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Please use this identifier to cite or link to this item:
http://hdl.handle.net/2122/4038
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| Title: | Cluster analysis of soil CO2 data from Mt. Etna (Italy) reveals volcanic influences on temporal and spatial patterns of degassing |
| Authors: | Giammanco, S.* Bonfanti, P.* |
| Keywords: | Mt. Etna Soil CO2 Diffuse degassing Cluster analysis Time series analysis Degassing model Volcanic activity |
| Issue Date: | 28-Jun-2008 |
| Publisher: | Springer Berlin / Heidelberg |
| Title of journal: | Bulletin of Volcanology |
| Series/Report no.: | / (2008) |
| Abstract: | Soil CO2 concentration data were collected
periodically from July 2001 to June 2005 from sampling
site grids in two areas located on the lower flanks of
Mt. Etna volcano (Paternò and Zafferana Etnea–Santa
Venerina). Cluster analysis was performed on the acquired
data in order to identify possible groups of sites where soil
degassing could be fed by different sources. In both areas
three clusters were recognised, whose average CO2 concentration
values throughout the whole study period
remained significantly different from one another. The
clusters with the lowest CO2 concentrations showed timeaveraged
values ranging from 980 to 1,170 ppm vol,
whereas those with intermediate CO2 concentrations
showed time-averaged values ranging from 1,400 to
2,320 ppm vol, and those with the highest concentrations
showed time-averaged values between 1,960 and
55,430 ppm vol. We attribute the lowest CO2 concentrations
largely to a biogenic source of CO2. Conversely,
the highest CO2 concentrations are attributed to a magmatic
source, whereas the intermediate values are due to a
variable mixing of the two sources described above. The
spatial distribution of the CO2 values related to the
magmatic source define a clear direction of anomalous
degassing in the Zafferana Etnea–Santa Venerina area,
which we attribute to the presence of a hidden fault,
whereas in the Paternò area no such oriented anomalies
were observed, probably because of the lower permeability
of local soil. Time-series analysis shows that most of the
variations observed in the soil CO2 data from both areas
were related to changes in the volcanic activity of Mt. Etna.
Seasonal influences were only observed in the time patterns
of the clusters characterised by low CO2 concentrations,
and no significant interdependence was found between soil
CO2 concentrations and meteorological parameters. The
largest observed temporal anomalies are interpreted as
release of CO2 from magma batches that migrated from
deeper to shallower portions of Etna’s feeder system. The
pattern of occurrence of such episodes of anomalous gas
release during the observation period was quite different
between the two studied areas. This pattern highlighted an
evident change in the mechanism of magma transport and
storage within the volcano’s feeder system after June 2003,
interpreted as magma accumulation into a shallow (<8 km
depth) reservoir. |
| URI: | http://hdl.handle.net/2122/4038 |
| URL: | http://www.springerlink.com/content/p77552m389115817/?p=98c7bf2664314ccea3dfaaa8ca764597&pi=1 |
| DOI: | 10.1007/s00445-008-0218-x |
| Appears in Collections: | Papers Published / Papers in press 04.08.01. Gases
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