Coping with the 1996 Tornado in Tangail,Bangladesh: An Analysis of Field Data

On May 13, 1996, a disastrous tornado hit the Tangail district of Bangladesh, killing more than 700 people and causing extensive damage to homes, crops, and livestock. This paper explores and analyzes how tornado victims adjusted to this destruction. Data collected from two study sites show that victims received emergency assistance from people both in neighboring areas and from more distant areas, as well as from government agencies and non-governmental organizations (NGOs). At both sites, NGOs played the leading role in minimizing the hardships of victims through extraordinary disaster relief and rehabilitation efforts. Because of the extensive support received, the tornado victims were able to return to their “normal” lives very quickly. This study concludes with several recommendations to help cope with future tornado disasters.     

Geochemical approach to magmatic evolution of Mt. Erciyes stratovolcano Central Anatolia, Turkey

Erciyes stratovolcano, culminating at 3917 m, is located in the Cappadocian region of central Anatolia. During its evolution, this Quaternary volcano produced pyroclastic deposits and lava flows. The great majority of these products are calc-alkaline in character and they constitute Kocdag and Erciyes sequences by repeated activities. Alkaline activity is mainly observed in the first stages of Kocdag and approximately first-middle stages of Erciyes sequences. Generally, Kocdag and Erciyes stages terminate by pyroclastic activities. The composition of lavas ranges from basalt to rhyolite (48.4–70.5 wt.% SiO₂). Calc-alkaline rocks are represented mostly by andesites and dacites. Some compositional differences between alkaline basaltic, basaltic and andesitic rocks were found; while the composition of dacites remain unchanged. All these volcanics are generally enriched in LIL and HFS elements relative to the orogenic values except Rb, Ba, Nb depleted alkaline basalt. ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd isotopic composition of the volcanics range between 0.703344–0.703964, 0.512920–0.512780 for alkaline basalts and change between 0.704322–0.705088, 0.512731–0.512630 for alkaline basaltic rocks whereas calc-alkaline rocks have relatively high Sr and Nd isotopic ratios (0.703434–0.705468, 0.512942–0.512600). Low Rb, Ba, Nb content with high Zr/Nb, low Ba/Nb, La/Yb ratio and low Sr isotopic composition suggest an depleted source component, while high Ba, Rb, Nb content with high La/Yb, Ba/Nb, low Zr/Nb and low ⁸⁷Sr/⁸⁶Sr ratios indicate an OIB-like mantle source for the generation of Erciyes alkaline magma. These elemental and ratio variations also indicate that the different mantle sources have undergone different degree of partial melting episodes. The depletion in Ba, Rb, Nb content may be explained by the removal of these elements from the source by slab-derived fluids which were released from pre-collisional subduction, modified the asthenospheric mantle. The chemically different mantle sources interacted with crustal materials to produce calc-alkaline magma. The Ba/Nb increase of calc-alkaline samples indicates the increasing input of crustal components to Erciyes volcanics. Sr and Nd isotopic compositions and elevated LIL and HFS element content imply that calc-alkaline magma may be derived from mixing of an OIB-like mantle melts with a subduction-modified asthenospheric mantle and involvement of crustal materials in intraplate environments.     

Some applications of humidity profiles estimated from INSAT infra red digital cloud imagery data

Moisture profiles have been estimated over the region bounded by the latitudes 40°N and 40°S and longitudes 30°E to 130°E using INSAT digital infra red cloud imagery data. The representativeness of these profiles in representing moisture field associated with the development and movement of synoptic scale systems during the period September 15th, 1996 to March 31st, 1997 has been examined. It has been shown that the changes in the moisture field associated with the withdrawal of the southwest and northeast monsoons from the Indian sub-continent, development and movement of synoptic scale sytems (depressions, tropical cyclones and waves in easterlies) and equatorial troughs in the Indian Ocean could be clearly seen in humidity profiles. The initial development of tropical systems is first seen in the humidity field in the upper troposphere. These profiles could be used in monitoring the initial development and subsequent movement of tropical systems. Further the data on moisture distribution from the data gap regions of the Indian Ocean could be used as an additional source of moisture in numerical analysis and prognosis.     

Early tertiary deltaic sedimentation around Kalka and Nahan, Punjab Himalaya, India

During the Early Tertiary epoch a basin of deposition covered almost all the present Himalayan foot hill zone. Large quantities of detrital sediments were transported from the northern source area to the depositional basin. The rivers carrying the sediment load formed large delta complexes. In the area studied at least two such delta complexes, one around Kalka and the other around Nahan, were formed; of these the one around Kalka contains the greatest volume of sediments.

The recognition of the deltas is based on: (a) greater abundance of stream deposits than deposits of other environments; (b) lithologic criteria, particularly sedimentary structures, repetitive lithologic associations; (c) the general coarsening-upward nature of the sediments; (d) strong unimodal current direction; (e) the typical lenticular lithogenetic model, common in recent deltas.

The rocks of the Nahan Group are divisible into three formations at Kalka and two formations at Nahan where central formation did not develop. Himalayan tectonism has largely controlled both delta formation and stratigraphy.

The differential rates of sedimentation greatly influenced the rates of subsidence within the Nahan basin. The sediments of the Nahan Group are roughly bounded between two major phases of Himalayan uplift, namely Eocene and middle Miocene tectonic movements. The effects of intermittent tectonic pulses are well depicted in rocks of the Nahan Group. The intensity of the tectonism that controlled both the source-area rise and basin subsidence during deposition of the Nahan Group of sediments was nonuniform, both in vertical and lateral directions. Because of a generally higher rate of deposition compared to the rate of subsidence, the rocks of the Nahan group represent a normal regressive basin-filling sedimentation, forming thick detrital deposits due to progradation of younger deltas beyond the distal end of older deltas.     

Total mercury content in some marine fish from the Indian Ocean

Total mercury was estimated in liver, gonads and muscle of some of the marine fishes from the Indian Ocean. The highest mercury concentration was observed in the muscle of sharks while the total mercury concentration was practically non-detectable in the liver and gonads. The range of all the values was 0.09–0.21 ppm (wet weight basis) and is quite low to reflect any possible mercury contamination.     

Mineralogical variations in the Delakhari sill,Deccan trap intrusion,central India

The Delakhari sill (maximum thickness cf. 200 m) is the most extensive Deccan Trap instrusion which occurs in central India, between longitutdes 78°3835 to 78°2240 and latitudes 22°26 and 22°2230. Based on petrographic examination, the sill is divided, from bottom to top, into (1) the Lower Chilled Zone (LCZ), up to 8 m thick, marked by abundant interstitial glass and an overall fine grain size, (2) the Olivine-Rich Zone (ORZ), 27 m thick, enriched in olivine (relative to the other zones in the sill), (3) the Central Zone (CZ), 70 m thick, marked by depletion in olivine and overall coarse grain size, (4) the Upper Zone (UZ), 55 m thick, marked by the presence of two chemically and morphologically distinct olivine types and abundant interstitial granophyre, and (5) the Upper Chilled Zone (UCZ), 10–25m thick, marked by abundant interstitial glass.Compositions of the pyroxenes and olivines show an overall increase in Fe/Mg with crystallization, but extensive interzonal and intrazonal variations and overlaps exist. Olivine ranges from Fa₂₄ (ORZ) to Fa₉₅ (UZ). In the UZ and inner UCZ, an equant (Fa_44–50, called type-A olivine) and interstitial skeletal olivine (Fa_70–95, called type-B olivine) occur together. Compositions of the Ca-rich and Ca-poor pyroxenes fall in the range Wo₃₈En₃₄Fs₂₈ to Wo₃₃En₈Fs₅₉ and Wo₁₄En₄₁Fs₄₅ to Wo₁₆En₁₉Fs₆₅, respectively. Overall, the two pyroxene trends converge with Fe-enrichment except for one anomalous sample from the UZ which contains a Ca-rich (Wo₃₄En₈Fs₅₈) and a Ca-poor (Wo₁₀En₁₈Fs₇₂) pyroxene well within the Forbidden Zone of Smith (1972).Compositions of coexisting oxide minerals indicate that the sill crystallized at oxygen fugacities from 10^–10 atm (ORZ) to 10^–13 (UZ). The magma prior to intrusion appears to have been derived from a more primitive melt from which a considerable amount of olivine and plagioclase have fractionated out. A model of open, interrupted fractional crystallization in the sill is proposed to explain the compositional variations exhibited by the major mineral phases.A previous study (Crookshank 1936) concluded that the sill is actually a multiple intrusion and has given rise to the lowermost (flow I) and the topmost (flow III) lava flows in the neighboring area around Tamia (78°4015, 22°2035). The olivines of flows I and III have compositions Fo₈₇ and Fo₈₈ respectively, and are much more Mg-rich than the maximum Mg-rich olivine (Fo₇₆) of the Delakhari sill, refuting the possibility of the sill being the feeder of the lava flows I and III.Geosciences Department, University of Texas at Dallas Contribution No. 338     

Dynamical Initialization of Boundary-Layer Data

A procedure for the dynamic initialization of wind and temperature fields within the atmospheric boundary layer (ABL) is presented. The procedure uses transilient turbulence theory to assess the turbulent fluxes from observed wind and temperature data, which are used to estimate the eddy transfer coefficients, so enabling a local closure ABL model to be integrated forward in time to a new steady state. The method has been applied to initialize kytoon data taken at Kharagpur (22.3° N, 87.2° E) during the MONTBLEX field programme. Results of a case study for 17 June 1990 are discussed.     

Stresses in column-supported hyperboloidal shells subject to seismic loading

The computation of stresses within a finite element displacement method analysis of a shell of revolution is considered. The common procedure of applying the kinematic and constitutive laws to the displacement functions is examined and justified for models where the displacements are represented by high-order polynomial expansions. Also, two alternative computational formats within this technique are explored. The influence of the column-supported base condition on a hyperboloidal shell of revolution is studied with respect to the stresses calculated from a response spectrum analysis. These studies emphasize the importance of accurately modelling the base region of a column-supported shell such as a hyperbolic cooling tower.     

Origin of garnet in the basic granulites around Saltora,W. Bengal,India

Garnetiferous basic granulites occur, as parts of hornblende-pyroxene- and pyroxene granulites, in a Precambrian terrain around Saltora. The chemistry of the garnetiferous basic granulites is broadly similar to that of the hornblende-pyroxene granulites, their immediate precursors, but in detail they have distinctly higher Fe/Mg ratios. The compositions of the major mafic silicates of the garnetiferous varieties do not reflect higher pressures of formation: the Jd/Ts ratios in calcic pyroxenes are similar to those from the non-garnetiferous varieties, and the pyrope contents of garnets are low. Exchange equilibrium in respect of major elements was established among the mafic silicates in spite of garnets being late overprints. The orthopyroxene — calcic pyroxene pairs from the garnetiferous granulites show lower values of K _D(Mg-Fe) ^opx-cpx than those from the non-garnetiferous granulites, pointing to lower temperature of equilibration. The K _D(Mg-Fe) ^opx-hbl K _D(Mg-Fe) ^cpx-hbl relations show that the more magnesian triads equilibrated at lower temperatures; viewed against experimental data regarding the effect of Mg/Fe ratios on the appearance of garnets in basic rocks, formation of garnets by cooling is strongly indicated. Several intergrowth textures, especially garnet-ilmenite and garnet-quartz (±albite) symplectites, and modal relations argue in favour of composite reactions of the type hornblende+ quartz-→calcic pyroxene+garnet+albite+H₂O, which couple hornblende breakdown reactions with orthopyroxene+anorthite→garnet reactions. The approximate range of pressure and temperature conditions, estimated from experimental data, are 6–8.5 kb and 750–830° C. Since garnets formed by cooling in iron-rich granulites, the garnetiferous granulites do not represent higher pressure subfacies of the granulite facies.