V. Hards

British Geological Survey

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i-10 index

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T. Christopher

Montserrat Volcano Observatory

Marie Edmonds

University of Cambridge

Madeleine C. S. Humphreys

Durham University

G. Ryan

University of the West Indies

R. N. Thompson

Durham University

M. D. Murphy

University of Bristol

Pamela D. Kempton

International Ocean Discovery Program

R. S. J. Sparks

University of Bristol

Silvio De Angelis

University of Liverpool

Susan Loughlin

British Geological Survey

Cooperative Institutions

British Geological Survey

Montserrat Volcano Observatory

University of Bristol

University of Cambridge

Durham University

Natural Environment Research Council

The Open University

United States Geological Survey

University of the West Indies

Istituto Nazionale di Geofisica e Vulcanologia

Author Statistics

Papers

Citation

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Research Field

Natural emissions of CO2 from the geosphere and their bearing on the geological storage of carbon dioxide

Energy (2006)

Steven W Holloway Julian A. Pearce V. Hards Takashi Ohsumi John Gale

10.1016/j.energy.2006.09.001

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Citations (134)

Cristobalite in Volcanic Ash of the Soufriere Hills Volcano, Montserrat, British West Indies

Science (1999)

P J Baxter Costanza Bonadonna R. Dupree V. Hards S. C. Kohn

Crystalline silica (mostly cristobalite) was produced by vapor-phase crystallization and devitrification in the andesite lava dome of the Soufriere Hills volcano, Montserrat. The sub-10-micrometer fraction of ash generated by pyroclastic flows formed by lava dome collapse contains 10 to 24 weight percent crystalline silica, an enrichment of 2 to 5 relative to the magma caused by selective crushing of the groundmass. The sub-10-micrometer fraction of ash generated by explosive eruptions has much lower contents (3 to 6 percent) of crystalline silica. High levels of cristobalite in respirable ash raise concerns about adverse health effects of long-term human exposure to ash from lava dome eruptions.

Lava dome

Devitrification

Dome (geology)

Volcanic ash

Stratovolcano

10.1126/science.283.5405.1142

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Citations (186)

An overview of lava dome evolution, dome collapse and cyclicity at Soufrière Hills Volcano, Montserrat, 2005–2007

Geophysical Research Letters (2010)

Susan Loughlin Richard Luckett G. Ryan T. Christopher V. Hards

The third episode of lava dome growth at Soufrière 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 m 3 /s), we identified 2–6 week discharge pulses that each supplied c.20 Mm 3 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 Mm 3 occurred during the third episode (on May 20, 2006) as a new magma pulse entered the dome and coincided with heavy rainfall.

Dome (geology)

Lava dome

Electrical conduit

10.1029/2010gl042547

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Citations (61)

Chlorine variations in the magma of Soufrière Hills Volcano, Montserrat: Insights from Cl in hornblende and melt inclusions

Geochimica et Cosmochimica Acta (2009)

Madeleine C. S. Humphreys Marie Edmonds T. Christopher V. Hards

Phenocryst

Melt inclusions

Hornblende

Lava dome

Porphyritic

Magma chamber

Pumice

10.1016/j.gca.2009.06.014

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Citations (72)

The heterogeneous Iceland plume: new insights from the alkaline basalts of the Snaefell volcanic centre

Journal of the Geological Society (1995)

V. Hards Pamela D. Kempton R. N. Thompson

Abstract It has been accepted for some time that mixing between MORB-source mantle and the Iceland plume (geochemically relatively ‘reriched’ mantle) occurs along the Reykjanes Ridge. The composition of the basalts becomes progressively more enriched in lithophile elements towards Iceland. Within Iceland itself, there is significant variation in the composition of the mafic volcanic rocks. Although variations in degree of melting of a single source could have produced the elemental compositions of the Icelandic picritic, tholeiitic and alkalic basalts, their isotope systematics are not consistent with this model and require differences in source chemistry. Therefore, either MORB-source mantle has been mixed into the plume or the plume itself is heterogeneous. The clearest indications come from Pb isotopic data, which suggest that MORB-source mantle was excluded from the generation of Icelandic volcanic rocks.

10.1144/gsl.jgs.1995.152.01.21

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Citations (73)

Influence of bacteria on rock-water interaction and clay mineral formation in subsurface granitic environments

Clay Minerals (2001)

K. Hama K. Bateman P. Coombs V. Hards A. E. Milodowski

Abstract Studies of the subsurface microbiology of the Äspö Hard Rock Laboratory, Sweden have revealed the presence of many different bacteria in the deep groundwaters which appear to maintain reducing conditions. Experiments were conducted to study the rock-water and microbial interactions. These used crushed Äspö diorite, Äspö groundwater and iron- and sulphate-reducing bacteria in flowing systems under anaerobic conditions. In column experiments, there was evidence of loss and mobilization of fine-grained crushed material (<5 μm) which had originally adhered to grain surfaces in the starting material. The mobilized fines were trapped between grains. The degree of mineralogical alteration was greater in the experiments when bacteria were present. In both column and continuously stirred reactor experiments, there is evidence for the formation of a secondary clay. These experiments have shown that microbial activity can influence rock-water interactions even in nutrient-poor conditions.

Diorite

10.1180/0009855013640012

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Citations (31)

SO2 loss rates in the plume emitted by Soufrière Hills volcano, Montserrat

Journal of Volcanology and Geothermal Research (2008)

Lizzette A. Rodríguez I. M. Watson Marie Edmonds G. Ryan V. Hards

Volcanic Gases

Panache

10.1016/j.jvolgeores.2008.01.003

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Citations (40)

Nature of Magma Recharge at Soufrière Hills volcano, Montserrat, West Indies

AGUFM (2006)

T. Barton Crystal P. Mann V. Hards G. Ryan John Stix

Source

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Citations (0)

Magma hybridisation and diffusive exchange recorded in heterogeneous glasses from Soufrière Hills Volcano, Montserrat

Geophysical Research Letters (2010)

Madeleine C. S. Humphreys Marie Edmonds T. Christopher V. Hards

Arc volcanoes commonly show evidence of mixing between mafic and silicic magma. Melt inclusions and matrix glasses in andesite erupted from Soufrière Hills Volcano, Montserrat, include an anomalously K 2 O‐rich population which shows close compositional overlap with residual glass from mafic inclusions. We suggest that these glasses represent the effects of physical mixing with mafic magma, both during ascent and by diffusive exchange during the formation of mafic inclusions. Many glasses are enriched only in K 2 O, suggesting diffusive contamination by high‐K mafic inclusion glass; others are also enriched in TiO 2 , suggesting physical mixing of remnant glass. Some mafic inclusion glasses have lost K 2 O. The preservation of this K‐rich melt component in the andesite suggests short timescales between mixing and ascent. Diffusive timescales are consistent with independent petrological estimates of magma ascent time.

Silicic

Igneous differentiation

10.1029/2009gl041926

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Citations (49)

Seismic characterization of pyroclastic flow activity at Soufrière Hills Volcano, Montserrat, 8 January 2007

Natural hazards and earth system sciences (2007)

Silvio De Angelis V. Bass V. Hards G. Ryan

Abstract. A partial dome collapse with concurrent pyroclastic flow (PF) activity occurred at Soufrière Hills Volcano (SHV), Montserrat on 8 January 2007. Pyroclastic density currents were observed to propagate from the Northwest and West sectors of the summit dome into the heads of Tyres Ghaut and Gages Valley, respectively. Between 10:00 and 10:15 UTC pyroclastic flows entered Tyres Ghaut and from there descended into the Belham Valley reaching a distance of about 5 km from the source. Pyroclastic flow activity on the Northwest and West side of the edifice continued at high levels over the following 1.5 h, although run-out distances of individual flows did not exceed 1.5 km. Subsequent observations showed that material had been removed from the lower Northwest side of the dome leaving an amphitheatre-like structure cutting through the old crater rim. The seismic waves excited by the propagation of pyroclastic flows were recorded by the Montserrat Volcano Observatory's network of broadband seismometers. The seismic records show the onset of a continuous signal before 09:30 UTC with gradually increasing amplitudes and spectral energy in the 1–8 Hz band. The signal rapidly increased in amplitude and a characteristic spindle-shaped waveform with broadband energy (1–25 Hz) was observed accompanying large PF that descended along the slopes of the volcano. The main phase was followed by a sequence of individual seismic pulses which correlated well with visual observations of PF. PF are a major hazard at SHV and pose significant risk for the population living in the proximity of the volcano. They can occur with little or no warning and have the potential to reach inhabited areas to the Northwest. The study of the seismic activity associated with the generation and propagation of pyroclastic flows can help to identify characteristic precursory seismic sequences providing valuable information to improve the understanding of the hazards posed by the SHV and to allow better warning to be given to the authorities.

Seismometer

Dome (geology)

Lava dome

10.5194/nhess-7-467-2007

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Citations (37)