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

  • Elske de Zeeuw-van Dalfsen
  • Hazel Rymer
  • Erik Sturkell
  • Rikke Pedersen
  • Andy Hooper
  • Freysteinn Sigmundsson
  • Benedikt Ófeigsson
Research Article


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.


Volcano deformation Caldera unrest Micro-gravity InSAR Precise levelling Iceland 



This project was financed by a Marie Curie intra-European fellowship (from EDZ). EDZ thanks Claude Jaupart, Eleonora Rivalta, Petar Marinkovic, Judicael Decriem, Florian Lhuillier, Rósa Ólafsdóttir and Thom Warmerdam for discussion, help with data processing, MATLAB programming, GMT plotting, DEM preparation and other computer issues. EDZ thanks Rósa Ólafsdóttir for preparation of Fig. 1c. The CSA provided RADARSAT images for this project as part of a DRU proposal. MDA assisted with the data selection and ordering procedures. Financial support to RP was received from Rannís. The DEM and xy data files were produced by the Icelandic Geodetic Survey. GMT public domain software was used to prepare Fig.1a and b. We thank Glyn Williams-Jones, Takao Ohminato and an anonymous reviewer for their constructive comments.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Elske de Zeeuw-van Dalfsen
    • 1
    • 2
  • Hazel Rymer
    • 3
  • Erik Sturkell
    • 4
    • 5
  • Rikke Pedersen
    • 5
  • Andy Hooper
    • 6
  • Freysteinn Sigmundsson
    • 5
  • Benedikt Ófeigsson
    • 5
  1. 1.Institut de Physique du Globe de ParisParisFrance
  2. 2.Department 2 - Physics of the EarthGFZ German Research Centre for GeosciencesPotsdamGermany
  3. 3.Faculty of ScienceThe Open UniversityMilton KeynesUK
  4. 4.Institute for GeosciencesGöteborgSweden
  5. 5.Nordic Volcanological Centre, Institute of Earth SciencesUniversity of IcelandReykjavikIceland
  6. 6.Delft University of TechnologyDelftthe Netherlands

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