Report on Etna (Italy) — 23 January-29 January 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 January-29 January 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, 23 January-29 January 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 two episodes of Strombolian activity from Etna's Bocca Nuova Crater occurred during the evenings of 16 and 18 January. Both began with a sudden increase in volcanic tremor amplitude. Poor weather conditions prevented direct observations; the only visible evidence was a bright glow illuminating the clouds covering the summit. On 18 January some clasts were ejected onto the S outer slope of the central summit cone.
On the early morning of 20 January volcanic tremor amplitude again rose, and was much more pronounced at the EBEL station about 700 m from the New Southeast Crater (NSEC) than at the ECPN station much closer to Bocca Nuova. Contemporaneously, there were reports of glow illuminating the clouds over the summit of Etna. Seismic and infrasonic data analyses suggested that the activity occurred at NSEC and consisted of mild Strombolian explosions, which ceased a few hours later.
The next episode began at 22 January. Tremor rapidly rose at 1840 again producing a stronger signal at the EBEL station. Glow from Strombolian activity was first recorded by a camera at 1856; the activity then became more clearly visible and the Strombolian explosions became more frequent. Incandescent bombs were ejected as high as 100 m above the crater rim. The strongest explosions were followed by abundant fallout of coarse-grained tephra onto the flanks of the NSEC cone. Eruptive activity continued for nearly 12 hours with minor fluctuations. Noises produced by the explosions were audible to residents on the E flank. At about 0600 on 23 January the tremor amplitude decreased and the last explosion visible on camera footage was recorded at 0635. During the hour following, a few small, sporadic puffs of vapor mixed with volcanic ash rose from the crater and drifted E.
The two episodes of Strombolian activity at the New Southeast Crater during 20 and 22-23 January represented the first emission of new magmatic products after a quiet interval of nearly nine months. During the past few months, signs of a possible reactivation of the crater were observed, starting with a dull glow coming from within the crater on 22 November 2012 and a series of small vapor and ash emissions during 25-27 December 2012. A short-lived episode of intense glow occurred on the evening of 3 January 2013.
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.