20.500.12556/DiRROS-27491 The role of crystal-bubble interactions, outgassing and magma composition in the ascent dynamics of alkaline magmas implications for eruptions at Vesuvius Intermediate to evolved alkaline magmas (phono-tephritic, tephri-phonolitic and phonolitic) exhibit a wide range in eruptive style and have produced some of the most catastrophic eruptions in human history, such as the 79 AD Plinian eruption of Vesuvius (Italy). However, eruptive dynamics are driven by complex, non-linear conduit processes during magma ascent, requiring a holistic approach to investigate their influence on explo- sivity. This study integrates synchrotron radiation X-ray computed microtomography (SRμCT) with a 1D steady- state conduit model, to investigate how crystal-bubble interactions, pre-eruptive conditions, outgassing, and magma composition affect eruptive style at alkaline volcanic systems, using Vesuvius as a case study. We analyse pyroclasts from the 79 AD Plinian and 1944 lava-fountaining eruptions using SRμCT. Our SRμCT results reveal that heterogeneous bubble nucleation can be promoted further by leucite crystals, contributing to the high bubble number densities (>10⁴ mm⁻³) observed in Plinian products. Despite high bubble connectivity, low throat-pore size ratios (the ratio between the radii of the throat and connected vesicles) and elevated tortuosity restrict gas–melt separation during fast magma ascent, promoting fragmentation. Numerical simulations reveal tephri-phonolitic and phonolitic magmas are prone to fragmentation across diverse conditions, producing highly explosive eruptions. Only relatively high temperatures (>1050 ◦ C) and low bubble number densities (102 to 103 mm-3) can promote lava flow and fountaining activity. Instead, phono-tephritic magmas exhibit highly explosive eruptions at considerably lower temperatures (<950 ◦C). Temperature controls magma viscosity, influencing the ascent rate and the outgassing efficiency, which, in turn, affects conduit dynamics and the eruptive behaviour. Our findings highlight that for alkaline systems, the parameter space which is conducive to highly explosive eruptions expands as the magma composition evolves and its viscosity increases. These insights enhance our understanding of eruption mechanisms, providing critical insights for assessing volcanic hazard and emergency planning at alkaline volcanic systems. outgassing conduit dynamics eruptive style crystal-bubble interaction alkaline magmas vesuvius izpuščanje plinov dinamika vodovoda eruptivni slog interakcija med kristali in mehurčki alkalne magme vezuv true false true Elsevier Angleški jezik Slovenski jezik Neznano 2026-02-10 07:41:50 2026-02-10 07:45:08 2026-02-11 04:01:06 0000-00-00 00:00:00 2026 0 0 str. 1-15 [article no.] 119771 Vol. 675 Feb. 2026 0000-00-00 PostprintKoncna Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-12-08 2027-12-08 55 1385-013X 10.1016/j.epsl.2025.119771 261144323 https://doi.org/10.1016/j.epsl.2025.119771 0 95a02bbe-064b-11f1-88c7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=40241 RAZ_Arzilli_Fabio_2026.pdf RAZ_Arzilli_Fabio_2026.pdf 1 E76627DD013C4EFBDBE087B5E5EA99DF 60ece26b08d6681486f7e63942ff9c43a7607380636a2bd4201e36c8a177a1df ff81ff5c-064b-11f1-88c7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=40242 Zavod za gradbeništvo Slovenije 0 0 0