Report on Etna (Italy) — 25 January-31 January 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 January-31 January 2017
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2017. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 January-31 January 2017. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
INGV reported that on the morning of 15 December 2016 minor emissions of brownish ash rose from the vent in the saddle between the newer cone and the old cone of Etna's Southeast Crater (SEC). That evening some of the emissions were more energetic, ejecting incandescent material out of the crater which landed on the steep S flank of the SEC cone. Analysis of samples of the ejected rock revealed no new material, only older material from the conduit walls. During the following five weeks weak ash emissions from the vent were observed, without being accompanied by incandescence.
During the early morning of 20 January the saddle vent was again active, with small black ash puffs and thermal anomalies identified by the surveillance camera. People on the SEC observed ejected incandescent material along with ash and blocks. Cloudy weather prevented visual observations for a few days; the evening of 23 January was cloud free and mild Strombolian activity was observed, accompanied by frequent emissions of small, black ash puffs. The activity gradually intensified through the night, with some explosions launching incandescent material as far as the base of the SEC cone. Fluctuating incandescence was also visible at the 7 August 2016 vent of the Voragine (VOR) crater. The frequency of explosions and ash emissions increased on 24 January but then slightly decreased the next morning.
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.