Report on Etna (Italy) — June 1976
Natural Science Event Bulletin, vol. 1, no. 9 (June 1976)
Managing Editor: David Squires.
Etna (Italy) Explosions from Bocca Nuova and The Chasm; lava flows on N-flank
Please cite this report as:
Global Volcanism Program, 1976. Report on Etna (Italy) (Squires, D., ed.). Natural Science Event Bulletin, 1:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197606-211060.
37.748°N, 14.999°E; summit elev. 3320 m
All times are local (unless otherwise noted)
Observations were made by the University College group and R. Romano of the IIV, 16 May-4 June 1976. Until this time weather conditions had been very bad on the volcano and reports of activity were sporadic. In the summit region, Bocca Nuova was fuming strongly and had a depth estimated to be in excess of 200 m. This pit was exploding throughout the period of observation, at rates varying from one explosion per 3 minutes up to 2 or 3 explosions/minute. Incandescent material was occasionally thrown above the level of the crater rim and vesicular scoria and Pele's hair fell close to the crater down-wind. The Chasm was also fuming strongly, and although its bottom was not seen, it had a depth of several hundred meters. During the afternoon of 25 May the Chasm started deep violent explosions at a rate of 20-25/minute. No bombs were seen from these explosions, and the activity died down over the next few days. The new pit on the W side of Northeast Crater was fuming quietly but not exploding. The area around this new pit contained large amounts of sublimates and its total depth was around 50 m. The Northeast Crater itself is now inactive, the vent being plugged by scree; but there is still heavy fumarolic activity high on the W inside wall.
The effusive activity during the period was occurring from new vents on the N side of the mountain (near Punta Lucia). A 40-m-high cone formed at about the 2,900 m level. Inside this cone was a conelet from which mild strombolian explosions of fresh gassy lavas were occurring on 26 May, though it was quiet on 31 May. Lava emissions were taking place farther downslope in the new lava field, from a number of boccas with positions that changed from day to day in an area above the 2,500 m contour. The rate of emission from one bocca was measured to be 0.4 m3/sec. and the total emission for the whole field was 2 m3/s.
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: J. Guest, J. Murray, S. Scott, and W. O'Donnell, Univ. of London; R. Romano, IIV.