Examining rhyolite lava flow dynamics through photo-based 3D reconstructions of the 2011–2012 lava flowfield at Cordón-Caulle, Chile

Abstract

During the 2011-2012 eruption at Cordón-Caulle, Chile, an extensive rhyolitic flowfield was created (in excess of 0.5 km 3 in volume), affording a unique opportunity to characterise rhyolitic lava advance. In 2012 and 2013, we acquired approximately 2500 digital photographs of active flowfronts on the north and east of the flowfield. These images were processed into three-dimensional point clouds using Structure-from-Motion Multi-view Stereo (SfM-MVS) freeware, from which digital elevation models were derived. Sequential elevation models-separated by intervals of three hours, six days, and one year-were used to reconstruct spatial distributions of lava velocity and depth, and estimate rheological parameters. Three-dimensional reconstructions of flowfronts indicate that lateral extension of the rubbly, 'a'ā-like flowfield was accompanied by vertical inflation, which differed both spatially and temporally as a function of the underlying topography and localised supply of lava beneath the cooled upper carapace. Compressive processes also drove the formation of extensive surface ridges across the flowfield. Continued evolution of the flowfield resulted in the development of a compound flowfield morphology fed by iterative emplacement of breakout lobes. The thermal evolution of flow units was modelled using a one-dimensional finite difference method, which indicated prolonged residence of magma above its glass transition across the flowfield. We compare the estimated apparent viscosity (1.21−4.03 × 10 10 Pa.s) of a breakout lobe, based on its advance rate over a known slope, with plausible lava viscosities from published non-Arrhenian temperatureviscosity models and accounting for crystallinity (~50 vol. %). There is an excellent correspondence between viscosity estimates when the lava temperature is taken to be magmatic, despite the breakout being located >3km from the vent, and advancing approximately nine months after vent effusion ceased. This indicates the remarkably effective insulation of the lava flow interior, providing scope for significant evolution of rhyolitic flow fields long after effusive activity has ceased.

MMASTER: Improved ASTER DEMs for Elevation Change Monitoring

“…We generate MMASTER DEMs over the Puyehue-Cordón Caulle volcanic complex, southern Chile, where a voluminous explosive eruption occurred in June 2011. The eruption resulted in a number of substantial topographic changes: (1) the effusion of a massive, 30-45 m-thick rhyolite lava flow that emanated from an effusive vent on the NNW flank of the volcano [27], (2) the shallow emplacement of a laccolithic intrusion that triggered a >200-m bulge of the Earth's surface and (3) the thick deposition of explosive material as a result of pyroclastic flows. In addition, the eastward transport of the eruptive column led to thick ash and tephra deposits [28], which considerably affected the ecosystems of the regions east of the volcano [29], including killing the vegetation due to the toxic ash concentration.…”

Unravelling textural heterogeneity in obsidian: Shear-induced outgassing in the Rocche Rosse flow

“…Magma viscosities on the order of 10 8 to 10 12 Pas (e.g., Farquharson et al, 2015) inhibit bubble growth and contribute to volatile oversaturation in the melt as rhyolitic magma ascends to lower pressures and depths in the conduit (e.g., Sparks, 1978). Solubility calculations show that if magma contained dissolved water in concentrations typical of obsidian lava (0.1-0.4 wt.%) decompression during ascent would result in vesicularities far beyond those inferred for fragmentation (Gonnermann, 2015).…”

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

“…As lava flows cool, they develop a solid crust that interacts with the underlying fluid by imparting shear on the internal lava; flow advance can be inhibited as the crust strengthens (Fink and Fletcher 1978;Fink 1980a;Cashman et al 1999;Blake and Bruno 2000;Griffiths 2000;Lescinsky and Merle 2005;Castruccio et al 2013;Farquharson et al 2015;Magnall et al 2017). Rhyolitic lava crusts are typically stronger, thicker and more rigid than basaltic crusts.…”

“…These processes are all inferred in the Rocche Rosse based on observations made at Cordón Caulle, and the role played by these variable factors may be understated in the reconstruction of other older lava flows. Recent studies (Carn et al 2009;Lara 2009;Castro et al 2013;Schipper et al 2013;Tuffen et al 2013;Bertin et al 2015;Farquharson et al 2015;Magnall et al 2017) of active flows and domes also highlight processes which may not be evident in older flows due to overprinting or lack of exposure.…”

“…Since 2008, real-time observations of active rhyolitic flow and dome emplacement at the Chilean volcanoes of Chaitén (Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013) and Puyehue-Cordón Caulle Schipper et al 2013;Tuffen et al 2013;Bertin et al 2015;Farquharson et al 2015;Magnall et al 2017) have further developed our knowledge of rhyolitic lava emplacement. The Cordón Caulle eruption is an example of a flow that moved away from the vent, while Chaitén was a domeforming eruption.…”