Publication Date:
2017-04-04
Description:
Studies on volcanic degassing have recently shown the important role of volatile release from active volcanoes
in understanding magmatic processes prior to eruptions. Here we present and discuss the evolution of magmatic
degassing that preceded and accompanied the 2008 Mt. Etna eruption. We tracked the ascent of magma bodies
by high-temporal resolution measurements of SO2 emission rates and discrete sampling of SO2/HCl and SO2/HF
molar ratios in the crater plume, as well as by periodic measurement of soil CO2 emission rates. Our data suggest
that the first signs of upward migration of gas-rich magma before the 2008 eruption were observed in June 2007,
indicated by a strong increase in soil CO2 efflux followed by a slow declining trend in SO2 flux and halogens. This
degassing behavior preceded the mid-August 2007 summit activity culminated with the September 4th paroxysmal
event. Five months later, a new increase in both soil CO2 and SO2 emission rates occurred before the November
23rd paroxysm, to drop down in late December. In the following months, geochemical parameters showed high
variability, characterized by isolated sudden increases occurred in early December 2007 and late March 2008. In
early May soil CO2, SO2 emission rates and S/Cl molar ratio gradually increased. Crater degassing peaked on
May 13th marking the onset of the eruption. Eruptive activity was accompanied by a general steady-state of SO2
flux characterized by two main degassing cycles. These cycles preceded explosive activity at the eruptive vents,
indicating terminal new-arrival of deep gas-rich magma bodies in the shallow plumbing system of Mt Etna. Conversely,
halogens described a slight increasing trend till the end of 2008. These observations suggest an impulsive
syn-eruptive dynamics of magma transfer from depth to the surface. Differently from the SO2 emission rates, the
S/Cl ratio and the soil CO2 efflux values showed an increasing trend from mid-April to mid-July 2008, indicating
steady-increasing input of deeper, gas-rich magma. Since August, geochemical parameters decreased, suggesting
that new magma has not arrived from depth. According to our interpretation, both the CO2 efflux and the S/Cl ratio
increases observed in early November may indicate a new input of fresh magma form depth. Finally, the estimated
volume of degassing magma showed substantial equilibrium between degassed and erupted magma suggesting an
“eruptive” steady-state of the volcano.
Description:
INGV, Sezione di Catania; INGV, Sezione di Pisa; University of Cambridge, Cambridge, UK
Description:
Published
Description:
Vienna, Austria
Description:
1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
Description:
open
Keywords:
Mt. Etna
;
plume gases
;
soil CO2
;
eruption
;
04. Solid Earth::04.08. Volcanology::04.08.01. Gases
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Abstract
Permalink
