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| Titel |
Monitoring quiescent volcanoes by diffuse He degassing: case study Teide
volcano |
| VerfasserIn |
Nemesio M. Pérez, Gladys Melián, María Asensio-Ramos, Eleazar Padrón, Pedro A. Hernández, José Barrancos, German Padilla, Fátima Rodriguez, David Calvo, Mar Alonso |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130180
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| Publikation (Nr.) |
 EGU/EGU2016-10396.pdf |
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| Zusammenfassung |
| Tenerife (2,034 km2), the largest of the Canary Islands, is the only island that has developed a
central volcanic complex (Teide-Pico Viejo stratovolcanoes), characterized by the eruption of
differentiated magmas. This central volcanic complex has been built in the intersection of the
three major volcanic rift-zones of Tenerife, where most of the historical volcanic activity has
taken place. The existence of a volcanic-hydrothermal system beneath Teide volcano is
suggested by the occurrence of a weak fumarolic system, steamy ground and high rates of
diffuse CO2 degassing all around the summit cone of Teide (Pérez et al., 2013). Diffuse
emission studies of non-reactive and/or highly mobile gases such as helium have recently
provided promising results to detect changes in the magmatic gas component at
surface related to volcanic unrest episodes (Padrón et al., 2013). The geochemical
properties of He minimize the interaction of this noble gas on its movement toward the
earth’s surface, and its isotopic composition is not affected by subsequent chemical
reactions. It is highly mobile, chemically inert, physically stable, non-biogenic,
sparingly soluble in water under ambient conditions, almost non-adsorbable, and
highly diffusive with a diffusion coefficient ∼10 times that of CO2. As part of the
geochemical monitoring program for the volcanic surveillance of Teide volcano, yearly
surveys of diffuse He emission through the surface of the summit cone of Teide
volcano have been performed since 2006. Soil He emission rate was measured
yearly at ∼130 sampling sites selected in the surface environment of the summit
cone of Teide volcano (Tenerife, Canary Islands), covering an area of ∼0.5 km2,
assuming that He emission is governed by convection and diffusion. The distribution of
the sampling sites was carefully chosen to homogeneously cover the target area,
allowing the computation of the total He emission by sequential Gaussian simulation
(sGs). Nine surveys have been carried out since 2006, showing an average emission
rate of 8.0 kg/d. This value showed an anomalous increase up to 29 kg/d in the
summer of 2010. The number of seismic events registered in and around Tenerife
Island by the National Geographic Institute (IGN) reached also the highest value
(1,176) in 2010. This excellent agreement between both times series suggest that the
anomalous seismicity registered in 2010 was likely due to strain/stress changes
caused by input of magmatic fluids beneath the central volcanic system of the island.
These results suggest that monitoring of He degassing rates in oceanic volcanic
islands is an excellent early warning geochemical precursory signal for volcanic
unrest.
References
Padrón et al., 2013. Geology, DOI: 10.1130/G34027.1.
Pérez et al., 2013. J. Geol. Soc., DOI: 10.1144/jgs2012-125. |
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