Mapping and measuring lava volumes from 2002 to 2009 at El Reventador Volcano, Ecuador, from field measurements and satellite remote sensing

Estimates of lava volume, and thus effusion rate, are critical for assessing volcanic hazard and are a priority for volcano observatories with responsibility for monitoring. The choice of specific methods used to approximate lava volume depends on both volcanological and practical considerations; in particular, whether field measurements are possible and how often they can be repeated. Volcán El Reventador (Ecuador) is inaccessible, and field measurements can only be made infrequently at a few locations in its caldera. We present both planimetric field and topographic satellite radar-based measurements of lava flow thicknesses and volumes for activity at El Reventador between 2002 and 2009. Lava volumes estimates range from 75 ± 24 × 106 m3 (based on field measurements of flow thickness) to 90 ± 37 × 106 m3 (from satellite radar retrieval of flow thickness), corresponding to time-averaged effusion rates of 9 ± 4 m3/s and 7 ± 2 m3/s, respectively. Detailed flow mapping from aerial imagery demonstrate that lava effusion rate was at its peak at the start of each eruption phase and decreased over time. Measurements of lava thickness made from a small set of Synthetic Aperture Radar (SAR) interferograms allowed the retrieval of the shape of the compound lava flow field and show that in 2009 it was subsiding by up to 6 cm/year. Satellite radar measurements thus have the potential to be a valuable supplement to ground-based monitoring at El Reventador and other inaccessible volcanoes.