The Effusive Eruption Modelling project undertook to determine the extent to which sulphur dioxid... more The Effusive Eruption Modelling project undertook to determine the extent to which sulphur dioxide and sulphate aerosol might be hazardous at ground and flight levels during a future eruption scenario based on a Laki-type eruption. In order to do this the model source term was constructed and comprised five weeks of daily emissions followed by one week of no emissions. In order to sample different meteorology, the 6-week model source term is repeated eighty times over 10 years of meteorology. The scenario was run using both the NAME model, and the EME4UK model. Detailed results are presented in Witham et al. This presentation reports the results of an assessment of UK impacts of trace species and sulphur deposition.
In response to the recent introduction of large, long-lasting gas-rich volcanic eruptions to the ... more In response to the recent introduction of large, long-lasting gas-rich volcanic eruptions to the UK National Risk Register (risk H55) a modelling project has been conducted to improve our understanding of potential hazards to the UK from such an eruption on Iceland. A precautionary “reasonable worst case” eruption scenario based on the 1783-1784 CE Laki eruption has been determined using the results of an expert elicitation of scientists. This scenario has been simulated 80 times using two different atmospheric chemistry and transport models (NAME and EMEP4UK) over 10 years of meteorology (2003-2012). The results provide information on the range of concentrations of sulphur dioxide (SO2), sulphate aerosol (SO4) and some halogen species that might be experienced in the UK during such an eruption and the likelihood of key thresholds being exceeded and the duration of their exceedance. Data for the surface and for a range of key flight altitudes have been produced. These are evaluated ...
Dome-forming eruptions can extend for significant periods of time and can be dangerous; nearly al... more Dome-forming eruptions can extend for significant periods of time and can be dangerous; nearly all dome-forming eruptions have been associated with some level of explosive activity. Hazards related to these eruptions are numerous and often include mass flows: dome-collapse and column-collapse pyroclastic flows, ash-cloud surges, lahars, and debris avalanches. Two global databases have been developed and are currently hosted on VHub.org: DomeHaz (https://vhub.org/groups/domedatabase/) contains information about 367 dome-forming episodes 1000 AD to present, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude of associated explosions. FlowDat (https://vhub.org/groups/massflowdatabase) includes 257 pyroclastic flows and surges, and records run-out length, volume, cross-sectional and planimetric area, as well as other mobility information. Analysis using the DomeHaz database has provided useful information regarding the relati...
This paper describes ash-venting activity at Soufrière Hills Volcano, Montserrat that was precurs... more This paper describes ash-venting activity at Soufrière Hills Volcano, Montserrat that was precursory to the onset of three phases of lava extrusion in 2005, 2008 and 2009, and similar ash venting that occurred during the fifth phase of lava extrusion.We describe in detail a style of mild, tephra-generating activity termed ash venting and its associated tephra products. The nature of the seismicity associated with ash venting is compared with that of explosive activity. All explosive events, from small explosions to large Vulcanian explosions, have impulsive, low-frequency onsets. These are absent in ash-venting events, which have subtle, emergent onsets.Microscope and grain-size analyses show that ash-venting events and large Vulcanian explosions generate tephra that is similar in grain size (in medial and distal regions), although phreatic events in 2005 were finer grained. Ash-venting products are either composed of fine-grained, variably altered pre-existing material or juvenile ...
Eos, Transactions American Geophysical Union, 2011
IAVCEI‐WMO Workshop on Ash Dispersal Forecast and Civil Aviation; Geneva, Switzerland, 18–20 Octo... more IAVCEI‐WMO Workshop on Ash Dispersal Forecast and Civil Aviation; Geneva, Switzerland, 18–20 October 2010; The April–May 2010 Eyjafjallajökull eruption brought to light the harmful effects of volcanic ash on civil aviation and the importance of robust ash forecasting based on the combination of numerical weather prediction (NWP), volcanic ash transport and dispersal models (VATDMs), and data acquisition. The Workshop on Ash Dispersal Forecast and Civil Aviation has produced a consensual document describing the characteristics and range of application of different VATDMs, identifying the needs of the modeling community, investigating new data acquisition strategies, and discussing how to improve communication between the volcanology community and operational agencies. The workshop was held at the World Meteorological Organization's (WMO) Geneva headquarters under the sponsorship of the Faculty of Sciences of the University of Geneva, the International Association of Volcanology a...
Journal of Geophysical Research: Solid Earth, 2012
The 2010 Eyjafjallajökull lasted 39 days and had 4 different phases, of which the first and third... more The 2010 Eyjafjallajökull lasted 39 days and had 4 different phases, of which the first and third (14–18 April and 5–6 May) were most intense. Most of this period was dominated by winds with a northerly component that carried tephra toward Europe, where it was deposited in a number of locations and was sampled by rain gauges or buckets, surface swabs, sticky‐tape samples and air filtering. In the UK, tephra was collected from each of the Phases 1–3 with a combined range of latitudes spanning the length of the country. The modal grain size of tephra in the rain gauge samples was 25 μm, but the largest grains were 100 μm in diameter and highly vesicular. The mass loading was equivalent to 8–218 shards cm−2, which is comparable to tephra layers from much larger past eruptions. Falling tephra was collected on sticky tape in the English Midlands on 19, 20 and 21st April (Phase 2), and was dominated by aggregate clasts (mean diameter 85 μm, component grains <10 μm). SEM‐EDS spectra for...
Lava dome forming volcanic eruptions are common throughout the world. They can be dangerous; near... more Lava dome forming volcanic eruptions are common throughout the world. They can be dangerous; nearly all dome-forming eruptions have been associated with explosive activity (Newhall and Melson, 1983). Most explosions are vulcanian with eruption plumes ...
The eruption of Soufrière Hills Volcano, Montserrat (1995-1999) has displayed a wide range of vol... more The eruption of Soufrière Hills Volcano, Montserrat (1995-1999) has displayed a wide range of volcanic phenomena: growth of an andesitic lava dome, generation of pyroclastic flows by lava dome collapse and by fountain collapse in explosive eruptions, Vulcanian and sub-Plinian explosivity with accompanying tephra fall, entrance of pyroclastic flows into the sea, sector collapse with formation of a debris avalanche and a high-velocity pyroclastic density current, and generation of lahars. New phenomena include: cyclic patterns of ground deformation linked with shallow seismicity and eruptive activity; pyroclastic flows formed by rapid sedimentation from pyroclastic surges; and an unprecedented slow escalation of eruption intensity. Magma pulsations with timescales of hours to years have been recognized. Transitions from extrusive to explosive activity were triggered by major dome collapses. Relationships between magma ascent dynamics and geophysical signals have been elucidated. Ascen...
The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava dome... more The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava domes, and inhalation of cristobalite-rich ash may pose a chronic respiratory hazard. We investigate the causes of variation in cristobalite abundance (measured by X-ray diffraction) in ash from dome collapses, explosions and ash venting from 1997 to 2010.Cristobalite abundance in bulk dome-collapse ash varies between 4 and 23 wt%. During periods of slow lava extrusion (<5 m3 s−1), cristobalite is abundant (7–23 wt%), which we attribute to extensive devitrification in slow-cooling lava; it can also form rapidly (15 wt% in 2 months), but we find no correlation between cristobalite abundance and dome residence time (DRT). By contrast, during rapid extrusion (>5 m3 s−1), cristobalite abundance is low (4–7 wt%, similar to that associated with Vulcanian explosions), and correlates strongly with DRT. We attribute this correlation to progressive vapour-phase mineralization or devitrification,...
The Effusive Eruption Modelling project undertook to determine the extent to which sulphur dioxid... more The Effusive Eruption Modelling project undertook to determine the extent to which sulphur dioxide and sulphate aerosol might be hazardous at ground and flight levels during a future eruption scenario based on a Laki-type eruption. In order to do this the model source term was constructed and comprised five weeks of daily emissions followed by one week of no emissions. In order to sample different meteorology, the 6-week model source term is repeated eighty times over 10 years of meteorology. The scenario was run using both the NAME model, and the EME4UK model. Detailed results are presented in Witham et al. This presentation reports the results of an assessment of UK impacts of trace species and sulphur deposition.
In response to the recent introduction of large, long-lasting gas-rich volcanic eruptions to the ... more In response to the recent introduction of large, long-lasting gas-rich volcanic eruptions to the UK National Risk Register (risk H55) a modelling project has been conducted to improve our understanding of potential hazards to the UK from such an eruption on Iceland. A precautionary “reasonable worst case” eruption scenario based on the 1783-1784 CE Laki eruption has been determined using the results of an expert elicitation of scientists. This scenario has been simulated 80 times using two different atmospheric chemistry and transport models (NAME and EMEP4UK) over 10 years of meteorology (2003-2012). The results provide information on the range of concentrations of sulphur dioxide (SO2), sulphate aerosol (SO4) and some halogen species that might be experienced in the UK during such an eruption and the likelihood of key thresholds being exceeded and the duration of their exceedance. Data for the surface and for a range of key flight altitudes have been produced. These are evaluated ...
Dome-forming eruptions can extend for significant periods of time and can be dangerous; nearly al... more Dome-forming eruptions can extend for significant periods of time and can be dangerous; nearly all dome-forming eruptions have been associated with some level of explosive activity. Hazards related to these eruptions are numerous and often include mass flows: dome-collapse and column-collapse pyroclastic flows, ash-cloud surges, lahars, and debris avalanches. Two global databases have been developed and are currently hosted on VHub.org: DomeHaz (https://vhub.org/groups/domedatabase/) contains information about 367 dome-forming episodes 1000 AD to present, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude of associated explosions. FlowDat (https://vhub.org/groups/massflowdatabase) includes 257 pyroclastic flows and surges, and records run-out length, volume, cross-sectional and planimetric area, as well as other mobility information. Analysis using the DomeHaz database has provided useful information regarding the relati...
This paper describes ash-venting activity at Soufrière Hills Volcano, Montserrat that was precurs... more This paper describes ash-venting activity at Soufrière Hills Volcano, Montserrat that was precursory to the onset of three phases of lava extrusion in 2005, 2008 and 2009, and similar ash venting that occurred during the fifth phase of lava extrusion.We describe in detail a style of mild, tephra-generating activity termed ash venting and its associated tephra products. The nature of the seismicity associated with ash venting is compared with that of explosive activity. All explosive events, from small explosions to large Vulcanian explosions, have impulsive, low-frequency onsets. These are absent in ash-venting events, which have subtle, emergent onsets.Microscope and grain-size analyses show that ash-venting events and large Vulcanian explosions generate tephra that is similar in grain size (in medial and distal regions), although phreatic events in 2005 were finer grained. Ash-venting products are either composed of fine-grained, variably altered pre-existing material or juvenile ...
Eos, Transactions American Geophysical Union, 2011
IAVCEI‐WMO Workshop on Ash Dispersal Forecast and Civil Aviation; Geneva, Switzerland, 18–20 Octo... more IAVCEI‐WMO Workshop on Ash Dispersal Forecast and Civil Aviation; Geneva, Switzerland, 18–20 October 2010; The April–May 2010 Eyjafjallajökull eruption brought to light the harmful effects of volcanic ash on civil aviation and the importance of robust ash forecasting based on the combination of numerical weather prediction (NWP), volcanic ash transport and dispersal models (VATDMs), and data acquisition. The Workshop on Ash Dispersal Forecast and Civil Aviation has produced a consensual document describing the characteristics and range of application of different VATDMs, identifying the needs of the modeling community, investigating new data acquisition strategies, and discussing how to improve communication between the volcanology community and operational agencies. The workshop was held at the World Meteorological Organization's (WMO) Geneva headquarters under the sponsorship of the Faculty of Sciences of the University of Geneva, the International Association of Volcanology a...
Journal of Geophysical Research: Solid Earth, 2012
The 2010 Eyjafjallajökull lasted 39 days and had 4 different phases, of which the first and third... more The 2010 Eyjafjallajökull lasted 39 days and had 4 different phases, of which the first and third (14–18 April and 5–6 May) were most intense. Most of this period was dominated by winds with a northerly component that carried tephra toward Europe, where it was deposited in a number of locations and was sampled by rain gauges or buckets, surface swabs, sticky‐tape samples and air filtering. In the UK, tephra was collected from each of the Phases 1–3 with a combined range of latitudes spanning the length of the country. The modal grain size of tephra in the rain gauge samples was 25 μm, but the largest grains were 100 μm in diameter and highly vesicular. The mass loading was equivalent to 8–218 shards cm−2, which is comparable to tephra layers from much larger past eruptions. Falling tephra was collected on sticky tape in the English Midlands on 19, 20 and 21st April (Phase 2), and was dominated by aggregate clasts (mean diameter 85 μm, component grains <10 μm). SEM‐EDS spectra for...
Lava dome forming volcanic eruptions are common throughout the world. They can be dangerous; near... more Lava dome forming volcanic eruptions are common throughout the world. They can be dangerous; nearly all dome-forming eruptions have been associated with explosive activity (Newhall and Melson, 1983). Most explosions are vulcanian with eruption plumes ...
The eruption of Soufrière Hills Volcano, Montserrat (1995-1999) has displayed a wide range of vol... more The eruption of Soufrière Hills Volcano, Montserrat (1995-1999) has displayed a wide range of volcanic phenomena: growth of an andesitic lava dome, generation of pyroclastic flows by lava dome collapse and by fountain collapse in explosive eruptions, Vulcanian and sub-Plinian explosivity with accompanying tephra fall, entrance of pyroclastic flows into the sea, sector collapse with formation of a debris avalanche and a high-velocity pyroclastic density current, and generation of lahars. New phenomena include: cyclic patterns of ground deformation linked with shallow seismicity and eruptive activity; pyroclastic flows formed by rapid sedimentation from pyroclastic surges; and an unprecedented slow escalation of eruption intensity. Magma pulsations with timescales of hours to years have been recognized. Transitions from extrusive to explosive activity were triggered by major dome collapses. Relationships between magma ascent dynamics and geophysical signals have been elucidated. Ascen...
The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava dome... more The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava domes, and inhalation of cristobalite-rich ash may pose a chronic respiratory hazard. We investigate the causes of variation in cristobalite abundance (measured by X-ray diffraction) in ash from dome collapses, explosions and ash venting from 1997 to 2010.Cristobalite abundance in bulk dome-collapse ash varies between 4 and 23 wt%. During periods of slow lava extrusion (<5 m3 s−1), cristobalite is abundant (7–23 wt%), which we attribute to extensive devitrification in slow-cooling lava; it can also form rapidly (15 wt% in 2 months), but we find no correlation between cristobalite abundance and dome residence time (DRT). By contrast, during rapid extrusion (>5 m3 s−1), cristobalite abundance is low (4–7 wt%, similar to that associated with Vulcanian explosions), and correlates strongly with DRT. We attribute this correlation to progressive vapour-phase mineralization or devitrification,...
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