Stratigraphy,distribution and geochemistry of widespread felsic volcanic units in the Mesoproterozoic Gawler Range Volcanics,South Australia

Three widespread felsic volcanic units, the Eucarro Rhyolite, Pondanna Dacite Member and Moonaree Dacite Member, have been distinguished in the Mesoproterozoic Gawler Range Volcanics. These three units are the largest in the Gawler Range Volcanics, each in excess of 500 km³. Each unit is ～300 m thick and includes a black, formerly glassy base, a granophyric columnar‐jointed interior, and an amygdaloidal outer margin. The units are very gently dipping and locally separated by thin (<20 m) lenses of either ignimbrite (Mt Double Ignimbrite), tuffaceous sandstone or faults. The youngest unit, the Moonaree Dacite Member, covers a central area with a diameter greater than 80 km. The southern two units have east‐west extents in the order of 180 km, but are much less extensive from south to north (5–60 km). All three units are dominated by euhedral phenocrysts and are relatively crystal rich. Both the Eucarro Rhyolite and Moonaree Dacite Member contain clasts of basement granitoid and other lithologies and are locally heterogeneous in texture and composition. Some granitoid clasts have disintegrated, liberating feldspar and quartz crystals into the surrounding host. These liberated crystals cause textural variations, but can be identified on the basis of shape (amoeboid or skeletal) and/or size (megacrysts). Textural and lithofacies characteristics are consistent with the interpretation that these units are lavas; the strongly elongate distribution and wide extent of the Eucarro Rhyolite and Pondanna Dacite Member could indicate that vents were aligned along an extensive east‐west‐trending fissure system. Stratigraphic nomenclature has been revised to better reflect the presence of the three emplacement units. The oldest unit, the Eucarro Rhyolite, is dominated by plagioclase‐phyric rhyolite that locally includes granitoid clasts and megacrysts. Along the northern margin, the rhyolite is amygdaloidal and has mingled with a quartz‐rich rhyolite (Paney Rhyolite Member). The Eucarro Rhyolite and Paney Rhyolite Member replace the formerly defined ‘Eucarro Dacite’, ‘Nonning Rhyodacite’, ‘Yannabie Rhyodacite’ and ‘Paney Rhyolite’. The two younger units, Pondanna Dacite Member and Moonaree Dacite Member, are compositionally and spatially distinct, newly defined members of the Yardea Dacite.     

Arecibo radar observations of Mars surface characteristics in the northern hemisphere

Mars surface characteristics at and near the Viking Chryse and Tritonis Lacus landing areas were determined by radio scatter using the new 12.6 cm radar at the Arecibo Observatory during 1975–1976. Interpretation of each power spectrum suggests rms surface tilts of 4° at the final A1WNW (47.9°W, 22.5°N) site, 5° near the original A1 site, and 6° between the two. At the back-up site (A2) surface roughness estimates were about 4°. Striking changes in surface texture have been found near the eastern bases of Tharsis Montes and Albor Tholus, each volcanic feature marking the western boundary of very smooth surface units. The roughness sensed at 1 to 100 m scales by radar appears to be relatively independent of the surface units defined at large scale lengths by photogeologists. Radar properties thus provide an additional means by which planetary surfaces may be characterized.     

The mean Jovian temperature structure derived from spectral observations from 105 to 630 cm−1

New far-infrared observations of the NH₃ rotation-inversion manifolds in the spectrum of Jupiter have been inverted with the use oftthe detailed ammonia line opacity. A temperature of 160°K at a 1-bar pressure level and a temperature of 105°K for the minimum temperature of the inversion level at 0.15 bars have been derived for gaseous absorption due to NH₃, H₂, and He. The overall fit to the brightness temperature as a function of frequency σ is within ±1°K for 100 ≤ σ ≤ 400 cm^?1 except for the centers of the NH₃ rotation-inversion manifolds where for J ≥ 7 the fit is about 5°K too high. In the continuum for 400 ≤ σ ≤ 630 cm^?1 the fit is within 2.5°K. Consideration of an ammonia ice haze, photodissociation of NH₃ by uv radiation, NH₃ abundance variation, different He/H₂ ratios, and uncertainties in the data effect the temperatures at 1 bar and the temperature at the inversion layer by <7°K. The presently derived temperature at 1 bar of 160°K is consistent with Jovian interior models which can match the gravitational moment, J₂.     

Critical reflections on practice: the changing roles of three physical geographers carrying out research in a developing country

To date, discussions on positionality and the relationship with research collaborators have been very much in the human geography realm. In this paper, we explore issues of expertise, positionality, collaboration and participation from our perspective as physical geographers working in a developing country context. We trace our journey from identifying ourselves as top-down 'experts' to participatory 'facilitators', and the difficulties and dilemmas encountered during this journey as we coped with the contrasting challenges of academic demands and local necessities. Our experiences highlight the many assumptions we make about doing research in developing countries and the real lack of capacity in these places to undertake typical short-term research projects designed in the developed world. We conclude with a call for a longer term and deeper commitment by physical geographers to the people that we engage with in our research .     

Small-area population estimates: a review of methods used in Britain in the 1990s

"Population estimates are usually produced by local government administrations in Britain, for each small area within their authority. Increasing interest has been shown by commerce and by central government. Five main methods are identified: apportionment, ratio change, additive change, cohort survival, and local censuses. Estimation strategies also vary according to available data, the detail in which a population is estimated, and the precise combination of elements chosen from one or more of the main methods. The use of methods at the beginning of the 1990s is surveyed in this paper, and examples given. The accuracy of each main method is quantified from empirical data collated by the Estimating with Confidence project. Likely developments towards the end of the 1990s are reviewed."     

Large-scale vulnerability assessments for natural hazards

This article examines the process by which vulnerability analysis takes place at the state level for State Hazard Mitigation Plans, as required by the Disaster Mitigation Act of 2000. The methods developed by the Center for Hazards Research and Policy Development at the University of Louisville are described, followed by a brief discussion on issues and challenges. A key finding in this article is the need to understand the impact and role of vulnerability analysis on planning and policy-making at the state and local level, as it applies to the investment of funding and resources in hazard mitigation. Recommendations for policy as well as directions in future research are offered in conclusion.