Steven Carey - Profile on Academia.edu (original) (raw)

Papers by Steven Carey

Proceedings of the Ocean Drilling Program, 1997

Influence of magma withdrawal on compositional gradients during the AD 79 Vesuvius eruption

Nature, 1990

... been used as indicators of pre-eruptive chemical gradients in magma chambers and of processes... more ... been used as indicators of pre-eruptive chemical gradients in magma chambers and of processes leading to compositional stratification 1,2 . Theoretical studies of the fluid dynamics of magma withdrawal from stratified chambers have shown ... 5. Blake, S. & Ivey, GN J. Volcan. ...

Earth and Planetary Science Letters, 2022

The lateral collapse of Anak Krakatau volcano, Indonesia, in December 2018, highlighted the poten... more The lateral collapse of Anak Krakatau volcano, Indonesia, in December 2018, highlighted the potentially devastating impacts of volcanic edifice instability. The trigger for the Anak Krakatau collapse remains obscure; the volcano had been erupting for the previous six months, and although failure was followed by intense explosive activity, it is the period immediately prior to collapse that is potentially key in providing identifiable, pre-collapse warning signals. Here, we integrate physical, microtextural and geochemical characterisation of tephra deposits spanning the collapse period. We demonstrate that the first post-collapse eruptive phase (erupting juvenile clasts with a low microlite areal number density and relatively large microlites, reflecting crystal growth) is best explained by instantaneous unloading of a relatively stagnant upper conduit. This was followed by the second post-collapse phase, on a timescale of hours, which tapped successively deeper portions of the plumbing system, reflected in highly anorthitic microlite populations, alongside higher calculated ascent velocities and decompression rates, within the post-collapse tephra-stratigraphy. This implies downward propagating destabilisation of the magma storage system, as a response to collapse, rather than pre-collapse magma ascent triggering failure. Importantly, this suggests that the collapse was a consequence of longer-term processes linked to edifice growth and instability, and that no indicative changes in the magmatic system could have signalled the potential for incipient failure. Therefore, monitoring efforts may need to focus on integrating short-and long-term edifice growth and deformation patterns to identify increased susceptibility to lateral collapse. The post-collapse eruptive pattern also suggests a magma pressurisation regime that is highly sensitive to surface-driven perturbations, which led to elevated magma fluxes after collapse and rapid edifice regrowth. Not only does rapid regrowth potentially obscure evidence of past collapses, but it also emphasises the finely balanced relationship between edifice loading and crustal magma storage.

Marine Geology, 2020

Extensive carbonate crusts discovered forming on the slopes of seamounts in many parts of the wor... more Extensive carbonate crusts discovered forming on the slopes of seamounts in many parts of the world's oceans are providing extra stability to the volcanic edifices. These crusts are composed of mixtures of volcaniclastic debris and bioclastic material, in most cases cemented by calcite, in the form of isopachous coatings around grains and pore-filling spar. Such crusts, which have been collected by remotely-operated vehicle (ROV), are described here from moderate-depth to deeper-water slopes (200-1000 m) around the volcanic island of Montserrat in the Caribbean, and from the nearby Kick'em Jenny submarine volcano off Grenada. Radiogenic 87 Sr /86 Sr isotope ratios from the carbonates give an indication of age but also demonstrate that some samples have been altered by hydrothermal-volcanic processes, as shown by ages much older than expected. Such alteration is also supported by carbon and oxygen isotope ( 13 C and  18 O) ratios, although most samples have typical marine values. In many cases  18 O is usually a little more positive than expected from modern shallow-water carbonates, likely reflecting cooler water at the depth of lithification. Just one sample, from Kick'em Jenny, has very negative  13 C (-42 ‰) indicating methanogenesis. Crusts are also reported here from the Mediterranean Sea, with an example described from Kolumbo, northeast of the Santorini volcanic complex in the Hellenic subduction zone, that are similar in many respects to those from the Caribbean. Typically, the biota of the crusts consists of calcareous red algae (commonly encrusting volcanic clasts), benthic (also encrusting) and planktic foraminifera, subordinate serpulids, bivalves, pteropods and heteropods, and rare deeper-water corals. In addition, there is evidence for the former presence of microbes from the occurrence of calcified filaments and peloids in intragranular cavities. Several generations of sponge borings are usually present as well as calcite cement. The carbonate crusts are attributed to seawater circulating within the surficial sediment, in some cases mixing with hydrothermal fluid. The significance of these crusts is in stabilising seamounts, enabling their 3 slopes to avoid frequent collapse, dissection and readjustment, but when failure does occur, larger-scale submarine landslides involving coherent slabs are more likely.

Marine Geology, 2019

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Scientific Reports, 2019

On Dec. 22, 2018, at approximately 20:55–57 local time, Anak Krakatau volcano, located in the Sun... more On Dec. 22, 2018, at approximately 20:55–57 local time, Anak Krakatau volcano, located in the Sunda Straits of Indonesia, experienced a major lateral collapse during a period of eruptive activity that began in June. The collapse discharged volcaniclastic material into the 250 m deep caldera southwest of the volcano, which generated a tsunami with runups of up to 13 m on the adjacent coasts of Sumatra and Java. The tsunami caused at least 437 fatalities, the greatest number from a volcanically-induced tsunami since the catastrophic explosive eruption of Krakatau in 1883 and the sector collapse of Ritter Island in 1888. For the first time in over 100 years, the 2018 Anak Krakatau event provides an opportunity to study a major volcanically-generated tsunami that caused widespread loss of life and significant damage. Here, we present numerical simulations of the tsunami, with state-of the-art numerical models, based on a combined landslide-source and bathymetric dataset. We constrain th...

Nature Communications, 2016

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different e... more Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0–2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami prod...

POSTER PRESENTATION THALATTA 2012, 22-23 September 2012, Santorini, Greece

1891 Submarine eruption of Foerstner volcano (Pantelleria, Sicily): insights into the vent structure of basaltic balloon eruptions

Bulletin of Volcanology, 2016

Kick-'em-Jenny (KeJ)-located ca. 8 km north of the island of Grenada-is the only active submarine... more Kick-'em-Jenny (KeJ)-located ca. 8 km north of the island of Grenada-is the only active submarine volcano of the Lesser Antilles Volcanic Arc. Previous investigations of KeJ revealed that it lies within a collapse scar inherited from a past flank instability episode. To assess the likelihood of future collapse, we employ here a combined laboratory and modeling approach. Lavas collected using a remotely operated vehicle (ROV) provided samples to perform the first rock physical property measurements for the materials comprising the KeJ edifice. Uniaxial and triaxial deformation experiments showed that the dominant failure mode within the edifice host rock is brittle. Edifice fractures (such as those at Champagne Vent) will therefore assist the outgassing of the nearby magma-filled conduit, favoring effusive behavior. These laboratory data were then used as input parameters in models of slope stability. First, relative slope stability analysis revealed that the SW to N sector of the volcano displays a deficit of mass/volume with respect to a volcanoid (ideal 3D surface). Slope stability analysis using a limit equilibrium method (LEM) showed that KeJ is currently stable, since all values of stability factor or factor of safety (Fs) are greater than unity. The lowest values of Fs were found for the SW-NW sector of the volcano (the sector displaying a mass/volume deficit). Although currently stable, KeJ may become unstable in the future. Instability (severe reductions in Fs) could result, for example, from overpressurization due to the growth of a cryptodome. Our modeling has shown that instabilityinduced flank collapse will most likely initiate from the SW-NW sector of KeJ, therefore mobilizing a volume of at least ca. 0.7 km 3. The mobilization of ca. 0.7 km 3 of material is certainly capable of generating a tsunami that poses a significant hazard to the southern islands of the West Indies.

$Research paper thumbnail of Marine Investigations of Greece\u27s Santorini Volcanic Field$

The most recent major explosive eruption of the Santorini volcano in Greece—around 3600 years bef... more The most recent major explosive eruption of the Santorini volcano in Greece—around 3600 years before present (B.P.), often referred to as the Minoan eruption—is one of the largest volcanic events known in historical time and has been the subject of intense volcanological and archeological studies [Druitt et al., 1999]. The submarine volcano Kolumbo, located seven kilometers northeast of Santorini and associated with Santorini\u27s tectonic system, erupted explosively in 1650 A.D., resulting in fatalities on the island of Thera [Fouqué, 1879]. A large fraction of the erupted products from the Minoan eruption has been deposited in the sea but, up to now, only has been studied in distal marine sediments. As part of a collaborative project between the University of Rhode Island (Narragansett), the Hellenic Centre of Marine Research (Athens, Greece), and the Institute of Geology and Mineral Exploration (Athens), a marine geological survey was conducted around Santorini from April to June...

Depositional processes in the collision zone between the North d'Entrecasteaux Ridge (NDR) an... more Depositional processes in the collision zone between the North d'Entrecasteaux Ridge (NDR) and the New Hebrides Island Arc were investigated in post-cruise analyses of sediment and nannofossils from Sites 827, 828, and 829. Reexamination of cores and analysis of grain size, turbidite frequency, carbonate content, and clay mineralogy, together with new nannofossil age determinations, were used to revise shipboard lithostratigraphies and interpret the sedimentologic history recorded at each site.The results of our analyses show that sedimentation on the inner trench slope and the impinging NDR has been significantly affected by the collision process. Uplift associated with subduction of the NDR beneath the New Hebrides Island Arc resulted in the emergence of Espiritu Santo Island and created a robust source of epiclastic sediment for the forearc area. Distribution of this material into deeper water has been modulated by Pleistocene sea level changes, which have influenced the freq...

An unusual deposit of Fe-rich hydrothermal nontronite was recovered by remotely operated vehicle ... more An unusual deposit of Fe-rich hydrothermal nontronite was recovered by remotely operated vehicle (ROV) from Seamount 3 of the Wolf-Darwin lineament, Galapagos Marine Reserve. X-ray diffraction, ICP-MS/ICP-AES, and SEM-EDS analyses show that this deposit is chemically and mineralogically similar to other deep-sea hydrothermal nontronites, indicating a formation temperature of about 30o to 50o Celsius. These Fe-Si-oxides and Fe-rich Al-poor nontronite deposits contain about 38-51 weight % SiO2 and 40-50 weight % Fe2O3. Although hydrothermal nontronite has been sampled at a number of sites by coring and dredging, this is the first in situ documentation of its sinuous, tubular structure on the seafloor. Imageanalysis of ROV imagery suggests that this unusual pattern might be controlled by fluid pathways in the underlying pillow lavas.

Geochemistry, Geophysics, Geosystems, 2016

Kick'em Jenny is a frequently erupting, shallow submarine volcano located 7.5 km off the northern... more Kick'em Jenny is a frequently erupting, shallow submarine volcano located 7.5 km off the northern coast of Grenada in the Lesser Antilles subduction zone. Focused and diffuse hydrothermal venting is taking place mainly within a small (70 3 110 m) depression within the 300 m diameter crater of the volcano at depths of about 265 m. Much of the crater is blanketed with a layer of fine-grained tephra that has undergone hydrothermal alteration. Clear fluids and gas are being discharged near the center of the depression from mound-like vents at a maximum temperature of 1808C. The gas consists of 93-96% CO 2 with trace amounts of methane and hydrogen. Gas flux measurements of individual bubble streams range from 10 to 100 kg of CO 2 per day. Diffuse venting with temperatures 5-358C above ambient occurs throughout the depression and over large areas of the main crater. These zones are colonized by reddish-yellow bacteria with the production of Fe-oxyhydroxides as surface coatings, fragile spires up to several meters in height, and elongated mounds up to tens of centimeters thick. A high-resolution photomosaic of the inner crater depression shows fluid flow patterns descending the sides of the depression toward the crater floor. We suggest that the negatively buoyant fluid flow is the result of phase separation of hydrothermal fluids at Kick'em Jenny generating a dense saline component that does not rise despite its elevated temperature.

Proceedings of the Ocean Drilling Program, 157 Scientific Results, 1998

Site 953 recovered a 14.8-Ma record of volcaniclastic sedimentation adjacent to Gran Canaria Isla... more Site 953 recovered a 14.8-Ma record of volcaniclastic sedimentation adjacent to Gran Canaria Island of the Canary Island archipelago. Changes in the lithology, age, and volume of clastic material reflect the evolution of Gran Canaria from a submarine stage to a mature subaerial edifice. Before the initiation of major felsic explosive volcanism on Gran Canaria at 14.0 Ma, there was a period during which numerous mafic volcaniclastic turbidites were generated from the emergent island (Unit V, Site 953). The deposits consist of sand-to silt-sized mixtures of altered sideromelane, tachylite, small clasts of microcrystalline basalt, and crystals of clinopyroxene, feldspar, and Fe-Ti oxides. Biogenic components, such as foraminifer fragments, make up as much as 30%. Computer-assisted fractal analysis of sideromelane grain morphologies shows a decrease in morphological complexity with increasing age through Unit V. This change, along with a decrease in the modal abundance of tachylite with increasing age, is interpreted to represent an increasing role of deeper, submarine volcanism as the source of clastic particles early in the island's development. The strongly mixed lithologies of the turbidites and the occurrence of common, rounded microcrystalline basalt fragments suggest that many of the layers were formed by the slumping of volcaniclastic material that had accumulated in shallow water from erosion of subaerial products, the entrance of lava flows into the sea, and shallow submarine eruptions. A median frequency of one flow event every 2000 yr has been determined from the thickness and accumulation rate of interbedded pelagic sediment in Unit V.

Mapping of a debris Avalanche Offshore Santorini Volcano

Natural Hazards, 2012

Kolumbo submarine volcano, located NE of Santorini caldera in the Aegean Sea, has only had one re... more Kolumbo submarine volcano, located NE of Santorini caldera in the Aegean Sea, has only had one recorded eruption during historic times (1650 AD). Tsunamis from this event severely impacted the east coast of Santorini with extensive flooding and loss of buildings. Recent seismic studies in the area indicate a highly active region beneath Kolumbo suggesting the potential for future eruptive activity. Multibeam mapping and remotely operated vehicle explorations of Kolumbo have led to new insights into the eruptive processes of the 1650 AD eruption and improved assessments of the mechanisms by which tsunamis were generated and how they may be produced in future events. Principal mechanisms for tsunami generation at Kolumbo include shallow submarine explosions, entrance of pyroclastic flows into the sea, collapse of rapidly accumulated pyroclastic material, and intense eruption-related seismicity that may trigger submarine slope collapse. Compared with Santorini, the magnitude of explosive eruptions from Kolumbo is likely to be much smaller but the proximity of the volcano to the eastern coast of Santorini presents significant risks even for lower magnitude events.

Journal of Volcanology and Geothermal Research, 2014

Kolumbo submarine volcano, located 7 km northeast of Santorini, Greece in the Aegean Sea, last er... more Kolumbo submarine volcano, located 7 km northeast of Santorini, Greece in the Aegean Sea, last erupted in 1650 AD. Submarine and subaerial explosive activity lasted for a period of about four months and led to the formation of thick (~250 m) highly stratified pumice deposits on the upper crater walls as well as extensive pumice rafts that were dispersed throughout the southern Aegean Sea. Subaerial tephra fallout from eruption columns that breached the surface occurred as far east as Turkey. Remotely operated vehicle (ROV) video observations from transects of the northern and southwestern crater walls have been used to create stratigraphic sequences of the 1650 AD deposits. Petrographic and geochemical analyses reveal that the bulk of the deposits consists of white, highly vesicular, sparsely porphyritic, biotitebearing rhyolite pumice. Pre-eruption volatile contents determined from plagioclase-hosted melt inclusions yield a median value of 6.5 wt.%. This corresponds to a pre-eruption storage pressure of~200 MPa, or a depth of~6 km assuming a H 2 O-saturated magma. Comparison of the natural glass compositions and mineral assemblage of the Kolumbo samples with experimental results on other rhyolite magmas of similar composition in the modified haplogranite system supports the pressure and total volatile estimates. Pre-eruption temperature was calculated as 750°C based on plagioclase-melt geothermometry. The high volatile content of the Kolumbo magma and historical accounts of substantial subaerial eruption plumes suggest that the explosive eruption was driven by primary volatile degassing. Three phases of activity can be inferred from historical accounts and deposit stratigraphy; an initial submarine eruption during which time the vent became shallower as pyroclastic material accumulated, a transitional phase with substantial fallout from a hybrid submarine/subaerial eruption plume, and a final subaqueous phase as the eruption waned. Depositional processes included a complex interplay of submarine fallout, pyroclastic density currents, and clast segregation associated with the transition from submarine to subaerial plumes, producing a highly stratified pumiceous sequence. This is the first study of the in situ pyroclastic deposits of a well-documented silicic submarine explosive eruption in the relatively shallow (b500 m below sea level) marine environment.