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The most explosive basaltic scoria cone eruption yet documented (>20 km high plumes) occurred at Sunset Crater (Arizona) ca. 1085 AD by undetermined eruptive mechanisms. We present melt inclusion analysis, including bubble contents by Raman spectroscopy, yielding high total CO 2 (approaching 6000 ppm) and S (~2000 ppm) with moderate H 2 O (~1.25 wt%). Two groups of melt inclusions are evident, classified by bubble vol%. Modeling of post-entrapment modification indicates that the group with larger bubbles formed as a result of heterogeneous entrapment of melt and exsolved CO 2 and provides evidence for an exsolved CO 2 phase at magma storage depths of ~15 km. We argue that this exsolved CO 2 phase played a critical role in driving this explosive eruption, possibly analogous to H 2 O exsolution driving silicic caldera-forming eruptions. Because of their distinct gas compositions relative to silicic magmas (high S and CO 2 ), even modest volume explosive basaltic eruptions could impact the atmosphere. Mechanisms that drive highly explosive eruptions of low-viscosity magmas, such as at Sunset Crater volcano, remain uncertain. Here, the authors present evidence for an exsolved CO 2 phase ~15 km beneath Sunset Crater that was the critical driver of rapid magma ascent leading to the explosive eruption.

Explosive volcanism occurred on Mars during its early history (Noachian–Hesperian; ~4.1–3.0 Ga). Because of Mars’ cold atmospheric temperatures, water released from explosive eruptions may precipitate as ice or ice-ash aggregates. This process may have supplied ice to equatorial regions, which contain high excess hydrogen and potential buried ice deposits. We simulate explosive volcanic eruptions using the Laboratoire de Météorologie Dynamique Generic Planetary Climate Model and find that up to ~5 meters of ice is delivered to the surface in only one high-magnitude eruptive event. This ice can persist for long periods if preserved by widespread cooling from volcanic sulfuric acid or by burial under dust or pyroclasts. Here we show that over time, explosive eruptions may have served as a recurring mechanism for delivering ice to the equator, explaining elevated ice content at low latitudes independent of obliquity. New modeling shows that explosive volcanic eruptions on Mars could have repeatedly delivered ice to the equator, pointing to a volcanic origin for the mysterious excess hydrogen in the planet’s shallow equatorial surface.

Limited evidence surrounds the lived experiences of military spouses whose partner has mental health issues. This lack of evidence may be due to factors such as global austerity, underfunding of armed forces, and inadequate healthcare systems. As a result, family members—especially spouses—often end up being the primary caregivers for their military partners with mental health issues. The study used a qualitative, biographical methodology, collecting data through life stories. Two face-to-face semi-structured interviews took place with nine military spouse recruited through military spouse networks and snowballing. Lieblich et al.’s (1998) framework provided analytical pluralism, which allowed for both narrative and thematic analysis. Stories are presented in the stages ‘in the beginning’, changing times’ and ‘this is me’. Thematic analysis identified six overarching categories; Living with disruption, living in the midst of it all, It isn’t enough, seeking support, Diagnosis and treatment, Living alongside. Whilst the first of its kind in the UK, this biographical study advances both national and global understanding of military spouse experiences in the context of mental health. Both the stories and the categories indicate that living with a serving partner who has mental health issues is a complex journey marked by both struggle and growth. A uniqueness arising from this study highlights the period leading up to a mental health diagnosis, emphasising the prolonged emotional and psychological strain experienced by military spouses before any formal recognition of mental illness in their serving partner. The study adds a new dimension to understanding the emotional toll on military spouses and underscores the importance of early recognition and support. While participants faced emotional detachment and feelings of invisibility, they also identified gains in resilience and strengthened relationships. Through the convergence of the narrative and thematic analysis the participants experience throughout their partners mental health issue is conceptualised in a Relationship Trajectory model. It illustrates the positive, early relational strength, superseded by relationship decline followed with relationship reinvention.

Military healthcare studies have reported a wide range of mental health issues amongst military personnel. Globally, mental health issues are one of the main causes of ill health. Military personnel have a greater prevalence of mental health issues than that of the general population. The impact of mental health issues can be wide and far reaching for family and carers. This systematic narrative review explores the military spouse experience of living alongside their serving or veteran partner with a mental health issue. The systematic review performed was based on the PRISMA guide for searching, screening, selecting papers for data extraction and evaluation. Studies were identified from CINHAL, ASSIA, Proquest Psychology, Proquest Nursing & Allied Health source, Proquest Dissertations & Theses, ETHOS, PsychArticles, Hospital collection, Medline, Science Direct Freedom Collection and hand searching of citations and reference lists. Twenty-seven studies were included in the narrative synthesis. Five overarching themes from the experiences of military spouses' living alongside their serving/veteran partners mental health issue were identified: caregiver burden, intimate relationships, psychological/psychosocial effects on the spouse, mental health service provision and spouse's knowledge and management of symptoms. The systematic review and narrative synthesis identified that the majority of studies focused on spouses of veterans, very few were specific to serving military personnel, but similarities were noted. Findings suggest that care burden and a negative impact on the intimate relationship is evident, therefore highlight a need to support and protect the military spouse and their serving partner. Likewise, there is a need for greater knowledge, access and inclusion of the military spouse, in the care and treatment provision of their serving partner's mental health issue.

The solubility of CO 2 in mafic magmas is strongly dependent on magma composition, which ultimately affects magma storage conditions and eruptive behavior. Recent experimental work showed that previously published volatile solubility models for mafic magmas are not well calibrated at mid-crustal pressures (400–600 MPa). Using a simple thermodynamic model, here we construct a general CO 2 solubility model for mafic magmas by establishing the compositional dependence of two key thermodynamic parameters. The model is calibrated using experimental data from 10 magma compositions that span a range of pressures as well as silica (44–53 wt.%) and total alkali (2–9 wt.%) contents. We also survey the experimental literature for relevant H 2 O solubility data to determine how to model H 2 O solubility for these magmas. We combine these separate CO 2 and H 2 O solubility models into a single general model for mixed-fluid (H 2 O–CO 2 ) solubility in mafic magmas called MafiCH. We test the MafiCH model using experiments from three compositions that fall both within and beyond the calibrated range, and find that the model accurately constrains the CO 2 solubility of depolymerized magmas. Sensitivity tests identify that Na, Ca, and Al have the largest effect on CO 2 solubility while Si and Mg do not play a strong role in CO 2 solubility in mafic, depolymerized melts. Overall, saturation pressures calculated using the new model presented here are typically lower than those predicted by previous models. The model provides a new framework to interpret volcanic data from mafic magma compositions for which no experimental data is available.

Continental flood basalts (CFBs) are dominated by two characteristic lava morphologies. The first type, referred to as ‘compound’ or ‘hummocky pāhoehoe,’ exhibits pillow-like lava flow lobes with cross-sections of ~ 0.5–2 m and thin chilled margins. The second type, referred to as ‘simple’ or ‘sheet lobes’ preserves more massive, inflated flow interiors that are laterally continuous on scales of 100s of meters to kilometers. Previous hypotheses suggest that two factors may contribute to stratigraphic changes in morphology from ‘compound’ to ‘simple’: 1) increased eruption duration or 2) increased extrusion rate. We test the hypothesis that a large increase in extrusion rate would result in flow morphology transitioning from multiple small lobes to inflated sheet lobes due to a shift in flow propagation from intraflow resurfacing-dominated to marginal breakout-dominated. Using polyethylene glycol (PEG) wax extruded into a circular water-filled tank 130 cm in diameter, we produced larger, more complex experiments than previous studies. Our efforts simulated more complex lava fields which change flow morphology with distance from the eruptive vent, characteristic of CFBs. Whereas previous PEG studies linked extrusion rate to near-source surface morphologies, our experiments evaluated how flow propagation mechanisms change with variable extrusion rate and distance from the source. Two flow propagation styles were identified: 1) resurfacing, in which molten material breaks through the surface of a flow and covers the older crust and 2) marginal breakouts, in which molten material extends beyond the crust at the active distal margin of the flow. Flows that propagated via marginal breakouts were found to have lower proportions of resurfaced area and vice versa. We show that significant resurfacing is needed to preserve internal chilled boundaries within a flow and a low-extrusion-rate surface morphology, whereas marginal breakout-dominated flows tend to inflate the pillow-like surface morphology preserving a massive interior at great distances from the vent. Higher and more steady extrusion rates tend to decrease the extent of resurfacing and increase the distance between the source and preserved low-extrusion-rate surface morphologies. We find that an extrusion rate increase equivalent to a jump in the extrusion rate scaling factor, Ψ value, from < 1 to > 5 would be necessary to ensure a switch from resurfacing-dominated lobate morphologies to marginal breakout-dominated propagation style. This amounts to a factor of 125 increase in effusion rate for fissure eruptions and a factor of 625 for point source eruptions, assuming no change in vent geometry. This would be equivalent to an effusion rate of 0.2 m 3 /s, as documented in 1987–1990 Kīlauea eruptions, increasing to 125 m 3 /s, which was commonly measured during the 2014 Holuhraun eruption in Iceland and the 2018 eruption at Leilani Estates in Hawai‘i. Thus, we propose that continental flood basalts do not require unusually large effusion rates, but instead were active for a longer and more consistent time period than smaller-volume eruptions.

Volatile solubility in magmas depends on several factors, including composition and pressure. Mafic magmas with high concentrations of alkali elements are capable of dissolving larger quantities of H2O and CO2 than subalkaline basalt, which possibly contributes to large explosive eruptions. Existing volatile solubility models for alkali-rich mafic magmas are well calibrated below ~ 200 MPa, but at greater pressures the experimental data are sparse. To fill in this gap, we conducted a set of mixed H2O–CO2 volatile solubility experiments between 400 and 600 MPa at 1200 °C in six mafic compositions with variable alkali contents (Stromboli, Etna, Vesuvius, Erebus, Sunset Crater, and the San Francisco Volcanic Field). Results from our experiments indicate that existing volatile solubility models for alkali-rich mafic magmas, if extrapolated beyond their calibrated ranges, do not accurately describe CO2 solubility at mid-crustal pressures. We adapt an existing thermodynamic model to reflect our higher-pressure experimental data by determining model parameters \\[ V_r^0,m\\] (partial molar volume change of CO2 reaction) and K0 (equilibrium constant) for each studied composition. In these compositions, \\[ V_r^0,m\\] is found to vary between ~ 15 and ~ 25 cm3 mol−1, while ln K0 ranges from − 14.9 to − 14.0. The calculated solubility curves show good agreement with CO2 solubility data from the experiments and provide a more accurate description of CO2 solubility than purely empirical fits. These new experiments indicate while CO2 solubility is increased in alkali-rich mafic magmas, it is not simply controlled by total alkali content but rather the full multicomponent magma composition.

Randomised placebo-controlled trials have shown that daily oral pre-exposure prophylaxis (PrEP) with tenofovir–emtricitabine reduces the risk of HIV infection. However, this benefit could be counteracted by risk compensation in users of PrEP. We did the PROUD study to assess this effect. PROUD is an open-label randomised trial done at 13 sexual health clinics in England. We enrolled HIV-negative gay and other men who have sex with men who had had anal intercourse without a condom in the previous 90 days. Participants were randomly assigned (1:1) to receive daily combined tenofovir disoproxil fumarate (245 mg) and emtricitabine (200 mg) either immediately or after a deferral period of 1 year. Randomisation was done via web-based access to a central computer-generated list with variable block sizes (stratified by clinical site). Follow-up was quarterly. The primary outcomes for the pilot phase were time to accrue 500 participants and retention; secondary outcomes included incident HIV infection during the deferral period, safety, adherence, and risk compensation. The trial is registered with ISRCTN (number ISRCTN94465371) and ClinicalTrials.gov (NCT02065986). We enrolled 544 participants (275 in the immediate group, 269 in the deferred group) between Nov 29, 2012, and April 30, 2014. Based on early evidence of effectiveness, the trial steering committee recommended on Oct 13, 2014, that all deferred participants be offered PrEP. Follow-up for HIV incidence was complete for 243 (94%) of 259 patient-years in the immediate group versus 222 (90%) of 245 patient-years in the deferred group. Three HIV infections occurred in the immediate group (1·2/100 person-years) versus 20 in the deferred group (9·0/100 person-years) despite 174 prescriptions of post-exposure prophylaxis in the deferred group (relative reduction 86%, 90% CI 64–96, p=0·0001; absolute difference 7·8/100 person-years, 90% CI 4·3–11·3). 13 men (90% CI 9–23) in a similar population would need access to 1 year of PrEP to avert one HIV infection. We recorded no serious adverse drug reactions; 28 adverse events, most commonly nausea, headache, and arthralgia, resulted in interruption of PrEp. We detected no difference in the occurrence of sexually transmitted infections, including rectal gonorrhoea and chlamydia, between groups, despite a suggestion of risk compensation among some PrEP recipients. In this high incidence population, daily tenofovir–emtricitabine conferred even higher protection against HIV than in placebo-controlled trials, refuting concerns that effectiveness would be less in a real-world setting. There was no evidence of an increase in other sexually transmitted infections. Our findings strongly support the addition of PrEP to the standard of prevention for men who have sex with men at risk of HIV infection. MRC Clinical Trials Unit at UCL, Public Health England, and Gilead Sciences.

The solubility of CO.sub.2 in mafic magmas is strongly dependent on magma composition, which ultimately affects magma storage conditions and eruptive behavior. Recent experimental work showed that previously published volatile solubility models for mafic magmas are not well calibrated at mid-crustal pressures (400-600 MPa). Using a simple thermodynamic model, here we construct a general CO.sub.2 solubility model for mafic magmas by establishing the compositional dependence of two key thermodynamic parameters. The model is calibrated using experimental data from 10 magma compositions that span a range of pressures as well as silica (44-53 wt.%) and total alkali (2-9 wt.%) contents. We also survey the experimental literature for relevant H.sub.2O solubility data to determine how to model H.sub.2O solubility for these magmas. We combine these separate CO.sub.2 and H.sub.2O solubility models into a single general model for mixed-fluid (H.sub.2O-CO.sub.2) solubility in mafic magmas called MafiCH. We test the MafiCH model using experiments from three compositions that fall both within and beyond the calibrated range, and find that the model accurately constrains the CO.sub.2 solubility of depolymerized magmas. Sensitivity tests identify that Na, Ca, and Al have the largest effect on CO.sub.2 solubility while Si and Mg do not play a strong role in CO.sub.2 solubility in mafic, depolymerized melts. Overall, saturation pressures calculated using the new model presented here are typically lower than those predicted by previous models. The model provides a new framework to interpret volcanic data from mafic magma compositions for which no experimental data is available.

During explosive eruptions, airborne particles collide and stick together, accelerating the fallout of volcanic ash and climate-forcing aerosols. This aggregation process remains a major source of uncertainty both in ash dispersal forecasting and interpretation of eruptions from the geological record. Here we illuminate the mechanisms and timescales of particle aggregation from a well-characterized ‘wet’ eruption. The 2009 eruption of Redoubt Volcano, Alaska, incorporated water from the surface (in this case, a glacier), which is a common occurrence during explosive volcanism worldwide. Observations from C-band weather radar, fall deposits and numerical modelling demonstrate that hail-forming processes in the eruption plume triggered aggregation of ∼95% of the fine ash and stripped much of the erupted mass out of the atmosphere within 30 min. Based on these findings, we propose a mechanism of hail-like ash aggregation that contributes to the anomalously rapid fallout of fine ash and occurrence of concentrically layered aggregates in volcanic deposits. The behaviour of airborne fine ash during explosive volcanic eruptions is poorly understood. Here, the authors study hail formation during an eruption, proposing a mechanism of particle aggregation that leads to the fallout of fine ash and the occurrence of concentrically layered aggregates in volcanic deposits