Towards a satellite-based approach to measure eruptive volumes at Mt. Etna using Pleiades datasets

Only a few high precision studies of lava and tephra during simultaneous explosive and effusive activity have so far been undertaken. We carried out such measurements by analysis of a unique and homogeneous multi-temporal dataset of high-spatial resolution satellite optical images. Digital Elevation Models (DEMs) and orthophotos (with 1- and 0.5-m-pixel resolutions respectively) were extracted from six specifically tasked Pleiades tri-stereo pairs of Mt. Etna volcano, between 2011 and 2016. During this period, frequent effusive and explosive events formed lava flow fields and built up the new south-east crater pyroclastic cone. The volumes of lava fields and proximal pyroclastic deposits were measured by comparing the Pleiades DEMs with an aerial photogrammetric DEM updated in 2007. The volumes of all distal deposits were estimated using lava and tephra partitioning from the literature for an Etnean lava fountain. The dense rock equivalent volume of lava and tephra, calculated to be 248.4 ± 2.1 × 106 m3 in total, corresponds to an average output rate of 0.98 m3/s over the analysed 8-year period (May 2008–May 2016) and to a multi-event eruption rate of 5.53 m3/s for 520 days of activity. The multi-temporal analysis of high-spatial resolution satellite DEMs, here successfully applied to the well-monitored Etna volcano, demonstrated that the tasking of high-spatial resolution satellite images is crucial for fast and effective monitoring during intense volcanic activity (frequent and overlapping eruptive events). This methodology could be used for the monitoring of remote or hazardous volcanoes that are difficult to study by means of repeated field surveys.