Geophysical surveys in Parvati valley geothermal field, Kullu, India

Direct current resistivity surveys and shallow temperature measurements were carried out for geothermal exploration in a part of Parvati valley, goethermal field, Himachal Pradesh, India. At a few places, the Schlumberger soundings pointed to the presence of a relatively low-resistivity shallow layer, which probably represents fractured and jointed quartzite, saturated with hot/cold water. Wenner resistivity profiles indicate the presence of some possible shallow subsurface lateral hot water channels across the valley at Manikaran. Shallow temperature measurements show a good subsurface thermal anomaly near the confluence of the rivers Brahmaganga and Parvati. The results of the survey, together with other available geodata, suggest that an anomalous heat source does not lie beneath the study area.It is postulated that the meteoric water, originating at high elevations after heating as a result of circulation at depth, emerges at the surface in the Parvati valley as hot springs, after mixing in various proportions with near surface cold waters.     

Impact of tsunami on texture and mineralogy of a major placer deposit in southwest coast of India

The great Indonesian earth quake (26 December 2004) triggered a tsunami wave across the Bay of Bengal and Indian Ocean basins and has brought a major havoc in several countries including India. The coastal segment between Thotapalli and Valiazhikal in Kerala state of southwest India, where considerably rich beach placer deposit with ilmenite percentage of more than 70% is concentrated, has been investigated to understand the impact of tsunami on coastal sediments. The grain size analysis flashes out the significant differences between the pre- and post-tsunami littoral environments. While the mineral grains collected during pre-tsunami period show well-sorted nature, the post-tsunami samples represent moderately to poorly sorted nature. Similarly, unimodal and bimodal distributions of the sediments have been recorded for pre- and post-tsunami sediments, respectively. Further, mineral assemblages corresponding to before and after this major wave activity clearly indicate the large-scale redistribution of sediments. The post-tsunami sediments register increasing trends of garnet, sillimanite and rutile. The total heavy mineral percentage of the post-tsunami sediment also shows an improved concentration, perhaps due to the large-scale transport of lighter fraction. Magnetite percentage of post-tsunami samples reflects higher concentration compared to the pre-tsunami samples, indicating the intensity of reworking process. X-ray diffraction patterns of ilmenite grains have confirmed the increased presence of pseduorutile, and pseudobrookite in post-tsunami samples, which could be due to the mixing of more altered grains. SEM examination of grains also confirms the significant alteration patterns on the ubiquitous mineral of placer body, the ilmenite. The reason for these textural, mineralogical and micromorphological changes in heavy minerals particularly in ilmenite, could be due to the churning action on the deeper sediments of onshore region or on the sediments entrapped in the near shelf region of the area, by the ∼ 6 m high tsunami waves.     

The geochemical study of fluvio-lacustrine aquifers in the Kathmandu Basin (Nepal) and the implications for the mobilization of arsenic

The geochemical analyses of fluvial-lacustrine aquifer sediments of the Kathmandu Valley have been made as a step in assessing the environment for the mobilization of arsenic in groundwater. Elements measured by X-ray fluorescence (XRF) include 4 major oxides (Fe₂O₃, TiO₂, CaO, P₂O₅) and 14 trace elements (As, Pb, Zn, Cu, Ni, Cr, V, Sr, Y, Nb, Zr, Th, Sc and TS). Elution tests of 15 selected core samples were also carried out to determine the potential leaching of arsenic from the sediments. The XRF results show that average bulk concentrations of the major oxides and trace elements are similar to modern unconsolidated sediments and average upper continental crust. However, the abundance of elements varies with grain size, with higher concentrations in finer-size grades. Variations in elemental abundances within the basin are strongly controlled by sediment facies. The elution tests show that greater amounts of arsenic are generally eluted from the fine sediments, although the rates are variable. The results overall suggest that As concentrations in the bulk sediments are not a controlling factor for elevated As in the Kathmandu Basin groundwater, and the roles of other factors such as redox conditions and organic matter contents are likely to be more significant.     

Refinement of the synthetic hydroxyapatite cell parameters

High-precision, computer-refined values of the cell parameters of calcium hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂, have been determined with an X-ray diffractometer, internally standardized by means of sodium chloride. The results obtained are as follows: a ₀=9.4192 Å c ₀/a ₀=0.731 c ₀=6.8867 Å volume=529.2 ų The apatite work was supported by a research grant DE-02105 from the United States Department of Health, Education, and Welfare. I am very grateful to Dr. W. R. Liebenberg, Dr. S. A. Hiemstra and Dr. H. V. R. von Rahden of National Institute for Metallurgy, South Africa for their valuable help and interest and Prof. Nelson Fuson and Prof. James R. Lawson for advice and discussion.     

Daily Weather Observations in Sixteenth-Century Europe

Thirty-two weather diaries written in astronomical calendars in central Europe in the late fifteenth and sixteenth centuries are presented and discussed. Systematic weather observations were promoted by the rise of planetary astronomy and its application in astro-meteorology. The practice of keeping weather diaries spread from Cracow (Poland) to Ingolstadt (Germany) and from there to other universities. The data obtained from these sources provided the backbone for setting up series of precipitation indices for Poland, Germany and Switzerland. Monthly statistics of days with precipitation, snowfall and frost were computed by counting the relevant entries in the most important diaries. The results were compared with either those obtained from instrumental measurements in the same place or with those from modern instrumental measurements in a neighbouring place. The final results show that autumn was considerably colder in the early sixteenth century. April was considerably drier and July was wetter during the period 1508-1531 than during 1901-1960. In order to highlight the impact of weather patterns on grain prices in a year of crisis, the timing of wet and dry spells in southern Poland and southern Germany is compared for the year 1529. Winters became 1.7°C colder from 1564 to 1576 and the month of July tended to be wetter than in 1901-1960. Details noted in the diaries kept between 1585 and 1600 by the astronomers Brahe (near Copenhagen) and Fabricius (in the Ostfriesland region of northwestern Germany) closely agree. It rained more often in June and July and temperatures dropped. The winter months were more frequently dominated by winds from easterly directions, the frequency of snowfall was higher and a deficit occurred in precipitation. This points to a higher frequency of high pressure in the Fennoscandian area with cold air advection from the east or northeast.     

Interaction between diapirism and sediment loading at the shelf-slope boundary,northwest Gulf of Mexico

During the last low stand of sea level, rivers and streams drained across the present northwestern Gulf of Mexico continental shelf depositing sediments in several shallow-water deltas near the present shelf-slope boundary. The weight of these wedges of prograded sediments triggered or augmented both subsidence of local depositional basins and upward movement of diapiric material around the basin edges. A depositional basin off the southwestern Louisiana coast records migration of the basinal axis during late Pleistocene and Holocene time indicating relative growth of diapirs along the basin margin throughout the most recent geological record.     

Use of Roche coordinates in the problems of small oscillations of tidally-distorted stellar models

Kopal's method of Roche coordinates used by us in an earlier paper (Mohan and Singh, 1978) to study the problems of small oscillations of tidally-distorted stars has been extended further to take into account the effect of second-order terms in tidal distortion. Our results show that the effect of including terms of second order of smallness in tidal distortion in the metric coefficients of the Roche coordinates of tidally distorted stars is quite significant, especially in case of stars with extended envelopes and (or) larger values of the mass ratio of the companion star producing tidal distortion. Some of the models which were earlier found stable against small perturbations now become dynamically unstable with the inclusion of the terms of second order of smallness in tidal effects.At present on leave of absence with the department of Mathematics, College of Science, Baghdad, Iraq.     

AstroGrid: A place for your science

Nicholas A Walton, Silvia Dalla, Eduardo Gonzalez-Solarez, Anita Richards and Jonathan Tedds show off the fast-developing astronomical applications of the UK's virtual observatory service.