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991.
Relative Sea Level Changes in Maldives and Vulnerability of Land Due to Abnormal Coastal Inundation 总被引:1,自引:0,他引:1
Tariq Masood Ali Khan Dewan Abdul Quadir T. S. Murty Anwarul Kabir Fahmida Aktar Majajul Alam Sarker 《Marine Geodesy》2013,36(1-2):133-143
Oceanic Islands in the Pacific and Indian Oceans have extremely small land areas, usually less than 500 km2, with maximum height about 4 m above sea level. The Republic of Maldives is an independent island nation in the Indian Ocean south of Sri Lanka which stretches vertically in the Indian Ocean from 07° 06'N - 0° 42'S. The land area of this island country is about 300 km2, and none of Maldives' 1190 islands has an elevation more than 3 m above sea level. In fact the Maldives has the distinction of being the flattest country on earth, making it extremely vulnerable to the effects of global warming. Of the south Asian countries, the Maldives is the most vulnerable nation, facing severe consequences as a result of global warming and sea level rise (SLR). Because of their obvious vulnerability to SLR, the Government of Maldives is very much concerned about climate change. As global warming and the related SLR is an important integrated environmental issue, the need of the hour is to monitor and assess these changes. The present article deals mainly with the analysis of the tidal and Sea Surface Temperature (SST) data observed at Male and Gan stations along the Maldives coast in the northern and southern hemispheres, respectively. The objective of the analysis is to study the trends of these parameters. Trend analysis is also performed on the corresponding air temperature data of both stations. The results show that Maldives coastal sea level is rising in the same way (rising trend) as the global sea level. The mean tidal level at Male has shown an increasing trend of about 4.1 mm/year.Similarly at Gan, near the equator,it has registered a positive trend of about 3.9 mm/year.Sea level variations are the manifestations of various changes that are taking place in the Ocean-Atmosphere system. Therefore, the variations in SST and air temperature are intimately linked to sea level rise. It is found that SST and air temperature have also registered an increasing trend at both stations. The evidence of rising trends suggest that careful future monitoring of these parameters is very much required. Tropical cyclones normally do not affect the Maldives coast. However, due to its isolated location, the long fetches in association with swells generated by storms, that originated in the far south have resulted in flooding. Thus the rising rate of sea level with high waves and flat topography have increased the risk of flooding and increased the rate of erosion and alteration of beaches. 相似文献
992.
Pervaiz Sikandar Allah Bakhsh Muhammad Arshad Tariq Rana 《Environmental Earth Sciences》2010,60(5):1113-1129
A geoelectrical resistivity survey using vertical electrical sounding (VES) was conducted at Chaj Doab (land between rivers
Jhelum and Chenab, Pakistan) and Rachna Doab (land between rivers Chenab and Ravi, Pakistan), with the objective of investigating
groundwater conditions. A total of 90 sites were selected with 43 sites in Chaj and 47 sites in Rachna Doabs. The resistivity
meter (ABEM Terrameter SAS 4000, Sweden) was used to collect the VES data by employing a Schlumberger electrode configuration,
with half current electrode spacings (AB/2) ranging from 2 to 180 m and the potential electrode (MN) from 1 to 40 m. The field
data were interpreted using the Interpex IX1D computer software and the resistivity versus depth models for each location
was estimated. The outputs of subsurface layers with resistivities and thickness presented in contour maps and 3-D views by
using SURFER software were created. A total of 102 groundwater samples from nearby hydrowells at different depths were collected
to develop a correlation between the aquifer resistivity of VES and the electrical conductivity (EC) of the groundwater and
to confirm the resulted geophysical resistivity models. From the correlation developed, it was observed that the groundwater
salinity in the aquifer may be considered low and so safe for irrigation if resistivity >45 Ω m, and marginally fit for irrigation
having resistivity between 25 and 45 Ω m. The study area has resistivities from 3.9 to 2,222 Ω m at the top of the unsaturated
layer, between 1.21 and 171 Ω m, in the shallow aquifers, and 0.14–152 Ω m in the deep aquifers of the study area. The results
indicate that the quality of groundwater is better near the rivers and in the shallow layers compared to the deep layers. 相似文献
993.
Aimal K. KASI Akhtar M. KASSI Muhammad UMAR Henrik FRIIS Mohibullah MOHIBULLAH Razzaq A. MANAN 《《地质学报》英文版》2018,92(2):499-518
Detailed facies analysis of the Neogene successions of the Pishin Belt (Katawaz Basin) has enabled documentation of successive depositional systems and paleogeographic settings of the basin formed by the collision of the northwestern continental margin of the Indian Plate and the Afghan Block. During the Early Miocene, subaerial sedimentation started after the final closure of the Katawaz Remnant Ocean. Based on detailed field data, twelve facies were recognized in Neogene successions exposed in the Pishin Belt. These facies were further organized into four facies associations i.e. channels, crevasse splay, natural levee and floodplain facies associations. Facies associations and variations provided ample evidence to recognize a number of fluvial architectural components in the succession e.g., low‐sinuosity sandy braided river, mixed‐load meandering, high‐sinuosity meandering channels, single‐story sandstone and/or conglomerate channels, lateral accretion surfaces (point bars) and alluvial fans. Neogene sedimentation in the Pishin Belt was mainly controlled by active tectonism and thrusting in response to the oblique collision of the Indian Plate with the Afghan Block of the Eurasian Plate along the Chaman‐Nushki Fault. Post Miocene deformation of these formations successively caused them to contribute as an additional source terrain for the younger formations. 相似文献
994.
Asghar ALI Khaista REHMAN Owais TAYYAB Tahir ZAMAN Mahad JAMEEL Azeem KHAN Rafique AHMAD Muhammad IRFAN 《《地质学报》英文版》2020,94(5):1440-1450
Analysis of the anomalous magnetic mineral intensities and geochemistry for placer gold deposits are presented for those of the Attock area at the confluence of the Indus and Kabul rivers in northwestern Pakistan. Two grids covering an area of 10x18 m2 and 8x10 m2 were analyzed using a G-858 Cesium Vapor Magnetometer. The anomalous zones obtained were plotted on contour maps, 2D and 3D magnetic intensity maps. Based on the magnetic anomalies, grid-1 of the study area was sampled at three different anomalous zones for geochemical analysis. These zones contain gold concentrations, ranging from 2.11 ppm to 6.109 ppm with an average of 4.01 ppm. Increase in gold concentration in the subsurface within the anomalous zones indicates that magnetometer survey followed by a geochemical analysis can potentially narrow down the gold-bearing anomalous zones. 相似文献
995.
湖泊碎屑岩沙坝因波浪和沿岸流的反复冲刷,成熟度较高,显示出巨大的油气勘探潜力,已成为隐蔽油气藏勘探的重点。作者在大量文献调研的基础上,总结了近年来前人在滩坝定义、沉积特征、主控因素、成因机制及内部构型研究中的重要进展,在此基础上提出了沙坝演化阶段及沉积构型的新认识。结果表明,沙坝完整的演化历程主要包括4个阶段,分别是弱波浪作用阶段、动荡水流—冲洗回流阶段、风成阶段及沼泽化阶段。影响沙坝发育的控制因素多样,其中物源和风场是沙坝发育的根本因素,两者分别影响了沙坝发育的物质来源和能量供给;而风场所决定的水动力是影响沙坝储集体发育的最直接因素;构造运动和层序演化则控制沙坝的分布位置及保存程度;各因素综合作用决定了坝的形态、发育规模及保存状况。依据前人构型理论,将沙坝构型按照正序方案依次划分为6级,对构型表征方法和沙坝3~5级构型定量表征进行了初步探索,以期为滩坝砂体勘探开发提供理论和实践支持。 相似文献
996.
Naghmah?HaiderEmail author Sajjad?Khan Asghar?Ali Liaqat?Ali 《Arabian Journal of Geosciences》2016,9(8):531
The Pliocene-Pleistocene Ghari Chandan Formation consists of lacustrine-fluvio-deltaic deposits exposed in the Attock-Cherat Range. Three beds of bentonite deposits occur in the upper part of the formation. An average thickness of each layer ranges from 0.4 to 1 m with a total strike length of ~5 Km. Montmorillonite and saponite clay minerals with admixtures of quartz, feldspar, muscovite, biotite, and hornblende were identified in these samples. Compositionally these beds are similar and comprised of dioctahedral smectite. The differential thermal analyses of bentonite reveals high thermal stability of the deposits. Detailed mineralogical and geochemical investigations suggest that the Garhi Chandan deposit is a mixture of calcic and sodic bentonite derived from andesitic and trachyandesitic source rock. Heavy metal concentration reduces the overall adsorbing capacity of the deposit. 相似文献
997.
M. A. Mumin B.Sc. Eng. M. M. R. Khan M.Sc. Ph.D. K. F. Akhter B.Sc. Eng. M. J. Uddin B.Sc. Eng. 《International Journal of Environmental Science and Technology》2007,4(4):525-532
Open burnt clay was studied as a potential adsorbent for the adsorption of Congo red (a reactive dye) from aqueous solution. The effect of contact time, pH, adsorbent dosage and temperature were studied. It was observed that the amount of Congo red retained increase with decreasing pH and increasing initial concentration. Removal percentage at pH 2 and 3 are almost same. The adsorption capacity of regenerated burnt clay was showed more than 98 % recovery of the adsorption efficiency of initial virgin adsorbent. The equilibrium data were described well by both Langmuir and Freundlich isotherm model. The adsorption capacity of some natural adsorbents, namely rice husk, wood charcoal, tea waste etc. were also investigated and compared with that of open burnt clay. 相似文献
998.
Salih Muhammad Awadh 《Environmental Earth Sciences》2012,66(8):2247-2256
Five dust storms that occurred in 2008 (15 March, 11 April, 28 April, 25, May and 26 June) in addition to the many sand dunes disseminated in the Western Desert of Iraq are sampled. The worse dust storm that occurred in Iraq in 11 April, 2008 covered 75% of the Iraq area and deposited 6.9?million tons approximately as a total weight of fallout during just 8?h, declining temperature 6°C. During the episodes of dust storms, visibility decreased enormously, no more than 30?m. Many people were taken to hospitals after sustaining breathing problems. Some of them died. Clay fraction is the dominant part in the dust storms forming 70% besides a little silt (20.6%) and sand (9.4%), then classified as mature arkose of clay to sandy clay, whereas sand dunes are formed from 72.7% sand, 25.1% silt and 2.19% clay, then classified as mature arkose of silty sand. Sand dunes have much maturity. Mineralogical composition of dust storms and sand dunes are Quartz (49.2%, 67.1%), feldspar (4.9%, 20.9%), calcite (38%, 5%), gypsum (4.8%, 0.4%), dolomite (0.8%, 1%) and heavy minerals (3.2%, 6.6%), respectively. Heavy mineral suites in the dust storms are represented by zircon, pyroxene, hornblende, chlorite and magnetite; whereas the sand dunes are represented by zircon, tourmaline, garnet and pyroxene, concentrated within sand fraction. Heavy minerals according to satellite images revealed the dry land of Sahara Desert in North Africa and the Arabian Peninsula as well as Syria and Jordan were a major source of the dust storms that have occurred in Asia, including Iraq. 相似文献
999.
Mautaz Al-Dabbas Salih Muhammad Awadh Ayad Abed Zaid 《Arabian Journal of Geosciences》2013,6(2):491-503
This study deals with the mineralogical and geochemistry of the Euphrates Formation (Lower Miocene) in Bahr Al-Najaf area in order to assess the lithofacies of the Euphrates Formation for Portland cement manufacturing. Petrographic and mineralogical studies were carried out on 210 core samples, collected from 21 boreholes, and showed that calcite is the dominant mineral with few amounts of quartz, gypsum, feldspar, and a rare amount of dolomite. Clay mineral suites (palygorskite, kaolinite, montmorillonite, and illite) formed about 5% from the total mineral composition. Palygorskite precipitated directly in alkali shallow water rich with Si and Mg ions. Chemical weathering of feldspar under acidic conditions participated in formation of Kaolinite. Geochemistry showed that there is no high variation in chemical constituents with depth, and the average of CaO (51.5), MgO (0.83), SO3 (0.54), SiO2 (4.3), Fe2O3 (0.45), Al2O3 (0.93), L.O.I (40.7), Na2O3 (0.08), K2O (0.14), and Cl- (0.1) qualified the lithofacies of Euphrates Formation to be raw materials suitable for manufacturing the Portland cement. Triangle Block method is applied to estimate the reserve on square area (2?×?2 km2) which is computed to be 63 million tons of medium-tough limestone as potential probable reserve. 相似文献
1000.
Kaleem Ullah Jan KHAN WANG Chang-ming Muhammad Wasim Jan KHAN LIANG Zhu LI Shuo LI Bai-long 《山地科学学报》2021,(6):1696-1709
The slope instability is associated with increasing rate of rainfall infiltration which cause shear strength reduction and suction loss and the slope tend to fa... 相似文献