Real-time tephra-fallout accumulation rates and grain-size distributions using ASHER (ASH collector and sizER) disdrometers

Marchetti, Emanuele; Poggi, Pasquale; Donne, Dario Delle; Pistolesi, Marco; Bonadonna, Costanza; Bagheri, Gholamhossein; Pollastri, Stefano; Thivet, Simon; Gheri, Duccio; Gurioli, Lucia; Harris, Andrew; Hoskuldsoon, Armann; Ripepe, Maurizio

doi:10.1016/j.jvolgeores.2022.107611

Cited by 4 publications

(3 citation statements)

References 41 publications

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“…The fact that bimodal fallout deposits, such as the one at Llaima (Figure 8), are relatively rare suggests effective particle size segregation occurs near the vent in most cases. On the other hand, hindered settling accounts for reduced particle settling velocity, otherwise explained by non spherical particle shape or the presence of wind (Marchetti et al., 2022). In a broader context, hindered settling is likely to occur in various types of geophysical flows containing particles with Stokes number ≫1, and our experiments suggest that this mechanism can operate at concentrations as low as ∼1 vol.%, which may be surprising.…”

Section: Discussionmentioning

confidence: 99%

“…Instead, if the particles are not suspended, they settle to form a deposit or a dense basal flow controlled by particle‐particle interactions. Experimental and numerical studies revealed that the particle settling velocity may increase (Dey et al., 2019; Wang & Maxey, 1993) or decrease (Dey et al., 2019; Fornari et al., 2016; Nielsen, 1993) depending on the degree of turbulence, and it can be lower (Marchetti et al., 2022) or higher (Del Bello et al., 2017) than predicted theoretically for a single particle depending on the particle size, shape, and concentration. Actual particle settling velocities different from theoretical velocities used in models may be a cause of discrepancies between observed and simulated volcanic fall deposits (Tadini et al., 2020, 2022) and this issue is critical in the context of hazard assessment.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Measurement of Enhanced and Hindered Particle Settling in Turbulent Gas‐Particle Suspensions, and Geophysical Implications

et al. 2023

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The dynamics of geophysical dilute turbulent gas‐particles mixtures depends to a large extent on particle concentration, which in turn depends predominantly on the particle settling velocity. We experimentally investigate air‐particle mixtures contained in a vertical pipe in which the velocity of an ascending air flux matches the settling velocity of glass particles. To obtain local particle concentrations in these mixtures, we use acoustic probing and air pressure measurements and show that these independent techniques yield similar results for a range of particle sizes and particle concentrations. Moreover, we find that in suspensions of small particles (78 μm) the settling velocity increases with the local particle concentration due to the formation of particle clusters. These clusters settle with a velocity that is four times faster than the terminal settling velocity of single particles, and they double settling speeds of the suspensions. In contrast, in suspensions of larger particles (467 μm) the settling velocity decreases with increasing particle concentration. Although particle clusters are still present in this case, the settling velocity is decreased by 30%, which is captured by a hindered settling model. These results suggest an interplay between hindered settling and cluster‐induced enhanced settling, which in our experiments occur respectively at Stokes number O(100) and O(1). We discuss implications for volcanic plumes and pyroclastic currents. Our study suggests that clustering and related enhanced or hindered particle settling velocities should be considered in models of volcanic phenomena and that drag law corrections are needed for reliable predictions and hazard assessment.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Measurement of Enhanced and Hindered Particle Settling in Turbulent Gas‐Particle Suspensions, and Geophysical Implications

et al. 2023

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“…Continuous processing and automation of astrometry data collected by the Gemini Observatory on Mauna Kea (Figure 1) would be helpful for quantifying plume heights. The development and deployment of an automated ash sampling array (Marchetti et al., 2022; Shimano et al., 2013) could provide a continuous record of tephra fall. Time‐constrained tephra records would inform ongoing ash dispersal modeling, provide context for radar and satellite analysis and yield a valuable tephra‐sample data set for petrology and ash morphology analyses.…”

Section: Discussionmentioning

confidence: 99%

Dynamics of the December 2020 Ash‐Poor Plume Formed by Lava‐Water Interaction at the Summit of Kīlauea Volcano, Hawaiʻi

Cahalan

Mastin

Eaton

et al. 2023

Geochem Geophys Geosyst

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The appearance of a water lake in Kīlauea's Halemaʻumaʻu Crater (Figure 1) in mid-July 2019 reawakened concerns of violent lava-water interaction when eruptive activity returned to the volcano's summit (Nadeau et al., 2020).Although Kīlauea is best known for its effusive volcanism, evidence from tephra deposits and native Hawaiian oral traditions indicates that violent lava-water interactions have occurred in Kīlauea's past (

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Dynamics, Monitoring, and Forecasting of Tephra in the Atmosphere

Pardini,

Barsotti,

Bonadonna

et al. 2024

Reviews of Geophysics

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Explosive volcanic eruptions inject hot mixtures of solid particles (tephra) and gasses into the atmosphere. Entraining ambient air, these mixtures can form plumes rising tens of kilometers until they spread laterally, forming umbrella clouds. While the largest clasts tend to settle in proximity to the volcano, the smallest fragments, commonly referred to as ash (≤2 mm in diameter), can be transported over long distances, forming volcanic clouds. Tephra plumes and clouds pose significant hazards to human society, affecting infrastructure, and human health through deposition on the ground or airborne suspension at low altitudes. Additionally, volcanic clouds are a threat to aviation, during both high‐risk actions such as take‐off and landing and at standard cruising altitudes. The ability to monitor and forecast tephra plumes and clouds is fundamental to mitigate the hazard associated with explosive eruptions. To that end, various monitoring techniques, ranging from ground‐based instruments to sensors on‐board satellites, and forecasting strategies, based on running numerical models to track the position of volcanic clouds, are efficiently employed. However, some limitations still exist, mainly due to the high unpredictability and variability of explosive eruptions, as well as the multiphase and complex nature of volcanic plumes. In the next decades, advances in monitoring and computational capabilities are expected to address these limitations and significantly improve the mitigation of the risk associated with tephra plumes and clouds.

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Real-time tephra-fallout accumulation rates and grain-size distributions using ASHER (ASH collector and sizER) disdrometers

Cited by 4 publications

References 41 publications

Experimental Measurement of Enhanced and Hindered Particle Settling in Turbulent Gas‐Particle Suspensions, and Geophysical Implications

Experimental Measurement of Enhanced and Hindered Particle Settling in Turbulent Gas‐Particle Suspensions, and Geophysical Implications

Dynamics of the December 2020 Ash‐Poor Plume Formed by Lava‐Water Interaction at the Summit of Kīlauea Volcano, Hawaiʻi

Dynamics, Monitoring, and Forecasting of Tephra in the Atmosphere

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