R. S. J. Sparks

University of Bristol

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B. Voight

Pennsylvania State University

Willy Aspinall

University of Bristol

Oleg Melnik

Lomonosov Moscow State University

Herbert E. Huppert

University of Cambridge

Jon Blundy

University of Oxford

Jenni Barclay

University of East Anglia

Haraldur Sigurdsson

University of Rhode Island

G. S. Mattioli

The University of Texas at Arlington

Catherine Annen

Czech Academy of Sciences, Institute of Geophysics

M. Field

University of Bristol

Cooperative Institutions

University of Bristol

197

University of Cambridge

Montserrat Volcano Observatory

Centre National de la Recherche Scientifique

United States Geological Survey

British Geological Survey

University of Oxford

University of Leeds

University of the West Indies

Imperial College London

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Eruption of kimberlite magmas: physical volcanology, geomorphology and age of the youngest kimberlitic volcanoes known on earth (the Upper Pleistocene/Holocene Igwisi Hills volcanoes, Tanzania)

Bulletin of Volcanology (2012)

Richard J. Brown Shukrani Manya Iris Buisman G. Fontana M. Field

Lapilli

Peléan eruption

Scoria

10.1007/s00445-012-0619-8

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Citations (70)

Experiments on deaerating granular flows and implications for pyroclastic flow mobility

Geophysical Research Letters (2002)

Olivier Roche Mark A Gilbertson Jeremy C. Phillips R. S. J. Sparks

Granular flows were generated by the release of beds of particles in various fluidized states, which then deaerated in a horizontal channel. We describe characteristics of the flows and their deposits. Morphological similarities between deposits in experiments and in the field suggest that pyroclastic flow deposits form from a fluidized mixture. The experiments show that slightly expanded, fluidized flows are more mobile than non‐fluidized flows of equivalent volume and material composition. They travel to a fixed distance from their source, which depends only weakly on their initial degree of fluidization. Flows of fine particles (<100 μm) deaerate slowly and are highly mobile. Pyroclastic flows commonly have large amounts of fine ash, which may have a controlling influence on their high mobility.

Fluidization

10.1029/2002gl014819

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Citations (45)

The nature of volcanism

Cambridge University Press eBooks (2009)

Charles B. Connor R. S. J. Sparks M. Dı́ez A. C. Volentik Sophie Pearson

Few people living in the town of Armero, Colombia, realized the immediate danger they faced in the autumn of 1985. Nevado Del Ruiz volcano, 65 km from Armero, had reawakened after more than one hundred years of repose. During the previous year new magma had risen beneath this ice-capped Andean volcano (Figure 3.1) to within a few kilometers of the surface. Intermittent explosions showered the summit glacier with pyroclasts, fragments of rock propelled by the sudden expansion of volcanic gases within the ascending magma. After months of this intermittent explosive activity, a much larger explosive eruption sent pyroclastic flows, hot gaseous clouds loaded with pyroclastic rock fragments, across the summit glaciers. The ice melted rapidly and water mixed with pyroclasts swept into river channels that source high on the volcano.

Peléan eruption

Summit

10.1017/cbo9780511635380.004

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Citations (9)

Discharge of pyroclastic flows into the sea during the 1996?1998 eruptions of the Soufri�re Hills volcano, Montserrat

Bulletin of Volcanology (2004)

Karen Hart Steven Carey Haraldur Sigurdsson R. S. J. Sparks Richard Robertson

Pyroclastic fall

Submarine volcano

10.1007/s00445-004-0342-1

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Citations (42)

The Piedras Grandes-Soncor Eruptions, Lascar Volcano, Chile; Evolution of a Zoned Magma Chamber in the Central Andean Upper Crust

Journal of Petrology (1999)

S. J. Matthews R. S. J. Sparks M. Gardeweg

Stage II of Lascar Volcano, Chile, involved development of an andesite to dacite volcanic complex and associated hypabyssal porphyry intrusions above the main magma chamber. The system culminated in development of a large zoned magma chamber that erupted in the large-magnitude (8 km3) Soncor explosive eruption at 26.5 ka, forming a Plinian pumice deposit and ignimbrite. Vent-derived lithic clasts in the Soncor deposits sample the pre-existing Stage II complex. The Piedras Grandes hornblende andesite unit represents a pre-Soncor dome complex. The andesite consistsof a heterogeneous phenocryst assemblage of plagioclase–amphibole–orthopyroxene–oxides and minor biotite, clinopyroxene, quartz, apatite, anhydrite and olivine together with commingled basaltic andesite inclusions and streaks. Temperature estimates from zoned orthopyroxenes and Fe–Ti oxides and disequilibrium between phenocrysts indicate an origin by remobilization and remelting of an igneous protolith by influx of hydrous mafic magmas so that the andesite is a mixture of partial melt, restite crystals, mafic components and phenocrysts. More silicic Stage II rocks are also interpreted as partial melts with entrained restite. The zoned Soncor chamber contained dacite (67 wt % SiO2) to silicic andesite (61 wt % SiO2) crystal-rich magmas with an assemblage of plagioclase–orthopyroxene–clinopyroxene–oxides with minor biotite, amphibole, apatite, zircon, anhydrite, pyrrhotite and olivine. Hornblende-rich mafic andesite pumice from late flow units in the ignimbrite provides evidence for influxes of hydrous mafic magmas at the base of the chamber at sufficient depths to stabilize amphibole. The hydrous mafic magmas are interpreted to have evolved in the lower crust by high-pressure fractionation with some lower-crustal contamination. The Soncor zoned magma chamber developed in the upper crust at about 6 km depth as a result of repeated influx of hydrous mafic magmas. The magmas in the chamber evolved by open-system fractionation with magma mixing being important in the less evolved magmas. Repeated influxes of hydrous mafic magmas resulted in convective stirring and addition of heat, volatiles and mafic components to the chamber. This produced complex histories of individual crystals and heterogeneous character of phenocrysts in individual samples. Halogen contents of amphibole, biotite, apatite and glass inclusions, S contents of glass inclusions, stabilization of anhydrite in the silicic magmas, and mass balance calculations imply major transfer of volatile components from the hydrous mafic magmas into the interior of the zoned chamber in the form of a co-magmatic fluid phase.

Phenocryst

Silicic

Basaltic andesite

Magma chamber

Pumice

Fractional crystallization (geology)

Dacite

10.1093/petroj/40.12.1891

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Citations (97)

Volcanic Eruptions: Cyclicity During Lava Dome Growth

Springer eBooks (2021)

Oleg Melnik R. S. J. Sparks Antonio Costa А. А. Бармин

Lava dome

Dome (geology)

Effusive eruption

10.1007/978-1-0716-1705-2_578

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Citations (1)

Comment on: ‘The structure and petrogenesis of the Trallval and Ruinsival areas of the Rhum ultrabasic pluton’ by J. A. Volker and B. G. J. Upton

Transactions of the Royal Society of Edinburgh Earth Sciences (1991)

Jean H. Bédard R. S. J. Sparks

Volker and Upton (VU) have provided an excellent contribution to the study of the Rhum complex, providing substantial amounts of descriptive material and new observationsto allow the discussion to rise above mere opinion. VU disagree with two of our (Bédard et al. 1988) principal conclusions about the genesis of the Eastern Layered Series. We argue in the following comment that, on the contrary, their data support and complement our conclusions.

Petrogenesis

Ultramafic rock

Complement

10.1017/s0263593300004223

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Citations (5)

Thermal and mechanical constraints on mixing between mafic and silicic magmas

Journal of Volcanology and Geothermal Research (1986)

R. S. J. Sparks Leandra Marshall

Silicic

Igneous differentiation

Magma chamber

Xenolith

10.1016/0377-0273(86)90041-7

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Citations (628)

Fall-out and deposition of volcanic ash during the 1979 explosive eruption of the soufriere of St. Vincent

Journal of Volcanology and Geothermal Research (1982)

S. Brazier A. N. Davis Haraldur Sigurdsson R. S. J. Sparks

Lapilli

Volcanic ash

Submarine volcano

Deposition

10.1016/0377-0273(82)90069-5

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Citations (77)

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)