Abstract
A new sequence of eruptions occurred at Mt. Etna volcano during the first half of 2017, after almost 8 months of quiescence. These episodes had low-to-mild intensity and markedly differ from the violent paroxysms occurred at the Voragine Crater (VOR) during December 2015 and May 2016. Despite the general weak explosive nature of the eruptions, the activity during 2017 revealed unusually complex dynamics of magma ascent and interaction. Detection and investigation of such dynamics required a multidisciplinary approach in which bulk rock compositions, crystal chemical zoning, diffusion chronometry and ground deformation data have been combined. Bulk rock major and trace elements suggest that the 2017 magmas followed a differentiation path similar to that experienced by magmas erupted at Mt. Etna during the 2015–16 eruptions at VOR. Olivine core compositions and zoning patterns indicate the presence of multiple magmatic environments at depth that strictly interacted each other through some episodes of intrusion and mixing before and during the 2017 eruptive events. Timescales retrieved from diffusion chronometry on olivine normal and reverse zoning correlate well with the ground deformation stages detected through geodetic data and associated models, thus allowing to track the evolution through time of the 2017 volcanic activity. Combination of all petrological and geodetic observations supports the idea that dynamics of magma transfer driving the eruptive episodes of 2017 have been a direct consequence of the violent eruptions occurred at VOR on May 2016, which boosted the ascent of new magma from depth and improved the efficiency of the plumbing system to transfer it upward to the surface. We propose a mechanism of self-feeding replenishment of the volcano plumbing system during 2017, where magma recharge from depth is triggered by sudden unloading of the magma column consequential to the violent paroxysmal activity occurred on May 2016 at VOR.
Highlights
In the last few decades, several eruptions have taken place at Mt
This enables to address some important changes in the modes of magma supply into the Etnean plumbing system during 2017, which is a direct consequence of the last violent paroxysmal episodes occurred at Voragine Crater (VOR) on May 2016
All the petrological and geodetic data support a model of self-feeding magma replenishment originated as a consequence of the violent paroxysmal eruptions occurred at VOR in May 2016
Summary
In the last few decades, several eruptions have taken place at Mt. Etna in relatively short succession, passing from periods of entirely effusive to strongly explosive activity (i.e., violent Strombolian to lava fountains). Based on an extensive dataset of concentration and diffusion profiles of olivine crystals combined with geodetic observations, we are able to interpret the volcanic unrest throughout the 2017 eruptive period in terms of deep and subsurface pre-eruptive processes such as the storage, transport and interactions of magmas Such approach of investigation allows the spatial localization of active magmatic sources, and defines their temporal activation before and during each eruptive episode. Other weak Strombolian eruptions took place on April 13–15 and April 19–21 at the vent located on the SEC-NSEC saddle, and were accompanied by emission of new lava flows from fractures located on the southern flank of the SEC These flows were directed to south and southeast toward the Valle del Bove and reached an altitude of 1950 m asl (Fig. 1a). On May 2017, SEC was characterized by episodic intra-crateric activity that completely ceased during June 2017
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