The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Timothy Druitt - One of the best experts on this subject based on the ideXlab platform.
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Investigation of surge-derived Pyroclastic Flow formation by numerical modelling of the 25 June 1997 dome collapse at Soufrière Hills Volcano, Montserrat
Bulletin of Volcanology, 2019Co-Authors: Valentin Gueugneau, Karim Kelfoun, Timothy DruittAbstract:Deposits from ash-cloud surges associated with dome collapse can, under certain conditions, be remobilised to form surge-derived Pyroclastic Flows (SDPFs). Using numerical modelling, we reproduce the emplacement of these Flows and investigate the conditions that favour their genesis. We use the new version of the numerical model VolcFlow, which simulates the two components of a Pyroclastic Flow: the basal avalanche and the overriding ash-cloud surge. The basal avalanche (primary block-and-ash Flows and SDPFs) are simulated using three previously published rheological laws: plastic, frictional and frictional velocity-weakening rheologies. Applied to the 25 June 1997 dome collapse at Soufrière Hills Volcano, the models reproduce to different degrees the deposit footprints formed by the block-and-ash Flows, the ash-cloud surges and the SDPFs. In the plastic model, SDPFs occur if the ash-cloud surge deposit exceeds a threshold thickness that allows it to remobilise and Flow. In the frictional models, SDPFs occur only if ash-cloud surge deposition takes place on a slope exceeding the friction angle of the ash. Results also highlight that SDPFs appeared so clearly in 1997 at Montserrat due to a combination of topographic factors: (i) a bend in the Mosquito Ghaut drainage that allowed the ash-cloud surges to detach, (ii) a depositional area on the watershed between the eastern and western drainage channels and (iii) a network of tributaries that drained all the remobilised mass into Dyer’s River to form a single, large SDPF. Our model could be a promising tool for the future forecasting of hazards posed by surge-derived Pyroclastic Flows.
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investigation of surge derived Pyroclastic Flow formation by numerical modelling of the 25 june 1997 dome collapse at soufriere hills volcano montserrat
Bulletin of Volcanology, 2019Co-Authors: Valentin Gueugneau, Karim Kelfoun, Timothy DruittAbstract:Deposits from ash-cloud surges associated with dome collapse can, under certain conditions, be remobilised to form surge-derived Pyroclastic Flows (SDPFs). Using numerical modelling, we reproduce the emplacement of these Flows and investigate the conditions that favour their genesis. We use the new version of the numerical model VolcFlow, which simulates the two components of a Pyroclastic Flow: the basal avalanche and the overriding ash-cloud surge. The basal avalanche (primary block-and-ash Flows and SDPFs) are simulated using three previously published rheological laws: plastic, frictional and frictional velocity-weakening rheologies. Applied to the 25 June 1997 dome collapse at Soufriere Hills Volcano, the models reproduce to different degrees the deposit footprints formed by the block-and-ash Flows, the ash-cloud surges and the SDPFs. In the plastic model, SDPFs occur if the ash-cloud surge deposit exceeds a threshold thickness that allows it to remobilise and Flow. In the frictional models, SDPFs occur only if ash-cloud surge deposition takes place on a slope exceeding the friction angle of the ash. Results also highlight that SDPFs appeared so clearly in 1997 at Montserrat due to a combination of topographic factors: (i) a bend in the Mosquito Ghaut drainage that allowed the ash-cloud surges to detach, (ii) a depositional area on the watershed between the eastern and western drainage channels and (iii) a network of tributaries that drained all the remobilised mass into Dyer’s River to form a single, large SDPF. Our model could be a promising tool for the future forecasting of hazards posed by surge-derived Pyroclastic Flows.
Gerardo J. Soto - One of the best experts on this subject based on the ideXlab platform.
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Pyroclastic Flow hazard at Arenal volcano, Costa Rica: scenarios and assessment
Journal of Volcanology and Geothermal Research, 2012Co-Authors: Delioma Oramas-dorta, Paul D. Cole, Geoff Wadge, Guillermo E. Alvarado, Gerardo J. SotoAbstract:Abstract The present work provides a comprehensive understanding of the evolution of Pyroclastic Flow hazard at Arenal volcano, Costa Rica, during the recent period of volcanic activity. It uses the geophysical Flow model TITAN2D to analyze and summarize Pyroclastic Flow hazard patterns associated with the topographic development of the volcanic edifice (“radial hazard pattern”) and to an observed evolution in the nature of Pyroclastic Flows at Arenal (“concentric hazard pattern”). In this regard, a new classification of Pyroclastic Flows of gravitational origin at Arenal is proposed and characterized, presenting different levels of associated hazardousness. TITAN2D has been used as a basis to produce Pyroclastic Flow hazard maps for two defined scenarios: a “current” hazard scenario, considered as being fairly representative of the present-day situation at Arenal; and another scenario which is thought could represent a stage in future Pyroclastic Flow hazard where crater C has largely engulfed crater D as a result of topographic change. These two maps show significantly different hazard distributions, and demonstrate the need for frequent updates of hazard assessments in this and other similarly dynamic volcanic settings. In the case of Arenal, this implies a need for regularly updating the topographic models of the volcano to capture topographic changes that impact the distribution of volcanic Flow hazard. Furthermore, this work provides a detailed evaluation of TITAN2D regarding its suitability to form the basis of such hazard assessments.
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Spatial and temporal controls on Pyroclastic Flow hazard at Arenal volcano, Costa Rica
Journal of Volcanology and Geothermal Research, 2012Co-Authors: Delioma Oramas-dorta, Paul D. Cole, Geoff Wadge, Guillermo E. Alvarado, Gerardo J. SotoAbstract:Abstract Pyroclastic Flows represent the greatest volcanic hazard at Arenal volcano, Costa Rica, due to their recurrence, unpredictability, potential run outs, high velocities and short emplacement times. The main Pyroclastic Flow events occurring at Arenal during the present period of eruptive activity have been characterized and simulated using the geophysical Flow model TITAN2D. The simulations performed, coupled with analyses of the evolution of Arenal concerning the topographic and morphological development of the volcanic edifice and the eruptive activity; provide insight into various temporal and spatial patterns of Pyroclastic Flow hazard. Increased Pyroclastic Flow frequency is shown to be related to the vertical growth rate of the active crater. The topographic evolution of the volcanic edifice and of the morphology of the lava field explain several observed spatial hazard patterns relating to Flow directionality and run-out, and lava effusion rates are shown to be related to Pyroclastic Flow magnitude and volume. Identified patterns highlight the dynamism of Pyroclastic Flow hazard at Arenal, and its close relationship to the evolution of the volcanic edifice and of the eruptive activity. The simulations performed also draw attention to the sensitivity of Pyroclastic Flow emplacement to topographic features and to topographic change, highlighting the importance of up to date and accurate representations of the topography (DEMs) of the volcano for related hazard assessments.
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Pyroclastic Flow generated by crater-wall collapse and outpouring of the lava pool of Arenal Volcano, Costa Rica
Bulletin of Volcanology, 2001Co-Authors: Guillermo E. Alvarado, Gerardo J. SotoAbstract:The Pyroclastic Flow that issued from the Arenal summit crater on 28 August 1993 came from the collapse of the crater wall of the cone and the drainage of a lava pool. The 3-km-long Pyroclastic Flow, 2.2±0.8×106 m3 in volume, was confined to narrow valleys (30–100 m wide). The thickness of the Pyroclastic deposit ranged from 1 to 10 m, and its temperature was about 400 °C, although single bombs were up to 1,000 °C. The deposit is clast-supported, has a bimodal grain size distribution, and consists of an intimate mixture of finely pulverized rock ash, lapilli, small blocks, and cauliFlower bread-crusted bombs, in which are set meter-size lava fragments and juvenile and non-juvenile angular blocks, and bombs up to 7 m in diameter. Large faceted blocks make up 50% of the total volume of the deposit. The cauliFlower bombs have deep and intricate bread-crust texture and post-depositional vesiculation. It is proposed that the juvenile material was produced entirely from a lava pool, whereas faceted non-juvenile blocks come from the crater-wall collapse. The concentration and maximum diameter of cauliFlower bread-crusted bombs increases significantly from the base (rockslide + Pyroclastic Flow) to the top (the Pyroclastic Flow) of the deposit. An ash cloud deposited accretionary lapilli in the proximal region (outside of the Pyroclastic Flow deposit), and very fine ash fell in the distal region (between 5 and 30 km). The accretionary lapilli deposit is derived from the fine, elutriated products of the Flow as it moved. A turbulent overriding surge blew down the surrounding shrubbery in the Flow direction. The Pyroclastic Flow from August 1993, similar to the Flows of June 1975, May 1998, August 2000, and March 2001, slid and rolled rather than being buoyed up by gas. They grooved, scratched, and polished the surfaces over which they swept, similar to a Merapi-type Pyroclastic Flow. However, the mechanism of the outpouring of a lava pool and the resulting Flows composed of high- to moderate-vesiculated, cauliFlower bread-crusted bombs and juvenile blocks have not been described before. High-frequency earthquake swarms, followed by an increase in low-frequency volcanic events, preceded the 1975, 1993, and 2000 eruptions 2–4 months before. These Pyroclastic Flow events, therefore, may be triggered by internal expansion of the unstable cone in the upper part because of a slight change in the pressure of the magma column (gas content and/or effusive rate). This phenomenon has important short-term, volcanic hazard implications for touristic development of some parts on the flanks of the volcano.
Valentin Gueugneau - One of the best experts on this subject based on the ideXlab platform.
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Investigation of surge-derived Pyroclastic Flow formation by numerical modelling of the 25 June 1997 dome collapse at Soufrière Hills Volcano, Montserrat
Bulletin of Volcanology, 2019Co-Authors: Valentin Gueugneau, Karim Kelfoun, Timothy DruittAbstract:Deposits from ash-cloud surges associated with dome collapse can, under certain conditions, be remobilised to form surge-derived Pyroclastic Flows (SDPFs). Using numerical modelling, we reproduce the emplacement of these Flows and investigate the conditions that favour their genesis. We use the new version of the numerical model VolcFlow, which simulates the two components of a Pyroclastic Flow: the basal avalanche and the overriding ash-cloud surge. The basal avalanche (primary block-and-ash Flows and SDPFs) are simulated using three previously published rheological laws: plastic, frictional and frictional velocity-weakening rheologies. Applied to the 25 June 1997 dome collapse at Soufrière Hills Volcano, the models reproduce to different degrees the deposit footprints formed by the block-and-ash Flows, the ash-cloud surges and the SDPFs. In the plastic model, SDPFs occur if the ash-cloud surge deposit exceeds a threshold thickness that allows it to remobilise and Flow. In the frictional models, SDPFs occur only if ash-cloud surge deposition takes place on a slope exceeding the friction angle of the ash. Results also highlight that SDPFs appeared so clearly in 1997 at Montserrat due to a combination of topographic factors: (i) a bend in the Mosquito Ghaut drainage that allowed the ash-cloud surges to detach, (ii) a depositional area on the watershed between the eastern and western drainage channels and (iii) a network of tributaries that drained all the remobilised mass into Dyer’s River to form a single, large SDPF. Our model could be a promising tool for the future forecasting of hazards posed by surge-derived Pyroclastic Flows.
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investigation of surge derived Pyroclastic Flow formation by numerical modelling of the 25 june 1997 dome collapse at soufriere hills volcano montserrat
Bulletin of Volcanology, 2019Co-Authors: Valentin Gueugneau, Karim Kelfoun, Timothy DruittAbstract:Deposits from ash-cloud surges associated with dome collapse can, under certain conditions, be remobilised to form surge-derived Pyroclastic Flows (SDPFs). Using numerical modelling, we reproduce the emplacement of these Flows and investigate the conditions that favour their genesis. We use the new version of the numerical model VolcFlow, which simulates the two components of a Pyroclastic Flow: the basal avalanche and the overriding ash-cloud surge. The basal avalanche (primary block-and-ash Flows and SDPFs) are simulated using three previously published rheological laws: plastic, frictional and frictional velocity-weakening rheologies. Applied to the 25 June 1997 dome collapse at Soufriere Hills Volcano, the models reproduce to different degrees the deposit footprints formed by the block-and-ash Flows, the ash-cloud surges and the SDPFs. In the plastic model, SDPFs occur if the ash-cloud surge deposit exceeds a threshold thickness that allows it to remobilise and Flow. In the frictional models, SDPFs occur only if ash-cloud surge deposition takes place on a slope exceeding the friction angle of the ash. Results also highlight that SDPFs appeared so clearly in 1997 at Montserrat due to a combination of topographic factors: (i) a bend in the Mosquito Ghaut drainage that allowed the ash-cloud surges to detach, (ii) a depositional area on the watershed between the eastern and western drainage channels and (iii) a network of tributaries that drained all the remobilised mass into Dyer’s River to form a single, large SDPF. Our model could be a promising tool for the future forecasting of hazards posed by surge-derived Pyroclastic Flows.
Karim Kelfoun - One of the best experts on this subject based on the ideXlab platform.
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Investigation of surge-derived Pyroclastic Flow formation by numerical modelling of the 25 June 1997 dome collapse at Soufrière Hills Volcano, Montserrat
Bulletin of Volcanology, 2019Co-Authors: Valentin Gueugneau, Karim Kelfoun, Timothy DruittAbstract:Deposits from ash-cloud surges associated with dome collapse can, under certain conditions, be remobilised to form surge-derived Pyroclastic Flows (SDPFs). Using numerical modelling, we reproduce the emplacement of these Flows and investigate the conditions that favour their genesis. We use the new version of the numerical model VolcFlow, which simulates the two components of a Pyroclastic Flow: the basal avalanche and the overriding ash-cloud surge. The basal avalanche (primary block-and-ash Flows and SDPFs) are simulated using three previously published rheological laws: plastic, frictional and frictional velocity-weakening rheologies. Applied to the 25 June 1997 dome collapse at Soufrière Hills Volcano, the models reproduce to different degrees the deposit footprints formed by the block-and-ash Flows, the ash-cloud surges and the SDPFs. In the plastic model, SDPFs occur if the ash-cloud surge deposit exceeds a threshold thickness that allows it to remobilise and Flow. In the frictional models, SDPFs occur only if ash-cloud surge deposition takes place on a slope exceeding the friction angle of the ash. Results also highlight that SDPFs appeared so clearly in 1997 at Montserrat due to a combination of topographic factors: (i) a bend in the Mosquito Ghaut drainage that allowed the ash-cloud surges to detach, (ii) a depositional area on the watershed between the eastern and western drainage channels and (iii) a network of tributaries that drained all the remobilised mass into Dyer’s River to form a single, large SDPF. Our model could be a promising tool for the future forecasting of hazards posed by surge-derived Pyroclastic Flows.
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investigation of surge derived Pyroclastic Flow formation by numerical modelling of the 25 june 1997 dome collapse at soufriere hills volcano montserrat
Bulletin of Volcanology, 2019Co-Authors: Valentin Gueugneau, Karim Kelfoun, Timothy DruittAbstract:Deposits from ash-cloud surges associated with dome collapse can, under certain conditions, be remobilised to form surge-derived Pyroclastic Flows (SDPFs). Using numerical modelling, we reproduce the emplacement of these Flows and investigate the conditions that favour their genesis. We use the new version of the numerical model VolcFlow, which simulates the two components of a Pyroclastic Flow: the basal avalanche and the overriding ash-cloud surge. The basal avalanche (primary block-and-ash Flows and SDPFs) are simulated using three previously published rheological laws: plastic, frictional and frictional velocity-weakening rheologies. Applied to the 25 June 1997 dome collapse at Soufriere Hills Volcano, the models reproduce to different degrees the deposit footprints formed by the block-and-ash Flows, the ash-cloud surges and the SDPFs. In the plastic model, SDPFs occur if the ash-cloud surge deposit exceeds a threshold thickness that allows it to remobilise and Flow. In the frictional models, SDPFs occur only if ash-cloud surge deposition takes place on a slope exceeding the friction angle of the ash. Results also highlight that SDPFs appeared so clearly in 1997 at Montserrat due to a combination of topographic factors: (i) a bend in the Mosquito Ghaut drainage that allowed the ash-cloud surges to detach, (ii) a depositional area on the watershed between the eastern and western drainage channels and (iii) a network of tributaries that drained all the remobilised mass into Dyer’s River to form a single, large SDPF. Our model could be a promising tool for the future forecasting of hazards posed by surge-derived Pyroclastic Flows.
Guillermo E. Alvarado - One of the best experts on this subject based on the ideXlab platform.
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Pyroclastic Flow hazard at Arenal volcano, Costa Rica: scenarios and assessment
Journal of Volcanology and Geothermal Research, 2012Co-Authors: Delioma Oramas-dorta, Paul D. Cole, Geoff Wadge, Guillermo E. Alvarado, Gerardo J. SotoAbstract:Abstract The present work provides a comprehensive understanding of the evolution of Pyroclastic Flow hazard at Arenal volcano, Costa Rica, during the recent period of volcanic activity. It uses the geophysical Flow model TITAN2D to analyze and summarize Pyroclastic Flow hazard patterns associated with the topographic development of the volcanic edifice (“radial hazard pattern”) and to an observed evolution in the nature of Pyroclastic Flows at Arenal (“concentric hazard pattern”). In this regard, a new classification of Pyroclastic Flows of gravitational origin at Arenal is proposed and characterized, presenting different levels of associated hazardousness. TITAN2D has been used as a basis to produce Pyroclastic Flow hazard maps for two defined scenarios: a “current” hazard scenario, considered as being fairly representative of the present-day situation at Arenal; and another scenario which is thought could represent a stage in future Pyroclastic Flow hazard where crater C has largely engulfed crater D as a result of topographic change. These two maps show significantly different hazard distributions, and demonstrate the need for frequent updates of hazard assessments in this and other similarly dynamic volcanic settings. In the case of Arenal, this implies a need for regularly updating the topographic models of the volcano to capture topographic changes that impact the distribution of volcanic Flow hazard. Furthermore, this work provides a detailed evaluation of TITAN2D regarding its suitability to form the basis of such hazard assessments.
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Spatial and temporal controls on Pyroclastic Flow hazard at Arenal volcano, Costa Rica
Journal of Volcanology and Geothermal Research, 2012Co-Authors: Delioma Oramas-dorta, Paul D. Cole, Geoff Wadge, Guillermo E. Alvarado, Gerardo J. SotoAbstract:Abstract Pyroclastic Flows represent the greatest volcanic hazard at Arenal volcano, Costa Rica, due to their recurrence, unpredictability, potential run outs, high velocities and short emplacement times. The main Pyroclastic Flow events occurring at Arenal during the present period of eruptive activity have been characterized and simulated using the geophysical Flow model TITAN2D. The simulations performed, coupled with analyses of the evolution of Arenal concerning the topographic and morphological development of the volcanic edifice and the eruptive activity; provide insight into various temporal and spatial patterns of Pyroclastic Flow hazard. Increased Pyroclastic Flow frequency is shown to be related to the vertical growth rate of the active crater. The topographic evolution of the volcanic edifice and of the morphology of the lava field explain several observed spatial hazard patterns relating to Flow directionality and run-out, and lava effusion rates are shown to be related to Pyroclastic Flow magnitude and volume. Identified patterns highlight the dynamism of Pyroclastic Flow hazard at Arenal, and its close relationship to the evolution of the volcanic edifice and of the eruptive activity. The simulations performed also draw attention to the sensitivity of Pyroclastic Flow emplacement to topographic features and to topographic change, highlighting the importance of up to date and accurate representations of the topography (DEMs) of the volcano for related hazard assessments.
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Pyroclastic Flow generated by crater-wall collapse and outpouring of the lava pool of Arenal Volcano, Costa Rica
Bulletin of Volcanology, 2001Co-Authors: Guillermo E. Alvarado, Gerardo J. SotoAbstract:The Pyroclastic Flow that issued from the Arenal summit crater on 28 August 1993 came from the collapse of the crater wall of the cone and the drainage of a lava pool. The 3-km-long Pyroclastic Flow, 2.2±0.8×106 m3 in volume, was confined to narrow valleys (30–100 m wide). The thickness of the Pyroclastic deposit ranged from 1 to 10 m, and its temperature was about 400 °C, although single bombs were up to 1,000 °C. The deposit is clast-supported, has a bimodal grain size distribution, and consists of an intimate mixture of finely pulverized rock ash, lapilli, small blocks, and cauliFlower bread-crusted bombs, in which are set meter-size lava fragments and juvenile and non-juvenile angular blocks, and bombs up to 7 m in diameter. Large faceted blocks make up 50% of the total volume of the deposit. The cauliFlower bombs have deep and intricate bread-crust texture and post-depositional vesiculation. It is proposed that the juvenile material was produced entirely from a lava pool, whereas faceted non-juvenile blocks come from the crater-wall collapse. The concentration and maximum diameter of cauliFlower bread-crusted bombs increases significantly from the base (rockslide + Pyroclastic Flow) to the top (the Pyroclastic Flow) of the deposit. An ash cloud deposited accretionary lapilli in the proximal region (outside of the Pyroclastic Flow deposit), and very fine ash fell in the distal region (between 5 and 30 km). The accretionary lapilli deposit is derived from the fine, elutriated products of the Flow as it moved. A turbulent overriding surge blew down the surrounding shrubbery in the Flow direction. The Pyroclastic Flow from August 1993, similar to the Flows of June 1975, May 1998, August 2000, and March 2001, slid and rolled rather than being buoyed up by gas. They grooved, scratched, and polished the surfaces over which they swept, similar to a Merapi-type Pyroclastic Flow. However, the mechanism of the outpouring of a lava pool and the resulting Flows composed of high- to moderate-vesiculated, cauliFlower bread-crusted bombs and juvenile blocks have not been described before. High-frequency earthquake swarms, followed by an increase in low-frequency volcanic events, preceded the 1975, 1993, and 2000 eruptions 2–4 months before. These Pyroclastic Flow events, therefore, may be triggered by internal expansion of the unstable cone in the upper part because of a slight change in the pressure of the magma column (gas content and/or effusive rate). This phenomenon has important short-term, volcanic hazard implications for touristic development of some parts on the flanks of the volcano.
