Abstract
Estimates of lava volumes provide important data on the lava flooding history and evolution of a volcano. For mapping these volcanic deposits, the advancement of satellite remote sensing techniques offer a great potential. Here we characterize the eruptive events occurred at Mt Etna between January 2011 and December 2015 leading to the emplacement of numerous lava flows and to the formation of a new pyroclastic cone (NSEC) on the eastern flank of the South East Crater. The HOTSAT system is used to analyze remote sensing data acquired by the SEVIRI sensor in order to detect the thermal anomalies from active lava flows and calculate the associated radiative power. The time-series analysis of SEVIRI data provides an estimation of event magnitude and intensity of the effusive material erupted during each event. The cumulative volume estimated from SEVIRI images from 2011 to 2015 adds up to ~106 millions of cubic meters of lava and is constrained using a topographic approach, i.e. by subtracting the last topography of Etna updated to 2005 from a 2015 digital elevation model, produced using tri-stereo Pleiades satellite images acquired on December 18, 2015. The total volume of products erupted from 2005 to 2015, calculated from topography difference by integration of the thickness distribution over the area covered, is about 287×106 m3, of which ~55×106 m3 is the volume of the NSEC cone.
Highlights
Mapping the volcanic deposits constitute a critical component for constraining magma supply, understanding magma plumbing system, and controlling lava flow morphological parameters, and represents an important indication of the amount of magma the volcanic system is capable of transporting during an eruptive event (Wadge et al, 1975; Stevens et al, 1999)
HOTSAT takes as input mid-infrared (MIR) and thermal infrared (TIR) channels acquired by the Spinning Enhanced Visible and Infrared Imager (SEVIRI), and provides cloud mask and thermal anomalies maps
The lava thermal flux is computed considering all those pixels classified as “hot” by using the mid-infrared radiance approach introduced by Wooster et al (2003), which allows estimating the radiant heat flux radiated by a sub-portion of the thermally anomalous pixels approximating the Planck’s radiation law to a fourth order power law. This approach is efficient with low spatial resolution sensors, such as SEVIRI, or moderate spatial resolution sensors such as Moderate Resolution Imaging Spectroradiometer (MODIS), given that the extent of lava flow fields is often subpixel in size (Ganci et al, 2013)
Summary
Mapping the volcanic deposits constitute a critical component for constraining magma supply, understanding magma plumbing system, and controlling lava flow morphological parameters, and represents an important indication of the amount of magma the volcanic system is capable of transporting during an eruptive event (Wadge et al, 1975; Stevens et al, 1999). The calculation of the amounts of lava erupted is still source of uncertainty, and problems occur when comparing volume values that are measured using different approaches (Harris et al, 2007). The second approach requires accurate mapping of the pre and post-eruption Digital Elevation Models (DEMs). This topographic approach is advantageous because deposit thickness is mapped throughout the flow field, resulting in detailed threedimensional measurements of the morphology and yielding a highly accurate volume estimate. The method is limited by the availability of topographic data of the surface underneath the volcanic deposit of interest, and such measurements are difficult, if not impossible, to be made retrospectively (Del Negro et al, 2016)
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