Skip to content

High-Temperature Deformation and Failure of Welded Volcaniclastic Deposits: Implications for Deposit-Derived Pyroclastic Density Currents

Teresa Oreade Grillo1 , Sara Calandra2, Teresa Salvatici2, Alessia Falasconi3, Alessandro Frontoni4, Gianmarco Buono3, Lucia Pappalardo3, Claudia Romano1, Alba Patrizia Santo2, Guido Giordano1, Emanuele Intrieri2, Alessandro Vona1, Federico Di Traglia3,2

  • Affiliations: 1Dipartimento di Scienze, Università degli Studi "Roma Tre", Largo San Leonardo Murialdo 1, 00146, Roma (Italia); 2Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via La Pira 4, 50121, Firenze (Italia); 3Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Via Diocleziano 328, 80124, Napoli (Italia); 4Consiglio Nazionale delle Ricerche -- Piazzale Aldo Moro 7, 00185 Roma (Italia)

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 185

  • Programme No: 3.9.18

  • Theme 3 > Session 9

Abstract

Failure of glowing volcaniclastic rocks can trigger hot rock avalanches, also known as deposit-derived pyroclastic density currents (PDCs). These phenomena are common in volcanoes with low to moderate eruptive activity, where steep slopes and proximal material accumulation near vents predispose volcanic flanks to instability. To investigate this process, we studied the welded deposits from the fire-fountaining activity of the1944 eruption of Mt. Vesuvius, which produced deposit-derived PDCs along the volcano's slopes. We combined field and laboratory analyses, as physico-mechanical analysis (porosity and sclerometer measurements, point load tests, uniaxial compression tests), and petrographic studies to examine the predisposing factors like welding degree, porosity, and crystallinity. In particular, high-temperature rheological experiments were conducted using the Volcanological In-situ Deformation Instrument (VIDI), capable of uniaxial deformation of volcanic material up to 1100°C. Tests were performed on partially remelted samples with varying welding degrees, including coherent lava blocks and partially welded pyroclasts. The experiments revealed the rheological response of multiphase materials (melt, crystals, and pores) The experiments explored the rheological response of multiphase materials (melt, crystals and pores) in regimes ranging from homogeneous to inhomogeneous deformation (viscous and brittle shear localisation). Flow curves defined material strength at elevated temperatures, while weakening due to shear band formation and ductile deformation was quantified. X-ray microtomography imaging before and after deformation provided insights into textural and porosity changes, revealing microstructural evolution during failure. These findings clarify the mechanical processes behind incandescent volcaniclastic rock failure and deposit-derived PDC generation, enhancing our understanding of volcanic instability dynamics and associated hazards.