Extension tectonics in the Afar Triangle

On the Red Sea coast of Africa, the triangular wedge of land named after its Afar people has been created by excess basalt production at a triple junction of divergent plate boundaries. Its harsh desert terrain is a remote wilderness that receives few visitors, yet is a spectacular suite of extension tectonics dominated by sinking grabens, salt basins below sea level, active faults and effusive volcanoes.     

An improved Ewing heat probe frame

The standard Ewing heat probe frame has been improved through the design of a new takedown model whose parts are held together by lynch pins. When a 600 lb (272 kg) unit of this type is taken apart, the heaviest single piece of the dismantled unit weighs only 75 lb (34 kg).This makes it feasible for one person to handle, transport, and assemble the new unit. A central, main support member of a heat probe using this frame can be suspended over the side of a research vessel while the heavier temperature recorder and ballast weights are attached by means of the quickaction lynch pins. This makes it possible to use this device on relatively small vessels which are not designed for coring work, having a minimum of free deck space and without launching platforms or hydraulic A-frame booms.     

Mineralogical and geochemical compositions of modern bivalve shells from the Mediterranean coast of Egypt

The stable isotopic composition (¹³C and ¹⁸O) and elemental (Sr and Mg) of marine molluscs are presented for Carditacea and Solenacea shells collected off the Mediterranean coast of Egypt. Based on shell microstructures and mineralogy, the bivalve shells are preserved in their original mineralogy and chemistry.The Sr and Mg concentrations of the bivalve shells have mean values of 1960 ppm and 226 ppm respectively. The stable isotopic composition generally show high values of ¹⁸O and ¹³C. The ¹⁸O values range from +0.1 to –1.8 PDB and most shells are highly enriched in¹³C; averaging +2.5 PDB. These elemental and isotopic signatures are analogous to modern marine bivalves from other localities.The oxygen and carbon isotopes, together with the calculated temperatures, suggest that the aragonitic bivalve shells were precipitated in isotopic equilibrium from warm marine waters.     

The role of moisture cycling in the weathering of a quartz chlorite schist in a tropical environment: findings of a laboratory simulation

Long‐term weathering of a quartz chlorite schist via wetting and drying was studied under a simulated tropical climate. Cubic rock samples (15 mm × 15 mm × 15 mm) were cut from larger rocks and subjected to time‐compressed climatic conditions simulating the tropical wet season climate at the Ranger Uranium Mine in the Northern Territory, Australia. Fragmentation, moisture content and moisture uptake rate were monitored over 5000 cycles of wetting and drying. To determine the impact of climatic variables, five climatic regimes were simulated, varying water application, temperature and drying. One of the climatic regimes reproduced observed temperature and moisture variability at the Ranger Uranium Mine, but over a compressed time scale. It is shown that wetting and drying is capable of weathering quartz chlorite schist with changes expected over a real time period of decades. While wetting and drying alone does produce changes to rock morphology, the incorporation of temperature variation further enhances weathering rates. Although little fragmentation occurred in experiments, significant changes to internal pore structure were observed, which could potentially enhance other weathering mechanisms. Moisture variability is shown to lead to higher weathering rates than are observed when samples are subjected only to leaching. Finally, experiments were conducted on two rock samples from the same source having only subtle differences in mineralogy. The samples exhibited quite different weathering rates leading to the conclusion that our knowledge of the role of rock type and composition in weathering is insufficient for the accurate determination of weathering rates. Copyright © 2005 John Wiley & Sons, Ltd.     

New developments in water efficiency

1Water LossInitiativesUnaccounted-for water(or unbilled water)has beenreceiving newscrutiny at both the state and nationallevels.For years,water conservationeffortsin Europehave emphasized reduction in water loss to a muchgreater extent thaninthe United S…