Eruption Of Mount Research Articles

Bayesian inversion of data from effusive volcanic eruptions using physics‐based models: Application to Mount St. Helens 2004–2008

Physics‐based models of volcanic eruptions can directly link magmatic processes with diverse, time‐varying geophysical observations, and when used in an inverse procedure make it possible to bring all available information to bear on estimating properties of the volcanic system. We develop a technique for inverting geodetic, extrusive flux, and other types of data using a physics‐based model of an effusive silicic volcanic eruption to estimate the geometry, pressure, depth, and volatile content of a magma chamber, and properties of the conduit linking the chamber to the surface. A Bayesian inverse formulation makes it possible to easily incorporate independent information into the inversion, such as petrologic estimates of melt water content, and yields probabilistic estimates for model parameters and other properties of the volcano. Probability distributions are sampled using a Markov‐Chain Monte Carlo algorithm. We apply the technique using GPS and extrusion data from the 2004–2008 eruption of Mount St. Helens. In contrast to more traditional inversions such as those involving geodetic data alone in combination with kinematic forward models, this technique is able to provide constraint on properties of the magma, including its volatile content, and on the absolute volume and pressure of the magma chamber. Results suggest a large chamber of >40 km3 with a centroid depth of 11–18 km and a dissolved water content at the top of the chamber of 2.6–4.9 wt%.

A Constellation of Vital Phenomena

60 worldliteraturetoday.org reviews Sex proves vital as resource and relief. Fatima reappears in “Bayern Bayern,” bedding Jonah, a Nigerian Irishman. For her, past is not culture but body: “The mind forgets things easily, but my whole goddamn body remembers my lovers.” In her memory , Jonah and Aziz “grow together into something else.” Meanwhile, the young protagonist of “War Currency ” trades sex for a failed chance to flee Bosnia. Youth reveres age in tropes from Bosnian rural culture. In “Gusul,” Emina, who cares for the autistic Swedish boy, Stig, makes plum pie in the old way to please her dying mother , while in “Butter,” Adam churns fresh milk into putar for his beloved wheelchair-bound grandmother. That tenderness secures him a cherished position as caretaker for an elderly Swede (the job Mahmutović held while earning his PhD in English literature in Sweden), their close bond traced in “Vacation: A Travelogue.” The penultimate story, “What We Talk about When We Talk about Suicide,” features a chat room whose personae discuss Stig’s successful suicide. When Almasa sadly reports that she urged him to seek counseling , her strong but caring voice hints that, once “embalmed for three years,” she is now firmly rooted in new soil. Finally, in “Afterword: Homecoming,” the Mahmutović-like persona of the opening piece relates his trip “home” to Bosnia with his wife and two small boys, where he rediscovers the “excessive Bosnian swearing,” finds himself “curseless,” “a language Puritan,” and realizes at last, “my home was, if anything , my strangeness.” In sometimes earthy, sometimes lyrical English, his third language, Mahmutović here presents a compelling gallery of mostly rural Bosnians who face traumatic circumstances with grit, transcending their pasts to find footholds in the present, most often by embracing others. Michele Levy North Carolina A&T University Anthony Marra. A Constellation of Vital Phenomena. New York. Hogarth. 2013. isbn 9780770436407 After reading A Constellation of Vital Phenomena, I can only echo the amazement of other reviewers: that such an accomplished novel is Anthony Marra’s first and that he visited Chechnya, the setting, only after he had all but completed it. The places, the topography, the course of the wars—the remembered first occupation and the second occupation by the Russians within the ten-year span of the novel, 1994 to 2004—all this context was largely created from determined research. The novel begins and ends in the middle. During Chechnya’s rebellion against Russian occupation, a girl’s father is whisked away by soldiers, presumably to be shot, and the eightyear -old is taken by a neighbor to a hospital, where he bargains with the head surgeon to help as a medical orderly in exchange for her taking in the girl. These three characters are narrated forward for five days in 2004, interspersed with backstories that connect them, even while pointing to their uncertain futures. Their conflicts are quite natural : the surgeon, a Russian national whose family had been settled in Chechnya, recognizes that the neighbor , who had been functioning as the village doctor, is at best semicompetent , though a good artist. The child, however appealing, poses a danger both to the surgeon and the neighbor (and his bedridden wife), since she is wanted by the Russians, in keeping with their policy of complete family extermination of rebels or sympathizers as a warning to others. Eugene Eoyang The Promise and Premise of Creativity Continuum Subtitled “Why Comparative Literature Matters,” this volume from an esteemed literary scholar makes the case for reading and studying literature at a critical moment. Through case studies and well-reasoned arguments, Eoyang upholds literature as cultural communication and outlines “the uses of the useless.” He tackles an important subject with enthusiasm and demonstrates his own heartfelt affection for comparative literature. Suzanne Dracius Climb to the Sky Jamie Davis, tr. University of Virginia Press In this collection of eight stories and one novella, Suzanne Dracius places women in opposition to overwhelming historical and existential circumstances. Her protagonists face the varied traumas of the Caribbean twentieth century—from the eruption of Mount Pelée to the boredom of bourgeois living—and must learn to overcome. Jamie Davis is an experienced translator of Dracius’s prose. Nota Bene...

Five Movements in Praise

Eugene Eoyang The Promise and Premise of Creativity Continuum Subtitled “Why Comparative Literature Matters,” this volume from an esteemed literary scholar makes the case for reading and studying literature at a critical moment. Through case studies and well-reasoned arguments, Eoyang upholds literature as cultural communication and outlines “the uses of the useless.” He tackles an important subject with enthusiasm and demonstrates his own heartfelt affection for comparative literature. Suzanne Dracius Climb to the Sky Jamie Davis, tr. University of Virginia Press In this collection of eight stories and one novella, Suzanne Dracius places women in opposition to overwhelming historical and existential circumstances. Her protagonists face the varied traumas of the Caribbean twentieth century—from the eruption of Mount Pelée to the boredom of bourgeois living—and must learn to overcome. Jamie Davis is an experienced translator of Dracius’s prose. Nota Bene The ten-year range of markers begins each chapter, with the focal year for the chapter in boldface. This aid is quite helpful in a novel that alternates between the present and the past, chapter by chapter. Centering on the characters’ stories and their attempts to cope with an unstable political/military situation , Marra keeps the style straightforward and informative. The texture of their experience comes primarily from character interchanges, in which people who are, in a sense, always under siege manage to keep their spirits up as well as their dedication to humane values, even when they don’t realize it. Their hard-bitten exchanges are often surprisingly funny and sometimes even tender. The secondary characters are quite strong, even memorable: an old man who burns his life’s work, a history of Chechnya; his son, whose torture by the Russians turns him into an informer; the surgeon’s sister, who is made an addict and sex slave, but comes back to paint a mural and work in the hospital —and then disappears again. Some readers may be disappointed that political history is slighted, that there is not more on the religious fervor of the Chechen rebels. But the novel reminds us that such wars entangle many who are not impelled to fight and want nothing more than a return to something approaching normalcy. Marra’s constellation of characters , revealed from inside through changes in point of view, show us “life,” which is, after all, the word defined by the title, according to a Russian medical dictionary. These people will stay with you. W. M. Hagen Oklahoma Baptist University Sharmistha Mohanty. Five Movements in Praise. Mumbai. Almost Island. 2013. isbn 9788192129518 In three books published over a period of eighteen years, Sharmistha Mohanty has been showing, with increasing consistency and verve, that there is more to contemporary creative writing in India than the marketable mix of magic realism, hip journalism, and re-creative nonfiction revered by most publishers and media outlets. There is poetry, of course, of which Mohanty is a perceptive publisher; but there are also rare instances of literary fiction and creative nonfiction whose models are to be found outside the mainstream of the Anglo-American novelistic and short-story tradition, in the wilder woods of continental Europe’s and Latin American’s para- and metafictional practices. While building on the foundations painstakingly laid in Book One (1995) and New Life (2005), Five Movements in Praise pursues a more ambitious course, moving beyond the internal waters of confessional, coming-of-age narrative, and aiming at the open sea of experimental literature. Using a musical metaphor as a compositional scheme and the travelogue form (and the traveler persona, or personae) as a narrative decoy, Mohanty successfully overcomes the autobiographical impulse and the limitations of the first-person narrative that had characterized her previous works. Although each of the five movements is set in actual places (Khuldabad and the Valley of Saints, the Ajanta and Ellora caves, Villa Schönberg and the Rietberg September–October 2013 • 61 62 worldliteraturetoday.org reviews Museum in Zurich), the boundaries between real and imagined spaces, interior and exterior (or fabricated and fabulated) landscapes—in brief, between topos and logos—are often blurred, if not erased, and their correspondences and liminal ambiguities are consistently cross-referenced throughout the book. Similarly...

Faulting within the Mount St. Helens conduit and implications for volcanic earthquakes

The 2004–2008 eruption of Mount St. Helens produced seven dacite spines mantled by cataclastic fault rocks, comprising an outer fault core and an inner damage zone. These fault rocks provide remarkable insights into the mechanical processes that accompany extrusion of degassed magma, insights that are useful in forecasting dome-forming eruptions. The outermost part of the fault core consists of finely comminuted fault gouge that is host to 1- to 3-mm-thick layers of extremely fine-grained slickenside-bearing ultracataclasite. Interior to the fault core, there is an ∼2-m-thick damage zone composed of cataclastic breccia and sheared dacite, and interior to the damage zone, there is massive to flow-banded dacite lava of the spine interior. Structures and microtextures indicate entirely brittle deformation, including rock breakage, tensional dilation, shearing, grain flow, and microfaulting, as well as gas and fluid migration through intergranular pores and fractures in the damage zone. Slickenside lineations and consistent orientations of Riedel shears indicate upward shear of the extruding spines against adjacent conduit wall rocks. Paleomagnetic directions, demagnetization paths, oxide mineralogy, and petrology indicate that cataclasis took place within dacite in a solidified steeply dipping volcanic conduit at temperatures above 500 °C. Low water content of matrix glass is consistent with brittle behavior at these relatively high temperatures, and the presence of tridymite indicates solidification depths of More than a million small and low-frequency "drumbeat" earthquakes with coda magnitudes (M d ) 2 ) slip patches, possibly along observed extensive principal shear zones within the fault core but probably not along the smaller Riedel shears. Although our field and structural data are compatible with stick-slip models, they do not rule out seismic and infrasound models that call on resonance of steam-filled fractures to generate the drumbeat earthquakes. We suggest that stick-slip and gas release processes may be coupled, and that regardless of the source mechanism, the distinctive drumbeat earthquakes are proving to be an effective precursor for dome-forming eruptions. Our data document a continuous cycle of deformation along the conduit margins beginning with episodes of fracture in the damage zone and followed by transfer of motion to the fault core. We illustrate the cycle of deformation using a hypothetical cross section of the Mount St. Helens conduit, extending from the surface to the depth of magmatic solidification.

PANDANGAN GABRIEL MARCEL TENTANG MANUSIA DALAM KONTEKS PERISTIWA BENCANA ALAM

In this time, there are a lot of accidents, like flood, landslide, fire, dryness, storm, tsunami, earthquake, and mount eruption. A lot of victims in these disasters. The victim have never represented an object choice, even victim have never chosen. Social reality describing to live together that demand a good social relationship and interaction of intersubjectivity. The Gabriel Marcel’s concept is the most relevant concept. The problems are what is the nature of “I” according to Marcel? How about the concept of relation of intersubjectivity? What is the concept of Love and Hope? What relevancy the Gabriel Marcel’s concept with human and emphaty with the victim of disaster? The Result of research are: According to Marcel’s view of existence of human being cannot be objectivied. The existence is my real experience as a subject in the world. In other word, existence represents the complexity of all factors that signs my live. Because of Marcel’concept gave appreciation for relation, he sure that man is the dynamic creature, always be achieve the level of to be. This level require to be confessed because to become to be myself, somebody will depend on its relationship. Intersubjective relationship according to Marcel marked with attendance. The mystery of human being is on this relationship. Attendance represents the meeting I – Thou, not only be comprehended simply as a meeting someone in the space. Attendance realized with the love, and faithfulness. These unsure are the important elements in understand and feel disaster victim, not as an object felt pity. Expectation will penetrate the certainty, which can make the calm human being and not afraid to death, also for the disaster. Expectation will appear the belief. Despair becaused of losing the expectation, belief, and love. These elements will realize the awareness to the eternity love, inclusive of God. Love represents the philosophic key on Marcel’concept which find the balance solution. Love gives the meaning of intersubjective relationship. With Love, the object will never died. Love gives the eternity meaning, to remove the hate each other, like expectation when removing the fear, despair. The contrary, expectation gives someone the confidence, certainty to uncertainty. Love and expectation confirm the self- faithfulness to the others inclusive of God.

TOF-SIMS and electron microprobe investigations of zoned magmatic orthopyroxenes: First results of trace and minor element analysis with implications for diffusion modeling

Zoned phenocrysts in volcanic rocks potentially provide an archive of magmatic processes. As a crystal grows and comes into contact with different melt batches, the chemical and textural signature of this journey is recorded within its crystal lattice. The timescale of some magmatic processes can be investigated through the relaxation of chemical gradients across crystal growth zones through the application of diffusion modeling techniques. One of the current limitations to diffusion modeling is the spatial and analytical resolution of the chemical profile that conventional techniques such as electron probe microanalyzer (EPMA), dynamic secondary ion mass spectrometry (SIMS), and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) can achieve. Here, for the first time, we present time-of-flight (TOF) SIMS (TOF-SIMS) data for zoning of orthopyroxene crystals from the May 1982 eruption of Mount St. Helens volcano, U.S.A., and cross-calibrate these data between backscattered electron images and EPMA. TOF-SIMS has the advantage of being able to achieve micrometer to nanoscale spatial resolution of major elements as well as analyses of light elements, such as Li, and trace and minor elements (Na, K, and Ni) at concentrations that cannot be achieved by EPMA, provided that convolution (overlap) effects and polyatomic mass inferences are carefully considered. With TOF-SIMS analyses we identified zoning of Li on a spatial scale (ca. 5-10 μm) that would be inaccessible to most other conventional analytical techniques. Preliminary results indicate that Li, a fast-diffusing element, may be introduced to the crystals in the minutes, hours, or days prior to eruption and may provide insights into pre-eruptive magmatic processes. Thus, TOF-SIMS has the potential to be a powerful tool for obtaining minor and trace element profiles across compositional interfaces within crystals at high-spatial resolution.

Extreme frictional processes in the volcanic conduit of Mount St. Helens (USA) during the 2004–2008 eruption

The 2004–2008 eruption of Mount St. Helens saw the extrusion of seven high-viscosity spines and formation of discrete shear zones along the conduit margin. At spine 7 this shear zone consists of four structurally distinct layers: the outer surface gouge (L1) crosscuts; a dark, banded layer (L2) which grades into; a moderately sheared layer (L3) and; undeformed rock (L4) inside the spine. Field observations, porosity measurements, geochemistry, mineralogy, microstructure, crystal size- and shape-distribution, kinetic properties and magnetic analyses chart the evolution of deformation processes and products throughout the eruption.Gouge formation was concomitant with characteristic microseismic “drumbeats” at depths 0.5–1 km. In addition, the seismic record shows two larger earthquakes with similar seismic signatures in August 2006, which we conclude represent larger slip amounts along the conduit margin of spine 7. Extensive slip resulted in frictional heating on the order of several hundreds of degrees, melting the highly-viscous, crystalline, ascending magma plug and forming a pseudotachylyte. High ambient temperatures in the conduit resulted in near-equilibrium melting and slow recrystallisation, thus impeding the development of signature pseudotachylyte characteristics and hindering identification. Thus, frictional melting and recrystallisation in ascending magma plugs may be a common, but unidentified, phenomena at composite volcanoes worldwide.

Rapid, low-cost photogrammetry to monitor volcanic eruptions: an example from Mount St. Helens, Washington, USA

We describe a low-cost application of digital photogrammetry using commercially available photogrammetric software and oblique photographs taken with an off-the-shelf digital camera to create sequential digital elevation models (DEMs) of a lava dome that grew during the 2004–2008 eruption of Mount St. Helens (MSH) volcano. Renewed activity at MSH provided an opportunity to devise and test this method, because it could be validated against other observations of this well-monitored volcano. The datasets consist of oblique aerial photographs (snapshots) taken from a helicopter using a digital single-lens reflex camera. Twelve sets of overlapping digital images of the dome taken during 2004–2007 were used to produce DEMs and to calculate lava dome volumes and extrusion rates. Analyses of the digital images were carried out using photogrammetric software to produce three-dimensional coordinates of points identified in multiple photos. The evolving morphology of the dome was modeled by comparing successive DEMs. Results were validated by comparison to volume measurements derived from traditional vertical photogrammetric surveys by the US Geological Survey Cascades Volcano Observatory. Our technique was significantly less expensive and required less time than traditional vertical photogrammetric techniques; yet, it consistently yielded volume estimates within 5% of the traditional method. This technique provides an inexpensive, rapid assessment tool for tracking lava dome growth or other topographic changes at restless volcanoes.

Long-range volcanic ash transport and fallout during the 2008 eruption of Chaitén volcano, Chile

The May 2008 eruption of Chaitén volcano, Chile, provided a rare opportunity to measure the long-range transport of volcanic emissions and characteristics of a widely-dispersed terrestrial ash deposit. Airborne ash mass, quantified using thermal infrared satellite remote sensing, ranged between 0.2 and 0.4Tg during the period 3–7 May 2008. A high level of spatiotemporal correspondence was observed between cloud trajectories and changes in surface reflectivity, which was inferred to indicate ash deposition. The evolution of the deposit was mapped for the first time using satellite-based observations of surface reflectivity.The distal (>80km) ash deposit was poorly sorted and fine grained, and mean particle size varied very little beyond a distance >300km. There were three particle size subpopulations in fallout at distances >300km which mirror those identified in fallout from the 18 May 1980 eruption of Mount St. Helens, known to have a high propensity for aggregation. Discrete temporal sampling and characterisation of fallout demonstrated contributions from specific eruptive phases. Samples collected at the time of deposition were compared to bulk samples collected months after deposition and provided some evidence for winnowing.Experimentally-derived ash leachates had near-neutral pH values and charge balance which indicates minimal quantities of adsorbed acids. X-ray Photoelectron Spectroscopy (XPS) analyses revealed surface enrichments in Ca, Na and Fe and the presence of coatings of mixed Ca-, Na- and Fe-rich salts on ash particles prior to deposition. Low S:Cl ratios in leachates indicate that the eruption had a low S content, and high Cl:F ratios imply gas–ash interaction within a Cl-rich environment. We estimate that ash fallout had potential to scavenge ∼42% of total S released into the atmosphere prior to deposition. XPS analyses also revealed ash particle surfaces were strongly enriched in Fe (in contrast to the results from bulk leachate analyses), which suggests that Chaitén ash fallout over oceans had potential to influence productivity in high-nutrient, low-chlorophyl regions of the oceans. Therefore ash particle surface geochemical analysis should be applied to quantify Fe-modulated biologically-forced CO2 draw-down potential of volcanic ash fallout over oceans.

Implications of management strategies and vegetation change in the Mount St. Helens blast zone

The 1980 eruptions of Mount St. Helens provided an excellent opportunity for scientists to investigate the recovery of vegetation communities following a major geologic disturbance. An important and often overlooked aspect in these studies is the human factor in recovery processes, and specifically, the different management approaches taken towards re-establishment of vegetation on lands under the control of various owners. This study examines vegetation changes throughout the 1980 blast zone using a time series of Landsat-derived Normalized Difference Vegetation Index (NDVI) images and change detection methods to assess the changes over 25 years, from 1980 to 2005, as a function of human management combined with ecological factors. This long-term tracking of change indicates that differences in the speed of vegetation re-establishment and consequent rates of change substantially reflect human involvement and varying management strategies.

Physics-based models of ground deformation and extrusion rate at effusively erupting volcanoes

[1] We present a model of effusive silicic volcanic eruptions which relates magma chamber and conduit physics to time-dependent data sets, including ground deformation and extrusion rate. The model involves a deflating chamber which supplies Newtonian magma through a cylindrical conduit. Solidification is approximated as occurring at fixed depth, producing a solid plug that slips along its margins with rate-dependent friction. Changes in tractions acting on the chamber and conduit walls are used to compute surface deformations. Given appropriate material properties and initial conditions, the model predicts the full evolution of an eruption, allowing us to examine the dependence of observables on initial chamber volume, overpressure, and volatile content. Employing multiple data sets in combination with a physics-based model allows for better constraints on these parameters than is possible using kinematic idealizations. Modeling posteruptive deformation provides an improved constraint on the rate of influx into the magma chamber from deeper sources. We compare numerical results to analytical approximations and to data from the 2004–2008 eruption of Mount St. Helens. For nominal parameters the balance between magma chamber pressure and frictional resistance of the solid plug controls the evolution of the eruption, with little contribution from the fluid magma below the idealized crystallization depth. While rate-dependent plug friction influences the time-dependent evolution of the eruption, it has no control on the final chamber pressure or extruded volume.

Evolution of the mechanics of the 2004–2008 Mt. St. Helens lava dome with time and temperature

The 2004–2008 eruption of Mount St. Helens, Washington, USA, formed a typical example of a Pelean spiny lava dome, with solid spines of crystalline silicic lava extruded along shear zones bounded by fault gouge (Cashman et al., 2008; Iverson et al., 2006). Creation of and movement along shear zones in this erupting lava, recorded as shallow micro-earthquakes, were thus key controls on eruption style and rate, in addition to dome stability. As eruption style and lava dome stability often change within individual eruptions, it is important to identify how the strength of dome rocks changes with temperature, time, texture and extrusion rate. However, critical values of the shear strength of dome lava at eruptive temperatures have never been measured. We have found in controlled laboratory experiments simulating eruption conditions that dome lava strength increased during the course of the 2004–2008 eruption of Mount St. Helens, as the textures became more crystalline and less porous. Increasing lava strength during the eruption would lead to deformation becoming increasingly localised to shear zones, explaining why the extrusion style and centre were so consistent. Acoustic emissions and microstructure analysis indicate that fracturing was more localised at higher temperatures, resulting in higher strengths at eruptive temperature compared to ambient temperatures for later erupted samples. The strength of these later erupted samples at eruptive temperatures increased markedly with strain rate. This would damp any increases in effusion rate that may result from changes in magma pressure, explaining the steady effusion rate at Mount St. Helens from 2004 to 2008.

(A35) Building National and Community Resilience

Each year a report is prepared for the World Economic Forum on global risks. It outlines the issues most likely to impact on society, and makes recommendations on actions required. The 2010 report concludes that global risks are becoming more volatile, uncertain, complex and ambiguous; and it comments on the increased number of high-impact, hard to predict ‘black swan’ events over the past decade. Indeed, recent disasters such as the Haiti earthquake which killed over 250,000 people, the eruption of Mount Eyjafjallajökull in Iceland, the rapid onset of the 2008/09 global financial crisis, and terrorist attacks around the world have all contributed to a heightened awareness of personal risk and vulnerability. In less than a decade the term resilience has evolved from the disciplines of materials science and environmental studies to become a concept used enthusiastically by policy makers, practitioners and academics. The concept is attractive as it suggests an ability of something or someone to cope in the face of adversity – to recover and return to normality after confronting an abnormal, alarming and often unexpected threat. It is used alongside security to understand how governments, local authorities, the emergency services and health agencies can best address the threats from natural disasters, health pandemics, malicious attacks on a country's critical infrastructure, and other major disruptive events. The paper discusses the meaning and utility of the concept of resilience. It traces the origins of the term through to its current use in addressing contemporary threats facing individuals, communities, organisations and nations. It identifies and describes a number of characteristics which are common to the concept of resilience in its many contexts and manifestations. In conclusion, the paper supports a review of the language and thinking of emergency and disaster management, and promotes the emerging concept of disaster resilience.

Subevents of long‐period seismicity: Implications for hydrothermal dynamics during the 2004–2008 eruption of Mount St. Helens

One of the most striking aspects of seismicity during the 2004–2008 eruption of Mount St. Helens (MSH) was the precise regularity in occurrence of repetitive long‐period (LP) or “drumbeat” events over sustained time periods. However, this precise regularity was not always observed, and at times the temporal occurrence of LP events became more random. In addition, accompanying the dominant LP class of events during the 2004–2008 MSH eruption, there was a near‐continuous, randomly occurring series of smaller seismic events. These subevents are not always simply small‐amplitude versions of the dominant LP class of events but appear instead to result from a separate random process only loosely coupled to the main LP source mechanism. We present an analysis of the interevent time and amplitude distributions of the subevents, using waveform cross correlation to separate LP events from the subevents. We also discuss seismic tremor that accompanied the 8 March 2005 phreatic explosion event at MSH. This tremor consists of a rapid succession of LPs and subevents triggered during the explosion, in addition to broadband noise from the sustained degassing. Immediately afterward, seismicity returned to the pre‐explosion occurrence pattern. This triggering in relation to the rapid ejection of steam from the system, and subsequent return to pre‐explosion seismicity, suggests that both seismic event types originated in a region of the subsurface hydrothermal system that was (1) in contact with the reservoir feeding the 8 March 2005 phreatic explosion but (2) not destroyed or drained by the explosion event. Finally, we discuss possible thermodynamic conditions in a pressurized hydrothermal crack that could give rise to seismicity. Pressure drop estimates for typical LP events are not generally large enough to perturb pure water in a shallow hydrothermal crack into an unstable state. However, dissolved volatiles such as CO2 may lead to a more unstable system, increasing the seismogenic potential of a hydrothermal crack subject to rapid heat flux. The interaction of hydrothermal and magmatic systems beneath MSH in 2004–2008 thus appears able to explain a wide range of observed phenomena, including subevents, LP events, larger (Md > 2) events, and phreatic explosions.

Cyclic ground tilt associated with the 2004–2008 eruption of Mount St. Helens

The long‐term behavior of the 2004–2008 effusive eruption of Mount St. Helens was characterized by a gradual decline in the rates of seismicity, dome growth, and broad‐scale ground deformation, but shallow near‐periodic “drumbeat” earthquakes over timescales of minutes indicated episodic short‐term behavior. In part to better characterize this behavior and any associated ground deformation, a network of tiltmeters was installed and recorded thousands of cyclic tilt events within the crater. The duration of these events, from minutes to hours, was too long for them to be directly caused by the drumbeat seismicity. Tilt events were characterized by a recoverable, asymmetric pattern of rapid tilt away from the vent followed by a more gradual reversal, were highly correlated between different tiltmeters in the crater, sometimes occurred in association with volcanic seismicity, and ceased at the end of the eruption. Tilt vectors converged on a point just south of the center of the preexisting 1980s lava dome, and the absence of detectable tilt outside the crater suggests a shallow source (<1 km). We examine several models, including cycles of conduit pressurization and plug slip or gas loss and stick‐slip behavior on the interface between the ascending plug and the 1980s lava dome. The small number of stations within the crater prevents a unique determination of source type or geometry, but results are consistent with a mechanism involving extrusion of the semisolid dacite plug and/or cycles of conduit pressurization.

Volcanic hazard in a slave society: the 1812 eruption of Mount Soufrière in St Vincent

This study analyses the impact of Mount Soufrière’s 1812 eruption on St Vincent: a British West India colony with an economy based on plantation slavery. Output losses are estimated at 14% of island GDP and infrastructure damage at 7% of physical capital invested in sugar estates. In contrast, casualty rates during the eruption and its aftermath proved minimal. Losses were concentrated in two northern coastal regions lying closest to the volcano: firstly, long-established plantations and estates on the Leeward side; secondly, recently-established estates on the Windward side. Leeward cultivators recovered only three-quarters of their pre-disaster output level during the 5 years after 1812. In contrast, Windward producers nearly doubled their output. The role of public authorities in disaster response was confined to securing emergency food relief from overseas and collating loss estimates for use in securing imperial assistance from Britain. Parliamentary grants and loans aided Windward planters in their reconstruction efforts, leading to a rise in slave numbers inhabiting the most hazardous zone. Contemporary descriptions of 1812 portray events as a calamity which no human effort could avert. This depiction, while effective lobby material and an inspiration to artist J.M.W. Turner, exaggerates the extent of destruction, downplays the role of human agency, and obscures the connections between colonisation and the conceptualisation of events as a disaster.

Influence of pre-eruptive degassing and crystallization on the juvenile products of laterally directed volcanic explosions

Strikingly similar examples of edifice collapse and directed blast are the 18 May 1980 eruption of Mount St. Helens (MSH), Washington, USA, and the 30 March 1956 eruption of Bezymianny Volcano (BZ), Kamchatka, Russia. In these cases, flank failures led to near-instantaneous decompression and fragmentation of intra-edifice cryptodome magma, which produced catastrophic, laterally directed blasts. In both instances, the blast products consisted of juvenile material with bimodal density/vesicularity distributions: low- and high-density modes at 1900 and 2400 kg m − 3 for BZ, 1600 and 2300 kg m − 3 for MSH, although the proportion of high-density material is greater at BZ. Blast materials also exhibit striking variety in groundmass crystallinity (< 40 to > 90 vol.%) despite having fairly uniform pheno-crystallinities, suggesting that degassing-driven groundmass crystallization occurred to varying extents within cryptodome magma at both volcanoes. New bulk-rock H 2O and ∂D measurements confirm that progressive open-system outgassing occurred prior to both blasts. The correlations between crystallinity, clast density, and bulk H 2O contents suggest that syn-blast magma expansion was modulated both by non-uniform volatile distribution within the cryptodome and rheological controls associated with non-uniform crystal content. Spatial heterogeneities in volatiles and crystallinity within a given cryptodome are attributed to distance from the wallrock margin, which probably correlates with timing of magma injection. The greater proportion of high-density material at BZ is speculatively related to lower blast energy compared with MSH.

Temporal changes in stress preceding the 2004–2008 eruption of Mount St. Helens, Washington

The 2004–2008 eruption of Mount St. Helens (MSH), Washington, was preceded by a swarm of shallow volcano-tectonic earthquakes (VTs) that began on September 23, 2004. We calculated locations and fault-plane solutions (FPS) for shallow VTs recorded during a background period (January 1999 to July 2004) and during the early vent-clearing phase (September 23 to 29, 2004) of the 2004–2008 eruption. FPS show normal and strike-slip faulting during the background period and on September 23; strike-slip and reverse faulting on September 24; and a mixture of strike-slip, reverse, and normal faulting on September 25–29. The orientation of σ 1 beneath MSH, as estimated from stress tensor inversions, was found to be sub-horizontal for all periods and oriented NE–SW during the background period, NW–SE on September 24, and NE–SW on September 25–29. We suggest that the ephemeral ~ 90° change in σ 1 orientation was due to intrusion and inflation of a NE–SW-oriented dike in the shallow crust prior to the eruption onset.

A 250 k.y. record of Cascade arc pyroclastic volcanism from late Pleistocene lacustrine sediments near Summer Lake, Oregon, USA

Distal tephra beds provide important records of pyroclastic volcanism that enhance our overall understanding of eruptive frequencies, magnitudes, compositions, and hazards. Some beds also serve as widespread chronostratigraphic markers. Lacustrine sediments near Summer Lake, Oregon (United States), record numerous eruptions of Cascade arc sources over a period exceeding 2.5 m.y. Late Pleistocene sediments exposed in outcrop have yielded 88 visible tephra beds, including many beds not previously documented. Of these beds, 44 are characterized by rhyolitic glass, 40 contain predominantly basaltic or intermediate glass, and 4 are strongly heterogeneous in composition. Only 23 have been correlated to deposits outside of the Summer Lake basin. The remaining 65 beds provide a record of Cascade arc volcanism that is as yet unique to Summer Lake. Age-depth relations are well constrained for the upper 6 m of section, but are less certain in the lower 12.4 m. Tephra correlations and an overall age model suggest the following: bed B1 originates from an eruption of Mount Mazama (Crater Lake) ca. 20 ka. Beds I and W likely originate from eruptions of Mount St. Helens ca. 80 and 190 ka. A 7-cm-thick tephra bed correlated to Shevlin Park Tuff probably dates to ca. 198 ka. Tephra correlated to the Antelope Well tuff from Medicine Lake volcano dates to ca. 215 ka. Bed NN, at the base of the section, has an estimated age of at least 240–250 ka and probably originated from Newberry Volcano. Overall, this record significantly refines the Pleistocene tephrostratigraphic framework for western North America.

Mount St. Helens: A 30‐Year Legacy of Volcanism

The spectacular eruption of Mount St. Helens on 18 May 1980 electrified scientists and the public. Photodocumentation of the colossal landslide, directed blast, and ensuing eruption column—which reached as high as 25 kilometers in altitude and lasted for nearly 9 hours—made news worldwide. Reconnaissance of the devastation spurred efforts to understand the power and awe of those moments (Figure 1).The eruption remains a seminal historical event—studying it and its aftermath revolutionized the way scientists approach the field of volcanology. Not only was the eruption spectacular, but also it occurred in daytime, at an accessible volcano, in a country with the resources to transform disaster into scientific opportunity, amid a transformation in digital technology. Lives lost and the impact of the eruption on people and infrastructure downstream and downwind made it imperative for scientists to investigate events and work with communities to lessen losses from future eruptions.