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 Fe oxides 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.
|Titolo:||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|
|Data di pubblicazione:||2009|
|Appare nelle tipologie:||1.1 Articolo in rivista|