Dome Collapse Research Articles

Gas storage, transport and pressure changes in an evolving permeable volcanic edifice

The total volume of gas in a magma, dissolved and subsequently exsolved, greatly influences the degree of explosiveness of a volcanic system. There is a marked contrast between the behaviour of a volcano in an “open” system compared to one which is “closed”. It is therefore essential to understand the entire degassing process: gas transport, storage and loss. A particular focus of this study is the effect different permeabilities and pressure gradients within a volcanic edifice have on the degree and pattern of the gas velocity. Gas loss is modelled numerically in two dimensions using a finite element approach, which allows the specification of boundary conditions with respect to pressure and different permeability domains within the volcanic edifice. By combining the time‐dependent continuity equation and Darcy's law, a partial differential equation is derived and solved for the pressure. The associated pressure gradient is then used within Darcy's law to determine the corresponding gas velocity distribution. This method is used not only for stationary systems in equilibrium, but also as a time-dependent progression. It permits the modelling of different situations to study how various volcanic characteristics affect the gas loss. The model is used to investigate the change in pressure and gas in response to time‐dependent scenarios. These are a dome collapse or sudden increase in permeability by magma rupture at the conduit margin, the formation of cracks within the lava dome and sealing by crystallisation.Our results show that a combination of high and low permeability regions is required for effective gas storage. High permeability allows the gas to enter the system, but impermeable areas act to confine the gas, thereby increasing its pressure and consequently, increasing the amount of gas which may be dissolved in the melt. Furthermore, our results show that permeability is an essential factor influencing the response time to system changes, which could be linked in future to deformation and other geophysical observations. Our model is highly versatile and sheds new light on the understanding of gas storage and transport in a permeable volcanic edifice.

Cyclic extrusion of a lava dome based on a stick-slip mechanism

Lava dome eruptions are sometimes characterised by large periodic fluctuations in extrusion rate over periods of hours that may be accompanied by Vulcanian explosions and pyroclastic flows. We consider a simple system of nonlinear equations describing a 1D flow of lava extrusion through a deep elastic dyke feeding a shallower cylindrical conduit in order to simulate this short-period cyclicity. Stick-slip conditions depending on a critical shear stress are assumed at the wall boundary of the cylindrical conduit. By analogy with the behaviour of industrial polymers in a plastic extruder, the elastic dyke acts like a barrel and the shallower cylindrical portion of the conduit as a die for the flow of magma acting as a polymer. When we applied the model to the Soufrière Hills Volcano, Montserrat, for which the key parameters have been evaluated from previous studies, cyclic extrusions with periods from 3 to 30h were readily simulated, matching observations. The model also reproduces the reduced period of cycles observed when a major unloading event occurs due to lava dome collapse.

The 2010 explosive eruption of Java's Merapi volcano—A ‘100-year’ event

Merapi volcano (Indonesia) is one of the most active and hazardous volcanoes in the world. It is known for frequent small to moderate eruptions, pyroclastic flows produced by lava dome collapse, and the large population settled on and around the flanks of the volcano that is at risk. Its usual behavior for the last decades abruptly changed in late October and early November 2010, when the volcano produced its largest and most explosive eruptions in more than a century, displacing at least a third of a million people, and claiming nearly 400 lives. Despite the challenges involved in forecasting this ‘hundred year eruption’, we show that the magnitude of precursory signals (seismicity, ground deformation, gas emissions) was proportional to the large size and intensity of the eruption. In addition and for the first time, near-real-time satellite radar imagery played an equal role with seismic, geodetic, and gas observations in monitoring eruptive activity during a major volcanic crisis. The Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) issued timely forecasts of the magnitude of the eruption phases, saving 10,000–20,000 lives. In addition to reporting on aspects of the crisis management, we report the first synthesis of scientific observations of the eruption. Our monitoring and petrologic data show that the 2010 eruption was fed by rapid ascent of magma from depths ranging from 5 to 30km. Magma reached the surface with variable gas content resulting in alternating explosive and rapid effusive eruptions, and released a total of ~0.44Tg of SO2. The eruptive behavior seems also related to the seismicity along a tectonic fault more than 40km from the volcano, highlighting both the complex stress pattern of the Merapi region of Java and the role of magmatic pressurization in activating regional faults. We suggest a dynamic triggering of the main explosions on 3 and 4 November by the passing seismic waves generated by regional earthquakes on these days.

Failure Modes for Single-Layer Reticulated Domes under Oblique Impact

FE models of both the single-layer Kiewitt-8 reticulated domes with a span of 60m and the cylindrical impactor were developed incorporating ANSYS/LS-DYNA. Afterward, fourteen groups impact are simulated by changing the impact position or impacted angle on reticulated dome, and impact velocity and mass of impactor are changed for each group impact. On the basis of large numbers of numerical simulations, characteristics of dynamic response for reticulated dome under impact are shown. And four failure modes (Members slightly damaged, Local collapse of dome, Global collapse of dome, Members shear failed) are presented for single-layer Kiewitt-8 reticulated dome under diverse impact. The distributing of failure modes for the fourteen types impact are different from each other, and the adverse position and angle are summrized.

Constraining the degassing processes of Popocatépetl Volcano, Mexico: A vesicle size distribution and glass geochemistry study

The explosive activity of Popocatépetl Volcano is a threat to the surrounding densely populated areas and it is therefore important to recognize indicators of change in eruptive style (explosive to dome building) within a short period of time. In this study we present results of vesicle size distributions (VSDs) and compositional analysis of matrix glass from juvenile clasts from five of the main plinian eruptions of Popocatépetl (ca. 23–1.2ka), the 2001 small eruption during partial dome collapse and four eruptions during 1997 (May 11th and June 14th, 15th and 30th). Major element analysis of matrix glass (WDS-EPMA) allows the estimation of the depth from which the erupted magma went into disequilibrium (between crystals and melt), by calculating the equilibrium pressure using the quartz–albite–orthoclase ternary system of Blundy and Cashman (2001). Quantitative interpretation of texture in juvenile (pumice or scoria) clasts via VSD analysis using CSD software was used to link physical changes experienced by magma during ascent, with conditions responsible for eruptions. The extent and style of vesiculation in juvenile clasts is also related to eruption style and duration and has specifically allowed the recognition of changes in vesicular texture that represent variations from explosive to dome building activity (Mangan and Sisson, 2000; Adams et al., 2006). This study highlights a more complicated story in terms of magma storage, than that previously accepted for the Popocatépetl volcanic system and is an important contribution to ongoing research at the volcano.

Surface textures and dynamics of the 2005 lava dome at Shiveluch volcano, Kamchatka

Shiveluch is one of the largest and most active andesitic volcanoes of the Kuril-Kamchatka arc. It commonly alternates between Vulcanian explosive eruptions and periods of dome growth and subsequent dome collapse–driven block-and-ash flows. The volcano was in an extended period of heightened activity for most of the period 2004–2010. We examined this activity in detail using thermal infrared (TIR) remote sensing as part of the urgent request protocol (URP) program of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument and confirmed the results with ground-based photography and airborne TIR camera data. High-spatial-resolution TIR images were collected during both daytime and nighttime satellite overpasses prior to and following the large explosive event/eruption of 27 February 2005 and the dome growth that followed. During a field campaign in August 2005, a helicopter overflight designed to acquire visible and TIR data of the active dome was performed. This was a nadir-looking, low-altitude overflight and the first ever of Shiveluch volcano involving non-Russian scientists. The image data revealed an active crease structure in the center of the dome with a distinctly different, crescent-shaped, high-temperature (>380 °C) zone roughly perpendicular to the crease. In order to provide a time context and estimate extrusion rates, the airborne data were compared to the spaceborne ASTER data and long-distance ground-based photography of the dome acquired by our Russian colleagues. The presence of a crease structure and the complex thermal pattern on the surface were both unexpected discoveries that reveal the way in which exogenous dome growth was occurring at the time. This highly active period at Shiveluch provides a unique example to better understand silicic lava dome growth using TIR data. The results also demonstrate a straightforward approach for fusing ground, air, and spaceborne image data, which could be applied to other active domes around the world.

Block‐and‐ash flow deposit of the Narcondam Volcano: Product of dacite–andesite dome collapse in the Burma–Java subduction complex

AbstractNarcondam Island in the Andaman Sea represents a dacite–andesite dome volcano in the volcanic chain of the Burma–Java subduction complex. The pyroclasts of andesitic composition are restricted to the periphery of the dome predominantly in the form of block‐and‐ash deposits and minor base surge deposits. Besides pyroclastic deposits, andesitic lava occurs dominantly at the basal part of the dome whereas dacitic lava occupies the central part of the dome. The pyroclasts are represented by non‐vesiculated to poorly vesiculated blocks of andesite, lapilli, and ash. The hot debris derived from dome collapse was deposited initially as massive to reversely‐graded beds with the grain support at the lower part and matrix support at the upper part. This sequence is overlain by repetitive beds of lapilli breccia to tuff breccia. These deposits are recognized as a basal avalanche rather than lahar deposit. This basal avalanche was punctuated by an ash‐cloud surge deposit representing a sequence of thinly bedded units of normal graded unit to parallel laminated beds.

Effects of volcano profile on dilute pyroclastic density currents: Numerical simulations

Explosive activity and lava dome collapse at stratovolcanoes can lead to pyroclastic density currents (PDCs; mixtures of volcanic gas, air, and volcanic particles) that produce complex deposits and pose a hazard to surrounding populations. Two-dimensional computer simulations of dilute PDCs (characterized by a turbulent suspended load and deposition through a bed load) show that PDC transport, deposition, and hazard potential are sensitive to the shape of the volcano slope (profile) down which they flow. We focus on three generic volcano profiles: straight, concave-upward, and convex-upward. Dilute PDCs that flow down a constant slope gradually decelerate over the simulated run-out distance (5 km in the horizontal direction) due to a combination of sedimentation, which reduces the density of the PDC, and mixing with the atmosphere. However, dilute PDCs down a concave-upward slope accelerate high on the volcano flanks and have less sedimentation until they begin to decelerate over the shallow lower slopes. A convex-upward slope causes dilute PDCs to lose relatively more of their pyroclast load on the upper slopes of a volcano, and although they accelerate as they reach the lower, steeper slopes, the acceleration is reduced because of the upstream loss of pyroclasts (lower density contrast with the atmosphere). Dynamic pressure, a measure of the damage that can be caused by PDCs, reflects these complex relations.

Submarine pyroclastic deposits formed during the 20th May 2006 dome collapse of the Soufrière Hills Volcano, Montserrat

The 20th May 2006 lava dome collapse of the Soufriere Hills Volcano, Montserrat, had a total non-dense rock equivalent (non-DRE) collapse volume of approximately 115 × 106 m3. The majority of this volume was deposited into the ocean. The collapse was rapid, 85% of the mobilized volume being removed in just 35 min, giving peak pyroclastic flow flux of 66 × 103 m3 s−1. Channel and levee facies on the submarine flanks of the volcano and formation of a thick, steep-sided ridge, suggest that the largest and most dense blocks were transported proximally as a high concentration granular flow. Of the submerged volume, 30% was deposited from the base of this granular flow, forming a linear, high-relief ridge that extends 7 km from shore. The remaining 70% of the submerged volume comprises the finer grain sizes, which were transported at least 40 km by turbidity currents on gradients of <2°. At several localities, the May 2006 distal turbidity currents ran up 200 m of topography and eroded up to 20 cm of underlying substrate. Multiple turbidites are preserved, representing current reflection from the graben margins and deflection around topography. The high energy of the May 2006 collapse resulted in longer submarine run out than the larger (210 × 106 m3) Soufriere Hills dome collapse in July 2003.

Reduction of Irreducible Hawkins III Talar Neck Fracture by Means of a Medial Malleolar Osteotomy: A Report of Three Cases With a 4-Year Mean Follow-Up

We report three cases of a closed Hawkins III talar neck fracture in which the posteromedially dislocated talar body was irreducible even with combined anteromedial and anterolateral approaches. Our intraoperative solution was to proceed with a medial malleolar osteotomy, which resulted in an easy reduction. The combined incisions provided excellent exposure for anatomic reduction and rigid internal fixation. At a mean follow-up of 4 years, all fractures had healed with no evidence of avascular necrosis or talar dome collapse.

Explosive volcanism as a cause for mass mortality of pteropods

Recently, it has been proposed that anthropogenic CO 2 emissions may affect marine ecosystems by causing ocean acidification. In particular, it is suggested that within acidified waters, calcifying organisms would be subject to malformation and enhanced dissolution. Here, we present evidence suggesting that this process occurs naturally where explosive volcanism deposits ash directly into ocean surface waters. Sediment cores from around the island of Montserrat, Lesser Antilles volcanic arc, contain distinct horizons of planktic fauna associated with recently deposited volcanic ash layers from the Soufrière Hills volcano. Within these layers are abundant thecosome pteropod shells that display evidence of partial dissolution and etching of their aragonitic shells, and appear to have suffered mass mortality during large eruptions from the volcano. Laboratory studies show that the acids bound to ash surfaces from the 2003 volcanic dome collapse event of the Soufrière Hills volcano could have caused the upper 5 m of the water column to become undersaturated with respect to aragonite. When combined with the large fluxes of acidic aerosols (principally as SO 2) from the volcano during eruptions, it is proposed that volcanogenic ocean acidification by marine ash falls is a significant contributing factor to these observed mass mortality events.

Triggering of a volcanic dome collapse by rainwater infiltration

The thermodynamic processes in a one‐dimensional model of a porous lava dome are considered in the presence of a rising magmatic gas flux through the void spaces and rainfall interacting with the dome surface. The steady state surface temperature of the dome depends on both magmatic gas mass flux and rainfall rate. A critical rainfall rate is determined, that cools the dome surface to 100°C. Rainfall rates above this critical value allow liquid infiltration into the void spaces of the dome, thus restricting the escape of magmatic gas. A model which restricts the gas flow through the surface predicts internal gas pressures much higher than the overburden pressure in the top few meters, approximately one hour after the onset of rainfall. For a marginally stable dome, this could cause small Vulcanian explosions, which (depending on their location) could trigger a dome collapse, on a timescale consistent with observations.

Seismic characterization of the fall 2007 eruptive sequence at Bezymianny Volcano, Russia

We examine an eruptive sequence in late 2007 at Bezymianny Volcano to characterize the magmatic plumbing system and eruption-related seismicity. Earthquake locations reveal seismicity below and offset to the north of the volcano along a tectonic fault. Based on historical seismicity, the magma chamber is postulated to have a top at about 6 km depth. Minor dome explosions, large sub-plinian eruptions and dome collapses are analyzed using an automated event classification scheme. Low-frequency tremor, interpreted as gas escape, and low-frequency earthquakes are a dominant proportion of the energy released. We also examine multiplet earthquakes whose behavior during the study period changed significantly and systematically before the largest eruption, demonstrating the potential of tracking multiplets to assess changing conditions with the conduit.

The 2006 pyroclastic deposits of Merapi Volcano, Java, Indonesia: High-spatial resolution IKONOS images and complementary ground based observations

On 16 June 2006 an overpass of IKONOS coincided with the emplacement of an active block-and-ash flow fed by a lava dome collapse at Merapi Volcano (Java, Indonesia). It was the first moving pyroclastic flow recorded on a satellite image. The very high-spatial resolution of the image indicated the extent and impact of pyroclastic material that was deposited during and prior to the day of image acquisition. A number of features associated with the hazardous block-and-ash flows emplaced in narrow, deep gorges were mapped, interpreted and analysed. The high-spatial-resolution IKONOS imagery worked extremely well for identifying pyroclastic deposits. The block-and-ash flow and surge deposits recognized in the IKONOS images include: (1) several channel-confined flow lobes and tongues in the box-shaped gorge; (2) thin ash-cloud surge deposit and knocked-down trees in constricted areas on both slopes of the gorge; (3) fan-like overbank deposits on the Gendol–Tlogo interfluves from which flows were re-routed in the Tlogo minor valley; (4) massive overbank flow lobes on the right bank of the Gendol River, which destroyed the village of Kaliadem 0.5 km from the main channel. A small part of this flow was re-channelled into the Opak tributary valley. The high-resolution IKONOS images also helped us to identify geomorphic obstacles that enabled flows to ramp up and spill out from the sinuous channel, as flow avulsion. Flow avulsions are dangerous as the redirect flows to unexpected areas away from the main channel. Valley fills from previous deposits, channel bends, and anthropogenic barriers in the channel (locally known as Sabo dams) influence the down valley passage of the flows. Sabo dams, originally built to ameliorate the effect of high sediment load streams, caused block-and-ash flows to avulse of the containing channel, and devastate populated areas.

Sediment-charged flash floods on Montserrat: The influence of synchronous tephra fall and varying extent of vegetation damage

On 20th May 2006 the Soufrière Hills Volcano on the Caribbean island of Montserrat experienced a large dome collapse and intense rainfall generated flash floods. The floods had very high loads of volcanic debris derived both from this and previous eruptions and can thus be classified as lahars. The floods reached unusually high water levels and caused substantial geomorphic change in the Belham Valley. Detailed rainfall and geomorphological data, coupled with the precise timing of events and yewitness accounts have facilitated an assessment of the relative importance of rainfall volume and intensity, older volcanic debris, pre- and syn-flood tephra fall and the extent of pre-flood vegetation damage for the behavior of this and subsequent sediment-laden floods in this setting. The change in runoff behavior was controlled by preexisting vegetation damage and synchronous tephra fall and this was critically important in controlling the impact of these flash floods. Although rainfall intensity and volume have some control on flood occurrence they are not the critical control on flash flood impact on the geomorphology in the Belham Valley. A significant conclusion of this study is that the extreme nature of the flash floods was not caused by extreme rainfall (as is commonly believed to be the primary cause of flash floods) but rather it was the result of changed runoff behaviour caused by the widespread syn-flood tephra deposition and importantly the widespread vegetation damage by volcanic-associated acid rain in the preceding weeks.

Injection of vesicular magma into an andesitic dome at the effusive–explosive transition

A single, vesicular pyroclast collected from a major (11×106m3) dome collapse eruption of the Soufrière Hills volcano, Montserrat (21st September 1997) was found to contain textural and Raman evidence for multiple decompression events and magma injection into the dome just prior to the onset of dome collapse. Quartz, plagioclase and hornblende phenocrysts contain closed and burst melt inclusions (MIs), the latter in the form of either foam or cylindrical melt extrusions from cavities on fracture surfaces. Fractures within ruptured quartz phenocrysts were infilled with glass, whereas those within plagioclase are entirely free of glass, indicating relatively early fracturing (decompression) of the quartz. This interpretation is supported by slightly higher measured H2OT in burst MIs in quartz (0.44wt.%±0.07, 1s.d.) compared with plagioclase (0.31wt.%±0.05, 1s.d.), indicating equilibration on rupturing of the quartz at higher PH2O. H2OT levels in glass from burst MIs in plagioclase are consistent with plagioclase fragmentation at H2O saturation pressures <5MPa, at an estimated depth of <210m, within the dome. The fragmentation occurred whilst the groundmass glass was still plastic, as evident from the presence of stretched vesicles in glass at fracture terminations. The fractures in plagioclase are empty of vapour phase precipitates (mainly cristobalite that infills matrix vesicles) which constrains the fracturing of plagioclase to the last depressurisation event recorded in the pyroclast, which was the dome collapse which led to the pyroclast being ejected from the dome. We suggest that our study provides the first direct (i.e. non seismic) evidence for the injection of gas-charged magma into the dome at the onset of dome collapse, marking the transition from effusive to explosive eruption, and that the magma injection could have provided the triggering mechanism for dome collapse.

Lava dome collapse detected using passive seismic interferometry

[1] The collapse of the lava dome at the Soufriere Hills Volcano on Montserrat in July 2003 is the largest recorded in historical times. I use noise correlation Green's functions to measure the changes in seismic properties that resulted from this collapse. Continuous three component seismic data recorded at two pairs of stations were cross-correlated to retrieve three-component Green's functions along two paths that intersect the volcanic edifice before and after the dome collapse. Particle motion analysis shows that the Green's functions are dominated by Rayleigh waves and are consistent with the expected Green's tensor for a vertical point force source at one station recorded by a three-component receiver at the other. Following the collapse, there is a clear decorrelation and phase shift in the Green's functions corresponding to a change in velocity of approximately 0.5% that can be interpreted in terms of the unloading of the lava dome.

In situ measurements of plagioclase growth using SIMS depth profiles of 7Li/30Si: A means to acquire crystallization rates during short-duration decompression events

Numerous petrologic studies have attempted to determine crystal growth rates in volcanic systems through several methods, including analyses of crystal size distributions in natural samples and decompression experiments on hydrous magmas. Experiments have revealed that rim growth on existing crystals will occur under a wide range of decompression conditions and is favored under conditions of low to moderate undercoolings over microlite nucleation, which has typically been the focus of decompression-induced crystallization studies. For this study, samples of eruptive clasts were collected from a Vulcanian explosion that occurred following the July 12-13, 2003 dome collapse of Soufrière Hills volcano, Montserrat. Plagioclase phenocrysts were extracted and examined with secondary ion mass spectrometry (SIMS) depth profiling. Lithium inflection depths within the profiles, along with the observed time interval between the peak in the collapse decompression and the explosion that ejected the examined samples, were used to calculate the growth rates as a result of magma devolatilization, with an average of 8.3 × 10 -8 mm/s. Anorthite content of the plagioclase rim growth indicates an average decompression magnitude of 40 MPa, inducing an undercooling of ~45 °C that favors crystal growth over microlite nucleation. However, variability in the final anorthite contents suggests that not all phenocrysts recorded an equilibrium composition reflecting accurate pressure conditions. In such events occurring over short timescales (&lt;10 h), lithium is a more reliable indicator of decompressioninduced growth than changing anorthite content due to lithium’s rapid diffusivity.

Growth of the lava dome and extrusion rates at Soufrière Hills Volcano, Montserrat, West Indies: 2005–2008

The third episode of lava dome growth at Soufrière Hills Volcano began 1 August 2005 and ended 20 April 2007. Volumes of the dome and talus produced were measured using a photo‐based method with a calibrated camera for increased accuracy. The total dense rock equivalent (DRE) volume of extruded andesite magma (306 ± 51 Mm3) was similar within error to that produced in the earlier episodes but the average extrusion rate was 5.6 ± 0.9 m3s−1 (DRE), higher than the previous episodes. Extrusion rates varied in a pulsatory manner from &lt;0.5 m3s−1 to ∼20 m3s−1. On 18 May 2006, the lava dome had reached a volume of 85 Mm3 DRE and it was removed in its entirety during a massive dome collapse on 20 May 2006. Extrusion began again almost immediately and built a dome of 170 Mm3 DRE with a summit height 1047 m above sea level by 4 April 2007. There were few moderate‐sized dome collapses (1–10 Mm3) during this extrusive episode in contrast to the first episode of dome growth in 1995–8 when they were numerous. The first and third episodes of dome growth showed a similar pattern of low (&lt;0.5 m3s−1) but increasing magma flux during the early stages, with steady high flux after extrusion of ∼25 Mm3.

Vulcanian explosion at Soufrière Hills Volcano, Montserrat on March 2004 as revealed by strain data

The CALIPSO collaborative volcano monitoring system on the Caribbean island of Montserrat includes observations of strain at depths ∼200 m using Sacks‐Evertson strainmeters. Strain data for the March 2004 explosion of the Soufrière Hills Volcano are characterized by large, roughly equal but opposite polarity changes at the two near sites and much smaller changes at a more distant site. The strain amplitudes eliminate a spherical pressure (Mogi‐type) source as the sole contributor. The initial changes are followed by smaller recoveries, but with differing relative recovery magnitudes. This dissimilarity requires a minimum of two pressure sources, which we model as a deep spherical pressure source and a shallow dike. The spherical source is fixed at the location derived from data for the massive dome collapse in July 2003. We solve for the best fitting dike plus sphere source combination. The dike geometry is consistent with earlier interpretations of dikes based on GPS data and other lines of evidence.