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: 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: New data obtained during re-mapping of the northern part of Syros (Cyclades, Greece) allow the refinement of existing concepts about the structural evolution of this island. A metabasite belt and its metasedimentary envelope near Kampos and San Michali were mapped at a 1:5000 scale, with special emphasis on the structural inventory. The HP/LT rocks (P , 1.5 GPa; T , 500 8C at ,50 Ma) exposed are intensely deformed by at least two isoclinal folding events. Relative age relations between deformation and peak metamorphism indicate that isoclinal folding took place before or during peak metamorphism. Later deformation stages include Miocene non-penetrative upright kink folding and crenulation, transpressional strike-slip faulting, and open upright cylindrical folding, followed by the development of steep normal faults. Taking into account recent zircon U–Pb geochronological constraints, lithostratigraphic observations, and published data on the Neogene structural evolution of the Aegean, we present a history for the rocks of Syros, beginning with the formation of the oceanic crust(represented by the metabasites) to the present.

Description: Volcanology has been in the past and in many respects remains a subject dominated by pure research grounded in the earth sciences. Over the past 30 years a paradigm shift has occurred in hazard assessment which has been aided by significant changes in the social theory of natural hazards and the first-hand experience gained in the 1990s by volcanologists working on projects conceived during the International Decade for Natural Disaster Reduction (IDNDR). Today much greater stress is placed on human vulnerability, the potential for marginalisation of disadvantaged individuals and social groups, and the requirement to make applied volcanology sensitive to the characteristics of local demography, economy, culture and politics. During the IDNDR a methodology, broadly similar to environmental impact analysis, has emerged as the preferred method for studying human vulnerability and risk assessment in volcanically active regions. The characteristics of this new methodology are discussed and the progress which has been made in innovating it on the European Union laboratory volcanoes located in western Europe is reviewed. Furnas (São Miguel, Azores) and Vesuvius in Italy are used as detailed case studies.

Description: In order to explain biological zonation, shore height above the ordnance level is frequently used as an indicator of the abiotic gradient in intertidal ecosystems. This is based on the implicit assumption that shore height is directly correlated with inundation frequency and/or duration. Despite the importance of inundation for tidal ecosystems, measurements have rarely been taken directly by measuring inundation at the site of investigation. We measured mean high tide (MHT) and flooding frequency at three sites on the Dutch Barrier Island of Schiermonnikoog. To assess the scale dependence, we compared local measurements with the estimated inundation frequencies based on the official tide gauge (OTG) farther away. Locally measured MHT water levels differed among sites and were consistently higher than estimated MHT water levels. With this data, we subsequently estimated the inundation frequency of vegetation plots from our measurements and correlated it with species distribution. In a logistic regression inundation frequency accounted for twice the variance in explaining the dominance of three salt marsh species than shore height. The discrepancy in annual inundation frequency of the vegetation between sites was ≦300% for a given shore height. Within each site replicated estimates of inundation frequency proved to be consistent (scale 10–50 m). Estimated and measured inundation frequencies thus reliably correlated at a small-scale (tens of metres), but not at a larger scale (hundreds of metres to kilometres). If inundation frequency is used as an explanatory variable, it will therefore be advisable to consider the spatial heterogeneity of the measurements, in particular if different sites are to be compared. We give mean inundation frequencies of three dominant salt marsh species (Elymus athericus, Festuca rubra, Artemisia maritima) measured over 1 year.