3-D analysis and interpretation of magnetotelluric data from the Aluto-Langano geothermal field, Ethiopia

The Main Ethiopian Rift Valley encompasses a number of volcanoes, which are known to be actively deforming with reoccurring periods of uplift and setting. One of the regions where temporal changes take place is the Aluto volcanic complex. It hosts a productive geothermal field and the only currently operating geothermal power plant of Ethiopia. We carried out magnetotelluric (MT) measurements in early 2012 in order to identify the source of unrest. Broad-band MT data (0.001-1000s) have been acquired at 46 sites covering the expanse of the Aluto volcanic complex with an average site spacing of 1km. Based on this MT data it is possible to map the bulk electrical resistivity of the subsurface down to depths of several kilometres. Resistivity is a crucial geophysical parameter in geothermal exploration as hydrothermal and magmatic reservoirs are typically related to low resistive zones, which can be easily sensed by MT. Thus by mapping the electrical conductivity one can identify and analyse geothermal systems with respect to their temperature, extent and potential for production of energy. 3-D inversions of the observed MT data from Aluto reveal the typical electrical conductivity distribution of a high-enthalpy geothermal system, which is mainly governed by the hydrothermal alteration mineralogy. The recovered 3-D conductivity models provide no evidence for an active deep magmatic system under Aluto. Forward modelling of the tippers rather suggest that occurrence of melt is predominantly at lower crustal depths along an off-axis fault zone a few tens of kilometres west of the central rift axis. The absence of an active magmatic system implies that the deforming source is most likely situated within the shallow hydrothermal system of the Aluto-Langano geothermal fiel

Geomorphology and age constraints of seamounts in the Cabo Verde Archipelago, and their relationship to island ages and geodynamic evolution

The Cabo Verde Archipelago is related to a mantle plume located close to the rotational pole of the African Plate. It consists of islands and seamounts arranged in a horseshoe‐shaped pattern open to the west, thus forming two volcanic chains, each with a weak east‐west age progression. High‐resolution swath bathymetry of 12 Cabo Verde seamounts is used here to assign each seamount to its pre‐shield, shield or post‐shield evolutionary stage, respectively. The eastern seamounts exhibit degraded and partially eroded morphologies, and are mainly in their post‐shield stage. A new 40Ar‐39Ar date for Senghor Seamount at 14.872 ± 0.027 Ma supports old ages for the eastern seamounts. The western seamounts generally exhibit younger volcanic‐edifice‐construction morphologies, showing fresh effusive and explosive volcanics, including rarely observed deep‐water explosive volcanism in the Charles Darwin Volcanic Field. Furthermore, the two previously unknown seamounts Sodade and Tavares in the westernmost termini of both volcanic chains exhibit pristine volcanic morphologies, in agreement with present‐day volcanism and seismic activity recorded from the western seamounts. The islands and seamounts rest on three submarine platforms to the east, northwest and southwest, respectively. Taken together, the seamount and island data suggest a shift in igneous activity from the eastern to the other platforms at about 8–6 Ma. However, the complex evolution pattern for both volcanic chains includes the simultaneous occurrence of pre‐shield or shield edifices at any time, followed by erosional and rejuvenation stages. The new seamount data still demonstrate ongoing westward submarine‐growth in both volcanic chains

Magma plumbing systems: a geophysical perspective

Over the last few decades, significant advances in using geophysical techniques to image the structure of magma plumbing systems have enabled the identification of zones of melt accumulation, crystal mush development, and magma migration. Combining advanced geophysical observations with petrological and geochemical data has arguably revolutionised our understanding of, and afforded exciting new insights into, the development of entire magma plumbing systems. However, divisions between the scales and physical settings over which these geophysical, petrological, and geochemical methods are applied still remain. To characterise some of these differences and promote the benefits of further integration between these methodologies, we provide a review of geophysical techniques and discuss how they can be utilised to provide a structural context for and place physical limits on the chemical evolution of magma plumbing systems. For example, we examine how Interferometric Synthetic Aperture Radar (InSAR), coupled with Global Positioning System (GPS) and Global Navigation Satellite System (GNSS) data, and seismicity may be used to track magma migration in near real-time. We also discuss how seismic imaging, gravimetry and electromagnetic data can identify contemporary melt zones, magma reservoirs and/or crystal mushes. These techniques complement seismic reflection data and rock magnetic analyses that delimit the structure and emplacement of ancient magma plumbing systems. For each of these techniques, with the addition of full-waveform inversion (FWI), the use of Unmanned Aerial Vehicles (UAVs) and the integration of geophysics with numerical modelling, we discuss potential future directions. We show that approaching problems concerning magma plumbing systems from an integrated petrological, geochemical, and geophysical perspective will undoubtedly yield important scientific advances, providing exciting future opportunities for the volcanological community

Marijuana and illicit drugs: Correlates of condomless anal sex among adolescent and emerging adult sexual minority men

•Knowledge of drug use and sexual behaviors among young sexual minority men is limited.•Marijuana was associated with the occurrence of condomless anal sex.•Illicit drugs were associated with occurrence and frequency of condomless anal sex. The association between “illicit drugs” (e.g., cocaine/crack, methamphetamine, gamma-hydroxybutyrate-GHB, ketamine, and ecstasy) and condomless anal sex (CAS) with casual partners is well established for sexual minority men (SMM). Recent evidence from adult SMM has indicated that marijuana is associated with the occurrence of CAS with casual partners above and beyond illicit drug use. The purpose of the current study was to evaluate associations between CAS and the use of marijuana and illicit drugs in a sample of young SMM (aged 15–24). Participants (n = 578) completed an online survey assessing demographics, current PrEP prescription, age, marijuana use, as well as drug use and sexual behavior in the past 90 days. A hurdle model simultaneously predicted the occurrence of CAS as well as the frequency of CAS among those reporting it. Illicit drug use was associated with both the occurrence (OR = 2.26; p = .01) and frequency of CAS (RR = 1.63; p = .02). In contrast, marijuana use was associated with the occurrence (OR = 1.69; p = .01), but not the frequency of CAS (RR = 1.07; p = .74). Findings mirror recent observations in large samples of adult SMM. While the effect size of marijuana is more modest than illicit drug use, marijuana does have significant and unique associations with the occurrence of CAS. HIV prevention services for young SMM may therefore benefit from assessing and addressing marijuana use in the context of HIV sexual behavior

Coping with global uncertainty: Perceptions of COVID-19 psychological distress, relationship quality, and dyadic coping for romantic partners across 27 countries

A correction has been published: Erratum to Coping with global uncertainty: Perceptions of COVID-19 psychological distress, relationship ... available at: https://journals.sagepub.com/doi/full/10.1177/02654075211061907American Psychological Association’s Office of International Affair