Alpha Ridge and iceland-products of the same plume?

Refraction results from the 1983 Canadian Expedition to Study the Alpha Ridge suggest a crustal model with many similarities to the region of Iceland. The overall character of the seismic sections, the derived velocity structure, the lateral dimensions of crustal transition zones and the general crustal thicknesses are comparable from the Arctic and Atlantic regions. Additional similarities are noted in the alkalic basalts, the subaerial to subaqueous, within-plate volcanic environment and the positive regional magnetic responses at satellite altitudes.Based on the geophysical semblances and the apparent evolutionary sequence of within-plate volcanism and tectonic events extending from the northern Ellesmere-Greenland area to Iceland, it is proposed that the Alpha Ridge and Iceland may have been affected by the same mantle plume.     

川滇及其邻区强震连续活动的地域图象研究

侧重分析了川滇及共邻区强度连续活动的不同地域分布图象，根据强震间的构造成因联系，将它们分为两种类型，主震－晚期强震和先期强震－后期强震。后一类又可分为两个亚类，由前兆性中强震条带联系的先、后期强震和相关构造带联系的先、后期强震。从整体连续强震活动图象变化特征上反映出强震及其晚期强震活动的可预测性，因而可供强震中期预报参数。     

Channel bed steps and pool shapes along Soda Creek, Three Sisters Wilderness, Oregon

Field study of bedrock step–pool systems along the upper reaches of Soda Creek in the Three Sisters Wilderness of Oregon shows strong correlation between several form variables (shape) and channel slope. Although step height and step length showed no regular spacing and variable correlation with channel slope, length to height ratios demonstrated strong negative correlations: steep slopes (20% to 80%) featured greater step height and shorter pool lengths than did flatter channel slopes. Correlations between step height to length ratios and channel slope varied between three lithologies. Explained variations ranged from 0.984 for the oldest channel steps developed in basalt, to 0.982 for steps of intermediate age developed in andesite, to 0.964 for the youngest steps developed in dacite. Sample size was 57, 40, and 33, respectively. The frequency of pool shape classes did not vary by lithology, but specific shape classes developed under differing slope conditions by rock type. All pool classes have adjusted (developed) their form to maximize resistance to flow H/L/S, and they have done so in remarkably uniform fashion.     

In situ chemisorption of radiocesium from seawater

A novel approach to in situ extraction of Cs radionuclides from seawater is described which offers many advantages over previous methods. Cesium (stable and radioactive) is partially stripped from seawater as it passes in series through a tandem cartridge consisting of twin beds of ion exchange resin impregnated with cupric ferrocyanide. It is demonstrated that, when seawater passes through this cartridge at a constant flow-rate, collection efficiencies of each bed are the same, allowing the calculation of the seawater Cs nuclide concentration. The cartridge is made of inexpensive, readily available, PVC pipe fittings and is easily deployed under various field conditions. Procedures are described for resin preparation and desorption and radiochemical purification of the collected Cs. Thousands of liters of seawater can be stripped of Cs in this way, permitting substantial improvement in the sensitivity of measurement of ¹³⁴Cs and ¹³⁷Cs.     

Vertical migration and mortality of benthos in dredged material—part I: Mollusca

Benthic invertebrates have many characteristics which make them prime candidates for burial studies in dredged material. A major concern in dredging and disposal projects is the effect of burial on the survival of benthic invertebrates. The purpose of the research reported in this paper was to determine the ability of estuarine benthos—in particular three species of molluscs (Mercenaria mercenaria, Nucula proxima and Ilyanassa obsoleta)—to migrate vertically in natural and exotic sediments and to determine the survival of benthos when exposed to particular amounts of simulated dredged material.Mortalities generally increased with increased sediment depth, with increased burial time and with overlying sediments whose particle size distribution differed from that of the species native sediment. Temperature affected mortalities and vertical migration. It was concluded that vertical migration is a viable process which can significantly affect rehabilitation of a dredged disposal area. Under certain conditions, vertical migration should be considered, together with larval settling and immigration from outside impacted areas, as a mechanism of recruiting a dredgedump site.