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34 results on '"Nordic Volcanological Center, Institute of Earth Sciences"'

1. Smectite quantification in hydrothermally altered volcanic rocks

Author

Thráinn Fridriksson, Nicolas Marino, Bernard Fraisse, Bruno Lanson, Benoit Gibert, Nathaniel Findling, Léa Lévy, Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, 101 Reykjavík, Iceland, ÍSOR - Iceland GeoSurvey, Reykjavík, Iceland, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie, Ecole Normale Supérieure, Paris Sciences et Lettres, CNRS, Paris, France, Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de géologie de l'ENS (LGE), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Grenoble Alpes (UGA)-Université Gustave Eiffel-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2), Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), University of Iceland [Reykjavik], Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)

Subjects
0211 other engineering and technologies, Mineralogy, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Fraction (chemistry), 02 engineering and technology, 010502 geochemistry & geophysics, 01 natural sciences, Hydrothermal circulation, Electrical resistivity and conductivity, Cation-exchange capacity, 021108 energy, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Renewable Energy, Sustainability and the Environment, Chemistry, Geology, Geotechnical Engineering and Engineering Geology, Volcanic rock, Volcano, Clay minerals, Mass fraction, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract

International audience; In volcanic environments, the presence of smectite may indicate recent hydrothermal circulations. Smectite is also responsible for enhanced rock electrical conductivity, as well as mechanical weakening. Therefore, 1 quantifying smectite is important in geothermal exploration. Smectite identification requires X-ray diffraction (XRD) but quantification based on XRD is time-consuming and not always accurate. In the present study, we investigate the use of an optimized unbuffered Cation Exchange Capacity (CEC) measurement, by back-titration of the Coppertriethylenetetramine(II) "Cu-trien" molecule, to quantify the smectite content of altered volcanic rock samples. We establish that a satisfying trade-off between the instrument uncertainty and an independant systematic error is theoretically reached for a fraction of reactants consumed of about 30% at the end of the exchange reaction. We suggest a modification to classical protocols to fall in that range. Finally, we show that optimized CEC measurements by Cu-trien are a direct measure of the smectite weight fraction in altered volcanic samples, with an average CEC of pure smectite of 90 ± 5 meq/100g.

Published
2020
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2. Magmatic cycles pace tectonic and morphological expression of rifting (Afar depression, Ethiopia)

Author

S. Medynski, R. Pik, P. Burnard, S. Dumont, R. Grandin, A. Williams, P.-H. Blard, I. Schimmelpfennig, C. Vye-Brown, L. France, D. Ayalew, L. Benedetti, G. Yirgu, Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), British Geological Survey (BGS), BGS, School of Earth Sciences [Addis Ababa], Addis Ababa University (AAU), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Lorraine (UL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)

Subjects
Dike, 010504 meteorology & atmospheric sciences, Volcanism, Fault (geology), cosmogenic isotopes, 010502 geochemistry & geophysics, Fault scarp, 01 natural sciences, Afar, Paleontology, Divergent boundary, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Earth and Planetary Sciences (miscellaneous), [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, geography.geographical_feature_category, Rift, tecto-magmatic processes, Mid-ocean ridge, Crust, Geophysics, Space and Planetary Science, Geology, Seismology
Abstract

International audience; The existence of narrow axial volcanic zones of mid-oceanic ridges testifies of the underlying concentration of both melt distribution and tectonic strain. As a result of repeated diking and faulting, axial volcanic zones therefore represent a spectacular topographic expression of plate divergence. However, the submarine location of oceanic ridges makes it difficult to constrain the interplay between tectonic and magmatic processes in time and space. In this study, we use the Dabbahu–Manda Hararo (DMH) magmatic rift segment (Afar, Ethiopia) to provide quantitative constraints on the response of tectonic processes to variations in magma supply at divergent plate boundaries. The DMH magmatic rift segment is considered an analogue of an oceanic ridge, exhibiting a fault pattern, extension rate and topographic relief comparable to intermediate-to slow-spreading ridges. Here, we focus on the northern and central parts of DMH rift, where we present quantitative slip rates for the past 40 kyr for major and minor normal fault scarps in the vicinity of a recent (September 2005) dike intrusion. The data obtained show that the axial valley topography has been created by enhanced slip rates that occurred during periods of limited volcanism, suggestive of reduced magmatic activity, probably in association with changes in strain distribution in the crust. Our results indicate that the development of the axial valley topography has been regulated by the lifetimes of the magma reservoirs and their spatial distribution along the segment , and thus to the magmatic cycles of replenishment/differentiation (

Published
2016
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3. Volcanic plume height correlated with magma-pressure change at Grímsvötn Volcano, Iceland

Author

Hreinsdóttir, Sigrún, Sigmundsson, Freysteinn, Roberts, Matthew, Björnsson, Halldór, Grapenthin, Ronni, Arason, Pórdur, Árnadóttir, Thóra, Hólmjárn, Jósef, Geirsson, Halldór, Bennett, Richard, Gudmundsson, Magnús, Oddsson, Björn, Ófeigsson, Benedikt, Villemin, Thierry, Jónsson, Thorsteinn, Sturkell, Erik, Höskuldsson, Ármann, Larsen, Gudrún, Thordarson, Thor, Óladóttir, Bergrún Arna, University of Iceland [Reykjavik], Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Department of Agricultural & Food Economics, University of Reading (UOR), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [Gothenburg], University of Gothenburg (GU), and Referent HAL Edytem, Christine Maury

Subjects
[SDE.BE] Environmental Sciences/Biodiversity and Ecology, [SDE.MCG] Environmental Sciences/Global Changes, [SDE.IE]Environmental Sciences/Environmental Engineering, [SHS.GEO] Humanities and Social Sciences/Geography, [SDE.MCG]Environmental Sciences/Global Changes, [SDE.IE] Environmental Sciences/Environmental Engineering, [SDE.ES] Environmental Sciences/Environmental and Society, [SHS.GEO]Humanities and Social Sciences/Geography, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, [SDE.ES]Environmental Sciences/Environmental and Society
Abstract

International audience; 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 source(1). The height of the volcanic plumes during explosive eruptions also varies with magma flow rate, in a nonlinear way(2,3). In May 2011, an explosive eruption at Grimsvotn Volcano, Iceland, erupted about 0.27 km(3) 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 Grimsvotn 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.

Published
2014

4. Multiple effects of ice load changes and associated stress change on magmatic systems

Author

Freysteinn Sigmundsson, Andrew Hooper, Virginie Pinel, Peter Schmidt, Carolina Pagli, Fabien Albino, Björn Lund, Pinel, Virginie, McGuire, W. J. & Maslin, M. A, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Department of Earth Sciences [Uppsala], Uppsala University, Institut des Sciences de la Terre (ISTerre), Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Delft Institute of Earth Observation and Space Systems, Delft University of Technology (TU Delft), Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, McGuire, W. J. & Maslin, M. A, Institute of Earth Science, Reykjavik, and Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
ice load, 010504 meteorology & atmospheric sciences, Earth science, [SDE.MCG]Environmental Sciences/Global Changes, magma stress, glacial unloading, crust/mantle, magma geometry, Geophysics, 010502 geochemistry & geophysics, 01 natural sciences, Stress change, [SDE.MCG] Environmental Sciences/Global Changes, 13. Climate action, [SDU.STU.VO] Sciences of the Universe [physics]/Earth Sciences/Volcanology, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Geology, 0105 earth and related environmental sciences
Abstract

Ice retreat on volcanoes reduces pressure at the surface of the Earth and induces stress changes in magmatic systems. The consequences can include increased generation of magma at depth, increased magma capture in the crust, and modification of failure conditions of magma chambers. We review the methodology to evaluate each of these effects, and consider the influence of ongoing ice retreat on volcanoes at the Mid-Atlantic divergent plate boundary in Iceland. Evaluation of each of these effects requires a series of assumptions regarding the rheology of the crust and mantle, and the nature of magmatic systems, contributing to relatively large uncertainty in response of a magmatic system to climate warming and associated ice retreat. Pressure release melting due to ice cap retreat in Iceland may at present times generate a similar amount of magma as plate tectonic processes; larger than realized previously. However, new modelling shows that part of this magma may be captured in the crust, rather than being erupted. Gradual retreat of ice caps do steadily modify failure conditions at magma chambers, which is highly dependent on their geometry and depth, as well as the details of ice load variations. A model is presented where long-term ice retreat at Katla volcano decreases the likelihood of eruption, as more magma is needed in the magma chamber to cause failure than in the absence of the ice retreat.

Published
2013

5. Influence of surface load variations on eruption likelihood: application to two Icelandic subglacial volcanoes, Grímsvötn and Katla

Author

Fabien Albino, Freysteinn Sigmundsson, Virginie Pinel, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Magma chamber, and modelling, 010504 meteorology & atmospheric sciences, processes, Outburst flood, Induced seismicity, 010502 geochemistry & geophysics, Mechanics, 01 natural sciences, Numerical solutions, Geochemistry and Petrology, Caldera, Glacial period, Magma chamber processes, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, theory, Volcano, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Volcano/climate interactions, Snow, Geophysics, 13. Climate action, Magma, climate interactions, Geology, Seismology
Abstract

SUMMARY We investigate how surface load variations around volcanoes act on shallow magma chambers. Numerical calculations are carried out in axisymmetric geometry for an elliptical chamber embedded in an elastic medium. Magma compressibility is taken into account. For variable chamber shape, size and depth, we quantify how unloading events induce magmatic pressure change as well as variation of the threshold pressure required for dyke initiation at the chamber wall. We evaluate the triggering effect of these surface events on onset of eruptions and find it depends strongly on the surface load location and the magma chamber shape. We apply this model to two active Icelandic subglacial volcanoes: Gr´ omsv¨ otn and Katla. The 2004 eruption of Gr´ omsv¨ otn was immediately preceded by a j¨ okulhlaup, a glacial outburst flood of 0.5 km 3 . We show that this event may have triggered the eruption only if the system was very close to failure conditions. Katla volcano is covered by the M´ yrdalsj¨ okull ice cap. An annual cycle, with up to 6 m change in snow thickness, occurs from winter to summer. As the seasonal snow load is reduced, a pressure decrease of the same order of magnitude as the load is induced within the magma storage zone. Our model predicts that, in the case of a spherical or horizontally elongated magma chamber, eruptions are more likely when the snow cover is smallest, which appears consistent with the fact that all the last nine major historical eruptions at Katla occurred during the summer period. The model predicts an increase in Coulomb stress around the caldera, up to 7 km from its centre, during unloading periods, enough to trigger earthquakes. Stress due to snow load variations, with focusing of it in weak zones near the caldera boundary, is considered a contributing factor to seasonal seismicity observed beneath M´ yrdalsj¨ okull.

Published
2010
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6. Climate effects on volcanism: influence on magmatic systems of loading and unloading from ice mass variations, with examples from Iceland

Author

Freysteinn Sigmundsson, Erik Sturkell, Halldór Geirsson, Virginie Pinel, Björn Lund, Carolina Pagli, Fabien Albino, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Department of Earth Sciences [ Uppsala], Uppsala University, Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, Icelandic Meteorological Office, celandic Meteorological Office, Department of Earth Sciences [Gothenburg], University of Gothenburg (GU), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), and Department of Earth Sciences [Uppsala]

Subjects
010504 meteorology & atmospheric sciences, General Mathematics, [SDE.MCG]Environmental Sciences/Global Changes, General Physics and Astronomy, Poison control, Magma chamber, volcanoes, 010502 geochemistry & geophysics, global warming, 01 natural sciences, ice retreat, glacial rebound, pressure, Glacial period, Meltwater, Petrology, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, magma, Lead (sea ice), General Engineering, Post-glacial rebound, Volcano, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Magma, Geology
Abstract

Pressure influences both magma production and the failure of magma chambers. Changes in pressure interact with the local tectonic settings and can affect magmatic activity. Present-day reduction in ice load on subglacial volcanoes due to global warming is modifying pressure conditions in magmatic systems. The large pulse in volcanic production at the end of the last glaciation in Iceland suggests a link between unloading and volcanism, and models of that process can help to evaluate future scenarios. A viscoelastic model of glacio-isostatic adjustment that considers melt generation demonstrates how surface unloading may lead to a pulse in magmatic activity. Iceland’s ice caps have been thinning since 1890 and glacial rebound at rates exceeding 20 mm yr−1is ongoing. Modelling predicts a significant amount of ‘additional’ magma generation under Iceland due to ice retreat. The unloading also influences stress conditions in shallow magma chambers, modifying their failure conditions in a manner that depends critically on ice retreat, the shape and depth of magma chambers as well as the compressibility of the magma. An annual cycle of land elevation in Iceland, due to seasonal variation of ice mass, indicates an annual modulation of failure conditions in subglacial magma chambers.

Published
2010
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7. Ongoing inflation and magma accumulation of Grimsvotn subglacial volcano, Iceland

Author

Sturkell, E., Sigmundsson, F., Einarsson, P., Jouanne, François, Geirsson, H., Ofeigsson, B. G., Villemin, Thierry, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Institute of Earth Sciences [Reykjavik], University of Iceland [Reykjavik], Laboratoire de Géodynamique des Chaines Alpines (LGCA), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Icelandic Meteorological Office, celandic Meteorological Office, Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut des Sciences de la Terre (ISTerre), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)

Subjects
[SDE.MCG]Environmental Sciences/Global Changes
Published
2008

8. Active volcanism and associated crustal deformation in Iceland

Author

Sturkell, E., Einarsson, P., Sigmundsson, F., Ofeigsson, B. G., Geirsson, H., Pedersen, R., Árnadóttir, Thóra, Ólafsson, H., De Zeeuw-Van Dalfsen, E., Linde, A. T., Sacks, S. I., Lafemina, P. C., Pagl, C., Villemin, Thierry, Rymer, H., Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Institute of Earth Sciences [Reykjavik], University of Iceland [Reykjavik], Icelandic Meteorological Office, celandic Meteorological Office, Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDE.MCG]Environmental Sciences/Global Changes
Published
2008

9. Current crustal deformation at volcanoes in Iceland

Author

Sturkell, E., Einarsson, P., Sigmundsson, F., Ofeigsson, B. G., Geirsson, H., Pedersen, R., Árnadóttir, Thóra, Ólafsson, H., De Zeeuw-Van Dalfsen, E., Linde, A. T., Sacks, S. I., Lafemina, P. C., Pagli, C., Villemin, Thierry, Rymer, H., Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Institute of Earth Sciences [Reykjavik], University of Iceland [Reykjavik], Icelandic Meteorological Office, celandic Meteorological Office, Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDE.MCG]Environmental Sciences/Global Changes
Published
2008

10. Seismic and geodetic insights into magma accumulation at Katla subglacial volcano, Iceland: 1999 to 2005

Author

Matthew J. Roberts, Erik Sturkell, Ragnar Stefánsson, Freysteinn Sigmundsson, Páll Einarsson, Halldór Ólafsson, Halldór Geirsson, Gunnar B. Guðmundsson, Magnús T. Gudmundsson, Virginie Pinel, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Institute of Earth Sciences [Reykjavik], University of Iceland [Reykjavik], Icelandic Meteorological Office, celandic Meteorological Office, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)

Subjects
Atmospheric Science, Nunatak, 010504 meteorology & atmospheric sciences, Iceland, Soil Science, Magma chamber, Aquatic Science, volcanoes, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Caldera, Geothermal gradient, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, geography, geography.geographical_feature_category, Ecology, Complex volcano, Paleontology, Jökulhlaup, Forestry, Geophysics, Volcano, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Magma, Seismology, Geology, Geodesy
Abstract

International audience; Katla is one of Iceland's most active volcanoes with at least 20 eruptions in the last 1100 years. The volcano is covered mostly by the Mýrdalsjökull ice cap; consequently, Katla eruptions are phreato-magmatic and are capable of producing jökulhlaups. A jökulhlaup in July 1999, preceded by an episode of continuous seismic tremor, was the first sign of renewed magma movement under the volcano since 1955. Using seismic and geodetic observations, and insights into geothermal activity from ice-surface observations, we analyze this period of unrest and assess the present state of Katla volcano. From 1999 to 2004, GPS measurements on nunataks exposed on the caldera edge revealed steady inflation of the volcano. Our measurements show uplift and horizontal displacement of the nuntatak benchmarks at a rate of up to 2 cm a−1, together with horizontal displacement of far-field stations (>11 km) at about 0.5 cm a−1 away from the caldera centre. Using a point-source model, these data place the center of the magma chamber at 4.9 km depth beneath the northern part of the caldera. However, this depth may be overestimated because of a progressive decrease in the mass of the overlying ice cap. The depth may be only 2–3 km. About 0.01 km3 of magma has accumulated between 1999 and 2004; this value is considerably less than the estimated 1 km3 of material erupted during the last eruption of Katla in 1918. Presently, rates of crustal deformation and earthquake activity are considerably less than observed between 1999 and 2004; nonetheless, the volcano remains in an agitated state.

Published
2008
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11. A High-Rate Continuous GPS Network in Iceland for Crustal Deformation Research

Author

Geirsson, H., Árnadóttir, Thóra, Bennett, R., Lafemina, P., Jonsson, S., Hreinsdottir, S., Holland, A., Deutscher, J., Ingvarsson, T., Sturkell, E., Villemin, Thierry, Icelandic Meteorological Office, celandic Meteorological Office, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Institut de biologie et chimie des protéines [Lyon] (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), and Foray, Charlotte

Subjects
[SDE.MCG] Environmental Sciences/Global Changes, [SDE.MCG]Environmental Sciences/Global Changes
Published
2007

12. A new high-rate continuous GPS network in Iceland for crustal deformation research

Author

Geirsson, H., Árnadóttir, Thóra, Bennett, R., Hreinsdottir, S., Jonsson, S., Deutscher, Josef, Lafemina, P., Sturkell, E., Villemin, Thierry, Miyazaki, S., Icelandic Meteorological Office, celandic Meteorological Office, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Microbiologie et Génétique Moléculaire (MGM), Institut National de la Recherche Agronomique (INRA)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
[SDE.MCG]Environmental Sciences/Global Changes
Published
2007

13. Discriminating volcano deformation due to magma movements and variable surface loads: application to Katla subglacial volcano, Iceland

Author

Erik Sturkell, Freysteinn Sigmundsson, Páll Einarsson, Magnús T. Gudmundsson, Virginie Pinel, Thórdís Högnadóttir, Halldór Geirsson, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Icelandic Meteorological Office, celandic Meteorological Office, Institute of Earth Sciences [Reykjavik], University of Iceland [Reykjavik], Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)

Subjects
010504 meteorology & atmospheric sciences, GPS, Modulus, Inflow, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Physics::Geophysics, retreating ice cap, Geochemistry and Petrology, Inviscid flow, fluids and rocks, geothermics, Green' s function, GJI Volcanology, Physics::Atmospheric and Oceanic Physics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, seasonal effects on volcanoes, Global warming, crustal deformation, Green's function, Annual cycle, Volcano deformation, Geophysics, Volcano, 13. Climate action, [SDU]Sciences of the Universe [physics], Seismology, Geology
Abstract

SUMMARY Surface displacements induced by ice load variation through time are calculated by spatial integration of Green's function for both end-members: an elastic half-space and a thick elastic plate lying over an inviscid mantle. The elastic half-space model allows the consideration of displacements caused by short-term (seasonal) variations. The thick plate model describes the final relaxed state. The transition between these two stages is dominated by an effective relaxation time which depends on mantle viscosity. This behaviour is considered to estimate displacements induced by long-term load changes (ice retreat over decades). We apply these methods to the Mýrdalsjokull ice cap, Iceland, where an annual cycle in ice load occurs as well as a gradual ice retreat as a consequence of climate warming. Seasonal vertical displacements measured from 2000 to 2006 at two continuous GPS stations located near the edge of Mýrdalsjokull ice cap fit well to a model of an elastic response to the annual variation in ice load. A comparison of model displacements and observations provides a minimum value of 29 ± 5 GPa for the effective static local value of the Young's modulus. We infer long-term displacements induced by ice retreat over the last 115 yr using a combination of the instantaneous elastic response and the final relaxed state. Results are compared to GPS measurements used to monitor the Katla volcano lying beneath the Mýrdalsjokull ice cap. A forward model considering an elastic thickness of 5 km can explain a fraction of the uplift recorded from 1999 to 2004, but it cannot account for the observed horizontal velocities. The study confirms that magma inflow is required to explain observed inflation of the Katla volcano 1999–2004.

Published
2007
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14. Establishment of a high-rate continuous GPS network in Iceland

Author

Geirsson, H., Árnadóttir, Thóra, Bennett, R., Hreinsdottir, S., Jonsson, S., Lafemina, P., Sturkell, E., Villemin, Thierry, Miyazaki, S., Icelandic Meteorological Office, celandic Meteorological Office, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDE.MCG]Environmental Sciences/Global Changes
Published
2006

15. Icelandic rhythmics: Annual modulation of land elevation and plate spreading by snow load

Author

Freysteinn Sigmundsson, Thóra Árnadóttir, Ronni Grapenthin, Virginie Pinel, Halldór Geirsson, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], Icelandic Meteorological Office, celandic Meteorological Office, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Young's modulus, 010502 geochemistry & geophysics, 01 natural sciences, Displacement (vector), symbols.namesake, Modulation (music), medicine, Green's functions, Ice caps, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Elevation, crustal deformation, Geophysics, Seasonality, Snow, Geodesy, medicine.disease, continuous GPS, Volcano, 13. Climate action, [SDU]Sciences of the Universe [physics], symbols, General Earth and Planetary Sciences, Geology
Abstract

International audience; We find strong correlation between seasonal variation in CGPS time series and predicted response to annual snow load in Iceland. The load is modeled using Green's functions for an elastic halfspace and a simple sinusoidal load history on Iceland's four largest ice caps. We derive E = 40 ± 15 GPa as a minimum value for the effective Young's modulus in Iceland, increasing with distance from the Eastern Volcanic Zone. We calculate the elastic response over all of Iceland to maximum snow load at the ice caps using E = 40 GPa. Predicted annual vertical displacements are largest under the Vatnajökull ice cap with a peak-to-peak seasonal displacement of ∼37 mm. CGPS stations closest to the ice cap experience a peak-to-peak seasonal displacement of ∼16 mm, consistent with our model. East and north of Vatnajökull we find the maximum of annual horizontal displacements of ∼6 mm resulting in apparent modulation of plate spreading rates in this area.

Published
2006
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16. Current plate movements across the Mid-Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland

Author

Geirsson, H., Árnadóttir, Thóra, Völksen, C., Jiang, W., Sturkell, E., Villemin, Thierry, Einarson, P., Sigmundsson, F., Stefansson, R., Icelandic Meteorological Office, celandic Meteorological Office, Nordic Volcanological Center, Institute of Earth Sciences, Institute of Earth Sciences [University of Iceland], University of Iceland [Reykjavik]-University of Iceland [Reykjavik], State Key Laboratory of Polymer Physics and Chemistry (Changchun Institute of Applied Chemistry), Chinese Academy of Sciences [Beijing] (CAS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDE.MCG]Environmental Sciences/Global Changes, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2006

17. Advanced Monitoring of H 2 S Injection through the Coupling of Reactive Transport Models and Geophysical Responses.

Author

Ciraula DA, Kleine-Marshall BI, Galeczka IM, and Lévy L

Subjects
Environmental Monitoring methods, Iceland, Iron chemistry, Hydrogen Sulfide chemistry
Abstract

Hydrogen sulfide (H 2 S), an environmentally harmful pollutant, is a byproduct of geothermal energy production. To reduce the H 2 S emissions, H 2 S-charged water is injected into the basaltic subsurface, where it mineralizes to iron sulfides. Here, we couple geophysical induced polarization (IP) measurements in H 2 S injection wells and geochemical reactive transport models (RTM) to monitor the H 2 S storage efforts in the subsurface of Nesjavellir, one of Iceland's most productive geothermal fields. An increase in the IP response after 40 days of injection indicates iron-sulfide formation near the injection well. Likewise, the RTM shows that iron sulfides readily form at circumneutral to alkaline pH conditions, and the iron supply from basalt dissolution limits its formation. Agreement in the trends of the magnitude and distribution of iron-sulfide formation between IP and RTM suggests that coupling the methods can improve the monitoring of H 2 S mineralization by providing insight into the parameters influencing iron-sulfide formation. In particular, accurate fluid flow parameters in RTMs are critical to validate the predictions of the spatial distribution of subsurface iron-sulfide formation over time obtained through IP observations. This work establishes a foundation for expanding H 2 S sequestration monitoring efforts and a framework for coupling geophysical and geochemical site evaluations in environmental studies.

Published
2024
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18. Simultaneous rift-scale inflation of a deep crustal sill network in Afar, East Africa.

Author

La Rosa A, Pagli C, Wang H, Sigmundsson F, Pinel V, and Keir D

Abstract

Decades of studies at divergent plate margins have revealed networks of magmatic sills at the crust-mantle boundary. However, a lack of direct observations of deep magma motion limits our understanding of magma inflow from the mantle into the lower crust and the mechanism of sill formation. Here, satellite geodesy reveals rift-scale deformation caused by magma inflow in the deep crust in the Afar rift (East Africa). Simultaneous inflation of four sills, laterally separated by 10s of km and at depths ranging 9-28 km, caused uplift across a ~ 100-km-wide zone, suggesting the sills are linked to a common mantle source. Our results show the supply of magma into the lower crust is temporally episodic, occurring across a network of sills. This process reflects inherent instability of melt migration through porous mantle flow and may be the fundamental process that builds the thick igneous crust beneath magmatic rifts and rifted margins globally., (© 2024. The Author(s).)

Published
2024
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19. Steam caps in geothermal reservoirs can be monitored using seismic noise interferometry.

Author

Sánchez-Pastor P, Wu SM, Hokstad K, Kristjánsson B, Drouin V, Ducrocq C, Gunnarsson G, Rinaldi A, Wiemer S, and Obermann A

Abstract

Harvesting geothermal energy often leads to a pressure drop in reservoirs, decreasing their profitability and promoting the formation of steam caps. While steam caps are valuable energy resources, they also alter the reservoir thermodynamics. Accurately measuring the steam fraction in reservoirs is essential for both operational and economic perspectives. However, steam content estimations are very limited both in space and time since current methods rely on direct measurements within production wells. Besides, these estimations normally present large uncertainties. Here, we present a pioneering method for indirectly sampling the steam content in the subsurface using the ever-present seismic background noise. We observe a consistent annual velocity drop in the Hengill geothermal field (Iceland) and establish a correlation between the velocity drop and steam buildup using in-situ borehole data. This application opens new avenues to track the evolution of any gas reservoir in the crust with a surface-based and cost-effective method., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2023, corrected publication 2024.)

Published
2023
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20. Nitrogen Incorporation in Potassic and Micro- and Meso-Porous Minerals: Potential Biogeochemical Records and Targets for Mars Sampling.

Author

Nikitczuk MP, Bebout GE, Geiger CA, Ota T, Kunihiro T, Mustard JF, Halldórsson SA, and Nakamura E

Subjects
Exobiology methods, Nitrogen, Porosity, Minerals analysis, Earth, Planet, Extraterrestrial Environment, Zeolites, Mars
Abstract

We measured the N concentrations and isotopic compositions of 44 samples of terrestrial potassic and micro- and meso-porous minerals and a small number of whole-rocks to determine the extent to which N is incorporated and stored during weathering and low-temperature hydrothermal alteration in Mars surface/near-surface environments. The selection of these minerals and other materials was partly guided by the study of altered volcanic glass from Antarctica and Iceland, in which the incorporation of N as NH 4 in phyllosilicates is indicated by correlated concentrations of N and the LILEs ( + , K, Ba, Rb, Cs), with scatter likely related to the presence of exchanged, occluded/trapped, or encapsulated organic/inorganic N occurring within structural cavities ( i.e. , K, Ba, Rb, Cs), with scatter likely related to the presence of exchanged, occluded/trapped, or encapsulated organic/inorganic N occurring within structural cavities ( e.g. , in zeolites). The phyllosilicates, zeolites, and sulfates analyzed in this study contain between 0 and 99,120 ppm N and have δ 15 values of -34‰ to +65‰. Most of these minerals, and the few siliceous hydrothermal deposits that were analyzed, have δ air N consistent with the incorporation of biologically processed N during low-temperature hydrothermal or weathering processes. Secondary ion mass spectrometry on altered hyaloclastites demonstrates the residency of N in smectites and zeolites, and silica. We suggest that geological materials known on Earth to incorporate and store N and known to be abundant at, or near, the surface of Mars should be considered targets for upcoming Mars sample return with the intent to identify any signs of ancient or modern life.15 N consistent with the incorporation of biologically processed N during low-temperature hydrothermal or weathering processes. Secondary ion mass spectrometry on altered hyaloclastites demonstrates the residency of N in smectites and zeolites, and silica. We suggest that geological materials known on Earth to incorporate and store N and known to be abundant at, or near, the surface of Mars should be considered targets for upcoming Mars sample return with the intent to identify any signs of ancient or modern life.

Published
2022
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21. Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland.

Author

Halldórsson SA, Marshall EW, Caracciolo A, Matthews S, Bali E, Rasmussen MB, Ranta E, Robin JG, Guðfinnsson GH, Sigmarsson O, Maclennan J, Jackson MG, Whitehouse MJ, Jeon H, van der Meer QHA, Mibei GK, Kalliokoski MH, Repczynska MM, Rúnarsdóttir RH, Sigurðsson G, Pfeffer MA, Scott SW, Kjartansdóttir R, Kleine BI, Oppenheimer C, Aiuppa A, Ilyinskaya E, Bitetto M, Giudice G, and Stefánsson A

Abstract

Recent Icelandic rifting events have illuminated the roles of centralized crustal magma reservoirs and lateral magma transport 1-4 , important characteristics of mid-ocean ridge magmatism 1,5 . A consequence of such shallow crustal processing of magmas 4,5 is the overprinting of signatures that trace the origin, evolution and transport of melts in the uppermost mantle and lowermost crust 6,7 . Here we present unique insights into processes occurring in this zone from integrated petrologic and geochemical studies of the 2021 Fagradalsfjall eruption on the Reykjanes Peninsula in Iceland. Geochemical analyses of basalts erupted during the first 50 days of the eruption, combined with associated gas emissions, reveal direct sourcing from a near-Moho magma storage zone. Geochemical proxies, which signify different mantle compositions and melting conditions, changed at a rate unparalleled for individual basaltic eruptions globally. Initially, the erupted lava was dominated by melts sourced from the shallowest mantle but over the following three weeks became increasingly dominated by magmas generated at a greater depth. This exceptionally rapid trend in erupted compositions provides an unprecedented temporal record of magma mixing that filters the mantle signal, consistent with processing in near-Moho melt lenses containing 10 7 -10 8  m 3 of basaltic magma. Exposing previously inaccessible parts of this key magma processing zone to near-real-time investigations provides new insights into the timescales and operational mode of basaltic magma systems., (© 2022. The Author(s).)

Published
2022
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22. Deformation and seismicity decline before the 2021 Fagradalsfjall eruption.

Author

Sigmundsson F, Parks M, Hooper A, Geirsson H, Vogfjörd KS, Drouin V, Ófeigsson BG, Hreinsdóttir S, Hjaltadóttir S, Jónsdóttir K, Einarsson P, Barsotti S, Horálek J, and Ágústsdóttir T

Abstract

Increased rates of deformation and seismicity are well-established precursors to volcanic eruptions, and their interpretation forms the basis for eruption warnings worldwide. Rates of ground displacement and the number of earthquakes escalate before many eruptions 1-3 , as magma forces its way towards the surface. However, the pre-eruptive patterns of deformation and seismicity vary widely. Here we show how an eruption beginning on 19 March 2021 at Fagradalsfjall, Iceland, was preceded by a period of tectonic stress release ending with a decline in deformation and seismicity over several days preceding the eruption onset. High rates of deformation and seismicity occurred from 24 February to mid-March in relation to gradual emplacement of an approximately 9-km-long magma-filled dyke, between the surface and 8 km depth (volume approximately 34 × 10 6  m 3 ), as well as the triggering of strike-slip earthquakes up to magnitude M W 5.64. As stored tectonic stress was systematically released, there was less lateral migration of magma and a reduction in both the deformation rates and seismicity. Weaker crust near the surface may also have contributed to reduced seismicity, as the depth of active magma emplacement progressively shallowed. This demonstrates that the interaction between volcanoes and tectonic stress as well as crustal layering need to be fully considered when forecasting eruptions., (© 2022. The Author(s).)

Published
2022
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23. Sediment trapping - An attempt to monitor temporal variation of microplastic flux rates in aquatic systems.

Author

Saarni S, Hartikainen S, Meronen S, Uurasjärvi E, Kalliokoski M, and Koistinen A

Subjects
Environmental Monitoring, Geologic Sediments, Plastics, Microplastics, Water Pollutants, Chemical analysis
Abstract

Sediment trapping as a tool to monitor microplastic influx was tested in an urban boreal lake basin. The one-year-long trap monitoring consisted of 5-month and 7-month periods representing growing season and winter season (including the spring flood event), respectively. Sediment accumulation rate (SAR), and organic content were determined, highest SAR - 14.5 g/m 2 /d - was measured during the winter period. Microplastics were extracted from the sediment applying heavy-liquid density separation method and collected under a microscope for further identification with FTIR spectroscopy. PE was identified as the most abundant synthetic polymer type, while PP and PET are also present. The annual microplastic flux rate is 32 400 pieces/m 2 /year, and highest accumulation does not coincide with the highest SAR, but occurs during the growing season. Changes in the microplastic accumulation rates are related to seasonal conditions. Highest microplastic concentration with respect to dry sediment weight (10 200 pieces/kg) was observed in a growing season sample, while highest concentration with respect to sediment volume (1800 pieces/l) was observed during winter. This finding underlines the problems related to reporting microplastic concentrations in various units. The results highlight that sediment trap monitoring is an efficient tool for monitoring microplastic accumulation rate in aquatic environments and provides an opportunity to better understand and define processes controlling microplastic accumulation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Published
2021
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24. Unexpected large eruptions from buoyant magma bodies within viscoelastic crust.

Author

Sigmundsson F, Pinel V, Grapenthin R, Hooper A, Halldórsson SA, Einarsson P, Ófeigsson BG, Heimisson ER, Jónsdóttir K, Gudmundsson MT, Vogfjörd K, Parks M, Li S, Drouin V, Geirsson H, Dumont S, Fridriksdottir HM, Gudmundsson GB, Wright TJ, and Yamasaki T

Abstract

Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation rates, the stability of deep magma bodies is governed by the magma-host rock density contrast and the magma body thickness. During eruptions, inelastic processes including magma mush erosion and thermal effects, can form a sustained channel that supports magma flow, driven by the pressure difference between the magma body and surface vents. At failure onset, it may be difficult to forecast the final eruption volume; pressure in a magma body may drop well below the lithostatic load, create under-pressure and initiate a caldera collapse, despite only modest precursors.

Published
2020
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26. First identification and characterization of Borrobol-type tephra in the Greenland ice cores: new deposits and improved age estimates.

Author

Cook E, Davies SM, Guðmundsdóttir ER, Abbott PM, and Pearce NJG

Abstract

Contiguous sampling of ice spanning key intervals of the deglaciation from the Greenland ice cores of NGRIP, GRIP and NEEM has revealed three new silicic cryptotephra deposits that are geochemically similar to the well-known Borrobol Tephra (BT). The BT is complex and confounded by the younger closely timed and compositionally similar Penifiler Tephra (PT). Two of the deposits found in the ice are in Greenland Interstadial 1e (GI-1e) and an older deposit is found in Greenland Stadial 2.1 (GS-2.1). Until now, the BT was confined to GI-1-equivalent lacustrine sequences in the British Isles, Sweden and Germany, and our discovery in Greenland ice extends its distribution and geochemical composition. However, the two cryptotephras that fall within GI-1e ice cannot be separated on the basis of geochemistry and are dated to 14358 ± 177 a b2k and 14252 ± 173 a b2k, just 106 ± 3 years apart. The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI-1e events identified in the ice-cores or that it relates to just one of the ice-core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice-cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine sediment cores from the North Iceland Shelf (ca. 17179-16754 cal a BP). Despite showing similarities to the BT, this deposit can be distinguished on the basis of lower CaO and TiO 2 and is a valuable new tie-point that could eventually be used in high-resolution marine records to compare the climate signals from the ocean and atmosphere.

Published
2018
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27. Younger Dryas ice margin retreat triggered by ocean surface warming in central-eastern Baffin Bay.

Author

Oksman M, Weckström K, Miettinen A, Juggins S, Divine DV, Jackson R, Telford R, Korsgaard NJ, and Kucera M

Abstract

The transition from the last ice age to the present-day interglacial was interrupted by the Younger Dryas (YD) cold period. While many studies exist on this climate event, only few include high-resolution marine records that span the YD. In order to better understand the interactions between ocean, atmosphere and ice sheet stability during the YD, more high-resolution proxy records from the Arctic, located proximal to ice sheet outlet glaciers, are required. Here we present the first diatom-based high-resolution quantitative reconstruction of sea surface conditions from central-eastern Baffin Bay, covering the period 14.0-10.2 kyr BP. Our record reveals warmer sea surface conditions and strong interactions between the ocean and the West Greenland ice margin during the YD. These warmer conditions were caused by increased Atlantic-sourced water inflow combined with amplified seasonality. Our results emphasize the importance of the ocean for ice sheet stability under the current changing climate.

Published
2017
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28. Magmatic gas percolation through the old lava dome of El Misti volcano.

Author

Moussallam Y, Peters N, Masias P, Apaza F, Barnie T, Ian Schipper C, Curtis A, Tamburello G, Aiuppa A, Bani P, Giudice G, Pieri D, Davies AG, and Oppenheimer C

Abstract

The proximity of the major city of Arequipa to El Misti has focused attention on the hazards posed by the active volcano. Since its last major eruption in the fifteenth century, El Misti has experienced a series of modest phreatic eruptions and fluctuating fumarolic activity. Here, we present the first measurements of the compositions of gas emitted from the lava dome in the summit crater. The gas composition is found to be fairly dry with a H 2 O/SO 2 molar ratio of 32 ± 3, a CO 2 /SO 2 molar ratio of 2.7 ± 0.2, a H 2 S/SO 2 molar ratio of 0.23 ± 0.02 and a H 2 /SO 2 molar ratio of 0.012 ± 0.002. This magmatic gas signature with minimal evidence of hydrothermal or wall rock interaction points to a shallow magma source that is efficiently outgassing through a permeable conduit and lava dome. Field and satellite observations show no evolution of the lava dome over the last decade, indicating sustained outgassing through an established fracture network. This stability could be disrupted if dome permeability were to be reduced by annealing or occlusion of outgassing pathways. Continued monitoring of gas composition and flux at El Misti will be essential to determine the evolution of hazard potential at this dangerous volcano., (© The Author(s) 2017.)

Published
2017
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29. Post-eruptive flooding of Santorini caldera and implications for tsunami generation.

Author

Nomikou P, Druitt TH, Hübscher C, Mather TA, Paulatto M, Kalnins LM, Kelfoun K, Papanikolaou D, Bejelou K, Lampridou D, Pyle DM, Carey S, Watts AB, Weiß B, and Parks MM

Abstract

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km 3 , submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.

Published
2016
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30. Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland.

Author

Sigmundsson F, Hooper A, Hreinsdóttir S, Vogfjörd KS, Ófeigsson BG, Heimisson ER, Dumont S, Parks M, Spaans K, Gudmundsson GB, Drouin V, Árnadóttir T, Jónsdóttir K, Gudmundsson MT, Högnadóttir T, Fridriksdóttir HM, Hensch M, Einarsson P, Magnússon E, Samsonov S, Brandsdóttir B, White RS, Ágústsdóttir T, Greenfield T, Green RG, Hjartardóttir ÁR, Pedersen R, Bennett RA, Geirsson H, La Femina PC, Björnsson H, Pálsson F, Sturkell E, Bean CJ, Möllhoff M, Braiden AK, and Eibl EP

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.

Published
2015
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31. Search for magnetic monopoles in polar volcanic rocks.

Author

Bendtz K, Milstead D, Hächler HP, Hirt AM, Mermod P, Michael P, Sloan T, Tegner C, and Thorarinsson SB

Abstract

For a broad range of values of magnetic monopole mass and charge, the abundance of monopoles trapped inside Earth would be expected to be enhanced in the mantle beneath the geomagnetic poles. A search for magnetic monopoles was conducted using the signature of an induced persistent current following the passage of igneous rock samples through a SQUID-based magnetometer. A total of 24.6 kg of rocks from various selected sites, among which 23.4 kg are mantle-derived rocks from the Arctic and Antarctic areas, was analyzed. No monopoles were found, and a 90% confidence level upper limit of 9.8 × 10(-5)/g is set on the monopole density in the search samples.

Published
2013
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32. Chemical analysis of sulfur species in geothermal waters.

Author

Kaasalainen H and Stefánsson A

Subjects
Solubility, Sulfides analysis, Sulfides chemistry, Chemistry Techniques, Analytical methods, Hot Springs chemistry, Sulfur analysis, Sulfur chemistry, Water chemistry
Abstract

Analytical methods have been developed to determine sulfur species concentrations in natural geothermal waters using Reagent-Free™ Ion Chromatography (RF™-IC), titrations and spectrophotometry. The sulfur species include SO(4)(2-), S(2)O(3)(2-), and ∑S(2-) with additional determination of SO(3)(2-) and S(x)O(6)(2-) that remains somewhat semiquantitative. The observed workable limits of detections were ≤ 0.5 μM depending on sample matrix and the analytical detection limits were 0.1 μM. Due to changes in sulfur species concentrations upon storage, on-site analyses of natural water samples were preferred. Alternatively, the samples may be stabilized on resin for later elution and analysis in the laboratory. The analytical method further allowed simultaneous determination of other anions including F(-), Cl(-), dissolved inorganic carbon (DIC) and NO(3)(-) without sample preservation or stabilization. The power of the newly developed methods relies in routine analysis of sulfur speciation of importance in natural waters using techniques and facilities available in most laboratories doing water sample analysis. The new methods were successfully applied for the determination of sulfur species concentrations in samples of natural and synthetic waters., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Published
2011
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33. Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption.

Author

Sigmundsson F, Hreinsdóttir S, Hooper A, Arnadóttir T, Pedersen R, Roberts MJ, Oskarsson N, Auriac A, Decriem J, Einarsson P, Geirsson H, Hensch M, Ofeigsson BG, Sturkell E, Sveinbjörnsson H, and Feigl KL

Abstract

Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajökull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18 years of intermittent volcanic unrest. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (>5 mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a ∼0.05 km(3) magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma-ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallajökull's behaviour can be attributed to its off-rift setting with a 'cold' subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.

Published
2010
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34. Climate effects on volcanism: influence on magmatic systems of loading and unloading from ice mass variations, with examples from Iceland.

Author

Sigmundsson F, Pinel V, Lund B, Albino F, Pagli C, Geirsson H, and Sturkell E

Abstract

Pressure influences both magma production and the failure of magma chambers. Changes in pressure interact with the local tectonic settings and can affect magmatic activity. Present-day reduction in ice load on subglacial volcanoes due to global warming is modifying pressure conditions in magmatic systems. The large pulse in volcanic production at the end of the last glaciation in Iceland suggests a link between unloading and volcanism, and models of that process can help to evaluate future scenarios. A viscoelastic model of glacio-isostatic adjustment that considers melt generation demonstrates how surface unloading may lead to a pulse in magmatic activity. Iceland's ice caps have been thinning since 1890 and glacial rebound at rates exceeding 20 mm yr(-1) is ongoing. Modelling predicts a significant amount of 'additional' magma generation under Iceland due to ice retreat. The unloading also influences stress conditions in shallow magma chambers, modifying their failure conditions in a manner that depends critically on ice retreat, the shape and depth of magma chambers as well as the compressibility of the magma. An annual cycle of land elevation in Iceland, due to seasonal variation of ice mass, indicates an annual modulation of failure conditions in subglacial magma chambers.

Published
2010
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