The historic magmatic-hydrothermal eruption of the Breccia di Commenda, Vulcano, Italy

Abstract

This is an author version of the contribution published on:Questa è la versione dell 'autore dell'opera: Gurioli, Zanella,Gioncada, Sbrana,Bulletin of Volcanology, 74, 1235-1254, DOI:10.1007. The definitive version is available at: La versione definitiva è disponibile alla URL: AbstractThe historic Breccia di Commenda (BC) explosive eruption of Vulcano (Aeolian Islands, Italy) opened with a phase that generated a grey fine ash layer dispersed to the northwest (Phase 1). The eruption continued with a dilute pyroclastic density current (PDC) that was dispersed to the east, followed by the emplacement of radially distributed, topographically controlled PDC deposits (Phase 2). The last phase of the eruption produced a sequence of accretionary lapilli and grey fine ash dispersed toward the southeast (Phase 3). The most impressive feature of the BC is its high lithic/juvenile clast ratio and the yellow color of the deposits of Phase 2. Lithic fragments are mainly hydrothermally altered rocks, in the silicic and advanced argillic facies. Juvenile fragments, ranging from 20% to 40% by volume, are mainly confined to the ash component of the deposits and comprise rhyolitic to trachyandesite, poorly to non-vesicular fragments. The fine ash fraction of the deposits is richer in S, Cu, Zn, Pb, and As than the BC juvenile lapilli and bombs, and also the juvenile 3 components of other La Fossa units, suggesting that the BC formed in the presence of an anomalously high amount of S and metals. Sulfur and metals may have been carried as aerosols by chloride-and sulfate-bearing micro-crystals, derived from the condensation of magmatic gas in the eruptive cloud. The high content of hydrothermally altered lithic clasts in the deposits suggests that explosions involved the fluid-saturated hydrothermally altered rocks residing in the conduit zone. However, the presence of a juvenile component in the deposits supports the idea that this explosion may have been triggered by the ascent of new magma.We categorize this eruption as magmatic-hydrothermal, to emphasize that in this type of phreatomagmatic eruption the external water was an active hydrothermal system.Rock magnetic temperatures of non-altered lava lithic fragments indicate a uniform deposit temperature for the PDC deposits of between 200 and 260 °C, with a maximum at 280 °C.These homogeneous, relatively low temperatures are consistent with the idea that the Phase 2 explosions involved the expansion of abundant steam from the flashing of the hydrothermal system. In addition, recent paleomagnetic dating of the BC provides an age of between 1000and 1200 AD, younger than that reported in the previously published data, suggesting that previous interpretations and the recent history of La Fossa and Mt. Pilato require reevaluation.

Sorption and thermodynamic properties of wood of Pinus canariensis C. Sm. ex DC. buried in volcanic ash during eruption

“…Therefore, the low EMC content obtained in the wood buried under ash compared to recently felled wood or the EMC obtained in other samples of buried wood (Esteban et al 2009(Esteban et al , 2010 shows the influence of the high temperatures, with an effect similar to the findings in some studies of thermally treated wood (Stamm and 1937;Hill 2006;Murata et al 2013;Olek et al 2013;Rautkari et al 2013Rautkari et al , 2014Willems et al 2013). Studies on temperatures of pyroclastic materials reported that it is usual for temperatures to reach 200-300 °C (Voight and Davis 2000;Freundt 2003;Gurioli et al 2012;Major et al 2013). The values of the minimum of the derivative of the EMC in relation to the RH correspond to the points where multilayer sorption starts to predominate over monolayer sorption (Fig.…”

Mapping the susceptibility of rain-triggered lahars at Vulcano island (Italy) combining field characterization, geotechnical analysis, and numerical modelling

“…PAL-A and PAL-C in Di Traglia et al, 2013), pumiceous tephra fallout layers of rhyolitic (PAL-B) and trachytic composition (PAL-D), several lava flows intercalated in the sequence (e.g. the rhyolitic obsidian of Commenda and the trachytic lava flows of Palizzi, Campo Sportivo, and Punte Nere), and, finally, several ash layers and widely dispersed PDC deposits (CEU) associated with the hydrothermal eruption of the Breccia di Commenda eruptive unit (Gurioli et al, 2012;Rosi et al, 2018), which closes the PCEC. The GCEC includes the recent products of the Pietre Cotte eruptive unit (ash and lapilli layers from Vulcanian activity), rhyolitic pumiceous tephra fallout layers, and the rhyolitic 1739 CE Pietre Cotte lava flow.…”

From sink to volcanic source: Unravelling missing terrestrial eruption records by characterization and high‐resolution chronology of lacustrine volcanic density flow deposits, Lake Inawashiro‐ko, Fukushima, Japan

“…Thus, several lines of evidence in the Bm and Bs characteristics, such as the clay‐rich nature, the presence of juvenile material, and incorporation of epithermal and low grade alteration parts of the edifice of Bandai volcano, point to the high possibility of a magmatic hydrothermal eruption (Fig. B: as magma injection into a pre‐existing convecting hydrothermal system that finally triggers an eruption: Browne & Lawless, ; Gurioli et al ., ) and an eruption‐related partial collapse at the volcano rather than a full magmatic eruption.…”

“…In this case, the bulk of the energy responsible for the eruption is derived from the hydrothermal system itself, but the magmatic input has an essential triggering role” (Browne & Lawless, ). This phenomenon is important because the presence of newly ascending magma, contributing to the eruption, has been sometimes overlooked by categorization as a pure phreatic eruption (Gurioli et al ., ). Such volcaniclastic layers by phreatic and magmatic–hydrothermal eruptions in stratigraphic records may not be recognized as the products of individual eruptions and eruption‐associated events.…”