Long-term record of CO2degassing along Mt. Etna's flanks and its relationship with magma dynamics and eastern flank instability

Abstract

A record of soil CO2 flux data on the lower flanks of Mt. Etna, measured from 1989 to 2008, is discussed in the framework of multidisciplinary observations, including seismicity, ground deformations, and flank instability. A huge increase in soil CO2 fluxes appears to be related to the dynamics of magma ascent in the upper portions of the volcano (0–3 km) and the intrusion of dykes along the southern rift, as mainly observed before the 1991–93 eruption. Even after the 1991–93 eruption, the recharge of the shallow/central reservoir was accompanied by a long-term increase in soil CO2 degassing mainly in the southwestern area. The 2001 eruption marked dramatic changes in the areal distribution of seismicity, the deformation pattern, and the soil CO2 degassing. Indeed, while the soil CO2 degassing showed background values in the southwestern area, it progressively increased in the eastern sector and along the Pernicana fault. This has been related to the marked sliding of the eastern flank since the 2002–03 eruption and the associated seismicity. This study provides evidence that the extent of soil CO2 degassing on the lower flanks of Mt. Etna is controlled by (1) the volume of involved magma, (2) the intrusion of dykes in the upper parts of the volcano, and (3) fault movement and seismicity. This implies that different degassing structures must be monitored simultaneously when attempting to understand the behavior of the volcano as a whole.