Volatile-rich magma injection into the feeding system during the 2001 eruption of Mt. Etna (Italy): its role on explosive activity and change in rheology of lavas

Abstract

The explosive behavior and the rheology of lavas in basaltic volcanoes, usually driven by differentiation, can also be significantly affected by the kinetics of magma degassing in the upper portion of the feeding system. The complex eruption of 2001 at Mt. Etna, Italy, was marked by two crucial phenomena that occurred at the Laghetto vent on the southern flank of the volcano: 1) intense explosive activity and 2) at the end of the eruption, emission of a lava flow with higher viscosity than flows previously emitted from the same vent. Here, we investigate the hypothesis that these events were driven by the injection of volatile-rich magma into the feeding system. The input and mixing of this magma into a reservoir containing more evolved magma had the twofold effect of increasing 1) the overall concentration of volatiles and 2) their exsolution with consequent efficient vesiculation and degassing. This led to an explosive stage of the eruption, which produced a~75-m-high cinder cone. Efficient volatile loss and the consequent increase of the liquidus temperature brought about the nucleation of Feoxides and other anhydrous crystalline phases, which significantly increased the magma viscosity in the upper part of the conduit, leading to the emission of a high viscosity lava flow that ended the eruption. The 2001 eruption has offered the opportunity to investigate the important role that input of volatile-rich magma may exert in controlling not only the geochemical features of erupted lavas but also the eruption dynamics. These results present a new idea for interpreting similar eruptions in other basaltic volcanoes and explaining eruptions with uncommonly high explosivity when only basic magmas are involved.

Regimes of magma recharge and their control on the eruptive behaviour during the period 2001–2005 at Mt. Etna volcano

“…4; cf. Monaco et al 2005;Viccaro et al 2006;Corsaro et al 2007;Ferlito et al 2009b). Consistent with our results, Caracausi et al (2003) and Rizzo et al (2006) observed an increased emission of CO 2 (exsolved at depth of~10 km) at the periphery of the volcanic edifice just before the 2001 eruption.…”

Imaging the multi-level magma reservoir at Mt. Etna volcano (Italy)

“…Gas boiling also can be caused by a relative increase of the content of volatiles in residual magma during crystal fractionation process occurring within the magma chamber and/or magma conduits or by the fluid migration irrespective of magma. The likelihood of this process, invoked to explain the increment of alkali in relatively shallow residing magmas [ Ferlito et al , 2009; Ferlito and Lanzafame , 2010], may be confirmed by the almost constant content of SO 2 in Mt. Etna's plume [ Caltabiano et al , 2004].…”

Magma, faults, and gravitational loading at Mount Etna: The 2002–2003 eruptive period

“…During the October 2002 to January 2003 eruptive event at Mount Etna, almost all fractures and fault systems in the eastern sector of the volcanic edifice were reactivated. Moreover, this event was characterized by seismicity, diffuse ground fracturing, strong explosive activity and petrographically distinct lava outputs, thus providing several constraints to constraining and testing models of the development of magma feeding systems and of the relationships with regional tectonics [see, e.g., Monaco et al , 2005; Neri et al , 2005; Ferlito et al , 2009]. The collected information and the subsequent analysis were crucial for building an overall and detailed numerical model (see below).…”