Report on Etna (Italy) — April 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 4 (April 1985)
Managing Editor: Lindsay McClelland.
Etna (Italy) South-flank lava production continues; tremor energy increases
Please cite this report as:
Global Volcanism Program, 1985. Report on Etna (Italy) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198504-211060.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
"The S flank activity that began 12 March was continuing in early May. During April, the main lava channel was transformed to a continuous lava tube (with at least three 'windows') from 2,510-2,320 m elevation. Around 2,300 m elevation numerous ephemeral effusive vents formed, variable in number and location, from which several lava flows originated and advanced over the lava field or along its E edge.
"The lava flows, directed mainly SE, S, and SSW, have not advanced much, generally stopping at 2,150-2,050 m above sea level. The lowest elevation reached during this period was 1,950 m (20 April). At times (19 and 21 April and 6 May), because of an increase in the production rate, lava overflows occurred following roof collapses in the upper parts (2,510 and 2,485 m elevation) of the lava tube, giving rise to small lava flows of short duration.
"No gas emission was noted from the mid-April hornitos. More or less intense emission of gas and vapor continued from both of the central crater vents; ash emission was very rare. The Northeast Crater generally emitted vapor and rarely (10 April and 9 May) ejected reddish ash.
"The surface covered by lava can be estimated at around 3 km2 and the volume at ~20 x 106 m3. In this period there has been almost a total absence of earthquakes. However, during the week of 8-14 April, 20 shocks with magnitudes less than 3 were recorded. Afterwards, a variation in the main spectral peaks of the tremor was observed. A gradual increase in the tremor energy was observed during the entire month of April (S. Gresta, personal communication).
"The Etna Guides and volunteers from the Italian Alpine Club rescue team cooperated in the collection of information about eruptive activity."
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.