Showing papers in "Earth Science Research in 2013"
TL;DR: In this paper, the extent and degree of damage caused to the floristic diversity of the Sundarbans by the tropical cyclone Sidr in 15 November 2007 was quantified.
Abstract: The Sundarbans - the world’s largest single block of tidal halophytic mangrove forest situated at the southwest of Bangladesh, plays a vital role in maintaining environmental sustainability of the country and the world in general. This study identified and quantified the extent and degree of damage caused to the floristic diversity of the Sundarbans by the tropical cyclone Sidr in 15 November 2007. It also quantified the extent and rate of the post-cyclone regeneration in the damaged flora. Unsupervised classification - ISODATA and the normalized difference vegetation index (NDVI) were carried out over a temporal series of 2007-2010 on four Landsat 7 Enhanced Thematic Mapper Plus (ETM +) images for the months of February. Land change analysis from the classification results show that three important floristic taxa - Heritiera fomes (Sundari), Excoecaria agallocha (Gewa) and Sonneratia apetala (Kewra) have been significantly affected by the cyclone. NDVI analysis indicates that 45% area of the Bangladesh’s part of the Sundarbans (approximately 2500 sq.km) was affected due to the cyclone action. Results further indicated that the average rate of post-cyclone floristic growth in 2009-2010 is four times higher than the average rate in 2008-2009. Thus the study identified a temporary loss of the diversity (in terms of relative abundance) in the affected three floristic taxa of the Sundarbans after that severe exogenous perturbation; which took three years to regenerate. Moreover, it showed the higher efficiency and promptness of remote sensing techniques in similar cases than the ground data based studies.
53 citations
TL;DR: In this article, the authors describe the development of an oil spill modeling system that can be used for both real-time response, forecast simulations and probabilistic risk analysis based on climatological wind and ocean current data.
Abstract: This paper describes the development of an oil spill modeling system that is operational on a global scale and can be used for both real-time response, forecast simulations and probabilistic risk analysis based on climatological wind and ocean current data. For ocean and estuarine spills, the system makes use of the General NOAA Operational Modeling Environment (GNOME) oil spill model, Trajectory Analysis Planner and the Automated Data Inquiry for Oil Spills weathering model. Hydrodynamic and meteorological data is obtained from the US Navy and National Oceanic and Atmospheric Administration. Data access is provided through the Naval Oceanographic Office, the Fleet Numerical Meteorological and Oceanographic Center and the GNOME Online Oceanographic Data Server. For riverine spills, the GeoSpatial Stream Flow Model and the Incident Command Tool for Drinking Water Protection are used to respectively, build river networks with associated flows and velocities and, transport and disperse oil spill contamination downstream. Case study examples are presented for both forecast simulations and probabilistic risk analysis.
30 citations
TL;DR: In this paper, the authors examined the trend in rainfall patterns over a period of fifty years i.e. 1960-2009 so as to know the effect of rainfall variability in the occurrence of drought and flood in the Sudano- Sahelian Ecological Zone of Nigeria comprising Kebbi, Sokoto, Kano, Jigawa, Yobe, Katsina and Borno States.
Abstract: The trends of rainfall have a great impact on the hydrologic cycle and therefore affect both the quality and quantity of water resources. There is therefore the need to examine the trend of rainfall in Sudano- Sahelian Ecological Zone of Nigeria comprising Kebbi, Sokoto, Kano, Jigawa, Yobe, Katsina and Borno States. The study examined the trend in rainfall patterns over a period of fifty years i.e. 1960-2009 so as to know the effect of rainfall variability in the occurrence of drought and flood in the zone. The study makes use of rainfall data, which were collected from the Nigeria Meteorological Agency, Oshodi, Lagos. The Standardized Anomaly Index was used to test for fluctuations in rainfall while the Spearman Rank Statistics was used to look for the trend in rainfall. The study revealed that there was a downward trend in rainfall amounts in the 1970s and 1980s which was responsible for the drought episodes of 1972/73 and 1980 and an upward trend in the amount of rainfall between 1990 and 2009 which accounts for the flood episodes in Northern Nigeria. There is a general increase of 5% in annual rainfall over the entire fifty years under study in the zone due to an observable 5.4% increase in mean rain-days and 4% increase in the rains that fall as heavy rain, which was found to be responsible for the increase in runoff, ground water recharge and the frequent flood episodes in the zone. Based on this study, it can therefore be concluded that the Sudano-Sahelian Ecological Zone of Nigeria has been experiencing an increase in the annual rainfall with little recession in 1970s and 1980s, the rainfall has been very high and this has significant consequences on water resources in the zone with the zone becoming prone to flood events, erosion and sedimentation which may have adverse effect on both quantity and quality of water available for human consumption. The study therefore recommends that a study of the interactions between the ecosystems due to the distortion in the hydrology of the zone should be carried out among others.
27 citations
TL;DR: In this article, the activity concentrations of 238U, 232Th and 40K in soil samples from different soil types has been collected in the state of Perak, Malaysia using a high-resolution co-axial HPGe gamma ray spectrometry system.
Abstract: The activity concentrations of 238U, 232Th and 40K in soil samples from different soil types has been collected in the state of Perak, Malaysia. The samples were determined using a high resolution co-axial HPGe gamma ray spectrometry system. Mean values for 238U, 232Th and 40K activity concentrations were found to be (127 ± 97) Bq kg-1, (304 ± 28) Bq kg-1, and (302 ± 29) Bq kg-1 respectively. The highest concentration of 238U and 232Th was found for soil of the types Paleudults-Hapludults and 40K for the typic Aeric Tropaquepts. The external hazard values (Hex) are between 0.35 and 3.07. Soil type typic Paleudults and typic Hapludults have a hazard index, Hex value which is greater than 2, and the rest of the soil types (ten soil types) have Hex values between 1 to 2. The concentrations of 238U and 232Th in soil samples in the study area are higher than the reference value.
14 citations
TL;DR: An integrated approach to the study of the structural patterns and seismic attributes was carried out on the Z-field using a 3D seismic data covering approximately 56 Km2 of western belt of the Niger Delta, checkshot data for well to seismic tie and log information for six wells from the field as mentioned in this paper.
Abstract: An integrated approach to the study of the structural patterns and seismic attributes was carried out on the Z-field using a 3D seismic data covering approximately 56 Km2 of western belt of the Niger Delta, checkshot data for well to seismic tie and log information for six wells from the field. This study aimed at investigating the available prospects, the responses of the basic seismic attributes to structural and stratigraphic elements within the study area. In all, six hydrocarbon bearing levels were delineated from well logs and correlated across the field. These horizons were analysed and petrophysical parameters estimated. An integration of well and seismic data was done by applying a time-depth relationship to identify where the hydrocarbon bearing sands from well posts on the seismic lines. These studies revealed two major regional growth faults (F1 and F5) dipping in the NE-SW directions and crestal faults (F4) dipping in the northern direction. The north dipping crestal fault F4 is responsible for holding the hydrocarbon in the proven closure A. The northernmost regional growth fault F1 is responsible for trapping the hydrocarbon in the prospect closure B in the north eastern part of the field. The closure C prospect is a four way dip closure to the spill point but becomes fault assisted on regional growth faults F1 and F5 at deeper levels. The trapping mechanism identified from our interpretation indicates that the field is characterized mostly by fault assisted closures and a few four way closures. The fault zones are identified by distinct displacement of walls and amplitude distortions towards the fault zones identified on the seismic sections and the extracted amplitude maps. At the south-western part of the field, using only seismic Stratigraphic approach, a part of fault F5 was too subtle to be identified, and this may lead to missing out on the potentials of the identified closure C prospect. Thus, where conventional seismic interpretation has failed, seismic attribute analysis complements.
13 citations
TL;DR: In this paper, the weathering of some granitic rocks in the West Region of Cameroon (Central Africa) was examined by X-ray diffraction (XRD) and Xray fluorescence Spectrometer (XRF) in conjunction with Scanning Electron Microscopy (SEM).
Abstract: The weathering of some granitic rocks in the West Region of Cameroon (Central Africa) was examined by X-ray diffraction (XRD) and X-ray fluorescence Spectrometer (XRF) in conjunction with Scanning Electron Microscopy (SEM). Kaolinite and illite were the most predominant weathering products whereas gibbsite, goethite and maghemite were also found in small amounts; only residual quantities of quartz and potassium feldspar were observed. The geochemical study shows the mobility of major elements during the progressive kaolinization of granitic rocks. The main trend is the loss of elements, with high losses of CaO, Na2O and MgO, slight losses of SiO2 while Al2O3 and K2O appear to increase with weathering intensity. Chemical index of alteration (CIA) shows a high value (68-95%). The scanning electron microscope analysis reveals the existence of several surface features that reflect the effect of mainly chemical actions on the quartz and K-feldspar grains. Quartz and K-feldspar crystals from kaolinized granitic rocks show low to very high chemical etching attributed to weathering under moderate to severe environmental conditions such as low pH, high temperature and humidity and extreme leaching typical of tropical climatic conditions. Etched pit densities on quartz surfaces increase with weathering, as a result of increasing silica concentrations in pore fluids.
10 citations
TL;DR: A rich Bolivina assemblage occurs in the onshore Tonjor-1 well of the Niger Delta; eighteen species are reported for the first time as mentioned in this paper, which permits the subdivision of the succession into one taxon and interval range zones respectively and two concurrent subzones.
Abstract: A rich Bolivina assemblage occurs in the onshore Tonjor-1 well of Niger Delta; eighteen species are reported for the first time. Some index planktonic foraminifera allowed a late Early Eocene age assignation, in addition to some Bolivina species that are known to be restricted to samples from the studied intervals. The Bolivina species recovered permits the subdivision of the succession into one taxon and interval range zones respectively and two concurrent subzones. The interval zone is Bolivina ottaensis Reyment; while the taxon zone is Bolivina attenuata Cushman. The concurrent sub-zones are Bolivina foliacea Sellier de Civrieux and Bolivina jacksonensis Cushman and Applin. The planktonic foraminifers associated with the bolivinids are namely, Acarinina pentacamerata (subbotina), A. psuedotopilensis (Subbotina), Pseudohastigerina wilcoxensis (Cushman and Ponton) and Globigerina officinalis Subbotina which permits the late Early Eocene dating of these zones. Stratigraphic diversity variation of the bolivinds allowed the recognition of late Early Eocene marine transgression which correlates with the global timing of Early Eocene transgression. The presence of strong costae, and larger test suggests a deposition in a well oxygenated slope to bathyal environment.
9 citations
TL;DR: In this paper, the results obtained show that stabilization by the addition of salts modifies the physico-chemical characteristics of soil and the results are quite satisfactory in significantly reducing the phenomenon of swelling, as regards the effect of salt on the swelling pressure it varies from salt to another and concentration to another.
Abstract: Swelling and shrinkage of expansive soils occur mainly due to a change in the moisture regime and pose serious problems to foundations causing damage to structures founded on them. However, construction on this type of soil requires a good companion for the recognition of identification, characterization of their swelling potential and Treatment processing. In this work we are interested by two aspects: 1) The first is on the tests recommended for the identification of diferants expansive soils in the region of Tlemcen in the north western Algeria. 2) The second is to perform stabilization tests on remolded samples by salts (KCl Potassium Chloride, Magnesium Chloride MgCl2) with deffrants concentrations and see their influence on physic-chemical parameters and swelling. The results obtained show that stabilization by the addition of salts modifies the physico-chemical characteristics of soil and the results are quite satisfactory in significantly reducing the phenomenon of swelling, as regards the effect of salt on the swelling pressure it varies from salt to another and concentration to another.
8 citations
TL;DR: In this paper, the geochemistry, origin and reserve evaluation of the phosphate in the Kasarwasa Prospect have been undertaken, which indicates P2O5 values of 29.23-34.2%.
Abstract: Sedimentary phosphate occurs as thin nodular beds and nodular disseminations in the Dange Formation (Paleocene) of Sokoto basin in north western Nigeria. The geochemistry, origin and reserve evaluation of the phosphate in the Kasarwasa Prospect have been undertaken. Analysis indicates P2O5 values of 29.23-34.2%. The nodules are suitable for the production of fertilizers on the basis of major elements and P2O5 values. The nodules also have direct soil application potential. Origin of the nodules was from direct precipitation as microsporite which was later reworked. The origin was associated with the trans-Saharan Tethys Sea transgression in North Africa. A nodule reserve in the Kasarwasa Prospect was evaluated from 46 pits. Tonnages per acre range from 91.14 to 3,260.09 which indicate only two hectares are economic while 22 are non-economic deposits.
7 citations
TL;DR: In this article, the authors investigated the relationship between local atmospheric circulation and moisture flux divergence for the case of rainfall over south of Iran during December 10-13, 1995 and revealed the main moisture source flux which feeds in the rain fall weather system.
Abstract: During December 10-13, 1995 a destructive flood occurred over the south part of Iran resulting from the intensive rainfall causing the social and economical damages over that area. This study intends to reveal the main moisture source flux which feeds in the rain fall weather system. The precipitation amount over the study area is four times greater than normal mean in December. The relationships between local atmospheric circulation and moisture flux divergence is investigated for this case of rainfall over south of Iran. The data used in these study includes rainfall data, from data processing center of IRIMO (Iran meteorological organization) and reanalysis daily data at every six hours interval for the same period and eight levels of NCEP-NCAR, with resolution 2.5 degrees in 0-80 E and 10-60 N domain. The high pressure circulation over the North East of Arabian peninsula at surface to 700hPa coupled with trough over the East of Mediterranean and west of the Red sea, transfer sufficient moisture in low levels of the troposphere from west of Indian ocean (Oman and Arabian seas), Aden gulf and Red sea to the center and North of Arabia and south of Iran. The average of perceptible water content in all troposphere level (1000-300 hPa) that comes from the above mentioned region to the South West and south of Iran is about (6-8) 10 -3 kg/m 2 s -1 . The most divergence of moisture flux in the lower level is from the west of the Indian Ocean while the source of moisture in middle and higher levels are from Aden gulf and the Red sea.
7 citations
TL;DR: In this article, the authors used Monte Carlo simulation (MCS) to calculate the probability of failure to liquefaction based on standard penetration test SPT in which soil's parameters are modeled by random variables.
Abstract: Soil liquefaction is the source of several major damages during earthquakes on the material and human level. Several authors have studied the probability of liquefaction by in situ and laboratory tests and several models have been proposed to calculate the safety factor. But because of various uncertainties in performance function parameters, we adopted in this paper a reliability analysis that considers uncertainties of parameters and model uncertainties. We used the Monte Carlo simulation (MCS) to calculate the probability of failure to liquefaction based on standard penetration test SPT which soil's parameters are modeled by random variables. The reliability results obtained show that the variability of soil’s parameters has an important impact on the probability of liquefaction. A sensitivity analysis based on the coefficient of variation is presented to see the effect of each random variable on the probability of liquefaction.
TL;DR: In this paper, the gastric bioaccessibility of Pb was investigated in soils and sediments from five villages in the Anka area of north-western Nigeria which has been adversely affected by artisanal mining of gold from lead-rich ores.
Abstract: The gastric bioaccessibility of Pb was investigated in soils and sediments from five villages in the Anka area of north-western Nigeria which has been adversely affected by artisanal mining of gold from lead-rich ores. In vitro bioaccessibility experiments were used to determine the extractability of Pb in order to evaluate the human health risk, especially to children below the age of five. The concentration of Pb in the simulated gastric fluids ranges from ~ 198 to 41740 µg.g-1 (mean, 9732 µg.g-1), with corresponding human bioaccessible fraction between ~ 29 and 100% (mean, ~ 60%). Chemical daily intake (CDI, µg/Kg/Day) values of between 111 and 41587 are generally very high compared to the tolerable daily intake (TDI) of ~ 3.6 µg Pb/Kg/Day. The high bioaccessibility is a result of high total concentration of Pb and the presence of highly soluble carbonate and oxide minerals in the ores. These results point to the very adverse health effects likely to result from incidental hand-to-mouth ingestion of soils by children in the affected villages. The results further show that the low pH of gastric juices enhances the extraction of Pb. Given the likelihood of sub-nutrition in the affected communities, characterized by skipping of meals, which can result in lowering of the pH over extended periods, the risk of Pb poisoning is further increased. This study was based on a hand-to-mouth ingestion scenario alone, but as other exposure routes, such as eating improperly washed vegetables and inhalation of dust are possible, the risk might even be higher. This, along with the fate of extracted Pb in the intestinal environment may need to be evaluated in order to fully quantify the bioavailability of Pb in the area.
TL;DR: The results of the analysis for analyzed core samples from these boreholes within Gombe Formation shows that the samples in boreholes BA-7 and BA-16 contain Type II kerogen while those from borehole BA-17 contain Type III kerogen as discussed by the authors.
Abstract: Gombe Formation is a heterogeneous sequence within the Upper Benue Trough consisting principally of shales with sands, clays and intercalations of coal. It is over 600 m thick maximally in some parts of the sub-basin and has been dated Maastritchtian. Fifteen (15) core samples from 3 boreholes (BA-7, BA-16 and BA-17) dug around the Maiganga Coal Mine have been studied geochemically using the Rock-Eval 6 method with the principal aim of evaluating their potential as possible source rocks for petroleum. The results of the Rock-Eval analysis for analyzed core samples from these boreholes within Gombe Formation shows that the samples in boreholes BA-7 and BA-16 contain Type II kerogen while those from borehole BA-17 contain Type III kerogen, and that the samples from boreholes BA-7 and BA-16 have very good generative potential while those from borehole BA-17 have good to very good potential. This study also reveals that the analyzed samples especially those from boreholes BA-7 and BA-16 may constitute good source rocks if the burial depth is sufficient. The Rock-Eval Tmax data available for thermal maturity assessment of the samples suggest that the analyzed samples from the three boreholes are thermally immature. This assessment is consistent with the immaturity status of their coeval Formations (Pindiga and Gongila Formations) in other part of the Benue Trough, suggesting that these contemporaneous Formations may be related in depth and/or have experienced similar geothermal gradient. It is therefore recommended that the thermal maturity of the analyzed samples from the three boreholes be re-evaluated by other thermal maturity indices such as vitrinite reflectance measurement and biomarker evaluation in order to further authenticate the maturity status of the Formation.
TL;DR: 2D vector map watermarking for GIS digital map is presented based on a new water marking concept called intelligentWatermarking to protect the wide range of digital maps data transmitted via computer networks.
Abstract: GIS (Geographic Information System) has been used in military and commercial applications for many years. The data of GIS are very expensive. So, it is very important to prevent any illegal use of these data. Digital watermarking can provide potential solution. As we know, in most of the applications of digital watermarking, the watermark is used to protect the copyright of digital product. In the other word, the product (cover) is important. According to this fact, we presented 2D vector map watermarking for GIS digital map based on a new watermarking concept called intelligent watermarking. The need of this concept is increased in the last years to protect the wide range of digital maps data transmitted via computer networks. Briefly, the scheme depends on the feature of the cover. The embedding of the watermark can be done in several steps. First extracting some features from the original digital vector map. Second combine these features with external watermark in order to get the intelligent watermark. Third embed the intelligent watermark in the vector map to get the watermarked vector map. The extracting of the watermark can be done in several steps. First, extract the intelligent watermark from the watermarked digital vector map. Second decompose the intelligent watermark into features and external watermark. Third reverse the extracted features to features of watermarked vector map. So, if the watermarked vector map is attacked, this watermarked vector map will be distorted, otherwise will not be distorted. Our proposed scheme can be applied in all the other media.
TL;DR: A taxonomic study of the ostracod assemblages has been undertaken in this paper, with the majority of them being placed in open nomenclature, indicating their affinity to the coeval assembls from Sierra Leone, Benin Republic and Gabon.
Abstract: Ditch cuttings from seven wells and foraminiferal slides of three wells have been analyzed for diatoms, ostracods and radiolaria. The wells penetrated Eocene to Miocene strata in the Niger delta. A taxonomic study of the ostracod assemblages has been undertaken. The paleobiogeography of the ostracods indicates their affinity to the coeval assemblages from Sierra Leone, Benin Republic and Gabon. Paleoecological interpretations of the ostracod assemblages suggest inner to middle neritic depositional environments. Diatoms and radiolarians were identified, with the majority of them being placed in open nomenclature. This was a pilot study to determine the stratigraphical and paleoenvironmental potential of the three fossil groups in the Niger delta.
TL;DR: In this article, the engineering properties of soils recovered along a road alignment route (right-of-way) and borrow pits of a 30 km road in the South Eastern Niger Delta area, Nigeria were assessed for utilization as highway pavement earth materials.
Abstract: Engineering properties of soils recovered along a road alignment route (right-of-way) and borrow pits of a 30 km road in the South-Eastern Niger Delta area, Nigeria were assessed for utilization as highway pavement earth materials. Laboratory soil tests conducted included the natural moisture content, grain size distribution analysis, consistency limits, standard proctor compaction and California bearing ratio (CBR). About thirty-five (35) soil samples were retrieved from the fifteen (15) boreholes and examined. Results show that all identified and examined soil samples from the borings along the road route and the borrow pits classified as A- 3, A-2-4 and A-2-6 are excellent sub-grade, good fill and sub-base materials. However, none of the soil types meet the engineering requirements for use as base course. Earth materials comprising overburden of clayey sands, silty sands and sandfills (previously used as sub-grades) along the Ahoada-Upatabo-Oyigba-Ebiriba-Ombor 30 km. road in South-eastern Niger Delta were evaluated for highway pavement construction. The results are presented in this paper. The objective of the study was to examine the appropriateness of these soils for the purpose of pavement design and construction as sub-grades, sub-base and base course materials. Previous related studies in the area include works by (1-5).
TL;DR: In this article, the authors describe the structure and formation process of Mount Kakoulima by means of geological field observations, showing that it is a stratified solid rock, formed with the result of some magma injections in some intrusive phases.
Abstract: The interest generated by mafic-ultramafic rocks is justified by the fact that their structure and formational processes not only have scientific importance but also can lead to metal concentrations, making them economically viable. Located 50 km north-east of Conakry, Guinea’s capital, Mount Kakoulima has long been one of the mafic-ultramafic rock areas of the world but has yet to be exploited; thus limited data have been published concerning it. The goal of this investigation is to describe the structure and formation process of Mount Kakoulima by means of geological field observations. The findings indicate that Mount Kakoulima is a stratified solid rock, formed with the result of some magma injections in some intrusive phases. With a Lithological sequence progressing from peridotite (dunite) to pyroxenite to extensive gabbro. The result will improve the understanding of geological processes on Mount Kakoulima to guide future surveys on mineral ores in the scientific and academic community for research and studies in the field of earth sciences.
TL;DR: In this article, the authors applied reduction-to-pole to the aeromagnetic data of Ilesha southwest, Nigeria with sheet number 243 and determined the depth to top for very thin body, intermediate body and very thick body using the Peter's half slope method.
Abstract: The slope method is one of the earliest magnetic depth estimate techniques which can determine the depth to the top of magnetic basement. Reduction-to-pole was applied to the aeromagnetic data of Ilesha southwest, Nigeria with sheet number 243. The data which was originally partitioned into different profiles was later processed to generate reduction-to-pole graph. The contour map of the study area was partitioned into four quadrants, with the highest magnetic anomaly occurring at the third quadrant (southwest region), while the northwest region has the lowest magnetic anomaly. The depth to top for very thin body, intermediate body and very thick body was determined using the Peter’s half slope method. These values range between 2.40 km and 10.60 km for the very thin body, 1.8 km to 7.93 km for the intermediate body and 1.41 km to 6.35 km for the very thick body. These results revealed the extent of the depth of the source of the magnetic anomaly that was produced by the aeromagnetic data of the study area.
TL;DR: In this paper, the authors investigated whether different cardinal directions which affect temperature and humidity of rocks have an effect on bdelloid diversity or not by examining 10 cm 2 of lichen samples which was collected from the west, east, north sides and from top of a rock covered with Lecanora muralis (lichen).
Abstract: Notwithstanding that there are ongoing studies being carried out on various groups of microorganisms for determining diversity pattern of microorganisms (smaller than 2 mm), they mostly focus on bacteria. Bdelloid rotifers are another group of microorganisms sized between 77-1500 μm. In this study, we investigated whether different cardinal directions which affect temperature and humidity of rocks have an effect on bdelloid diversity or not by examining bdelloid rotifers living on 10 cm 2 of lichen samples which was collected from the west, east, north sides and from top of a rock covered with Lecanora muralis (lichen). The results showed that species richness, species composition and abundance of bdelloid rotifers are affected by different cardinal directions. KeywordsSpecies Richness; Abundance; Diversity Pattern; Microorganism
TL;DR: In this article, the authors present descriptive, petrographic, and geochemical criteria to distinguish between such cemented internal sediment and true cements, and develop genetic models to account for both the development of internal sediment (i.e., sediment which infiltrated the gravel skeleton after deposition) the source of which is assumed to be the fine suspended fraction of glacier meltwater.
Abstract: Quaternary glacial gravels are often partly cemented by carbonates, and comparable cements are also known from pre-Quaternary glacigenic rock sections. These cemented zones are of importance e.g. for applied geology or paleoclimate studies but have hitherto not been studied systematically. This article reports examples from the Alpine foreland of Northern Switzerland. It is based on geotechnical reports, field observations, petrographic and stable isotope analyses. It will be shown that carbonate cements in glacial gravel are of heterogeneous origin and that many of them should rather be considered as cemented internal sediment (i.e., sediment which infiltrated the gravel skeleton after deposition) the source of which is assumed to be the fine suspended fraction of glacier meltwater. This paper presents descriptive, petrographic, and geochemical criteria to distinguish between such cemented internal sediment and true cements, and develops genetic models to account for both the development of internal sediment and of true cements. It is suggested that the use of these models will help to better predict the spatial geometry of cemented zones in glacial gravel. Finally, we will discuss some consequences for the study of pre-Quaternary glacigenic deposits.
TL;DR: In this paper, the authors present evidence that climate change has the potential to influence land-cover patterns over space and time and land change models can compliment climate models to provide better understanding of the climate and land cover relations at local levels.
Abstract: Understanding the feedback between climate and land-cover is important for planning climate mitigation and adaptation measures at local scales. This study presents evidence that climate change has the potential to influence land-cover patterns over space and time and land change models can compliment climate models to provide better understanding of the climate and land-cover relations at local levels. Present day (1982–2006) and downscaled future (2046–2065) rainfall and temperature data were integrated with local eco-geographical factors to build change suitabilities for land-cover change for present day and future climate scenarios. The basis land-cover maps were derived from Landsat imageries. The change suitabilities were combined with markov probabilities and applied to the basis land-cover to predict future land-cover maps under the present day and future climate scenarios using Idrisi’s Cellular Automata-Markov land change model. The results suggest that forest and woodland which is the major canopy ecosystems are expected to remain relatively stable both in areal coverage and spatial pattern under the present day climate scenario. In the future climate scenario, the areal coverage of the canopy ecosystems is expected to be relatively stable, but dramatic change in the spatial pattern is likely as the wooded savanna becomes drier. The forests would likely become more disturbed, with galleria forest becoming the most significant forest type. Shrub/grassland is also projected to become much more widespread. This scenario is expected to alter the spatial pattern of emerging built up and agricultural land-uses.
TL;DR: In this article, the standard thermodynamic potentials of natural zeolites in unified stoichiometric formulas were derived by using linear programming for the calculation of standard thermodynamics potentials for the systems of calcium-, sodium-, Ca-Na, K-Na-Ca, and K Na-Ca-Mg-zeolites.
Abstract: The systems of calcium-, sodium-, Ca-Na, K-Na-Ca, and K-Na-Ca-Mg-zeolites have been considered by methods of linear programming for calculations of standard thermodynamic potentials of natural zeolites in unified stoichiometric formulas. KeywordsZeolites; Standard Thermodynamic Potentials; Linear Programming
TL;DR: In this paper, the seasonal and solar cycle distribution of storms with sudden commencement is presented, and a correlation between the number of geomagnetic storms by month and monthly sunspot numbers is observed.
Abstract: In this brief paper the seasonal and solar cycle distribution of storms with sudden commencement is presented. A correlation between the number of geomagnetic storms by month and monthly sunspot numbers is observed. Also, a pronounced seasonal variation of the occurrence of intense geomagnetic storms and no dependence for moderate geomagnetic storms, which occur more frequently than the intense ones during the solar cycles.
TL;DR: In this article, an evaluation of the aquifer properties of the inland sedimentary Bida basin, central Nigeria, using empirical methods derived from particle size distribution curves was conducted using the Hazens method, while porosity was determined in the laboratory.
Abstract: An evaluation of the aquifer properties of the inland sedimentary Bida basin, central Nigeria, was conducted using empirical methods derived from particle size distribution curves. The main aquifer properties determined were hydraulic conductivity, porosity, effective porosity and coefficient of uniformity. Samples for analysis were obtained from test water wells drilled to 100m in selected parts of the Basin. The empirical method used was the Hazens method, while porosity was determined in the laboratory. The results show that three levels of aquifers generally exist in the Basin. The aquifer material consist of well sorted medium sand to fine gravel. The upper aquifer occurs at a depth of between 10 – 18m and has a hydraulic conductivity of 18.5m/d and effective porosity of 9.0. The second, or middle, aquifer occurs at a depth of between 45 – 65m and has a hydraulic conductivity of 37m/d and effective porosity of 20. The third, or lower, aquifer occurs between 80 – 100m and has a hydraulic conductivity of 32m/d and effective porosity of 24. Effective porosity generally increases with depth in the basin indicating coarsening up of the sandstone with fewer fine grained cementing material. Mean hydraulic conductivity value is 29.16m/d, porosity 63%, effective porosity of 6.7 and coefficient of uniformity of 2.8. The results have therefore shown that it is possible to obtain quantitative results from particle size distribution curves that are useful for the determination of hydraulic properties of aquifers.
TL;DR: In this paper, the authors investigated the relationship between magnetic structure of coronal holes and/or coronal mass ejection (CME) source region and their influence on Earth's geomagnetic field, i.e. storms and sub storms.
Abstract: The solar Cycle 23 has shown some peculiar features, i.e. slow and prolonged decline phase. When it is combined with the ascending phase of Cycle 24, it provides a long phase during which the overall magnetic activity was very low. During this interval the average sunspot number appeared on the solar disk was very low and signified the weak polar magnetic fields, and solar wind streams mainly originating from coronal holes. The study investigated the relationship between magnetic structure of coronal holes and/or coronal mass ejection (CME) source region and their influence on Earth's geomagnetic field, i.e. storms and sub storms. The study is performed mainly considering very intense geomagnetic storms that occurred during Solar Cycle 23. The disturbance storm time index Dst is taken as an indicator of geomagnetic activity by setting a value of Dstmin ≤ −200 nT as threshold. By examining halo CMEs that erupted between 2000 and 2008, we selected 07 events associated with M-class and X-class solar flares. Furthermore, as the geomagnetic field (BGeomag) puts a lower cutoff rigidity (Rc) to the entry of cosmic particles in to the earth's atmosphere. It depends upon the nature of geomagnetic activity and also upon the reconnection of field with the plasma regions formed due to the solar ejections. Sometimes when this entry of charged particles exhibits very sudden sharp and short lived increases in cosmic ray intensities, registered by the neutron monitor, it is termed as Ground-level enhancement (GLEs). These enhancements are known to take place during the result of powerful solar eruption. In present investigation GLE event associated with solar flare and coronal mass ejection (CME) occurred during the study period are also studied. The spacecraft data acquired by STEREO mission and those provided by SOHO, ACE and geomagnetic data from the geomagnetic stations like WDC-Kyoto are utilized in the study. It is found that the GLE's are well associated to X-class solar flares. The average speed of GLE associated CME was much faster than the average speed of non GLE associated CMEs.
TL;DR: In this article, a detailed field investigation of the vertical profiles revealed by "natural longitudinal trenches" formed in the rock avalanche deposits, an obvious vertical gradation along their sliding paths is observed, and proposed to be divided into five zones from the top to the bottom and named as follows: the air-blast zone, the bouncing and jumping zone, sliding and deposit zone, basal travel zone, and the original accumulation zone.
Abstract: Study on rock avalanche kinematics is still a hotspot in the world, especially after the Wenchuan earthquake. To examine this mechanism further, some rock avalanches triggered by the Wenchuan earthquake are taken as objects in this paper. After a detailed field investigation of the vertical profiles revealed by "natural longitudinal trenches" formed in the rock avalanche deposits, an obvious vertical gradation along their sliding paths is observed, and proposed to be divided into five zones from the top to the bottom and named as follows: the air-blast zone, the bouncing and jumping zone, the sliding and deposit zone, the basal travel zone, and the original accumulation zone. Based on the characteristics of these zones, the formation of each zone is discussed in detail with corresponding conclusions proposed: (1) The air-blast zone, as the upper boundary of the area damaged by rock avalanches, is destroyed by wind gusts initiated by a large rapidly moving mass. (2) The bouncing and jumping zone, mainly characterized by the display of accumulated fine grains and isolated blocks, is produced by the co-work of escaping force of entrapped air and debris internal force. (3) The coupling effect of kinematic sieving and momentum transfer is the main reason for the formation of sliding and deposit zone. (4) Debris in basal travel zone goes through a complex dynamical process: collision, dilation, fragmentation, rotation and sliding, and compaction. In this process, both the overburden pressure and the self-excited vibration energized by the undulated slip surface are the main dynamical forces controlling the formation of basal travel zone. And the simple shear and pure shear modes are the main mechanical behaviors, which realize the formation of particle fragmentation, a binary mixture with coarse particles embedded in clay matrix, and alignment distribution of particles in basal travel zone.
TL;DR: In this paper, the authors used data from 46 synoptic and climatologic stations that almost covered all part of Iran have been got from the national weather organization and have been used after the extraction of necessary data for a 30-year period from 1976 to 2005.
Abstract: In this paper, in order to study of the highest daily precipitations of daily precipitations data in 46 synoptic and climatologic stations that almost covered all part of Iran have been got from the national weather organization and have been used after the extraction of necessary data for a 30-year period from 1976 to 2005. In concerning of data analysis, necessary statistical analyses like data homogeneity test, normality test, correlation test, simple and multiple regressions, variance analysis, Friedman's non parametric test and classification cluster analysis have been used. The results showed that the average of the highest precipitations in all the studied stations during the statistical period of the research, except in two stations of Boushahr and Khoy, don't have any significant difference. Investigation of the changes of the highest annual precipitations in the statistical period in each of these stations showed that these changes are significant in Sanandaj station and in the other stations no significant change is observed. The results also proved that there is a positive and significant relation between the highest daily precipitation and annual precipitation in all the stations which means increase in the annual precipitation the highest daily precipitation of stations growth. Finally climatic classification of the stations displays 5 layers in terms of the proportion from highest daily rain to annual rain in the country.
TL;DR: In this paper, the Global Ionospheric Total Electron Content (TEC) maps (GIMs) for the time period from 04:50 to 05:05 UT are examined by Principal Component Analysis (PCA) and Nonlinear Principal Component analysis (NLPCA).
Abstract: In this study, the Global Ionospheric Total Electron Content (TEC) maps (GIMs) for the time period from 04:50 to 05:05 UT are examined by Principal Component Analysis (PCA) and Nonlinear Principal Component Analysis (NLPCA) in order to detect
TL;DR: In this article, the authors analyzed features of the seismic regime before one of the strongest earthquake Taiwan in the twentieth century (Chi-Chi, 21.09.1999, Mw = 7.6).
Abstract: The purpose of this paper is an analysis of features of the seismic regime before one of the strongest earthquake Taiwan in the twentieth century (Chi-Chi, 21.09.1999, Mw = 7.6). According to data for 1990-1999 variations of three parameters of the seismic regime were studied retrospectively: total annual number of earthquakes N? in the range of magnitudes of ML = 2.5-5.5, total annual quantity of released seismic energy ?E, J and angular coefficient b of graphs of recurrence of earthquakes. There were chosen two obvious sub-periods in course the seismic regime – quiescence in 1990-1996 and activation in 1997-1999. Earthquake of Chi-Chi occurred on a maximum of seismic activity. Overestimated value of coefficient b (-1.16 on average) is conditioned by prevalence of weak earthquakes in a period of preparation the Chi-Chi earthquake.