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  • Articles  (2)
  • 1
    Publication Date: 2011-10-01
    Description: Explosive activity and lava dome collapse at stratovolcanoes can lead to pyroclastic density currents (PDCs; mixtures of volcanic gas, air, and volcanic particles) that produce complex deposits and pose a hazard to surrounding populations. Two-dimensional computer simulations of dilute PDCs (characterized by a turbulent suspended load and deposition through a bed load) show that PDC transport, deposition, and hazard potential are sensitive to the shape of the volcano slope (profile) down which they flow. We focus on three generic volcano profiles: straight, concave-upward, and convex-upward. Dilute PDCs that flow down a constant slope gradually decelerate over the simulated run-out distance (5 km in the horizontal direction) due to a combination of sedimentation, which reduces the density of the PDC, and mixing with the atmosphere. However, dilute PDCs down a concave-upward slope accelerate high on the volcano flanks and have less sedimentation until they begin to decelerate over the shallow lower slopes. A convex-upward slope causes dilute PDCs to lose relatively more of their pyroclast load on the upper slopes of a volcano, and although they accelerate as they reach the lower, steeper slopes, the acceleration is reduced because of the upstream loss of pyroclasts (lower density contrast with the atmosphere). Dynamic pressure, a measure of the damage that can be caused by PDCs, reflects these complex relations.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 2
    Publication Date: 2022-05-24
    Description: Pyroclastic currents are described as gravity currents, and the classic conceptual model gives a first-order importance to the density of such currents. This directs quantitative models to assume specific flow structures (shallow water or equilib rium turbulent boundary layer), which may apply to restricted volcanic areas inde pendently of source dynamics or may correspond to source dynamics separate from topographic interaction. The recent introduction of two end-members of pyroclastic currents, inertial and forced, is further developed here, leading to a global conceptual model in which source dynamics and topographic interaction are both taken into account. The concept of energy facies is defined here as the ensemble of the first order indicators of pyroclastic currents (topological aspect ratio, competence ratio and emplacement temperature) that are proxies of the energy of such currents. Nine energy facies are introduced with general applicability and with the goal to globally characterize pyroclastic currents from vent to deposit.
    Description: Published
    Description: 1-11
    Description: 4V. Processi pre-eruttivi
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Keywords: Energy facies ; pyroclastic currents
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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