Satellite-based assessment of physiographic disposition to health problems in kasargod district,Kerala, India

Photo interpretation and digital classification of IRS LISS -III sensor data have been carried out for a few villages affected by abnormal health problems in the Kasargod district of Kerala State. Physical location of the affected villages in relation to the agricultural lands use, watershed characteristics and the extent of cashewnut plantations are studied. It was found that the villages affected by the health problems are located in the microwatersheds that have steep slopes, nearly circular in shape, high runoff potential. The first order streams within these micro-watersheds are originating from the cashewnut plantations that are sprayed with a toxicant called Endosulfan. The study recommends to stop aerial spraying of any toxicant on the cash crops of these watersheds.     

Geomorphological study of sundarban deltaic estuary

Study of landforms in Sundarbans deltaic estuary is necessary in regular basis due to its importance and impact on ecology, climate and economy. Remote sensing has proved as an important tool to study this. Multi-temporal satellite data helps to delineate the various geomorphic classes in different time domain and also provide inputs to study the coastal erosion and accretion. Finer spatial and better temporal resolution will be an added adventure for this kind of study.     

HE 1127–1304: the largest radio quasar

By considering the propagation of low-amplitude magnetohydrodynamic waves in partially ionized plasmas, it is shown that the ion-neutral drift (ambipolar diffusion) induced by the waves can have specific effects on the molecular chemistry of cold material. The chemistry occurring in gas swept by Alfvén waves is described and it is shown that this leads to spatial variations in the deuterium fractionation ratios of, for example, HCO⁺ and N₂H⁺, on spatial scales of a few hundredths of a parsec, depending upon the fractional ionization of the ambient medium. The possibility of detecting interstellar Alfvén waves by molecular spectroscopy and their effect of producing small-scale chemical abundance gradients in molecular clouds are briefly discussed.     

Hydrogeomorphological studies by remote sensing application in niva river basin, chittoor district, andhra pradesh

To evaluate the hydrogeomorphological conditions of Niva river basin Chittoor district, Andhra Pradesh, geological, hydrogeological and geomorphological studies were carried out. through visual interpretation of Landsat 5, FCC with adequate ground truth. The study shows that the Niva river basin is occupied by granites and gneisses of Archaean age with intrusive bodies of dolerites. The recent alluvium deposits are present along the stream courses. The study area is traversed by various directional fractures/lineaments and most of them are NESW, ENE-WSW and EW directions. Groundwater potential of geomorphological units viz. Denudational hill, Residual hill, Pediment, Pediplain and Valley fill is discussed.     

Hydroclimatic fluctuations of the Upper Narmada catchment and its association with break-monsoon days over India

In this paper, hydroclimatic fluctuations of the Upper Narmada catchment (upto Narmadasagar damsite) have been studied by examining the time series (1901–80) of (i) 1-to 10-day annual extreme rainfall; (ii) seasonal total rainfall between May and October; (iii) the precipitation concentration index (PCI); (iv) a modified version of PCI(MPCI); and (v) parameters of the periods contributing specified percentages of rainfall to annual total. Most of these parameters followed the normal distribution and did not show any significant long-term trend. However, some dominant long period oscillations have been noticed in extreme rainfall, seasonal rainfall, PCI and MPCI series. Influence of break-monsoon days over India during July and August on the rainfall activities of the Upper Narmada catchment has also been investigated and salient findings discussed.     

Physical and chemical response of zircons to deformation

An investigation of U-Pb isotopic systematics in zircons from mylonitized Henderson Gneiss (Sinha and Glover 1978) revealed that selected zircon fractions from the mylonite zone suffered total loss of radiogenic Pb at 460 m.y. To further investigate the relationship between Pb loss, U gain, and grain size reduction associated with increasing strain in the shear zone, we have characterized the chemistry and morphology of zircons in the mylonitic rocks, using both electron microprobe analysis and scanning electron microscopy.SEM photographs of the zircons indicate that strain-correlated fracturing and size reduction of the zircons accompanied Pb loss throughout the mylonite zone. Stresses imposed by the expansion of initially U-rich, -damaged portions of the crystal resulted in microfracturing of the more brittle crystalline material proximal to the U-rich zones. During mylonitization, fractures propagated preferentially along these zones allowing metamorphic fluids to penetrate the easily-leached, -damaged portions of the zircons. Removal of 75% of the radiogenic Pb from zircons in the least-deformed zone of the mylonites may have occurred via this mechanism.Irregular, porous zircon overgrowths are also evident from the SEM photographs. Overgrowths are strongly enriched in U, Y and P with respect to the relict, Henderson Gneiss-derived cores, and tend to increase in volume from the protomylonite to the blastomylonite. Thus, the development of overgrowths on the zircons accounts for the U gain observed by Sinha and Glover (1978), and indicates that the transport of high field strength cations (e.g., Zr⁴⁺, Hf⁴⁺, U⁴⁺, etc.) occurred during prograde mylonitization at 460 m.y.A retrograde shearing event at 273 m.y. caused no further disturbance in the U-Pb isotopic systematics of the zircons. Pb retention by zircons during the later episode may have been the result of 1) the participation of H₂O-rich, relatively noncorrosive fluids and/or 2) the lack of further fracturing and size reduction in a strain gradient of lower magnitude than the prograde event.     

Palaeo-tectonic environment of the Precambrian basaltic mafic dykes on the application of chemical discriminants

Dykes of Chitaldurg and Newer Dolerite I are OFB and represent early attempts to rift and to generate oceanic crust. Shimoga dykes are CAB and belong to orogenic phase. Guntur dykes and Ananthapur-Chittoor dykes are OIB and these are related to ‘hot spot’. Newer Dolerite II is CONB and belongs to healing and filling of fractured crust. The Cuddapah dykes are transitional to all magma types and these represent a compound event of rifting and filling of fractured continental crust.     

Spectral reflectance studies on certain fuel wood species

Spectral reflectance studies are carried out on certain fuel wood species with reference to IRS bands 1, 2, 3 and 4. The reflectance values are correlated with different types of soil substratum, spacing and leaf area index. The radiometric responses of adaxial and abaxial surfaces of leaves, reflectance from canopy and transmittance through canopy are studied. Variations in the values are discussed in relation to the above parameters.     

Wave-induced nearshore circulation along the Calangute-Candolim beach,Goa, west coast of India

The wave-induced nearshore circulation model suggested by Noda has been modified and applied for three small segments along the coast of Goa. The present model incorporates the prevailing bottom topography and considers its variation along with the radiation stress as the driving force for the circulation. We find that the flow pattern is strongly dependent on bottom topography. While normal incidence of waves results in a cellular pattern of flow, meandering flows prevail for oblique incidence along the coast. The shoreward flows are always located over shoals while the rip currents prevail over channels. The onshore/offshore flows show magnitudes as high as 3·1 m/s, while those alongshore reach a maximum of 1·1 m/s. When compared with field observations these values are slightly higher.     

Strontium isotopic and selected trace element variations between two Aleutian volcanic centers (Adak and Atka): implications for the development of arc volcanic plumbing systems

Major and trace element concentrations and initial ⁸⁷Sr/⁸⁶Sr ratios of lavas from the Aleutian volcanic centers of Adak and Atka have been used to study the evolution of their respective lithospheric plumbing systems. The centers are within 150 km of one another and show similar overall silica ranges (47–67%), but Adak (40 km³) is smaller than Atka (200 km³). Adak's lavas are chemically and isotopically heterogeneous (⁸⁷Sr/⁸⁶Sr:0.70285–0.70330) and two units contain lithospheric xenoliths. The lavas of the much larger Atka, on the other hand, have much less variability in major and trace elements as well as ⁸⁷Sr/⁸⁶Sr (0.70320–0.70345). We suggest that these characteristics are a measure of the relative maturity and cleanliness of the lithospheric plumbing systems that supply magma to these centers. Because Aleutian volcanic centers often remain fixed for relatively long periods of time (5 m.y.), once established, magmatic passageways are repeatedly used. Young plumbing systems are relatively cool and contain large amounts of wallrock contaminant, and ascending magmas undergo contamination as well as concurrent crystallization and fractionation. With time, however, heat and mass transfer between ascending magmas and wallrock produce thermal and chemical boundary layers that insulate subsequent magmas. In effect, the plumbing system matures. The chemical heterogeneity displayed by young, dirty systems (like Adak) reflects not only the magma source but also the wallrock encountered during ascent and possibly the effects of extensive crystal fractionation. Thus, it is the petrologic data of mature, clean systems, like Atka, that yield the most direct and unambiguous information on the ultimate origin of the lavas and their near surface evolution.