Decades of subsidence followed by rapid uplift

Decades of subsidence followed by rapid uplift: Insights from microgravity data at Askja Volcano, Iceland

Koymans, M.R. (TU Delft Applied Geophysics and Petrophysics; Royal Netherlands Meteorological Institute (KNMI))
de Zeeuw-van Dalfsen, E. (TU Delft Mathematical Geodesy and Positioning; Royal Netherlands Meteorological Institute (KNMI))
Sepúlveda, J. (University of Leeds)
Evers, L.G. (TU Delft Applied Geophysics and Petrophysics; Royal Netherlands Meteorological Institute (KNMI))
Giniaux, J. M. (University of Leeds)
Grapenthin, R. (University of Alaska Fairbanks)
Hooper, A. (University of Leeds)
Ófeigsson, B. G. (Icelandic Meteorological Office; Nordic Volcanological Center)
Sigmundsson, F. (Nordic Volcanological Center)
Yang, Y. (Nordic Volcanological Center)

2023

In August 2021, Askja volcano in Iceland returned to the spotlight after a sudden onset of rapid uplift followed decades of continuous subsidence. In this study the extended record of microgravity data from Askja between 1988 to 2017 is revisited, and new microgravity data from 2021 and 2022 are introduced, which were collected after the uplift had started. Askja caldera had been steadily subsiding since at least 1984 and was characterised by a net decrease in microgravity, potentially signalling the contraction of its magma chamber or eviction of magma either laterally or to deeper levels. The microgravity data indicate that despite ongoing subsidence between 2017 and early 2021, a significant gravity increase can be detected in the center of the caldera between 2017 and August 2021. This increase may be introduced during – or leading up to – the period of uplift. The new microgravity data also indicate that during the period of 40 cm uplift after August 2021 to fall 2022, gravity changes approach the free-air gradient, suggesting subsurface density decreases as a driving process. This process may relate to the vesiculation of magma previously emplaced in the volcano roots, a change in the hydrothermal system, or replacement of dense basaltic magma with less dense rhyolitic magma, or a combination of these processes. However, uncertainties for this period are elevated and may obscure a gravity signal expected from additional mass accumulation. The timing and high uncertainties of some campaigns make it challenging to be conclusive on the driving process behind the uplift, but future microgravity campaigns could help solve the ambiguity. The study also provides a description of potential pitfalls in microgravity campaigns and recommendations on how the reliability of microgravity data can be improved.

Askja
Campaign
Data
Deformation
Microgravity
Volcano

http://resolver.tudelft.nl/uuid:a4d129b2-37e4-4213-998a-d02846955b7f

https://doi.org/10.1016/j.jvolgeores.2023.107890

2024-02-22

0377-0273

Journal of Volcanology and Geothermal Research, 442

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2023 M.R. Koymans, E. de Zeeuw-van Dalfsen, J. Sepúlveda, L.G. Evers, J. M. Giniaux, R. Grapenthin, A. Hooper, B. G. Ófeigsson, F. Sigmundsson, Y. Yang