Report on Etna (Italy) — December 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 12 (December 1986)
Managing Editor: Lindsay McClelland.
Etna (Italy) Lava flows; Strombolian activity; ash emission
Please cite this report as:
Global Volcanism Program, 1986. Report on Etna (Italy) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:12. Smithsonian Institution.
37.748°N, 14.999°E; summit elev. 3320 m
All times are local (unless otherwise noted)
"The eruption was continuing in early January. Strong gas emissions continued from the eruptive vent at ~ 2,600 m altitude. Lava continued to flow into a tube that extended from the base of the vent to ~ 1,800 m altitude, where there were ephemeral effusive vents that varied in number and position. The lava flows that originated from these ephemeral vents did not advance below 1,500 m altitude, and remained in the center of the Valle del Bove.
"The Strombolian activity at Conetto Rittmann (2,350-2,300 m altitude), at times from as many as three explosive vents, included periods of greater or lesser activity, but diminished gradually. From the beginning of January, the Strombolian activity was almost totally replaced by more or less violent explosions of gray ash. Lava flows originating at the base of Conetto Rittmann (recently more than two lobes have been noted) usually reached 1450 m altitude, passing N of Rocca Musarra, where they stagnated. The rate of lava production varied considerably with time. At the pit crater at ~ 2,850 m altitude, only gas emissions were observed. More or less violent explosions of reddish ash continued from the E vent of the central crater (La Voragine) alternating with periods (more rare) of vapor emission. Gas emissions from the other summit vents (Bocca Nuova, and Southeast and Northeast craters) were continuous but of varying strength.
"During this period, no seismic shocks were recorded. Volcanic tremor remained at rather high levels, with sporadic variations associated with the trend of the eruptive activity."
Further Reference. Kieffer, G., and Tanguy, J.C., 1987, L'activité de l'Etna en 1986: Bull. Sect. Volcanol. Soc. Géol. Fr., no. 3 (January 1987), p. 3-6.
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, T. Caltabiano, and D. Condarelli, IIV; S. Gresta, Univ di Catania.