ABSTRACT Geophysical (tilt, seismic tremor and gravity signals), geochemical (crater SO2 flux) an... more ABSTRACT Geophysical (tilt, seismic tremor and gravity signals), geochemical (crater SO2 flux) and infrared satellite measurements are presented and discussed to track the temporal evolution of the lava fountain episode occurring at Mt Etna volcano on 10 April 2011. The multi-disciplinary approach provides insight into a gas-rich magma source trapped in a shallow storage zone inside the volcano edifice. This generated the fast ascending gas-magma dispersed flow feeding the lava fountain and causing the depressurization of a deeper magma storage. Satellite thermal data allowed estimation of the amount of erupted lava, which, summed to the tephra volume, yielded a total volume of erupted products of about 1 × 106 m3. Thanks to the daylight occurrence of this eruptive episode, the SO2 emission rate was also estimated, showing a degassing cycle reaching a peak of 15,000 Mg d-1 with a mean daily value of ˜5,700 Mg d-1. The SO2 data from the previous fountain episode on 17-18 February to 10 April 2011, yielded a cumulative degassed magma volume of about ˜10.5 × 106 m3, indicating a ratio of roughly 10:1 between degassed and erupted volumes. This volumetric balance, differently from those previously estimated during different styles of volcanic activities with long-term (years) recharging periods and middle-term (weeks to months) effusive eruptions, points toward the predominant role played by the gas phase in generating and driving this lava fountain episode.
Egu General Assembly Conference Abstracts, May 1, 2010
... Island (Italy) 2 3 Rosalba Napoli 1 , Gilda Currenti 1 , Ciro Del Negro 1 , Agnese Di Stefano... more ... Island (Italy) 2 3 Rosalba Napoli 1 , Gilda Currenti 1 , Ciro Del Negro 1 , Agnese Di Stefano 1,2 , Filippo Greco 1 and 4 ... 100 All stations were devised using robust technologic components, which guarantee 101 uninterrupted working under harsh environmental conditions. ...
ABSTRACT 18-years (September 1994 - October 2011) gravity and ground deformation sequences, recor... more ABSTRACT 18-years (September 1994 - October 2011) gravity and ground deformation sequences, recorded at Etna volcano along an East-West trending profile of 19 stations on the southern flank at a quasi-monthly sampling rate, are presented. Over the last two decades, frequent fountaining events and several flank eruptions occurred at Mt Etna. We use the SBAS DInSAR technique to analyze the temporal evolution of surface displacements by inverting a sequence of interferograms to form a deformation time series. Height changes, evaluated by DInSAR data during the entire period, show modest vertical variations unable to produce significant gravity changes. However, the gravity data set was corrected for the small height variations using the experimental free-air gravity gradients measured at two stations of the profile. The residual space-time gravity image displayed some gravity increase/decrease cycles, mostly affecting the central and eastern stations of the East-West profile. We attributed these gravity cycles to mass redistribution processes mainly located at a depth of 2-4 km bsl in a region recognized to be a preferential pathway of magma rising and an intermediate zone of magma storage/withdrawal. In the latter period 2008-2011, when several paroxysmal events occurred from the South East crater, the gravity and height deformation patterns show many similarities with the previous period 1995-2000 encompassing a long series of paroxysmal episodes that preceded the violent and dramatic explosive/effusive eruptions of 2001 and 2002-2003.
Continuous gravity observations performed in the last few years, both at Mt. Etna and Stromboli, ... more Continuous gravity observations performed in the last few years, both at Mt. Etna and Stromboli, have prompted the need to improve the tidal analysis in order to acquire the best corrected data for the detection of volcano related signals. On Mt. Etna, the sites are very ...
ABSTRACT We present a multidisciplinary set of recent and new data that allowed to make a step fo... more ABSTRACT We present a multidisciplinary set of recent and new data that allowed to make a step forward in studying the internal mechanisms of a powerful lava fountain occurred at Etna volcano. In particular, the negative change in the signals recorded at two borehole strainmeters, installed just two weeks before the explosive event, gives clear evidence of a deep depressurizing source (depth of ca. 6-8 km below summit craters). The decompression was well recorded at both the two stations located at a radial distance from summit craters of 6 and 10 km, respectively. Due to the exceptional accuracy of the strainmeters (the nominal resolution is of about 10E-12 in strain), this episode represents the first time that strain field changes are observed at Etna with such precision during a lava fountain. As for other previous episodes, during the lava fountain the gravity signals of the two continuous stations showed a different reversal trend that inferred a shallower (ca. 1.5 km below summit craters) source, where the low density rich-gas magma (foam) accumulated and then was released during the lava fountain. Therefore, this set of data (strain and gravity) allowed to infer the positions of two intermediate storages involved in the shallow-intermediate plumbing system. Also magnetic data recorded a significant permanent piezomagnetic variation of about 3 nT providing useful constraints on the stress field. The piezomagnetic effect depends directly on the deviatoric stress and, hence, gave insights into the internal overpressure within the volcano edifice. During this event, satellite data acquired by MSG-SEVIRI (3 km of spatial resolution, 15 minutes of sample time) were elaborated to detect thermal anomalies, to compute a radiant heat flux and to provide an estimation of the emitted volume. Both strain signals and SEVIRI-derived radiant heat flux started to show a first significant change few hours before the lava fountain beginning, when also a lava flow was emitted from SE crater anticipating the paroxysmal event. The estimate of the emitted volume allowed to infer the overpressure released during the explosive episode, thus also providing constraints on pressure change associated with the depressurizing sources.
ABSTRACT Geophysical (tilt, seismic tremor and gravity signals), geochemical (crater SO2 flux) an... more ABSTRACT Geophysical (tilt, seismic tremor and gravity signals), geochemical (crater SO2 flux) and infrared satellite measurements are presented and discussed to track the temporal evolution of the lava fountain episode occurring at Mt Etna volcano on 10 April 2011. The multi-disciplinary approach provides insight into a gas-rich magma source trapped in a shallow storage zone inside the volcano edifice. This generated the fast ascending gas-magma dispersed flow feeding the lava fountain and causing the depressurization of a deeper magma storage. Satellite thermal data allowed estimation of the amount of erupted lava, which, summed to the tephra volume, yielded a total volume of erupted products of about 1 × 106 m3. Thanks to the daylight occurrence of this eruptive episode, the SO2 emission rate was also estimated, showing a degassing cycle reaching a peak of 15,000 Mg d-1 with a mean daily value of ˜5,700 Mg d-1. The SO2 data from the previous fountain episode on 17-18 February to 10 April 2011, yielded a cumulative degassed magma volume of about ˜10.5 × 106 m3, indicating a ratio of roughly 10:1 between degassed and erupted volumes. This volumetric balance, differently from those previously estimated during different styles of volcanic activities with long-term (years) recharging periods and middle-term (weeks to months) effusive eruptions, points toward the predominant role played by the gas phase in generating and driving this lava fountain episode.
Egu General Assembly Conference Abstracts, May 1, 2010
... Island (Italy) 2 3 Rosalba Napoli 1 , Gilda Currenti 1 , Ciro Del Negro 1 , Agnese Di Stefano... more ... Island (Italy) 2 3 Rosalba Napoli 1 , Gilda Currenti 1 , Ciro Del Negro 1 , Agnese Di Stefano 1,2 , Filippo Greco 1 and 4 ... 100 All stations were devised using robust technologic components, which guarantee 101 uninterrupted working under harsh environmental conditions. ...
ABSTRACT 18-years (September 1994 - October 2011) gravity and ground deformation sequences, recor... more ABSTRACT 18-years (September 1994 - October 2011) gravity and ground deformation sequences, recorded at Etna volcano along an East-West trending profile of 19 stations on the southern flank at a quasi-monthly sampling rate, are presented. Over the last two decades, frequent fountaining events and several flank eruptions occurred at Mt Etna. We use the SBAS DInSAR technique to analyze the temporal evolution of surface displacements by inverting a sequence of interferograms to form a deformation time series. Height changes, evaluated by DInSAR data during the entire period, show modest vertical variations unable to produce significant gravity changes. However, the gravity data set was corrected for the small height variations using the experimental free-air gravity gradients measured at two stations of the profile. The residual space-time gravity image displayed some gravity increase/decrease cycles, mostly affecting the central and eastern stations of the East-West profile. We attributed these gravity cycles to mass redistribution processes mainly located at a depth of 2-4 km bsl in a region recognized to be a preferential pathway of magma rising and an intermediate zone of magma storage/withdrawal. In the latter period 2008-2011, when several paroxysmal events occurred from the South East crater, the gravity and height deformation patterns show many similarities with the previous period 1995-2000 encompassing a long series of paroxysmal episodes that preceded the violent and dramatic explosive/effusive eruptions of 2001 and 2002-2003.
Continuous gravity observations performed in the last few years, both at Mt. Etna and Stromboli, ... more Continuous gravity observations performed in the last few years, both at Mt. Etna and Stromboli, have prompted the need to improve the tidal analysis in order to acquire the best corrected data for the detection of volcano related signals. On Mt. Etna, the sites are very ...
ABSTRACT We present a multidisciplinary set of recent and new data that allowed to make a step fo... more ABSTRACT We present a multidisciplinary set of recent and new data that allowed to make a step forward in studying the internal mechanisms of a powerful lava fountain occurred at Etna volcano. In particular, the negative change in the signals recorded at two borehole strainmeters, installed just two weeks before the explosive event, gives clear evidence of a deep depressurizing source (depth of ca. 6-8 km below summit craters). The decompression was well recorded at both the two stations located at a radial distance from summit craters of 6 and 10 km, respectively. Due to the exceptional accuracy of the strainmeters (the nominal resolution is of about 10E-12 in strain), this episode represents the first time that strain field changes are observed at Etna with such precision during a lava fountain. As for other previous episodes, during the lava fountain the gravity signals of the two continuous stations showed a different reversal trend that inferred a shallower (ca. 1.5 km below summit craters) source, where the low density rich-gas magma (foam) accumulated and then was released during the lava fountain. Therefore, this set of data (strain and gravity) allowed to infer the positions of two intermediate storages involved in the shallow-intermediate plumbing system. Also magnetic data recorded a significant permanent piezomagnetic variation of about 3 nT providing useful constraints on the stress field. The piezomagnetic effect depends directly on the deviatoric stress and, hence, gave insights into the internal overpressure within the volcano edifice. During this event, satellite data acquired by MSG-SEVIRI (3 km of spatial resolution, 15 minutes of sample time) were elaborated to detect thermal anomalies, to compute a radiant heat flux and to provide an estimation of the emitted volume. Both strain signals and SEVIRI-derived radiant heat flux started to show a first significant change few hours before the lava fountain beginning, when also a lava flow was emitted from SE crater anticipating the paroxysmal event. The estimate of the emitted volume allowed to infer the overpressure released during the explosive episode, thus also providing constraints on pressure change associated with the depressurizing sources.
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