title: 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 long. Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens, or magma flowing vertically into dykes from an underlying source, 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.
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Freysteinn
authors.initials: F
authors.lastname: Sigmundsson
authors.affiliation: Centre for the Observation and Modelling of Earthquakes and Tectonics (COMET), School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hooper
authors.affiliation: GNS Science, PO Box 30368, Lower Hutt 5040, New Zealand.
authors.forename: Sigrún
authors.initials: S
authors.lastname: Hreinsdóttir
authors.affiliation: Icelandic Meteorological Office, IS-150 Reykjavík, Iceland.
authors.forename: Kristín S
authors.initials: KS
authors.lastname: Vogfjörd
authors.affiliation: Icelandic Meteorological Office, IS-150 Reykjavík, Iceland.
authors.forename: Benedikt G
authors.initials: BG
authors.lastname: Ófeigsson
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Elías Rafn
authors.initials: ER
authors.lastname: Heimisson
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Dumont
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Michelle
authors.initials: M
authors.lastname: Parks
authors.affiliation: Centre for the Observation and Modelling of Earthquakes and Tectonics (COMET), School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Karsten
authors.initials: K
authors.lastname: Spaans
authors.affiliation: Icelandic Meteorological Office, IS-150 Reykjavík, Iceland.
authors.forename: Gunnar B
authors.initials: GB
authors.lastname: Gudmundsson
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Vincent
authors.initials: V
authors.lastname: Drouin
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Thóra
authors.initials: T
authors.lastname: Árnadóttir
authors.affiliation: Icelandic Meteorological Office, IS-150 Reykjavík, Iceland.
authors.forename: Kristín
authors.initials: K
authors.lastname: Jónsdóttir
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Magnús T
authors.initials: MT
authors.lastname: Gudmundsson
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Thórdís
authors.initials: T
authors.lastname: Högnadóttir
authors.affiliation: 1] Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland [2] Icelandic Meteorological Office, IS-150 Reykjavík, Iceland.
authors.forename: Hildur María
authors.initials: HM
authors.lastname: Fridriksdóttir
authors.affiliation: Icelandic Meteorological Office, IS-150 Reykjavík, Iceland.
authors.forename: Martin
authors.initials: M
authors.lastname: Hensch
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Páll
authors.initials: P
authors.lastname: Einarsson
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Eyjólfur
authors.initials: E
authors.lastname: Magnússon
authors.affiliation: Canada Centre for Mapping and Earth Observation, Natural Resources Canada, 560 Rochester Street, Ottawa, Ontario K1A 0E4, Canada.
authors.forename: Sergey
authors.initials: S
authors.lastname: Samsonov
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Bryndís
authors.initials: B
authors.lastname: Brandsdóttir
authors.affiliation: Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK.
authors.forename: Robert S
authors.initials: RS
authors.lastname: White
authors.affiliation: Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK.
authors.forename: Thorbjörg
authors.initials: T
authors.lastname: Ágústsdóttir
authors.affiliation: Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Greenfield
authors.affiliation: Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Green
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Ásta Rut
authors.initials: ÁR
authors.lastname: Hjartardóttir
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Rikke
authors.initials: R
authors.lastname: Pedersen
authors.affiliation: Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bennett
authors.affiliation: Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Halldór
authors.initials: H
authors.lastname: Geirsson
authors.affiliation: Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Peter C
authors.initials: PC
authors.lastname: La Femina
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Helgi
authors.initials: H
authors.lastname: Björnsson
authors.affiliation: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavík, Iceland.
authors.forename: Finnur
authors.initials: F
authors.lastname: Pálsson
authors.affiliation: Department of Earth Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Sturkell
authors.affiliation: Seismology Laboratory, School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bean
authors.affiliation: Seismology Laboratory, School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Martin
authors.initials: M
authors.lastname: Möllhoff
authors.affiliation: Seismology Laboratory, School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Aoife K
authors.initials: AK
authors.lastname: Braiden
authors.affiliation: Seismology Laboratory, School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Eva P S
authors.initials: EP
authors.lastname: Eibl