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1.
CHRISTINE ELLIOTT 《New Zealand geographer》2003,59(1):50-60
A review of some recent studies on rock weathering in Antarctica has revealed that Antarctic weathering research has a significant contribution to make to the ongoing debate about rock weathering in cold climates. Largely conducted in the field rather than the laboratory as in the Northern Hemisphere, it demonstrates that whilst all weathering processes can occur in Antarctica this is highly localised and dependent on the particular micro‐environment. Freeze‐thaw, for example, is not the most dominant process in many parts of Antarctica. The right combination of rock temperature and moisture can mean that salt, insolation, hydration or even chemical weathering can predominate. 相似文献
2.
福建长乐屏山风化坑与河流壶穴的成因及其证据 总被引：1，自引：0，他引：1
风化坑和壶穴是一种常见的岩石坑穴地形,其形成原因和形态完全不同,但容易被误解和混淆.结合对福建长乐三溪河地区这两种坑穴地形的实地考察,本文从地貌学,沉积学,岩石化学和矿物学等各个方面对两者的形成过程、影响因素进行了论证和对比.研究表明：风化坑形成于岩石面积水的风化作用,壶穴则是由河流的旋转水流对河床产生的侵蚀作用形成;山顶风化坑的发育与河流流水作用没有关系,河流壶穴的形成与河谷的发育过程有关,河谷中的风化坑只能在河流深切后,流水不再作用到的河床部位发育;只要条件合适,风化坑或壶穴随时可以生成;风化坑与河流壶穴的形态,坑内沉积物的磨圆度、粒度特征等反映出各自不同的形成过程.风化坑内碎屑与周边岩石的化学蚀变指数CIA 值的差异反映了风化坑的化学风化成因;风化坑内碎屑与周边岩石石英长石比例的差异说明风化坑是矿物差异风化的结果;用CIA 值和英长比均无法区分河流壶穴和风化坑中的碎屑颗粒,但两者化学元素迁移特征的差别反映了风化坑的风化作用和河流壶穴的流水搬运作用的成因差别;风化坑的风化程度达不到当地风化壳的风化程度,但不同气候带风化坑碎屑的CIA 值能反映不同气候带风化作用的强度差异. 相似文献
3.
Heather Viles 《Geomorphology》1995,13(1-4)
A wide range of information is now available on the ecology of rock surface microorganisms (including bacteria, fungi and algae) and lichens and their role in weathering in particular locations. External environmental conditions as well as rock characteristics determine the type of rock surface community, and thus the style of biological weathering. A simple, preliminary conceptual model can be drawn, which relates biological weathering activity to an environmental stress gradient and which is applicable at a range of scales. Further research needs carrying out to test and extend this model in order to make some progress towards the important goal of assessing the overall importance of biological weathering to geomorphology. 相似文献
4.
Weathering processes in the Ellsworth Mountains of Antarctica are dominated by frost action. These processes were observed to be different on the same group of marbles under different slope conditions. North- and south-facing walls of the bedrock showed the same shattering rate in the summer of 1992–1993. Frost shattering of rocks is controlled by surface temperature, moisture, and the physical properties of the rock. The most important control on frost shattering in this area was moisture availability, given the same bedrock and freeze-thaw cycle. Snow particles are moved by katabatic winds, bringing moisture to the rock. Moisture is collected mainly in lower cliffs and cols. [Key words: weathering, marble, moisture conditions, Antarctica.] 相似文献
5.
Norikazu Matsuoka 《Geomorphology》1995,12(4)
Field observations of weathering processes and the related landforms, combined with laboratory analyses of weathering products, permit a synthetic evaluation of Late Cenozoic weathering environments in the Sør Rondane Mountains, Antarctica, an arid upland characterized by low temperatures and strong winds. Rates and character of weathering depend mainly on moisture availability and the bedrock geology. Under the humid weathering regime that occurs only locally around the margin of the present sheet, frequent diurnal freeze-thaw cycles in summer cause relatively rapid rock fragmentation. Most of the mountains are situated in the arid weathering regime, under which rock breakdown is very slow unless the rock contains plenty of salts. Salt weathering becomes more intensive and extensive with exposure age, as a result of salt accumulation in rock, eventually producing soils as small as fine-silt size. Lack of clay mineralization even in weathered rocks having been exposed above the ice sheet prior to 4 Ma ago indicates that hydrolysis or carbonation of rock minerals has been insignificant during the past 4 Ma. The final products of weathering are due mainly to salt action and reflect the parent lithology. Resistant fine-grained granite forms strongly oxidized tors carved with tafoni, or fields of mushroom-like boulders overlying the fractured bedrock. Less resistant rocks, like biotite gneiss and amphibolite, produce stone pavements underlain by saline, silty soils up to 30–40 cm thick, the thickness of which corresponds to the maximum thaw depth. 相似文献
6.
BY VIKRAM GUPTA RUCHIKA SHARMA MADHO PRASAD SAH 《Geografiska Annaler: Series A, Physical Geography》2009,91(3):179-188
Four rock types (quartz mica gneiss, schist, quartzite and calc-silicate) located in the Satluj and Alaknanda valleys were used to test whether a Schmidt hammer can be used to distinguish rock surfaces affected by various natural and man-induced processes like manual smoothing of rock surfaces by grindstone, surface weathering, deep weathering, fluvial polishing and blasting during road construction. Surfaces polished by fluvial process yielded the highest Schmidt hammer rebound (R-) values and the blast-affected surfaces yielded the lowest R-values for the same rock type. Variations in R-value also reflect the degree of weathering of the rock surfaces. It has been further observed that, for all the rock types, the strength of relationship between R-values for the treated surfaces (manual smoothing of rock surface by grindstone) and the unconfined compressive strength (UCS) is higher than for the fresh natural surfaces. 相似文献
7.
The hyper-arid Namib Desert is an ancient desert of great lithological diversity. Weathering plays a key role in landscape evolution in the Namib which, in spite of its aridity, has a number of sources of moisture – rainfall, fogs, dews and groundwater seepage – which enhance weathering. Among the weathering processes that have been the subject of recent study in the central Namib are salt, thermal and lichen weathering which, in often complex associations of processes, contribute to the array of small scale weathering features found on marble and granite outcrops here. At the landscape scale weathering in the central Namib is also highly interrelated with erosion and the development of geochemical sediments (calcrete, gypcrete, tufas etc), whilst weathering ‘hotspots’ are thought to be important sources of fine sediment production. Over the long term weathering has played important roles in landscape evolution here which, despite localized weathering hotspots, has been very slow for much of the Cenozoic. 相似文献
8.
Great monumental places—Petra, Giza, Angkor, Stonehenge, Tikal, Macchu Picchu, Rapa Nui, to name a few—are links to our cultural past. They evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes. However, as with natural landforms, human constructs are subject to weathering and erosion. Indeed, many of our cultural resources suffer from serious deterioration, some natural, some enhanced by human impact. Groups from the United Nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources, from simple rock art to great temples. Geomorphologists trained in interacting systems, process and response to thresholds, rates of change over time, and spatial variation of weathering processes and effects are able to offer insight into how deterioration occurs and what can be done to ameliorate the impact.Review of recent literature and case studies presented here demonstrate methodological and theoretical advances that have resulted from the study of cultural stone weathering. Because the stone was carved at a known date to a “baseline” or zero-datum level, some of the simplest methods (e.g., assessing surface weathering features or measuring surface recession in the field) provide useful data on weathering rates and processes. Such data are difficult or impossible to obtain in “natural” settings. Cultural stone weathering studies demonstrate the importance of biotic and saline weathering agents and the significance of weathering factors such as exposure (microclimate) and human impact. More sophisticated methods confirm these observations, but also reveal discrepancies between field and laboratory studies. This brings up two important caveats for conservators and geomorphologists. For the conservator, are laboratory and natural setting studies really analogous and useful for assessing stone damage? For the geomorphologist, does cultural stone data have any real relevance to the natural environment? These are questions for future research and debate. In any event, cultural stone weathering studies have been productive for both geomorphologists and conservators. Continued collaboration and communication between the geomorphic, historic preservation, archaeological, and engineering research communities are encouraged. 相似文献
9.
Biancane badlands consisting of small domes dissected by rills and micropipes, with rough disordered microrehef, can be found along the Apennines in Italy. The dominant processes forming biancane differ from those of badlands formed on smectite-rich mudrocks, as micropipes associated with pseudokarstic enlargement of pores and cracks predominate and form the main routes for evacuation of eroded material.Biancana evolution is controlled by water infiltration into intact bedrock, producing an erodible weathering ‘rind’ which is more porous than intact rock. This rind is easily removed by rill or micropipe flow, and erosion is therefore ‘weathering-controlled’, depending on rind production by infiltrating water. Infiltration is initially slow and stepped, due to slow water movement through very small capillary pores in intact rock alternating with rapid filling of macropores and cracks. This occurs due to rapid matrix pore enlargement by dispersion and/or dissolution. The infiltration pattern is accurately reproduced by a model built on progressive development of weathering layers by moisture penetration. Model results are consistent with weathering rind depths and erosion observed in the field, and show that a pipe network can be generated on newly exposed rock by the rainfall of one year.Propagation of the pipe network diverts a progressively larger proportion of runoff into micropipes, expanding weathering rind production within the biancana as well as on the surface. Internal weathering and flow progressively dominate with few unweathered corestones, and the biancana gradually collapses into a penultimate “soufflé-like” form. 相似文献
10.
Rock coatings are frequent on natural rock outcrops and even more on stone surfaces of historical buildings and monuments. They are interesting as some of them have a protective effect against erosion. In the last 30 years, research on rock coatings has been performed separately on either buildings or natural outcrops. This paper studies and compares thin coatings found on granitic rock surfaces of historical buildings with coatings found on natural granite outcrops in a same climatic area (NW Spain) by analysing their surface and cross-sections. As rock surfaces of buildings have known age they can be used to assess rates of weathering and coating growth. This is the first comparative study of formation of coatings on natural and built surfaces in the same region. Both endogenous (rock characteristics) and exogenous factors (climatic conditions, air pollution) that could affect the coatings formation are considered to assess the origin and formation of coatings. X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) analyses of the underlying rocks, XRD analyses of the coatings and Scanning Electron Microscopy (SEM) observations of surface and cross-sections of the coatings, performing Energy Dispersive Spectrometry (EDS) and X-ray maps, were carried out to establish their composition. Fieldwork and results indicate that natural outcrops are widely covered by biological coatings or coatings formed due to rock weathering, while coatings found on rock ashlars are highly variable with air pollution, other building materials, organic droppings and micro-environmental factors contributing to coatings on rock ashlars in a more significant way than substrate characteristics and exposure time. 相似文献
11.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):257-264
Weathering processes responsible for landscape denudation in Arctic environments are poorly understood. Traditionally, gelifraction has been widely invoked as the dominant weathering process, but empirical support for this is frequently lacking. In Norwegian Lapland, post-glacial weathering has been recently attributed to predominantly biophysical processes, based on field measurements of landscape lowering undertaken by André (1995). The study reported here examined bedrock samples from one of André's sites for mineralogical and chemical transformations since post-glacial exposure. Backscatter scanning electron microscopy reveals extensive mineral grain dissolution and accompanying development of rock porosity. Wavelength dispersive spectroscopy shows these mineral alterations to be the result of the loss of major chemical constituents including Ca, Mg, K, Si, and Al. Chemical weathering is clearly a component of post-glacial landscape denudation in Norwegian Lapland, in addition to the important role of biophysical processes identified by André (1995). Cosmogenic dating of the sampled bedrock surface confirms that much of this weathering has occurred in the last 10,000 years. 相似文献
12.
An environmental chamber was used to simulate a 24-h cycle of rock surface temperature and relative humidity, a stone pavement with differing levels of sodium chloride content, and differing levels of fog precipitation to assess some of the controls of rock weathering in the vicinity of Swakopmund in the Namib Desert. The rock employed was Cretaceous Chalk. Some treatments were effective at causing disintegration after 76 temperature/humidity cycles and 10 fog cycles. Small amounts of fog moisture (0.5 mm per event) were associated with the greatest amounts of breakdown, whereas the amount of salt in the simulated pavements appeared to be of less significance. The experiment showed that sodium chloride can be an effective agent of weathering in a coastal foggy environment. 相似文献
13.
对内蒙、河北等地新近发现的壶穴进行详细的计量及采样分析 ,并参考国内外相关研究资料 ,认为本区壶穴是非冰成的风化风蚀穴。它的发育受到风、温度、降水、湿度、生物、地貌及岩体的结构构造等多种因子的控制。其中风化 ,尤其是盐风化等化学风化 ,是其主要控制因子 ,而风不仅加速风化 ,进行风蚀 ,并不断把风化物搬运走。作者综观国内外各类壶穴 ,并结合自己的研究成果 ,对壶穴的成因进行了类型划分 ,这些成因皆反映了特定的环境背景。本区古人类文化相当发达 ,壶穴正是在夏家店文化年代跨度内达到了相对稳定 ,气候环境、地貌过程、文化类型三者存在很好的响应互动关系。 相似文献
14.
15.
丹霞山顺层洞穴风化特征的试验研究 总被引：1，自引：1，他引：0
以丹霞盆地丹霞组2段顺层洞穴为研究对象,探讨不同岩性红层抗风化能力的差异,重点关注软岩夹层的风化特征及其对顺层洞穴发育的影响。在野外考察的基础上,选择3个典型顺层洞穴为案例,采集了洞穴剖面不同岩性红层的岩样及夹层水样品,进行一系列的岩矿理化测试和水样分析实验。结果表明：洞穴剖面岩性的不均一性及软岩夹层的风化凹进是形成丹霞山顺层洞穴的主要原因。顺层洞穴发育的软岩夹层一般是粉砂质泥岩,粘土矿物含量高,以泥质胶结为主,吸水性较强,开型空隙率较大,抗压强度小,易于风化破碎;上下岩层主要是砂岩和砂砾岩,以钙质和铁质胶结为主,吸水性较弱,开型孔隙率较小,抗压强度较大,风化速度较慢。在洞穴岩层风化过程中,粘土矿物的胀缩、钙质胶结物的溶解, 及铁质胶结物的水化作用等是导致岩体结构破坏的重要因素,但促使不同岩性红层风化的主导因素有所差别。粉砂质泥岩的风化以粘土矿物的胀缩作用为主,砂岩和砂砾岩的风化则以钙质胶结物的溶解作用为主。此外,酸性雨水渗入岩体后与各种矿物进行的一系列离子交换作用也促进了顺层洞穴岩层的风化。 相似文献
16.
柴达木盆地那棱格勒河流域是我国目前最大的盐湖型锂矿区和工业设施最为完备的卤水锂工业基地,长期以来关于其尾闾盐湖区锂的物源问题备受关注。尽管目前的众多研究已经对流域内地表水体及尾闾区盐湖中锂的物源有了较为一致的看法,但盆地周缘围岩风化过程在其中起到的作用仍缺乏系统性认识。基于部分保守性微量元素在物源示踪研究中的重要作用,本文通过对流域内河流表层沉积物中的REEY、Li、Sc、Co、Nb、Ta、Th等微量元素开展其地球化学行为方面的分析,讨论了沉积物的物源属性特征及其中锂的来源特征,为深入认识盐湖区游离态锂资源的物源提供了新的证据。结果表明,那棱格勒河流域与毗邻的东、西对比区河流沉积物有着相似的化学风化背景和基岩类型,源岩具有显著的长英质岩和基性岩的二元混合特征,且基性源岩所占比重更大;而沉积物中的锂除尾闾盐湖区明显受到富锂孔隙水体夹带的影响外,其它地区锂的来源特征与沉积物的物源特征相同,表明地表迁移过程对介质中锂的通量影响较弱,沉积物中的锂更多的是以赋存在相关矿物结构中的形式存在;研究区来自源岩风化作用提供的游离态锂的量较为有限,尾闾盐湖中的锂资源主要以昆仑山深大断裂带涌出的热泉水的长年补给为主。 相似文献
17.
Effects of direct and indirect heating on the validity of rock weathering simulation studies and durability tests 总被引：2，自引：0，他引：2
Rock surface and subsurface temperature responses in samples exposed to direct heating (insolation) under natural hot desert conditions reveal considerable variability between lithologies related to differences in thermal properties, especially albedo and thermal conductivity. However, when the same samples are heated indirectly by air in an oven-based environmental cabinet, lithological differences in temperature response disappear and all samples attain temperatures similar to the air temperature within the cabinet. Rates and patterns of rock decay produced in such environmental cabinets may not, therefore, reflect those encountered under natural conditions, where breakdown is related to micro-environmental conditions at the rock/air interface and where rock temperature is one of the most important controlling factors. In addition to implications for assessment of weathering effectiveness, use of only indirect forms of heating affects the determination of comparative rock durability because all rock types are cycled through the same temperature regimes. Because temperature exerts such a major control on rock breakdown through its control on physical and chemical weathering processes, all significant factors influencing it must be included in the design of weathering simulations and durability tests. 相似文献
18.
对内蒙、河北等地新近发现的壶穴进行详细的计量及采样分析，并参考国内外相关研究资料，认为本区壶穴是非冰成的风化风蚀穴。它的发育受到风、温度、降水、湿度、生物、地貌及岩体的结构构造等多种因子的控制。其中风化，尤其是盐风化等化学风化，是其主要控制因子，而风不仅加速风化，进行风蚀，并不断把风化物搬运走。作者综观国内外各类壶穴，并结合自己的研究成果，对壶穴的成因进行了类型划分，这些成因皆反映了特定的环境背景。本区古人类文化相当发达，壶穴正是在夏家店文化年代跨度内达到了相对稳定，气候环境、地貌过程、文化类型三者存在很好的响应互动关系。 相似文献
19.