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| Titel |
Long-range volcanic ash transport and fallout during the 2008 eruption of Chaiten volcano, Chile |
| VerfasserIn |
A. J. Durant, A. J. Prata, G. Villarosa, W. I. Rose, P. Delmelle, J. Viramonte |
| 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 |
250064475
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| Zusammenfassung |
| The May 2008 eruption of Chaitén volcano, Chile, provided a rare opportunity to measure the
long-range transport of volcanic emissions and characteristics of a widely-dispersed
terrestrial ash deposit. Airborne ash mass, quantified using thermal infrared satellite remote
sensing, ranged between 0.2-0.4 Tg during the period 3-7 May 2008. A high level of
spatiotemporal correspondence was observed between cloud trajectories and changes in
surface reflectivity, which was inferred to indicate ash deposition. The evolution of the
deposit was mapped for the first time using satellite-based observations of surface
reflectivity.
The distal (>80 km) ash deposit was poorly sorted and fine grained, and mean particle
size varied very little beyond a distance >300 km. There were 3 consistent particle size
subpopulations in fallout at distances >300 km which suggests that aggregation influenced
particle settling. Discrete temporal sampling and characterisation of fallout demonstrated
contributions from specific eruptive phases. Some evidence for winnowing was identified
through comparison of samples collected at the time of deposition to bulk samples collected
months after deposition.
X-Ray Photoelectron Spectroscopy (XPS) analyses revealed surface enrichments in Ca,
Na and Fe and the presence of coatings of mixed Ca-, Na- and Fe-rich salts on ash
particles prior to deposition. XPS analyses revealed strong surface Fe enrichments (in
contrast to the results from bulk leachate analyses), which indicates that surface
analysis techniques should be applied to investigate potential influences on ocean
productivity in response to volcanic ash fallout over oceans. Low S:Cl ratios in leachates
indicate that the eruption had a low S content, and high Cl:F ratios imply gas-ash
interaction within a Cl-rich environment. We estimate that ash fallout had potential
to scavenge ~42 % of total S released into the atmosphere prior to deposition. |
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