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The Young Doña Juana central vent within the Doña Juana Volcanic Complex, in SW Colombia, is an excellent example for dome-dominated, tropical arc volcanoes. Here, fast rates of weathering and erosion in the tropical climate and active tectonics across the North-Andean block strongly fragment the geological record. We focused on the geology of the Young Doña Juana central summit vent zone, which is the best exposed, the only one showing pyroclastic besides effusive activity, and has affected the inhabited territory to the west of the volcano in the XXth century. We integrate new geological mapping at a 1:5000 scale with radiocarbon ages, sedimentology analysis, and historical chronicles to reconstruct the Late Holocene evolution of this young lava-dome complex.Descriptions of new outcrops at 93 locations allowed defining lithostratigraphic units. The lithofacies associations and sedimentological analyses indicate that pyroclastic-density-currents were predominant, generated by dome collapse leading to block-and-ash flows, or by pyroclastic fountain/column-collapse producing lithic or pumice-bearing deposits. Lahars were also common. The PDCs were ~4 to 10 ´ 106 m3 in volume and deposited under granular-flow or fluid escape-dominated depositional regimes at high clast concentrations, and affecting currently inhabited areas. Hence, lava-dome growth and collapse phases, as well as lava dome/plug disruption through Vulcanian and possibly sub-Plinian eruptions dominated over the Late Holocene, with at least three main explosive eruption episodes since ~5 cal ky. We pose a new baseline of knowledge on a potentially active volcanic center of the Northern Andes experiencing explosive activity during the XX century., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Dry granular flows are gravity-driven mixtures of discrete polydisperse grains that belong to the family of multiphase flows, which are involved in a wide range of volcanological (e.g. pyroclastic density currents, block and ash flows, debris avalanches, etc.) and industrial (pneumatic transport, fluidized beds, etc.) applications. If they are non-cohesive, their status is determined by the interaction of particle-particle and particle-wall frictional forces, external boundaries and gravity. The understanding of the transport mechanisms of granular materials is of paramount importance for the characterization of volcanic granular flows and for hazard assessments associated with these flows. In order to investigate the dynamics of these kinds of flows, we simulated large-scale experiments on bi-disperse granular flows by means of the Two-Fluid Model approach using the software MFIX, with an emphasis on the polydispersity effect and on the grain size ratio (ratio of larger particles diameters to smaller ones) on the flow behaviour. Specifically, we first investigated the forces ruling the mixing and segregation processes active in granular flows; then we analysed the effect of these processes on the flow organization and on the velocity of the granular flow front. Finally, we replicated the large-scale experiments by focusing on the effects of the different grains size ratios on the granular flow dynamics. Simulations of the bi-disperse granular flows demonstrated an enhanced capability to replicate segregation dynamics active in real granular flows, thus highlighting the grain size ratio role on granular flows behaviour., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The variability of eruptive dynamics in an active volcano is related to several factors, also including the magma input rate from depth and the influence of volcano-tectonic events. Such elements are also able to impact on the trigger mechanisms of eruptions which, in an extreme synthesis, could be related to bottom-to-top and top-to-bottom dynamics in function of the area of the feeding system whose modification is able to activate magma ascent.A new detailed and stratigraphically-constrained study of the Petrazza eruptive cycle of the PaleoStromboli I eruptive epoch (85-75 ka) has highlighted a period of unusual high-energetic explosive eruptions, likely to be associated to (partially/totally) closed conduit dynamics. A multi-disciplinary approach embracing whole rock, mineral compositional and textural studies and geobarometry confirm initial conditions of closed conduit system, allowing an extensive differentiation of magmas and the crystallization of amphibole. High-intensity explosions are then triggered by the input of hotter and more mafic magma, which partially and gradually substituted the residing one in the intermediate/shallow portions of the feeding system, leading to “classical” open-conduit eruptive dynamics. At the end of the sequence an event of extreme decompression of the magma feeding system, here related to a structural collapse of the volcanic edifice whose deposits are still visible within the sequence, triggered a rapid magma ascent at water undersaturated conditions and an high-energetic explosive eruption, assumed as the larger for the Stromboli volcanic system.

To the present date, no phreatic eruption has been successfully forecasted, as this kind of eruption lacks clear and univocal precursory signals. Understanding how deep magmatic gas and heat fluxes interact with groundwater systems and prime phreatic eruptions is thus of pivotal importance. Here we present an overview of how the modeling of such systems can be addressed from a physical perspective.Volcanic heat and gases (mainly H2O and CO2) released from magmatic intrusions can reach a shallow aquifer hosted in a porous medium, leading to the formation of a multicomponent (H2O and CO2) two-phase system. The formation of a hydrothermal sealing leads to the build-up of an overpressure. The stresses generated by this overpressure might overcome the resistance of the host rock thus leading to the development of cracks (at depth) or leading to an eruption (closer to the surface).The dynamic evolution of the two-phase fluids can be described by the multiphase multicomponent transport model and some energy-based phase equilibrium criteria (e.g., minimization of the Gibbs free energy of the system). This system needs then to be coupled with a thermo-poro-elastic model of the host rock for modeling the stress and deformation fields in order to understand the conditions leading to an eruption. Numerical integration is a key tool for solving the problem. Explorative tests are running using the high-performance multiphysics code ALYA.The development of such models are a key step in understanding phreatic eruptions and will eventually help developing the forecasting of such events., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Five cores from the southern Tyrrhenian and Ionian seas were studied for their tephra and cryptotephra content in the 4.4–2.0 ka time interval. The chronological framework for each core was obtained by accelerator mass spectrometry14C dating, the occurrence of distinct marker tephra and stratigraphic correlation with adjacent records. Tephrochronology allowed us to correlate the analyzed deposits with tephra markers associated with Somma‐Vesuvius (79ad), Ischia Island (Cretaio), Mt Etna (FG, FL and FS) and Campi Flegrei (Astroni‐Agnano Monte Spina) events. For the first time in the marine setting, a large single glass data set is provided for the Late Holocene Etnean marker beds including the FS tephra (ca. 4.3 ka). Moreover, unknown deposits from Lipari (ca. 2.2–2.0 ka) and Vulcano (3.6–3.3 ka) are also recognized at more distal sites than previously reported. These results contribute to improve the high‐resolution tephrostratigraphic framework of the central Mediterranean Sea. They also provide new insights into the chemical composition and dispersal pattern of tephras that can be used as inter‐archive tools for regional and ‘local’ stratigraphic correlations and for addressing paleoclimate research.