Insights into the dynamics and evolution of the 2010 Eyjafjallajokull summit eruption (Iceland) provided by volcanic ash textures

• Published in: Earth and Planetary Science Letters
• Main Authors: R. Cioni, M. Pistolesi, A. Bertagnini, C. Bonadonna, A. Hoskuldsson, B. Scateni
• Other Authors: Cioni, R., Pistolesi, M., Bertagnini, A., Bonadonna, C., Hoskuldsson, A., Scateni, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: explosive volcanism; Eyjafjallajökull; Eyjafjallajokull; Iceland
• Online Access: http://hdl.handle.net/11568/903123; https://doi.org/10.1016/j.epsl.2014.02.051

Recent observations all around the world have shown a large range of explosive activity dominated by prolonged, low- to mid-intensity emission of ash, and characterized by a large variability of magma composition and style of magma degassing, fragmentation and ash dispersal. The April-May 2010 eruption of the Eyjafjallajökull volcano (Iceland) represents one example of this type of activity, as it was characterized by a continuous generation of tephra injected into the atmosphere that affected various economic sectors in Iceland and caused a world-wide interruption of air traffic. This eruption is progressively becoming a benchmark for the interpretation and discussion of the processes that govern the dynamics of ash-dominated eruptions, also representing a unique opportunity for direct ash particle investigation. In this paper, selected ash samples from all phases of the eruption were studied in order to characterize: 1) the morphology, composition and texture of ash fragments; 2) the variability of the products of each phase of the eruption; 3) the progressive changes of these features with time. The large morphological and textural variability of the ash fragments throughout the eruption is unrelated to any important compositional change, and it reflects changes in eruption and magma dynamics and in the processes of magma fragmentation during the different phases of the eruption. The variability and the changes during the eruption observed in the textural and morphological features of the juvenile material record the complex dynamics of the eruption, suggesting that primary magma degassing dominated and modulated the dynamics of the entire eruption, while hydromagmatic fragmentation was particularly effective only in the very initial phase. As a consequence, the large production of fine-grained ash that characterized the eruption cannot be related to processes of magma-water interaction, and mechanisms of magma fragmentation of a high-fragility melt by degassing and ash recycling must be invoked.