Thoughts on the criteria to determine the origin of volcanic unrest as magmatic or non-magmatic.

As our ability to detect volcanic unrest improves, we are increasingly confronted with the question of whether the unrest has a magmatic origin (magma on the move) or a non-magmatic origin from a change in the hydrothermal system (fluids that are not magma on the move) or tectonic processes. The cause of unrest has critical implications for the potential eruptive hazard (e.g. used in constructing Bayesian Event Trees), but is frequently the subject of debate, even at well-studied systems. Here, we propose a set of multi-disciplinary observations and numerical models that could be used to evaluate conceptual models about the cause of unrest. These include measurements of gas fluxes and compositions and the isotopic signature of some components (e.g. H2, He, C, SO2, H2 O, CH4 and CO2), the spatial and temporal characteristics of ground deformation, thermal output, seismicity, changes in gravity, and whether there is topographic uplift or subsidence spanning hundreds to thousands of years. In several volcanic systems, both magmatic and non-magmatic unrest is occurring at the same time. While none of these observations or models is diagnostic on its own, we illustrate several examples where they have been used together to make a plausible conceptual model of one or more episodes of unrest and whether eruptions did or did not follow the unrest. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'.

An examination of the relation of gender, mass media influence, and loneliness to disordered eating among college students.

Previous research has found that mass media influence and loneliness relate to disordered eating behaviors in women, but little is known about this relation in men. The present study examined the relations among disordered eating patterns, gender, mass media influence, and loneliness in male and female college students. Results of a stepwise regression revealed that disordered eating attitudes and behaviors (as measured by the Eating Attitudes Test-26) were predicted by mass media influence, gender, and loneliness, respectively. In the present study both male and female college students appear susceptible to developing disordered eating patterns. Clinicians may wish to address unrealistic comparisons to media and client interpersonal skills when designing treatment plans.

Factors associated with alcohol use in later adolescence.

The relative influence of a number of family and individual characteristics on the frequency and intensity of alcohol use in a group of older adolescents was assessed. The sample consisted of 8,661 persons ranging in age from 20 to 21 years obtained from the "High School and Beyond" study. Logistic regression analyses performed on both frequency and intensity of alcohol use indicated that white males from higher socioeconomic backgrounds, living in urban or suburban areas and having an external locus of control and a weak family orientation, tended to drink more frequently and consume a larger quantity of alcohol per drinking episode. Results are explained from a sociocultural perspective.

Factors associated with adolescent saving and spending patterns.

This study examined the saving and spending behaviors of 1,619 employed high school seniors from over 1,000 private and public schools across the United States. Students were categorized as savers, necessity spenders, and discretionary spenders based on their responses to the question, "How do you spend the money that you earn?" Associations of student spending and saving patterns with individual and family factors were analyzed. Student savers were from families who saved and planned money use. Students who spent more for necessities were from families with fewer resources and greater financial difficulties. Discretionary spenders felt that money was important and were from families with higher income and socioeconomic status. Findings are discussed in light of the importance of families as socializing agents of their children.

Adolescent body mass indices and self-perception.

This study examined the relationship between body mass index (BMI) of adolescents and their perceived-weight status and self-concept, controlling for confounding factors. The data base was drawn from the High School and Beyond (HSB) study, which included 17,318 females and 15,878 males. BMI was calculated using self-reported weights and heights. Response variables included a self-concept index and evaluation of the statement "I am overweight." While respondents' perception of overweight status was accompanied by higher mean BMI values, there were discrepancies in perceived-weight and BMI-weight status. Logistic regression of explanatory variables on perception of overweight status revealed that BMI was the strongest predictor, gender was the second strongest, and the odds of perception of overweight status were higher for females than males by a factor of more than eight. Ordinary least squares regression of explanatory variables on the self-concept index revealed that perception of normal weight status, lower BMI, and male gender were strong predictors of positive self-concept. The findings indicate that substantial numbers of teenage females perceive themselves as overweight when BMI values suggest they are not, while males have a reasonably accurate weight perception.

Global link between deformation and volcanic eruption quantified by satellite imagery.

A key challenge for volcanological science and hazard management is that few of the world's volcanoes are effectively monitored. Satellite imagery covers volcanoes globally throughout their eruptive cycles, independent of ground-based monitoring, providing a multidecadal archive suitable for probabilistic analysis linking deformation with eruption. Here we show that, of the 198 volcanoes systematically observed for the past 18 years, 54 deformed, of which 25 also erupted. For assessing eruption potential, this high proportion of deforming volcanoes that also erupted (46%), together with the proportion of non-deforming volcanoes that did not erupt (94%), jointly represent indicators with 'strong' evidential worth. Using a larger catalogue of 540 volcanoes observed for 3 years, we demonstrate how this eruption-deformation relationship is influenced by tectonic, petrological and volcanic factors. Satellite technology is rapidly evolving and routine monitoring of the deformation status of all volcanoes from space is anticipated, meaning probabilistic approaches will increasingly inform hazard decisions and strategic development.

Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano, Chile.

Unconsolidated pyroclastic flow deposits of the 1993 eruption of Lascar Volcano, Chile, have, with time, become increasingly dissected by a network of deeply penetrating fractures. The fracture network comprises orthogonal sets of decimeter-wide linear voids that form a pseudo-polygonal grid visible on the deposit surface. In this work, we combine shallow surface geophysical imaging tools with remote sensing observations and direct field measurements of the deposit to investigate these fractures and their underlying causal mechanisms. Based on ground penetrating radar images, the fractures are observed to have propagated to depths of up to 10 m. In addition, orbiting radar interferometry shows that deposit subsidence of up to 1 cm/year-1 occurred between 1993 and 1996 with continued subsidence occurring at a slower rate thereafter. In situ measurements show that 1 m below the surface, the 1993 deposits remain 5°C to 15°C hotter, 18 years after emplacement, than adjacent deposits. Based on the observed subsidence as well as estimated cooling rates, the fractures are inferred to be the combined result of deaeration, thermal contraction, and sedimentary compaction in the months to years following deposition. Significant environmental factors, including regional earthquakes in 1995 and 2007, accelerated settling at punctuated moments in time. The spatially variable fracture pattern relates to surface slope and lithofacies variations as well as substrate lithology. Similar fractures have been reported in other ignimbrites but are generally exposed only in cross section and are often attributed to formation by external forces. Here we suggest that such interpretations should be invoked with caution, and deformation including post-emplacement subsidence and fracturing of loosely packed ash-rich deposits in the months to years post-emplacement is a process inherent in the settling of pyroclastic material.

Factors associated with alcohol use in young adulthood.

The purpose of the study was to identify characteristics associated with higher levels of alcohol use in individuals who are between 24 and 25 years of age. Data from the 1982 and 1986 U.S. High School and Beyond longitudinal study (n = 8,875) were used to examine the relationship between the response variables, frequency, and intensity of alcohol use in 1986, and the explanatory variables which included alcohol use in 1982. Comparison of alcohol use in the two time periods revealed an increase in the percentage of respondents who consumed high levels of alcohol, while abstention from drinking remained relatively constant. Frequency of alcohol use in 1986 was related to use in 1982, gender, ethnicity, and family orientation.