The autonomous underwater glider "Spray"

A small (50-kg, 2-m long) underwater vehicle with operating speeds of 20-30 cm/s and ranges up to 6000 km has been developed and field tested. The vehicle is essentially an autonomous profiling float that uses a buoyancy engine to cycle vertically and wings to glide horizontally while moving up and down. Operational control and data relay is provided by GPS navigation and two-way communication through ORBCOMM low-Earth-orbit satellites. Missions are envisioned with profile measurements repeated at a station or spaced along a transect. The initial instrument complement of temperature, conductivity, and pressure sensors was used to observe internal waves and tides in the Monterey underwater canyon     

Tectonics at the intersection of the East Pacific Rise with Tamayo Transform fault

During the Fall of 1979, a manned submersible program, utilizing DSRV ALVIN, was carried out at the intersection of the East Pacific Rise (EPR) with the Tamayo Transform boundary. A total of seven dives were completed in the vicinity of the EPR/Tamayo intersection depression and documented the geologic relationships that characterize the juxtaposition of these types of plate boundaries. The young volcanic terrain of the EPR axis can be traced into and across the Tamayo Transform valley but becomes buried by sedimentary talus that is being shed from sediment scarps along the unstable sediment slope that defines the north side of the intersection depression. Within 4 km of the transform boundary, the dominant trend (000°) of the fissures and faults that disrupt the rise-generated volcanics is markedly oblique to the regional direction of sea floor spreading (120°). Since no evidence was found to suggest that these structures accommodate significant amounts of strike-slip displacement, they are taken to reflect a distortion of the EPR extensional tectonic regime by a transform generated shear couple. The floor of the Tamayo Transform valley in this area is inundated by mass-wasted sediment, and the principal transform displacement zone is characterized at the surface by a narrow (<1.5 km) interval of fault scarps in sediment that trends parallel with the transform valley. Extrapolated to the west, this zone links with zones of transform deformation investigated during earlier submersible studies (CYAMEX and Pastouret, 1981). Evidence of low-level hydrothermal discharge was seen at one locality on the EPR axis and at another 8 km west of the axis at the edge of the zone of transform deformation.     

A hydrodynamic model of a submerged lenticular wave energy device

The wavemaking capability and energy absorbing characteristics of a single submerged body, constrained to move horizontally in a surge mode, are examined. The body possesses both a vertical axis of symmetry and a horizontal plane of symmetry and is ‘thin’ in the sense that the body draft is small compared to the length. The behaviour of a single body subject to a constraint being placed upon the amplitude of its displacement and the properties of an array of interacting identical devices are also discussed.     

Comparison of three oxidation methods used for the analysis of the dissolved organic carbon in seawater

Three methods for the determination of dissolved organic carbon in seawater were compared. Samples were analysed using persulphate oxidation, high-temperature combustion, and ultraviolet photo-oxidation. The dissolved organic carbon content of the seawater samples ranged from 0.6 to 1.6 mg C/I. This study shows that results of high-temperature oxidation and photo-oxidation procedures differ by less than 5%, whereas results with persulphate oxidation are about 15% less than those obtained with the high-temperature oxidation. The relative merits of each of the oxidation techniques for the determination of organic matter in seawater are discussed.     

Dispersal patterns of clay minerals in the sediments of the eastern Mediterranean Sea

A semiquantitative X-ray diffraction study of the finer-than-2μ-size fraction of the surface sediments of the eastern Mediterranean Sea has been carried out. On the basis of the abundances and the distributional patterns of the different clay minerals six mineral assemblages are distinguished. These assemblages have distinctive sources and their dispersal reflects different agents of transport in the eastern Mediterranean Sea.     

Bifurcating and wandering ocean ridges: A progress report

First conclusions of a study of the fault pattern in the North Atlantic ocean are briefly outlined. Correlation of fracture zones in deep ocean basins, even over short distances (30 miles) is difficult when using only topographic and seismic profiler data, and requires the additional criterion that the magnetic pattern is shifted along the fracture zones. This implies that each track must be paralleled by at least one more track at close distance to detect breaks in the magnetic pattern.Transform faults are regarded as complementary to the median rift, which, as a tension fault, should be normal to the direction of maximum strain according to laboratory experiments by Gramberg. Median rift segments and transform faults together form an orthogonal system approximating an originally irregular but continuous fissure.Mantle convection currents are thought to be the agents of continental drift. In view of the dimensions of convection cells, a direct coupling between ridges (or ridge segments) and the upwelling branch of a convection current seems impossible. Thus the known bifurcations of mid-ocean ridges in the Indian and in the Pacific Ocean may be interpreted as the result of a divergence of the horizontal branch of a convection cell or a divergence of the movements of crustal plates through collision of continents. Secondary fissures would lead to the development of secondary ridges that cannot be distinguished from primary ridges. In this concept mid-ocean ridges can partake in the horizontal movement by asymmetrical spreading. This might explain the disappearance of the East Pacific Rise under the North American continent.The resulting convection current system is simple: one upwelling and one downgoing current as two complementary helices winding round the earth. Ways are indicated to check several aspects of the proposed hypotheses.     

Plate boundaries and evolution of the Solomon Sea region

The Solomon Sea Plate was widely developed during late Oligocene, separating the proto-West Melanesian Arc from the proto-Trobriand Arc. Spreading in the Bismarck Sea and in the Woodlark Basin resulted from interaction between the Pacific and Australian Plates, specifically from the collision of the proto-West Melanesian Arc with north New Guinea, which occurred after arc reversal. This model explains the extensive Miocene, Pliocene, and Quaternary volcanism of the Papua New Guinea mainland as it related to southward subduction of the Trobriand Trough. Our interpreted plate motions are concordant with the geological evidence onshore and also with complex tectonic features in the Solomon Sea Basin Region.     

Benthic Metabolism and Standing Stock in the Central and Northern Deep Red Sea

Abstract. Benthic metabolism and standing stocks were investigated in the deep Red Sea between 21^o and 27^oN, Activity was assessed by the determination of respiration rates with a shipboard method and by calculating oxygen consumption from the activity in the electron transport system. We attempted to compare results from different latitudes within the warm Red Sea and with data from cold Atlantic environments. Our investigations were part of an environmental risk assessment to evaluate future mining of metalliferous sediments from the Atlantis II Deep.