Geodetic data shed light on ongoing caldera subsidence at Askja, Iceland

International audience Subsidence within the main caldera of Askja volcano in the North of Iceland has been in progress since 1983. Here, we present new ground- and satellite-based deformation data, which we interpret together with new and existing micro-gravity data, to help understand which proces...

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Bibliographic Details
Published in:Bulletin of Volcanology
Main Authors: de Zeeuw-van Dalfsen, Elske, Rymer, Hazel, Sturkell, Erik, Pedersen, Rikke, Hooper, Andy, Sigmundsson, Freysteinn, Ófeigsson, Benedikt
Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2013
Subjects:
Volcano deformation
Caldera unrest
Micro-gravity
InSAR
Precise levelling
Iceland
[SDU]Sciences of the Universe [physics]
Askja
New Ground
Online Access:https://insu.hal.science/insu-03581910
https://doi.org/10.1007/s00445-013-0709-2
Description
Summary:International audience Subsidence within the main caldera of Askja volcano in the North of Iceland has been in progress since 1983. Here, we present new ground- and satellite-based deformation data, which we interpret together with new and existing micro-gravity data, to help understand which processes may be responsible for the unrest. From 2003 to 2007, we observe a net micro-gravity decrease combined with subsidence and from 2007 to 2009 we observe a net micro-gravity increase while the subsidence continues. We infer subsidence is caused by a combination of a cooling and contracting magma chamber at a divergent plate boundary. Mass movements at active volcanoes can be caused by several processes, including water table/lake level movements, hydrothermal activity and magma movements. We suggest that, here, magma movement and/or a steam cap in the geothermal system of Askja at depth are responsible for the observed micro-gravity variations. In this respect, we rule out the possibility of a shallow intrusion as an explanation for the observed micro-gravity increase but suggest magma may have flowed into the residing shallow magma chamber at Askja despite continued subsidence. In particular, variable compressibility of magma residing in the magma chamber as well as compressibility of the surrounding rock may be the reason why this additional magma did not create any detectable surface deformation.

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