Image‐based measurement of flux variation in distal regions of active lava flows

Abstract

[1] Understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes. Here, we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active 'a' a flows in order to investigate distal flow processes at Mount Etna, Sicily. Photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow-fronts. Velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava. Significant variations of the magma flux were observed, and pulses of increased flux arrived within the flow-front region on timescales of several hours. The pulses are believed to be the distal result of more frequent flux changes observed in the vent region. Hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short-period variations in effusion rate. In considering advance processes for the individual flow-fronts, it must be assumed that they were fed by a highly unsteady flux, which was volumetrically at least an order of magnitude lower than that observed near the vent.

Exceptional mobility of an advancing rhyolitic obsidian flow at Cordón Caulle volcano in Chile

“…Photogrammetry and other terrestrial imaging techniques are powerful tools for tracking the morphological evolution of lavas and domes [39][40][41] , and can be used in concert with satellite remote sensing techniques 42 . More recently, construction of 3D models using structure-frommotion (SfM) and multiview-stereo computer vision techniques allows quantitative interpretation of the temporal evolution of lava flow fields and silicic domes [43][44][45] .…”

Morphological complexities and hazards during the emplacement of channel-fed `a`ā lava flow fields: A study of the 2001 lower flow field on Etna

“…However, small-scale changes in effusion rate on timescales of minutes to hours are known to significantly influence flow behaviour and morphology (e.g. Kauahikaua et al 2003;Bailey et al 2006;James et al 2007). Behncke and Neri (2003) and Coltelli et al (2007) calculated time-averaged syn-eruption discharge rates (Harris et al 2007) for the 2,100 m vent on a near-daily basis, using planimetric methods.…”

Point clouds from oblique stereo-imagery: Two outcrop case studies across scales and accessibility

“…Close range: Faxe Quarry Comparison between DEM´s derived by photogrammetry and laser scanning Using terrestrial oblique stereo images for DEM extraction within the geosciences field has previously been applied successfully [Chandler et al, 2002;James et al, 2006;James et al, 2007;Haneberg, 2008;Gessner et al, 2009;Sturzenegger and Stead, 2009] and is as such not a new topic. The results of our experiment, in accordance with previous studies, show that the use of high-resolution handheld digital cameras and photogrammetric methods is a method capable of producing elevation models of geological outcrops with high resolution.…”