“…The δ 13 C and CO 2 /SO 2 ratios are powerful tracers of magma degassing at Mount Etna volcano, Italy (e.g., Aiuppa et al, 2007Aiuppa et al, , 2010Paonita et al, 2012) and in many other volcanic systems worldwide (e.g., Stromboli, Italy: Capasso et al, 2005;Aiuppa et al, 2009;Rizzo et al, 2009; Turrialba, Costa Rica: Moussallam et al, 2014). While high-frequency measurements of the CO 2 /SO 2 ratio have revealed this to be a powerful tracer for detecting pre-eruptive degassing of ascending magmas (e.g., Aiuppa et al, 2007;Shinohara et al, 2008;Patané et al, 2013), δ 13 C is currently only monitored in fumarolic gases via discrete sampling, and so only provides medium-to long-term clues about the dynamics occurring at depth.…”