Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow

Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-squarekilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, nearexponential decline of both collapse rate and the intensity of the 180-day-long eruption

Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow

Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-squarekilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, nearexponential decline of both collapse rate and the intensity of the 180-day-long eruption.</p

Controls on explosive-effusive volcanic eruption styles

One of the biggest challenges in volcanic hazard assessment is to understand how and why eruptive style changes within the same eruptive period or even from one eruption to the next at a given volcano. This review evaluates the competing processes that lead to explosive and effusive eruptions of silicic magmas. Eruptive style depends on a set of feedbacks involving interrelated magmatic properties and processes. Foremost of these are magma viscosity, gas loss, and external properties such as conduit geometry. Ultimately, these parameters control the speed at which magmas ascend, decompress and outgas en route to the surface, and thus determine eruptive style and evolution

Deformation due to geothermal exploitation at Reykjanes, Iceland

Ground deformation in utilized geothermal areas is often attributed either to pressure decrease or temperature decrease in the geothermal reservoir. A new geothermal power plant at Reykjanes began operation in May 2006 and local deformation caused by geothermal utilization was observed shortly thereafter. We use images acquired by the Envisat and TerraSAR-X (TSX) satellites, between 2003 and 2016, as well as available GNSS data, to derive constraints on the cumulative ground displacement at the Reykjanes geothermal area, Iceland, and compare these results to production data acquired from observation wells in this region. We employ interferometric analysis of synthetic aperture satellite radar images (InSAR), using a combined persistent scatterer and small baseline approach, on both ascending and descending Envisat and TSX satellite tracks covering the 2003–2016 period. Time series of range change along line-of-sight (LOS) from the ground to the satellite show the characteristics of on-going ground deflation in the vicinity of the Reykjanes power plant. In the 2005–2008 period, the main area of deformation was 4 km long by 2.5 km wide, aligned along the Reykjanes fissure swarm, but in the period 2009–2016 it is more circular in shape and ~2 km wide. LOS displacement rates have remained relatively steady in time, although slightly faster in the 2005–2008 period than the 2009–2016 period. The average LOS velocities from ascending and descending tracks are decomposed into estimates of near-vertical and near-east displacements. The inferred maximum subsidence since the start of production is ~260 mm. Horizontal displacements show contraction towards the center of deflation of up to ~140 mm. Geodetic modeling is undertaken using sources of simple geometry within an elastic halfspace to determine the optimal sources for the observed contraction throughout 2005–2016. For the earlier period modeled utilizing ENVISAT interferograms (16 June 2005–16 August 2008) the optimal source is a Yang model with a strike of 58° and a source depth of 2.2 km. The calculated volume change associated with the observed contraction is −2.3 × 106m3. For the latter period, utilizing TSX interferograms (24 September 2009–17 August 2016), the preferred source is a Mogi-type model at a depth of 1.2 km and the modeled volume change is −1 × 106m3

Syn-convergent extension observed using the RETREAT GPS network, northern Apennines, Italy

We present crustal deformation results from a geodetic experiment (Retreating-Trench, Extension, and Accretion Tectonics (RETREAT)) focused on the northern Apennines orogen in Italy. The experiment centers on 33 benchmarks measured with GPS annually or more frequently between 2003 and 2007, supplemented by data from an additional older set of 6 campaign observations from stations in northern Croatia, and 187 continuous GPS stations within and around northern Italy. In an attempt to achieve the best possible estimates for rates and their uncertainties, we estimate and filter common mode signals and noise components using the continuous stations and apply these corrections to the entire data set, including the more temporally limited campaign time series. The filtered coordinate time series data are used to estimate site velocity. We also estimate spatially variable seasonal site motions for stations with sufficient data. The RMS scatter of residual time series are generally near 1 mm and 4 mm, horizontal and vertical, respectively, for continuous and most of the new campaign stations, but scatter is slightly higher for some of the older campaign data. Velocity uncertainties are below 1 mm/yr for all but one of the stations. Maximum rates of site motion within the orogen exceed 3 mm/yr (directed NE) relative to stable Eurasia. This motion is accommodated by extension within the southwestern and central portions of the orogen, and shortening across the foreland thrust belt to the northeast of the range. The data set is consistent with contemporaneous extension and shortening at nearly equal rates. The northern Apennines block moves northeast faster than the Northern Adria microplate. Convergence between the Northern Apennines block and the Northern Adria microplate is accommodated across a narrow zone that coincides with the northeastern Apennines range front. Extension occurs directly above an intact vertically dipping slab inferred by previous authors from seismic tomography. The observed crustal deformation is consistent with a buried dislocation model for crustal faulting, but associations between crustal motion and seismically imaged mantle structure may also provide new insights on mantle dynamics