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| Titel |
Assessing the atmospheric and climatic effects of basaltic fissure eruptions. A case study Nornahraun, North Iceland, 2014-2015. |
| VerfasserIn |
Catherine Gallagher, Kevin Burton, Thorvaldur Thordarson  , Charlotte Vye-Brown, Richard Brown |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112962
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| Publikation (Nr.) |
 EGU/EGU2015-13152.pdf |
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| Zusammenfassung |
| A volcanic eruption’s ability to release sulphur gases into the atmosphere is one of the critical
factors in assessing their climatic and environmental effects, because it is directly linked to
the potential H2SO4 aerosol burden produced [1]. Basaltic fissure eruptions loft
large amounts of sulphur into the atmosphere because of the efficient degassing of
volatiles and halogens from the magma at the vent [2-4] coupled with the high
sulphur yield of basaltic magma. The common nature of this style of eruption and
its products, regardless of magnitude, means that our understanding of the exact
processes which influence atmospheric chemistry and environmental impact is very
important.
The Nornahraun fissure eruption in North Iceland that began on the 31st August 2014, has
quickly become one of the best documented eruptions of its kind, through systematic
monitoring and sampling by the Institute of Earth Sciences eruption team and The
Icelandic Meteorological Office. As a result it is an excellent modern analogue for
historic or ancient basaltic fissure eruptions, for which the amount of degassing can
only be estimated through petrological and geochemical methods. It also serves
as a timely testing platform for novel geochemical proxies. This study uses the
exceptional sensitivity of the 187Os-187Re radiogenic system to the presence of crustal
material [5], and highly siderophile stable isotopes Cu, Zn and S to indicate the
chemistry and degassing of the melt carrying S to the surface. The geochemical isotopic
proxies will be tested using established petrological methods and gas emission
data.
This study concentrates on determining the following key parameters:
(1) The source of volatiles in the magma indicated though the pressure dependence of S
solubility.
(2) The mechanism of aerosol and gas release into the atmosphere is dictated both by the
chemistry of the melt that controls the S species (H2S, SO2 or FeS2) present [6], and by the
mechanism of transfer.
(3) The amount of volatiles released during a basaltic fissure eruption both at the vent
(>70%) as well as during lava transport [2-4]. This uses the petrological method of
Devine et al (1984) and a two-stage degassing model [3] to establish the total S
budget.
(4) The duration of atmospheric loading of volatiles in an eruption, which affects the
residence time of these gases and aerosols.
The Nornahraun event provides the opportunity to verify the gas species and aerosols present
in the atmosphere. By utilising the very well documented Nornahraun eruption, better
constraints can be obtained on the atmospheric effects of well-known historical eruptions
such as Laki 1783-84. Scaling up of such models to large flood basalt eruptions
may shed light on their climatic effects and postulated association with major mass
extinctions.
[1] Thordarson, T. et al. Geol. Soc. London. Spec. Publ. 213 (2003), 103-121.
[2] Guilbaud, M.-N. et al. Journal of Petrology 48.(2007), 1265-1294.
[3] Thordarson, T. et al. Bulletin of Volcanology 58.(1996), 205-225.
[4] Metrich, N. et al. Contrib Mineraology Petrol 107.(1991), 435-447.
[5]Gannoun, A. et al. Science 303.(2004),70-72.
[6] Burgisser, A., Scaillet, B. Nature 445.(2007), 194-197. |
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