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Lava effusion in mountainous terrain generates flow backup and increased inundation

Annie Borch1 , James K. Russell1, Thomas Jones2

  • Affiliations: 1Earth, Ocean, and Atmospheric Sciences Department, University of British Columbia, Vancouver, Canada. 2Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom. 

  • Presentation type: Talk

  • Presentation time: Monday 16:15 - 16:30, Room R380

  • Programme No: 3.15.3

  • Theme 3 > Session 15

Abstract

Many volcanic eruptions occur in high relief terrains featuring narrow valleys, sharp turns, and changes in valley width. In these mountainous landscapes, constrictions in width impact the flow and emplacement of effusive eruptions, with such impacts including lava back-up at the point of constriction. Here, we use analogue materials (golden syrup, glycerol) to model lava emplacement in channels that feature significant changes in their width. We measure the impact of the constriction on the excess fluid inundation (i.e. the excess volume and flow thickness) for a range of volumetric fluxes, channel slopes, and fluid viscosities. Our results indicate that fluid/lava backup can be achieved in at least three ways. (i) Interaction with abrupt changes in the channel wall geometry pose as obstacles and barriers to flow and cause local backup. (ii) To achieve a volumetric flow balance between the upstream flow and the downstream flow within the channel constriction, an increase in flow thickness is required. (iii) When choked flow is achieved within the constriction, increases in upstream flow thickness can be generated. For each of these processes we assess the environmental conditions (e.g., degree of channel confinement) and lava properties (e.g., viscosity) under which they operate for basaltic systems. Future work will apply this framework to basaltic lava flows in representative topography. Our results will aid in interpreting the emplacement history of valley-filling lava flows and the resulting impacts on valley drainage geomorphology, and will support forecasting of lava flow hazards in areas of mountainous terrain.