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: 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: Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcusgroup). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.

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: 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.

Description: A geographically related database called MAGIC has been developed, using GIS (Geographic Information System) technology, for MArine Gas seeps and seep IndiCators. A complementary bibliographic database (GASREF) stores details of related publications. The databases include data relating to natural seabed gas seeps and features such as pockmarks, cold seep communities, and methane-derived carbonates which are known to be found in association with seeps. The databases are compiled from published reports (so far restricted to those written in English), and users are able to interrogate the system for specified features from user-defined areas.

Description: The Catalina Schist (California) contains an amphibolite-grade (0.8–1.1 GPa; 640–750 jC) melange unit consisting of mafic and ultramafic blocks in high-Mg, schistose melange matrix with varying modal proportions of talc, chlorite, anthophyllite, calcic-amphibole, enstatite, and minor phases including zircon, rutile, apatite, spinel, and Fe–Ni sulfides. This melange unit is interpreted as a kilometer-scale zone of tectonic and metasomatic mixing formed within a juvenile subduction zone, the study of which may yield insight into chemical mixing processes at greater depths in subduction zones. Relationships among the major and trace element compositions of the mafic and ultramafic blocks in the melange, the rinds developed at the margins of these blocks, and the surrounding melange matrix are compatible with the evolution of the melange matrix through a complex combination of infiltrative and diffusional metasomatism and a process resembling mechanical mixing. Simple, linear mixing models are compatible with the development of the melange matrix primarily through simple mixture of the ultramafic and mafic rocks, with Cr/Al ratios serving as indicators of the approximate proportions of the two lithologies. This conclusion regarding mafic–ultramafic mixing is consistent with the field observations and chemical trends indicating strong resemblance of large parts of the melange matrix with rinds developed at the margins of mafic and ultramafic blocks. The overall process involved development of metasomatic assemblages through complex fluid-mediated mixing of the blocks and matrix concurrent with deformation of these relatively weak rind materials, which are rich in layer silicates and amphibole. This deformation was sufficiently intense to transpose fabrics, progressively disaggregate more rigid, block-derived materials in weaker chorite- and talc-rich melange, and in some particularly weak lithologies (e.g., chlorite-, talc-, and amphibole-rich materials), intimately juxtapose adjacent lithologies at the (sub-)cm scale (approaching grain scale) sampled by the whole-rock geochemical analyses. Chemical systematics of various elements in the melange matrix can be delineated based on the Cr/Al-based mixing model. Simple mixing relationships exhibited by Al, Cr, Mg, Ni, Fe, and Zr provide a geochemical reference frame for considerations of mass and volume loss and gain within the melange matrix. The compositional patterns of many other elements are explained by either redistribution (local stripping or enrichment) at varying scales within the melange (Ca, Na, K, Ba, and Sr) or massive addition from external sources (Si and H2O), the latter probably in infiltrating H2O-rich fluids that produced the dramatic O and H isotopic shifts in the melange. Melange formation, resulting in the production of high-variance ultramafic assemblages withhigh volatile contents, may aid retention of volatiles (in this case, H2O) to greater depths in subduction zones than in original subducted mafic and sedimentary materials. The presence of such assemblages (i.e., containing minerals such as talc, chlorite, and Mg-rich amphiboles) would impact the rheology of the slab–mantle interface and perhaps contribute to the low-velocity seismic structure observed at/near the slab–mantle interface in some subduction zones. If operative along the slab–mantle interface, complex mixing processes such as these, involving the interplay between fluid-mediated metasomatism and deformation, also could impact slab incompatible trace element and isotopic signatures ultimately observed in arc magmas, producing ‘‘fluids’’ with geochemical signatures inherited from interactions with hybridized rock compositions.

Description: Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for ∼48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO2 to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential.