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Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland

Abstract

Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long1. Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens2,3,4, or magma flowing vertically into dykes from an underlying source5,6, with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bárðarbunga volcanic system grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning System (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of magnitude M > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.

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Figure 1: Overview of data.
Figure 2: Seismicity and magma volume along the dyke, 16 August to 6 September 2014.
Figure 3: Dyke model.
Figure 4: Seismicity and volume change.

References

  1. 1

    Wright, T. J. et al. Geophysical constraints on the dynamics of spreading centres from rifting episodes on land. Nature Geosci. 5, 242–250 (2012)

    ADS  CAS  Google Scholar 

  2. 2

    Einarsson, P. & Brandsdottir, B. Seismological evidence for lateral magma intrusion during the July 1978 deflation of the Krafla volcano in NE-Iceland. J. Geophys. 47, 160–165 (1980)

    Google Scholar 

  3. 3

    Buck, W. R., Einarsson, P. & Brandsdottir, B. Tectonic stress and magma chamber size as controls on dike propagation: constraints from the 1975–1984 Krafla rifting episode. J. Geophys. Res. 111, B12404, http://dx.doi.org/10.1029/2005JB003879 (2006)

    ADS  Google Scholar 

  4. 4

    Belachew, M. et al. Comparison of dike intrusions in an incipient seafloor-spreading segment in Afar, Ethiopia: seismicity perspectives. J. Geophys. Res. 116 (B6), B06405, http://dx.doi.org/10.1029/2010JB007908 (2011)

    ADS  Google Scholar 

  5. 5

    Gudmundsson, A. Infrastructure and mechanics of volcanic systems in Iceland. J. Volcanol. Geotherm. Res. 64, 1–22 (1995)

    ADS  CAS  Google Scholar 

  6. 6

    Hartley, M. E. & Thordarson, T. The 1874–1876 volcano-tectonic episode at Askja, North Iceland: lateral flow revisited. Geochem. Geophys. Geosyst. 14, 2286–2309 (2013)

    ADS  Google Scholar 

  7. 7

    Segall, P. Earthquake and Volcano Deformation (Princeton Univ. Press, 2009)

    Google Scholar 

  8. 8

    Segall, P., Llenos, A. L., Yun, S.-H., Bradley, A. M. & Syracuse, E. M. Time-dependent dike propagation from joint inversion of seismicity and deformation data. J. Geophys. Res. Solid Earth 118, 5785–5804 (2013)

    ADS  Google Scholar 

  9. 9

    Björnsson, H. Hydrology of Ice Caps in Volcanic Regions Vol. 45 (Societas Scientarium Islandica, 1988)

    Google Scholar 

  10. 10

    Gudmundsson, M. T. & Högnadóttir, T. Volcanic systems and calderas in the Vatnajökull region, central Iceland, constraints on crustal structure from gravity data. J. Geodyn. 43, 153–169 (2007)

    Google Scholar 

  11. 11

    Björnsson, H. & Einarsson, P. Volcanoes beneath Vatnajökull, Iceland: evidence from radio-echo sounding, earthquakes and jökulhlaups. Jökull 40, 147–168 (1990)

    Google Scholar 

  12. 12

    Thordarson, T. & Larsen, G. Volcanism in Iceland in historical time: volcano types, eruption styles and eruptive history. J. Geodyn. 43, 118–152 (2007)

    Google Scholar 

  13. 13

    Einarsson, P. et al. Center of the Iceland hotspot experiences volcanic unrest. Eos 78, 369–375 (1997)

    ADS  Google Scholar 

  14. 14

    Pagli, C. et al. Crustal deformation associated with the 1996 Gjálp subglacial eruption, Iceland: InSAR studies in affected areas adjacent to the Vatnajökull ice cap. Earth Planet. Sci. Lett. 259, 24–33 (2007)

    ADS  CAS  Google Scholar 

  15. 15

    Reddy, J. N. An Introduction to Continuum Mechanics (Cambridge Univ. Press, 2013)

    Google Scholar 

  16. 16

    Dahm, T. Numerical simulations of the propagation path and arrest of fluid-filled fractures in the Earth. Geophys. J. Int. 141, 623–638 (2000)

    ADS  Google Scholar 

  17. 17

    Maccaferri, F., Bonafede, M. & Rivalta, E. A quantitative study of the mechanisms governing dike propagation, dike arrest and sill formation. J. Volcanol. Geotherm. Res. 208, 39–50 (2011)

    ADS  CAS  Google Scholar 

  18. 18

    Fialko, Y. A. & Rubin, A. What controls the along-strike slopes of volcanic rift zones? J. Geophys. Res. 104, 20007–20020 (1999)

    ADS  Google Scholar 

  19. 19

    Toda, S., Stein, R. S. & Sagiya, T. Evidence from the AD 2000 Izu islands earthquake swarm that stressing rate governs seismicity. Nature 419, 58–61 (2002)

    ADS  CAS  PubMed  Google Scholar 

  20. 20

    Staudacher, T. et al. The April 2007 eruption and the Dolomieu crater collapse, two major events at Piton de la Fournaise (La Réunion Island, Indian Ocean). J. Volcanol. Geotherm. Res. 184, 126–137 (2009)

    ADS  CAS  Google Scholar 

  21. 21

    Böðvarsson, R., Rögnvaldsson, S. T., Slunga, R. & Kjartansson, E. The SIL Data Acquisition System — At Present and Beyond Year 2000 (Report VÍ-R98005-JA04, Icelandic Meteorological Office, 1998)

    Google Scholar 

  22. 22

    Slunga, R., Rögnvaldsson, S. Th. & Bödvarsson, R. Absolute and relative locations of similar events with application to microearthquakes in southern Iceland. Geophys. J. Int. 123, 409–419 (1995)

    ADS  Google Scholar 

  23. 23

    Stefánsson, R. et al. Earthquake prediction research in the South Iceland seismic zone and the SIL project. Bull. Seismol. Soc. Am. 83, 696–716 (1993)

    Google Scholar 

  24. 24

    Darbyshire, F. A., Bjarnason, I. Th., White, R. S. & Flóvenz, Ó. G. Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile. Geophys. J. Int. 135, 1131–1149 (1998)

    ADS  Google Scholar 

  25. 25

    Lomax, A., Virieux, J. J., Volant, P. & Berge, C. in Advances in Seismic Event Location (eds Thurber, C. H. & Rabinowitz, N. ) 101–134 (Kluwer, Amsterdam, 2000)

    Google Scholar 

  26. 26

    Rögnvaldsson, S. T. & Slunga, R. R. Routine fault plane solutions for local networks: a test with synthetic data. Bull. Seismol. Soc. Am. 83, 1232–1247 (1993)

    Google Scholar 

  27. 27

    Herring, T., King, R. W. & McCluskey, S. M. Introduction to GAMIT/GLOBK Release 10.4 (Massachusetts Institute of Technology Technical Report, Cambridge, 2010)

    Google Scholar 

  28. 28

    Rosen, P. A., Henley, S., Peltzer, G. & Simons, M. Updated repeat orbit interferometry package released. Eos Trans. AGU 85, 47 (2004)

    ADS  Google Scholar 

  29. 29

    Kampes, B. Delft Object-oriented Radar Interferometric Software: User’s Manual and Technical Documentation v4.02 (Delft Technical University, 1999)

    Google Scholar 

  30. 30

    Werner, C. et al. Gamma SAR and interferometric processing software. Proc. ERS-ENVISAT Symp Vol. 461 (European Space Agency Special Publication, 2000)

  31. 31

    Jóhannesson, T. et al. Ice-volume changes, bias-estimation of mass-balance measurements and changes in subglacial water bodies derived by LiDAR-mapping of the surface of Icelandic glaciers. Ann. Glaciol. 54, 63–74 (2013)

    ADS  Google Scholar 

  32. 32

    Magnússon, E., Björnsson, H., Dall, J. & Pálsson, F. Volume changes of Vatnajökull ice cap, Iceland, due to surface mass balance, ice flow, and subglacial melting at geothermal areas. Geophys. Res. Lett. 32, L05504, http://dx.doi.org/10.1029/2004GL021615 (2005)

    ADS  Google Scholar 

  33. 33

    Goldstein, R. R. & Werner, C. Radar interferogram filtering for geophysical applications. Geophys. Res. Lett. 25, 4035–4038 (1998)

    ADS  Google Scholar 

  34. 34

    Goldstein, R., Zebker, H. & Werner, C. Satellite radar interferometry-two-dimensional phase unwrapping. Radio Sci. 23, 713–720 (1988)

    ADS  Google Scholar 

  35. 35

    Chen, C. W. & Zebker, H. A. Two-dimensional phase unwrapping with use of statistical models for cost functions in nonlinear optimization. J. Opt. Soc. Am. 18, 338–351 (2001)

    ADS  CAS  Google Scholar 

  36. 36

    Decriem, J. et al. The 2008 May 29 earthquake doublet in SW Iceland. Geophys. J. Int. 181, 1128–1146 (2010)

    ADS  Google Scholar 

  37. 37

    Okada, Y. Internal deformation due to shear and tensile faults in a half-space. Bull. Seismol. Soc. Am. 82, 1018–1040 (1992)

    Google Scholar 

  38. 38

    Fialko, Y., Khazan, Y. & Simons, M. Deformation due to a pressurized horizontal circular crack in an elastic half-space, with applications to volcano geodesy. Geophys. J. Int. 146, 181–190 (2001)

    ADS  Google Scholar 

  39. 39

    Mogi, K. Relations between the eruptions of various volcanoes and the deformations of the ground surfaces around them. Bull. Earthq. Res. Inst. Univ. Tokyo 36, 99–134 (1958)

    Google Scholar 

  40. 40

    Hooper, A. et al. Increased capture of magma in the crust promoted by ice-cap retreat in Iceland. Nature Geosci. 4, 783–786 (2011)

    ADS  CAS  Google Scholar 

  41. 41

    Mosegaard, K. & Tarantola, A. Monte Carlo sampling of solutions to inverse problems. J. Geophys. Res. 100, 12431–12447 (1995)

    ADS  Google Scholar 

  42. 42

    Hooper, A. et al. Importance of horizontal seafloor motion on tsunami height for the 2011 Mw = 9.0 Tohoku-Oki earthquake. Earth Planet. Sci. Lett. 361, 469–479 (2013)

    ADS  CAS  Google Scholar 

  43. 43

    Árnadóttir, T., Jiang, W., Feigl, K. L., Geirsson, H. & Sturkell, E. Kinematic models of plate boundary deformation in southwest Iceland derived from GPS observations. J. Geophys. Res. 111, B07402, http://dx.doi.org/10.1029/2005JB003907 (2006)

    ADS  Google Scholar 

  44. 44

    Sturkell, E. & Sigmundsson, F. Continuous deflation of the Askja caldera Iceland, during the 1983-1998 non-eruptive period. J. Geophys. Res. 105, 25671–25684 (2000)

    ADS  Google Scholar 

  45. 45

    Delaney, P. T. & McTigue, D. F. Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kilauea volcano. Bull. Volcanol. 56, 417–424 (1994)

    ADS  Google Scholar 

  46. 46

    Jóhannesson, H. & Sæmundsson, K. Geological Map of Iceland, Tectonics 1:600.000 (Icelandic Institute of Natural History, 2009)

    Google Scholar 

  47. 47

    Gudmundsson, M. T., Högnadóttir, Þ., Kristinsson, A. B. & Gudbjörnsson, S. Geothermal activity in the subglacial Katla caldera, Iceland, 1999-2005, studied with radar altimetry. Ann. Glaciol. 45, 66–72 (2007)

    ADS  Google Scholar 

  48. 48

    Yun, S., Segall, P. & Zebker, H. Constraints on magma chamber geometry at Sierra Negra Volcano, Galápagos Islands, based on InSAR observations. J. Volcanol. Geotherm. Res. 150, 232–243 (2006)

    ADS  CAS  Google Scholar 

Download references

Acknowledgements

Support for this work was received from the European Community’s Seventh Framework Programme Grant No. 308377 (Project FUTUREVOLC), the Icelandic Research Fund (Project Volcano Anatomy), the Research Fund at the University of Iceland, NERC, the Geological Survey of Ireland and the US National Science Foundation (NSF). COSMO-SkyMed data were provided by the Italian Space Agency (ASI) and TerraSAR-X data by the German Space Agency (DLR) through the Icelandic Volcanoes Supersite project supported by the Committee on Earth Observing Satellites (CEOS). RADARSAT-2 data were provided by the Canadian Space Agency and MDA Corporation. Natural Resources Canada Earth Sciences Sector contribution number 20140314. An intermediate TanDEM-X digital elevation model was provided by DLR under project IDEM_GEOL0123. We thank the following key persons for help with instrumentation and data: B. H. Bergsson, Þ. Jónsson, V. H. Kjartansson, S. Steinþórsson, P. Erlendsson, H. Ólafsson, J. Söring and D. Craig. We also acknowledge the many others who have contributed to GPS, seismic and other field work in the study area. For GPS equipment and support, we acknowledge services provided by the UNAVCO Facility with support from the US NSF and National Aeronautics and Space Administration (NASA) under NSF Cooperative Agreements Nos EAR-0735156 and EAR-0711446. S. Jónsson (KAUST, Saudi Arabia) and T. Villemin (EDYTEM, Université de Savoie, France) also provided support to GPS. Seismic equipment: The British Geological Survey donated several of the broadband seismic sensors around Vatnajökull. We thank the SEISUK facility for loans to R.S.W. of seismometers under loan 980. Landsvirkjun contributed GPS instruments and seismic sensors north of Vatnajökull. The surveying aeroplane of Isavia (Icelandic Aviation Operation Services) mapped the subsidence of Bárðarbunga. The Icelandic Coast Guard provided aeroplane and helicopter support for field studies.

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Contributions

The writing of the paper, and the research it is based on, was coordinated by F.S., A.H., S.H., K.S.V., B.G.Ó. and other members of Icelandic Meteorological Office (IMO) seismic monitoring team. All authors contributed ideas and input to the research and writing of the paper. Modelling of geodetic data was done by A.H., E.R.H. and Th.A. Analysis and operation of continuous GPS sites were carried out by S.H., B.G.Ó., H.M.F, R.A.B., V.D., H.G. and P.C.L. Relative earthquake locations were calculated by K.S.V., seismic data presentation and relative locations were by G.B.G., focal mechanisms were determined by M.H. and single earthquake location determination was led by K.J. and SIL seismic monitoring group. Interferometric analysis was carried out by S.D., K.S., M.P., V.D. and S.S., with a composite digital elevation model prepared by E.M. The combined strain and gravity potential in relation to the dyke propagation was modelled by E.R.H. in consultation with A.H. and F.S. Campaign GPS measurements were carried out by S.D., V. D., M.P., Á.R.H., E.S., F.S. and others. M.T.G. and Th.H. mapped the collapse of the Bárðarbunga caldera and the formation of ice cauldrons over the path of the dyke with aircraft radar profiling. Á.R.H., E.M. and P.E. led mapping of graben formed and of the eruptive fissure as shown here. P.E., B.B. and R.P. contributed to the interpretation of events, and H.B. and F.P. provided bedrock topography and ice thickness for Vatnajökull ice cap. R.S.W., Th.Á., T.G., R.G.G., C.J.B., M.M., A.K.B. and E.P.S.E. contributed and analysed seismic data.

Corresponding author

Correspondence to Freysteinn Sigmundsson.

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Extended data figures and tables

Extended Data Figure 1 Tectonic map showing seismic and geodetic stations.

Filled uptriangles correspond to continuous GPS stations, open triangles to campaign GPS sites, filled downtriangles correspond to seismic stations, and black ‘stars’ correspond to co-located GPS and seismic stations. Station names for GPS are indicated with four upper-case letters and for seismic stations with three lower-case letters. The different tracks for SAR satellite data are plotted with solid lines for RADARSAT-2, dashed lines for COSMO-SkyMed (CSK) and dotted lines for TerraSAR-X (TSX). Orbit numbers are indicated for CSK and TSX. The red stars correspond to the 2014 eruptive fissures at Holuhraun. Background map shows ice caps (white), central volcanoes (dotted lines), calderas (hatched lines) and fissure swarms (grey shading)46. Names of selected volcanoes are shown, and T indicates Tungnafellsjökull central volcano. Inset, locations of the Eastern Volcanic Zone (EVZ), the Western Volcanic Zone (WVZ), the Northern Volcanic Zone (NVZ) and the South Iceland Seismic Zone (SISZ), with their fissure swarms and central volcanoes; box shows area of the main figure.

Extended Data Figure 2 Map and table of dyke segments defined by seismicity.

a, Location of dyke segments (red lines labelled with numbers) delineated by relatively relocated earthquakes. The triangles show locations of the nearest seismic stations used to locate the events. Green, stations operated by the Icelandic Meteorological Office (IMO); blue, station operated by the University of Cambridge; and red, station operated by University College Dublin. The two stations on the ice are joint IMO and University of Cambridge stations. All stations telemetered data to IMO. Also shown are ice cauldrons formed (circles), outline of lava flow mapped from radar image on 6 September, and boundaries of graben activated in the dyke distal area (hatched lines). b, The dyke segments. Columns show segment number (Nr), latitude and longitude of beginning (Lat1, Lon1) and end points (Lat2, Long2) of each segment, segment length (L), depth range (D), strike, dip, the RMS value of the deviation (in metres) of the earthquakes from the plane they define, and the number of earthquakes used to define each dyke segment plane (#Eq).

Extended Data Figure 3 Subsidence at Bárðarbunga volcano revealed by aeroplane radar profiling.

Blue contours show the elevation of the ice surface in the Bárðarbunga caldera on 5 September 2014, about three weeks after the onset of unrest. The data were obtained using aircraft flown 100–150 m above glacier surface, using radar altimetry and submetre differential GPS Omnistar. The system provides 2 m absolute accuracy of surface elevation along the survey profiles47, shown as black dotted lines. The subsidence relative to the pre-unrest ice surface is indicated with coloured shading (key at right). It is greatest in the central part of the caldera, where it had a maximum of 16 m.

Extended Data Figure 4 Geodetic model with a contracting point pressure source, a two-segment-dyke and no a priori constraints.

The dyke segments are rectangular with uniform opening37 and the model shown is that with maximum probability. Free parameters are: position and volume change of the point pressure source39, and position, strike, dip and opening of the dyke. The panels show from left to right: data (a, d, g), model (b, e, h) and residuals (c, f, i). GPS data in all panels span 15 August to 4 September 2014. The top row shows an interferogram spanning 6 July 2012 to 4 September 2014; the middle row shows an interferogram spanning 2 August to 3 September 2014; the bottom row shows the data from Extended Data Fig. 3 from aeroplane radar profiling, but these data were not used to constrain the model.

Extended Data Figure 5 Geodetic model with a contracting point pressure source, two caldera faults, and a four-segment dyke.

The dyke is divided into multiple rectangular patches37 and the model shown is that with maximum probability. Lateral dyke position is fixed from relocated seismicity. Position of the point source and faults, volume change of the point source and opening and strike-slip of the dyke are free parameters. Left column (a, d, g), data; middle column (b, e, h), model; right column (c, f, i), residuals. The data are detailed in Extended Data Fig. 4 and all of the data were used to constrain the model.

Extended Data Figure 6 Geodetic model with a contracting flat-topped chamber, two caldera faults, and a four-segment dyke.

A deflating penny-shaped crack38 is used to represent the top of a flat-topped chamber48, and the dyke is divided into multiple rectangular patches37. The model shown is that with maximum probability. Lateral dyke position is fixed from relocated seismicity. Position of the crack and faults, volume change and radius of the crack and opening and strike-slip of the dyke are free parameters. Left column (a, d, g), data; middle column (b, e, h), model; right column (c, f, i), residuals. The data are detailed in Extended Data Fig. 4 and all of the data were used to constrain the model.

Extended Data Figure 7 Path of dyke propagation from energy considerations.

ah, Energy profiles for dyke segments 1, 2, 3, 4, 5, 6, 7a and 8a, as described in Fig. 3b. Blue lines indicate the strain energy potential change as a function of the strike, and the red lines the gravitational potential change. Green is the total potential energy change. Energy is shown in terajoules (1012 J). The lowest point on each energy curve is defined as 0 TJ. Error bars, 1 s.d. of the error in the numerical integration.

Extended Data Figure 8 Topography, earthquake depths, and lithostatic pressure along the dyke path.

a, Bedrock (brown line) and ice topography (light blue line) along the dyke path. b, Depth of earthquake hypocentres (grey dots) below sea level projected on the dyke segments and lines (red) of constant lithostatic pressure, assuming constant crustal density of 2,800 kg m−3 and ice density of 920 kg m−3. Line spacing corresponds to 25 MPa. c, Lithostatic pressure at sea level calculated along dyke segments 1, 2, 3, 4, 5, 6, 7a, 8a and 8b (blue line). The calculations take into account both the subglacial bedrock topography and ice thickness. Light blue triangles indicate the beginning of a segment and red triangles the end of a segment. It is assumed that between segments the dyke propagates along a straight path. Dyke propagation was halted for the longest time at the end of segment 4 (see Figs 2 and 4), before an increase in lithostatic pressure.

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Sigmundsson, F., Hooper, A., Hreinsdóttir, S. et al. Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland. Nature 517, 191–195 (2015). https://doi.org/10.1038/nature14111

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