辐射沙脊群海域悬沙场遥感反演方法   总被引：1，自引：1，他引：0  

潘进  丁贤荣  康彦彦  葛小平  李森 《地理空间信息》2013,11(2):82-84,87

利用2006年江苏908调查水文泥沙测验数据和同期MODIS影像建立遥感定量反演模式,获取了半个潮周期的悬沙场以及全潮平均悬沙场,进行了辐射沙脊群海域悬沙场遥感反演方法的研究,并结合悬沙数学模型对结果进行了验证。研究表明,在辐射沙脊群海域,敏感参数(B1-B4)/(B1+B4)的对数模式反演悬沙场精度较高;遥感反演结果在总体上与数学模型计算结果相似,悬沙高值区主要分布在弶港、废黄河口和长江口附近;在细节上比数学模型表现得更精细,能清晰地反映河口、沙洲、水道等地貌对悬沙分布的影响。  相似文献   

Beach Ridge Geomorphology at Cape Grinnell,northern Greenland: A Less Icy Arctic in the Mid-Holocene     

Owen K. Mason 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):337-355

Geografisk Tidsskrift—Danish Journal of Geography 110(2):337–355, 2010

In northern Greenland, the Cape Grinnell beach ridge plain offers a 9,000year multi-proxy record for isostatic recovery, storm history, and the hydrological changes related to precipitation and slope evolution. The chronology of uplifted beach ridges is constrained by ten geological 14C ages on shell and sea mammal bones and eleven upper limiting ages from archaeological sites that span the last 3,000 years. Beach ridges formed under the influence of open water storms with renewed frequency and intensity ca. 3 ka and 1 ka ago. A lack of shell may reflect cooler sea surface temperatures. The presence and absence of ice can be inferred by push-features. Three intervals of heightened precipitation produced extensive fan deltas: (a) after 9 ka BP (b) prior to 4.5 ka BP and (c) during the Little Ice Age (AD 1350–1900). Active solifluction lobes and colluvia cover beach ridge deposits that are between 9 and 7 ka old.  相似文献   

Coarse clast ridge sequences as suitable archives for past storm events? Case study on the Houtman Abrolhos,Western Australia     

Anja M. Scheffers  Sander R. Scheffers  Dieter H. Kelletat  Peter Squire  Lindsay Collins  Yuexing Feng  Jian‐Xin Zhao  Renaud Joannes‐Boyau  Simon Matthias May  Gerhard Schellmann  Heather Freeman 《第四纪科学杂志》2012,27(7):713-724

Prehistoric storm records are relatively scarce in most parts of the world. This article presents storm records derived from coral rubble‐based geological archives of the Houtman Abrolhos Archipelago located off the west coast of Australia, where the southernmost coral reefs of the Indian Ocean are found. Winter storm swell from the circum‐Antarctic ‘Brave Westerlies’, as well as tropical cyclone waves, have left numerous ridge systems on dozens of islands of the archipelago, all composed of coral rubble from adjacent reefs. At three islands, seven ridge systems were dated by three different methods: U‐series (68 dates), radiocarbon (64 dates), electron spin resonance (7 dates); 139 radiometric dates span the last 5500 years of the Holocene. In contrast to the geomorphological interpretation, the age sequences show ‘inversions’, hiatuses and different ages for the same ridge, all pointing to complicated ridge formation processes. Time gaps, some exceeding 1000 years, are interpreted as phases of erosion and not as phases without storm activity. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

DEPOSITS FROM LANDSLIDES AND AVALANCHES TRIGGERED BY SEISMIC ACTIVITY IN SWEDISH LAPLAND     

JAN LUNDQVIST 《Geografiska Annaler: Series A, Physical Geography》2010,92(3):411-420

In the mountain area of Swedish Lapland, landforms with semicircular or horse‐shoe ridges encircling hummocky ground occur. They are interpreted as landslide or avalanche deposits directly upon, from or adjacent to down‐wasting ice. Since they are restricted to the vicinity of fault scarps in the Pärvie fault system the releasing factor is suggested to be displacement of bedrock blocks or related seismic activity.  相似文献   

Recent progress in submarine geosciences in China     

JIN Xianglong 《海洋学报(英文版)》2013,32(12):1-3

In China submarine geosciences represents a newly established discipline of oceanography, focusing on the oceanic lithosphere, and its interface with the hydrosphere and biosphere. Recently, supported by the National High Technology Research and Development Program and other high-tech development projects, significant progress has been made in the development of advanced technologies and equipment. This en- ables the scientists in China to carry out explorations of the international seabed area in the Pacific Ocean and on the Southwest Indian Ridge. In addition, they have been active in the research activities associated the mid-ocean ridges and western Pacific marginal seas. It is anticipated that this research field will continue to be highly fruitful in the near future.  相似文献   

Morphodynamic implications for shoreline management of the western-Mediterranean sector of Egypt     

Omran E. Frihy 《Environmental Geology》2009,58(6):1177-1189

Although the western-Mediterranean coast of Egypt between Sallum and Alexandria, ~550 km long, has maintained a considerable equilibrium throughout history, developers have built traditional protective structures in an effort to form sheltered recreational beaches without taking into consideration its geomorphologic characteristics, coastal processes and their harmful impact on the coastal environment and human safety. The improper practices in this environmentally valuable region have induced us to undertake an initiative to carry out a morphodynamic analysis to provide a framework for understanding the relationship between coastal morphology and the prevailing dynamic forces. Based on the degree of natural protection or wave sheltering, the study shoreline can be categorized into four distinct morphotypical stretches: (1) high-energy wave-exposed shores and the outer margins of the rocky headlands, (2) moderate to high wave-energy beaches along semi-exposed embayments and bays mostly downdrift of the rocky headlands, (3) low-wave energy at semi-exposed headland lee-sided and pocket beaches, and (4) calm wave-sheltered enclosing water basins for safe anchorages, moorings and recreation beaches. The results deducted will have practical applications for shoreline management initiatives regarding sustained sites suitable for future beachfront development such as safe swimming conditions, sport facilities, water intakes and sheltered areas for vessels. In addition, benefits realized by the understanding of the morphodynamic processes would enhance our awareness of the significance of the role of western coast morphodynamics in supporting sustainable development via shoreline management. As far as sustainability is concerned, the selection of appropriate sites would help avoiding or minimizing the formation of the hard structures needed for creating safe recreation beaches. On a national scale, results reached could provide reliable database for information that can be used in establishing a sustainable shoreline management plan, which is, in turn, an essential part when implementing an Integrated Coastal Zone Management Plan for this region of attraction.  相似文献   

A REVIEW OF THE PALEO­HYDROLOGICAL AND GEOMORPHOLOGICAL CHARACTER OF LAKE NAM CO|SOUTH­CENTRAL TIBET          下载免费PDF全文

《第四纪研究》2009,29(4):655-664

Department of Earth Sciences,Freie Universität Berlin,Malteserstraße 74－100,12249 Berlin,Germany)
The endorheic Lake Nam Co,south Eastern Tibetan Plateau,was selected to investigate the interrelation between drainage basin processes,especially post­glacial glacier decay,and lake level fluctuations. Landforms of the drainage basin are highly influenced by tectonics,superimposed by fluvial and periglacial processes,and locally by glacial and eolian processes. Thus,geomorphological features and hydrological characteristics were compiled for the lake­basin to provide an overview of the landscape character. Data show that during the Last Glacial Maximum melt water from the mountains accumulated fluvial deposits in the foreland. Concurrently,an increase of the lake level occurred which is presently shown by a cliff line all around Nam Co with its base approximately 29m above the present lake level. The Holocene decrease of the lake level is traced by beach ridges. As Nam Co is an endorheic lake post­glacial water loss has to be primarily explained by evaporation and moisture conditions. However,more detailed conclusions on quantitative and chronological patterns of both factors,melt­water input and evaporation output,still remain to be drawn.  相似文献   

Exploring the ocean for hydrothermal venting: New techniques,new discoveries,new insights     

《Ore Geology Reviews》2017

Enumerating active hydrothermal fields on the seafloor has been a challenge since their discovery almost 40 years ago. High-temperature hydrothermal fields are readily discoverable, primarily by detecting mineral-laden plumes, but low-temperature, particle-poor vent fields resist discovery. Decades of exploration for vent fields have covered, though often cursorily, about one-third of the global lengths of both oceanic spreading ridges (OSRs) and volcanic arcs, identifying some 630 active vent fields. About 80% of these fields are on OSRs, and the spatial frequency of those fields is currently estimated as ∼0.5–5/100 km, generally increasing with spreading rate. Over the last decade, however, a few detailed surveys have added sensors capable of detecting ephemeral chemical tracers (oxidation-reduction potential) in addition to standard sensors that detect quasi-conservative optical tracers (such as light backscattering). This approach has revealed a new view of the distribution of venting fields along fast-spreading (>55 mm/yr) OSRs. Studies of four such ridge sections totaling 1470 km length suggest that the present inventory of vent fields may underestimate the true global population of vent fields on fast-spreading OSRs by a factor of 3–6. This increase implies that ridge axes are unexpectedly “leaky” reservoirs, from which hydrothermal fluids escape at far more sites than presently assumed; that the supply of dissolved hydrothermal iron, which may be fertilizing the primary production of the Southern Ocean, is higher than now calculated; and that present estimates of recoverable sulfide tonnage from ridge axes may be too low. Along slow-spreading ridges, which account for 60% of the global OSR length and 86% of known sulfide tonnage, expansive axial valleys present special exploration challenges that will not be easily overcome.  相似文献   

Growth of large-scale bed forms due to storm-driven and tidal currents: a model approach     

M. Walgreen  D. Calvete  H. E. de Swart 《Continental Shelf Research》2002,22(18-19)

An idealized morphodynamic model is used to gain further understanding about the formation and characteristics of shoreface-connected sand ridges and tidal sand banks on the continental shelf. The model consists of the 2D shallow water equations, supplemented with a sediment transport formulation and describes the initial feedback between currents and small amplitude bed forms. The behaviour of bed forms during both storm and fair weather conditions is analyzed. This is relevant in case of coastal seas characterized by tidal motion, where the latter causes continuous transport of sediment as bed load.The new aspects of this work are the incorporation of both steady and tidal currents (represented by an M₂ and M₄ component) in the external forcing, in combination with dominant suspended sediment transport during storms. The results indicate that the dynamics during storms and fair weather strongly differ, causing different types of bed forms to develop. Shoreface-connected sand ridges mainly form during storm conditions, whereas if fair weather conditions prevail the more offshore located tidal sand banks develop. Including the M₄ tide changes the properties of the bed forms, such as growth rates and migration speeds, due to tidal asymmetry. Finally a probabilistic formulation of the storm and fair weather realization of the model is used to find conditions for which both types of large-scale bed forms occur simultaneously. These conditions turn out to be a low storm fraction and the presence strong tidal currents in combination with strong steady currents during storms.  相似文献   

The RAMESSES experiment—V. Crustal accretion at axial volcanic ridge segments—a gravity study at 57°45'N on the slow spreading Reykjanes Ridge     

Christine Peirce  Debbie A. Navin 《Geophysical Journal International》2002,149(1):76-94

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