Preliminary observations of solar radio sources with the Culgoora radioheliograph operating at four frequencies

The Culgoora radioheliograph has been modified for observing at 327.4 MHz, which is in addition to the three frequencies (43.25, 80, and 160 MHz) previously available. At the new frequency the array beamwidth is 56, which represents the highest resolution yet available for metre-wavelength solar mapping.At 327.4 MHz the sources of radio emission are mainly in the lowest layers of the corona. Some preliminary four-frequency observations have been made of type I storms. It is found that the source size generally decreases with increasing observing frequency. This result confirms earlier suggestions that the sources of both type I and type III emission are contained in structures whose boundaries diverge outwards in the corona.     

Age estimates of coastal terraces in the Andaman and Nicobar Islands and their tectonic implications

The great Indian Ocean earthquake of December 26, 2004 caused significant vertical changes in its rupture zone. About 800 km of the rupture is along the Andaman and Nicobar Islands, which forms the outer arc ridge of the subduction zone. Coseismic deformation along the exposed land could be observed as uplift/subsidence. Here we analyze the morphological features along the coast of the Andaman and Nicobar Islands, in an effort to reconstruct the past tectonics, taking cues from the coseismic effects. We obtained radiocarbon dates from coastal terraces of the island belt and used them to compute uplift rates, which vary from 1.33 mm yr^− 1 in the Little Andaman to 2.80 mm yr^− 1 in South Andaman and 2.45 mm yr^− 1 in the North Andaman. Our radiocarbon dates converge on  600 yr and  1000 yr old coastal uplifts, which we attribute to the level changes due to two major previous subduction earthquakes in the region.     

Changes of deformational and reservoir properties of arenaceous-argillaceous rocks due to operation of underground gas storage facilities

This paper discusses issues of the decline of the reservoir properties of arenaceous-argillaceous rocks as a result of declining porosity due to long-term operation of underground gas storage facilities. An analysis of the many-year operation of storage facilities, as well as calculation, has revealed that the active capacity of a storage reservoir gradually decreases under certain conditions of underground storage operations. We performed a series of experiments with model specimens in order to support the hypothesis of decreasing reservoir (capacity-filtration) properties because of changes in the value and structure of the pore space. These experiments showed that the cyclic loading and unloading of arenaceous-silty rocks during long-term operation of underground gas storage facilities can significantly decrease the reservoir parameters of reservoirs created within worked out gas-and-gas condensate fields. Laboratory studies of model specimens corresponding to feldspar sandstone in their composition, porosity, and strength proved that porosity considerably decreases in such reservoirs at actually existing values of formation pressure. Tests of sand performed under conditions close to those existing during the development of hydrocarbon fields also showed that their permeability gradually decreases in the process of cyclic changes of effective pressure.     

Seismic hazard assessment of Chennai city considering local site effects

Chennai city suffered moderate tremors during the 2001 Bhuj and Pondicherry earthquakes and the 2004 Sumatra earthquake. After the Bhuj earthquake, Indian Standard IS: 1893 was revised and Chennai city was upgraded from zone II to zone III which leads to a substantial increase of the design ground motion parameters. Therefore, a comprehensive study is carried out to assess the seismic hazard of Chennai city based on a deterministic approach. The seismicity and seismotectonic details within a 100 km radius of the study area have been considered. The one-dimensional ground response analysis was carried out for 38 representative sites by the equivalent linear method using the SHAKE91 program to estimate the ground motion parameters considering the local site effects. The shear wave velocity profile was inferred from the corrected blow counts and it was verified with the Multichannel Analysis of Surface Wave (MASW) test performed for a representative site. The seismic hazard is represented in terms of characteristic site period and Spectral Acceleration Ratio (SAR) contours for the entire city. It is found that structures with low natural period undergo significant amplification mostly in the central and southern parts of Chennai city due to the presence of deep soil sites with clayey or sandy deposits and the remaining parts undergo marginal amplification.     

Late Quaternary Bison diminution on the Great Plains of North America: evaluating the role of human hunting versus climate change

Body size changes of Bison and mortality age structure data document the effects of climate-driven environmental change and human hunting pressure on large mammals in North America. Morphometric and mortality data are drawn from 58 archaeological and 9 paleontological localities dating between 37,000 and 250 calBP. Proxy information on body size is based on measurements recorded on 901 adult calcanei (os calcis) and 1026 humeri. In addition, published mortality profiles from 24 archaeological faunal assemblages spanning the last 14,000 years were used to approximate the age structure of bison populations. These results suggest that dramatic diminution in bison body size occurred in several short bursts, rather than a continuous gradual decline. These periods of rapid size reduction correlate with times of ecological reorganization, when aridity-driven changes in grasslands decreased forage quality and availability. Mortality age data indicate that the decrease in body size occurred in a context where there was no evidence for a progressively severe juvenile bias in bison populations. Overall, it appears that the changes in body size were a reaction to environmental conditions rather than the result of human predation pressure.     

Estimating potential landslide sites of an upland sub-watershed in Western Ghat’s of Kerala (India) through frequency ratio and GIS

The purpose of this study is to assess the susceptibility of landslides in parts of Western Ghats, Kerala, India, using a geographical information system (GIS). Landslide inventory of the area was made by detailed field surveys and the analysis of the topographical maps. The landslide triggering factors are considered to be slope angle, slope aspect, slope curvature, slope length, distance from drainage, distance from lineaments, lithology, land use and geomorphology. ArcGIS version 8.3 was used to manipulate and analyse all the collected data. Probabilistic-likelihood ratio was used to create a landslide susceptibility map for the study area. The result was validated using the Area under Curve (AUC) method and temporal data of landslide occurrences. The validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide locations. As the result, the success rate of the model was (84.46%) and the prediction rate of the model was (82.38%) shows high prediction accuracy. In the reclassified final landslide susceptibility zone map, 5.68% of the total area is classified as critical in nature. The landslide susceptibility map thus produced can be used to reduce hazards associated with landslides and to land cover planning.     

Sediment salt-load in the St Lucia Estuary during the severe drought of 2002–2006

The purpose of this study was to determine whether there was a sufficiently high residual salt load in the dry sediments of the St Lucia Estuary to cause salinity problems should it later fill up with either freshwater or seawater. The estuary lakes have suffered the effects of a severe drought since 2002 with the result that many areas were dry, and the salinity of the residual water varied between 4 psu and up to five times that of seawater. Measurements of the salts content in the sediments to a depth of 20 cm showed that more than 2 million tonnes of salt was held in this layer of the sediment in 2006. Recent management of the estuary (since 1970) has ensured that the mouth was not artificially opened. This was to prevent the inflow of seawater, with its salts, that would otherwise enter while the drought was in place. The results of the sediment salinity data showed that if the drought had been broken and the lake area filled with rain and river water, the resulting salinity would be about 6 psu. In March 2007, Cyclone Gamede in the Indian Ocean off the east coast of South Africa produced a wave climate at sea that resulted in the mouth breaching; thus introducing an estimated 12 million tonnes of salts. The high salinity in the system resulting from this breach is expected to have an adverse effect on the ecology of the system, whereas the residual salinity in the sediments would not have caused an environmental problem. If the estuary and lake system were to fill completely with seawater, the residual salts together with seawater will raise the salinity to an initial value higher than 40 psu, which will have the effect of suppressing much of the important submerged vegetation that is vital for sustaining juvenile fish in the system. Many of the large fauna will also suffer from a shortage of freshwater.     

Problems of soil and groundwater pollution in the disposal of “marble” slurries in NW Sicily

This work deals with disposal of slurries generated during the cutting and polishing processes of slabs of decorative sedimentary carbonate rocks in the north western Sicily. At present, they are used as fillers of dismantled quarries near the sawmills and, as a final step of reclamation, are covered with earth layers. In spite of such inexpensive solution, there is lack of knowledge about the composition of the waste. In order to assess if there is any threat for the environment and to suggest indications for alternative solutions, such as recycling or inactivation processes, the slurries were analysed by XR diffraction, simultaneous thermal analysis, ICP/MS, ionic chromatography, FTIR, UV-Vis, COD and TOC measurements, grain size analysis. Results indicate that the slurries can threaten the groundwater, because of the high chemical oxygen demand; furthermore they can modify the mechanism of groundwater recharge, because of their grain size distribution. Some laboratory tests show that, even in very aggressive conditions, the solid pollutants persist in the waste and slowly release into water the products of their degradation. The slurry therefore should be subjected to inactivation treatment before disposal or, alternatively, recycled as secondary raw material for a suitable process.     

Application of precise 142Nd/144Nd analysis of small samples to inclusions in diamonds (Finsch,South Africa) and Hadean Zircons (Jack Hills,Western Australia)

¹⁴⁶Sm–¹⁴²Nd and ¹⁴⁷Sm–¹⁴³Nd systematics were investigated in garnet inclusions in diamonds from Finsch (S. Africa) and Hadean zircons from Jack Hills (W. Australia) to assess the potential of these systems as recorders of early Earth evolution. The study of Finsch inclusions was conducted on a composite sample of 50 peridotitic pyropes with a Nd model age of 3.3 Ga. Analysis of the Jack Hills zircons was performed on 790 grains with ion microprobe ²⁰⁷Pb/²⁰⁶Pb spot ages from 3.95 to 4.19 Ga. Finsch pyropes yield 100 × ?¹⁴²Nd = ? 6 ± 12 ppm, ?¹⁴³Nd = ? 32.5, and ¹⁴⁷Sm/¹⁴⁴Nd = 0.1150. These results do not confirm previous claims for a 30 ppm ¹⁴²Nd excess in South African cratonic mantle. The lack of a ¹⁴²Nd anomaly in these inclusions suggests that isotopic heterogeneities created by early mantle differentiation were remixed at a very fine scale prior to isolation of the South African lithosphere. Alternatively, this result may indicate that only a fraction of the mantle experienced depletion during the first 400 Myr of its history. Analysis of the Jack Hills zircon composite yielded 100 × ?¹⁴²Nd = 8 ± 10 ppm, ?¹⁴³Nd = 45 ± 1, and ¹⁴⁷Sm/¹⁴⁴Nd = 0.5891. Back-calculation of this present-day ?¹⁴³Nd yields an unrealistic estimate for the initial ?¹⁴³Nd of ? 160 ?-units, clearly indicating post-crystallization disturbance of the ¹⁴⁷Sm–¹⁴³Nd system. Examination of ^146,147Sm–^142,143Nd data reveals that the Nd budget of the Jack Hills sample is dominated by non-radiogenic Nd, possibly contained in recrystallized zircon rims or secondary subsurface minerals. This secondary material is characterized by highly discordant U–Pb ages. Although the mass fraction of altered zircon is unlikely to exceed 5–10% of total sample, its high LREE content precludes a reliable evaluation of ¹⁴⁶Sm–¹⁴²Nd systematics in Jack Hills zircons.