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Titel |
The 2010 Eyjafjallajökull volcanic summit eruption: evidences from ash-leachates analysis and ground deposition fluxes |
VerfasserIn |
E. Bagnato, A. Aiuppa, A. Bertagnini, C. Bonadonna, R. Cioni, M. Pedone, M. Pistolesi |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250060995
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Zusammenfassung |
The Eyjafjallajökull 2010 eruption was an extraordinary event in that it led to widespread
over Europe. Volcanic processes which lead to eruptions can be investigated by monitoring a
variety of parameters, including the composition of ash leachates. Fine-grained
tephra erupted from active vents, and transported through volcanic plumes, can
adsorbs, and therefore rapidly scavenge, volatile elements such as S, halogens, and
metal species in the form of soluble salts adhering to ash surfaces. Analysis of such
water-soluble phases is a suitable complement for the remote sensing of volcanic gases at
inaccessible volcanoes, like Eyjafjallajökull. The 2010 Eyjafjallajökull eruption
developed in four main phases, whose difference in gas chemistry and products
has been marked in ash-leachates data too. The recurrent ash fallout provided a
unique opportunity to characterize the compositional features of ash leachates, and to
identify their relation (if any) with the eruptive activity styles of the volcano. By these
considerations, we report on the chemical composition of leachates of 20 volcanic
ash samples deposited during the most explosive Eyjafjallajökull activities (from
14 April to 8 May) and during the lava fountaining event (on 26th March 2010).
We found that ash-leachate solutions are dominated - among cations - by Na and
Ca, while they display nearly equal S : Cl : F abundances (mean S-Cl and S-F
molar ratios of 0.85 and 0.33, respectively), as characteristic of divergent-plate and
within-plate volcanism. The strong correlations between leached Ca - F , Ca - SO4,
and Na - Cl (r2 = 0.7 - 0.9), suggest that fluorite, anhydrite, and halite are the
most likely soluble surface minerals formed in the plume (and therefore leached
during our experiments), as also reported at many active volcanoes. Our data bring
evidence for variations in S and halogens proportions, with samples from 5 - 8th
May which show the highest S-Cl and lowest Cl-F ratios. By combining the
concentration of leached SO4, F and Cl with the mass/area ratio of deposited ash
(normalized to 30 min of 5-8 May 2010 volcanic phase), we estimated mean depositional
elemental fluxes of about 1.0 Ã 10-5, 1.1 Ã 10-3 and 1.2 Ã 10-3 g -
m-2s-1, for the
water-soluble SO4, Cl and F , respectively. By integrating these data over the whole
sampling area, we estimated a total depositional flux of about 864, 605 and 691
t -
day-1, for SO4, Cl and F , respectively. These data mean that ~ 15% of Sgas
and 29% of Clgas discharged into the plume during the same eruptive phase, may
have been scavenged by adsorption processes on ash surfaces within the eruption
column. |
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