Gigantic volcanic eruptions and climatic change in the early Eocene

23 layers of altered volcanic ash (bentonites) originating from the North Atlantic Igneous Province have been recorded in early Eocene deposits of the Austrian Alps, about 1,900 km away from the source area. The Austrian bentonites are distal equivalents of the “main ash-phase” in Denmark and the North Sea basin. We have calculated the total eruption volume of this series as 21,000 km³, which occurred in 600,000 years. The most powerful single eruption of this series took place 54.0 million years ago (Ma) and ejected ca. 1,200 km³ of ash material, which makes it one of the largest basaltic pyroclastic eruptions in geological history. The clustering of eruptions must have significantly affected the incoming solar radiation in the early Eocene by the continuous production of stratospheric dust and aerosol clouds. This hypothesis is corroborated by oxygen isotope values, which indicate a global decrease of sea surface temperatures between 1 and 2°C during this major phase of explosive volcanism.     

Variation trends in the alkaline salic rocks of tenerife

The ratio salic rocks/basalts is higher in Tenerife than in other Atlantic islands. It is also surprising the number of intermediate types between phonolites and trachytes and the basalts. The salic rocks of Tenerife have been grouped in to two large units, one related to the edifice of « Las Cañadas » and the other to « Teide-Pico Viejo ». The top of the former collapsed and the latter was built in the Caldera thus formed. Both units belong to a middle atlantic series, but the atlantic character of « Teide-Pico Viejo » is stronger. A clear alkalinitization can be observed during the whole evolution. Most of the materials which are related to the Cañadas edifice are near the saturation line, and they must be classed as phonolites and Na-trachytes. In these rocks a variation trend related to that of the former alkaline basalts can be observed. In the latest episodes of their evolution cutaxite and pumice emissions appeared with great intensity. The « Teide-Pico Viejo » lava-flows are always of phonolite types with high amounts of normative nepheline. These materials also represented the end of the differentiation trend of an alkaline basaltic series, which started after the Cañadas edifice was built. This second trend ended in less silica-rich rocks than those of the Cañadas series.     

Mesozoic limestone from the Vema offset zone,Mid-Atlantic Ridge?

A shallow-water, indurated limestone, consisting of fossil benthic foraminifera, calcareous green algae, fragments of gastropods, thalassinid crab coproliths, as well as inorganic ooids and pelloids, and containing detrital grains of quartz, orthoclase, and microcline, was dredged from the summit of a transverse ridge within the Vema offset zone of the Mid-Atlantic Ridge. Subaerial and submarine recrystallization, suggesting past emergence of the limestone, is indicated by oxygen and carbon isotope analysis. The occurrence in the limestone ofParafavreina, an anomuran crab coprolite fossil, suggests a probable Mesozoic age for the rock. The occurrence of this shallow-water Mesozoic limestone would confirm previous suggestions that a non-spreading crustal block exists at the Vema offset zone.     

Floods and floodplain changes of the River Morava,the Strážnické Pomoraví region (Czech Republic) over the past 130 years

Abstract

The development of the River Morava floodplain has been influenced by several natural and anthropogenic factors. This paper focuses on variations in flood activity and channel changes of the River Morava in the region of Strá?nické Pomoraví (southeastern Czech Republic). Floods are analysed in terms of measured peak water stages, H_k (Rohatec, 1886–1920) and peak discharges Q_k (Rohatec/Strá?nice, 1921–2010) evaluated with respect to their N-year return period (H _N or Q_N ). The frequency of floods with Q_k ≥ Q ₂ reaches a significant maximum in March, followed by July. According to flood series compiled from 1881 onwards, their frequency peaked in the 1961–1970 decade with the most severe events occurring in July 1997 (Q ₁₀₀), March 2006 and June 2010 (Q ₅₀). During the study period the natural dynamics of the original anabranching channel patterns were significantly modified by human intervention, such as the abandonment of some anabranching channels, channel straightening, enlargement of the main channel, flood-dike construction, and the creation of the Ba?a shipping channel. These changes resulted in decreased frequency and a reduction in the extent of floodplain inundations compared to the period prior to channel modifications in the 1930s.

Citation Brázdil, R., Má?ka, Z., ?ezní?ková, L., Soukalová, E., Dobrovolný, P. & Matys Grygar, T. (2011) Floods and floodplain changes of the River Morava, the Strá?nické Pomoraví region (Czech Republic) over the past 130 years. Hydrol. Sci. J. 56(7), 1166–1185.     

Present state of the Baltic Coastal Waters off Mecklenburg-Vorpormmern,Germany

The coastal waters of the former GDR comprising more than 9000 sqkm with a maximum width of 12 n.m. from the baseline and the 1600 sqkm inner bodden waters with a volume of about 6 cu.km are of unique importance to trade by providing transport by sea including three ferry links, to fishing, recreaation and other uses. Based on the results of monitoring programmes carried out between 1973 and 1988 and reviewing existing literature, the state of these waters is discussed. The paper starts with a characterization of the environmental background conditions of the area including its catchment region. Data on population density, fishing, industry, agriculutre and other information is tabulated as deemed necessary to understand the sensitivity of the coastal water and potential impacts on their state.The contamination load released into bodden waters and further into the Baltic Sea by eight relatively small rivers is quantified. In relation to the concentrations of contaminants such as heavy metals, petroleum hydrocarbons and organochlorines, there are no severe environmental problems. However, nutrients and their cycling in the system cause eutrophication. This results (a) in reduced usefulness of the bodden waters for recreation and even fishing, (b) in anoxic sediments and (c) in declining benthos colonization. For some of the contaminants inter-annual and spatial trends were found to be of statistical significance. Summarizing the present knowledge on the state of the coastal waters and realising obvious gaps in the complex scientific understanding and forecasting, measures required to reduce the contaminant load are proposed.     

The spatial dynamics of atmospheric pollution in Latvia and the Baltic Republics,as measured in mosses,topsoil and precipitation

Atmospheric pollution in the Baltic countries of Estonia, Latvia, and Lithuania has been mapped using measurements of pollutant concentrations in mosses, topsoil and precipitation. Air masses from western Europe deposit industrial pollutants in the Baltic region and concentrations depend on meteorological conditions. Superimposed on this background is the pattern of deposits from local sources. Large areas receive neutral to basic precipitation due to cement industries and fly ash emissions from fossil fuel combustion. The burning of oil-shale in NE Estonia results in precipitation with pH values over 7.0, and high concentrations of V, Fe, and Cd. Heavy metal concentrations in the topsoil around large cities indicate ecologically unsound city planning and insufficient control of pollutants. The Chernobyl effect in the form of radioactive deposition depended on rainfall events during the accident.     

The composition of settling particles in Lake Zürich

Settling particles in the Lake Zürich were collected at different depths. Water samples and particles have been analyzed for heavy metals and for organic matter elements. Samples were investigated by transmission electron microscopy, scanning electron microscopy, energy dispersive X ray and X ray. The elemental composition of the settling particles was found to be almost constant. Special remarks are made on iron and phosphate and on manganese. Manganese oxidizing microorganisms were found near the bottom of the lake.     

Moment and duration of shallow earthquakes from Love-wave modelling for regional distances

Love waves from five earthquakes in southwest Germany, Italy, Yugoslavia, Greece and Algeria, as recorded at the broadband Gräfenberg array in eastern Bavaria, are modelled in detail using an extended reflectivity method. The focal mechanisms are taken from the literature or determined from long-period WWNSS data. The theoretical double-couple moment function used for modelling increases smoothly during the risetime T from zero to the seismic moment M₀. T and M₀ are determined by matching the observed and theoretical Love-wave seismograms in the long-period WWNSS frequency band. T is approximately equal to the rupture duration; values from 1.4 to 20 s are found. Seismic moments generally agree within a factor of about two with those found by other authors from larger data sets. The earthquakes in southwest Germany and Greece were simple events and can be modelled very well by one double couple. In the case of the other earthquakes, the theoretical Love-wave seismograms are too short. For these earthquakes there is some independent evidence for a multiple-event nature. This evidence is condensed into source models consisting of two or three double couples representing separate and complete sub-earthquakes, which then explain the observations quite well. In the case of the Algerian earthquake, the long Love-wave duration may also be due to complications in structure along the wavepath across the Mediterranean and the Alps. The present results show that accurate Love-wave modelling for a single station at regional distance from an epicentre is a reliable method for estimation of seismic moment and rupture duration. Use of a digitally recording station with large dynamic range allows events over a large magnitude interval to be studied. The Gräfenberg array is well suited for such an investigation of European and North African earthquakes.     

North Atlantic Oscillation – Concepts And Studies

This paper aims to provide a comprehensive review of previous studies and concepts concerning the North Atlantic Oscillation. The North Atlantic Oscillation (NAO) and its recent homologue, the Arctic Oscillation/Northern Hemisphere annular mode (AO/NAM), are the most prominent modes of variability in the Northern Hemisphere winter climate. The NAO teleconnection is characterised by a meridional displacement of atmospheric mass over the North Atlantic area. Its state is usually expressed by the standardised air pressure difference between the Azores High and the Iceland Low. ThisNAO index is a measure of the strength of the westerly flow (positive with strong westerlies, and vice versa). Together with the El Niño/Southern Oscillation (ENSO) phenomenon, the NAO is a major source of seasonal to interdecadal variability in the global atmosphere. On interannual and shorter time scales, the NAO dynamics can be explained as a purely internal mode of variability of the atmospheric circulation. Interdecadal variability maybe influenced, however, by ocean and sea-ice processes.