Reconstruction of total grain size distribution of the climactic phase of a long-lasting eruption: the example of the 2008–2013 Chaitén eruption
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The 2008–2013 eruption of Chaitén Volcano (Chile) was a long-lasting eruption whose climactic phase (May 6, 2008) produced a sub-Plinian plume, with height ranging between 14 and 20 km that dispersed to the NE, reaching the Atlantic coast of Argentina. The erupted material was mainly of lithic origin (∼77 wt%), resulting in a unimodal total grain size distribution (TGSD) dominated by coarse ash (77 wt%), with Mdϕ of 2.7 and σϕ of 2.4. Lapilli clasts (>2 mm) dominate the proximal deposit within ~20 km of the vent, while coarse (63 μm–2 mm) and fine ash (<63 μm) sedimented as far as 800 km from vent, generating mostly poly-modal grain size distributions across the entire deposit. Given that most of the mass is sedimented in proximal areas, results show that possible contributions of later explosive events to the thickness of the distal deposit where layers are less distinguishable (>400 km) do not significantly affect the determination of the TGSD. In contrast, gaps in data sampling in the medial deposit (in particular the gap between 50 and 350 km from vent that coincides with shifts in sedimentation regimes) have large impacts on estimates of TGSD. Particle number distribution for this deposit is characterized by a high power-law exponent (3.0) following a trend very similar to the vesicle size distribution in the juvenile pyroclasts. Although this could be taken to indicate a bubble-driven fragmentation process, we suggest that fragmentation was more likely the result of a shear-driven process because of the predominance of non-vesicular products (lithics and obsidians) and the large fraction of coarse ash in the TGSD.
KeywordsLong lasting explosive eruptions Tephra fall deposit Total grain size distribution Magmatic fragmentation
Sebastien Biass is thanked for the implementation of the Voronoi tessellation script to describe the weight of individual polygons (https://vhub.org/resources/329). We thank Raffaello Cioni, Danilo M. Palladino and the Associate Editor (Jacopo Taddeucci) for their comments and suggestions that helped greatly to improve the manuscript.
- Biass S, Bonadonna C (2014) TOTGS: total grainsize distribution of tephra fallout. https://vhub.org/resources/3297.
- Bonadonna C, Genco R, Gouhier M, Pistolesi M, Cioni R, Alfano F, Hoskuldsson A, Ripepe M (2011) Tephra sedimentation during the 2010 Eyjafjallajkull eruption (Iceland) from deposit, radar, and satellite observations. J Geophys Res Solid Earth 116, B12202. doi: 10.1029/2011JB008462 CrossRefGoogle Scholar
- Bonadonna C, Cioni R, Pistolesi M, Connor C, Scollo S, Pioli L, Rosi M (2013) Determination of the largest clast sizes of tephra deposits for the characterization of explosive eruptions: a study of the IAVCEI commission on tephra hazard modelling. Bull Volcanol 75:1–15. doi: 10.1007/s00445-012-0680-3 Google Scholar
- Cas RAF, Wright JV (1988) Volcanic successions: modern and ancient. Allen and Unwin, London. doi: 10.1007/978-94-009-3167-1
- Cashman KV, Mangan MT (1994) Physical aspects of magmatic degassing; II, constraints on vesiculation processes from textural studies of eruptive products. Rev Min Geochem 30:447–478Google Scholar
- Costantini L, Houghton BF, Bonadonna C (2010) Constraints on eruption dynamics of basaltic explosive activity derived from chemical and microtextural study: the example of the Fontana Lapilli Plinian eruption, Nicaragua. J Volcanol Geotherm Res 189:207–224. doi: 10.1016/j.jvolgeores.2009.11.008 CrossRefGoogle Scholar
- Inman D (1952) Measures for describing the size distribution of sediments. J Sediment Petrol 125–145. doi: 10.1306/D42694DB-2B26-11D7-8648000102C1865D
- Mastin LG, Guffanti M, Servranckx R, Webley P, Barsotti S, Dean K, Durant AJ, Ewert JW, Neri A, Rose WI, Schneider D, Siebert L, Stunder B, Swanson G, Tupper A, Volentik ACM, Waythomas CF (2009) A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions. J Volcanol Geotherm Res 186:10–21. doi: 10.1016/j.jvolgeores.2009.01.008 CrossRefGoogle Scholar
- Volentik ACM, Bonadonna C, Connor CB, Connor L, Rosi M (2010) Modeling tephra dispersal in absence of wind: insights from the climactic phase of the 2450BP Plinian eruption of Pululagua Volcano (Ecuador). J Volcanol Geotherm Res 193:117–136. doi: 10.1016/j.jvolgeores.2010.03.011 CrossRefGoogle Scholar