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SUMMARY:Volcanic fissure localisation and lava delta formation: Modelling 
 of volcanic flows undergoing rheological evolution - Jesse Taylor-West (Br
 istol)
DTSTART:20250317T130000Z
DTEND:20250317T140000Z
UID:TALK226699@talks.cam.ac.uk
CONTACT:Kasia Warburton
DESCRIPTION:In this talk\, I will present two volcanologically motivated m
 odelling problems.  In the first\, I will detail how thermoviscous localis
 ation of volcanic eruptions is influenced by the irregular geometry of nat
 ural volcanic fissures. Fissure eruptions typically start with the opening
  of a linear fissure that erupts along its entire length\, following which
  activity localises to one or more isolated vents within a few hours or da
 ys. Previous work has proposed that localisation can arise through a therm
 oviscous fingering instability driven by the strongly temperature dependen
 t viscosity of the rising magma. I will show that\, even for relatively mo
 dest variations of the fissure width\, a non-planar geometry supports stro
 ngly localised steady states\, in which the wider parts of the fissure hos
 t faster\, hotter flow\, and the narrower parts of the fissure host slower
 \, cooler flow. This geometrically-driven localisation differs from the sp
 ontaneous thermoviscous fingering localisation observed in planar geometri
 es\, and is potentially more potent for parameter values relevant to volca
 nic fissures.\n\nThe second problem concerns lava delta formation. A lava 
 delta arises when a volcanic lava flow enters a body of water\, extending 
 the pre-eruption shoreline via the creation of new\, relatively flat land.
  A combination of cooling induced rheological changes and the reduction in
  gravitational driving forces controls the morphology and evolution of the
  delta. I will present shallow-layer continuum models for this process\, h
 ighlighting how different modes of delta formation manifest in different l
 ate-time behaviours. In particular\, I will derive a steady state shorelin
 e extent when the delta formation is driven only by buoyancy forces\, and 
 late time similarity solutions for the evolution of the shoreline when the
  viscous lava fragments and forms `hyaloclastic' debris on contact with th
 e water.
LOCATION:MR3\, CMS
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