ALBERT

Description: Santorini, Greece is a major explosive volcano. The Santorini volcanic complex is composed of two active volcanoes—Nea Kameni and Mt. Columbo. Holocene eruptions have generated a variety of processes and deposits and eruption mechanisms pose significant hazards of various types. It has been recognized that, for major European volcanoes, few studies have focused on the social aspects of volcanic activity and little work has been conducted on public perceptions of hazard, risk and vulnerability. Such assessments are an important element of establishing public education programmes and developing volcano disaster management plans. We investigate perceptions of volcanic hazards on Santorini. We find that most residents know that Nea Kameni is active, but only 60% know that Mt. Columbo is active. Forty percent of residents fear that negative impacts on tourism will have the greatest effect on their community. In the event of an eruption, 43% of residents would try to evacuate the island by plane/ferry. Residents aged N50 have retained a memory of the effects of the last eruption at the island, whereas younger residents have no such knowledge. We find that dignitaries and municipal officers (those responsible for planning and managing disaster response) are informed about the history, hazards and effects of the volcanoes. However, there is no bemergency planQ for the island and there is confusion between various departments (Civil Defense, Fire, Police, etc.) about the emergency decision-making process. The resident population of Santorini is at high risk from the hazards associated with a future eruption.

Description: High concentrations of free C32 bis-homohopanoic acids (up to 433 μg/g dry wt) occur in microbial mats at methane seeps in anoxic Black Sea waters. These compounds show a strong preference for the ‘geological’ 17α(H),21β(H)- over the ‘biological’ 17β(H),21β(H)-configuration (αβ/ββ ratios up to 30.7) and indicate the potential formation of αβ-hopanoids in modern environments. Strong 13C-depletions (δ13C as low as −78.4‰ PDB) indicate an in situ generation of these hopanoids by biota involved in the anaerobic cycling of methane carbon. The inferred presence of hopanoids indigenous to a permanently anoxic marine environment is significant because these lipids are not known to occur in strictly anaerobic bacteria.

Description: Late glacial to post glacial sea-level changes provide direct evidence of the progress of melting of large ice sheets during the last deglaciation but, although the correlation between ice and ocean volumes is incontrovertible, the causal link is commonly obscured. Local effects including tectonics, isostatic and hydroisostatic responses and equatorial ocean-syphoning impose additional signals that hide the true picture. A detailed regional study of the Western Indian Ocean based on the analysis of drill cores carried out through modern reefs, in combination with observations and sampling of reef foreslopes, and investigations of outcrops provides a comprehensive data base. Sites from a range of tectonic settings include the microcontinental margins of Madagascar, the granitic Seychelles, and the isolated volcanic islands of Réunion, Mauritius and the Comoros in which the effects of subsidence can be shown to be small. These cover a range of latitudes, and comparisons with adjacent sites on continental margins allow the construction of sea-level curves that closely reflect the eustatic response and disengage this from the effects of other mechanisms. The Mayotte foreslope in the Comoro Islands provides the first coral reef record of sea-level change during the early deglaciation in the Indian Ocean (110–115 m below present sea level between 18,000 and 17,000 yr BP). Two distinctive reef terraces, at 90 and 60 m water depth are dated at 13,600 yr BP and partly attributed to the Younger Dryas period (12,700–11,600 cal yr BP). Reef drowning at around 13,500 yr BP may correspond to Meltwater Pulse 1A, and although there were surges in the rate of sea-level rise, most notably between 11,950 and 11,350 yr BP, there is little evidence to support a well-defined Meltwater Pulse 1B. Reconstructed Holocene sea-level curves are in good agreement and reflect a rapid sea-level rise of about 6 mm yr−1 between 10,000 and 7500 yr BP, followed by a clear inflection around 7500 yr BP when the rate fell to 1.1 mm yr−1. Modern reefs started to grow 8000–9000 years ago. In the post-glacial period the rate of sea-level rise was 1–1.5 mm yr−1 before stabilization at its present level 3000–2500 years ago. Curves for the 10,000–6000 yr−1 BP interval correspond closely with those predicted by theoretical models but lie below these in the subsequent period. In particular, and with the exception of the margins of the Madagascar microcontinent influenced by hydroisostatic processes, they do not reflect predicted higher sea-level stands during the late Holocene.

Description: The 14C-dating of microbial carbonate structures growing at methane seeps in anoxic waters of the Black Sea has shown a gradual increase with depth of the age of carbonates of these buildups. Comparing the radiocarbon age of the base and middle parts of the microbial structures gives an approximate time of origin of the deepest and shallowest microbial buildups as about 5300 and 2900 years before present, respectively. These dates correspond to the first appearance of hydrogen sulfide in the deepest Black Sea waters and to the stabilization of the upper boundary of the anoxic zone around the present-day level.

Description: Understanding how complex, highly variable sedimentary systems interact in time and space to release, transport and concentrate diamonds is the basis for successful exploration strategies for placer diamond deposits. De Beers’ and Namdeb's West Coast operations are widely involved in a variety of applied scientific research to unravel the complex interactions of Cainozoic fluvial, marine and aeolian systems that have contributed to the formation of the most spectacular gem diamond placer in the world. Geological models produced not only provide the basis for exploration target selection but also high-resolution orebody characterisation, a prerequisite for high confidence geostatistical evaluation, mining system design and mine planning. This paper draws on some of the many applied research projects that have contributed to De Beers’ and Namdeb's placer exploration success that continues to deliver new mineral resources on the West Coast. The history of the Orange River has, and continues to be intensively studied both on- and offshore as the principal conduit for diamond introduction to the continental margin. Use of the “Jago” submersible has introduced a new dimension to offshore sedimentological studies on the continental shelf through direct seafloor observation, which helped us to identify the latest deep-water offshore development—the late Pliocene/early Pleistocene Orange River fan-delta.

Description: Two modes of decrease in load bearing capacity of granular materials are discussed in view of experimental results. Both relate to the fact that frictional materials exhibit nonassociated plastic flow and they undergo considerable volume changes, either contraction or dilation. One mode consists of the instability that may occur in certain regions of stress space and potentially result in liquefaction of the granular material. It is the fact that loading of contracting soil (resulting in large plastic strains) can occur under decreasing stresses that may lead to unstable behavior under undrained conditions. As long as the soil remains drained, it will remain stable in the region of potential instability. The other mode is initiated by localization of plastic strains and subsequent development of shear bands, which in granular materials is followed by a decrease in load bearing capacity. These two modes are mutually exclusive and they occur for different loading and material conditions as discussed here on the basis of experimental observations.

Description: Alkaline volcanic rocks including nephelinites, basanites and trachybasalts dredged from the volcanic pedestal of Rakahanga Atoll and from a volcanic edifice with 100 satellite volcanoes at the eastern edge of the Manihiki Plateau, ca. 40 km southwest of the atoll, fall well within the category of EM-type ocean island basalts. They indicate a hotspot involvement during the formation of the plateau basement. The rocks are thought to be products of explosive eruptions which took place subaerially or in shallow water in the Aptian. The volcanoes, together with other volcanic eruption centers, most likely were responsible for the formation of the 230 m thick volcaniclastite layer which rests on the basement for at least 5000 km2 of the eastern part of the Manihiki Plateau. Erosion has prevented any substantial sediment cover on the volcanic cone field and most of the slope of Rakahanga and thin pelagic limestones were deposited instead at least since the Maastrichtian.

Description: Analysis of 12,000 electronic still camera images collected with the ARGO II vehicle near the Trans-Atlantic Geotraverse (TAG) active hydrothermal mound, 26°N on the Mid-Atlantic Ridge, has made possible the first quantitative in situ assessment of both fissure orientation and width within the median valley of a slow-spreading ridge. Fissures near the TAG mound are partially rubble-filled extensional fractures that cut lightly sedimented seafloor and in ∼1% of our observations host pillow lavas. Fissure widths range from 0.15 to 3.5 m, with a mean of 0.7 m, and do not vary systematically within the survey area. First-order estimates of crack depth, based on these width measurements and reasonable elastic moduli, indicate that fissures are restricted to depths 〈500 m, with a mean depth of ∼70 m. Fissure-associated eruptives were therefore probably fed by shallow propagating dikes. TAG fissures exhibit a wide range of orientations, with ∼40% deviating by 〉45° from the strike of the ridge axis. The formation of obliquely oriented fissures requires that the local least compressive stress direction varies (at least temporarily) from that predicted by the regional tectonic stress field associated with plate separation. This stress field reorientation may be facilitated by variations in the style of magma emplacement within the rift. The close spatial association of long-term hydrothermal activity, fissure-hosted lava flows, and faults and fissures trending oblique to the spreading axis suggests a causal relationship between the impact of dike intrusion and the maintenance of localized hydrothermal flow.

Description: Detrital sediment is carried from land to the sea by three agents, rivers, glaciers, and winds. The shoreline is an arbitrary boundary within the detrital sediment transport system, which extends from a site of origin across areas of temporary storage to a site of long-term deposition. The most important of the agents moving sediment across the land is river transport, estimated to be in the order of 20×1012 kg of sediment annually at present. Analysis of drainage basins indicates that relief and runoff are the most important factors in determining the sediment load of rivers. The competence of rivers to transport sediment is governed by the volume flow, gradient, and the sediment load itself. Today, most large rivers are fed by snowmelt in highland areas, runoff from rainfall in the drainage basin, and groundwater inflow. Along the river course, water is lost to evaporation and groundwater infiltration. River courses can often be divided into two segments, a degradational section in which the gradient is relatively steep and little temporary storage of sediment takes place, and an aggradational section where the gradient is sharply reduced through meandering, and where large-scale temporary sediment storage forms a flood plain. Lakes trap sediment inland and prevent its transport to the sea. Today, many high and mid-latitude rivers are interrupted by lakes of glacial origin. There are also some large areas of internal drainage that deliver no sediment to the sea. The load carried by rivers has been markedly altered by human activity, and may have doubled over the past few thousand years, only to be reduced in the past century by the widespread construction of dams. The ancient use of fire in hunting and its subsequent use in clearing land has increased erosion. Extensive deforestation and cultivation processes have also increased the sediment supply. Dam construction is a relatively new factor and affects the sediment transport system by trapping sediment before it can reach the sea. The resulting lower sediment supply from rivers is, at least in part, compensated by increased coastal erosion. Glacial erosion is difficult to estimate. There is an ongoing controversy whether ice sheets are effective erosive agents or not. Estimates of the present global flux of glacial detritus range from 0.8–50×1012 kg annually, with the lower value most probable. The dust flux is in the order of 0.5 to 0.9×1012 kg annually, but may vary greatly with time.

Description: This chapter discusses the rates of protein synthesis in fish. Protein synthesis can be viewed at a number of levels. Whole-animal values can be integrated into the descriptions of assimilation/growth or assimilation/metabolism patterns in different fish species and is the focus of the chapter. The measurement of protein synthesis rates in body organs and tissues can provide information on the extent to which differences exist among various tissues and offer a challenge in understanding the integration of organ metabolism into whole animal physiology. The majority of methods for estimating protein synthesis measure the flux of an amino acid or nitrogen. This involves the use of tracer substances—that is, amino acids labeled with an isotope, which are given in a single dose or by continuous infusion. The measurements, parameters, and formulae that are commonly employed in the studies of protein growth, synthesis, and degradation are described in the chapter. It discusses the mechanism of nutrition and protein synthesis in the fish and explains the impact that protein synthesis has upon the rates of oxygen consumption.