Learning from (small) disasters

In this article, disasters are understood as processes that have different impacts on social routines in terms of scale, scope and duration. The extent of adaptive processes in society can provide the ground for a rough classification of disaster types. Such classification has, on the one hand, practical and analytical advantages. On the other hand, they harbour the danger of overlooking transitions of scale and discourage comprehensive scale-related learning forms. Based on the disaster scale by Fischer (Int J Mass Emerg Disasters 1:91–107, 2003), flash floods in mountain rivers and torrents are described as extreme emergencies or small-town disasters. Three given examples will clearly show that learning rarely takes place within an institutional setting that is subjected to small disasters, because the stakeholder’s focus remains on only one level. Therefore, we propose to implement a system of self-organised and scale-independent learning, so called deutero learning, within the political subsystem. Following a damaging event, participative processes that involve all levels should be initialised. Their task would be to assess the combination of causes and draw conclusions for mitigation measures. An aggregation of these assessments would help the responsible political subsystems to adapt the current natural disasters policy to the changing environmental conditions.     

Description of an aerodynamic levitation apparatus with applications in Earth sciences

Background  

In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO₂-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments.     

A high-resolution sedimentary archive from landslide-dammed Lake Mengda,north-eastern Tibetan Plateau

Lacustrine sediments have been widely used to investigate past climatic and environmental changes on millennial to seasonal time scales. Sedimentary archives of lakes in mountainous regions may also record non-climatic events such as earthquakes. We argue herein that a set of 64 annual laminae couplets reconciles a stratigraphically inconsistent accelerator mass spectrometry (AMS) ¹⁴C chronology in a ~4-m-long sediment core from Lake Mengda, in the north-eastern Tibetan Plateau. The laminations suggest the lake was formed by a large landslide, triggered by the 1927 Gulang earthquake (M = 8.0). The lake sediment sequence can be separated into three units based on lithologic, sedimentary, and isotopic characteristics. Starting from the bottom of the sequence, these are: (1) unweathered, coarse, sandy valley-floor deposits or landslide debris that pre-date the lake, (2) landslide-induced, fine-grained soil or reworked landslide debris with a high organic content, and (3) lacustrine sediments with low organic content and laminations. These annual laminations provide a high-resolution record of anthropogenic and environmental changes during the twentieth century, recording enhanced sediment input associated with two phases of construction activities. The high mean sedimentation rates of up to 4.8 mm year^?1 underscore the potential for reconstructing such distinct sediment pulses in remote, forested, and seemingly undisturbed mountain catchments.     

Present and projected degree days in China from observation,reanalysis and simulations

Degree days are usually defined as the accumulated daily mean temperature varying with the base temperature, and are one of the most important indicators of climate changes. In this study, the present-day and projected changes of four degree days indices from daily mean surface air temperature output simulated by Max Planck Institute, Earth Systems Model of low resolution (MPI-ESM-LR) model are evaluated with the high resolution gridded-observation dataset and two modern reanalyses in China. During 1979–2005, the heating degree days (HDD) and the numbers of HDD (NHDD) have decreased for observation, reanalyses (ERA-Interim and NCEP/NCAR) and model simulations (historical and decadal experiments), consistent with the increasing cooling degree days (CDD) and the numbers of CDD (NCDD). These changes reflect the general warming in China during the past decades. In most cases, ERA-Interim is closer to observation than NCEP/NCAR and model simulations. There are discrepancies between observation, reanalyses and model simulations in the spatial patterns and regional means. The decadal hindcast/forecast simulation performance of MPI-ESM-LR produce warmer than the observed mean temperature in China during the entire period, and the hindcasts forecast a trend lower than the observed. Under different representative concentration pathway (RCP) emissions scenarios, HDD and NHDD show significant decreases, and CDD and NCDD consistently increase during 2006–2100 under RCP8.5, RCP4.5 and RCP2.6, especially before the mid-21 century. More pronounced changes occur under RCP8.5, which is associated with a high rate of radiative forcing. The 20th century runs reflect the sensitivity to the initial conditions, and the uncertainties in terms of the inter-ensemble are small, whereas the long-term trend is well represented with no differences among ensembles.     

Origin and age of ultramafic rocks and gabbros in the southern Puna of Argentina: an alleged Ordovician suture revisited

Ultramafic rocks and gabbros are exposed in the southern Puna (NW Argentina) in tectonic association with continental arc-related Ordovician (volcano) sedimentary successions and granitoids. The origin of this mafic rock suite has been debated for three decades as either representing an Ordovician terrane suture, primitive Ordovician arc-related rocks or relics of the pre-Ordovician basement in tectonic contact with the Ordovician retro-arc basin successions. We present the first U–Pb ages of primary and inherited zircon from gabbros of this mafic–ultramafic assemblage. LA-ICP-MS analyses on cores and rims of these zircon grains yielded a concordia age of 543.4 ± 7.2 Ma for the gabbroic rocks. Other analysed zircons have Mesoproterozoic, and Early Ediacaran core and rim ages indicating that the magmas also assimilated Meso- and Neoproterozoic crustal material prior to final crystallization. The mafic rocks witnessed higher metamorphic grade than associated Ordovician rocks, which are unmetamorphosed or only affected by anchimetamorphism. The gabbros are mostly tholeiitic and enriched in Zr, Th, as well as other incompatible elements and have εNd _t=540Ma ranging from 1.3 to 7.4 with most of the values between 5 and 7. ¹⁴⁷Sm/¹⁴⁴Nd ratios show evidence of weak crustal contamination. The mafic rocks do not reveal any affinity to mid-ocean ridge basalts in their geochemistry but point instead to an emplacement in an active plate margin arc environment. Chromites from ultramafic rocks show typical Ti, Al, Cr#, Fe³⁺ abundances found in magmatic arc rocks. The formation of the gabbros and the associated ultramafic rocks in the southern Argentine Puna is related to the evolution of the margin of the Pampia terrane, including the Puncoviscana basin, during the Late Neoproterozoic and earliest Cambrian. In contrast to previous interpretations, the rocks predate the Ordovician evolution of the Central proto-Andean active margin. Consequently, interpretations assuming these rocks to represent an oceanic terrane suture of Ordovician age have to be dismissed as much as all palaeotectonic models that define Ordovician terranes in the Central Andes based on assumption that the ultramafic rocks and gabbros exposed in the southern Puna mark plate boundaries.     

http://www.sciencedirect.com/science/article/pii/S1674987114000395

The study of fluid inclusions in high-grade rocks is especially challenging as the host minerals have been normally subjected to deformation, recrystallization and fluid-rock interaction so that primary in- clusions, formed at the peak of metamorphism are rare. The larger part of the fluid inclusions found in metamorphic minerals is typically modified during uplift. These late processes may strongly disguise the characteristics of the ＂original＂ peak metamorphic fluid. A detailed microstructural analysis of the host minerals, notably quartz, is therefore indispensable for a proper interpretation of fluid inclusions. Cathodoluminescence （CL） techniques combined with trace element analysis of quartz （EPMA, LA- [CPMS） have shown to be very helpful in deciphering the rock-fluid evolution. Whereas high-grade metamorphic quartz may have relatively high contents of trace elements like Ti and A1, low- temperature re-equilibrated quartz typically shows reduced trace element concentrations. The result- ing microstructures in CL can be basically distinguished in diffusion patterns （along microfractures and grain boundaries）, and secondary quartz formed by dissolution-reprecipitation. Most of these textures are formed during retrograde fluid-controlled processes between ca. 220 and 500 ℃, i.e. the range of semi-brittle deformation （greenschist-facies） and can be correlated with the fluid inclusions. In this way modified and re-trapped fluids can be identified, even when there are no optical features observed under the microscope.     

Spinel-bearing,Al-rich chondrules in two chondrite finds from Roosevelt County,New Mexico: Indicators of nebular and parent body processes

Abstract— Two rare, spinel-bearing, Al-rich chondrules have been identified in new chondrite finds from Roosevelt County, New Mexico—RC 071 (L4) and RC 072 (L5). These chondrules have unusual mineralogies, dominated by highly and asymmetrically zoned, Al-Cr-rich spinels. Two alternatives exist to explain the origin of this zoning—fractional crystallization or metamorphism. It appears that fractional crystallization formed the zoning of the trivalent cations (Al, Cr) and caused a localized depletion in chromites around the large Al-Cr-rich spinels. The origin of the zoning of the divalent cations (Fe, Mg, Zn) is less certain. Diffusive exchange and partitioning of Fe and Mg between olivine and spinel during parent body metamorphism can explain the asymmetric zoning of these elements. Unfortunately, appropriate studies of natural and experimental systems to evaluate the formation of zoning of the divalent cations by fractional crystallization have not yet been conducted. The bulk compositions of the chondrules suggest affinities with the Na-Al-Cr-rich chondrules, as would be expected from the abundance of Al-Cr-rich spinels. Melting of rare and unusual precursors produced the compositions of Na-Al-Cr-rich chondrules, possibly including a spinel-rich precursor enriched in Cr₂O₃ and ZnO. The two chondrules we studied have larger modal abundances of Al-Cr-rich spinels than reported in other Na-Al-Cr-rich chondrules of similar composition, and Al-rich chondrules even more enriched in spinel are reported in the literature. These differences indicate that factors other than bulk composition control the mineralogy of the chondrules. The most important of these factors are the temperature to which the molten chondrule was heated and the cooling rate during crystallization. These two chondrules cooled rapidly from near the liquidus, as indicated by the zoning, occurrence and sizes of spinels, radiating chondrule textures and localized chromite depletions. The range of mineralogies in other Al-rich chondrules of similar composition reflect a range of peak temperatures and cooling rates. We see no reason to believe that this range is fundamentally different from the range of thermal histories experienced by “normal” Fe-Mg-rich chondrules.     

Evaluating sulfur dynamics during storm events for three watersheds in the northeastern USA: a combined hydrological,chemical and isotopic approach

Concerns related to climate change have resulted in an increasing interest in the importance of hydrological events such as droughts in affecting biogeochemical responses of watersheds. The effects of an unusually dry summer in 2002 had a marked impact on the biogeochemistry of three watersheds in the north‐eastern USA. Chemical, isotopic and hydrological responses with particular emphasis on S dynamics were evaluated for Archer Creek (New York), Sleepers River (Vermont) and Cone Pond (New Hampshire) watersheds. From 1 August to 14 September 2002, all three watersheds had very low precipitation (48 to 69 mm) resulting in either very low or no discharge (mean 0·015, 0·15 and 0·000 mm day^?1 for Archer Creek, Sleepers River and Cone Pond, respectively). From 15 September to 31 October 2002, there was a substantial increase in precipitation totals (212, 246 and 198 mm, respectively) with increased discharge. Archer Creek was characterized by a large range of SO₄^2? concentrations (152 to 389 µeq L^?1, mean = 273 µeq L^?1) and also exhibited the greatest range in δ³⁴S values of SO₄^2? (?1·4 to 8·8 ‰ ). Sleepers River's SO₄^2? concentrations ranged from 136 to 243 µeq L^?1 (mean = 167 µeq L^?1) and δ³⁴S values of SO₄^2? ranged from 4·0 to 9·0 ‰ . Cone Pond's SO₄^2? concentrations (126–187 µeq L^?1, mean = 154 µeq L^?1) and δ³⁴S values (2·4 to 4·3 ‰ ) had the smallest ranges of the three watersheds. The range and mean of δ¹⁸O‐SO₄^2? values for Archer Creek and Cone Pond were similar (3·0 to 8·9 ‰ , mean = 4·5 ‰ ; 3·9 to 6·3 ‰ , mean = 4·9 ‰ ; respectively) while δ¹⁸O‐SO₄^2? values for Sleepers River covered a larger range with a lower mean (1·2 to 10·0 ‰ , mean = 2·5). The difference in Sleepers River chemical and isotopic responses was attributed to weathering reactions contributing SO₄^2?. For Archer Creek wetland areas containing previously reduced S compounds that were reoxidized to SO₄^2? probably provided a substantial source of S. Cone Pond had limited internal S sources and less chemical or isotopic response to storms. Differences among the three watersheds in S biogeochemical responses during these storm events were attributed to differences in S mineral weathering contributions, hydrological pathways and landscape features. Further evaluations of differences and similarities in biogeochemical and hydrological responses among watersheds are needed to predict the impacts of climate change. Copyright © 2008 John Wiley & Sons, Ltd.     

Polarization and brightness opposition effects for the E-type Asteroid 64 Angelina

We present new polarimetric and photometric observations of the high-albedo Asteroid 64 Angelina in the UBVRI wavebands at phase angles ranging from 0.43° to 13.02° during oppositions in 1995, 1999, and 2000/2001. The polarization opposition effect has been observed in the form of a sharp peak of negative polarization with amplitude of about −0.4% centered at αmin≈1.8°, which is superimposed on the regular negative polarization branch. The amplitude of the polarization opposition effect appears to be apparition-dependent. Our photometric data confirm the early detected by Harris et al. [1989. Phase relations of high-albedo asteroids: The unusual opposition brightening of 44 Nysa and 64 Angelina. Icarus 81, 365-374] of a very strong and unusually narrow opposition spike, i.e., brightness opposition effect, for Angelina. Thus, 64 Angelina is the first asteroid for which both the polarization opposition effect and the brightness opposition effect have been detected. We observed that the polarization opposition effect as well as the regular negative polarization branch depends on the wavelength of scattered light, but in different manners. In addition, the colors B-V and V-R show little phase-angle dependence, while the color U-B increases with increasing phase angle, thus indicating that the amplitude of the brightness opposition effect is larger in the U band and almost the same in the B, V, and R bands. It appears that all colors indices begin to increase with decreasing phase angle to zero. The composite lightcurve computed with a period of 8.752 h has amplitude of 0.13 magnitude.