The use of sorting curves in studying K2O alteration in interbedded greywacke and argillite

The chemical composition of unaltered greywacke-argillite sequences varies both abruptly and gradationally across short distances of a few centimeters to meters. These original variations are sufficient to mask changes in K₂O (and other oxides) resulting from hydrothermal alteration. Sorting curves for unaltered samples present K₂O contents in terms of two relatively immobile oxides SiO₂ and Al₂O₃. This allows an estimated of the original pre-alteration K₂O content of altered samples, from which gains and losses can then be calculated.     

Diurnal variation in net radiation depletion within a corn crop

The estimation of net radiation within a mature sweet corn canopy is examined using measurements of net radiation at one level above and three levels within the canopy during seven days in 1969. It is shown that Beer's Law, with a constant extinction coefficient, cannot be used to estimate hourly net radiation within the canopy. Functions of zenith angle and relative solar azimuth are incorporated into the model to account for the diurnal variation of optical density. These modifications, which are based on the characteristics of the crop, allow a constant extinction coefficient to be used to calculate hourly net radiation to an acceptable level of accuracy.     

Potential vorticity and the stirring of a rotating fluid

Summary The concept of potential vorticity is employed to demonstrate the quintessential interplay of an embient rotation with the forced or free stirring of a fluid.     

Landslide research in Kenya

As Kenya's population continues to increase and towns and villages steadily encroach onto steeper slopes and mountainsides, landslide hazards become an increasingly serious threat to life and property. However, there is still a dearth of information on several aspects of the landslide phenomenon and only recently has any serious consideration been given to the problem, including preventive and remedial measures. This review attempts to synthesise the information available to date and evaluate the status of landslide research in the country.     

Local and regional components of western Aegean deformation extracted from 100 years of geodetic displacement measurements

Our objectives are as follows. First, we wish to develop a methodology to recover the long-term component of deformation from any set of distributed, time-averaged geodetic strain measurements that were subject to seismic disturbance, given a catalogue of local seismicity that occurred during the measurement period. Second, using seismic and geodetic data sets that span approximately 100 years, we apply this technique in the western Aegean to assess the role of local seismicity in regional deformation. The methodology is developed using a model for crustal deformation constructed from a long-term, smooth regional strain field combined with instantaneous, local perturbations from upper-crustal earthquakes approximated by static elastic dislocations. By inverting geodetic displacements for the smooth field while simultaneously floating influential but uncertain earthquake source parameters, an estimate of the regional component of deformation that is approximately independent of the seismicity can be made. In the western Aegean we find that the horizontal component of regional deformation can be described with minor inaccuracy by a quadratic relative displacement field. The principal horizontal extensional axes calculated from the regionally smooth displacement field agree in orientation with the T-axes of earthquakes in the region. These observations indicate that the instantaneous elastic strain of the 10 km thick seismogenic layer is driven by a stress field that is smooth on the scale of the geodetic network as a whole, 200-300 km.     

Large scale isotopic Sr, Nd and O isotopic anatomy of altered oceanic crust: DSDP/ODP sites417/418

Large-scale compositional domains at DSDP/ODP drill sites 417A, 417D and 418A were analyzed for O, Sr and Nd isotope ratios, and REE, U, K, Rb and Sr abundances, to constrain the bulk chemical composition of the oceanic crust that is recycled at subduction zones. The combination of the three sites gives the composition of the upper oceanic crust in this region over a distance of about 8 km. The δ¹⁸O_SMOW and⁸⁷Sr/⁸⁶Sr_meas of compositional domains 10–100 m in size correlate well, with a range of 7.7–19.2 and 0.70364–0.70744, and mean of 9.96 and 0.70475, respectively. The Rb inventory of the upper crust increases by about an order of magnitude, while Sr contents remain constant. U abundances increase moderately under oxidizing alteration conditions and nearly triple in the commonly reducing alteration environments of the upper oceanic crust. REEs are influenced by alteration only to a small extent, and recycled oceanic crust is similar to MORB with respect to¹⁴³Nd/¹⁴⁴Nd. Even though the average composition of the upper oceanic crust is well defined, the large scale composition varies widely. Highly altered compositional domains may not have a large impact on the average composition of the oceanic crust, but they may preferentially contribute to fluids or partial melts derived from the crust by prograde metamorphic reactions.     

Sustainability,development and rural aboriginal communities

Aborigines, because of their population numbers and increasing control over land and resources, are crucial to the sustainable development of rural Australia. However, appropriate Aboriginal development requires the replacement of the ‘top‐down’ approaches generally adopted by government agencies by ‘bottom‐up’ approaches reflecting the needs and aspirations of rural Aboriginal people. Past experience demonstrates that Aborigines have faced many frustrations in reconciling these concepts. But some approaches now being adopted in the use and management of Australia's rangelands provide interesting alternatives which may be more generally applicable in enhancing rangeland sustainability. Examples include land‐use practices conducted by Aborigines living in remote homeland centres on their own freehold land, and the diversity of land uses introduced on pastoral stations now under Aboriginal ownership. Broader recognition of the value of these approaches will depend on widespread acknowledgment of the overall worth of Aboriginal land management knowledge in rural restructuring     

Desertification: or perhaps not? White Nile,Sudan, 1980–92

The White Nile area of the Sudan has undergone significant socio-economic change during the 1980s as demonstrated by surveys carried out near Ed Dueim in 1980 and 1992. At first sight these changes appear to be linked directly with the reduction in average annual rainfall. This paper demonstrates that, though important, this factor is not the sole, and may not even be the main factor involved. Government investment policy and associated population movements are shown to have great significance, and cast doubt on any belief that a return to higher rainfall levels would reverse the current socio-economic processes.     

Cultures under pressure in the Sudan: the Ingessana and the Uduk

The paper examines the pressures being exerted by cultural and economic processes upon African cultures in the intermediate zone of the Sudan. It examines in particular the experience of the Ingessana and Uduk peoples living between the White and Blue Niles. The Uduk have experienced the greater degree of disruption from Sudan's civil war, and many Uduk have sought refuge in Ethiopia. The Ingessana are in the frontline facing cultural and economic pressures from the north. To pressures for Islamisation and Arabicisation have been added the development of chromite mining, mechanised agriculture and increased nomadic activity around their hills.The paper points out the advantages of cultural adaptation and survival, rather than acculturation, to both these peoples and the Sudan and concludes that the Ingessana seem particularly likely to adapt and survive as a cultural entity.