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

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

Magma Flow Rates and Temporal Evolution of the 2012–2014 Post‐Eruptive Intrusions at El Hierro, Canary Islands

The 2011–2014 volcanic activity at El Hierro (Canary Islands) was characterized by a 5‐month long submarine eruption as well as a series of magmatic intrusions occurring between 5 months and 2 years after the eruption, as revealed by seismic swarms and ground deformation. We study the temporal evolution of the six post‐eruptive magmatic intrusions, using Global Navigation Satellite System and Interferometric Synthetic Aperture Radar observations complemented with relocated earthquakes. Magma volumes and magma supply rates are determined from inversion of the geodetic data using a Bayesian approach. The intrusions last between ~3 and 20 days and are inferred to be sill‐like, thin compared with their lateral extent and emplaced in the ~13–16 km depth range. Initial magma flow rates of ~300 m3/s decay exponentially with time. The two largest intrusions occurred in June–July 2012 and March–April 2013. During each of these events, magma migrated laterally, and >120 ×106 m3 of magma was intruded beneath the island. The shortest events, <1 week‐long, intruded ~(24hyphen;44) ×106 m3 of magma beneath the volcano. We suggest that all intrusions originated from an overpressure in a deep magma body located beneath the center of El Hierro. The crust/mantle boundary and the previous intrusion that fed the 2011–2012 submarine eruption may have discouraged the ascent of the post‐eruptive intrusions to the surface and forced them to migrate laterally away from the island as sill‐like sources

The passion scale: Aspects of reliability and validity of a new 8-item scale assessing passion.

Publisher's version (útgefin grein)In this article, the psychometric properties of a new scale aimed at quantifying passion are explored, i.e. passion related to becoming good or achieving in some area/theme/skill. The Passion Scale was designed to be quantitative, simple to administer, applicable for large-group testing, and reliable in monitoring passion. A total of 126 participants between 18 and 47 years of age (mean age = 21.65, SD = 3.45) completed an assessment of Passion Scale, enabling us to investigate its feasibility, internal consistency, construct validity and test-retest reliability. Feasibility: The overall pattern of results suggest that the scale for passion presented here is applicable for the age studied (18-47). Internal consistency: All individual item scores correlated positively with the total score, with correlations ranging from 0.51 to 0.69. The Cronbach's alpha value for the standardized items was 0.86. Construct validity: Pearson correlations coefficient between total score passion scale and Grit-S scale were 0.39 for adults, mean age 21.23 (SD = 3.45) (N = 107). Test-retest reliability: Intraclass correlation coefficient (ICCs) between test and retest scores for the total score was 0.92. These promising results warrant further development of the passion scale, including normalization based on a large, representative sample."Peer Reviewed

Passion, grit and mindset in young adults: Exploring the relationship and gender differences

Publisher's version (útgefin grein)The main aim of the study was to explore the associations between passion, grit and mindset in a group of young Icelandic adults. The sample consisted of 146 participants. The eight item Passion Scale was used to assess passion, and the Grit-S scale was used to assess grit. Mindset was measured with the Theories of Intelligence Scale (TIS). The scale has 8-items. The results show significant difference between female and male in the passion factor only, in favor of males. In addition the results indicated a significant correlation between all factors for the group as a whole; passion and grit, r = .435; passion and mindset, r = .260; grit and mindset, r = .274. The results for the gender separate indicate a same pattern for the females, significant correlation between all the factors; passion – grit, r = .382, passion-mindset, r = . 299 and grit-mindset, r = .356. For the males the pattern was different. Significant correlation was between passion-grit, r = .500 and for passion-mindset r =.260. For grit-mindset there was not significant correlation r = .215. The results indicate gender differences in associations between passion, grit and mindset.Peer reviewe

Glacio-isostatic deformation around the Vatnajokull ice cap, Iceland, induced by recent climate warming: GPS observations and finite element modeling

Glaciers in Iceland began retreating around 1890, and since then the Vatnajökull ice cap has lost over 400 km3 of ice. The associated unloading of the crust induces a glacio‐isostatic response. From 1996 to 2004 a GPS network was measured around the southern edge of Vatnajökull. These measurements, together with more extended time series at several other GPS sites, indicate vertical velocities around the ice cap ranging from 9 to 25 mm/yr, and horizontal velocities in the range 3 to 4 mm/yr. The vertical velocities have been modeled using the finite element method (FEM) in order to constrain the viscosity structure beneath Vatnajökull. We use an axisymmetric Earth model with an elastic plate over a uniform viscoelastic half‐space. The observations are consistent with predictions based on an Earth model made up of an elastic plate with a thickness of 10–20 km and an underlying viscosity in the range 4–10 × 1018 Pa s. Knowledge of the Earth structure allows us to predict uplift around Vatnajökull in the next decades. According to our estimates of the rheological parameters, and assuming that ice thinning will continue at a similar rate during this century (about 4 km3/year), a minimum uplift of 2.5 meters between 2000 to 2100 is expected near the current ice cap edge. If the thinning rates were to double in response to global warming (about 8 km3/year), then the minimum uplift between 2000 to 2100 near the current ice cap edge is expected to be 3.7 meters

Post-eruptive volcano inflation following major magma drainage: Interplay between models of viscoelastic response influence and models of magma inflow at Bárðarbunga caldera, Iceland, 2015-2018

&amp;lt;p&amp;gt;Unrest at B&amp;amp;#225;r&amp;amp;#240;arbunga after a caldera collapse in 2014-2015 includes elevated seismicity beginning about six months after the eruption ended, including nine Mw&amp;gt;4.5 earthquakes. The earthquakes occurred mostly on the northern and southern parts of a caldera ring fault. Global Navigation Satellite System (GNSS, in particular, Global Positioning System; GPS) and Interferometric Synthetic Aperture Radar (InSAR) geodesy are applied to evaluate the spatial and temporal pattern of ground deformation around B&amp;amp;#225;r&amp;amp;#240;arbunga caldera outside the icecap, in 2015-2018, when deformation rates were relatively steady. The aim is to study the role of viscoelastic relaxation following major magma drainage versus renewed magma inflow as an explanation for the ongoing unrest.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The largest horizontal velocity is measured at GPS station KISA (3 km from caldera rim), 141 mm/yr in direction N47&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt;E relative to the Eurasian plate in 2015-2018. GPS and InSAR observations show that the velocities decay rapidly outward from the caldera. We correct our observations for Glacial Isostatic Adjustment and plate spreading to extract the deformation related to volcanic activity. After this correction, some GPS sites show subsidence.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We use a reference Earth model to initially evaluate the contribution of viscoelastic processes to the observed deformation field. We model the deformation within a half-space composed of a 7-km thick elastic layer on top of a viscoelastic layer with a viscosity of 5 x 10&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt; Pa s, considering two co-eruptive contributors to the viscoelastic relaxation: &amp;amp;#8220;non-piston&amp;amp;#8221; magma withdrawal at 10 km depth (modelled as pressure drop in a spherical source) and caldera collapse (modelled as surface unloading). The other model we test is the magma inflow in an elastic half-space. Both the viscoelastic relaxation and magma inflow create horizontal outward movements around the caldera, and uplift at the surface projection of the source center in 2015-2018. Viscoelastic response due to magma withdrawal results in subsidence in the area outside the icecap. Magma inflow creates rapid surface velocity decay as observed.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We explore further two parameters in the viscoelastic reference model: the viscosity and the &amp;quot;non-piston&amp;quot; magma withdrawal volume. Our comparison between the corrected InSAR velocities and viscoelastic models suggests a viscosity of 2.6&amp;amp;#215;10&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt; Pa s and 0.36 km&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt; of &amp;amp;#8220;non-piston&amp;amp;#8221; magma withdrawal volume, given by the optimal reduced Chi-squared statistic. When the deformation is explained using only magma inflow into a single spherical source (and no viscoelastic response), the optimal model suggests an inflow rate at 1&amp;amp;#215;10&amp;lt;sup&amp;gt;7&amp;lt;/sup&amp;gt; m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;/yr at 700 m depth. A magma inflow model with more model parameters is also a possible explanation, including sill inflation at 10 km together with slip on caldera ring faults. Our reference Earth model and the two end-member models suggest that there is a trade-off between the viscoelastic relaxation and the magma inflow, since they produce similar deformation signals outside the icecap. However, to reproduce details of the observed deformation, both processes are required. A viscoelastic-only model cannot fully explain the fast velocity decay away from the caldera, whereas a magma inflow-only model cannot explain the subsidence observed at several locations.&amp;lt;/p&amp;gt; </jats:p

On subducting slab entrainment of buoyant asthenosphere

Laboratory and numerical experiments and boundary layer analysis of the entrainment of buoyant asthenosphere by subducting oceanic lithosphere implies that slab entrainment is likely to be relatively inefficient at removing a buoyant and lower viscosity asthenosphere layer. Asthenosphere would instead be mostly removed by accretion into and eventual subduction of the overlying oceanic lithosphere. The lower (hot) side of a subducting slab entrains by the formation of a ∼10–30 km-thick downdragged layer, whose thickness depends upon the subduction rate and the density contrast and viscosity of the asthenosphere, while the upper (cold) side of the slab may entrain as much by thermal 'freezing' onto the slab as by mechanical downdragging. This analysis also implies that proper treatment of slab entrainment in future numerical mantle flow experiments will require the resolution of ∼10–30 km-thick entrainment boundary layers

Deformation at Krafla and Bjarnarflag geothermal areas, Northern Volcanic Zone of Iceland, 1993-2015

The Krafla volcanic system has geothermal areas within the Krafla caldera and at Bjarnarflag in the Krafla fissure swarm, 9-km south of the Krafla caldera. Arrays of boreholes extract geothermal fluids for power plants in both areas. We collected and analyzed InSAR, GPS, and leveling data spanning 1993–2015 in order to investigate crustal deformation in these areas. The volcanic zone hosting the geothermal areas is also subject to large scale regional deformation processes, including plate spreading and deflation of the Krafla volcanic system. These deformation processes have to be taken into account in order to isolate the geothermal deformation signal. Plate spreading produces the largest horizontal displacements, but the regional deformation pattern also suggests readjustment of the Krafla system at depth after the 1975–1984 Krafla rifting episode. Observed deformation can be fit by an inflation source at about 20 km depth north of Krafla and a deflation source at similar depth directly below the Krafla caldera. Deflation signal along the fissure swarm can be reproduced by a 1-km wide sill at 4 km depth closing by 2–4 cm per year. These sources are considered to approximate the combined effects of vertical deformation associated with plate spreading and post-rifting response. Local deformation at the geothermal areas is well resolved in addition to these signals. InSAR shows that deformation at Bjarnarflag is elongated along the direction of the Krafla fissure swarm (∼4 km by ∼2 km) while it is circular at Krafla (∼5 km diameter). Rates of deflation at Krafla and Bjarnarflag geothermal areas have been relatively steady. Average volume decrease of about 6.6 ×10⁵ m³/yr for Krafla and 3.9 ×10⁵ m³/yr for Bjanarflag are found at sources located at ∼1.5 km depth, when interpreted by a spherical point source of pressure. This volume change represents about 8 ×10 −3 m³/ton of the mass of geothermal fluid extracted per year, indicating important renewal of the geothermal reservoir by water flow

Unexpected large eruptions from buoyant magma bodies within viscoelastic crust

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

Consensus statement for perioperative care in lumbar spinal fusion: Enhanced Recovery After Surgery (ERAS®) Society recommendations

BACKGROUND: Enhanced Recovery After Surgery (ERAS) evidence-based protocols for perioperative care have led to improvements in outcomes in numerous surgical areas, through multimodal optimization of patient pathway, reduction of complications, improved patient experience and reduction in the length of stay. ERAS represent a relatively new paradigm in spine surgery. PURPOSE: This multidisciplinary consensus review summarizes the literature and proposes recommendations for the perioperative care of patients undergoing lumbar fusion surgery with an ERAS program. STUDY DESIGN: This is a review article. METHODS: Under the impetus of the ERAS� society, a multidisciplinary guideline development group was constituted by bringing together international experts involved in the practice of ERAS and spine surgery. This group identified 22 ERAS items for lumbar fusion. A systematic search in the English language was performed in MEDLINE, Embase, and Cochrane Central Register of Controlled Trials. Systematic reviews, randomized controlled trials, and cohort studies were included, and the evidence was graded according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system. Consensus recommendation was reached by the group after a critical appraisal of the literature. RESULTS: Two hundred fifty-six articles were included to develop the consensus statements for 22 ERAS items; one ERAS item (prehabilitation) was excluded from the final summary due to very poor quality and conflicting evidence in lumbar spinal fusion. From these remaining 21 ERAS items, 28 recommendations were included. All recommendations on ERAS protocol items are based on the best available evidence. These included nine preoperative, eleven intraoperative, and six postoperative recommendations. They span topics from preoperative patient education and nutritional evaluation, intraoperative anesthetic and surgical techniques, and postoperative multimodal analgesic strategies. The level of evidence for the use of each recommendation is presented. CONCLUSION: Based on the best evidence available for each ERAS item within the multidisciplinary perioperative care pathways, the ERAS� Society presents this comprehensive consensus review for perioperative care in lumbar fusion