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Report on Etna (Italy) — January 2005


Etna

Bulletin of the Global Volcanism Network, vol. 30, no. 1 (January 2005)
Managing Editor: Richard Wunderman.

Etna (Italy) 7 September eruption continues on W wall of Valle del Bove, includes lava tubes, multiple vents

Please cite this report as:

Global Volcanism Program, 2005. Report on Etna (Italy) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 30:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200501-211060



Etna

Italy

37.748°N, 14.999°E; summit elev. 3357 m

All times are local (unless otherwise noted)


The effusive eruption that started on 7 September 2004 on the W wall of the Valle del Bove continued. Lava escaped at a very low effusion rate from two main vents at 2,620 and 2,320 m elevation. Lava tubes developed downslope of these vents, forming a complex lava-flow field with ephemeral vents at the base of the W wall of the Valle del Bove. After December 2004, effusive vents were mainly located at the lower end of the tube network below 2,000 m elevation. Lava flows were up to 2.5 km long, and the lava-flow field did not change significantly since the end of October 2004 (figure 109).

Figure (see Caption) Figure 109. A map of Etna emphasizing features associated with the lava flow field as they appeared 4 October 2004. Courtesy of INGV.

On 8 January 2005 an ash plume formed above the summit of SE crater and lasted a few hours. Analysis of the ash components revealed that it consisted of lithic material. This episodic ash emission was probably caused by collapse within the crater into the void left after three months of lava output.

On 18 January the INGV-CT web camera located 27 km S of the summit craters revealed a dense, pulsating gas plume rising above the summit of NE crater and lasting a few minutes. This was probably caused by snow vaporization due to hot gas emission from the main crater vent.

During the afternoon of 18 January a new lava flow formed upslope along the 2,620-m-long eruptive fissure, at ~ 2,450 m elevation. The lava flow spread for about 200 m SE on the snow and along the middle wall of the western Valle del Bove. This flow front moved slowly and completely stopped after about 24 hours. The emission of lava from the ephemeral vents below 2,000 m stopped during the effusion from the 2,450-m vent. The lower ephemeral vents again started to emit lava on 19 January. During the afternoon of 22 January two new lava flows erupted from vents at 2,400 m elevation, along the same tube system fed by the 2,620-m-elevation vent. Two parallel, fast-moving flows spread E. They were still evident on 27 January from the images recorded by the INGV-CT webcam at Milo, together with a number of ephemeral vents and small lava flows at the lower end of the lava tube.

The opening of effusive vents upslope along the tube system of a complex lava-flow field has usually indicated the final stages of expansion, an effect observed several times at lava-flow fields on Etna and Stromboli. Decreased effusion from the main vent causes the tube system to drain, so the lava tube walls collapse. Obstruction at the lower end of the tube then causes accumulation of lava farther upslope and the opening of new vents at higher elevations.

Since the start of the eruption on 7 September 2004 (BGVN 29:09), there has been no significant explosive activity at the summit craters or the eruptive fissures.

Geological Summary. Mount Etna, towering above Catania on the island of Sicily, has one of the world's longest documented records of 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 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: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).