Explosive Episodes Research Articles

Darwin, Hooker and Arruda Furtado and the palaeobotany of Azores: Rediscovering the first collections

The historical investigation of the palaeobotany of the Azores Islands led to the recent rediscovery of the leaf fossils initially collected by Arruda Furtado in the late 19th century. Advised by Sir Charles Darwin and Sir Joseph Dalton Hooker to search for plant fossils, Arruda Furtado found the first specimens in São Miguel Island, and sent them to the UK for further identification. A recent search at the Natural History Museum, UK, revealed that from a total of sixteen specimens, only one specimen survived. In the same tray, two undescribed specimens from Furnas (São Miguel) were found. Here we describe and identify them as Woodwardia radicans, Laurus azorica and an unidentified fern. The taphonomy indicates that these fossils were preserved in a trachytic tuff, possibly related to the explosive episodes of the Furnas volcano, indicating that they could be late Pleistocene to Holocene in age. This report aims to highlight the potential of future palaeobotanical studies of the Azores Islands.

Mechanisms of Local Explosive Development of a Radiation Fog Event

An explosive fog event was analysed which occurred in the coastal area of north- eastern Hebei Province( the Leting meteorological station as representative) and the Tianjin area from 21 to 22 December 2010,based on the observations obtained from the 255 m meteorological tower located in Tianjin,the NCEP reanalysis data with the spacial resolution of 1° × 1°,and the automatic meteorological monitoring data adjacent to the railway. The results indicated that: The explosive fog episode in Leting is the presence of the atmospheric moisture convergence near the shear line,along with the cold air inflow in the front of a short-wave trough,and longwave radiation cooling in the evening. The explosive thickened fog in Tianjin region is directly caused by invasion of a frontal weak cold air of the secondary cold front at lower atmosphere. In addition,the fog dissipation is due to strong cold air which is acompanied with the cold frontal passage. During the fog event,it's moist and clod in near surface layer,warm and dry in the upper boundary layer. In addition,the surface air temperature increases slightly prior to the fog intensification during the overall cooling tendency,which is an effective indicator of the explosive development of fog.

Replenishment of volatile-rich mafic magma into a degassed chamber drives mixing and eruption of Tungurahua volcano

In July and August of 2006 and May of 2010, Tungurahua volcano, Ecuador, produced pyroclastic flow-forming eruptions, representing increased explosivity compared to the Strombolian events that characterized its behavior since its renewal in 1999. Volatiles (H2O, CO2, S, Cl) and major elements were analyzed in 35 melt inclusions hosted in olivine and pyroxene phenocrysts in tephra from both events to reconstruct the pre-eruptive magmatic conditions and mechanisms that led to these more explosive episodes. Melt inclusion composition paired with host phenocryst zonation indicate mixing of two distinct magmas: a volatile-rich (∼4.0 wt% H2O and ∼1,800 ppm S) basaltic andesite containing olivine phenocrysts and a degassed (∼1.0 wt% H2O and 100–500 ppm S) andesite with plagioclase and pyroxene phenocrysts that contain andesitic to dacitic melt inclusions. We attribute the lower volatile concentrations in the evolved melt inclusions to degassing that occurred during residence in a shallow reservoir, where fractional crystallization led to the production of dacitic melt. Our melt inclusion data confirm the hypothesis made on the basis of phenocryst zoning profiles (J Volcanol Geotherm Res 199:69–84, 2011) that the intrusion of a volatile-rich basaltic andesite into a more evolved chamber and subsequent mixing led to explosive eruption in 2006. Melt inclusions from the 2006 and 2010 eruptive products have comparable volatile and major element compositions. High H2O concentrations in melt inclusions from 2010 olivine indicate little diffusive loss from the melt inclusions following mixing with the degassed andesitic reservoir, which requires that the 2010 eruption be the result of a new recharge event and not remobilization of the 2006 hybrid.

Explosive felsic volcanism on El Hierro (Canary Islands)

The Canary Islands consist of seven basaltic shield volcanoes whose submerged portion is much more voluminous than the subaerial part of each island. Like so many other volcanic oceanic islands, the indicative deposits of explosive felsic volcanism are not a common feature on the Canary archipelago. Hitherto, they have only been documented from the central islands of Gran Canaria and Tenerife, which are the largest volcanic complexes of the islands. On the other Canary Islands, the presence of felsic rocks is mostly restricted to intrusions and a few lava flows, generally within the succession in the oldest parts of individual islands. In this paper, we present a detailed stratigraphic, lithological and sedimentological study of a significant felsic pumice deposit on the island of El Hierro, referred here as the Malpaso Member, which represents the only explosive episode of felsic volcanism found on the Canary Islands (outside of Gran Canaria and Tenerife). The products of the eruption indicate a single eruptive event and cover an area of about 15 km2. This work provides a detailed stratigraphic and chronological framework for El Hierro, and four subunits are identified within the member on the basis of lithological and granulometric characteristics. The results of this study demonstrate the importance of an explosive eruption in a setting where the activity is typified by effusive basaltic events. Given the style and the spatial distribution of the Malpaso eruption and its products, a future event with similar characteristics could have a serious impact on the population, infrastructure and economy of the island of El Hierro.

Price Explosiveness, Speculation, and Grain Futures Prices

AbstractA recently developed testing procedure is used to detect and date‐stamp explosive episodes (“bubbles”) in corn, soybean, and wheat futures markets during 2004–2013. We find that the markets experienced price explosiveness only approximately two percent of the time and, when bubbles do occur, they are generally short‐lived and small in magnitude. The correspondence between observed price spikes and bubbles is rather low, with a large portion of the price explosiveness occurring during downward price movements. Commodity index trader positions do not significantly affect the probability of a positive bubble occurring in grain futures markets, which directly contradicts the argument (the “Masters Hypothesis”) that waves of index investment distorted underlying supply‐and‐demand relationships and led to a series of massive bubbles in agricultural futures markets. In addition, commodity index trader positions tend to reduce negative bubble occurrence, while general speculative activity as measured by Working's T reduces the probability of a positive bubble. There is some evidence that the positions of noncommercial traders have a direct effect on positive bubble occurrence, but the effect declines when accounting for the composition of other traders in the market. Overall, speculation has little effect or negative effects on price explosiveness. Finally, positive bubbles are more likely to occur in the presence of low inventories, strong exports, a weak U.S. dollar, and booming economic growth, whereas negative bubbles are more likely to occur with large inventories, weak exports, and stagnant economic growth.

Explosive to effusive transition during the largest volcanic eruption of the 20th century (Novarupta 1912, Alaska)

Silicic volcanic eruptions commonly show abrupt shifts between powerful and dangerous (Plinian) explosive episodes and gentle effusion of lava. Whether the onset of magma permeability and ensuing gas loss controls these transitions has been a subject of debate. We measured porosities and permeabilities in samples from the A.D. 1912 eruption of Novarupta volcano, Alaska, and analyzed them within the context of a well-constrained eruptive sequence that encompasses sustained explosive and effusive activity. For the explosive samples, we find that the degree of vesicle interconnectivity, measured as the ratio of connected to total porosity, decreases with phenocryst content and with increasing eruption intensity. Permeabilities of explosive samples show a weak dependence on porosity. Dome samples are not significantly different in permeability, but are of lower porosity, which together with abundant flattened vesicles is consistent with bubble collapse by permeable outgassing. Quantitative analysis indicates that outgassing alone was insufficient to affect the transition to effusive activity. Rather, the change from explosive to effusive activity was probably a consequence of high versus low magma ascent rates.

Deposition and generation of multiple widespread fall units from the c. AD 1314 Kaharoa rhyolitic eruption, Tarawera, New Zealand

The c. AD 1314 Kaharoa eruption from Tarawera volcano, North Island, New Zealand, was a complex, long-duration, multi-episode rhyolitic event. Up to 13 discrete sub-Plinian to Plinian-style phases occurred in two stages from at least two different vents along an 8-km-long fissure. The early explosive stage produced seven pumice lapilli fall units dispersed solely to the southeast of the volcano, while a later stage produced six fall units dispersed almost entirely to the north and northwest. The duration of fallout for these 13 lapilli units is estimated to have totaled about 1.5 days. The presence of massive-textured ash layers between many of the lapilli fall units suggests that longer-duration, pyroclastic density-current producing phases and more quiescent fallout intervals occurred between the intense explosive phases of the eruption (total duration of ash fallout ~ 7.5 days). The ash deposition extended the minimum duration of the explosive episodes to at least 9 days, based on settling rates of the ash. Possibly the explosive phase of eruptive activity lasted for ~ 2 weeks, including some brief hiatuses and pyroclastic density-current deposition, and was followed by ~ 4 years of mainly lava-dome-forming activity. At least 15 km3 (> 7.3 km3 dense rock equivalent, DRE) of tephra was erupted during the main explosive episodes, and at least 9.1 km3 DRE during the whole eruption, more than doubling the previous estimate. This may be an underestimate by up to 50 % of the fallout volume. Eruption column heights for the two most widely dispersed fall units are estimated to have ranged from 25–28 km above the vents and durations of individual lapilli fall unit-forming phases ranged from 1.5 to 4 h, but the ash-producing phases lasted much longer (individually up to 30 h) and represent a longer-lived shut-down to each eruptive episode. Time-averaged mass discharge rates are estimated to have varied by more than one order of magnitude during the main Plinian-style phases, from 107 to 108 kg/s. However, the explosive phases were unsteady, as indicated by fluctuating grain-size with stratigraphic height in the lapilli fall units and common capping ash beds. The north-northwesterly dispersal of the later stage fall units, and the possible duration of ~ 4 days for these episodes, indicate an unusual period of southerly to southeasterly winds. Therefore, the main explosive part of the Kaharoa eruption is most likely to have occurred during the austral winter to spring months. The Kaharoa eruption style is also shared by the three previous rhyolite-dominated eruptions that have built Tarawera volcano over the past 22,000 years. Knowledge of the widespread pumice and ash fallout from the Kaharoa eruption is important in quantifying the hazard from this type of extended-duration explosive activity, and has implications for future similar rhyolitic activity in New Zealand.

Reconstructing the setting for deposition of distal tephra in the Sea of Japan Basin: A catastrophic eruption of Baitoushan Volcano

This paper presents a detailed analysis of the attitude and accumulation of fine-grain ash material from the Baegdusan-Tomakomai bed (B-Tm) on the seafloor; this material was deposited after a powerful explosion of the ultraplinian type that occurred around 938 AD. It was found that, provided one has a large digital array of grain-size analyses that characterizes both areal and vertical variability in the bed and makes use of advanced mathematical data-processing techniques (division of the grain-size distribution into subpopulations, a trend analysis of transport pathways, and so on), one can derive new information concerning the character of the eruption, its location, the pathways of aerial and marine transport, and the condition of the atmosphere and water at the time of the eruption. It was found that the grain-size distributions for the tephra in the bed in question contain information on two explosive episodes that lasted 10 days each that took place under the conditions of atmospheric circulation typical of spring (the earlier episode) and of autumn (the later episode). For both of these episodes we determined the most likely areas of ash deposition on the marine water surface. We also identified a complex structure of the areas of concentrated particle distribution on the basin bottom that reflected a vortical water structure in the Sea of Japan during the eruption.

Stratigraphic correlation of Holocene phonolitic explosive episodes of the Teide–Pico Viejo Volcanic Complex, Tenerife

Teide and Pico Viejo (TPV) are twin stratovolcanoes that form one of the largest alkaline volcanic complexes in the world. They began forming inside the caldera of Las Cañadas about 200 ka ago and are largely made up of an accumulation of mafic, intermediate and more recent felsic products that form lava flows. However, a significant number of Holocene pyroclastic deposits are also present. To quantify the explosive contribution to the construction of TPV, we re-examined its stratigraphy and identified several Holocene phonolitic explosive episodes ranging from Strombolian to sub-Plinian styles that are represented by fallout and pyroclastic density current deposits. Although some of the pumice deposits have been related to known sources, a few have not been linked to a specific vent. The use of field data as well as geochemical and mineralogical analysis helped to provide reliable criteria for robust correlations and to establish the relative stratigraphy of the deposits. The presence of these pyroclastic deposits in the recent history of the TPV complex suggests that these stratovolcanoes are entering a more explosive stage that represents a non-avoidable hazard for the island of Tenerife.

Volcanic tremors: Good indicators of change in plumbing systems during volcanic eruptions

Geophysical and geochemical signals recorded during episodes of unrest preceding volcanic eruptions provide information on movements of magma inside the lithosphere and on how magma prepares to reach the surface. When the eruption ensues continuous volcanic monitoring can reveal the nature of changes occurring in the volcano's plumbing system, which may be correlated with changes in both eruption behaviour and products. During the 2011–2012 submarine eruption of El Hierro (Canary Islands), the seismic signal, surface deformation, a broad stain on the sea surface of the eruption site, and the occasional appearance of floating lava balloons and pyroclastic fragments were the main observable signs. A strong continuous tremor in the vent accompanied the eruption and varied significantly in amplitude, frequency and dynamical parameters. We analysed these variations and correlated them with changes in the distribution of earthquakes and in the petrology of the erupting magma. This enabled us to relate variations in tremors to changes in the (i) stress conditions of the plumbing system, (ii) dimensions of the conduit and vent, (iii) intensity of the explosive episodes, and (iv) rheological changes in the erupting magma. The results obtained show how the tremor signal was strongly influenced by stress changes in the host rock and in the rheological variations in the erupting magma. We conclude that the tracking of real-time syn-eruptive tremor signals via the observation of variations in plumbing systems and magma physics is a potentially effective tool for interpreting eruption dynamics, and suggest that similar variations observed in pre-eruptive tremors will have a similar origin.

Major effusive eruptions and recent lava fountains: Balance between expected and erupted magma volumes at Etna volcano

AbstractOver the last four decades Etna has shown a high output rate through numerous eruptions. The volcano has displayed two eruptive behaviors. The first is characterized by effusive eruptions that efficiently drained the storage system and emitted large volumes of magma; the second behavior is related to lava fountains, erupting small magma batches, which are normally with high frequency and have been considered as precursors of major effusive eruptions. In this paper, we present an updated estimation of emitted volumes from Etna eruptions, which include the 38 lava fountain episodes that occurred from January 2011 to April 2013. These recent explosive episodes have been frequent, discharging significant magma volumes. Observing the steady trend of magma output over time, we present insights on expected erupted volumes. We highlight that the January 2011 to April 2013 lava fountains efficiently drained the intermediate‐shallow storage system and favored a balance between the incoming and outgoing magma.

Forecasting the duration of volcanic eruptions: an empirical probabilistic model

The ability to forecast future volcanic eruption durations would greatly benefit emergency response planning prior to and during a volcanic crises. This paper introduces a probabilistic model to forecast the duration of future and on-going eruptions. The model fits theoretical distributions to observed duration data and relies on past eruptions being a good indicator of future activity. A dataset of historical Mt. Etna flank eruptions is presented and used to demonstrate the model. The data have been compiled through critical examination of existing literature along with careful consideration of uncertainties on reported eruption start and end dates between the years 1300 AD and 2010. Data following 1600 is considered to be reliable and free of reporting biases. The distribution of eruption duration between the years 1600 and 1669 is found to be statistically different from that following it and the forecasting model is run on two datasets of Mt. Etna flank eruption durations: 1600–2010 and 1670–2010. Each dataset is modelled using a log-logistic distribution with parameter values found by maximum likelihood estimation. Survivor function statistics are applied to the model distributions to forecast (a) the probability of an eruption exceeding a given duration, (b) the probability of an eruption that has already lasted a particular number of days exceeding a given total duration and (c) the duration with a given probability of being exceeded. Results show that excluding the 1600–1670 data has little effect on the forecasting model result, especially where short durations are involved. By assigning the terms ‘likely’ and ‘unlikely’ to probabilities of 66 % or more and 33 % or less, respectively, the forecasting model based on the 1600–2010 dataset indicates that a future flank eruption on Mt. Etna would be likely to exceed 20 days (± 7 days) but unlikely to exceed 86 days (± 29 days). This approach can easily be adapted for use on other highly active, well-documented volcanoes or for different duration data such as the duration of explosive episodes or the duration of repose periods between eruptions.

The 2006–2009 activity of the Ubinas volcano (Peru): Petrology of the 2006 eruptive products and insights into genesis of andesite magmas, magma recharge and plumbing system

Following a fumarolic episode that started six months earlier, the most recent eruptive activity of the Ubinas volcano (south Peru) began on 27 March 2006, intensified between April and October 2006 and slowly declined until December 2009. The chronology of the explosive episode and the extent and composition of the erupted material are documented with an emphasis on ballistic ejecta. A petrological study of the juvenile products allows us to infer the magmatic processes related to the 2006–2009 eruptions of the andesitic Ubinas volcano. The juvenile magma erupted during the 2006 activity shows a homogeneous bulk-rock andesitic composition (56.7–57.6wt.% SiO2), which belongs to a medium- to high-K calc-alkaline series. The mineral assemblage of the ballistic blocks and tephra consists of plagioclase>two-pyroxenes>Fe–Ti oxide and rare olivine and amphibole set in a groundmass of the same minerals with a dacitic composition (66–67wt.% SiO2). Thermo-barometric data, based on two-pyroxene and amphibole stability, records a magma temperature of 998±14°C and a pressure of 476±36MPa. Widespread mineralogical and textural features point to a disequilibrium process in the erupted andesite magma. These features include inversely zoned “sieve textures” in plagioclase, inversely zoned clinopyroxene, and olivine crystals with reaction and thin overgrowth rims. They indicate that the pre-eruptive magmatic processes were dominated by recharge of a hotter mafic magma into a shallow reservoir, where magma mingling occurred and triggered the eruption. Prior to 2006, a probable recharge of a mafic magma produced strong convection and partial homogenization in the reservoir, as well as a pressure increase and higher magma ascent rate after four years of fumarolic activity. Mafic magmas do not prevail in the Ubinas pre-historical lavas and tephras. However, mafic andesites have been erupted during historical times (e.g. AD 1667 and 2006–2009 vulcanian eruptions). Hence, the most recent episode indicates that a resupply of mafic magmas has probably occurred at depth under Ubinas.

FOSSIL IMPRINT OF A POWERFUL FLARE AT THE GALACTIC CENTER ALONG THE MAGELLANIC STREAM

The Fermi satellite discovery of the gamma-ray emitting bubbles extending 50 deg (10 kpc) from the Galactic Centre has revitalized earlier claims that our Galaxy has undergone an explosive episode in the recent past. We now explore a new constraint on such activity. The Magellanic Stream is a clumpy gaseous structure passing over the South Galactic Pole (SGP) at a distance of at least 50-100 kpc. Patchy H-alpha emission discovered along the Magellanic Stream over the SGP is a factor of 5 too bright to have been produced by the Galactic stellar population. Time-dependent models of Stream clouds exposed to a flare in ionising photon flux show that the ionised gas must recombine and cool for a time interval 0.6 - 2.9 Myr for the emitted H-alpha surface brightness to drop to the observed level. A nuclear starburst is ruled out. Sgr A* is a more likely candidate because it is two orders of magnitude more efficient at converting gas to UV radiation. The central black hole (4 x 10^6 Msun) can supply the required ionising luminosity with a fraction of the Eddington accretion rate (3-30%). In support of nuclear activity, the H-alpha emission along the Stream has a polar angle dependence peaking close to the SGP. Moreover, it is now generally accepted that the Stream over the SGP must be further than the Magellanic Clouds. At the lower halo gas densities, shocks become too ineffective and are unlikely to give rise to a polar angle dependence in the H-alpha emission. Thus it is likely that the Stream emission arose from a `Seyfert flare' that was active 1-3 Myr ago, consistent with the cosmic ray lifetime in the Fermi bubbles. Sgr A* activity today is greatly suppressed (70-80 dB) relative to the Seyfert outburst...

Bubbles in food commodity markets: Four decades of evidence

We use daily prices from individual futures contracts to test whether speculative bubbles exist in 12 agricultural markets and to identify whether patterns of bubble behavior exist over time. The samples begin as far back as 1970 and run through 2011. The findings demonstrate that all 12 agricultural markets experienced multiple periods of price explosiveness. However, bubble episodes represent a very small portion—between 1.5 and 2%—of price behavior during the 42-year period. In addition, most bubbles are short-lived with 80–90% lasting fewer than 10 days. Though receiving far less attention, negative bubbles contribute significantly to price behavior, accounting for more than one-third of explosive episodes. Markets over-react during both positive and negative explosive episodes, leading to a correction as they return to a random walk. This adjustment back to fundamental values is most pronounced with positive bubbles particularly in the earlier part of the sample. While the magnitudes of the corrections are generally small, there were a few instances of significant increases in prices and large over-reactions, most notably in the softs (e.g., cocoa 1973, coffee 1994, cotton 2010). We also find that explosive periods did not become more common or last longer in the second half of the sample period and that the most recent bubble episodes may not have been as severe as in mid-1970s.

Analysis of the seismic activity associated with the 2010 eruption of Merapi Volcano, Java

The 2010 eruption of Merapi is the first large explosive eruption of the volcano that has been instrumentally observed. The main characteristics of the seismic activity during the pre-eruptive period and the crisis are presented and interpreted in this paper. The first seismic precursors were a series of four shallow swarms during the period between 12 and 4months before the eruption. These swarms are interpreted as the result of perturbations of the hydrothermal system by increasing heat flow. Shorter-term and more continuous precursory seismic activity started about 6weeks before the initial explosion on 26 October 2010. During this period, the rate of seismicity increased almost constantly yielding a cumulative seismic energy release for volcano-tectonic (VT) and multiphase events (MP) of 7.5×1010J. This value is 3 times the maximum energy release preceding previous effusive eruptions of Merapi. The high level reached and the accelerated behavior of both the deformation of the summit and the seismic activity are distinct features of the 2010 eruption.The hypocenters of VT events in 2010 occur in two clusters at of 2.5 to 5km and less than 1.5km depths below the summit. An aseismic zone was detected at 1.5–2.5km depth, consistent with studies of previous eruptions, and indicating that this is a robust feature of Merapi's subsurface structure. Our analysis suggests that the aseismic zone is a poorly consolidated layer of altered material within the volcano. Deep VT events occurred mainly before 17 October 2010; subsequent to that time shallow activity strongly increased. The deep seismic activity is interpreted as associated with the enlargement of a narrow conduit by an unusually large volume of rapidly ascending magma. The shallow seismicity is interpreted as recording the final magma ascent and the rupture of a summit-dome plug, which triggered the eruption on 26 October 2010.Hindsight forecasting of the occurrence time of the eruption is performed by applying the Material Failure Forecast Method (FFM) using cumulative Real-time Seismic Amplitude (RSAM) calculated both from raw records and on signals classified according to their dominant frequency. Stable estimates of eruption time with errors as small as ±4h are obtained within a 6day lapse time before the eruption. This approach could therefore be useful to support decision making in the case of future large explosive episodes at Merapi.

The pre-eruption conditions for explosive eruptions at Merapi volcano as revealed by crystal texture and mineralogy

We analyze the textures and mineralogy of Merapi tephra generated during explosive VEI 3–4 eruptions over the past 2000years, and compare these data with those observed for Merapi dome and flow lavas. We find that the Merapi pumiceous tephra and lava textures differ significantly with respect to small-size crystal populations, but that phenocryst textures are generally similar. A similar initial phase of crystallization is indicated for tephras and lavas in mid-crustal (>10km depth) reservoirs. Subsequent textural differences are mainly affected by ascent rate and degassing during ascent, and, for dome lavas, with temporary storage in shallower reservoirs. These differences also correspond to different eruptive styles. Our analyses include study of pumices, lava, and breadcrust-bomb samples, including samples from some of the most recent explosive episodes prior to the 2010 eruption. Textural analyses of youthful breadcrust bomb samples yield insights on one type of transition between effusive and explosive eruptive styles, involving pressure build-up under a degassed crystalline shallow-conduit plug. In general, comparison of the crystal size distributions and calculated residence times among the effusive and explosive eruptive styles suggests that the two main magma-product types resided for similar lengths of time in a mid-crustal reservoir, before ascending toward the surface and either erupting explosively (tephra), or stagnating in a shallow magma chamber prior to extrusion (lava). The interpretation is supported by the occurrences of amphibole in pristine condition in tephra and in altered state in lava. Finally the 1872 and 2010 explosive eruptions are examined and compared with others over the past three millennia. The 2010 bulk-rock compositions overlap with products of other major explosive Merapi eruptions, such as the Ngrangkah, Tegalsruni, Temusari, and Kepuharjo tephras. The 2010 products show a gradational late-stage mafic enrichment, dissimilar to 1872 which showed little (<1%) compositional variation, but similar to the Ngrangkah, Tegalsruni, and Temusari tephras. Such variation implies conventional withdrawal from a zoned magma chamber, with the more-evolved products being erupted first.

Trioctahedral micas in xenolithic ejecta from recent volcanism of the Somma-Vesuvius (Italy): Crystal chemistry and genetic inferences

This study reports the first crystal chemical database resulting from a detailed structural investigation of trioctahedral micas found in xenolithic ejecta produced during the AD 1631, 1872 and 1944 eruptions, three explosive episodes of recent volcanic period of Vesuvius volcano (Southern Italy). Three xenolith types were selected: metamorphic/metasomatic skarns, pyrometamorphic/hydrothermally altered nodules and mafic cumulates. They are related to different magma chemistry and effusive styles: from sub-plinian and most evolved (AD 1631 eruption) to violent strombolian with medium evolution degree (AD 1872 eruption) to vulcanian-effusive, least evolved (AD 1944 eruption) event, respectively. Both xenoliths and micas were investigated employing multiple techniques: the xenoliths were characterized by X-ray fluorescence, inductively-coupled plasma-mass spectrometry, optical microscopy, X-ray powder diffraction, and quantitative energy-dispersive microanalysis; the micas were studied by electron probe microanalysis and single crystal X-ray diffraction. The mica-bearing xenoliths show variable texture and mineralogical assemblage, clearly related to their different origin. Based on the major oxide chemistry, only one xenolithic sample falls in the skarn compositional field from the Somma-Vesuvius literature, some fall close to the skarns and cumulate fields, others plot close to the syenite/foidolite/essexite field. A subgroup of the selected ejecta does not fall or approach any of the compositional fields. Trace and rare earth element patterns show some petrological affinity between studied xenoliths and erupted magmas with typical Eu, Ta and Nb negative anomalies. Strongly depleted patterns were detected for the 1631 metamorphic/metasomatic skarns xenoliths. Three distinct mica groups were distinguished: 1) Mg-, Al-rich, low Ti-bearing, low to moderate F-bearing varieties (1631 xenolith), 2) Al-moderate, F- and Mg-rich, Ti-, Fe-poor varieties (1872 xenolith), and 3) Al-, Ti- and Fe-rich, F-poor phases (1944 xenolith). All the analyzed mica crystals are 1M polytypes with the expected space group C2/m. Micas from xenoliths of the 1631 Vesuvius eruption are phlogopites characterized by a combination of low extent of oxy-type and variable extent OH−→F− substitutions, as testified by the range of F concentration (from ~0.20 to 0.80apfu). Micas from xenoliths of the 1872 Vesuvius eruption exhibit structural peculiarities typical of fluorophlogopites, i.e. OH−→F− substitution is predominant. Micas from the xenolith of the 1944 Vesuvius eruption display features typical of oxy-substituted micas. The variability of the crystal chemical features of the studied micas is consistent with the remarkable variation of their host rocks. Micas from 1631 nodules are related to metasomatic, skarn-type environment, deriving from the metamorphosed wall-rocks hosting the magma reservoir. The fluorophlogopites from the 1872 xenoliths testify for strongly dehydrated environmental conditions compared to those of the 1631 and 1944 hosts. Finally, magma storage condition at depth, associated to a decreasing aH2O may have promoted major oxy-type substitutions in 1944 biotites.

Injuries from combat explosions in Iraq: Injury type, location, and severity

IntroductionExplosions have caused a greater percentage of injuries in Iraq and Afghanistan than in any other large-scale conflict. Improvements in body armour and field medical care have improved survival and changed the injury profile of service personnel. This study's objective was to determine the nature, body region, and severity of injuries caused by an explosion episode in male service personnel. Materials and methodsA descriptive analysis was conducted of 4623 combat explosion episodes in Iraq between March 2004 and December 2007. The Barell matrix was used to describe the nature and body regions of injuries due to a combat explosion. ResultsA total of 17,637 International Classification of Diseases, Ninth Revision (ICD-9) codes were assigned to the 4623 explosion episodes, with an average of 3.8 ICD-9 codes per episode. The most frequent single injury type was a mild traumatic brain injury (TBI; 10.8%). Other frequent injuries were open wounds in the lower extremity (8.8%) and open wounds of the face (8.2%), which includes tympanic membrane rupture. The extremities were the body regions most often injured (41.3%), followed by head and neck (37.4%) and torso (8.8%). ConclusionThe results of this study support previous observations of TBI as a pre-eminent injury of the wars in Iraq and Afghanistan, with mild TBI as the most common single injury in this large cohort of explosion episodes. The extremities had the highest frequency of injuries for any one body region. The majority of the explosion episodes resulted in more than one injury, and the variety of injuries across nearly every body region and injury type suggests a complex nature of explosion injuries. Understanding the constellation of injuries commonly caused by explosions will assist in the mitigation, treatment, and rehabilitation of the effects of these injuries.

Fish‐meal diet enriched with omega‐3 PUFA and treatment of canine chronic enteropathies

AbstractWatching to see whether their pet has another explosive episode of bloody diarrhea, and the detailed characteristics of those episodes, must be every pet‐owner's nightmare. Until now, the standard method of differentiating the two most common forms of chronic enteropathy in dogs, inflammatory bowel disease (IBD) and food‐responsive diarrhea, has been to watch their response to various treatments, including an elimination diet. The manuscript by Ontsouka et al. in this issue of the European Journal of Lipid Science and Technology [p. 412–422], is of particular interest for several reasons. Firstly, it relates changes in duodenal gene expression profiles to a longer term reduction in diarrhea. This is important not only in providing a mechanism for this effect, but also implying a potential biomarker that might predict a reduction in the symptoms of chronic enteropathies, without having to wait for the disease process to occur. This thereby adds to a growing literature base endorsing genomic technologies in supporting health claims for pet foods. In addition, the study gives credibility to a fish‐meal‐ and potato protein‐based diet, enriched in omega‐3 PUFA, in reducing the symptoms of spontaneous diarrhea lasting at least 6 wk. Consequent opportunities and challenges, for pets, other animals and humans, are discussed in the present commentary.See accompanying article http://dx.doi.org/10.1002/ejlt.201100343