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 formation of farm mounds on the Island of Sanday,Orkney

A recent archaeological site survey of the island of Sanday on Orkney has identified a distinct concentration of 15 farm mounds. An immediate need is to determine the nature, age, and processes of formation of these very distinctive landform features. This paper reports a geoarchaeological investigation of three mounds at Westbrough, Langskaill, and Skelbrae. For the island as a whole, the mounds vary in diameter from 50 to 205 m, with deposits up to a thickness of 4.3 m. The mounds vary in their morphology, reflecting complex processes of accumulation, often intense disturbance, and in some cases, erosion by the sea. Sections at the three sites are described with analytical data also being given for particle size, percent loss-on-ignition, total phosphate, δ¹³C, and radiocarbon dating. The Westbrough and Skelbrae mounds were formed post-7th century A.D.; more detailed dating was possible for the Langskaill site, which was initiated in the early to mid 13th century. A steady and relatively rapid sedimentation rate (ca. 1.9 cm year⁻¹) took place over the 200 years following the initiation of the mound. The lower part of the Westbrough mound is distinguished by the presence of peat, interpreted as discarded bedding material, but the remainder of the investigated sections are composed dominantly of mineral sediments containing organic matter of terrestrial origin. It is suggested that these materials accumulated from the ash of domestic hearths as well as from the residues of bedding material from the byres (cattle sheds). Turves (vegetation plus some underlying soil) would have been cut, dried, and then used in the byres and such turves would have retained a significant mineral content. The implication is that the inherent fertility of the island made it unnecessary for the farmers to spread the dung over the fields. This may explain why there is the distinct concentration of these mounds on the island of Sanday, an island noted in earlier times for its fertile soils developed on calcareous sands.     

Assessing risk to groundwater quality using an integrated risk framework

Source-water protection strategies are ideally focused where the greatest amount of harm reduction can occur. This process of risk management requires an assessment of the spatial variability of risk to water. The assessment methodology presented herein combines aquifer susceptibility with a hazard threat inventory and an analysis of the consequence of contamination to assess the risk to water quality. Aquifer susceptibility combines the intrinsic susceptibility of the physical system with anthropogenic features that locally increase susceptibility. Hazard threats are assessed based on the properties of the chemicals (toxicity and environmental fate), the potential magnitude (extent and quantity of release) and the likelihood of release. The consequence is herein considered as the financial costs of the loss of the resource, including the replacement of a water source and the economic loss where water intensive businesses are lost. A second scenario is included that analyses health issues related to pathogen sources as well as the financial impact to the community where people fall ill and present a financial burden to the public health care system. The risk assessment methodology is applied to the Township of Langley, in southwestern British Columbia, Canada. The results outline the most vulnerable areas as those where susceptible aquifers coexist with potential chemical and biological threats. The risk is greatest where these vulnerable areas coincide with those with the greatest potential for financial loss: within the capture zones of major municipal production wells and where private wells serve agricultural operations with high annual farm sales.     

Ocean-dumping research and monitoring: Strategies and tools

Ocean-dumping studies are designed to establish critical indexes of environmental quality to assess the impacts of ocean dumping. Strategies emphasized are: 1) source function characterization including determinations of toxicities of original wastes, 2) environmental characterization, 3) waste dispersion studies in the laboratory and at sea, and 4) waste biota interaction studies, both in the short term, within a life cycle of organisms affected, and in the long term, over many life cycles. Present tools include: 1) quantitative mapping of pollutant distribution by aerial remote sensing and moored and drifting arrays, 2) realtime tracking of waste dispersion in the ocean by 20- and 200-kHz acoustic records, 3) continuous multidepth water sampling to obtain sea truth, 4) in situ bioassay devices, and 5) mathematical dispersion models, some of which are similar to atmospheric chimney plume dispersion models.     

The stratigraphy and tectonics of the Skiddaw slates and the relationship of the overlying borrowdale volcanic series in part of the Lake District

The Skiddaw Slates consist of eight formations with the substantial thickness of about 30,000 ft. This geosynclinal sequence is of Arenig age though the highest formation may continue into the Lower Llanvirn. The polyphase tectonics of the Skiddaw Slates and the relationship of the overlying Borrowdale Volcanic Series are discussed. It is concluded that the Caledonian tectonic history of this part of Britain contains two paroxysms of orogenic activity. In addition to the orthodox end-Silurian orogenesis there was also an intra-Lower Ordovician orogenic episode which took place towards the close of the Llanvirn. During the earlier tectonic climax the Skiddaw Slates were deformed by two phases of folding. Their structure is, therefore, largely of pre-Borrowdale age and bears little relation to that of the overlying cover. After this dual deformation the slaty basement was truncated by erosion and is separated from the overlying Borrowdale Volcanic Series by an angular unconformity. Only the end-Silurian folding affects the volcanic superstructure and the younger Lower Palaeozoic sequence.