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 |
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| Authors: | Carmelo Ferlito Marco Viccaro Renato Cristofolini |
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| Institution: | 1.Dipartimento di Scienze Geologiche,Università di Catania,Catania,Italy |
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| 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 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. |
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