The 2002–03 Etna explosive activity: Tephra dispersal and features of the deposits

Abstract

The onset of Mt. Etna's 2002–03 eruption was marked by intense explosive activity beginning on 27 October 2002 and persisting until 30 December. This phase of activity produced abundant ash emission that impacted the local economy and air traffic. Thereafter, explosive activity declined with the eruption ceasing on 28 January 2003. In this paper, we present field data collected during the eruption and use these to obtain input data for tephra dispersal model. This was applied, after validation, to extrapolate the total distribution of the deposits emplaced during the explosive activity. Detailed sampling of fallout deposits was completed on 27, 28, 31 October and 4 November. This enabled construction of isomass maps and calculation of the erupted mass. Grain‐size analysis of all collected samples was used to reconstruct the total grain‐size distribution which displays a peak at 0.5 Φ. Column height was estimated at 3.3–7 km by combining barometrical altimeter data during over‐flights with the analysis of images and videos. This was used to estimate a total erupted mass of 4.4 ± 0.6 × 1010 kg. Simulations showed that the deposit was significantly affected by variations in wind direction and mass eruption rate, with deposits being dispersed mainly on the E sector of the volcano due to a dominant easterly wind. Our study underlines that basaltic volcanoes, such as Etna, can produce huge amounts of ash, as well as lava, and that an improvement in the knowledge of dispersal processes during prolonged explosive activity is required to better mitigate the associated hazards.

Tephra hazard assessment at Mt. Etna (Italy)

“…These eruptions have been thoroughly described for tephra fallout dispersion and eruptive parameters (e.g. Andronico et al, 2008). 4.4 × 10 10 7 0.5 1.5 ERS-WLL 1.5 × 10 6 -5 × 10 9 3.6-7 −0.5-2.3 1.5…”

“…Andronico et al, 2008), from satellite retrievals (e.g. Prata and Grant, 2001) and/or analysis of the field deposit (e.g.…”

“…Lapilli and ash mainly covered the eastern sectors of the volcano due to dominant winds that blew eastward. A total volume of 4.4 ± 0.6 × 10 10 kg and a total grain-size distribution peaked at 0.5 ϕ were estimated by Andronico et al (2008). Over the past three centuries, this activity has been considered comparable only with the 1763 eruption (Andronico et al, 2005) The OES-WLL probability maps were compiled considering an eruption lasting 100 days and producing a weak plume of 7 km a.s.l.…”

Selenium mobilization in soils due to volcanic derived acid rain: An example from Mt Etna volcano, Sicily

“…Even though ashes were deposited mainly on the southern and eastern flank of the volcano, deposition also took place on the western and northern flanks (Andronico et al, 2008a). In the year prior to sampling (June 2008; Section 3) some events produced minor contribution of pyroclastic materials.…”

TError: towards a better quantification of the uncertainty propagated during the characterization of tephra deposits

“…where H is the maximum plume height (km above the vent) and k is an empirical constant typically set to 0.236 for silicic magmas and between 0.244 and 0.295 for andesitic/basaltic magmas (Andronico et al, 2008;Scollo et al, 2007;Wehrmann et al, 2006). Mastin et al (2009) compiled published data for about 30 well-constrained eruptions in order to empirically identify a best-fit relationship between the plume height and the volumetric flow rate (m 3 DRE s −1 ).…”