Volcanic plume height correlated with magma-pressure change at Grímsvötn Volcano, Iceland



Magma flow during volcanic eruptions causes surface deformation that can be used to constrain the location, geometry and internal pressure evolution of the underlying magmatic source1. The height of the volcanic plumes during explosive eruptions also varies with magma flow rate, in a nonlinear way2,3. In May 2011, an explosive eruption at Grímsvötn Volcano, Iceland, erupted about 0.27 km3 dense-rock equivalent of basaltic magma in an eruption plume that was about 20 km high. Here we use Global Positioning System (GPS) and tilt data, measured before and during the eruption at Grímsvötn Volcano, to show that the rate of pressure change in an underlying magma chamber correlates with the height of the volcanic plume over the course of the eruption. We interpret ground deformation of the volcano, measured by geodesy, to result from a pressure drop within a magma chamber at about 1.7 km depth. We estimate the rate of magma discharge and the associated evolution of the plume height by differentiating the co-eruptive pressure drop with time. The time from the initiation of the pressure drop to the onset of the eruption was about 60 min, with about 25% of the total pressure change preceding the eruption. Near-real-time geodetic observations can thus be useful for both timely eruption warnings and for constraining the evolution of volcanic plumes.

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Figure 1: The location of Grímsvötn Volcano in Iceland and map of horizontal displacement.
Figure 2: GPS and tilt time series 21–23 May 2011.
Figure 3: Plume-top altitude, pressure change and accumulated erupted volume as a function of time 21–23 May 2011.


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We gratefully acknowledge the efforts of volunteers of the Icelandic Glaciological Society who operate the field research station at Mount Grímsfjall on Vatnajökull, and the technicians and staff at our institutions who have been involved in ensuring the successful collection of the data this paper is based on. Support for this work was received from the Icelandic Research Fund, the research fund at University of Iceland, National Science Foundation, USA, the French Polar Institute (IPEV Arctic program 316) and European Community’s FP7 Programme Grant No. 308377 (Project FUTUREVOLC). The mobile X-band radar was on loan from the Italian Civil Protection Agency. We thank UNAVCO for technical support. GMT public domain software was used for some figures. T. Högnadóttir prepared the map on Fig. 1b. R.G. acknowledges support from the Alaska Volcano Observatory.

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S.H. and F.S. coordinated the writing of the paper and the research it is based on; S.H. and R.G. analysed the GPS data; M.J.R., S.H. and F.S. analysed the tilt data; M.T.G., B.O., Á.H., G.L., T.T. and B.A.Ó. measured and evaluated the volume of the eruptive products; H.B. and P.A. measured the plume height from radar data and photos and evaluated variations in eruption rate; M.J.R. analysed the seismic data; S.H., M.J.R., F.S., M.T.G., B.O., P.A. and Á.H. were involved in daily monitoring of the eruptive activity; J.H. was the lead person in engineering and installing the tilt and GPS station at Grímsfjall; H.G., S.H., R.A.B., T.V., E.S., T.Á., B.G.Ó. and T.J. supervised and led the installation and operation of the high-rate GPS stations used in the research; F.S. and T.Á. modelled the geodetic displacements; S.H. produced the paper figures; S.H., R.G., M.J.R. and T.Á. produced Supplementary figures; S.H., F.S., R.G., M.J.R., T. Á. and M.T.G. led the writing of the paper with all authors discussing the results and commenting on the manuscript.

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Correspondence to Sigrún Hreinsdóttir or Freysteinn Sigmundsson.

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Hreinsdóttir, S., Sigmundsson, F., Roberts, M. et al. Volcanic plume height correlated with magma-pressure change at Grímsvötn Volcano, Iceland. Nature Geosci 7, 214–218 (2014). https://doi.org/10.1038/ngeo2044

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