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51.
M. Porreca M. Mattei C. MacNiocaill G. Giordano E. McClelland R. Funiciello 《Bulletin of Volcanology》2008,70(7):877-893
The Peperino Albano (approximately 19–36 ka old) is a phreatomagmatic pyroclastic flow deposit, cropping out along the slopes
of the associated Albano maar (Colli Albani volcano, Italy). The deposit exhibits lateral and vertical transitions from valley
pond to veneer facies, as well as intracrater facies. We present the results of a paleomagnetic study of thermal remanent
magnetization (TRM) of the lithic clasts of the Peperino Albano ignimbrite that provide quantitative estimates of the range
of emplacement temperatures across the different facies of the ignimbrite. Emplacement temperatures estimated for the Peperino
Albano ignimbrite range between 240° and 350°C, with the temperatures defined in the intracrater facies being generally lower
than in the valley pond and veneer facies. This is possibly due to the large size of the sampled clasts in the intracrater
facies which, when coupled with low temperature at the vent, were not completely heated throughout their volume during emplacement.
The emplacement temperatures derived from the paleomagnetic results are in good agreement with the presence of un-burnt plants
at the base of the ignimbrite, indicating that the temperature of the pyroclastic flow was lower than the temperature of ignition
of wood. Paleomagnetic results from the Peperino Albano confirm the reliability of the paleomagnetic approach in defining
the thermal history of pyroclastic flow deposits. 相似文献
52.
53.
重点介绍和讨论了中性条件下旋转扰动流体中边界层强迫不稳定及其相关的一些问题,阐述了旋转体系中切变驱动边界层不稳定的动力学特征.这些不稳定状态的研究在大气物理学、流体动力学、海洋学等多个领域中引起科学家极大的兴趣,近年来在实验和理论研究中都得到了不断的发展.意大利都灵大学基础物理系地球科学实验组通过水槽旋转实验方法,不断改变水槽启动或结束时的旋转运动速度,以及底部壁面粗糙度等要素,所得到的实验结果与SDBL理论非常一致. 相似文献
54.
Late Quaternary environmental and climate changes registered in lacustrine sediments of the Serra Sul de Carajás,south‐east Amazonia 下载免费PDF全文
55.
The granulites of the Juiz de Fora complex occur within thick basement thrust slices associated with the Pan-African shortening process in the central segment of the Ribeira belt. Five lithological units of the Intermediate tectonic domain of the belt can be identified on the basis of detailed geological mapping: a) orthogranulites, b) orthogneisses; c) kinzigite; d) intrusive garnet charnockite and e) amphibolite facies metasediments of probable Meso to Neoproterozoic age, correlated to the cover of the belt. Petrological data indicate high temperatures and intermediate to low lithostatic pressure conditions for the Paleoproterozoic granulite facies metamorphism. Textures and CO2-rich fluid inclusions are probably related to an IBC path. Geochemical data do not show relevant compositional change as a result of the granulite metamorphism. Two calc-alkaline suites and tholeiitic to alkaline basic rocks can be related to compressional and extensional settings, respectively. The overall composition of the granulites, the lack of substantial LILE depletion as well as the composition of the fluid inclusion points to granulitization process driven by CO2-rich fluids. Orthogranulites gave rise to banded gneisses as a result of the Pan-African retrograde metamorphism and intense deformation. The U and Th depletion detected in few rocks is possibly related with the hydrated conditions of the retrograde reactions. 相似文献
56.
Erminio Murano Renato Toffanin Ester Cecere Roberto Rizzo Svein Halvor Knutsen 《Marine Chemistry》1997,58(3-4)
Dried samples of the red algae Solieria filiformis and Agardhiella subulata from Mar Piccolo, Taranto, were extracted by stirring in water at 25 (Cold), 85 (Hot) and 120 (pressure) °C. For each species, six successive cold, three hot and two pressure extractions were performed and analyzed separately. Water-soluble polysaccharides were isolated after treatment with amylase, alcohol precipitation, dialysis and freeze drying. The total, starch-free yields were 27 and 24% of the dry weight for S. filiformis (SF) and A. subulata (AS), respectively. FTIR and NMR spectroscopic analysis showed that the different cold and hot water extracts had a similar structural backbone, which can be characteristic of gelling type carrageenans with a dominant iota repeating structure (DA2S-G4S). However, some irregularities were detected by NMR, which may be attributed to 6-sulphated 4-linked precursor units. The occurrence of such and other irregularities was more frequent in the SF samples, giving a possible explanation for the enhanced extractability in cold water of carrageenan polymers from this species. 相似文献
57.
Zooplankton volume trends off Peru between 1964 and 2001 总被引:5,自引:0,他引:5
Ayon Patricia; Purca Sara; Guevara-Carrasco Renato 《ICES Journal of Marine Science》2004,61(4):478-484
58.
Roberto A. T. Gomes Renato F. Guimarães Osmar A. Carvalho Jr. Nelson F. Fernandes Eurípedes A. Vargas Jr. Éder S. Martins 《Natural Hazards》2008,45(2):197-209
In tropical areas, mass movements are common phenomena, especially during periods of heavy rainfall, which frequently take
place in the summer season. These phenomena have caused loss of life and serious damage to infrastructure and properties.
The most prominent of these phenomena are landslides that can produce debris flows. Thus, this article aims at determining
affected areas using a model to predict landslide prone areas (SHALSTAB) combined with an empirical model designed to define
the debris flow travel distance and area of deposition. The methodology of this work consists of the following steps: (a)
elaboration of a digital elevation model (DEM), (b) application of the deterministic SHALSTAB model to locate the landslide
prone areas, (c) identification of the debris flow travel distance and area of deposition, and (d) mapping of the affected
areas (landslides and debris flows). This work was developed in an area in which many mass movements occurred after intense
rainfall during the summer season (February 1996) in the state of Rio de Janeiro, southeast Brazil. All of the scars produced
by that event were mapped, allowing for validation of the applied models. The model results show that the mapped landslide
locations can adequately be simulated by the model. 相似文献
59.
Renato Macciotta C. Derek Martin Norbert R. Morgenstern David M. Cruden 《Landslides》2016,13(4):765-785
The benefits of quantitative risk assessments for landslide management have been discussed and illustrated in several publications. However, there still are some challenges in its application for low-probability, high-magnitude events. These challenges are associated with the difficulties in populating our models for risk calculations, which largely require the input of expert opinion. This paper presents a quantitative risk assessment to a very slow moving rock slope within a dam reservoir in the Province of British Columbia, Canada. The assessment is focused on the risk to the population in the vicinity of the dam and the populated areas downstream. Expert opinions quantified the slope failure probabilities in the order of 10?3 to 10?1 per year for the smallest failure scenario considered and less than 10?6 for a failure of the entire slope. However, these estimations are associated with high levels of uncertainty. Our approach starts with the calculation and assessment of the magnitude and probability of the potential slope failure consequences, minimizing the uncertainties associated with estimated slope failure probabilities. Then, these consequences and failure probabilities are combined to obtain a measure of risk. The uncertainty associated with the slope failure probabilities is managed by the estimation of plausible ranges for these. The calculated risk levels are then presented as ranges of values and assessed against adopted evaluation criteria. The consequence and risk assessment of the rock slope suggest that the risk to the population exposed in the vicinity of the dam and populated areas downstream is under adequate control. The probability of large consequence scenarios is extremely low, in the order of 10?7 chance of an event causing more than 100 fatalities. We propose an observational technique to assess changes in risk levels and decide when to update the risk management approach or deploy emergency measures. The technique is focused on the detection of changes in the slope deformation patterns that would indicate an increase in the potential failure volumes or an imminent failure. It can be considered an extension to the current early warning system in place, easy to implement and enhanced with the strength of the comprehensive analysis required for a quantitative risk assessment. 相似文献