Report on Etna (Italy) — 6 March-12 March 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 March-12 March 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 March-12 March 2013. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
Sezione di Catania - Osservatorio Etneo reported that during 5-6 March a new episode of lava fountaining occurred at Etna's New Southeast Crater (NSEC). On 5 March an explosion from the vent in the W part of NSEC was detected at 1854 and ejected incandescent bombs several tens of meters above the crater rim. This explosion was followed by similar ones, initially separated by intervals of 15-20 minutes, but then gradually became more frequent. As the evening went on, the activity at NSEC progressively intensified; likewise, the volcanic tremor amplitude started to rise. Around 0012 on 6 March, lava started to flow from the saddle between the two SEC cones; a few minutes later, an eruptive fissure with several vents opened in the lower portion of the saddle. Lava jets became continuous around 0017, forming a fountain that rose 200-300 m above the crater rim. Various vents were active within the NSEC, in the saddle area, and at the base of the saddle, from where a voluminous lava flow expanded S and SE. Around 0100 this lava flow had reached the area of Belvedere station. Lava also flowed through the breach in the SE rim of NSEC.
For the next 30 minutes, lava fountaining continued with jets rising 600 to 800 m above the crater. An eruption column heavily laden with pyroclastic material rose several kilometers above the summit and drifted NE. Deposition was intense on the upper NE flank of Etna, covering the area of the Valle del Leone, Pizzi Deneri, and Serra delle Concazze with incandescent bombs and scoriae. Further downslope, at Linguaglossa, scoria with diameters of several centimeters fell, and ash and lapilli fall was also observed at Piedimonte Etneo, Fiumefreddo, Taormina, and other towns along the Messinian Ionian coast.
Just after 0100, and within a few minutes, explosive activity nearly ceased, with only a few weak Strombolian explosions. During the same time, however, an eruptive vent opened on the lower E flank of the NSEC cone, which produced vigorous spattering and a well-fed lava flow that advanced SE. This activity continued at a slowly decreasing rate for a few days and ceased altogether on 9 March.
At the Voragine, Strombolian activity continued after the 5-6 March paroxysm at NSEC, but then alternated with short episodes of intense Strombolian activity and nearly totally quiet intervals. These oscillations were reflected in the volcanic tremor amplitude, which during the 24 hours following the paroxysmal episode at the NSEC showed about twenty small peaks.
Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.