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The effects of lull and peaks in effusion rate on lava flows propagated on slopes: insights from analog experiments

Sean I. Peters 1, Amanda B. Clarke2,3, Erika L. Rader4

  • Affiliations: 1Department of Earth and Climate Sciences, Middlebury College, Middlebury, VT, USA; 2School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA; 3Istituto Nazionale di Geofisica e Vulcanologia -- Sezione di Pisa, Pisa, IT; 4Department of Earth and Spatial Sciences -- University of Idaho, Moscow, ID, USA

  • Presentation type: Talk

  • Presentation time: Tuesday 08:30 - 08:45, Room R380

  • Programme No: 6.5.1

  • Theme 6 > Session 5

Abstract

Lava flows represent a hazard to populations and infrastructure proximal to volcanoes.  Topography is one of the primary external variables that impacts flow emplacement, affecting likely paths.  The confluence of variable effusion rates and topography may produce unique flow behaviors that may improve understanding of lava flow emplacement.  We conducted analog experiments utilizing polyethylene glycol wax to investigate how changes in extrusion rate at the source impact flow propagation on low, medium, and high slopes.  We focused on the following flow emplacement modes:  surface and marginal breakouts, inflation, and tube formation. We performed 72 experiments using 2 different effusion rate patterns to address the following controls on lava flow emplacement:  a lull -- a stepwise decrease in extrusion rate (n = 36) and a peak -- a stepwise increase in extrusion rate (n = 36).  For each condition (lull vs peak), we varied the slope between low (~7°), medium (~16°), and high (~29°).  We controlled for wax and ambient water temperature, extrusion rate, and slope.  Emplacement modes varied by condition, extrusion rate, and slope, with resurfacing independent of all, inflation occurring at low slopes or under low extrusion rates, and tube formation preferred under peak conditions regardless of slope.  Steeper slopes resulted in narrower channelized flows, while flows emplaced on shallower slopes were wider, thicker (in cases of inflation and resurfacing), and displayed more complex morphologies.  Post-emplacement morphologies were modified by drain out especially at steeper slopes, which may not preserve the finer surface textures produced during an eruption.