Report on Etna (Italy) — 23 October-29 October 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 October-29 October 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Etna (Italy). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 23 October-29 October 2002. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
A relatively large eruption began at Etna on 27 October, following a series of ~200 small earthquakes the previous evening. The eruption began with fissures opening on the volcano's S and NE slopes around 2,700 m elevation, between Southeast Crater and Montagnola cone. Lava fountains rose 100-200 m, lava flows were emitted from the fissures, and significant ash plumes were produced. On the 28th seismicity continued, with a M 3.8 earthquake occurring beneath the volcano. Lava flows cut across the road connecting the towns of Linguaglossa and Piano Provenzana and lava ignited several forest fires near Piano Provenzana. The lava flows were estimated to be 365 m wide and 6.1 m high.
Ditches were dug in an effort to control lava flows, but by the 29th they were completely covered by lava. Authorities also tried to control the flows by having planes douse the lava with water, causing the flows to cool and stagnate, but they continued to travel down the volcano's flanks. Authorities stressed that the popular ski town of Linguaglossa (6,000 residents), located ~15 km NE of Etna's summit, was not in danger of being engulfed by lava flows. As a precautionary measure ~50 residents were evacuated and schools were closed. By the 28th lava flows had destroyed several hotels, restaurants, a ski school, ski lift pylons, and power lines on the volcano's flanks. Ash fell in towns at the base of the volcano. Some streets in the town of Nicolosi, ~15 km S of the summit, were covered with a 5-cm-thick layer of ash.
During 27 to at least 29 October ash clouds were visible on satellite imagery and the Etna volcano video camera, reaching a maximum height of ~6.4 km a.s.l. The clouds drifted towards the SE and on the 27th one had reached ~350 km S to Libya. From the beginning of the eruption, Catania's Fontanarossa airport was closed. Ash emissions continued on the 29th and a M 4.4 earthquake occurred around 1100, damaging hundreds of buildings in the town of Santa Venerina on the volcano's SE flank.
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.