From pore-scale processes to volcanic hazards : multiscale modeling of submarine landslides, tsunamis, and lava flows
Volcanic geophysical flows involve physical processes acting over a wide range of spatial and temporal scales, from particle rearrangements and pore-fluid interactions to the propagation of landslides, waves, and lava flows over complex terrain. This talk presents a multiscale numerical approach for investigating these processes, with particular emphasis on volcanic environments in the Canary Islands.
The first part focuses on submerged granular failures and landslide-generated waves. At the pore scale, the initial compaction state controls whether the granular skeleton contracts or dilates during deformation. Loose deposits tend to contract, generating positive excess pore pressure, reducing effective stress, and promoting rapid failure or liquefaction. Dense deposits, in contrast, dilate and generate negative pore pressure, increasing effective stress and shear resistance and favoring slower failure. The discrete element method and multiphase finite volume method are used to investigate how these pore-pressure feedback mechanisms control failure mode, mobility, runout, and wave generation. These models are also used to examine the interaction of submarine granular flows with submerged objects and infrastructure, including impact forces and the respective contributions of grain contacts, pore-pressure effects, and hydrodynamic loading. The modeling is then applied at larger scales using real bathymetry and field observations from volcanic environments.
The second part addresses lava flow dynamics. Numerical simulations are used to investigate how cooling modifies flow dynamics and how interactions with barriers affect velocity, thickness, flow diversion, and accumulation upstream of obstacles. The physical understanding gained from these small-scale simulations is subsequently applied to a real volcanic setting, using the 2021 La Palma eruption as a case study to model lava flow propagation over complex topography. Together, these examples illustrate how detailed numerical models can connect small-scale physical mechanisms to the large-scale evolution of volcanic hazards.
Contact Cyrille Bonamy for more information or to schedule a discussion with the seminar speaker.