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  • 1
    Publication Date: 2020-11-26
    Description: We propose a long-term probabilistic multi-hazard assessment for El Misti Volcano, a composite cone located 〈20 km from Arequipa. The second largest Peruvian city is a rapidly expanding economic centre and is classified by UNESCO as World Heritage. We apply the Bayesian Event Tree code for Volcanic Hazard (BET_VH) to produce probabi- listic hazard maps for the predominant volcanic phenomena that may affect c.900,000 people living around the volcano. The methodology accounts for the natural variability displayed by volcanoes in their eruptive behaviour, such as different types/sizes of eruptions and possible vent locations. For this purpose, we treat probabilistically several model runs for some of the main hazardous phenomena (lahars, pyroclastic density currents (PDCs), tephra fall and ballistic ejecta) and data from past eruptions at El Misti (tephra fall, PDCs and lahars) and at other volcanoes (PDCs). The hazard maps, although neglecting possible interactions among phenomena or cascade effects, have been produced with a homogeneous method and refer to a common time window of 1 year. The probability maps reveal that only the north and east suburbs of Arequipa are exposed to all volcanic threats except for ballistic ejecta, which are limited to the uninhabited but touristic summit cone. The probability for pyroclastic density currents reaching recently expanding urban areas and the city along ravines is around 0.05 %/year, similar to the probability obtained for roof-critical tephra load- ing during the rainy season. Lahars represent by far the most probable threat (around 10 %/year) because at least four radial drainage channels can convey them approximately 20 km away from the volcano across the entire city area in heavy rain episodes, even without eruption. The Río Chili Valley repre- sents the major concern to city safety owing to the probable cascading effect of combined threats: PDCs and rockslides, dammed lake break-outs and subsequent lahars or floods. Although this study does not intend to replace the current El Misti hazard map, the quantitative results of this probabilistic multi-hazard assessment can be incorporated into a multi-risk analysis, to support decision makers in any future improvement of the current hazard evaluation, such as further land-use planning and possible emergency management.
    Description: Published
    Description: 771
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: BET_VH ; TITAN2D ; TEPHRA2 ; Probabilistic volcanic hazard ; Multi-hazard assessment ; El Misti Arequipa ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2021-06-25
    Description: Uncertainties in modelling volcanic hazards are often amplified in geographically large systems and in volcanoes which have a diverse eruption history that comprises variable eruption compositions and styles from different vent locations. The large ~ 700 km2 Okataina Volcanic Centre (OVC) is a large silicic caldera complex in a geodynamic region of New Zealand which has displayed a range of eruption styles and compositions over its current phase of activity (26 ka - present), including one basaltic maar-forming eruption, one basaltic Plinian eruption, and nine rhyolitic Plinian eruptions. All three of these eruption styles have occurred within the past 3.5 ky, and any of these styles could occur in the event of a future eruption. The location of a future eruption is also unknown. Future vents could potentially open in one of three different possible areas of the OVC: the Tarawera linear vent zone (LVZ) (5 eruptions over the past 26 ky), the Haroharo LVZ (5 eruptions over the past 26 ky), or outside of these LVZs (1 eruption over the past 26 ky). A future rhyolitic or basaltic Plinian eruption from the OVC is likely to generate widespread tephra fall in loads that will cause significant disruption and socio- economic impacts throughout the surrounding region. Past OVC tephra studies have focused on evaluating hazard from a rhyolitic Plinian eruption at select vent locations in the OVC's Tarawera LVZ. Here, we expand upon these past studies by evaluating tephra hazard for all possible OVC eruption vent areas and for both rhyolitic and basaltic Plinian eruption styles, and exploring how these parameters influence tephra hazard forecasts. Probabilistic volcanic hazard model BET_VH and advection-diffusion tephra hazard model TEPHRA2 were used to assess the hazard of accumulating ≥ 10 kg m-2 of tephra from both basaltic Plinian and rhyolitic Plinian eruption styles, occurring from within the Tarawera LVZ, the Haroharo LVZ, and other potential vent areas within the caldera. We present the results of these analyses as a first-order tephra hazard assessment for the entire OVC. Our results highlight the importance of considering all the potential vent locations of a volcanic system, in order to capture the full eruption catalogue in analyses (e.g., 11 eruptions over 26 ky for the OVC, versus only 5 eruptions over 26 ky for the Tarawera LVZ), as well as the full potential distribution of tephra hazard. Although the Tarawera LVZ has been prominently discussed in studies of OVC hazard because of is recent activity (1886 and ~1315 AD), we find that, in the event of future eruption, the likelihood of a vent opening within the Haroharo LVZ (last eruption 5.6 ka) is equivalent (〈 1% difference) to that for the Tarawera LVZ (31.8% compared to 32.5%). We also find that an eruption from within the Haroharo LVZ presents a relatively higher hazard to several localities, such as the town of Kawerau, where the average absolute probability of accumulating ≥ 10 kg m-2 of tephra is 1.3 times greater than for an eruption from within the Tarawera LVZ. While the absolute probabilities of accumulating ≥ 10 kg m-2 of tephra in the next one year from a basaltic Plinian eruption are on average 7.2 times lower than for a rhyolitic Plinian eruption throughout the surrounding region, our results suggest that the hazard posed by a basaltic Plinian eruption does contribute to the overall OVC tephra hazard, raising absolute probabilities for the entire OVC by an order of 0.14, which may have implications when considering sensitive decision-making thresholds.
    Description: Published
    Description: 38
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: PVHA ; Okataina Volcanic Centre ; BET_VH ; TEPHRA2 ; volcanic hazard ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2021-06-25
    Description: By using BET_VH, we propose a quantitative probabilistic hazard assessment for base surge impact in Auckland, New Zealand. Base surges resulting from phreatomagmatic eruptions are among the most dangerous phenomena likely to be associated with the initial phase of a future eruption in the Auckland Volcanic Field. The assessment is done both in the long-term and in a specific short-term case study, i.e. the simulated pre-eruptive unrest episode during Exercise Ruaumoko, a national civil defence exercise. The most important factors to account for are the uncertainties in the vent location (expected for a volcanic field) and in the run-out distance of base surges. Here, we propose a statistical model of base surge run-out distance based on deposits from past eruptions in Auckland and in analogous volcanoes. We then combine our hazard assessment with an analysis of the costs and benefits of evacuating people (on a 1km x 1km cell grid). In addition to stressing the practical importance of a cost-benefit analysis in creating a bridge between volcanologists and decision makers, our study highlights some important points. First, in the Exercise Ruaumoko application, the evacuation call seems to be required as soon as the unrest phase is clear; additionally, the evacuation area is much larger than what is recommended in the current Contingency Plan. Secondly, the evacuation area changes in size with time, due to a reduction in the uncertainty in the vent location and increase in the probability of eruption. It is the tradeoff between these two factors that dictates which cells must be evacuated, and when, thus determining the ultimate size and shape of the area to be evacuated.
    Description: Published
    Description: 705-723
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Auckland Volcanic Field ; Base surge ; Bayesian event tree ; Volcanic hazard ; Cost benefit analysis ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2017-04-04
    Description: The statistical modeling of the time-size distribution of volcanic eruptions is a fundamental tool to understand better the physics of the eruptive process, and to make reliable forecasts [Newhall and Hoblitt, 2002; Connor et al., 2003; Marzocchi et al., 2004a; Sparks and Aspinall, 2004]. Eruption forecasting is commonly associated to different timescales (short-, intermediate-, and long-term; see definition by Newhall and Hoblitt [2002]). Regardless of the time frame, the statistical modeling of the past behavior of a volcano is a key ingredient for quantitative forecasting (usually, but not necessarily, over long time intervals) when the volcano has an almost stationary state (for instance, it is dormant). In this case, monitoring data are not particularly informative of the future evolution of the system, at least until the volcano becomes restless and/or changes its stationary state. Hereinafter, the terms ‘‘eruption forecasting’’ and ‘‘volcanic hazard’’ refer to this stationary case. [3] The main difficulties in providing a general model of eruptive activity are linked to the existence of different types of volcanic activity, to the paucity of eruptive data for most volcanoes, and to the intrinsic complexity of eruptive processes. As a consequence, most of the past papers devoted to this issue are focused on single (or very few) volcanoes [e.g., Wickman, 1976; Klein, 1982; Burt et al., 1994; Bebbington and Lai, 1996; Marzocchi, 1996; Connor et al., 2003; Gusev et al., 2003; Sandri et al., 2005] where detailed eruptive catalogs exist. This approach limits the generality of the results. We cannot know if the behavior of the volcano analyzed represents a generic feature of a specific type of volcanism, or if it is peculiar of the volcano itself. Under this perspective, part of the different statistical distributions found by analyzing single eruptive catalogs can be explained by the existence of some peculiarities in volcanic activity. [4] One way to overcome this drawback, which we use here, is to perform a common analysis on data from several volcanoes. In particular, we test the Poisson hypothesis in the time domain, and the reliability of time-size distributions such as the time predictable model and size predictable model. The results obtained are then used to build a quantitative model of the statistical time-size distribution for some classes of volcanic activities that can be used for volcanic hazard assessment.
    Description: Published
    Description: B04204
    Description: JCR Journal
    Description: reserved
    Keywords: quantitative model ; eruptions ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publication Date: 2017-04-04
    Description: Knowledge of past precursor patterns is crucial for the correct interpretation of monitoring data and reliable volcano forecasting. In the case of Vesuvius, one of the world’s riskiest volcanoes, very little information is available about unrest signals following long periods of quiescence. The translation and analysis of three Latin treatises written from eye-witnesses immediately after the A.D. 1631 subplinian eruption allowed us to reconstruct the sequence of precursors. The progression in the signals was remarkably clear starting at least two to three weeks before the event. Widespread gas emission from the ground coupled with deformation was followed by an increase in seismic activity in the eight days before the eruption. Seismicity escalated both in frequency and intensity in the night before the eruption, heralding the opening of fissures on the volcanic cone. The details of phenomena occurring in the medium-term (months before the eruption) are difficult to evaluate, though it is worth noticing that no major tectonic earthquakes were felt in the area of the volcano. Civil protection preparedness plans should be organized in order to complete the evacuation of people in a time span significantly shorter than the duration of expected short-term precursors.
    Description: Published
    Description: L18317
    Description: JCR Journal
    Description: reserved
    Keywords: Vesuvius ; A. D. 1631 ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
    Publication Date: 2017-04-04
    Description: Numerical simulation of pyroclastic density currents has developed significantly in recent years and is increasingly applied to volcanological research. Results from physical modeling are commonly taken into account in volcanic hazard assessment and in the definition of hazard mitigation strategies. In this work, we modeled pyroclastic density currents in the Phlegrean Fields caldera, where flows propagating along the flat ground could be confined by the old crater rims that separate downtown Naples from the caldera. The different eruptive scenarios (mass eruption rates, magma compositions, and water contents) were based on available knowledge of this volcanic system, and appropriate vent conditions were calculated for each scenario. Simulations were performed along different topographic profiles to evaluate the effects of topographic barriers on flow propagation. Simulations highlighted interesting features associated with the presence of obstacles such as the development of backflows. Complex interaction between outward moving fronts and backflows can affect flow propagation; if backflows reach the vent, they can even interfere with fountain dynamics and induce a more collapsing behavior. Results show that in the case of large events ( 108 kg/s), obstacles affect flow propagation by reducing flow velocity and hence dynamic pressure in distal regions, but they cannot stop the advancement of flows. Deadly conditions (in terms of temperature and ash concentration) characterize the entire region invaded by pyroclastic flows. In the case of small events (2.5 107 kg/s), flows are confined by distal topographic barriers which provide valuable protection to the region beyond.
    Description: Published
    Description: Q11003
    Description: JCR Journal
    Description: reserved
    Keywords: Phlegrean Fields ; multiphase flow ; pyroclastic flows ; dynamic pressure ; volcanic hazard ; caldera ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
    Publication Date: 2017-04-04
    Description: We produce a spatial probability map of vent opening (susceptibility map) at Etna, using a statistical analysis of structural features of flank eruptions of the last 2 ky. We exploit a detailed knowledge of the volcano structures, including the modalities of shallow magma transfer deriving from dike and dike-fed fissure eruptions analysis on historical eruptions. Assuming the location of future vents will have the same causal factors as the past eruptions, we converted the geological and structural data in distinct and weighted probability density functions, which were included in a non-homogeneous Poisson process to obtain the susceptibility map. The highest probability of new eruptive vents opening falls within a N-S aligned area passing through the Summit Craters down to about 2,000 ma.s.l. on the southern flank. Other zones of high probability follow the North-East, East-North-East, West, and South Rifts, the latter reaching low altitudes (∼400 m). Less susceptible areas are found around the faults cutting the upper portions of Etna, including the western portion of the Pernicana fault and the northern extent of the Ragalna fault. This structuralbased susceptibility map is a crucial step in forecasting lava flow hazards at Etna, providing a support tool for decision makers.
    Description: This study was performed with the financial support from the V3-LAVA project (DPC-INGV 2007–2009 contract).
    Description: Published
    Description: 2083–2094
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: restricted
    Keywords: Flank eruption ; Dike ; Volcano structure ; Susceptibility map ; Spatial clustering ; Back analysis ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2017-04-04
    Description: Any effective volcanic risk mitigation strat- egy requires a scientific assessment of the future evo- lution of a volcanic system and its eruptive behavior. Some consider the onus should be on volcanologists to provide simple but emphatic deterministic forecasts. This traditional way of thinking, however, does not deal with the implications of inherent uncertainties, both aleatoric and epistemic, that are inevitably present in observations, monitoring data, and interpretation of any natural system. In contrast to deterministic pre- dictions, probabilistic eruption forecasting attempts to quantify these inherent uncertainties utilizing all avail- able information to the extent that it can be relied upon and is informative. As with many other natural hazards, probabilistic eruption forecasting is becoming established as the primary scientific basis for planning rational risk mitigation actions: at short-term (hours to weeks or months), it allows decision-makers to pri- oritize actions in a crisis; and at long-term (years to decades), it is the basic component for land use and emergency planning. Probabilistic eruption forecasting consists of estimating the probability of an eruption event and where it sits in a complex multidimensional time–space–magnitude framework. In this review, we discuss the key developments and features of models that have been used to address the problem.
    Description: Published
    Description: 1777-1805
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: eruption forecasting ; volcanic hazard ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
    Publication Date: 2017-04-04
    Description: To better understand the mechanisms leading to different radon background levels in volcanic settings, we have performed two long-term deformation experiments of 16 days using a real-time setup that enables us to monitor any variation of radon activity concentration during rock compression. Our measurements demonstrate that, in the case of highly porous volcanic rocks, the emanating power of the substrate changes as a function of the volcanic stress conditions. Constant magmatic pressures, such as those observed during dike intrusions and hydrothermal fluid injections, can result in pervasive pore collapse that is mirrored by a significant radon decrease until a constant emanation is achieved. Conversely, repeated cycles of stress due to, for example, volcano inflation/deflation cycles, cause a progressive radon increase a few days (but even weeks and months) before rupture. After rock failure, however, the formation of new emanation surfaces leads to a substantial increase of the radon signal. Our results suggest that surface deformation in tectonic and volcanic settings, such as inflation/ deflation or constant magmatic pressures, have important repercussions on the emanating power of volcanic substrates.
    Description: Published
    Description: 751
    Description: 2R. Laboratori sperimentali e analitici
    Description: JCR Journal
    Description: restricted
    Keywords: Radon monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
    Publication Date: 2017-04-04
    Description: Mt. Cameroon is one of the most active effusive volcanoes in Africa. About 500,000 people living or working around its fertile flanks are subject to significant threat from lava flow inundation. Lava flow hazard and risk were assessed by simulating probable lava flow paths using the DOWNFLOW code. The vent opening probability density function and lava flow length distribution were determined on the basis of available data from past eruptions at Mt. Cameroon volcano. Code calibration was performed through comparison with real lava flow paths. The topographic basis for simulations was the 90-m resolution SRTM DEM. Simulated lava flows from about 80,000 possible vents were used to produce a detailed lava flow hazard map. The lava flow risk in the area was mapped by combining the hazard map with digitized infrastructures (i.e., human settlements and roads). Results show that the risk of lava flow inundation is greatest in the most inhabited coastal areas comprising the town of Limbe, which constitutes the center of Cameroon’s oil industry and an important commercial port. Buea, the second most important town in the area, has a much lower risk although it is significantly closer to the summit of the volcano. Non-negligible risk characterizes many villages and most roads in the area surrounding the volcano. In addition to the conventional risk mapping described above, we also present (1) two reversed risk maps (one for buildings and one for roads), where each point on the volcano is classified according to the total damage expected as a consequence of vent opening at that point; (2) maps of the lava catchments for the two main towns of Limbe and Buea, illustrating the expected damage upon venting at any point in the catchment basin. The hazard and risk maps provided here represent valuable tools for both medium/long-term land-use planning and real-time volcanic risk management and decision making.
    Description: Published
    Description: 423-439
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Lava flow simulation ; Lava flow hazard ; Lava flow risk ; Mt. Cameroon ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
    Publication Date: 2017-04-04
    Description: The Campi Flegrei caldera is a restless structure affected by general subsidence and ongoing resurgence of its central part. The persistent activity of the system and the explosive character of the volcanism lead to a very high volcanic hazard that, combined with intense urbanization, corresponds to a very high volcanic risk. One of the largest sources of uncertainty in volcanic hazard/risk assessment for Campi Flegrei is the spatial location of the future volcanic activity. This paper presents and discusses a long- term probability hazard map for vent opening in case of renewal of volcanism at the Campi Flegrei caldera, which shows the spatial conditional probability for the next vent opening, given that an eruption occurs. The map has been constructed by building a Bayesian inference scheme merging prior information and past data. The method allows both aleatory and epistemic uncertainties to be evaluated. The probability map of vent opening shows that two areas of relatively high probability are present within the active portion of the caldera, with a probability approximately doubled with respect to the rest of the caldera. The map has an immediate use in evaluating the areas of the caldera prone to the highest volcanic hazard. Furthermore, it represents an important ingredient in addressing the more general problem of quantitative volcanic hazards assessment at the Campi Flegrei caldera.
    Description: Published
    Description: 497-510
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Volcanic hazards assessment . Campi Flegrei . Vent opening probability map . Bayesian inference ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 12
    Publication Date: 2017-04-04
    Description: Pyroclastic density currents (PDC) related to paroxysmal eruptions have caused a large number of casualties in the recent history of Stromboli. We combine here a critical review of historical chronicles with detailed stratigraphic,textural, and petrographic analyses of PDC deposits emplaced at Stromboli over the last century to unravel the origin of currents, their flow mechanism and the depositional dynamics. We focus on the 1930 PDC as they are well described in historical accounts and because the 1930 eruption stands as the most voluminous and destructive paroxysm of the last 13 centuries. Stromboli PDC deposits are recognizable from their architecture and the great abundance of fresh, well-preserved juvenile material. General deposit features indicate that Stromboli PDC formed due to the syn-eruptive gravitational collapse of hot pyroclasts rapidly accumulated over steep slopes. Flow channelization within the several small valleys cut on the flanks of the volcano can enhance the mobility of PDC, as well as the production of fine particles by abrasion and comminution of hot juvenile fragments, thereby increasing the degree of fluidization. Textural analyses and historical accounts also indicate that PDC can be fast (15–20 m/s) and relatively hot (360–700 °C). PDC can thus flow right down the slopes of the volcano, representing a major hazard. For this reason, they must be adequately taken into account when compiling risk maps and evaluating volcanic hazard on the Island of Stromboli.
    Description: Published
    Description: 827-840
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Stromboli, Pyroclastic density currents, Paroxysms, Basaltic explosive volcanism,Volcanic hazard ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 13
    Publication Date: 2020-02-05
    Description: The definition of probabilistic models as mathematical structures to describe the response of a volcanic system is a plausible approach to characterize the temporal behavior of volcanic eruptions, and constitutes a tool for long-term eruption forecasting. This kind of approach is motivated by the fact that volcanoes are complex systems in which a com- pletely deterministic description of the processes preceding eruptions is practically impos- sible. To describe recurrent eruptive activity we apply a physically-motivated probabilistic model based on the characteristics of the Brownian passage-time (BPT) distribution; the physical process defining this model can be described by the steady rise of a state variable from a ground state to a failure threshold; adding Brownian perturbations to the steady load- ing produces a stochastic load-state process (a Brownian relaxation oscillator) in which an eruption relaxes the load state to begin a new eruptive cycle. The Brownian relaxation os- cillator and Brownian passage-time distribution connect together physical notions of unob- servable loading and failure processes of a point process with observable response statistics. The Brownian passage-time model is parameterized by the mean rate of event occurrence, μ , and the aperiodicity about the mean, α . We apply this model to analyze the eruptive his- tory of Miyakejima volcano, Japan, finding a value of 44.2(±6.5 years) for the μ parameter and 0.51(±0.01) for the (dimensionless) α parameter. The comparison with other models often used in volcanological literature shows that this pysically-motivated model may be a good descriptor of volcanic systems that produce eruptions with a characteristic size. BPT is clearly superior to the exponential distribution and the fit to the data is comparable to other two-parameters models. Nonetheless, being a physically-motivated model, it provides an insight into the macro-mechanical processes driving the system.
    Description: INGV - Sezione di Bologna; Universita' di Bologna - Marco Polo program
    Description: Published
    Description: 545-558
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: open
    Keywords: Probabilistic models; Brownian passage-time distribution; ; Hazard function; Miyakejima volcano ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis ; 05. General::05.08. Risk::05.08.01. Environmental risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 14
    Publication Date: 2020-02-05
    Description: Eruption forecasting refers, in general, to the assessment of the occurrence probability of a given erup- tive event, whereas volcanic hazards are normally associated with the analysis of superficial and evident phenomena that usually accompany eruptions (e.g., lava, pyroclastic flows, tephra fall, lahars, etc.). Nevertheless, several hazards of volcanic origin may occur in noneruptive phases dur- ing unrest episodes. Among others, remarkable examples are gas emissions, phreatic explosions, ground deforma- tion, and seismic swarms. Many of such events may lead to significant damages, and for this reason, the “risk” associ- ated to unrest episodes could not be negligible with respect to eruption-related phenomena. Our main objective in this paper is to provide a quantitative framework to calculate probabilities of volcanic unrest. The mathematical frame- work proposed is based on the integration of stochastic mod- els based on the analysis of eruption occurrence catalogs into a Bayesian event tree scheme for eruption forecast- ing and volcanic hazard assessment. Indeed, such models are based on long-term eruption catalogs and in many cases allow a more consistent analysis of long-term tem- poral modulations of volcanic activity. The main result of this approach is twofold: first, it allows to make inferences about the probability of volcanic unrest; second, it allows to project the results of stochastic modeling of the eruptive history of a volcano toward the probabilistic assessment of volcanic hazards. To illustrate the performance of the pro- posed approach, we apply it to determine probabilities of unrest at Miyakejima volcano, Japan.
    Description: Published
    Description: 689
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: open
    Keywords: Volcanic unrest ; Eruption forecasting ; Bayesian event tree ; Stochastic models ; Miyakejima volcano ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 15
    Publication Date: 2023-08-08
    Description: Within the Ararat Valley (Armenia), a continuously growing water demand (for irrigation and fish farming) and a simultaneous decline in groundwater recharge (due to climate change) result in increasing stress on the local groundwater resources. This detrimental development is reflected by groundwater-level drops and an associated reduction of the area with artesian conditions in the valley centre. This situation calls for increasing efforts aimed at more sustainable water resources management. The aim of this baseline study was the collection of data that allows for study on the origin and age distribution of the Ararat Valley groundwater based on environmental tracers, namely stable (δ〈sup〉2〈/sup〉H, δ〈sup〉18〈/sup〉O) and radioactive (〈sup〉35〈/sup〉S, 〈sup〉3〈/sup〉H) isotopes, as well as physical-chemical indicators. The results show that the Ararat Valley receives modern recharge, despite its (semi-)arid climate. While subannual groundwater residence times could be disproved (〈sup〉35〈/sup〉S), the detected 〈sup〉3〈/sup〉H pattern suggests groundwater ages of several decades, with the oldest waters being recharged around 60 years ago. The differing groundwater ages are reflected by varying scatter of stable isotope and hydrochemical signatures. The presence of young groundwater (i.e., younger that the 1970s), some containing nitrate, indicates groundwater vulnerability and underscores the importance of increased efforts to achieve sustainable management of this natural resource. Since stable isotope signatures indicate the recharge areas to be located in the mountains surrounding the valley, these efforts must not be limited to the central part of the valley where most of the abstraction wells are located.
    Description: Technische Universität Darmstadt (3139)
    Keywords: ddc:551 ; Groundwater residence time ; Tritium ; Radiosulphur ; Stable isotopes ; Armenia
    Language: English
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  • 16
    Publication Date: 2023-08-01
    Description: Cereal crop production in sub-Saharan Africa has not achieved the much-needed increase in yields to foster economic development and food security. Maize yields in the region’s semi-arid agroecosystems are constrained by highly variable rainfall, which may be worsened by climate change. Thus, the Tanzanian government has prioritized agriculture as an adaptation sector in its intended nationally determined contribution, and crop management adjustments as a key investment area in its Agricultural Sector Development Programme. In this study, we investigated how future changes in maize yields under different climate scenarios can be countered by regional adjusted crop management and cultivar adaptation strategies. A crop model was used to simulate maize yields in the Singida region of Tanzania for the baseline period 1980–2012 and under three future climate projections for 2020–2060 and 2061–2099. Adaptation strategies to improve yields were full irrigation, deficit irrigation, mulch and nitrogen addition and another cultivar. According to our model results, increase in temperature is the main driver of future maize yield decline. Increased respiration and phenological development were associated with lower maize yields of 16% in 2020–2060 and 20% in 2061–2099 compared to the 1980–2012 baseline. Surprisingly, none of the management strategies significantly improved yields; however, a different maize variety that was tested as an alternative coping strategy performed better. This study suggests that investment in accessibility of improved varieties and investigation of maize traits that have the potential to perform well in a warmer future are better suited for sustaining maize production in the semi-arid region than adjustments in crop management.
    Description: Leibniz Centre for Agricultural Landscape Research (ZALF)
    Description: Universität Hohenheim (3153)
    Keywords: ddc:631 ; Maize ; Climate change ; Adaptation ; Model ; Tanzania ; NDC
    Language: English
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  • 17
    Publication Date: 2023-06-23
    Description: Die Ergebnisse regionaler Klimaprojektionen für Deutschland weisen auf eine Zunahme der mittleren Lufttemperatur und eine innerjährliche Verschiebung der Niederschläge – mit feuchteren Wintern und trockeneren Sommern – hin. Darüber hinaus werden sich regional die Häufigkeit, Intensität und Dauer von Hitzewellen, Trockenperioden und Starkregenereignissen weiter erhöhen. Durch diese Veränderungen wird sich auch der Jahresgang der Grundwasserneubildung ändern. Als Folge dessen können sich Änderungen bei den hohen, mittleren und tiefen Grundwasserständen, Grundwasserschwankungsbreiten und dem Grundwasserdargebot ergeben. Aber nicht nur die Ressource Grundwasser wird durch die Folgen des Klimawandels betroffen. Auch die gesamte Infrastruktur – von der Förderung bis zur Verteilungsleitung zum Kunden – kann beeinträchtigt werden. Neben den direkten Einflüssen sind auch indirekte Beeinflussungen durch Kaskadeneffekte – beispielsweise ausgehend vom Energiesektor – möglich. Darum gilt es integrative, ganzheitliche und systemische Lösungen zu erarbeiten, um die Funktionalität der kritischen Infrastruktur dauerhaft auch unter Berücksichtigung der Folgen des Klimawandels gewährleisten zu können.
    Description: Helmholtz-Zentrum Geesthacht - Zentrum für Material- und Küstenforschung GmbH (HZG) (4216)
    Description: Climate change impacts on groundwater use—impacts and action needs
    Keywords: ddc:304.28 ; Klimawandel ; Wasserversorgung ; Kritische Infrastruktur ; Anpassung ; Climate change ; Impacts ; Water supply ; Critical infrastructure ; Adaptation
    Language: German
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  • 18
    Publication Date: 2023-07-20
    Description: Late Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.
    Description: TÜBİTAK
    Description: İTÜ-BAP
    Description: TÜBA
    Description: Freie Universität Berlin (1008)
    Keywords: ddc:551 ; Thrace Basin ; Shortening ; Oligocene ; Miocene ; Aegean
    Language: English
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  • 19
    Publication Date: 2023-07-20
    Description: New whole-rock geochemical and coupled U–Pb and Lu–Hf LA-ICP-MS zircon data of metasedimentary rocks of the Austroalpine, South Alpine and Penninic basement domains are presented, to disentangle the pre-Variscan tectonic evolution of the proto-Alps. The studied units seem to record distinct stages of protracted Late Ediacaran to Carboniferous tectonosedimentary processes prior to the Variscan collision. In the case of Austroalpine and South Alpine units, nevertheless, no major differences in terms of provenance are observed, since most detrital zircon samples are characterized by a major Pan-African peak. Their detrital zircon spectra record a provenance from the northeastern Saharan Metacraton and the Sinai basement at the northern Arabian-Nubian Shield, being thus located along the eastern Early Paleozoic northern Gondwana margin, whereas sources located further west are inferred for the Penninic Unit, which might have been placed close to the Moldanubian Unit of the Bohemian Massif. In any case, it is thus clear that the Alpine basement remained in a close position to the Gondwana mainland at least during the Early Paleozoic. The Late Ediacaran to Silurian tectonic evolution, which includes Cadomian and Cenerian tectonometamorphic and magmatic processes, seem thus to record a continuum related to a retreating-mode accretionary orogen, with diachronous back-arc basin opening and possibly discrete compressional/transpressional pulses linked to changes in subduction zone dynamics. On the other hand, it is inferred that the Alpine basement essentially comprises Pan-African metasedimentary and subordinate metaigneous rocks, possibly with very few Early Neoproterozoic relics. This basement was significantly reworked during the protracted Paleozoic orogenic evolution, due to anatexis and/or assimilation by mantle-derived juvenile magmatism.
    Description: Georg-August-Universität Göttingen (1018)
    Keywords: ddc:551 ; Alpine basement ; Cadomian orogeny ; Cenerian orogeny ; Retreating-mode accretionary orogen ; Sedimentary provenance ; Detrital zircons
    Language: English
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  • 20
    Publication Date: 2023-07-27
    Description: Extensive morphological and age studies on more than 4600 detrital zircon grains recovered from modern sands of Namibia reveal complex mechanisms of sediment transport. These data are further supplemented by a zircon age database containing more than 100,000 single grain analyses from the entire southern Africa and allow for hypothesising of a large Southern Namibian Sediment Vortex located between the Damara Orogen and the Orange River in southern Namibia. The results of this study also allow assuming a modified model of the Orange River sand highway, whose origin is likely located further south than previously expected. Moreover, studied samples from other parts of Namibia give first insights into sediment movements towards the interior of the continent and highlight the potential impact of very little spatial variations of erosion rates. Finally, this study points out the huge potential of detrital zircon morphology and large geo-databases as an easy-to-use additional tool for provenance analysis.
    Description: deutsche forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Senckenberg Naturhistorische Sammlungen Dresden (3507)
    Keywords: ddc:551 ; Namibia ; Zircon ; Mineral morphology ; Sediment transport ; Geochronology ; Database
    Language: English
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  • 21
    Publication Date: 2023-07-27
    Description: The Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.
    Description: Westfälische Wilhelms-Universität Münster (1056)
    Description: https://github.com/jeanbraun
    Keywords: ddc:551 ; European Alps ; Tauern Window ; Thermochronology ; Thermokinematic modeling
    Language: English
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  • 22
    Publication Date: 2023-07-21
    Description: Late Paleozoic (Variscan) magmatism is widespread in Central Europe. The Lusatian Block is located in the NE Bohemian Massif and it is part of the Saxothuringian Zone of the Variscan orogen. It is bordered by two major NW-trending shear zones, the Intra-Sudetic Fault Zone towards NE and the Elbe Fault Zone towards SW. The scarce Variscan igneous rocks of the Lusatian Block are situated close to these faults. We investigated 19 samples from Variscan plutonic and volcanic rocks of the Lusatian Block, considering all petrological varieties (biotite-bearing granites from the Koenigshain and Stolpen plutons, amphibole-bearing granites from three boreholes, several volcanic dykes, and two volcanites from the intramontane Weissig basin). We applied whole-rock geochemistry (18 samples) and zircon evaporation dating (19 samples). From the evaporation data, we selected six representative samples for additional zircon SHRIMP and CA–ID–TIMS dating. For the Koenigshain pluton, possible protoliths were identified using whole-rock Nd-isotopes, and zircon Hf- and O-isotopes. The new age data allow a subdivision of Variscan igneous rocks in the Lusatian Block into two distinct magmatic episodes. The spatial relation of the two age groups to either the Elbe Fault Zone (298–299 Ma) or the Intra-Sudetic Fault Zone (312–313 Ma) together with reports on the fault-bound character of the dated intrusions suggests an interpretation as two major post-collisional faulting episodes. This assumption of two distinct magmatic periods is confirmed by a compilation of recently published zircon U–Pb CA–ID–TIMS data on further Variscan igneous rocks from the Saxothuringian Zone. New geochemical data allow us to exclude a dominant sedimentary protolith for the Koenigshain pluton as supposed by previous investigations. This conclusion is mainly based on new O- and Hf-isotope data on zircon and the scarcity of inherited zircons. Instead, acid or intermediate igneous rocks are supposed as the main source for these I-type granitoids from the Koenigshain pluton.
    Description: Technische Universität Bergakademie Freiberg (3135)
    Keywords: ddc:551 ; Geochronology ; Zircon ; Variscan granites ; Lusatian block
    Language: English
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  • 23
    Publication Date: 2023-06-17
    Description: Paleo-shorelines on continental shelves give insights into the complex development of coastlines during sealevel cycles. This study investigates the geologic development of the Limpopo Shelf during the last sealevel cycle using multichannel seismic and acoustic datasets acquired on the shelf in front of the Limpopo River mouth. A detailed investigation of seismic facies, shelf bathymetry, and a correlation to sea level revealed the presence of numerous submerged shorelines on the shelf. These shorelines are characterized by distinct topographic ridges and are interpreted as coastal dune ridges that formed in periods of intermittent sealevel still-/slowstand during transgression. The shorelines are preserved due to periods of rapid sealevel rise (melt water pulses) that led to the overstepping of the dune ridges as well as due to early cementation of accumulated sediments that increased the erosive resistance of the ridges. The high along-shelf variability of the submerged dune ridges is interpreted as a result of pre-existing topography affecting shoreline positions during transgression. The pre-existing topography is controlled by the underlying sedimentary deposits that are linked to varying fluvial sediment input at different points on the shelf. The numerous prominent submerged dune ridges form barriers for the modern fluvial sediment from the Limpopo River and dam sediment on the inner shelf. They may also facilitate along-shelf current-induced sediment transport.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551 ; Limpopo Shelf ; Geology
    Language: English
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  • 24
    Publication Date: 2023-06-17
    Description: After the onset of plate collision in the Alps, at 32–34 Ma, the deep structure of the orogen is inferred to have changed dramatically: European plate break-offs in various places of the Alpine arc, as well as a possible reversal of subduction polarity in the eastern Alps have been proposed. We review different high-resolution tomographic studies of the upper mantle and combine shear- and body-wave models to assess the most reliable geometries of the slabs. Several hypotheses for the tectonic evolution are presented and tested against the tomographic model interpretations and constraints from geologic and geodetic observations. We favor the interpretation of a recent European slab break-off under the western Alps. In the eastern Alps, we review three published scenarios for the subduction structure and propose a fourth one to reconcile the results from tomography and geology. We suggest that the fast slab anomalies are mainly due to European subduction; Adriatic subduction plays no or only a minor role along the Tauern window sections, possibly increasing towards the Dinarides. The apparent northward dip of the slab under the eastern Alps may be caused by imaging a combination of Adriatic slab, from the Dinaric subduction system, and a deeper lying European one, as well as by an overturned, retreating European slab.
    Description: GRNE graduate school
    Description: Deutsche Forschungsgemeinschaft (DE)
    Description: H2020 Marie Skłodowska-Curie Actions ()
    Description: http://www.orfeus-eu.org/eida
    Keywords: ddc:551 ; Seismic tomography ; Subduction slabs ; Alpine subduction system ; Slab break-off ; Slab polarity reversal
    Language: English
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  • 25
    Publication Date: 2023-06-17
    Description: The Namibian Mesozoic successions may be remnant of a high dynamic sedimentary system that is characterized by multiple stages of sediment accumulation and erosion with contemporaneous homogenization starting with the deposition of the Permo-Carboniferous Dwyka Group strata and continues at least until the Lower Cretaceous. The Lower Cretaceous sedimentary system is interpreted to have involved at least an area covering the whole SW Gondwana, documenting the sedimentary history during the evolution from an ice house environment to an arid desert. To test the sediment homogenization hypothesis, we applied a combination of isotopic and morphometric data on detrital zircon grains, as well as whole-rock geochemical data of selected Mesozoic sandstones from Namibia. As a base for the interpretation of the detrital zircon age data we compiled a zircon age dataset with c. 44,000 analyses for the southern African region. All samples reveal a major detrital pan-African zircon age peak of c. 0.5–0.7 Ga sourced from the pan-African magmatic events occurring around the Kalahari Craton margin. The lowermost Triassic is characterized by the occurrence of additional Mesoproterozoic and Paleoproterozoic age peaks of c. 1.0–1.2 Ga and 1.8–2.0 Ga with a majority of zircon grains showing angular shapes. The protosource of these grains is interpreted to possibly be the Namaqua Metamorphic Complex and other Paleoproterozoic structural units deformed in course of the Namaqua orogeny. In contrast, other samples show a prominent Permo-Triassic age peak and completely rounded zircon grains, putatively derived from within the Gondwanides volcanic arc. The disparity in the zircon age pattern may point towards a change in provenance and also a change in the whole system of zircon recycling during the Mesozoic southern Gondwana. The Lower Triassic Neu Loore fm. are constrained to more local bedrock sources and short zircon transport distance. In contrast, zircon grains of the Middle Triassic Omingonde, the Jurassic Etjo und the Cretaceous Twyfelfontein formations are an expression for a major recycling and sediment homogenization system. The system was facilitated by an interplay between fluvial and eolian sedimentary transport systems.
    Keywords: ddc:551 ; Zircon U–pb ; Mesozoic ; Gondwana ; Karoo ; Namibia
    Language: English
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  • 26
    Publication Date: 2023-08-17
    Description: Samples and documentation of outcrops and drillings, facies analysis, whole rock geochemistry and radiometric ages have been employed to re-evaluate the Late Carboniferous Tharandt Forest caldera (TFC) and the co-genetic Niederbobritzsch granite (NBG) in the eastern Erzgebirge near Dresden, Germany. The c. 52 km2 TFC harbours strongly welded ignimbrites with a preserved minimum thickness of 550 m. Composition of initial fallout tephra at the base of the TFC fill, comprising lithics of rhyolitic and basic lava, and of silica-rich pyroclastic rocks, suggests a bimodal volcanic activity in the area prior to the climactic TFC eruption. The lower part of the TFC fill comprises quartz-poor ignimbrites, overlain by quartz-rich ignimbrites, apparently without a depositional break. Landslides originating from the collapse collar of the caldera plunged into the still hot TFC fill producing monolithic gneiss mesobreccia with clasts ≤ 1 m in a pyroclastic matrix. Aphanitic and porphyritic rhyolitic magma formed ring- and radial dykes, and subvolcanic bodies in the centre of TFC. Whole rock geochemical data indicate a high silica (most samples have 〉 73 wt% SiO2) rhyolitic composition of the TFC magma, and a similar granodiorite–granitic composition for the NBG. Based on drillings and caldera extent, a minimum volume of 22 km3 of TFC fill is preserved, the original fill is assumed at about 33 km3. This estimate translates into a denudation of at least c. 210 m during Late Paleozoic to pre-Cenomanian. Telescopic subsidence of the TFC took place in two, perhaps three stages. A possible TFC outflow facies has been completely eroded and distal TFC tuff has not been recognized in neighboring basins. New CA-ID-TIMS measurements on two TFC samples gave mean zircon ages of 313.4 ± 0.4 Ma and 311.9 ± 0.4 Ma; two samples from NBG resulted in 318.2 ± 0.5 Ma and 319.5 ± 0.4 Ma. In addition, for one sample of the ring dyke an age of ca. 314.5 ± 0.5 Ma has been obtained. These ages, together with field relations, allow for a model of a long-standing evolution of an upper crustal magmatic system (~ 5 Ma?), where pulses of magmatic injection and crustal doming alternate with magmatic quietness and erosion. Together with the Altenberg–Teplice Volcanic Complex, located some 10 km to the southeast, the TFC–NBG Complex represents an early post-Variscan magmatic activity in central Europe.
    Description: Technische Universität Bergakademie Freiberg (3135)
    Keywords: ddc:551 ; Single phase caldera evolution ; Caldera wall landslides ; Freiberg gneiss dome ; CA-ID-TIMS zircon dating
    Language: English
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  • 27
    Publication Date: 2023-08-17
    Description: This paper presents radon flux profiles from four regions in Schleswig–Holstein (Northern Germany). Three of these regions are located over deep-rooted tectonic faults or salt diapirs and one is in an area without any tectonic or halokinetic activity, but with steep topography. Contrary to recently published studies on spatial patterns of soil radon gas concentration we measured flux of radon from soil into the atmosphere. All radon devices of each profile were deployed simultaneously to avoid inconsistencies due to strong diurnal variations of radon exhalation. To compare data from different seasons, values had to be normalized. Observed radon flux patterns are apparently related to the mineralogical composition of the Quaternary strata (particularly to the abundance of reddish granite and porphyry), and its grain size (with a flux maximum in well-sorted sand/silt). Minimum radon flux occurs above non-permeable, clay-rich soil layers. Small amounts of water content in the pore space increase radon flux, whereas excessive water content lessens it. Peak flux values, however, are observed over a deep-rooted fault system on the eastern side of Lake Plön, i.e., at the boundary of the Eastholstein Platform and the Eastholstein Trough. Furthermore, high radon flux values are observed in two regions associated with salt diapirism and near-surface halokinetic faults. These regions show frequent local radon flux maxima, which indicate that the uppermost strata above salt diapirs are very inhomogeneous. Deep-rooted increased permeability (effective radon flux depth) or just the boundaries between permeable and impermeable strata appear to concentrate radon flux. In summary, our radon flux profiles are in accordance with the published evidence of low radon concentrations in the “normal” soils of Schleswig–Holstein. However, very high values of radon flux are likely to occur at distinct locations near salt diapirism at depth, boundaries between permeable and impermeable strata, and finally at the tectonically active flanks of the North German Basin.
    Description: Bundesministerium für Wirtschaft und Energie http://dx.doi.org/10.13039/501100006360
    Description: Johannes Gutenberg-Universität Mainz (1030)
    Keywords: ddc:551 ; Radon flux ; Local radon flux maxima ; Permeability ; Quaternary sediments ; Salt tectonics ; Schleswig–Holstein
    Language: English
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