, Etna has come back to life with renewed Strombolian activity at the Bocca Nuova - bright glows were well visible this morning from my home in Tremestieri Etneo.
www.flickr.com/photos/etnab...

Re: Rising Sea Levels Might Promote Increased Volcanism

Boris Behncke — Thu, 10 Jan 2013 01:34:28 -0000

Just posted a comment announcing the resumption of Strombolian activity at Etna's Bocca Nuova with a link, and the comment has disappeared in the vortices of "awaiting moderation" ... anyway, two of our Sicilian volcanoes are now in eruption: Stromboli is continuing to produce intermittent small lava overflows, and Etna is having its first significant eruptive activity since early October

Re: Rising Sea Levels Might Promote Increased Volcanism

Boris Behncke — Thu, 10 Jan 2013 03:46:56 -0000

Looks we posted our comments simultaneously :-D (see just below)

Re: Rising Sea Levels Might Promote Increased Volcanism

Boris Behncke — Thu, 10 Jan 2013 14:59:36 -0000

More detailed information on the latest activity at Etna and Stromboli:
http://www.ct.ingv.it/index...

Re: Rising Sea Levels Might Promote Increased Volcanism

Boris Behncke — Thu, 10 Jan 2013 15:21:18 -0000

Yes, we moved from Trecastagni to Tremestieri Etneo on 5 December - and this is the first activity of Etna we're seeing from the new home :-D

Re: Busy Week at Italy’s Stromboli with Lava Flows, Explosions

Boris Behncke — Tue, 15 Jan 2013 06:18:40 -0000

indeed the activity has likely come to a stop, though weather conditions have dramatically deteriorated and there is no visibility. The last glow was recorded by our surveillance cameras around 05 h local time this morning, about one hour before the volcano disappeared in the clouds of raging thunderstorms

Re: Busy Week at Italy’s Stromboli with Lava Flows, Explosions

Boris Behncke — Tue, 15 Jan 2013 13:15:33 -0000

Sorry it's only in Italian so far, tomorrow I'll post also the English version of the latest INGV-Osservatorio Etneo report on the activity of Etna and Stromboli during the past few days!

www.ct.ingv.it/index.php?op...

Re: Busy Week at Italy’s Stromboli with Lava Flows, Explosions

Boris Behncke — Wed, 16 Jan 2013 01:21:01 -0000

As a matter of fact, Stromboli is definitely considered a male volcano by its inhabitants - they call it "Iddu", which means "him" in Sicilian. On the contrary, Etna is female, the big "mamma" volcano to the Sicilians :-D