Halldor Geirsson

Photo of Halldor Geirsson

Research interests

The focus of my research is contributing to improved understanding of various volcanic and tectonic Earth processes and properties such as magma accumulation, eruptions and intrusions, earthquakes, and plate boundary deformation. I mostly rely on geodetic methods (GNSS, InSAR, tilt, borehole strain), however, I also use other data sources such as seismic, gas, geochemistry, petrology, visual observations, etc., where applicable. Most of my previous work is on volcanic and tectonic processes in Iceland and Central America (see publication list).

For my current (since January 2015) post-doctoral position at ECGS I am studying deformation sources in the Virunga Volcanic Region in Central Africa. In this area (the western branch of the East Africa Rift Zone) the Nubia and Victoria plates are diverging by 2-3 mm per year, and the very active volcanoes Nyiragongo and Nyamulagira are positioned inside the rift valley. My objectives are to use data from the Kivu continuous GNSS network and InSAR time series from the MSBAS algorithm to: investigate long-term inter-eruptive volcanic deformation in the region; model short-term precursory and co-eruptive deformation to understand their sources and interplay; geodetically identify the axis of the Nubia-Victoria plate boundary. A substantial part of my work is also dedicated to developing near-real-time analysis of geodetic data and training of local scientists for improved hazard monitoring of the Kivu area. My work is funded by the Luxembourg Research Fund (AFR) and the Belgium Research Fund (BELSPO – through the GeoRisCA project).


  • 2010-2014: PhD in Geosciences from The Pennsylvania State University.
  • 1999-2002: M.Sc. in Geophysics from University of Iceland.
  • 1996-1999: B.Sc. in Geophysics from University of Iceland.

Career experience

  • 2014 (Aug. – Dec.): Post-doctoral fellow, The Pennsylvania State University.
  • 1999-2011: Geophysicist, Division of Processing and Research, Icelandic Meteorological Office.
  • 1997-1998: Summer-intern at the Icelandic National Energy Authority, Hydrological Department.


  • Weber, J. C., H. Geirsson, J. L. Latchman, K. Shaw, P. La Femina, S. Wdowinski, M. Higgins, C. Churches, and E. Norabuena, 2015. Tectonic inversion in the Caribbean-South American plate boundary: GPS Geodesy, Seismology, and Tectonics of the Mw 6.7 April 22, 1997 Tobago earthquake, Tectonics, 34, doi:10.1002/2014TC003665.
  • Rodgers, M., Roman, D. C., Geirsson, H., LaFemina, P., McNutt, S. R., Munos, A., Tenorio, V., 2015. Stable and unstable phases of elevated seismic activity at the persistently restless Telica Volcano, Nicaragua, Journal of Volcanology and Geothermal Research, 290, 63-74, doi: 10.1016/j.jvolgeores.2014.11.012.
  • Sigmundsson, F., Hooper, A., Hreinsdottir, S., Vogfjord, K. S., Ofeigsson, B. G., Heimisson, E. R., Dumont, S., Parks, M., Spaans, K., Gudmundsson, G. B., Drouin, V., Árnadóttir, Th., Jónsdóttir, K., Gudmundsson, M. T., Högnadóttir, Th., Fridriksdóttir, H. M., Hensch, M., Einarsson, P., Magnússon, E., Samsonov, S., Brandsdóttir, B., White, R. S., Ágústsdóttir, Th., Greenfield, T., Green, R. G., Hjartardóttir, A. R., Pedersen, R., Bennett, R. A., Geirsson, H., LaFemina, P. C., Björnsson, H., Pálsson, F., Sturkell, E., Bean, C. J., Mölhoff, M., Braiden, A. K., Eibl, E. P. S., 2015. Segmented lateral dyke growth in a rifting event at Bardarbunga volcanic system, Iceland. Nature, 517, 191–195, doi: 10.1038/nature14111.
  • Kobayashi, D., P. LaFemina, H. Geirsson, E. Chichaco, A. Abrego, H. Mora-Paez, E. Camacho, 2014. Kinematics of the Western Caribbean: Collision of the Cocos Ridge and Upper Plate Deformation. G-cubed, 15, 1671–1683, doi:10.1002/2014GC005234.
  • Hreinsdottir, S., F. Sigmundsson, M.J. Robserts, H. Bjornsson, R. Grapenthin, Th. Arason, Th. Arnadottir, J. Holmjarn, H. Geirsson, R.A. Bennett, M.T. Gudmundsson, B. Oddsson, B.G. Ofeigsson, T. Villemin, Th. Jonsson, E. Sturkell, A. Hoskuldsson, G. Larsen, Th. Thordarson, B.A. Oladottir, 2014. Volcanic plume height correlated with magma-pressure change at Grimsvotn Volcano, Iceland, Nature Geoscience, doi: 10.1038/ngeo2044M3.
  • Geirsson, H., M. Rodgers, P. LaFemina, M. Witter, D. Roman, A. Munoz, V. Tenorio, J. Alavarez, V. C. Jacobo, D. Nilsson, B. Galle, M. D. Feineman, T. Furman, A. Morales, 2014. Multidisciplinary observations of the 2011 explosive eruption of Telica volcano, Nicaragua: Implications for the dynamics of low-explosivity ash eruptions. J. Volc. Geotherm. Res., 271, 1, 55-69, doi: 10.1016/j.jvolgeores.2013.11.009.
  • Rodgers, M., D. C. Roman, H. Geirsson, P. LaFemina, A. Munoz, C. Guzman, V. Tenorio, 2013. Seismicity accompanying the 1999 eruptive episode at Telica Volcano, Nicaragua. J. Volc. Geotherm. Res., 265, 39-51, doi:10.1016/j.jvolgeores.2013.08.010.
  • Sturkell, E., K. Ágústsson, A. T. Linde, S.I. Sacks, P. Einarsson, F. Sigmundsson, H. Geirsson, R. Pedersen, P. C. LaFemina, H. Ólafsson, 2013. New insights into volcanic activity from strain and other deformation data for the Hekla 2000 eruption. J. Volc. Geotherm. Res., 256, 78-86, doi:10.1016/j.jvolgeores.2013.02.001.
  • Geirsson, H., P. LaFemina, T. Árnadóttir, E. Sturkell, F. Sigmundsson, M. Travis, P. Schmidt, B. Lund, S. Hreinsdóttir, and R. Bennett, 2012. Volcano deformation at active plate boundaries: Deep magma accumulation at Hekla volcano and plate boundary deformation in south Iceland. J. Geophys. Res., 117, B11409, doi:10.1029/2012JB009400.
  • Hooper, A., B. Ófeigsson, F. Sigmundsson, B. Lund, P. Einarsson, H. Geirsson, E. Sturkell, 2011. Increased capture of magma in the crust promoted by ice-cap retreat in Iceland. Nature Geoscience, 4, 783-786, doi:10.1038/NGEO1269.
  • Metzger, S., S. Jónsson, and H. Geirsson, 2011. Locking depth and slip-rate of the Húsavík Flatey fault, North Iceland, derived from continuous GPS data 2006–2010. Geophys. J. Int., 187, 2, 564-576, doi: 10.1111/j.1365-246X.2011.05176.x.
  • Magnusson, E., H. Bjornsson, H. Rott, M.J. Roberts, F. Palsson, S. Gudmundsson, R.A. Bennett, H. Geirsson, E. Sturkell, 2011. Localized uplift of Vatnajökull, Iceland: subglacial water accumulation deduced from InSAR and GPS observations. Journal of Glaciology, 57, 203, 475-484.
  • Sigmundsson, F., S. Hreinsdóttir, A.Hooper, Th. Árnadóttir, R. Pedersen, M. Roberts, N. Óskarsson, A. Auriac, J. Decriem, P. Einarsson, H. Geirsson, M. Hensch, B. Ófeigsson, E. Sturkell, H. Sveinbjörnsson, K.L. Feigl, 2010. Intrusion triggering of the 2010 Eyjafjallajokull explosive eruption. Nature, 468, 426-430, doi:10.1038/nature09558.
  • Sigmundsson, F., V. Pinel, B. Lund, F. Albino, C. Pagli, H. Geirsson, E. Sturkell, 2010. Climate effects on volcanism: Influence on magmatic systems of loading and unloading from ice mass variations with examples from Iceland. Phil. Trans. Roy. Soc. A, Special issue on climate forcing of geological and geomorphological hazards, Philosophical Transactions Royal Society A, 368, 1-16, doi:10.1098/rsta.2010.0042
  • Decriem, J., Th. Árnadóttir, A. Hooper, H.Geirsson, M. Keiding, B.G. Ófeigsson, F. Sigmundsson, S. Hreinsdóttir, P. LaFemina and R. Bennett, 2010. The 29 May 2008 earthquake doublet in SW Iceland, Geophys. J. Int., 181(2), 1128-1146, doi: 10.1111/j.1365-246X.2010.04565.x
  • Sturkell, E., P. Einarsson, F. Sigmundsson, A. Hooper, B.G. Ofeigsson, H. Geirsson and H. Olafsson, 2010. Katla and Eyjafjallajokull Volcanoes. In: Developments in Quaternary Science, eds. A. Schomacker, J. Kruger and K.H. Kjaer, Elsevier, Volume 13, The Myrdalsjokull Ice Cap, Iceland. Glacial processes, sediments and landforms on an active volcano, 5-21, doi:10.1016/S1571-0866(09)01302-5.
  • Geirsson, H., Th. Árnadóttir, S. Hreinsdóttir, J. Decriem, P.C. LaFemina, S. Jónsson, R. A. Bennett, S. Metzger, A. Holland, E. Sturkell, T. Villemin, C. Völksen, F. Sigmundsson, P. Einarsson, M. J. Roberts, H. Sveinbjörnsson, 2010. Overview of results from continuous GPS observations in Iceland from 1995 to 2010. Jökull, vol. 60, p. 3-22.
  • Geirsson, H., Jakobsdóttir, S.S., Guðmundsson, G.B., Roberts, M.J., Decriem, J., 2009. A deep seated magmatic intrusion at Upptyppingar, Iceland, during 2007 and 2008 In: The VOLUME Project, VOLcanoes: Understaning subsurface mass moveMEnt, ed. C.J. Bean, A.K. Braiden, I. Lokmer, F. Martini, G.S. O’Brien. School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
  • Pinel, V., F. Albino, F. Sigmundsson, E. Sturkell, H. Geirsson, P. Einarsson & M. T. Gudmundsson, 2009. Consequences of local surface load variations for volcano monitoring: Application to Katla subglacial volcano, Iceland. In: The VOLUME Project, VOLcanoes: Understaning subsurface mass moveMEnt, ed. C.J. Bean, A.K. Braiden, I. Lokmer, F. Martini, G.S. O’Brien. School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
  • Árnadóttir, Th., B. Lund, W. Jiang, and H. Geirsson, H. Björnsson, P. Einarsson and T. Sigurdsson, 2009. Glacial rebound and plate spreading: Results from the first countrywide GPS observations in Iceland, Geophys. J. Int., 177(2), 691-716, doi: 10.1111/j.1365-246X.2008.04059.x.
  • Hreinsdóttir, S., T. Árnadóttir, J. Decriem, H. Geirsson, A. Tryggvason, R. A. Bennett, and P. LaFemina, 2009. A complex earthquake sequence captured by the continuous GPS network in SW Iceland, Geophys. Res. Lett., 36, L12309, doi:10.1029/2009GL038391.
  • Sturkell, E., P. Einarsson, H. Geirsson, E. Tryggvason, J.G. Moore, and R. Ólafsdóttir, 2009. Precision levelling and geodetic GPS observations performed on Surtsey between 1967 and 2002, Surtsey Research, 12, 39-47.
  • Volksen, C., Th. Arnadottir, H. Geirsson, G. Valsson, 2009. Present day geodynamics in Iceland monitored by a permanent network of continuous GPS stations, Journal of Geodynamics, 48, 279-283, doi: 10.1016/j.jog.2009.09.033.
  • Sturkell, E., F. Sigmundsson, H. Geirsson, H., Ólafsson, Th. Theodórsson, 2008. Multiple volcano deformation sources in a post-rifting period: 1989–2005 behaviour of Krafla, Iceland constrained by levelling, tilt and GPS observations. J. Volc. Geotherm. Res., 177, 405–417, doi:10.1016/j.jvolgeores.2008.06.013.
  • Sturkell, E., Einarsson, P., Roberts, M.J., Geirsson, H., Gudmundsson, M.T., Sigmundsson, F., Pinel, V., Guðmundsson, G.B., Ólafsson, H., & Stefánsson, R., 2008. Seismic and geodetic insights into magma accumulation at Katla subglacial volcano, Iceland: 1999 to 2005. Journal of Geophysical Research, 113, B03212, doi:10.1029/2006JB004851
  • Keiding, M., Árnadóttir, Th., Sturkell, E., & Geirsson, H., 2008. Contemporary strain accumulation along the Reykjanes Peninsula, South Iceland. Geophysical Journal International, 172, 861–872 doi: 10.1111/j.1365-246X.2007.03655.x
  • Jakobsdottir, S.S., M.J. Roberts, G.B. Gudmundsson, H. Geirsson, R. Slunga, 2008. Earthquake swarms at Upptyppingar, North-East Iceland: A sign of magma intrusion? Stud. Geophys. Geod., 52, 513-528, doi: 10.1007/s11200-008-0035-x.
  • Árnadóttir, Th. H. Geirsson, W. Jiang, 2008. Crustal deformation in Iceland: Plate spreading and earthquake deformation. Jökull, 58, 59-74.
  • Pagli, C., F. Sigmundsson, B. Lund, E. Sturkell, H. Geirsson, P. Einarsson, Th. Árnadóttir, 2007. Glacio-isostatic deformation around the Vatnajökull ice cap, Iceland, induced by recent climate warming: GPS observations and Finite Element Modeling. J. Geophys. Res., 112, B8, B08405, doi: 10.1029/2006JB004421.
  • Pinel, V., Sigmundsson, F., Sturkell, E., Geirsson, H., Einarsson, P., Gudmundsson, M.T. & Högnadóttir, T., 2007. Green’s function estimates of Earth response to variable surface loads: Application to deformation of the subglacial Katla volcano, Iceland. Geophysical Journal International, 169, 325–338, doi: 10.1111/j.1365-246X.2006.03267.x
  • Geirsson, H., Th. Árnadóttir, C. Völksen, W. Jiang, E. Sturkell, T. Villemin, P. Einarsson, F. Sigmundsson, R. Stefánsson, 2006. Current plate movements across the Mid-Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland, J. Geophys. Res., 111, B9, B09407, doi: 10.1029/2005JB004092.
  • Sturkell, E., P. Einarsson, F. Sigmundsson, H. Geirsson, H. Olafsson, R. Pedersen, E. de Zeeuw-van Dalfsen, A. L. Linde, I. S. Sacks, and R. Stefansson, 2006. Volcano geodesy and magma dynamics in Iceland, J. Volc. Geotherm. Res., 150, 14-34.
  • Arnadóttir, Th., Jiang, W., Feigl, K.L., Geirsson, H. & Sturkell, E., 2006. Kinematic models of plate boundary deformation in southwest Iceland derived from GPS observations. Journal of Geophysical Research, 111, B07402, doi:10.1029/2005JB003907.
  • Grapenthin, R., F. Sigmundsson, H. Geirsson, Þ. Árnadóttir, V. Pinel, 2006. Icelandic rhythmics: Annual modulation of land elevation and plate spreading by snow load. Geophysical Research Letters, 33(24), L24305, doi: 10.1029/2006GL028081.
  • Hjaltadottir, S., H. Geirsson, Th. Skaftadottir, 2005. Seismic activity in Iceland during 2004. Jokull, 55, 107-119.
  • Vogfjörð, K. S., S. S. Jakobsdóttir, G. B. Guðmundsson, M. J. Roberts, K. Ágústsson, Þ. Arason, H. Geirsson, S. Karlsdóttir, S. Hjaltadóttir, U. Ólafsdóttir, B. S. Þorbjarnardóttir, Þ. Skaftadóttir, E. Sturkell, E. B. Jónasdóttir, G. Hafsteinsson, H. Sveinbjörnsson, R. Stefánsson, Þ. V. Jónsson, 2005. Forecasting and monitoring a subglacial eruption in Iceland. EOS transactions, 86(26), 245, 248.
  • Arnadottir, Th., H. Geirsson, P. Einarsson, 2004. Coseismic stress changes and crustal deformation on the Reykjanes Peninsula due to triggered earthquakes on 17 June 2000. J. Geophys. Res., 109, B09307, doi: 10.1029/2004JB003130.
  • Sturkell, E., P. Einarsson, F. Sigmundsson, S. Hreinsdóttir, H. Geirsson, 2003. Deformation of Grímsvötn volcano, Iceland: 1998 eruption and subsequent inflation. Geophysical Research Letters, 30,4, 1182, doi:10.1029/2002GL016460.