Geomorphology, Stratigraphy, and Radiocarbon Chronology of LlanquihueDrift in the Area of the Southern Lake District, Seno Reloncaví, and Isla Grande de Chiloé, Chile

Glacial geomorphologic features composed of (or cut into) Llanquihue drift delineate former Andean piedmont glaciers in the region of the southern Chilean Lake District, Seno Reloncav', Golfo de Ancud, and northern Golfo Corcovado during the last glaciation. These landforms include extensive moraine belts, main and subsidiary outwash plains, kame terraces, and meltwater spillways. Numerous radiocarbon dates document Andean ice advances into the moraine belts during the last glacial maximum (LGM) at 29,363–29,385 ¹⁴C yr BP , 26,797 ¹⁴C yr BP , 22,295–22,570 ¹⁴C yr BP , and 14,805–14,869 ¹⁴C yr BP . Advances may also have culminated at close to 21,000 ¹⁴C yr BP , shortly before 17,800 ¹⁴C yr BP , and shortly before 15,730 ¹⁴C yr BP . The maximum at 22,295–22,567 ¹⁴C yr BP was probably the most extensive of the LGM in the northern part of the field area, whereas that at 14,805–14,869 ¹⁴C yr BP was the most extensive in the southern part. Snowline depression during these maxima was about 1000 m. Andean piedmont glaciers did not advance into the outer Llanquihue moraine belts during the portion of middle Llanquihue time between 29,385 ¹⁴C yr BP and more than 39,660 ¹⁴C yr BP . In the southern part of the field area, the Golfo de Ancud lobe, as well as the Golfo Corcovado lobe, achieved a maximum at the outermost Llanquihue moraine prior to 49,892 ¹⁴C yr BP . Pollen analysis of the Taiquemmire, which is located on this moraine, suggests that the old Llanquihue advance probably corresponds to the time of marine isotope stage 4. The implication is that the Andean snowline was then depressed as much as during the LGM. A Llanquihue-age glacier expansion into the outer moraine belts also occurred more than about 40,000 ¹⁴C yr BP for the Lago Llanquihue piedmont glacier.     

A comparison of archaeointensity results from Chinese ceramics using microwave and conventional Thellier's and Shaw's methods

Palaeo- and archaeointensity determinations of the geomagnetic field are limited by mineralogical alteration that may occur when samples are heated in the laboratory to produce a TRM ( Thellier & Thellier 1959 ; Shaw 1974 ). By using microwave excitation of the magnetic grains we have been able to create a TRM without significantly heating the bulk samples, thereby avoiding thermal alteration ( Walton et al . 1993 ; Shaw et al . 1996 ). When applied to Peruvian ceramics in a manner analogous to the standard Thellier method, the microwave technique was found to reduce the scatter dramatically in the archaeointensity results ( Shaw et al . 1996 ). In the present study we apply this microwave technique to a collection of Chinese ceramics covering the time interval 2700–7500  yr BP. These ceramics have already been investigated using adaptations of both Thellier's ( Coe 1967 ) and Shaw's ( Rolph & Shaw 1985 ) palaeointensity methods ( Yang et al . 1993a ). Although an acceptable agreement was found between those two methods, the equivalent virtual axial dipole moments (VADMs) were significantly lower than for the global model of McElhinny & Senanayake (1982 ). The present study, using the microwave technique with cooling-rate correction, has provided more consistent VADMs, and is much closer to the global model.     

On the move: explaining migration patterns in Estonia during the transition period

This paper attempts to explore the migration patterns during the transition period in Estonia. A structuration approach was used to analyze data from the Estonian Statistical Office collected in 1997. Findings show that for migration between urban and rural areas, work-related reasons have been the most important motivating factor in urban growth during the transition period. Also considered are the family and education. In relation to sociodemographic structure of the population, men cite work, while women count family-related reasons, as the main motive for migrating. As to nonregistration, the most significant reason relates to issues of ownership. Because migrants are living in rented housing, it is not possible for them to register even if they desire to do so. Other reasons include "temporary", associated with study and work; "juridical", bureaucratic matters; and "multiple places of residence". This analysis, however, is incomplete because the attitudes and patterns of behavior have only partially or perfunctorily been related to the dramatic changes that have occurred in Estonian society. Proper statistical data are needed to help examine trends at a more disaggregated spatial level.     

Integrating GB and US census microdata for studying the impact of family migration on partnered women's labour market status

This paper investigates the problems in integrating different data sets for social science research. A cross-national analysis of the effects of family migration on labor market participation rates for female partners was used as an example to concretize these problems. The data used in the cross national analysis came from the 1991 British Census Sample of Anonymised Records and the 1990 United States Public Use Microdata Sample. The problems addressed were the following: data collection; manipulation and reliability; question type and definition; and measurement of individual and family variables. As part of the analysis, some empirical findings were also presented. Significant overall differences between the US and Great Britain (GB) samples were observed, particularly concerning graduate qualifications, marital and employment status, and ethnic group. There were higher numbers of married partners and full-time workers in the US sample, while female partners undertaking part-time employment were greater in GB. Furthermore, the US sample had more couples with a female graduate as compared with the GB sample who had a higher proportion of nongraduate couples. Finally, this paper recognized the importance of cross- national research in the evaluation of national ideological and institutional structures.     

PHYSICAL GEOGRAPHY IN SOUTHEAST ASIA: PAST THEMES, CURRENT STATUS AND FUTURE TRENDS

Our knowledge regarding the physical geography of Southeast Asia is incomplete to a surprising extent. This paper reviews the past research, describes the ongoing work, and attempts to identify the future trends. Coverage of such a large area, even for the last 25 years, requires study of publications in several languages and coping with literature which is not easily available. Therefore certain topics. which are prominent in current research and likely to remain so in the future were chosen and reviewed in detail. Such topics include studies related to active plate margin features; the Pleistocene in Southeast Asia; erosion and sedimentation rates; rainforest; river systems; karst in Southeast Asia; coastal geomorphology; and the urban environment. Environmental studies are rapidly gaining importance chiefly because of (a) the destruction of the natural vegetation and the associated loss of biodiversity and (b) the growing problems due to accelerated erosion and sedimentation This trend is likely to continue with accelerated destruction of forests, development of coastal areas, and urbanization of the landscape The direction of research in physical geography of Southeast Asia has been determined by a combination of individual research interest, governmental priorities, and international expectations     

Crustal structure beneath exposed accreted terranes of Southern Alaska

Summary. The crustal structure beneath the exposed terranes of southern Alaska has been explored using coincident seismic refraction and reflection profiling. A wide-angle reflector at 8–9 km depth, at the base of an inferred low-velocity zone, underlies the Peninsular and Chugach terranes, appears to truncate their boundary, and may represent a horizontal decollement beneath the terranes. The crust beneath the Chugach terrane is characterized by a series of north-dipping paired layers having low and high velocities that may represent subducted slices of oceanic crust and mantle. This layered series may continue northward under the Peninsular terrane. Earthquake locations in the Wrangell Benioff zone indicate that at least the upper two low-high velocity layer pairs are tectonically inactive and that they appear to have been accreted to the base of the continental crust. The refraction data suggest that the Contact fault between two similar terranes, the Chugach and Prince William terranes, is a deeply penetrating feature that separates lower crust (deeper than 10 km) with paired dipping reflectors, from crust without such reflectors.     

Radiation from an impulsive line source in an unbounded homogeneous anisotropic medium

Summary. The space-time elastic wave motion generated by an impulsive line source in a homogeneous anisotropic medium is calculated with the aid of the Cagniard-de Hoop method. Two types of sources are considered in detail, viz. a line source of expansion (model for an explosive source) and a line force (model for a mechanical vibrator). Numerical results are presented for the radiated particle velocity in the medium including those regions of space where shear-wave triplication occurs. There is a marked difference in the time response observed for the two types of sources and for the different positions of the receiver with respect to the source position. These waveform differences are important when the radiated wave is used to determine experimentally the elastic properties of the medium. As compared with the traditional Fourier-integral transform method to handle this problem, the computation time with the present method is considerably less.     

Black–White and Hispanic–White Segregation in U.S. Counties

Residential segregation in metropolitan areas has been the subject of much research, but this article analyzes patterns of white–black and white–Hispanic segregation in counties across the United States. Our purpose was to understand county variations in this one dimension of inequality. Conceiving of segregation as relative inequality of access to neighborhood resources, we measured segregation in 2000 by the index of dissimilarity (D) calculated by blocks, mapped the index values, and correlated them with census variables. Three filters enabled us to eliminate counties with characteristics that could have corrupted the analyses, leaving us with more than 1,000 counties in each analysis. Both minority groups were less segregated from whites in the West and South and in metropolitan counties. Lower segregation was strongly associated with higher minority socioeconomic status and higher percentages of minorities living in housing built in the 1990s, and Hispanic–white segregation was lower where more Hispanics were U.S.-born or English proficient. The racial threat hypothesis was supported only weakly and inconsistently. Mapping made it possible to identify regional and local patterns of high and low segregation as well as the lower segregation of suburban counties in some large metropolitan areas.     

Divergent Perspectives on Water Security: Bridging the Policy Debate

Environmental policy discussion is replete with references to water security, food security, ecosystem health, community resilience, sustainable development, and sustainable urbanism. These terms are, by their very nature, ambiguous and difficult to define; they allow room, however, for a variety of actors to conceptualize water, food, ecological, economic, and urban problems in ways that allow them to move forward on contentious issues. This article focuses on the idea of water security and asks how it is conceptualized and used for regional policy debate in western Canada. We asked fifty-eight water stakeholders from the Saskatchewan River Basin to define water security, identify major barriers to security, and prioritize water problems. Responses showed there are myriad ways to think about water security, ranging from narrow conceptualizations, such as reliability, quality, and quantity, to broader sustainability perspectives about the nature of resource development and its social and economic consequences. The human dimensions of water security (governance, land use, and competing demands) were assigned higher priority than its biophysical aspects (flooding, droughts, and climate change). Framing water security to emphasize the human capacity to manage uncertain and rapid biophysical and societal change offers the opportunity to unite actors who otherwise would be separated by core environmental values, definitions of water security, provincial context (Alberta vs. Saskatchewan), and occupation.