Summary

The 21st paroxysmal eruption of Etna's New SE crater started early on 4 March, following a week of intermittent strombolian activity and accompanied by a steep rise of volcanic tremor. Lava fountains several 100 m tall were rising from the summit crater during the peak phase of the eruption, generating a 2-3 km tall tephra and steam plume, which rose almost vertically due to the absence of strong winds, and drifted SE.
A lava flow was erupted from the SE trending fissure and went towards and partly into the Valle del Bove.
Episodes of violent, explosive lava-snow interaction were observed producing large billowing steam plumes and probably generating small pyroclastic flows, similar to such events during previous paroxysms.

Etna New SE crater paroxsym nr 21 on 4 March 2012

Almost a week has passed since the last paroxysm and Etna has been quiet. It will be interesting to see whether a new eruption is going to happen in the next weeks.

Changes to the SE crater complex

View of the SE crater complex on 6 March, the new eruptive fissure in the saddle between the old and new cone with the lava flow from there are clearly visible

Boris Behncke analyzes the changes brought forth by the 4 March paroxysm (original report on flickr):
"For the first time since the violent episode of lava fountaining (paroxysm) on 4 March 2012, we had a crystal-clear view of the summit of Mount Etna on the morning of 6 March 2012.
... The most interesting detail to be revealed was the new fissure on the southwestern flank of the New Southeast Crater cone, seen here pretty much vertically below the steaming summit of the old Southeast Crater cone (in the left half of the picture).
The fissure ripped open at the climax of the 4 March paroxysm, around 07:50 GMT (= local time -1), and released a lava flow that mixed with thick snow at the base of the cone, generating a pyroclastic flow and a lahar (a volcanic mudflow). The dark streak cutting diagonally across the lower half of the image is the path of that lahar; some of it was later covered by a small lava flow that oozed from the lower end of the fissure for many hours after the cessation of lava fountaining.

All is quiet again, with only some wisps of gas coming from numerous fumaroles (gas vents) on the crater rim, which are incandescent at night. Who knows how long it will take until the next lava fountain, and whether that fissure on the southwest flank of the new cone will open again?"

Eruption has ended

The eruption has ended, this time very quickly as often during paroxysms of Etna. Tremor is back to near zero, and the eruption column and lava fountains have disappeared, as the magma column inside the conduit has dropped.
The wait for the next eruption can begin!

Eruption decreases - probably the near end of the paroxysm

Etna trekking webcam (nr3) 10h12 local time; steam is seen rising from an area SW of the summit cones

The eruption is visibly decreasing in strength, and tremor continues to drop quickly. If the paroxysm follows the usual pattern, the eruption will probably be over soon.
Steam and dust obscure views, but it seems that there is either a lava flow on the SW or western side, or another pyroclastic flow reached the S-SW flat area beneath the summit cones, near Torre del Filosofo, and far from the erupting vent (see webcam images).

Thermal image of the eruption column from Etna's NSEC seen from Nicolosi		Volcanic tremor signal dropping sharply from its peak

The eruption is still going strong with tall lava fountains rising near vertically from the NSEC, although mostly hidden behind massive steam plumes. However, the tremor just started to drop sharply, and probably heralds the near end of the eruption.
This would make it a relatively short paroxysm, especially when compared to the previous one on 8 Feb, which lasted about 6 hours.
The following video shows the pyroclastic flow we mentioned earlier during the probably most spectacular phase of the eruption, when a new vent opened on the SW flank in the saddle between the old SE and the New SE cone, generating a pyroclastic flow caused by violent mixing of ejected lava and debris with rapidly evaporating snow.

The eruption column rising 2-3 km estimated from the webcam image		Thermal image showing the lava fountain\'s heat

A massive steam plume generated by snow-lava contact is seen rising from behind the cone on the western side		Shortly after, the plume has mostly dissipated, but it does look as if the event was a pyroclastic flow that has reached considerable distance to the SW, where now a weaker steam plume rises. Field work and observations from closer location will probably better explain this soon
Volcanic tremor at 50 times background levels near the climax of the eruption

A massive steam plume is rising from somewhere behing on the western side of the cone; it could be a lava flow entering fresh snow there or a pyroclastic flow generated by heavy impacts of incandescent scoria on snow, generating violent phreatomagmatic explosions.

New paroxysm of SE crater (nr 21)

Etna in eruption
The typical rise of the tremor signal
Thermal image showing the heat of the lava fountain and the rising ash and steam plume

The hoped-for paroxysm of Etna's New SE crater started during the night and is now in full swing as can be seen on both the tremor signal and the webcams. This makes it nr 21 in the series of eruptions that began in 14 months ago, or the 3rd event in 2012.
Lava fountains are now rising from the crater along with a dense column of tephra and steam reaching about 2 km and drifting SE. A lava flow can be seen flowing from the southeasterly aligned fissure taking the normal path towards the Valle del Bove.
The eruption is still increasing in strength, but is probably already near its peak.

Strombolian activity at the NSEC at 22h16

Anther snapshot of an eruption at the New South East Crater (NSEC). Activity seems more regular than during the previous week.

Weak strombolian activity continues from New SE crater

Strombolian eruption at Etna early on 29 Feb, webcam image on the evening of 3 Feb

Occasional strombolian explosions are occurring from the summit vent of the New SE crater. At the moment, the tremor signal is very low and not indicating that a paroxysm is to be expected in the immediate future.
Sporadic small strombolian explosions from the New SE crater have been observed tonight again, occurring at irregular intervals during more active phases with 10-15 explosions per hour alternating with phases of quiet of sometimes several hours.
It seems that the activity has gone down, as there seem not to have been new eruptions over the night. Tremor as well is at low levels, but that can all change quickly.

New strombolian activity from New SE crater

Strombolian eruption at Etna early on 29 Feb, webcamp image captured by Etna Walk (www.etnawalk.it)

Sporadic strombolian activity has resumed at the New SE crater early on 29 February. Explosions have been occuring at varying intervals between few minutes and more than 2 hours. The explosions were up to a few tens of meters high and occasionally threw incandescent bombs onto the southern flank of the cone.

Elevated volcanic tremor could be from deep explosive activity within North-East crater

Volcanic tremor signal at Etna on 28 Feb 2012

At the moment, there is no visible activity at the New Southeast Crater, Boris Behncke reports form the INGV control room on a comment on the Eruption Blog. The sometimes elevated tremor could possibly originate from activity deep within the Northeast Crater, which has shown heightened levels of activity in these past few days.
"The rising volcanic tremor amplitude is not a true increase in the volcanic tremor, but an effect of numerous (and increasingly frequent) explosive events within the Northeast Crater.
The constant ground vibration (the true volcanic tremor) is rather weak, but for the calculation of the RMS tremor amplitude graph, 5-minute intervals are averaged, and these include many of the explosion signals, so the tremor amplitude appears elevated.
In any case, Etna is a bit restless, but the situation is currently different from the typical "prelude" of a new lava fountaining episode ..."

New weak strombolian activity from New SE crater

Volcanic tremor recording of INGV Catania

Weak strombolian activity has resumed inside the New SE crater early on 24 February, Etna Walk reports. The eruptions were not observed directly, but could be clearly heard even from some distance such as Pedara village on the southern flank of Etna, and were occurring at intervals of tens of minutes over the day. No incandescence was seen at night, suggesting that this activity is still deep within the crater.
Volcanic tremor is still at low levels, but has recovered from the drop after the rise observed over the last weekend.
After a few days of bad weather and heavy snowing, the upper parts of Etna are now white except the still warm recent lava flows. Whatever has caused the gradually rising tremor signal up to Tuesday, possibly (but speculation) a rise in the magma column inside the conduit feeding the New SE crater, and triggering expectations to see the 21st paroxysm soon, seems to have ended - the signal is now back down at normal background levels.
The tremor continues to go up and down, but has a decreasing overall trend now.
Etna is unpredictable. Just after our previous update, the tremor signal (currently the only available indicator) dropped sharply to almost half its value. Probably, no "show" tonight!
The tremor is still rising, and the signal looks very similar to the initial stages of most paroxysms during the past 13 months. Unless Etna is doing something quite different (which is very possible, too), it seems more and more as if the next eruption could happen very soon.

Tremor continues to rise slowly, but bad visibility

Tremor signal on 21 Feb 2012
Montagnola webcam image - it's snowing up on Etna

The tremor continues its gradual increase towards suspicious levels, but unfortunately, the weather is very bad at the moment to see what is going on.
No explosions were noted during the previous 3 days, but an incandescent spot on the southern rim of the New SEC was visible, suggesting that temperatures there were increasing. Something might be in the making...