A petrological and geochemical study on time-series samples from Klyuchevskoy volcano,Kamchatka arc

To understand the generation and evolution of mafic magmas from Klyuchevskoy volcano in the Kamchatka arc, which is one of the most active arc volcanoes on Earth, a petrological and geochemical study was carried out on time-series samples from the volcano. The eruptive products show significant variations in their whole-rock compositions (52.0–55.5 wt.% SiO₂), and they have been divided into high-Mg basalts and high-Al andesites. In the high-Mg basalts, lower-K and higher-K primitive samples (>9 wt.% MgO) are present, and their petrological features indicate that they may represent primary or near-primary magmas. Slab-derived fluids that induced generation of the lower-K basaltic magmas were less enriched in melt component than those associated with the higher-K basaltic magmas, and the fluids are likely to have been released from the subducting slab at shallower levels for the lower-K basaltic magmas than for higher-K basaltic magmas. Analyses using multicomponent thermodynamics indicates that the lower-K primary magma was generated by ~13% melting of a source mantle with ~0.7 wt.% H₂O at 1245–1260?°C and ~1.9 GPa. During most of the evolution of the volcano, the lower-K basaltic magmas were dominant; the higher-K primitive magma first appeared in AD 1932. In AD 1937–1938, both the lower-K and higher-K primitive magmas erupted, which implies that the two types of primary magmas were present simultaneously and independently beneath the volcano. The higher-K basaltic magmas evolved progressively into high-Al andesite magmas in a magma chamber in the middle crust from AD 1932 to ~AD 1960. Since then, relatively primitive magma has been injected continuously into the magma chamber, which has resulted in the systematic increase of the MgO contents of erupted materials with ages from ~AD 1960 to present.     

Flood‐plain responses to contemporary climate change in small High‐Arctic basins (Svalbard,Norway)

Changes in the supply of water and sediment to high‐latitude rivers related to contemporary climate change and glacier fluctuations largely determine the activity of fluvial processes. This study reconstructs fluvial dynamics since the end of the Little Ice Age (LIA) in two small, partially glaciated basins in the southern part of Spitsbergen, Svalbard Archipelago. We use a combination of aerial photograph interpretation, field mapping and dendrochronological analysis. Sequences of abandoned channels and glacifluvial terraces are distinctly visible in middle and lower parts of the Brattegg and Arie basins in this area. The advance of glaciers during the LIA in the upper part of the basins led to the development of a braiding pattern and to channel aggradation corresponding to the highest glacifluvial levels. The decreasing activity of these braidplains occurred at the turn of the 19th and 20th centuries, immediately prior to a significant incision period. A second generation of braided channels developed during the first half of the 20th century. Ice‐marginal lake development, less input of fine‐grained sediment to the river channel, and fast incision began from the second half of the 20th century onward. During the last two decades, the main fluvial response to the climatic warming has been contraction of flow within a narrower channel and the abandonment of braidplains. The increased lateral erosion and rate of downcutting and the formation of the most downstream reaches of the modern valley bottom occurred in the 1980s and 1990s. This process was intensified under flood conditions generated by extreme rainfall events. These micro‐scale (small partially glaciated basins) observations concerning the changes of the activity of fluvial processes since the end of LIA may be helpful for the reconstruction of past fluvial changes over longer time scales.     

Nonlinear Evolution of Kinetic Alfvén Waves and Filament Formation

The transfer of wave energy to plasma energy is a very crucial issue in coronal holes and helmet streamer regions. Mixed mode Alfvén waves, also known as kinetic Alfvén wave (KAW) can play an important role in the energization of the plasma particles because of their potential ability to heat and accelerate the plasma particles via Landau damping. This paper presents an investigation of the growth of a Gaussian perturbation on a non-uniform kinetic Alfvén wave having Gaussian wave front. The effect of the nonlinear coupling between the main KAW and the perturbation has been studied. The dynamical equations for the field of the main KAW and the perturbation have been established and their semi-analytical solution has been obtained in the low (β≪ m_e/m_i≪ 1) and the high (β≫ m_e/m_i≪ 1) β cases. The critical field of the main KAW and the perturbation has been evaluated. Nonlinear evolution of the main KAW and the perturbation into the filamentary structures and its dependence on various parameters of the solar wind and the solar corona have been investigated in detail. These filamentary structures can act as a source for the particle acceleration by wave particle interaction because the KAWs are mixed modes and Landau damping is possible. Especially, in the solar corona, the low β and the high β cases could correspond to the coronal holes and the helmet streamer. The presence of the primary and the secondary filaments of the perturbation may change the spectrum of the Alfvénic turbulence in the solar wind.     

Flux monitoring at 327 MHz during SL9-Jupiter collision

Jupiter flux at 327 MHz was monitored using the Ooty radio telescope from July 12th to July 29th during the collision of comet Shoemaker-Levi 9 with Jupiter. Flux was found to increase steadily from July 17th to July 26th by ∼ 2–5 Jy, after which it declined to its pre-event value. The comparison of 327 MHz observations with those at 840 MHz and 2240 MHz indicates that the enhancement was mainly due to the increased synchrotron emission and the contribution of thermal emission was very small at metric-decimetric frequencies. The enhancement in radio emission was found to be more at 840 MHz than at 327 or 2240 MHz. The steepening of the spectrum between 327 and 840 MHz as well as between 2240 and 840 MHz was also noted.     

An application of Markov Chain Model for wet and dry spell probabilities at Juba in Southern Sudan

The theoretical probabilities of wet and dry spells derived from the Markov Chain Model were found to fit very closely the observed probabilities of various sequence lengths at Juba, S Sudan. Monthly variation in the probability values does not seem to follow a secular trend. Anomogram relating observed sequence length frequency of wet and dry spells versus those computed by Markov model is presented.     

Delineation of floodplains of streams to combat natural (flood) hazard in an urbanized watershed

During urban development, the land surface is changed from undisturbed soils with natural vegetative cover to disturbed soils, managed landscapes, and built materials [2]. The change in land uses causes the stormwater runoff from impervious areas to be as much as 16 times higher than from natural areas [5] which implies increase of frequency of local flooding and more contribution to the streams carrying urbanized runoff. The main streams in the periphery of city Chandigarh, India are Patiali ki Rao and Sukhna Choe. This study focuses on the identification and development of a real time model for prediction of increase in stormwater runoff to the streams and within the watershed of Chandigarh due to urbanization. The study has undertaken hydraulic modeling of Sukhna Choe using United States Army Corps of Engineers Hydraulic Engineering Centre River Analysis System (HEC-RAS) to understand the urgent need of control of stormwater runoff to deal with flooding issues of the city. It has been concluded from this study that the condition of streams has been deteriorating from past to present to future condition of development and the predicted HEC-RAS water surface elevations can be put into effect to plan further development in the city.     

Adaptive state estimation of groundwater contaminant boundary input flux in a 2-dimensional aquifer

In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location.     

Groundwater aggressiveness assessment according to EN 206-1: data,methods and application on groundwater in the Horna Nitra basin,Slovakia

The history of groundwater aggressiveness evaluation procedures applied in the Slovak Republic is summarized and compared with the newly adopted European technical standard STN EN 206-1. The methodology of data acquiring and processing for groundwater aggressiveness evaluation was proposed. The procedure included basic principles of data mining, requested number of chemical analyses and ways of groundwater aggressiveness assessment. Ways of results interpretation and graphical visualization were proposed, too. The procedure was applied in the area of the Horna Nitra in Slovakia. A total number of 953 groundwater analyses were used to assess the groundwater aggressiveness. The resulting map of zoning comprised eight groundwater aggressiveness zones. Zones with the non-aggressive degree (X0) groundwater to moderately aggressive degree (XA2) were delineated. The aggressiveness was caused mainly by presence of aggressive carbon dioxide (depending on the rock type in the area) and by lowered pH values in association with increased sulfate contents in areas of brown coal mining activities and in heavy industrialized areas. The compilation of a locality map was proposed, where for each municipality type and degree of aggressiveness is assessed. It should serve to local authorities as background information within the decision-making process connected to the permission of construction work.     

Determination of Iodine in Thirty Two International Geochemical Reference Materials

Thirty two geochemical reference samples have been analysed for their iodine contents by a pyrohydrolysis extraction technique, followed by colourimetry. In spite of the existence of few reported values for iodine, limiting comparison with results from this study, the four available "reference" values show good agreement with the work reported here.