Aeolian Remobilisation of the 2011-Cordón Caulle Tephra-Fallout Deposit: Example of an Important Process in the Life Cycle of Volcanic Ash

Although volcanic eruptions represent short periods in the whole history of a volcano, the large amount of loose pyroclastic material produced, combined with aeolian processes, can lead to continuous, long-lasting reworking of volcanic products. Driven by wind, these processes significantly influence the geomorphology and prolong the impacts of eruptions on exposed communities and ecosystems. Since such phenomena are of interest to scientists from a range of disciplines (e.g., volcanology, atmospheric and soil sciences), a well-defined, common nomenclature is necessary to optimise the multidisciplinary characterisation of both processes and deposits. We, therefore, first describe ash wind-remobilisation processes and provide definitions for appropriate terms consistent with the World Meteorological Organisation’s (WMO’s) classification of lithometeors. Second, we apply these definitions to investigate aeolian remobilisation of the 2011 Cordón Caulle (Chile) tephra-fallout deposit, which has strongly impacted rural communities in the Argentinian Patagonia steppe. We combine field observations and a physical characterisation of systematically collected ground and airborne material in order to identify the secondary deposits associated with: (i) non-erodible surface roughness elements (e.g., vegetation and rocks) and (ii) pre-existing mounds or similar erodible bedforms. Grainsize analysis shows that wind-remobilised particles have a specific size range, from