## 6 Conclusions  
The coupling of high-rate, even if noisy, and precise, albeit if low-rate, data allowed us to perform a comprehensive investigation of the dynamics leading to and enabling very rapid magma movement and pressure accumulation and discharge, through an impressive sequence of very violent eruptions. The overall picture coming from the different rates data analyses constrains the feeding system underlying such a quick and violent sequence of eruptive episodes (well summarized in Figure 11), allowing a rapid magma upraise and discharge from the summit crater, located at about 3300 m a.s.l. at Mt. Etna. In this framework, there is a deep, and not well-constrained here, pressurizing source that provides gas-rich magma to a middle-depth reservoir, located at about 6 km depth. This is the reservoir that gradually feeds the shallower system at about 1.5-2 km b.s.l., where the upper part of the magma batch temporarily stops and vesiculates, charging and producing each paroxysm when the pressure, mainly due to the essolution of gas, exceeds the containment pressure of the hosting rocks inside the volcano. Figure 11: Sketch of the feeding system resulting from HR and integrated ground deformation modeling. A deep and fairly continuous magma upraise feeds a middle-depth storage level. During the eruptive sequence, this storage is depleted to feed a shallower reservoir that works as a temporary storage, charging to feed each single-shot paroxysm. The combined mechanism of two storage levels at different depths depicts the possible feeding system of such high-discharge rate events, with a middle-depth storage of gas-rich magma that charges, more or less continuously, at a _recharging rate_ of about 15-20 m\({}^{3}\)/s, and a shallower level where magma stops temporarily, accumulating pressure due to the gas exsolution. When the pressure exceeds a threshold determined by lithostatic pressure and structural conditions of the shallower feeding system, the paroxysh starts, draining not only the magma accumulated in this shallower source but also part of that in the rest of the feeding system at an _eruptive discharge rate_ of more than 300 m\({}^{3}\)/s. When the gas pressure is discharged below the threshold, the paroxysh ends and the shallower source starts to be re-charged again. The _overall supply rate_ of the entire sequence is about 29-31 m\({}^{3}\)/s, which is similar to that estimated for the most recent sequence at SEC (February-March 2021). Thus, the model suggests a machine-gun-like mechanism, comprising a middle-depth reservoir continuously charging a shallower one that works as a firing chamber triggering each single-shot paroxysh. This mechanism, and the overall supply rates needed to feed this dynamic, could represent a general conceptual model for similar events at Etna and at all volcanoes. The following are available online at [[https://www.mdpi.com/article/10.3390/app11104630/s1](https://www.mdpi.com/article/10.3390/app11104630/s1)]([https://www.mdpi.com/article/10.3390/app11104630/s1](https://www.mdpi.com/article/10.3390/app11104630/s1)), XLS files refer to the tilt variations measured from December 2 to 7 at the eight stations here considered. In the other three XLS files, the tilt measured for the first three paroxysms are summarized. Each file lists the station name, its coordinates and its tilt components (in microradiants). The baseline variations are stored in a data structure within the MAT file. The structure includes the station names and locations, and a table with the baseline variations estimated for each period of the piecewise linear regression. 3D_SISTEM_output.zip: zipfile containing Ue_SISTEM.asc, Un_SISTEM.asc, Uu_SISTEM.asc SISTEM 3D Output (East, North and Up components of GPS and DInSAR integrated deformation, respectively) in ESRI- ASCII grid format, Word Geodetic System 1984 UTM, zone 33N (IGNF-UTM33W84), reference system (m) and a README.TXT file describing these files. GPS.csv: GPS displacement relevant to 2-14 December 2015 timespan. Conceptualization, A.B.