A review of solar type Ⅲ radio bursts

Solar type Ⅲ radio bursts are an important diagnostic tool in the understanding of solar accelerated electron beams. They are a signature of propagating beams of nonthermal electrons in the solar atmosphere and the solar system. Consequently, they provide information on electron acceleration and transport, and the conditions of the background ambient plasma they travel through. We review the observational properties of type Ⅲ bursts with an emphasis on recent results and how each property can help identify attributes of electron beams and the ambient background plasma. We also review some of the theoretical aspects of type Ⅲ radio bursts and cover a number of numerical efforts that simulate electron beam transport through the solar corona and the heliosphere.     

The impact of climate change on tribal communities in the US: displacement, relocation, and human rights

Tribal communities in the United States, particularly in coastal areas, are being forced to relocate due to accelerated rates of sea level rise, land erosion, and/or permafrost thaw brought on by climate change. Forced relocation and inadequate governance mechanisms and budgets to address climate change and support adaptation strategies may cause loss of community and culture, health impacts, and economic decline, further exacerbating tribal impoverishment and injustice. Sovereign tribal communities around the US, however, are using creative strategies to counter these losses. Taking a human rights approach, this article looks at communities’ advocacy efforts and strategies in dealing with climate change, displacement, and relocation. Case studies of Coastal Alaska and Louisiana are included to consider how communities are shaping their own relocation efforts in line with their cultural practices and values. The article concludes with recommendations on steps for moving forward toward community-led and government-supported resettlement programs.     

Laboratory simulation of salt weathering under moderate ageing conditions: Implications for the deterioration of sandstone heritage in temperate climates

Salt weathering is a significant process affecting the deterioration and conservation of stone-built heritage in many locations and environments. While much research has focused on the impact of salt weathering under arid or coastal conditions with characteristic climatic conditions and salt types, many sites found to be experiencing salt-induced deterioration, such as sandstone rock-hewn cave temples in Gansu Province, China and sandstone buildings in the northern UK, experience high humidities, moderate temperature ranges, and different salt types. To evaluate the impact of salt weathering on sandstone-built heritage under such mild humid environmental conditions, a lab simulation experiment was designed. The experiment was carried out on three types of sandstone (used in the northern UK and Gansu Province, China) and utilized a realistic diurnal humidity and temperature cycle (85% RH/16°C + 60% RH/22°C), and three widespread damaging salts, that is, Na₂SO₄, MgSO₄, and the mixture of Na₂SO₄–MgSO₄. The nature and extent of deterioration was monitored by photography, weight loss, and the changes in petrophysical properties measured using hardness, ultrasonic pulse velocity (P-wave velocity), water absorption coefficient by capillarity, open porosity, and apparent density. All three sandstones were found to be susceptible to MgSO₄ and the mixture of Na₂SO₄–MgSO₄, but weakly affected by Na₂SO₄ under mild humid environmental conditions.     

The flow dynamics of an extremely large volume pyroclastic flow,the 2.08-Ma Cerro Galán Ignimbrite,NW Argentina,and comparison with other flow types

The 2.08-Ma Cerro Galán Ignimbrite (CGI) represents a >630-km³ dense rock equivalent (VEI 8) eruption from the long-lived Cerro Galán magma system (∼6 Ma). It is a crystal-rich (35–60%), pumice (<10% generally) and lithic-poor (<5% generally) rhyodacitic ignimbrite, lacking a preceding plinian fallout deposit. The CGI is preserved up to 80 km from the structural margins of the caldera, but almost certainly was deposited up to 100 km from the caldera in some places. Only one emplacement unit is preserved in proximal to medial settings and in most distal settings, suggesting constant flow conditions, but where the pyroclastic flow moved into a palaeotopography of substantial valleys and ridges, it interacted with valley walls, resulting in flow instabilities that generated multiple depositional units, often separated by pyroclastic surge deposits. The CGI preserves a widespread sub-horizontal fabric, defined by aligned elongate pumice and lithic clasts, and minerals (e.g. biotite). A sub-horizontal anisotropy of magnetic susceptibility fabric is defined by minute magnetic minerals in all localities where it has been analysed. The CGI is poor in both vent-derived (‘accessory’) lithics and locally derived lithics from the ground surface (‘accidental’) lithics. Locally derived lithics are small (<20 cm) and were not transported far from source points. All data suggest that the pyroclastic flow system producing the CGI was characterised throughout by high sedimentation rates, resulting from high particle concentration and suppressed turbulence at the depositional boundary layer, despite being a low aspect ratio ignimbrite. Based on these features, we question whether high velocity and momentum are necessary to account for extensive flow mobility. It is proposed that the CGI was deposited by a pyroclastic flow system that developed a substantial, high particle concentration granular under-flow, which flowed with suppressed turbulence. High particle concentration and fine-ash content hindered gas loss and maintained flow mobility. In order to explain the contemporaneous maintenance of high particle concentration, high sedimentation rate at the depositional boundary layer and a high level of mobility, it is also proposed that the flow(s) was continuously supplied at a high mass feeding rate. It is also proposed that internal gas pressure within the flow, directed downwards onto the substrate over which the flow was passing, reduced the friction between the flow and the substrate and also enhanced its mobility. The pervasive sub-horizontal fabric of aligned pumice, lithic and even biotite crystals indicates a consistent horizontal shear force existed during transport and deposition in the basal granular flow, consistent with the existence of a laminar, shearing, granular flow regime during the final stages of transport and deposition.     

Heterogeneous pumice populations in the 2.08-Ma Cerro Gal��n Ignimbrite: implications for magma recharge and ascent preceding a large-volume silicic eruption

Triggering mechanisms of large silicic eruptions remain a critical unsolved problem. We address this question for the ~2.08-Ma caldera-forming eruption of Cerro Galán volcano, Argentina, which produced distinct pumice populations of two colors: grey (5%) and white (95%) that we believe may hold clues to the onset of eruptive activity. We demonstrate that the color variations correspond to both textural and compositional variations between the clast types. Both pumice types have bulk compositions of high-K, high-silica dacite to low-silica rhyolite, but there are sufficient compositional differences (e.g., ~150?ppm lower Ba at equivalent SiO₂ content and 0.03?wt.% higher TiO₂ in white pumice than grey) to suggest that the two pumice populations are not related by simple fractionation. Trace element concentrations in crystals mimic bulk variations between clast types, with grey pumice containing elevated Ba, Cu, Pb, and Zn concentrations in both bulk samples (average Cu, Pb, and Zn concentrations are 27, 35, and 82 in grey pumice vs. 11, 19, and 60 in white pumice) and biotite phenocrysts and white pumice showing elevated Li concentrations in biotite and plagioclase phenocrysts. White and grey clasts are also texturally distinct: White pumice clasts contain abundant phenocrysts (44?C57%), lack microlites, and have highly evolved groundmass glass compositions (76.4?C79.6?wt.% SiO₂), whereas grey pumice clasts contain a lower percentage of phenocrysts/microphenocrysts (35?C49%), have abundant microlites, and have less evolved groundmass glass compositions (69.4?C73.8?wt.% SiO₂). There is also evidence for crystal transfer between magma producing white and grey pumice. Thin highly evolved melt rims surround some fragmental crystals in grey pumice clasts and appear to have come from magma that produced white pumice. Furthermore, based on crystal compositions, white bands within banded pumice contain crystals originating in grey magma. Finally, only grey pumice clasts form breadcrusted surface textures. We interpret these compositional and textural variations to indicate distinct magma batches, where grey pumice originated from an originally deeper, more volatile-rich dacite recharge magma that ascended through and mingled with the volumetrically dominant, more highly crystalline chamber that produced white pumice. Shortly before eruption, the grey pumice magma stalled within shallow fractures, forming a vanguard magma phase whose ascent may have provided a trigger for eruption of the highly crystalline rhyodacite magma. We suggest that in the case of the Cerro Galán eruption, grey pumice provides evidence not only for cryptic silicic recharge in a large caldera system but also a probable trigger for the eruption.     

Female newcomers’ adjustment to life in Toronto,Canada: sources of mental stress and their implications for delivering primary mental health care

Stress disorders and other mental ill health may be brought on by the disruption caused by resettlement. We examine female newcomers’ experiences of adjusting to a new place, metropolitan Toronto, Canada and a new health care system. We consider sources of mental stress experienced during adjustment. We frame this adjustment as a process that happens over place and through time. Thematic findings of interviews (n = 35) with female newcomers from five cultural-linguistic groups are reported. Sources of stress in adjusting to life in Toronto include: navigating a new place, personal safety concerns, adapting to a new lifestyle, and finding employment. Sources of stress in adjusting to a new health care system include: learning how to access care, not having access to specialists, and adapting to a new culture of care. We conclude by considering the implications of what newcomers report for the delivery of primary mental health care (i.e. ‘first contact’ care).     

Age and significance of the Quaternary cemented deposits of the Duje Valley (Picos de Europa,Northern Spain)

Cemented calcareous breccias appear in the Picos de Europa (Cantabrian Mountains, Spain) resting on glacially abraded surfaces and covered by moraines. U/Th dating of the calcite coating the clasts was successful in two samples, the oldest one indicating that the breccias accumulated during or prior to Marine Isotope Stage (MIS) 11, and the youngest indicating later cementation during MIS 8. The former introduces a limit for the age of the glaciation preceding the breccias, which cannot correspond to an event younger than MIS 12. This is the oldest absolute age so far obtained for intercalated glacial/interglacial deposits of the Iberian Peninsula.     

The Relationship of Place Re-Making and Watershed Group Participation in Appalachia

This article explores how participation in watershed groups creates a social space that mediates the relationship between biophysical places and place-protective action. We analyze qualitative data from a survey of more than 200 watershed group volunteers in the Appalachian region of the United States who were asked to describe experiences that encouraged or discouraged their participation. “Place” emerged as a key theme, with further delineations between made places (those highly affected by human activity, including coal extraction); natural places; and re-made places (those restored by the efforts of the watershed-group participants). Our findings suggest that the places themselves—and the natural, institutional, and social resources in these places—are more than a backdrop or setting for the volunteer activities; they also inspire, enhance, and are transformed by the act of volunteering.     

A Dasymetric Map of Maine Lobster Trap Distribution Using Local Knowledge

As coastlines face increased development pressure, it is important to have the best available spatial information on coastal activities, including commercial fishing. This article describes the creation of a fine-scale spatial representation of lobster fishing activity along the Maine coast of the United States using a combination of participatory geographic information systems (GIS) and dasymetric mapping methods. These methods are employed here to support data collection from a large number of active lobster harvesters while maintaining individual privacy. The resulting representation of the fishery is designed as a planning tool for identifying potential interactions between marine resources and human activities.