There be Eruptions!

Photograph by Nina Slaschilina of Tolbachik. You can find more of her stunning photographs at http://slashchilina.livejournal.com

It has been a fairly hectic week in volcano land. No less than 3 volcanoes have been discussed during the week. Most of them are known to the readers of the blog, but I thought I should write a bit about them anyhow.

Global Volcanism Program

Tomorrow Monday the new GVP site premieres to the joy of all interested in volcanoes. The old site functioned fairly well as a “who’s who” among the volcanoes. But it was antiquated from both a technical and a scientific standpoint. The hopes are high, so let us not be too disappointed if our obscure favorite volcanoes are not mentioned this time around.

Pavlof

Photograph thanks to Kirby Morgan over at Tuff Team. Lava showing at the top of Pavlof.

Out in the Aleutian arch we find the Emmons Field Caldera. On the flank we is the most active volcano in the chain. So, it is no great surprise that Pavlof is erupting yet again. Ash has been ejected up to 3 kilometers above the crater and magma is now showing at the crater rim.

One thing to remember about Pavlof is that the eruption normally tends to increase towards the end of the eruption. So we will probably have time to get back to this particular volcano. The biggest problem with the Alaskan volcanoes is the cut backs in the funding of the Alaskan Volcano Observatory. Something that greatly endangers flight traffic in the area, short sighted politicians once again hindering both science and endangering civilian lives.

Popocatépetl

Photograph of Popocatépetl from Global Volcanism Program.

Activity at the second tallest volcano in North America has been ongoing since the latest eruptive cycle started in 2011. Last couple of weeks the activity has increased enough for the authorities to prepare for evacuations, and also to increase the size of the exclusion zone.

Nothing points towards this eruption growing out of control even though Popocatépetl has the potential for something really dangerous, namely Mount St Helens type explosive failures spreading large debris fields. The current risks are lahars and pyroclastic flows travelling down valleys surrounding the volcano.

Tolbachik

Photograph by Yuri Demyanchuk. Here one can clearly see the scale of the event. This tongue of the flood basalt looks small untill one sees that the grass are tall trees. Thanks to UKViggen who found the image.

Some volcanoes really fly under the radar. Tolbachik is a stunning example of this. It is having the largest effusive eruption since the Krafla Fires, and the largest eruption of any volcano this century. With the latest increase in activity it is estimated to have erupted 2 cubic kilometers of lava in the form of a flood basalt, built a few cones, and suffering from constant strombolian activity at the central vent.

Let us put that into perspective. Total amount of ejecta is about one fifth of the VEI-6 eruption of Pinatubo, one ninth of Lakí and a whopping twenty times more material ejected then during Eyjafjallajökull.

I do not know who took this image. Dr Carmen Morataya sent it to me. It really shows how astounding Tolbachik is.

One thing that I started thinking is that Tolbachik is about as gassy as its Icelandic counterparts. The likely hood is that the gas has affected the weather inside the temperate zone weather cell across the globe. We have to wait for the temperature tally, but I would not be surprised if that was the fact in the end. Remember, we are talking about 1/9 of Lakí.

CARL

The Usual Suspects and Friday’s NtV Riddle

Photograph by Eggert Norddahl under exclusive right to Volcano Café. Hekla 1980 eruption.

We are minutely studying any hiccup from the Icelandic Usual Suspects. In the case of earthquakes we are quite used in getting all sorts of useful stuff out of them. One of my favorite ways of studying earthquakes in volcanoes is the cumulative seismic release (CSR). In the case of Grimsvötn it might even be the perfect way of predicting how close he is to erupting. Except for Hekla the Icelandic volcanoes are rather noisy, but how noisy is a volcano in the making?

I had this question ringing in my head yesterday so I tallied up the sums for Iceland’s only known proto-volcano, the Gódabunga cryptodome. A cryptodome is a magmatic emplacement that is unerupted; it is a magmatic system in the making. Normally it suffers several magmatic emplacements before erupting, but most often a cryptodome never erupts. The reason for them not erupting is that it takes a tremendous amount of energy and pressure for a volcanic opening to form. These virgin territory emplacements are hideously noisy compared to a regular volcano.

I had handy data for Eyjafjallajökull, Gódabunga, Grimsvötn, Hekla, Katla and Torfajökull. I discarded Hekla since it would not even show as a speed bump compared to the others. In the end the results got interesting.

The data is from July 1991 up to February 2013 except for Grimsvötn (1996). Energy is in Joules, as a comparison one could use a Big Mac; at 540 kilocalories it has 2.2 million Joules of energy (roughly equivalent to a 1.1M earthquake).

Eyjafjallajökull

Photograph by Eggert Norddahl under exclusive agreement to Volcano Café. Eyjafjallajökull eruption 2010.

Eyjafjallajökull was rather active before the eruption in 2010, the total CSR was 6.8e+9 and otherwise Eyjafjallajökull was rather quiet during the period. The total tally including the VEI-4 eruption during the period was 1.06e+10. As you will notice this is surprisingly little. Let us now walk over to the quiet neighbor to the north. After the eruption this volcano has been very quiet.

Torfajökull

Torfajökull, the forgotten and quietly playing volcano.

This volcano latest erupted in 1477 and has since then not erupted, but it is still active. It suffers from two opposite forms of earthquakes. It simultaneously has earthquakes associated with cooling magma, and earthquakes associated with magmatic emplacement. It is probably safe to assume that this large volcano has more than one chamber, and that the most likely spot for an eruption will not be at the same place as the last one.

It would therefore have been interesting to have these earthquakes separated, so we could compare. But alas, we do not have that. The total sum during the same time period is 4.8e+9. Except for 2010 Torfajökull had higher CSR then Eyjafjallajökull during the entire period.

Grimsvötn

Photograph by Eggert Norddahl under exclusive agreement to Volcano Café. Grimsvötn 2011 eruption, sun over ash cloud.

For being a very large volcano Grimsvötn is surprisingly quiet. The earthquakes during the period from 1996 are rather even over the years, with the only exception being
the period after the 2011 eruption where the volcano has been very quiet.

Grimsvötn seems to erupt as soon as it has reached a certain value of CSR. At least it did that the last two times in 2004 and 2011. That value is slightly more than 3.8e+9. The total strain release between 1996 and now is 7.7+9e, or slightly more than Eyjafjalla released in the 3 months before erupting up to the end of the eruption. Who thought Grimsvötn would be the shy quiet one?

Katla

I guess nobody will be surprised that Katla is a noisy volcano. It suffers from numerous small to medium sized earthquake swarms. Many of those are signs of magma entering the system. The noisiest year was 2011-2012 when the volcano suffered from a CSR of 8.9e+9. During the entire time the CSR was 3.1e+10. Now, let us go and visit the noisy unborn baby volcano next door.

Gódabunga

Gódabunga Núnatak next to the SIL station.

Gódabunga was a quiet unassuming little Núnatak (cliff protruding above a glacier) just on the outside of the caldera wall of the massive Katla volcano when, to the surprise of everyone, it started kicking around. In 96-97 it had a CSR of 1.8e+9 and most thought it was Katla having a side emplacement. The next year it got a CSR of 6.5e+9 and it was noticed that the hypocenter of the earthquake ball was outside the Katla system. It caused a bit of a stir; remember that all of a sudden out of the blue there was more CSR than Grimsvötn produces during the entire run up to an eruption.

For two years it was showing signs of calming down after the initial emplacement. Gódabunga seemed destined to dwindle into the mist of magmatic emplacement history, the same way 99 percent of all emplacements go.

After the two years Gódabunga went on a massive spree of large emplacements that really knocked on the roof of the teenage room.  During the next five years it had at least two more even larger emplacements than the initial one. The CSR for the period was 6.03e+10 with the record year (2002-2003) blasting an impressive CSR of 1.83e+10.

After those five years Gódabunga has calmed down, but the CSR is still 100 times higher than before the commotion started. The total release during the period is a whopping 9.02e+10.

What will happen to Gódabunga is written in the stars so far. Remember that science have never seen a large new volcano blast into life, especially never with instrumentation like this. The ones science has seen have been rather small, and they have been un-instrumented. If Gódabunga ever is born we only know one thing, it will be very noisy.

Ruminations

For those who are surprised over how quiet Grimsvötn is should remember that this volcano is erupting often. The system is permanently heated and filled with magma, so the roof over the chambers cannot withstand a lot of pressure. One should also note that the earthquakes in a volcanic system are a sign of pressure increase (or in some cases of pressure decrease as magma cools down and contracts). So, Grimsvötn will show comparatively few earthquakes before erupting since it cannot take a lot of pounding.

The fact that Grimsvötn has a weak top is what makes CSR into a good predictive tool. The amount of pressure increase the roof can take will be about the same between the eruptions. At least for as long as the eruptive cycles have roughly the same time spans.

As the roofs above volcanoes cool down it will take more and more pressure for a volcano to break through. Also size and depth of the magma chambers are factors that affect the amount of pressure needed for an eruption to occur.

Eyjafjallajökull had a rather small magmatic system that was fairly close to the surface (after an emplacement just before the period my data covers), so it had a surprisingly small conflagration of earthquakes before erupting.

Katla has not erupted since 1918, and has a very large magma system. So the roof has had time to solidify and can due to the size flex quite a lot over time. So, it is not that surprising that it can withstand a lot of CSR over time.

Gódabunga on the other hand has an unknown size of the magmatic system, but one thing is clear, it is fairly deep down, and the roof is (no pun) rock hard. Here the magma has to quite literally pound its way through layer after layer of hard old rock so naturally there is a lot of music being played. How much more pressure will it take before an eruption occurs? The answer is that nobody knows. All we can do is waiting for a new emplacement and then try to track the progress of the earthquake ball hypocenter upwards. For all we know it could withstand anywhere up to ten times as much CSR, especially if it is temporally well spaced.

Numbers taken from Icelandic Met Office and treated by Carl, then made into a plot by GeoLurking.

If the CSR is a representation of the systemic pressure inside an unborn volcano, the Gódabunga is potentially a bad one. If we compare with El Hierro that had an eruption after a long repose time and had a very noisy eruption the energy released there was still 1 000 times less. In the end we are faced with the small thing that the CSR are caused by a magma emplacement, and the amount of activity gives a hint of the amount of magma emplaced.

CARL

Name those Volcanoes Riddle

 1 point for each Volcano …

No 1 - Legendary lost home of the hairy eared dwarves? SOLVED Mount Shasta 1 point Sa’ke

http://en.wikipedia.org/wiki/Mount_Shasta

http://en.wikipedia.org/wiki/List_of_lemur_species

No 2 - 4295 eponymous deposit. SOLVED Katla / Vedde Ash 

http://en.wikipedia.org/wiki/Katla_volcano

http://en.wikipedia.org/wiki/Vedde

No 3 - Thoroughly well bred parent of the US Ambassador? SOLVED Acatenango 1 point KarenZ

http://www.sportinglife.com/racing/profiles/sire/98444/acatenango/progeny

http://en.wikipedia.org/wiki/Acatenango_(horse)

http://en.wikipedia.org/wiki/Acatenango

No 4 - Slightly under 50 miles north of a pillar of salt. SOLVED Aukland volcanic field 1 point KarenZ

http://en.wikipedia.org/wiki/Auckland_volcanic_field

No 5 - Its location and summit hold a global distance record.  SOLVED Chimborazo 1 point Sa’ke

http://en.wikipedia.org/wiki/Chimborazo_(volcano)

No 6 - Site of the earth’s nastiest outside loo. SOLVED Mount Elbrus 1 point Alison

http://en.wikipedia.org/wiki/Elbrus

KILGHARRAH

A Tale of Three Cities

Photograph by Kevin Sebold. Fuego on a moonlit night.

It was the best of times, it was the worst of times. It certainly was volcanic times. This is the story of three great cities, one lost in the mist of time, one almost gone into the mist of time, and one that is a buzzing metropolis, doomed to disappear into the tephric mist of a time to come.

Welcome to the Capitals of Guatemala.

Ciudad Vieja

Award-winning photograph taken by Dave Wilson from Ciudad Vieja with the Volcan de Agua in the center. This is a digitally enhanced photograph.

Even though Técpan was the first military center for the Spanish invaders it is Ciudad Vieja that was the first real place of government in the colonial era Guatemala. Even more correct would be to say that the first capital of what is now known as Guatemala was the Cakquikel city of Iximché, but let us leave that behind us for now. It was Ciudad Vieja that is interesting for this Tale of Three Cities.

The city was founded in 1527, and had a rather short lifespan. In 1541 Agua suffered a dramatic collapse causing a lahar that totally ruined the city forcing the inhabitants to permanently evacuate the city. For two years Guatemala was without a capital.

Because of the flooding water and the lahar devastating Ciudad Vieja the volcano was renamed into Volcan de Agua. At the same time they renamed the nearby volcano into Volcan de Fuego. Nobody knows what devastated the sides of Volcan de Agua. Most likely it was earthquake activity during a magmatic emplacement at depth, but that is just a theory. What is though known is that the side of the crater gave way, and the crater lake came crashing down picking up any loose items on the way.

Photograph taken by Dr Carmen Morataya for Volcano Café. There are definitly worse places for a morning cup of coffee. Photograph taken from the Hotell Garden towards Agua.

Volcan de Agua is a youthful young stratovolcano with no known historical eruptions. It is though showing low level signs of activity. It is today judged to be dormant, but in a state that can change at any time.

Antigua

Photograph from Wikimedia Commons.

In 1543 the new capital was formed in the next valley. It was named Santiago de los Caballeros. It was probably one of the least fortuitous places to have a capital in. Not only is Volcan de Agua less then 5km from the city, there is also the highly active Volcan de Fuego close to the city. To top it off the city also had to contend with Acatenango. During its history (1543 – 1776) it was inundated under tephras from Volcan de Fuego no less than 23 times, and two of those eruptions were VEI-4 category.

To really make things interesting it is placed on top of an active fault line.

Photograph from the Wikimedia Commons. Church ruins from the Santa Marta Earthquake.

On the 29^th of September 1717 much of Santiago de los Caballeros was destroyed in a large earthquake. More than 3000 building were ruined and the Spanish Crown started to contemplate moving the city. Sadly they contemplated to long.

On the 29^th of July 1773 the Santa Marta Earthquake struck the city with a force estimated to be 7.5 on the magnitude scale. Most of the city was left in burning ruins after the earthquake. Equally devastating was the intensive swarm of unusually powerful aftershocks that hammered the city into December the same year. In 1776 the Spanish Crown finally had it and decided to move the capital to a new safer spot. The new city was named after both the region and the country for good luck. Now we know that the move was from the ashes into the fire, quite literally. But we will get back to Guatemala City in the next installment.

Left were the ruins of the old capital, now renamed into Antigua Guatemala, basking in the shade of its large volcanoes.

Acatenango & Volcan de Fuego Massif

Acatenango and Fuego are joined to the hip quite literally. It seems like they do not share the same magmatic system, even though some researchers have extemporized that the magmatic system of Fuego runs through the magmatic system of Acatenango. The reason for this theory is to explain that some of the eruptions of Fuego carry magmatic signatures from Acatenango, but Acatenango never have the magmatic signature of the bulk of Fuegos eruptions. Be that as it may, the two volcanoes have rather different patterns regarding their eruptions.

Photograph by courtesy of Dr Carmen Morataya showing the phreatic crater of Acatenango.

Acatenango has had very few historical eruptions. The last real eruption cycle began on the 18^th of December 1924 with a set of large phreatic detonations; this was later followed by a central vent eruption and a radial fissure eruption from the Pico Central crater. During this eruption the volcano ejected the telltale amphibole bearing dacite that is the most common lava emanating from Acatenango. The eruption ended on the 7^th of June 1925 and was rated a VEI-3. In August 1926 the volcano sprang back into life with a new set of phreatic detonations followed by renewed lava ejection from the north flank of Pico Central. The eruption ended on the 19^th of May 1927 and was rated a VEI-2.

On the 12^th of November 1972 a set of phreatic detonations started that lasted for about a month. No lava was ejected so it is seen as an aborted eruption. The phreatic detonations was powerful enough to gut the Yepocapa saddle of the Pico Central cone.

Historically Acatenango has not suffered from frequent eruptions. Instead the eruptions have tended towards being larger than the eruptions of its twin Fuego. The greatest risks are the well documented deep layers left from large scale pyroclastic flows. The flow fields from the 370 BC eruption would have eradicated any of the adjacent towns and villages in an instant. Therefore the authorities would be well advised to prepare proper evacuation maps of all the possible routes pyroclastic flows can take from Acatenango and put in place large scale evacuations in case Acatenango rumbles back in to life.

Volcan de Fuego erupting with Acatenango in the forefront.

Volcan de Fuego was born out of the scrap heap left by the massive Meseta volcano when it went lumbering towards the ocean in the Asquintla debris avalanche. Fuego is one of the two most prolific volcanoes in Guatemala. One could almost say that it is erupting more often than it is resting.

Normally it has small to moderate sized eruptions with an average of VEI-2. But it quite often has short-spanned VEI-3 eruptions that are more of a bother for the locals. Two VEI-4 eruptions are documented, the last in 1974 when it had numerous pyroclastic flows killing residents in nearby villages.

Fuego shows a varied pattern of behavior ranging from lahars and pyroclastic flows (the killers), via lava bombs and lava flows from central vents and fissures to spine growths and exploding extruded domes. These varied behaviors make Fuego into a fairly unpredictable volcano. What is lacking is good mitigation with pre-prepared evacuation maps from the valleys most affected by pyroclastic flows and lahars. Also the will to evacuate and being evacuated is slightly low locally, something that can be understood if one think about that the people in the villages are really poor without the means to support themselves if they evacuate.

If you think this was bad choice for cities, just wait until the next installment of A Tale of Three Cities.

CARL

P.S. Do not miss the expert comments at the end of the comments section. D.S.

Countdown to Hekla

It has been a long time since I wrote about Hekla. But, I guess nobody is surprised at what I am about to write.

Everyone with a genuine interest in volcanoes have their favorite volcano. As many in here know Hekla is my favorite volcano to bang my head against. Few volcanoes are as intricate as Hekla, and few have such a short run up before an eruption as Hekla. Normal run up time to an eruption is between 30 – 80 minutes from the first sign.

This time around has been different. But let us first recapitulate what has happened since the last eruption. For those who are curious about how Hekla works I would like to recommend my own post about her innards:

http://volcanocafe.wordpress.com/2012/01/10/deconstructing-hekla-hells-gate-revisited/

Background

In 2004 Hekla had received as much new magma as was discharged during the 2000 eruption and sometime during late 2008 to early 2009 that figure had doubled. After that the inflation stagnated and no real uplift was measured at the GPS-stations with the exception of what was most likely magma moving between the different magma chambers.

During the summer of 2011 earthquakes was registered and a public safety alert was issued stating that Hekla was close to erupting. From then on Hekla has had earthquakes ranging from miniscule to 2M+ without erupting. For those who are not familiar with Hekla one should notice that she normally is aseismic, or in other words, that she does not have a lot of earthquakes.

From 2010 and onwards Hekla started to show a new feature that I dubbed “transients”. The transients are sudden rapid drops in the strain measured at the borehole strainmeters. These transients have only been seen before as Hekla erupted. They had before 2010 never been seen without an eruption occurring. A transient is in short happening as the mountain strains to open up.

On the 13^th of March and onwards Hekla had a swarm of earthquakes and once again transients were noticed on the strain-meters. There was also harmonic tremor measured indicating rapid movement of magma. This caused IMO to issue a public safety warning, and the London VAAC issued a flight code warning Orange. This followed the exact pattern of how all the previously instrumentally monitored eruptions had started so far.

As we all know nothing happened in the end. We can now safely say that we know even less than we did before about how Hekla acts before an eruption. Because now we have to figure out why Hekla did not erupt when she should have. I guess someone will have a research career out of it in the end.

Present

After this Hekla entered into a new phase never seen before, this time a phase of very rapid and unbroken inflation started. What happened is most likely that the earthquake swarm removed blockages inside the deep feeder tubes of Hekla enabling fresh magma to flow into the volcanic system.

The rate of inflation varies a lot depending on where the GPS station is placed. The big exception is Mjóaskard situated to the west of Hekla. It has only suffered an uplift of 5mm in the last 5 weeks. For the other stations the rate of inflation is between 15mm in Hestáalda and 32mm at ISAK. Average uplift is 16mm, and 21mm if MJSK is not counted. This type of rapid inflation has so far never been measured at Hekla.

http://strokkur.raunvis.hi.is/~sigrun/HEKLA.html

During the entire inflation phase there have been scattered earthquakes and micro-quakes.

If the current rapid inflation continues there is a very low chance of Hekla not erupting. Yes, we do not know what is happening with Hekla now since we have never seen this type of behavior. But Hekla is constructed in such a way that she can’t take a huge increase in pressure without erupting.

Image by GeoLurking based on data by the University of Iceland and Professor Sigrún Hréinsdóttir. All areas are showing uplift on this image covering the period from 4th of April up untill now. The area with the highest uplift are due north of Hekla.

If the inflation continues at the current rate Hekla will erupt. When? Well I am not going to make any bets, but any time from 1 hour from when you read this to 4 weeks. Remember that 4 weeks into the future the combined uplift in 2 months will have exceeded 50mm at many GPS stations. As seen on the image above the largest uplift is happening on the northern slopes. This is a known site for one of Heklas primary magma chambers. The area to the northeast are not showing correctly, there is uplift there too, but due to lack of a GPS station there the model get scewed.

Image courtesy of the University of Reykjavik and Professor Sigrún Hréinsdóttir.

I personally would not at any cost get closer to Hekla then 10 km from now on. And then I would stay in the car on the road. If you are closer the chance of you surviving is not good and 5 km the chance of you surviving the initial blast is pretty much nill.

What will the eruption be like? Here I will be guessing since Hekla has changed her behavior compared to the last eruptions. I would say that Hekla has remobilized old evolved magma during all that moving of magma, and this latest inflation phase seems to fill up a lot of old magma chambers. This causes me to fear a rather explosive start of the eruption. I would also say that there is quite a high likelihood of there being more lava erupted then was seen during the last 3 eruptions. I will hedge my bet by saying that I would expect it to be anything between a VEI2 and a VEI4 on the volcanic explosivity index, and that Hekla will effuse between 0.1 to 2 cubic kilometers of lava. Based on the GPS plot above my best judgement is that the eruption will start at the top of Hekla proper and then open up the fissure both to the south, but mainly to the north. Most probably the Hekla fissure will open over all of Hekla proper with a fissure extending to the Northeast.

For those who wish to follow the eruption, here is the Hekluvöktun page:

http://hraun.vedur.is/ja/hekla/

CARL

Etna’s paroxysm overview

Since the beginning of this year, Inge B. has kept track of all of Etna’s activity this year and has submitted a summary to keep track of all this for everyone. By now, we have seen a dozen of paroxysms and several other instances of activity at various craters, so it is easy to see people get lost there. For that reason, a table has been made by Inge B. (thanks for that!) which I have sort of converted to wordpress-language.

Etna summit craters map. Image by INGV

Bigger eruptions	Date	Summit craters involved	Characteristics of activity
	9-15 Jan 2013	Bocca Nuova (BN)	Vigorous Strombolian eruption after 3 months quiescence at this crater which had had its first magmatic activity after 10 years again in 2011.
	16 Jan 2013	BN	Strombolian activity
	18 Jan 2013	BN	Strombolian Activity
	20 Jan 2013	New SouthEast Crater (NSEC)	Strombolian activity, first magmatic activity after 9 months quiescence at NSEC
	22 Jan 2013	NSEC	Strombolian activity, more intense than the last ones, bombes rose up to 100 m above crater rim
	28-29 Jan 2013	BN   NSEC	Vigorous Strombolian activity, rumbling noises, to be heard in vicinity of craters Weak Strombolian activity; rhythmic degassing with slight ash content. First time since 12 years, simultaneous activity from 2 summit craters
	30 Jan 2013	BN	Intensive Strombolian activity, launching bombs to about 120 m above crater rim
Paroxysm 1	19 Feb 2013	NSEC	Lava fountaining with production of lava flows, pyroclastic flows, lahars and ash cloud
Paroxysm 2	20 Feb 2013	NSEC	Lava fountaining, lava flows, ash
Paroxysm 3	20 Feb 2013	NSEC	Lava fountaining, lava flows, ash. Second paroxysm that day
Paroxysm 4	21 Feb 2013	NSEC	Lava fountaining, lava flows, ash; 4 paroxysms in 48 hours is very rare
Paroxysm 5	23 Feb 2013	NSEC	Lava fountaining, more intense than before, fountains up to 800 m high, lava flows, ash cloud containing scoriae
	27 Feb – 4 Apr 2013	BN   Voragine (VOR)	Strombolian activity, weak lava fountains continuing through 28 Feb 2013 Explosive activity, first activity of VOR since 1999. Strombolian activity in the night before Paroxysm 6. Still ongoing Strombolian activity with stronger explosions in between, small ash emission, volcanic bombs during Paroxysm 7. Weak Strombolian activity still ongoing; after activity ceased at NSEC at Paroxysm 8, strong explosions at VOR. Weak Strombolian activity still ongoing at Paroxysm 9.
Paroxysm 6	28 Feb 2013	NSEC	Lava fountaining; eruptive fissure opened in the saddle between the Southeast Crater and the New Southeast Crater, lava flows; ash plume, scoriae fallout
Paroxysm 7	5-6 Mar 2013	NSEC	Spattering from new fissure in the saddle between the SEC and the NSEC; lava flows then lava fountains up to 800 m high; intense fallout of scoriae in adjacent towns and villages down to Taormina on the Ionian Coast
Paroxysm 8	16-17 Mar 2013	NSEC	Slow increase of Strombolian activity; lava fountains, ash and scoriae fall, rather violent paroxysm with several loud bangs heard in population centers around the volcano, gas rings; lava overflow, up to 800 m high lava fountains, ash plume 2.000 m high, lightening within the plume; downpour of heavy material, volcanic bombs and big scoriae in the summit area; after explosive activity ceased: small collapses and slides of still hot material
Paroxysm 9	3-4 Apr 2013	NSEC	violent paroxysm, only short time lava fountains, but very loud explosions, noise heard tens of kilometers from the craters, opening of new vents on the NSEC, production of small pyroclastic flows in the summit area (summit area declared “off limits” by the authorities after this episode); ash and scoriae fall in adjacent towns and villages
Paroxysm 10	8-14 Apr 2013	NSEC	Long run-up phase beginning on 8. April with loud Vulkanian (?) explosions (heard tens of km away), some rather heavy explosions with ash emission, followed by a period of Strombolian activity of increasing intensity culminating in lava fountaining on April 12, emission of tephra, ash and lapilli as well as lava bombs, less ashfall though than during Paroxysm 9 and the ones in March 2013; lava flow into Valle del Bove; repeated collapse at NSEC, leading to formation of a depression in the cone lava flow from “saddle” between SEC and NSEC in direction of Belvedere activity also from 2 vents at the base of NSEC on the same day; landslide; small pyroclastic flow two days following of declining activity with some production of weak lava flows
Paroxysm 11	18 Apr 2013	NSEC	From 16 April on some explosive activity at NSEC, ash emissions, small Strombolian eruptions, slowly increasing paroxysm with lava fountaining in the morning of 18. April; eruption cloud with ashfall and lapilli dispersion in direction S-SW; big lava flow into Valle del Bove, two smaller ones from the “saddle” between NSEC and SEC in directions N and S weaker Strombolian activity still ongoing since morning of 19 April
Paroxysm 12	20 Apr 2013	NSEC	Violent activity, ramping up quickly. Fountaining up to 1000 m high with column of gas, ash and lapilli and heavy tephra fall on the east flank. Downpoor of lapilli on the highway Catania-Messina near Giarre. Intensity approximately 30% higher than previous paroxysms.

Sources:
INGV Catania (also for the pictures), reports http://www.ct.ingv.it/en/ (English)
for the 9th paroxysm: http://www.ct.ingv.it/it/component/content/article/11-notizie/news/868
(Italian)
for the 10th paroxysm: http://www.ct.ingv.it/en/component/content/article/11-
notizie/news/875 (English)
for the 11th paroxysm (as per April 20, 2013): http://www.ct.ingv.it/en/ (English) and
http://www.ct.ingv.it/it/component/content/article/11-notizie/news/880 (Italian)

Photo of Paroxysm 10 at the 12th of April 2013. Photo by etnawalk.it

El Nathan