Degassing behaviour of Hekla volcano - verkefni lokið
Fréttatilkynning verkefnisstjóra
Hekla is one of the most active volcanoes in Iceland and has an infamously short pre-eruptive warning period. Our project contributes to the ongoing work on improving Hekla's monitoring and early warning systems.
In 2012 we began monitoring gas release at Hekla. This
original dataset comprises near-real time measurements with a permanent
MultiGAS monitoring system, mapping and quantification of diffuse gas flux, and
direct samples analyzed for composition and stable isotopes. In addition, we
used reaction path modelling to derive information on the origin and reaction
pathways of the gas emissions.
Heiti verkefnis: Degassing behaviour of Hekla volcano
Verkefnisstjóri: Evgenia Ilyinskaya, Veðurstofu Íslands
Tegund styrks: Verkefnisstyrkur
Styrkár: 2012-2013
Fjárhæð styrks: 8,996 millj. kr. alls
Tilvísunarnúmer Rannís: 12020402
At the time of our study, Hekla was in a quiescent state with no focused gas venting, but visible steam emanations were found in areas near its summit. Hekla's gas composition was CO2-dominated (80%) and the δ13C signature was consistent with known values for Icelandic magmas. The gas is poor in H2O and S compared to hydrothermal manifestations and syn-eruptive emissions from other active volcanic systems in Iceland. The total CO2 flux from Hekla mountain is at least 44 T/day, thereof 14 T/day are sourced from a small area at the volcano's summit. There was no detectable gas flux at other craters, even though some of them had higher ground temperatures and had erupted more recently.
Our measurements are consistent with a magma reservoir at depth coupled with a shallow dike beneath the summit. In the current quiescent state, the composition of the exsolved gas is substantially modified along its pathway to the surface through cooling and interaction with wall-rock and groundwater. The modification involves both significant H2O condensation and scrubbing of S-bearing species, leading to a CO2- dominated gas emitted at the summit. We conclude that a compositional shift towards more S- and H2O-rich gas compositions if measured in the future by the permanent MultiGAS station should be viewed as sign of imminent volcanic unrest on Hekla.
This project served as a proof-of-concept for volcanic gas monitoring in Iceland as this was the first time a permanent monitoring station was installed in Iceland. The station set-up was specifically designed by our group to tolerate Icelandic winter conditions and the design has since been applied to other high-altitude volcanoes elsewhere in the world.
The permanent station at Hekla is still in operation and the data are transmitted to the monitoring team of the Icelandic Meteorological Office (the national volcano observatory). The Icelandic gas monitoring network now extends to several other volcanic systems, and we have developed ‘rapid-installation' stations to be deployed in areas of unrest (e.g. at jökulhlaup sites).
Publications:
Ilyinskaya E; Aiuppa A; Bergsson B; Di Napoli R; Fridriksson T; Óladóttir AA; Óskarsson F; Grassa F; Pfeffer M; Lechner K; Yeo R; Giudice G (2015) Degassing regime of Hekla volcano 2012-2013, Geochimica et Cosmochimica Acta, 159, pp.80- 99. doi: 10.1016/j.gca.2015.01.013. [Open access]
Di Napoli R; Aiuppa A; Bergsson B; Ilyinskaya E; Pfeffer M; Guðjónsdóttir S; Valenza M (2016) Reaction path models of magmatic gas scrubbing, Chemical Geology, 420, pp.251-269. doi:10.1016/j.chemgeo.2015.11.024
