The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
G. Ryan - One of the best experts on this subject based on the ideXlab platform.
-
an overview of Lava Dome evolution Dome collapse and cyclicity at soufriere hills volcano montserrat 2005 2007
Geophysical Research Letters, 2010Co-Authors: S C Loughlin, G. Ryan, T Christopher, S De Angelis, R. Luckett, Vicky Hards, Lee JonesAbstract:[1] The third episode of Lava Dome growth at Soufriere Hills Volcano, Montserrat was characterised by higher average magma discharge rates than either previous Dome growth episode at this volcano and yet fewer collapses. During sustained Dome growth at moderate-high average rates (>6 m3/s), we identified 2–6 week discharge pulses that each supplied c.20 Mm3 magma from depth. Our observations are consistent with some existing models but we explain discrepancies by a combination of higher volatile contents and higher ascent rates. Cycles of c. 11–16 days were evident in rockfall, LP rockfall and shallow LP earthquake counts related to Dome growth and degassing. We speculate that degassing at the conduit margins together with stick-slip conduit flow may drive these cycles. Only one major collapse >10 Mm3 occurred during the third episode (on May 20, 2006) as a new magma pulse entered the Dome and coincided with heavy rainfall.
-
growth of the Lava Dome and extrusion rates at soufriere hills volcano montserrat west indies 2005 2008
Geophysical Research Letters, 2010Co-Authors: G. Ryan, Eliza S. Calder, Mike R. James, S.c. Loughlin, Lee Jones, T ChristopherAbstract:The third episode of Lava Dome growth at Soufriere Hills Volcano began 1 August 2005 and ended 20 April 2007. Volumes of the Dome and talus produced were measured using a photo-based method with a calibrated camera for increased accuracy. The total dense rock equivalent (DRE) volume of extruded andesite magma (306 ± 51 Mm3) was similar within error to that produced in the earlier episodes but the average extrusion rate was 5.6 ± 0.9 m3s−1 (DRE), higher than the previous episodes. Extrusion rates varied in a pulsatory manner from <0.5 m3s−1 to ∼20 m3s−1. On 18 May 2006, the Lava Dome had reached a volume of 85 Mm3 DRE and it was removed in its entirety during a massive Dome collapse on 20 May 2006. Extrusion began again almost immediately and built a Dome of 170 Mm3 DRE with a summit height 1047 m above sea level by 4 April 2007. There were few moderate-sized Dome collapses (1–10 Mm3) during this extrusive episode in contrast to the first episode of Dome growth in 1995–8 when they were numerous. The first and third episodes of Dome growth showed a similar pattern of low (<0.5 m3s−1) but increasing magma flux during the early stages, with steady high flux after extrusion of ∼25 Mm3.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part i Dome shape and internal structure
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Lava Domes comprise core, carapace, and clastic talus components. They can grow endogenously by inflation of a core and/or exogenously with the extrusion of shear bounded lobes and whaleback lobes at the surface. Internal structure is paramount in determining the extent to which Lava Dome growth evolves stably, or conversely the propensity for collapse. The more core Lava that exists within a Dome, in both relative and absolute terms, the more explosive energy is available, both for large pyroclastic flows following collapse and in particular for lateral blast events following very rapid removal of lateral support to the Dome. Knowledge of the location of the core Lava within the Dome is also relevant for hazard assessment purposes. A spreading toe, or lobe of core Lava, over a talus substrate may be both relatively unstable and likely to accelerate to more violent activity during the early phases of a retrogressive collapse. Soufriere Hills Volcano, Montserrat has been erupting since 1995 and has produced numerous Lava Domes that have undergone repeated collapse events. We consider one continuous Dome growth period, from August 2005 to May 2006 that resulted in a Dome collapse event on 20th May 2006. The collapse event lasted 3 h, removing the whole Dome plus Dome remnants from a previous growth period in an unusually violent and rapid collapse event. We use an axisymmetrical computational Finite Element Method model for the growth and evolution of a Lava Dome. Our model comprises evolving core, carapace and talus components based on axisymmetrical endogenous Dome growth, which permits us to model the interface between talus and core. Despite explicitly only modelling axisymmetrical endogenous Dome growth our core–talus model simulates many of the observed growth characteristics of the 2005–2006 SHV Lava Dome well. Further, it is possible for our simulations to replicate large-scale exogenous characteristics when a considerable volume of talus has accumulated around the lower flanks of the Dome. Model results suggest that Dome core can override talus within a growing Dome, potentially generating a region of significant weakness and a potential locus for collapse initiation.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part ii rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a similar to 100 x 10(6) m(3) Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 x 10(3) - 13 x 10(3) m(3) per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60-70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered. (C) 2009 Elsevier B.V. All rights reserved.
-
Modelling the Lava Dome extruded at Soufriere Hills Volcano, Montserrat, August 2005-May 2006. Part II: Rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Abstract During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a ∼ 100 × 10 6 m 3 Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 × 10 3 –13 × 10 3 m 3 per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60–70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered.
Eliza S. Calder - One of the best experts on this subject based on the ideXlab platform.
-
presentation and analysis of a worldwide database for Lava Dome collapse events the global archive of Dome instabilities gladis
Bulletin of Volcanology, 2019Co-Authors: Claire E. Harnett, Eliza S. Calder, Mark Thomas, Susanna K. Ebmeier, Alison Telford, W Murphy, Jurgen NeubergAbstract:Lava Dome collapses generate hazardous pyroclastic flows, rockfalls and debris avalanches. Despite advances in understanding Lava Dome collapses and their resultant products, the conditions that occur prior to collapse are still poorly understood. Here, we introduce the Global Archive of Dome Instabilities (GLADIS), a database that compiles worldwide historical Dome collapses and their reported properties, including original Dome volume (at the time of collapse), Dome morphology, emplacement conditions, precursory activity, Dome geometry and deposit characteristics. We determine the collapse magnitude for events where possible, using both absolute deposit volumes and relative collapse volume ratios (this being deposit volume as a proportion of original Dome volume). We use statistical analysis to explore whether relationships exist between collapse magnitude and extrusion rate, Dome growth style, original Dome volume and causal mechanism of collapse. We find that relative collapse magnitude is independent of both the extrusion rate and the original Dome volume. Relative collapse volume ratio is dependent on Dome growth style, where endogenous growth is found to precede the largest collapses (~ 75% original volume). Collapses that comprise a higher proportion (> 50%) of original Dome volume are particularly attributed to both gravitational loading and the development of gas overpressure, whilst collapses comprising a small proportion (< 10%) of original Dome volume are associated with the topography surrounding the Dome, and variations in extrusion direction. By providing validation and/or source data, we intend these data on various Dome growth and collapse events, and their associated mechanisms, to be the focus of future numerical modelling efforts, whilst the identified relationships with relative collapse volume ratios can inform collapse hazard assessment based on observations of a growing Dome.
-
the longevity of Lava Dome eruptions
Journal of Geophysical Research, 2016Co-Authors: Robert L Wolpert, Sarah E Ogburn, Eliza S. CalderAbstract:Understanding the duration of past, ongoing, and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of ongoing and future Lava Dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with “eruption” defined as the period encompassing individual episodes of Dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding, we show that probability distributions for Dome eruption durations are both heavy tailed and composition dependent. We construct objective Bayesian statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and ongoing eruptions that depend on both eruption duration to date and composition. Our Bayesian predictive distributions reflect both uncertainty about model parameter values (epistemic uncertainty) and the natural variability of the geologic processes (aleatoric uncertainty). The results are illustrated by presenting likely trajectories for 14 Dome-building eruptions ongoing in 2015. Full representation of the uncertainty is presented for two key eruptions, Soufriere Hills Volcano in Montserrat (10–139 years, median 35 years) and Sinabung, Indonesia (1–17 years, median 4 years). Uncertainties are high but, importantly, quantifiable. This work provides for the first time a quantitative and transferable method and rationale on which to base long-term planning decisions for Lava Dome-forming volcanoes, with wide potential use and transferability to forecasts of other types of eruptions and other adverse events across the geohazard spectrum.
-
Lava Dome Eruptions
The Encyclopedia of Volcanoes, 2015Co-Authors: Eliza S. Calder, Yan Lavallée, Jackie E. Kendrick, Marc BernsteinAbstract:Lava Domes form during volcanic eruptions in which highly viscous magma accumulates in the near-vent region. During this activity, gas pressure build up in the Lava Dome or shallow conduit region can destabilize the structure and trigger transitions to explosive eruptions or Lava Dome collapse. In this chapter we introduce Lava Dome eruptive activity as well as details of recent, well-monitored Lava Dome eruptions at Mount St Helens (USA), Soufriere Hills (Montserrat), and Chaiten (Chile). We then discuss Dome emplacement and the influence of rheological factors such as silica, crystal, and gas content on the embrittlement of magma and its control on eruption style. Lava Domes expose a range of morphologies as well as internal structural features that affects outgassing efficiency, their structural stability, and the generation of associated hazards. We conclude with an overview of hazards commonly associated with Lava Dome eruptions including Dome instability, collapse events, and explosive activity that can cause devastating pyroclastic flows.
-
Rhyolite Lava Dome growth styles at Chaitén Volcano, Chile (2008-2009): Interpretation of thermal imagery
Andean Geology, 2013Co-Authors: Marc Bernstein, Andrés Pavez, Nick Varley, Patrick L. Whelley, Eliza S. CalderAbstract:Airborne thermal images of the Chaiten rhyolite Lava Dome were obtained on three occasions between January 2009 and January 2010. These images were useful for understanding the nature and pace of growth of the newly extruded Lava, which formed a complex of lobes and a spine. The images also revealed contrasting growth styles affecting different parts of the Lava Dome complex. Observed synchronous endogenous and exogenous growth was likely the result of multiple flow paths within the Lava Dome. We suggest that contrasts in morphology and surface texture between various Lava lobes are the result of different extrusion rates.
-
growth of the Lava Dome and extrusion rates at soufriere hills volcano montserrat west indies 2005 2008
Geophysical Research Letters, 2010Co-Authors: G. Ryan, Eliza S. Calder, Mike R. James, S.c. Loughlin, Lee Jones, T ChristopherAbstract:The third episode of Lava Dome growth at Soufriere Hills Volcano began 1 August 2005 and ended 20 April 2007. Volumes of the Dome and talus produced were measured using a photo-based method with a calibrated camera for increased accuracy. The total dense rock equivalent (DRE) volume of extruded andesite magma (306 ± 51 Mm3) was similar within error to that produced in the earlier episodes but the average extrusion rate was 5.6 ± 0.9 m3s−1 (DRE), higher than the previous episodes. Extrusion rates varied in a pulsatory manner from <0.5 m3s−1 to ∼20 m3s−1. On 18 May 2006, the Lava Dome had reached a volume of 85 Mm3 DRE and it was removed in its entirety during a massive Dome collapse on 20 May 2006. Extrusion began again almost immediately and built a Dome of 170 Mm3 DRE with a summit height 1047 m above sea level by 4 April 2007. There were few moderate-sized Dome collapses (1–10 Mm3) during this extrusive episode in contrast to the first episode of Dome growth in 1995–8 when they were numerous. The first and third episodes of Dome growth showed a similar pattern of low (<0.5 m3s−1) but increasing magma flux during the early stages, with steady high flux after extrusion of ∼25 Mm3.
Alina J Hale - One of the best experts on this subject based on the ideXlab platform.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part i Dome shape and internal structure
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Lava Domes comprise core, carapace, and clastic talus components. They can grow endogenously by inflation of a core and/or exogenously with the extrusion of shear bounded lobes and whaleback lobes at the surface. Internal structure is paramount in determining the extent to which Lava Dome growth evolves stably, or conversely the propensity for collapse. The more core Lava that exists within a Dome, in both relative and absolute terms, the more explosive energy is available, both for large pyroclastic flows following collapse and in particular for lateral blast events following very rapid removal of lateral support to the Dome. Knowledge of the location of the core Lava within the Dome is also relevant for hazard assessment purposes. A spreading toe, or lobe of core Lava, over a talus substrate may be both relatively unstable and likely to accelerate to more violent activity during the early phases of a retrogressive collapse. Soufriere Hills Volcano, Montserrat has been erupting since 1995 and has produced numerous Lava Domes that have undergone repeated collapse events. We consider one continuous Dome growth period, from August 2005 to May 2006 that resulted in a Dome collapse event on 20th May 2006. The collapse event lasted 3 h, removing the whole Dome plus Dome remnants from a previous growth period in an unusually violent and rapid collapse event. We use an axisymmetrical computational Finite Element Method model for the growth and evolution of a Lava Dome. Our model comprises evolving core, carapace and talus components based on axisymmetrical endogenous Dome growth, which permits us to model the interface between talus and core. Despite explicitly only modelling axisymmetrical endogenous Dome growth our core–talus model simulates many of the observed growth characteristics of the 2005–2006 SHV Lava Dome well. Further, it is possible for our simulations to replicate large-scale exogenous characteristics when a considerable volume of talus has accumulated around the lower flanks of the Dome. Model results suggest that Dome core can override talus within a growing Dome, potentially generating a region of significant weakness and a potential locus for collapse initiation.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part ii rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a similar to 100 x 10(6) m(3) Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 x 10(3) - 13 x 10(3) m(3) per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60-70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered. (C) 2009 Elsevier B.V. All rights reserved.
-
Modelling the Lava Dome extruded at Soufriere Hills Volcano, Montserrat, August 2005-May 2006. Part II: Rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Abstract During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a ∼ 100 × 10 6 m 3 Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 × 10 3 –13 × 10 3 m 3 per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60–70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered.
-
Lava Dome growth and evolution with an independently deformable talus
Geophysical Journal International, 2008Co-Authors: Alina J HaleAbstract:Subduction zone volcanism occurs due to partial melting from subducting slabs, which generally results in high-viscosity magma containing a large amount of volatiles. Such volcanic eruptions can form a Lava Dome, from which collapse events are a common and important part of their evolution. Collapse events can have devastating consequences; in the form of block and ash avalanche deposits, pyroclastic flows, surges and the generation of tsunamis if they enter the sea. In addition to this, once a mass of Lava Dome has been removed during a collapse event, this results in a drop in pressure in the remaining volatile-rich magma, which may then erupt explosively. The internal structure of a Lava Dome and the extent of the surrounding carapace/talus is unknown, but likely to be critical for hazard assessment, and is the motivation for this research. Presented is a computational model for the growth and evolution of an endogenous Lava Dome, including an independently deformable talus, using the Finite Element Method. Dome growth is modelled to occur under two time-scales: continuous Dome expansion via the addition of new magma into the molten core interior, and relatively instantaneous talus readjustments due to rockfalls and the disintegration of the solid surface. The continuous deformation of the Dome is modelled as a fluid with a yield strength in the talus region. While talus deformation is modelled as a granular material that rests at angles below its angle of repose. Both surfaces, Dome and core/talus interface, are displaced using the level-set method. The model is axi-symmetric and assumes that solidification, and therefore talus growth, occurs due to gas exsolution which promotes crystallisation, rather than from surface cooling, appropriate for intermediate composition Lava flows. For the purpose of this paper we consider and apply the model to the Soufriere Hills Volcano, Montserrat, but the techniques used are generic, allowing the model to be applied to other Dome forming eruptions. The model provides information on the shape of the Dome, with the growth and extent of the talus and core found to be predominantly governed by the Lava extrusion rate, degree of solidification (i.e. a solidus pressure), the friction angle associated with the talus, and Lava Dome viscosity.
-
studying the influence of a solid shell on Lava Dome growth and evolution using the level set method
Geophysical Journal International, 2007Co-Authors: Laurent Bourgouin, Alina J Hale, Hans Muhlhaus, Antonin ArsacAbstract:A finite element formulation of the level set method, a technique to trace flow fronts and interfaces without element distortion, is presented to model the evolution of the free surface of a spreading flow for a highly viscous medium on a horizontal surface. As an example for this class of problem we consider the evolution of an axisymmetric Lava Dome. Equilibrium configurations of Lava Domes have been modelled analytically as brittle shells enclosing pressurized magma. The existence of the brittle shell may be viewed as a direct consequence of the strong temperature dependence of the viscosity. The temperature dependence leads to the formation of a thin predominantly elastic-plastic boundary layer along the free surface and acts as a constraint for the shape and flow of the Lava Dome. In our model, we adopt Iverson's assumption that the thin boundary layer behaves like an ideal plastic membrane shell enclosing the ductile interior of the Lava Dome. The effect of the membrane shell is then formally identical to a surface tension-like boundary condition for the normal stress at the free surface. The interior of the Dome is modelled as a Newtonian fluid and the axisymmetry equations of motion are formulated in a Eulerian framework. We show that the level set is an effective tool to trace and model deforming interfaces for the example of the free surface of a Lava Dome. We demonstrate that Iverson's equilibrium Dome shapes are indeed steady states of a transient model. We also show how interface conditions in the form of surface tension involving higher order spatial derivative (curvature) can be considered within a standard finite element framework.
Geoff Wadge - One of the best experts on this subject based on the ideXlab platform.
-
Chapter 13 AVTIS observations of Lava Dome growth at Soufrière Hills Volcano, Montserrat: 2004 to 2011
Geological Society London Memoirs, 2014Co-Authors: Geoff Wadge, D. G. Macfarlane, Henry M. Odbert, Adam J. Stinton, Duncan A. Robertson, Mike R. James, Harry PinkertonAbstract:Abstract To solve the problem of Lava Dome growth at Soufriere Hills Volcano (SHV) being invisible and unmeasured owing to cloud, we have designed, built and deployed a ground-based millimetre-wave radar/radiometer: the All-weather Volcano Topography Imaging Sensor (AVTIS). In this chapter, after an outline technical sketch of the instruments, we describe the campaigns between 2004 and 2011 used to test their capabilities. We then present results from the campaigns to illustrate how signals of volcanological interest can be retrieved. The primary measurements of AVTIS are range (to within, at best, about 1 m), and, from that, topography, topographical change and effusion rates, and surface temperature (to within a few degrees Celsius). Changes in radar reflectivity can indicate surface processes (e.g. mass wasting). Surface motion within the instantaneous field of view produces a Doppler signal that allows detection of rockfall. Attenuation of the signal by rain along the path can, when stacked temporally, give an image of rain cloud structure and, by calibration, a rate of rainfall. We regard a strategy of two radars – one permanantly mounted (at Windy Hill) autonomous instrument, and the other used as a rover – as being best for capturing Dome growth.
-
Cyclic extrusion of a Lava Dome based on a stick-slip mechanism
Earth and Planetary Science Letters, 2012Co-Authors: Antonio Costa, Geoff Wadge, Oleg MelnikAbstract:Abstract Lava Dome eruptions are sometimes characterised by large periodic fluctuations in extrusion rate over periods of hours that may be accompanied by Vulcanian explosions and pyroclastic flows. We consider a simple system of nonlinear equations describing a 1D flow of Lava extrusion through a deep elastic dyke feeding a shallower cylindrical conduit in order to simulate this short-period cyclicity. Stick-slip conditions depending on a critical shear stress are assumed at the wall boundary of the cylindrical conduit. By analogy with the behaviour of industrial polymers in a plastic extruder, the elastic dyke acts like a barrel and the shallower cylindrical portion of the conduit as a die for the flow of magma acting as a polymer. When we applied the model to the Soufriere Hills Volcano, Montserrat, for which the key parameters have been evaluated from previous studies, cyclic extrusions with periods from 3 to 30 h were readily simulated, matching observations. The model also reproduces the reduced period of cycles observed when a major unloading event occurs due to Lava Dome collapse.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part i Dome shape and internal structure
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Lava Domes comprise core, carapace, and clastic talus components. They can grow endogenously by inflation of a core and/or exogenously with the extrusion of shear bounded lobes and whaleback lobes at the surface. Internal structure is paramount in determining the extent to which Lava Dome growth evolves stably, or conversely the propensity for collapse. The more core Lava that exists within a Dome, in both relative and absolute terms, the more explosive energy is available, both for large pyroclastic flows following collapse and in particular for lateral blast events following very rapid removal of lateral support to the Dome. Knowledge of the location of the core Lava within the Dome is also relevant for hazard assessment purposes. A spreading toe, or lobe of core Lava, over a talus substrate may be both relatively unstable and likely to accelerate to more violent activity during the early phases of a retrogressive collapse. Soufriere Hills Volcano, Montserrat has been erupting since 1995 and has produced numerous Lava Domes that have undergone repeated collapse events. We consider one continuous Dome growth period, from August 2005 to May 2006 that resulted in a Dome collapse event on 20th May 2006. The collapse event lasted 3 h, removing the whole Dome plus Dome remnants from a previous growth period in an unusually violent and rapid collapse event. We use an axisymmetrical computational Finite Element Method model for the growth and evolution of a Lava Dome. Our model comprises evolving core, carapace and talus components based on axisymmetrical endogenous Dome growth, which permits us to model the interface between talus and core. Despite explicitly only modelling axisymmetrical endogenous Dome growth our core–talus model simulates many of the observed growth characteristics of the 2005–2006 SHV Lava Dome well. Further, it is possible for our simulations to replicate large-scale exogenous characteristics when a considerable volume of talus has accumulated around the lower flanks of the Dome. Model results suggest that Dome core can override talus within a growing Dome, potentially generating a region of significant weakness and a potential locus for collapse initiation.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part ii rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a similar to 100 x 10(6) m(3) Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 x 10(3) - 13 x 10(3) m(3) per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60-70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered. (C) 2009 Elsevier B.V. All rights reserved.
-
Modelling the Lava Dome extruded at Soufriere Hills Volcano, Montserrat, August 2005-May 2006. Part II: Rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Abstract During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a ∼ 100 × 10 6 m 3 Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 × 10 3 –13 × 10 3 m 3 per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60–70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered.
S.c. Loughlin - One of the best experts on this subject based on the ideXlab platform.
-
growth of the Lava Dome and extrusion rates at soufriere hills volcano montserrat west indies 2005 2008
Geophysical Research Letters, 2010Co-Authors: G. Ryan, Eliza S. Calder, Mike R. James, S.c. Loughlin, Lee Jones, T ChristopherAbstract:The third episode of Lava Dome growth at Soufriere Hills Volcano began 1 August 2005 and ended 20 April 2007. Volumes of the Dome and talus produced were measured using a photo-based method with a calibrated camera for increased accuracy. The total dense rock equivalent (DRE) volume of extruded andesite magma (306 ± 51 Mm3) was similar within error to that produced in the earlier episodes but the average extrusion rate was 5.6 ± 0.9 m3s−1 (DRE), higher than the previous episodes. Extrusion rates varied in a pulsatory manner from <0.5 m3s−1 to ∼20 m3s−1. On 18 May 2006, the Lava Dome had reached a volume of 85 Mm3 DRE and it was removed in its entirety during a massive Dome collapse on 20 May 2006. Extrusion began again almost immediately and built a Dome of 170 Mm3 DRE with a summit height 1047 m above sea level by 4 April 2007. There were few moderate-sized Dome collapses (1–10 Mm3) during this extrusive episode in contrast to the first episode of Dome growth in 1995–8 when they were numerous. The first and third episodes of Dome growth showed a similar pattern of low (<0.5 m3s−1) but increasing magma flux during the early stages, with steady high flux after extrusion of ∼25 Mm3.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part i Dome shape and internal structure
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Lava Domes comprise core, carapace, and clastic talus components. They can grow endogenously by inflation of a core and/or exogenously with the extrusion of shear bounded lobes and whaleback lobes at the surface. Internal structure is paramount in determining the extent to which Lava Dome growth evolves stably, or conversely the propensity for collapse. The more core Lava that exists within a Dome, in both relative and absolute terms, the more explosive energy is available, both for large pyroclastic flows following collapse and in particular for lateral blast events following very rapid removal of lateral support to the Dome. Knowledge of the location of the core Lava within the Dome is also relevant for hazard assessment purposes. A spreading toe, or lobe of core Lava, over a talus substrate may be both relatively unstable and likely to accelerate to more violent activity during the early phases of a retrogressive collapse. Soufriere Hills Volcano, Montserrat has been erupting since 1995 and has produced numerous Lava Domes that have undergone repeated collapse events. We consider one continuous Dome growth period, from August 2005 to May 2006 that resulted in a Dome collapse event on 20th May 2006. The collapse event lasted 3 h, removing the whole Dome plus Dome remnants from a previous growth period in an unusually violent and rapid collapse event. We use an axisymmetrical computational Finite Element Method model for the growth and evolution of a Lava Dome. Our model comprises evolving core, carapace and talus components based on axisymmetrical endogenous Dome growth, which permits us to model the interface between talus and core. Despite explicitly only modelling axisymmetrical endogenous Dome growth our core–talus model simulates many of the observed growth characteristics of the 2005–2006 SHV Lava Dome well. Further, it is possible for our simulations to replicate large-scale exogenous characteristics when a considerable volume of talus has accumulated around the lower flanks of the Dome. Model results suggest that Dome core can override talus within a growing Dome, potentially generating a region of significant weakness and a potential locus for collapse initiation.
-
modelling the Lava Dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part ii rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a similar to 100 x 10(6) m(3) Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 x 10(3) - 13 x 10(3) m(3) per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60-70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered. (C) 2009 Elsevier B.V. All rights reserved.
-
Modelling the Lava Dome extruded at Soufriere Hills Volcano, Montserrat, August 2005-May 2006. Part II: Rockfall activity and talus deformation
Journal of Volcanology and Geothermal Research, 2009Co-Authors: Alina J Hale, Geoff Wadge, Eliza S. Calder, S.c. Loughlin, G. RyanAbstract:Abstract During many Lava Dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the Dome are important aspects of the observed activity. An improved understanding of internal Dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a Lava Dome is poised for a major collapse and how this collapse might ensue. We consider a period of Lava Dome growth at the Soufriere Hills Volcano, Montserrat, from August 2005 to May 2006, during which a ∼ 100 × 10 6 m 3 Lava Dome developed that culminated in a major Dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the Lava Dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core Lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the Dome. We then use our model to simulate the 2005 to 2006 Soufriere Hills Dome growth using measured Dome volumes and extrusion rates to drive the model and generate the evolving configuration of the Dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 × 10 3 –13 × 10 3 m 3 per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60–70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich Lava, could have a greater lateral extent than previously considered.