A new model for the growth of basaltic shields based on deformation of Fernandina volcano, Galápagos Islands

Bagnardi, Marco; Amelung, F.; Poland, Michael P.

doi:10.1016/j.epsl.2013.07.016

Cited by 94 publications

(137 citation statements)

References 39 publications

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“…As for the reference stress state of the volcano over which to superpose the stress perturbation, we assume an initially isotropic reference stress field (e.g., Chadwick and Dieterich, 1995; Bagnardi et al, 2013). This is justified by the slow and gradual growth of the volcano, by repeated injection of dikes homogenizing the stress, and by diffuse fracturing that would continuously release the deviatoric stresses by inelastic deformation.…”

Section: Methodsmentioning

confidence: 99%

“…Some of the best-developed circumferential fissures are found at Fernandina (Gal ‡pagos; Fig1; Chadwick and Howard, 1991), which hosts a ~1 km deep and ~6.5 x 4 km wide caldera resulting from several collapses testified by old benches and a ~350 m drop of the SE caldera floor in the formation of circumferential fissures at Fernandina, considering the effect of: a) caldera faults capturing and channeling magma to the caldera rim (Nordlie, 1973, Browning andGudmundsson, 2015); b) caldera walls unbuttressing re-orienting the minimum compressive stress perpendicular to them (Simkin, 1984;Munro and Rowland 1996); c) stress perturbations due to the pressurization of a magma chamber (Chadwick and Dieterich, 1995;Chestler and Grosfils, 2013) or d) a previous intrusion (Bagnardi et al, 2013). The caldera fault model was excluded based on observing: i) no displacement in layers adjacent to circumferential dikes; ii) circumferential dikes crosscutting caldera faults; and iii) circumferential fissures located well downslope from the caldera rim (Chadwick and Dieterich, 1995).…”

Section: Introductionmentioning

confidence: 99%

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How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Corbi

Rivalta

Pinel

et al. 2015

Earth and Planetary Science Letters

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Calderas are topographic depressions formed by the collapse of a partly drained magma reservoir. At volcanic edifices with calderas, eruptive fissures can circumscribe the outer caldera rim, be oriented radially and/or align with the regional tectonic stress field. Constraining the mechanisms that govern this spatial arrangement is fundamental to understand the dynamics of shallow magma storage and transport and evaluate volcanic hazard. Here we show with numerical models that the previously unappreciated unloading effect of caldera formation may contribute significantly to the stress budget of a volcano. We first test this hypothesis against the ideal case of Fernandina, Gal ‡pagos, where previous models only partly explained the peculiar pattern of circumferential and radial eruptive fissures and the geometry of the intrusions determined by inverting the deformation data. We show that by taking into account the decompression due to the caldera formation, the modeled edifice stress field is consistent with all the observations. We then develop a general model for the stress state at volcanic edifices with ! 1 calderas based on the competition of caldera decompression, magma buoyancy forces and tectonic stresses. These factors control: 1) the shallow accumulation of magma in stacked sills, consistently with observations; 2) the conditions for the development of circumferential and/or radial eruptive fissures, as observed on active volcanoes. This top-down control exerted by changes in the distribution of mass at the surface allows better understanding of how shallow magma is transferred at active calderas, contributing to forecasting the location and type of opening fissures.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Corbi

Rivalta

Pinel

et al. 2015

Earth and Planetary Science Letters

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“…We exploit the radar data interferometrically (InSAR), a method now used routinely to analyze large scale deformation at many volcanoes (Fournier et al, 2010;Ebmeier et al, 2013), and allowing the identification of the depths and geometries of volcanic magma chambers (Dzurisin, 2007). Recent studies have also revealed the importance of both timeliness and spatial resolution when identifying processes associated with basaltic eruptions (Bagnardi et al, 2013;Richter et al, 2013). However, this is the first time that transient plumbing of a dome feeding system was detected as a pre-explosive inflation episode using InSAR.…”

Section: Introductionmentioning

confidence: 90%

Satellite radar data reveal short-term pre-explosive displacements and a complex conduit system at VolcÃ¡n de Colima, Mexico

et al. 2014

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The geometry of the volcanic conduit is a main parameter controlling the dynamics and the style of volcanic eruptions and their precursors, but also one of the main unknowns. Pre-eruptive signals that originate in the upper conduit region include seismicity and deformation of different types and scales. However, the locality of the source of these signals and thus the conduit geometry often remain unconstrained at steep sloped and explosive volcanoes due to the sparse instrumental coverage in the summit region and difficult access. Here we infer the shallow conduit system geometry of Volcán de Colima, Mexico, based on ground displacements detected in high resolution satellite radar data up to 7 h prior to an explosion in January 2013. We use Boundary Element Method modeling to reproduce the data synthetically and constrain the parameters of the deformation source, in combination with an analysis of photographs of the summit. We favor a two-source model, indicative of distinct regions of pressurization at very shallow levels. The horizontal location of the upper pressurization source coincides with that of post-explosive extrusion. The pattern and degree of deformation reverses again during the eruption; we therefore attribute the displacements to transient (elastic) pre-explosive pressurization of the conduit system. Our results highlight the geometrical complexity of shallow conduit systems at explosive volcanoes and its effect on the distribution of pre-eruptive deformation signals. An apparent absence of such signals at many explosive volcanoes may relate to its small temporal and spatial extent, partly controlled by upper conduit structures. Modern satellite radar instruments allow observations at high spatial and temporal resolution that may be the key for detecting and improving our understanding of the generation of precursors at explosive volcanoes.

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“…Long-lived hotspot eruptions at Kilauea, Hawai'i (e.g., Poland et al, 2008) and Piton de la Fournaise, Réunion (e.g., Peltier et al, 2010), as well as repeated episodes of intrusion in the Galapagos (e.g., Bagnardi et al, 2013) dominate the small number of systems worldwide where multiple cycles of eruption have been observed geodetically (although this also includes non-hotpot volcanoes such as Okmok, Aleutians, Biggs et al, 2010a). As well as cycles of pre-eruptive uplift followed by co-eruptive subsidence, such long-lived eruptions have also provided evidence for endogenous growth, change in intrusion location in response to varying stress fields (e.g., Bagnardi et al, 2013) and cycles of feedback related to topographic structures (e.g., Jónsson, 2009;Lénat et al, 2012).…”

Section: Insights From Global Insar Volcano Deformation Measurementsmentioning

confidence: 99%

Synthesis of global satellite observations of magmatic and volcanic deformation: implications for volcano monitoring & the lateral extent of magmatic domains

et al. 2018

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Global Synthetic Aperture Radar (SAR) measurements made over the past decades provide insights into the lateral extent of magmatic domains, and capture volcanic process on scales useful for volcano monitoring. Satellite-based SAR imagery has great potential for monitoring topographic change, the distribution of eruptive products and surface displacements (InSAR) at subaerial volcanoes. However, there are challenges in applying it routinely, as would be required for the reliable operational assessment of hazard. The deformation detectable depends upon satellite repeat time and swath widths, relative to the spatial and temporal scales of volcanological processes. We describe the characteristics of InSAR-measured volcano deformation over the past two decades, highlighting both the technique's capabilities and its limitations as a monitoring tool. To achieve this, we draw on two global datasets of volcano deformation: the Smithsonian Institution Volcanoes of the World database and the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics volcano deformation catalogue, as well as compiling some measurement characteristics and interpretations from the primary literature. We find that a higher proportion of InSAR observations capture non-eruptive and non-magmatic processes than those from ground-based instrument networks, and that both transient (< month) and long-duration (> 5 years) deformation episodes are under-represented. However, satellite radar is already used to assess the development of extended periods of unrest and long-lasting eruptions, and improved spatial resolution and coverage have resulted in the detection of previously unrecognised deformation at both ends of the spatial scale (~10 to > 1000 km 2 ). 'Baseline' records of past InSAR measurements, including 'null' results, are fundamental for any future interpretation of interferograms in terms of hazard‚ both by providing information about past deformation at an individual volcano, and for assessing the characteristics of deformation that are likely to be detectable (and undetectable) using InSAR. More than half of all InSAR deformation signals attributed to magmatic processes have sources in the shallow crust (< 5 km depth). While the depth distribution of InSAR-derived deformation sources is affected by measurement limitations, their lateral distribution provides information about the extent of active magmatic domains. Deformation is common (24% of all potentially magmatic events) at loci ≥5 km away from the nearest active volcanic vent. This demonstrates that laterally extensive active magmatic domains are not exceptional, but can comprise the shallowest part of trans-crustal magmatic systems in a range of volcanic settings.

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A new model for the growth of basaltic shields based on deformation of Fernandina volcano, Galápagos Islands

Cited by 94 publications

References 39 publications

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Satellite radar data reveal short-term pre-explosive displacements and a complex conduit system at VolcÃ¡n de Colima, Mexico

Synthesis of global satellite observations of magmatic and volcanic deformation: implications for volcano monitoring & the lateral extent of magmatic domains

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