Report on Etna (Italy) — February 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 2 (February 1985)
Managing Editor: Lindsay McClelland.
Etna (Italy) Seismicity, then Strombolian activity and lava flows from Southeast Crater; ashfall on coast towns
Please cite this report as:
Global Volcanism Program, 1985. Report on Etna (Italy). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 10:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198502-211060.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
Weak strombolian activity started 8-9 March in the Southeast Crater. Lava began to flow from the Southeast Crater the morning of 10 March and advanced E (toward the Valle del Bove), stopping that night as feeding ended. Mudflows were also observed in the Valle del Bove; heavy rains had caused flooding in Sicily during the previous week. On 11 March, fissures opened on the upper S flank (in Piano del Lago Alto). The press reported that temperatures in some of the fissures were high enough to melt plastic at nearby cable car stations. Ash fell on the towns of Acireale and Fiumefreddo (~20 km SE and 20 km ENE of the central crater). During the morning of 12 March, lava emerged from vents that opened at progressively lower elevations (from 2,620 to 2,500 m above sea level) and flowed S and SSW, reaching 2,250 m elevation by the next morning. Numerous mudflows preceded the lava flows.
An 11 March newspaper article citing the National Institute of Geophysics reported that microtremors with epicenters in the W part of the Valle del Bove had been recorded for the past few days. A M 3.4 event near the central crater occurred 9 March at 1523, and a shock with a focus at 5 km depth was felt 10 March at 1101 in the towns of Linguaglossa, Milo, and Sant Alfio (16 km NE, 11 km ESE, and 13 km E of the central crater). No magnitude was reported for the 10 March earthquake but both events were said to reach MM IV-V intensity.
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.
Information Contacts: R. Romano, IIV; Il Progresso, New York; Corriere della Sera, Milano, UPI.