## 5 Discussion
In particular, until March 2012, the temporal variations in \(\mathrm{SHS_{Flux}}\) from the ground seem related to the pre-eruptive magmatic processes occurring in a magma batch located at 1-2 km a.s.l. beneath the NEC [28; 44]. In contrast, after March 2012, the condensation level of hydrothermal vapor descended to the deepest observed depths (Figure 4), and afterwards, the inverse correlation with the air temperature probably remained the main feature of \(\mathrm{SHS_{Flux}}\) variations (Figure 5). Clearly before the onset of the last two lava fountains (LF3 and LF4 on April 2012, Table 2) an evident decrease in the thermal output from the ground was registered at the BTL station (Figures 5-7). Finally, during LF4, the \(\mathrm{SHS_{Flux}}\) in the NE Rift reached the lowest values, remaining very low for the next 10 days (Figures 5 and 6). The different modulations in the \(\mathrm{SHS_{Flux}}\) between the March and April episodes are probably related to the different energy displayed by the lava fountains (Figure 7, Table 2). Afterwards, the volcanic system entered a new quiescent period and the next lava fountain occurred on 19 February 2013 [31], whereas the new lava flow started later on (26 October 2013 [45; 48]). Focusing on 2012, this record of ground temperatures from the NE Rift provided some precursory signals on the transient behavior of the volcanic system towards the standstill of the eruptive activity, despite several sustained lava fountains that were still going to occur and the lava still flowing from the NSEC. The recorded data clearly show that the power of the convective circulation on the NE Rift decreased several hours before the onset of the last lava fountains from NSEC (the two most energetic paroxysm, with TRE > 5 \(\times\) 10\({}^{10}\) J). The decrease in heat flux was irreversible after the end of the eruption, and the negative pulses of the convective front were repeated frequently below the BTL monitoring station throughout the following months. Thus, the intensity and position of the thermal anomaly detected at the surface--and particularly the depth reached by the front of the ascending steam, as monitored by the BTL station--provide new evidence on the framework of observations about the behavior of the volcanic complex of Mt. Etna volcano. The NSEC and NE Rift are two different volcanic features, but they were both impacted by convective processes (fluid transfer responding to pressure gradients) during the monitored period. The conceptual model proposed by [PERSON] et al. [29] postulated a fast change in the proportions between magma and gas. This hypothesis could also explain the instability of the front of rising vapor escaping through the NE Rift and the highly variable range of \(\mathrm{SHS_{Flux}}\) during the eruptive period. The position of the volcanic tremor centroid, which happened before the reappraisal of the volcanic activity, suggests the open conduit located beneath the NEC as the site of the structural connection of magma ascending through distinct pathways at 2 km a.s.l. [28]. The major modulations of \(\mathrm{SHS_{Flux}}\) observed during the eruptive phases are possibly correlated to the transient gas bursts postulated by [PERSON] et al. [28] to explain the fast transition from strombolian activity to lava fountaining. At the end of the eruptive period (April 2012), the further decrease in the \(\mathrm{SHS_{Flux}}\) released by the NE Rift (Figure 5), coupled with the convergence of magmatic fluids towards the NSEC, caused the observed local instability of the convective front (Figure 4). A part of the heat flow, generally dispersed by the NE Rift during the previous paroxysms, was channeled through the explosive crater as an additional component to these more energetic lava fountain events, which concluded the long eruptive phases begun in November 2010.