Hazardous earth processes in parts of Bauchi State,Nigeria: Their causes and environmental implications     

D. M. Orazulike 《Natural Hazards》1988,1(2):155-160

The August 1985 crack has focussed attention on passive earth processes in parts of Bauchi State, Nigeria. These processes, encompassing groundwater solution and roof collapse, soil shrink-swell, and gullying, are widespread in the Akko, Gombe, and Bauchi Local Government Areas (LGAs) of the State. Soils in these areas are rich in montmorillonite clay minerals and possess appreciable shrink-swell capabilities. Surface heave ranges from 8.1 to 11 cm. Preliminary data on plasticity measurement show a plasticity index (PI) of 13.4 to 15%. Consequently, in response to seasonal changes, the soil usually splits, leaving gaping cracks. These cracks, once formed, constitute channels throug which meteoric water easily penetrates the bedrock. The water is chemically acid and the underlying bedrock contains layers of limestone and shale. Systematic solution of these chemically reactive rocks results in the formation of caverns, the roof of which may ultimately collapse leaving randomly distributed sink holes. These cracks and sink holes run through villages, destroying mud buildings, which often collapse overnight, and transforming most modern block buildings into death traps. They affect roads, bridges, and other foundations, and render farmlands waste, swallowing up livestock.The expansive soil processes, solution and roof collapse phenomena currently identified in these places, are passive phenomena and have been overlooked as geologic hazards. Preliminary results of investigations on the physical and chemical properties of the soils and underlying rocks indicate that these areas of Bauchi State of Nigeria need to be monitored closely to avert disaster.  相似文献   

Afghanistan’s development and functionality: Renewing a collapsed state     

John Shroder 《GeoJournal》2007,70(2-3):91-107

Afghanistan has long been backward and underdeveloped where centuries of desertification, deforestation, overgrazing and environmental degradation have combined with successive invasions, violence, and terrorism to reduce the population to abject poverty. In the post 9/11 world, development of Afghanistan is seen as the only hope to revive the failed nation and reduce its threat to the external world. New assessments of natural resources offer many solutions to old problems of development and the potential economic functionality through renewal of the collapsed state. Oil, gas, copper, iron, gemstones, and a number of other resources, combined with a renewed transportation grid, offer a viable solution that is now underway to possibly produce a somewhat more promising future, providing that corruption, renewed violence, and environmental despoliation can be kept to a minimum.  相似文献   

Karst system developed in salt layers of the Lisan Peninsula,Dead Sea,Jordan   总被引：1，自引：0，他引：1  

Damien?ClossonEmail author  Philip?E.?LaMoreaux  Najib?Abou Karaki  Hassan?al-Fugha 《Environmental Geology》2007,52(1):155-172

The Lisan Peninsula, Jordan, is a massive salt layer accumulated in the inner part of the Dead Sea’s precursory lakes. This tongue-shaped, emergent land results in a salt diapir uplifted in the Dead Sea strike-slip regional stress field and modified by the water level fluctuations of the last lake during the Holocene. These two elements, associated with dissolution caused by rainfall and groundwater circulation, resulted in an authentic karst system. Since the 1960s, the Dead Sea lowering of 80 cm to 1 m per year caused costly damages to the industrial plant set up on the peninsula. The Lisan karst system is described in this article and the components of the present dynamic setting clarified.  相似文献   

Testing less-conventional methods to date a late-pleistocene to Holocene eruption: Radiocarbon dating of paleosols and 36Cl exposure ages at Pelado volcano,Sierra Chichinautzin,Central Mexico     

《Quaternary Geochronology》2022

Despite their significance for estimating hazards and forecasting future activity, dating young volcanic deposits and landforms (<50,000 yrs old) remains a challenge due to the limitations inherent to the different isotopic chronometers used. The Trans-Mexican Volcanic Belt is one of the most active and populated continental arcs worldwide, yet its temporal pattern of activity is poorly constrained. Such deficiency is particularly problematic for the Sierra Chichinautzin Volcanic Field (SCVF) that is located at the doorstep of Mexico City and Cuernavaca and is hence a major source of risk for these cities. Existing ages for this area derive mostly from either radiocarbon on charcoal, which is rare and may be contaminated, or ⁴⁰Ar/³⁹Ar on rock matrix, which is poorly precise for this time period and rock type. Here, we focus on the Pelado monogenetic volcano, which is located in the central part of the SCVF and erupted both explosively and effusively, producing a large lava shield and a widespread tephra blanket. This unique eruptive event was previously dated at ∼12 calibrated (cal) kyrs BP, using radiocarbon dating on charcoal from deposits related to the eruption. To test alternative dating approaches and confirm the age of this significant eruption, we applied two less conventional techniques, radiocarbon dating of bulk paleosol samples collected below the complete tephra sequence at nine sites around the shield, and in-situ ³⁶Cl exposure dating of two samples of an aphyric lava from the base of the shield. Radiocarbon paleosol ages span a continuous time interval from 13.2 to 20.2 cal kyrs BP (2σ), except for one anomalously young sample. This wide age spread, along with the low organic contents of the paleosols, may be due to erosive conditions, related to the sloping topography of the sampling sites and the cool and relatively dry climate of the Younger Dryas (11.7–12.9 ka), during which the Pelado eruption probably occurred. The two ³⁶Cl-dated lava samples have consistent ages at 1σ analytical errors of 15.5 ± 1.4 ka and 13.2 ± 1.2 ka, respectively, yielding an average age of 14.3 ± 1.6 ka for this lava flow. The high full uncertainty in ³⁶Cl ages (24%) is due to high rock Cl content. We conclude that paleosol radiocarbon dating is useful if numerous samples are analyzed and climatic and relief conditions at the time of the eruption and at the sites of tephra deposition are considered. The ³⁶Cl dating technique is an alternative method to date volcanic eruptions, as it gave consistent results, but in the specific case of Pelado volcano, the high Cl content in the analyzed rocks increases the age uncertainties.  相似文献   

中印地震和滑坡灾害研讨会在印度举行     

中国地震局地震专家代表团 《国际地震动态》2002,(5):21-24

介绍了2002年1月21－23日在印度国家科学院举行的“中印地震和滑坡灾害研讨会”概况及印度有关科研机构的研究计划和进展情况。  相似文献   

新疆独山子震害地质区划   总被引：1，自引：0，他引：1       下载免费PDF全文

王立功  蔡灵铎 《地震地质》1990,12(1):69-75

本文扼要介绍了独山子地区特有的地质背景——最新的造山运动、独特的泥火山喷出物、广阔的戈壁平原和特殊的洼地沉积。与地质背景有关的一系列地质因素地基土、地形、断层、崩塌、滑坡等也具有独特的区域特征。地质因素地震易损性分析结果,取得震害地质A、B、C、D、E五级分区。根据不同分区地震地面效应强弱程度的差异,建议在土地利用上应避南就北,即避开泥火山和山前洼地而就戈壁平原  相似文献   

A conceptual model of vegetation dynamics in the semiarid Highland savanna of Namibia, with particular reference to bush thickening by Acacia mellifera     

D.F. Joubert  A. Rothauge  G.N. Smit   《Journal of Arid Environments》2008,72(12):2201-2210

Namibian rangelands are encroached with Acacia mellifera, partially resulting from a poor understanding of vegetation dynamics. A conceptual state-and-transition model of vegetation dynamics in the semiarid Highland savanna in central Namibia, emphasising bush thickening by A. mellifera, is described. Two main states, a grassy and a bushy state, are identified. These are further subdivided, and 11 transitions are identified. The key transition initiating a change from grassy to bushy state can be termed a “leap” (an occasional, infrequent mass recruitment event) following a long “sleep” (no or little change in A. mellifera density). It is rare because it requires three consecutive years of above-average rainfall for seedling establishment. Fire, coinciding with seedling establishment, can interrupt it, while a low biomass grass sward facilitates it. The phenology and physiology of the encroaching species, seed predation and sapling herbivory influence this transition. The model proposes opportunistic management interventions, particularly the use of fire, to minimise the risk of further landscape-scale transitions to a bushy state. It highlights areas where understanding of vegetation dynamics is lacking and recommends crucial research foci. Conceptual models of bush-thickening processes need to account for differences in climate and phenological details of encroaching species.  相似文献   

Frequent eruptions of Mount Rainier over the last ∼2,600 years     

T. W. Sisson  J. W. Vallance 《Bulletin of Volcanology》2009,71(6):595-618

Field, geochronologic, and geochemical evidence from proximal fine-grained tephras, and from limited exposures of Holocene lava flows and a small pyroclastic flow document ten–12 eruptions of Mount Rainier over the last 2,600 years, contrasting with previously published evidence for only 11–12 eruptions of the volcano for all of the Holocene. Except for the pumiceous subplinian C event of 2,200 cal year BP, the late-Holocene eruptions were weakly explosive, involving lava effusions and at least two block-and-ash pyroclastic flows. Eruptions were clustered from ∼2,600 to ∼2,200 cal year BP, an interval referred to as the Summerland eruptive period that includes the youngest lava effusion from the volcano. Thin, fine-grained tephras are the only known primary volcanic products from eruptions near 1,500 and 1,000 cal year BP, but these and earlier eruptions were penecontemporaneous with far-traveled lahars, probably created from newly erupted materials melting snow and glacial ice. The most recent magmatic eruption of Mount Rainier, documented geochemically, was the 1,000 cal year BP event. Products from a proposed eruption of Mount Rainier between AD 1820 and 1854 (X tephra of Mullineaux (US Geol Surv Bull 1326:1–83, 1974)) are redeposited C tephra, probably transported onto young moraines by snow avalanches, and do not record a nineteenth century eruption. We found no conclusive evidence for an eruption associated with the clay-rich Electron Mudflow of ∼500 cal year BP, and though rare, non-eruptive collapse of unstable edifice flanks remains as a potential hazard from Mount Rainier. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. T. W. Sisson and J. W. Vallance contributed equally to this study.  相似文献   

城市生活垃圾卫生填埋场填土层工程特性及净化机理研究   总被引：3，自引：0，他引：3  

张莲花 《地质灾害与环境保护》1999,(Z1)

城市生活垃圾卫生填埋场中,填土层对垃圾淋滤液的渗透阻滞和净化作用具有重要意义。对成都万兴固体废弃物处置场填土料的压实性、渗透性及其相互关系,在大量试验的基础上作了深入探讨并导出关系式。填土层对垃圾淋滤液中污染物的衰减净化,是各种因素综合作用的结果。以工程地质为基础,研究生活垃圾淋滤液中常见离子净化规律和机理,认为土层结构的不同,对淋滤液的净化有一定影响,而这种影响因离子的不同而有不同程度的表现：二价离子交换吸附,引起渗透系数在０．５～１．０个数量级范围内变化;离子的负吸附,表明土层吸附的可逆性;而典型的一价离子ＮＨ＋４和Ｃｌ－的净化规律,可用指数函数表征;有机物的衰减与土的有机碳的含量有关。这些研究成果,为全面研究填埋体结构的合理化设计提供了重要依据。  相似文献   

陕西三原双槐树地裂缝的发育特征   总被引：3，自引：0，他引：3  

卢全中  彭建兵  范文  马润勇  李喜安 《工程地质学报》2007,15(4):458-462

陕西三原双槐树地裂缝由两条近平行的地裂缝组成,延伸长度大于4km,地裂缝活动给沿线居民带来了巨大的灾害和经济损失。通过调查访问和探槽、探井、平硐等勘探工程,从平面展布特征、剖面结构特征、活动特征和力学性质等方面描述了该地裂缝的发育特征。结果显示:南侧的F1地裂缝的破碎带宽度和活动程度均大于北侧的F2地裂缝,其中的F1地裂缝破碎带宽度一般大于10m,最大可达50余米,不同期次和不同级次的裂缝数量可达30余条,如此规模的裂缝破碎带宽度和裂缝数量在黄土地区并不多见。  相似文献