Elastic properties of granulite facies rocks of Mahabalipuram, Tamil Nadu, India

Compressional and shear wave velocities and attenuation measurements have been carried out in some of the borehole samples of acidic, basic and intermediate granulites of Mahabalipuram, Tamil Nadu, India. The results have been obtained at ambient conditions using ‘time-of-flight’ pulse transmission technique at 1.0 MHz frequency. The results show linear relationships between velocity and density, and velocity and attenuation properties of the rocks. The acidic granulites show lower velocities and higher attenuation than the intermediate and basic granulites. The average values of the Poisson’s ratio of acidic, intermediate and basic granulites have been found to be 0.210, 0.241 and 0.279 respectively. The variations in velocities and attenuation in these low porosity crystalline rocks are found to be strongly influenced by their mineral composition. The laboratory velocity data (extrapolated to high pressure) of the present study and the published field velocity data from deep seismic sounding studies indicate that these granulite facies rocks may belong to mid-crustal depths only.     

KIDS AND SPACE IN THE PUERTO RICAN HIGHLANDS

ABSTRACT. The spatial world of the child comprises two great realms, “in’ and “out,’ more or less corresponding to the great behavioral domains of “got to’ and “doing nothing.’ Within the “got‐to’ domain–and thus “in’–are home, school, and other loci of secure, stable authority. Included in “doing nothing’–and so “out’–are street and yard, field and stream, pool hall and movie theater, the spaces of games, things to do, and really doing nothing. This study looks at the shifting relationships of these realms across the life cycle of kids in the highlands of Puerto Rico in 1969–1970.     

HUMBOLDT AND THE HABITABILITY OF CANADA'S GREAT NORTHWEST*

ABSTRACT. Alexander von Humboldt's influence in British North America during the nineteenth century was filtered mainly through British imperial applications of “Humboldtian” sciences, including geomagnetism and biogeography. The best‐known examples include Edward Sabine and John Henry Lefroy, Royal Artillery officers who, during the 1830s and 1840s, transformed British North American outposts and territories, including Rupert's Land, into Humboldtian sites and regions in Great Britain's imperial “magnetic crusade.” Important groundwork had already been laid by John Richardson, who applied data accrued during John Franklin's overland Arctic expeditions during the 1820s to systematize Humboldtian inquiries into the habitability of Canada's Great Northwest. Despite both the relative decline of Humboldtian sciences by midcentury and Humboldt's own reservations about the political ramifications of his science, his “cosmic” outlook circulated in Canada to refine territorial expansionists' scientistic arguments justifying annexation of Rupert's Land after the monopoly of the Hudson's Bay Company expired in 1869.     

On global forces of nature driving the Earth’s climate. Are humans involved?

The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible.     

Avalanche Risk During Backcountry Skiing – An Analysis of Risk Factors

Skier-triggered avalanches are the main cause of avalanche accidents in backcountry skiing. The risk of accidents during backcountry skiing was analysed statistically and related to factors such as elevation level, aspect, stability rating and the time of the year. The analysis is based on a database about terrain usage and avalanche accidents from a large heli-skiing operator in Canada, which makes it possible to study the conditional probability of accidents given the recorded pattern of terrain usage. This study shows that the historical risk of accidentally triggering an avalanche greater than size 1 depends highly on the stability rating, with the highest risk occurring during “poor” stability. The risk is greater at high elevations, and it is lower during the late season than earlier on. Skier risk does not depend as much on aspect as may be indicated from avalanche data alone. However, it is relatively high in the N–NE–E sector. These factors are not independent of each other and therefore analyses of combined factors were also performed. Questionnaires and interviews were used to gain knowledge about the terrain selection of professional mountain guides. These results indicate that when selecting terrain, guides first look at the overall shape and size of the terrain, but avalanche history of terrain and inclination are also important factors. Finally, remarks in avalanche reports were analysed, and common human factors identified.     

Reliability Based Assessment of Shallow Foundations Using Mathcad

A reliability based method was used to design and analyse shallow foundations using first-order Taylor series approximation. The computer program Mathcad was used to facilitate all mathematical and computional efforts. This method is an effective tool to assist the foundation designers and analyists to investigate how reliable their designs or analyses are in relation to the ultimate bearing capacity of the foundations. The approach presented in this paper provides a reliable alternative for design and analysis of shallow foundations, rather than the conventional design methods, which employs the assumptions of a specified saftey factor. Several examples were presented for design and analysis of strip footings embedded in sandy soil, and rectangular and square footings analysis embedded in clayey soils. The program input and output of each example are also presented and discussed.     

Structure sismique du socle paléozoı̈que du bassin des Doukkala,Môle côtier,Maroc occidental. Indication en faveur de l'existence d'une phase éo-varisqueSeismic structure of the Doukkala basin,Palaeozoic basement,western Morocco: a hint for an Eovariscan fold-and-thrust belt

Seismic profiles and well data from the Doukkala basin unravel the structure of the Palaeozoic basement and suggest that this coastal zone of western Morocco was affected by a compressive phase during the Frasnian. This resulted in the formation of upright, plurikilometric folds associated with reverse faults (North Doukkala), and of asymmetrical folds associated with mostly west verging ramps (South Doukkala). Folding involved all pre-Upper Frasnian formations and caused partial or total hiatus of Upper Frasnian–Strunian strata. This event can be correlated with the orogenic phase reported from more internal domains of the Morocco Hercynian belt, where it is referred to as the ‘Bretonne’ or ‘Eovariscan’ phase. To cite this article: H. Echarfaoui et al., C. R. Geoscience 334 (2002) 13–20     

Statistical characteristics of chlorophyll-a concentration in Hong Kong′s coastal waters

In this paper seven of the ten Water Control Zones (WCZs) in Hong Kong′s coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors. Cluster analysis was employed to group the monitoring stations based on the structure of the data set. Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level. The results suggest that all the monitoring stations could be grouped into two clusters. Cluster I with frequent red tide incidents comprises two WCZs which aresemi-enclosed bays. Cluster II with less red tide occurrence comprises the other five WCZs in an estuarine environment in the west. For both clusters, the organic contents indicator, BOD5, was a common significant influencing factor of the chlorophyll-a level. Nitrogen and light penetration condition related to turbidity, total volatile solids and suspended solids had more influence on the cholophyll-a level in Cluster I than in Cluster II, while phosphorus and oceanographic conditions associated with salinity, temperature, dissolved oxygen and pH were more important in Cluster II than in Cluster 1. Generally, there was a higher average chlorophyll-a level in winter and autumn in a year.The chlorophyll-a level was much higher in Cluster I than in Cluster II among all seasons. Although the chlorophyll-a concentration had great variations from place to place in Hong Kong′s coastal waters, it seemed to have a common long term fluctuation period of 8-10 years with a high-low-high variation in the period in the whole region, which might be influenced by other factors of global scale.     

贾汪煤田为何未能向北东继续延伸

贾汪煤田的基本构造形态为贾汪向斜。通过对贾汪向斜北东延长段原地系统和外来系统的分析研究，认为在贾汪石炭——二叠纪煤田北界伏山前断裂的北东盘上，受构造应力的影响，奥陶系沿着其与寒武系界面间的软弱层被推覆，在原地代之以大面积分布的是青白口——震旦系及部分寒武系而非石炭——二叠系，从而造成了贾汪煤田没有向北东继续延伸。