Report on Etna (Italy) — July 1984
Scientific Event Alert Network Bulletin, vol. 9, no. 7 (July 1984)
Managing Editor: Lindsay McClelland.
Etna (Italy) Lava production and Strombolian activity continue from Southeast Crater; strong explosions from Central and Northeast craters
Please cite this report as:
Global Volcanism Program, 1984. Report on Etna (Italy). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 9:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198407-211060.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
"The Southeast Crater eruption was continuing in early August with more or less intense strombolian activity, accompanied at irregular intervals by violent expulsions of dark ash. This activity produced a scoria cone (~50 m high) higher than the rim of the Southeast Crater. The effusive activity took place from vents around 3,000 m above sea level that changed their positions continuously. On 6 August, two effusive vents were active along the old rim of the Southeast Crater, one on the NE edge, the other on the S edge. Some rather well-fed flows originated from these vents. The final flow direction was always E, toward the Valle del Bove. During this period, the lava flows never advanced below 2,600 m. The lava field that formed from this continuous and variable (in terms of intensity and position) effusive activity was larger than 1 km in extent. The volume of lava emitted can be estimated at around 8-10 x 106 m3.
"An increase in central crater eruptive activity was recorded in July. From Bocca Nuova, violent expulsions of gray ash continued at irregular intervals, while on the vent floor, violent and continuous strombolian activity continued. At times, incandescent lava rose higher than the crater rim. The Chasm, after showing activity similar to that at Bocca Nuova in mid-July, was the source of violent activity on 19 July between 1300 and 1700. Very violent strombolian activity ejected incandescent lava fragments about 1 m in diameter to 500 m from the crater rim. The S and N flanks of the central crater were most often impacted by the lava fragments (their average diameter was ~30 m, they fell within an average radius of 300 m)."
The pilot of an aircraft flying near Etna at 1542 on 19 July observed an eruption cloud that reached ~6.5 km altitude. At 1613, the NOAA 7 polar orbiting satellite showed a plume extending 100 km E from Etna.
"After this, the Chasm remained obstructed until 1 August, when it reopened (at 1900) with the expulsion of old material that fell outside the crater rim. On 6 August, this vent was once again obstructed (around 1300) as the result of internal landslides."
"The Northeast Crater, inactive since February 1981, had a violent explosion that ejected old material on 20 July at 1715. Since then, strong emissions of gases occurred from the small vent that formed near the summit."
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; M. Matson, NOAA.