地貌面、地文期与地貌演化——从华北地貌演化研究看地貌学的一些基本理论

华北地貌的形成演化研究以传统地貌学理论戴维斯等的"地貌面"和"侵蚀旋回"理论为指导。研究表明,它基本适用于华北地貌的形成与演化;同时也发现了传统地貌学理论的不足。该文用华北地貌形成演化的实际资料弥补了这个不足,并进一步探讨了地貌形成演化理论的某些新观点。     

《城市地貌学》评介

喜读刁承泰所著《城市地貌学》(西南师范大学出版社,1999.6)一书,甚感欣慰。它为地貌学增添了一本新的学术专著,为城市发展建设中改造利用地貌条件与治理地貌灾害提供了地貌学的研究成果,也是十多年来我国开展城市地貌研究的总结。     

Geomorphology in the system of Earth sciences

We examine the question of determining the place of geomorphology in the system of Earth sciences. The study revealed that, in spite of the differences in understanding the subject matter of science, there are at least seven integrating and generally accepted techniques of geomorphological investigations themselves: orographic analysis, cartometry, remote analysis of hidden landforms, morphometry, geomorphological mapping, modeling of geomorphological systems and conceptual development of the methodology. Emphasis is placed on the important role of geomorphological mapping in understanding all processes on land cover and the history of its development, assessing the natural resources and natural hazards, and in forecasting the evolution of the landscape. The technique of representing results from geomorphological investigations as a geomorphological map requires developing a classification of topographic features and landforms, and publications of A. N. Lastochkin and his followers are specifically focused on this issue. The integrating role of N. A. Florensov’s ideas of concepts concerning the continental orogenesis and geomorphological formations is pointed out. The autonomy of geomorphology in the system of Earth sciences is demonstrated but it is emphasized that it is not possible to further develop geomorphological knowledge outside the province of related Earth sciences, primarily geology and physical geography. A substantiation is given to the exclusiveness of the object of study (topography of land cover) and the subject (main topographic properties: morphology, genesis, age, and morphogenesis processes) which can be analyzed solely by geomorphological research techniques and development models.     

Geomorphology of coal seam fires

Coal fires occur in underground natural coal seams, in exposed surface seams, and in coal storage or waste piles. The fires ignite through spontaneous combustion or natural or anthropogenic causes. They are reported from China, India, USA, South Africa, Australia, and Russia, as well as many other countries. Coal fires lead to loss of a valuable resource (coal), the emission of greenhouse-relevant and toxic gases, and vegetation deterioration. A dangerous aspect of the fires is the threat to local mines, industries, and settlements through the volume loss underground. Surface collapse in coal fire areas is common. Thus, coal fires are significantly affecting the evolution of the landscape. Based on more than a decade of experience with in situ mapping of coal fire areas worldwide, a general classification system for coal fires is presented. Furthermore, coal seam fire geomorphology is explained in detail. The major landforms associated with, and induced by, these fires are presented. The landforms include manifestations resulting from bedrock surface fracturing, such as fissures, cracks, funnels, vents, and sponges. Further manifestations resulting from surface bedrock subsidence include sinkholes, trenches, depressions, partial surface subsidence, large surface subsidence, and slides. Additional geomorphologic coal fire manifestations include exposed ash layers, pyrometamorphic rocks, and fumarolic minerals. The origin, evolution, and possible future development of these features are explained, and examples from in situ surveys, as well as from high-resolution satellite data analyses, are presented. The geomorphology of coal fires has not been presented in a systematic manner. Knowledge of coal fire geomorphology enables the detection of underground coal fires based on distinct surface manifestations. Furthermore, it allows judgments about the safety of coal fire-affected terrain. Additionally, geomorphologic features are indicators of the burning stage of fires. Finally, coal fire geomorphology helps to explain landscape features whose occurrence would otherwise not be understood. Although coal fire-induced thermal anomalies and gas release are also indications of coal fire activity, as addressed by many investigators, no assessment is complete without sound geomorphologic mapping of the fire-induced geomorphologic features.     

The Siberian School of Experimental Geomorphology

This paper considers the results of geomorphological field experiments in Siberia conducted at the permanent stations operated by the V.B. Sochava Institute of Geography SB RAS for a 60-year period and describes the observation methods. A unique database of quantitative data on the modern relief dynamics is provided. The rates of slow mass motions of soils on slopes, and also of the deluvial, aeolian and channel processes are presented. Observations for long-term time series are summarized. Much attention is paid to the results from investigating the slope processes. The contribution of stationary investigations to the solution of fundamental problems in geomorphology is shown. The role of field experiments in understanding the temporal organization of geomorphological systems is emphasized. Dynamic phases of the intrasecular cycles of exogenous relief formation are investigated. Models of the contemporary functioning of denudation systems that cover all possible variety of dynamic phases and morphological and climatic conditions of denudation in semi-arid conditions of southern Siberia are obtained. It was found that the spatial ordering of exogenous relief formation in the south of Siberia is manifested in the form of a regional series of correlative denudational systems whose structure and functioning mode naturally vary along the aridity and continentality vectors of climate. The spatial ordering of aeolian lithostreams is shown, which are involved in a common cycle of matter spinning clockwise and moving aeolian fine material along the northern subarid foothills areas of the mountain belt of Southern Siberia. An important role of the observation results on the relief dynamics for solving ecological problems is pointed out. Prospects for a further development of experimental geomorphological research in Siberia using high-precision instruments, GIS technologies and other modern methods are outlined.     

Geomorphology and late Holocene climatic change in Northeastern Spain

During the late Holocene, accumulation and downcutting stages affected the slopes and infilled valleys in the semiarid areas in NE Spain. The presence of archaeological remains, charcoal and ashes within slope deposits and valley fills makes it possible to carry out accurate datings. In the case of infilled valleys, the different accumulations may be diachronous at a regional level. These diachronisms among different infilled valleys may be caused by both human activity and complex responses of the system. On the slopes, one can distinguish between two accumulation periods separated by an incision period. The older accumulation stage has a widespread distribution and developed from the Bronze Age to the Iberian–Roman Epoch. The following accumulation period was formed in the Post-Medieval period and is spatially more restricted. Because of the widespread synchronism shown by these accumulations, a climatic cause is put forward as the possible triggering factor for the accumulation–incision stages in the slopes. The datings obtained indicate that the first accumulation corresponds to the Iron Age Cold Epoch (900–300 years B.C.) and the second to the Little Ice Age. Between both accumulation periods, a downcutting stage took place (approximately from 300 B.C. to 1450 A.D.). This downcutting interval can be related to the warm stages of the Subatlantic Period, during which there was a relatively lower percentage of vegetation cover. Finally, the last incision period, which is still taking place, has affected previous accumulations.     

Marine Geomorphology in the Design of Marine Reserve Networks

Marine environments, key life-support systems for the earth, are under severe threat. Issues associated with managing these common property resources are complex and interrelated. Networks of marine reserves can be valuable for mitigating threats to marine systems, yet the successful design and implementation of such networks has been limited. Efficient ways to conserve marine environments are urgently needed. This Focus Section of The Professional Geographer explores the development of marine reserve networks based on geomorphology, fish biology, ecological connectivity, and appropriate governance. The articles in this Focus Section offer examples of the following: (1) distinctive reef geomorphology dictating the spawning locations of reef fishes, which in turn serve as critical source sites for the replenishment of distant reefs by means of larval transport; (2) an example of a simplified oceanographic model that predicts larval transport from fish breeding sites to important nursery areas; and (3) a case study of the development of a marine reserve network that illustrates key elements of a successful strategy. In sum, this Focus Section offers case studies that show the value of marine geomorphology, oceanographic connectivity, and stakeholder involvement as key elements of multidisciplinary geographic studies applied to the design of marine reserve networks. Geographers can further contribute to the conservation and management of coastal and marine ecosystems in many ways that involve subdisciplines of remote sensing and geographic information systems, political and economic geography, political ecology, and ethnography.     

Geomorphology of sand dunes in the Northeast Taklimakan Desert

Three types of sand dunes exist in the Taklimakan Desert, namely compound/complex crescent dunes and crescent chains, compound dome dunes and compound/complex linear dunes. Besides these three compound/complex types, single simple dunes are also distributed throughout the sand sea. The compound/complex linear dunes are developed under acute bimodal wind regimes. Though the ratios of the resultant drift potential (RDP) and the drift potential (DP) are the same as that near the border and adjacent area of the sand sea, the compound/complex crescent and dome dunes are developed, respectively, because of divergence of the sand available, the stress of the sand-moving winds and the time scales of dune formation. The sand supply for the dunes is not from Lopo Nor in the east as previous studies suggested but mainly from local alluvial or lacustrine deposits. The grain size component does not correlate evidently to the morphology parameters of the sand dunes. Analyses of the DP and drift direction suggest that the northeast Taklimakan is an area of low wind energy and the resultant drift direction (RDD) coincides well with the distribution, morphology and scales of the dunes.