Major Landforms Research Articles

Filtering SPOT imagery by kriging analysis

Digital images are rich in data, but in many instances they are so complex as to require spatial filtering to distinguish the structures in them and facilitate interpretion. The filtering can be done geostatistically by kriging analysis. It proceeds in two stages. The first involves modelling the correlation structure in the imagery by decomposing the variogram into independent spatial components. The second takes each component in turn and kriges it, thereby filtering it from the others. The paper describes the theory and illustrates it with an example of an analysis of a SPOT image in a forested landscape of the south-eastern United States. Variograms of the three wavebands, originally recorded as digital numbers and for the red and infrared transformed to the logarithms, revealed spatial variation on two distinct scales with effective ranges of 300m and 3km. These variograms and that of the Normalized Difference Vegetation Index (NDVI) were fitted by nested (double) exponential models. The two spatial components in the scene were then estimated separately by kriging analysis and mapped. The maps of NDVI are displayed and compared with data from ground survey. The shortrange component represents an intricate pattern of dissection and its associated vegetation. The long-range component is that of the major landform units and associated ground cover classes.

Aurignacian Settlement Patterns in the Vézère Valley

Etude de la mobilite des groupes aurignaciens du bassin de la Vezere a partir de l'economie de la matiere premiere lithique et de la saisonnalite animale. Ces elements fournissent des donnees nouvelles sur l'extension du territoire exploite, sur le degre de sedentarisation et de saisonnalite humaine

Exploring Geology on the World-Wide Web – Geomorphology

INTRODUCTION Long before we collect and study in detail rocks in the field, we learn to observe and interpret the lay of the land. From the jagged peaks and sheer cliffs of a youthful mountain to the sinuous curves of a mature stream, the major landforms themselves tell us much of what we need to know about how a particular region has been molded by geological forces. College-level courses in geomorphology often address both the physical descriptions of landforms, and the underlying processes that created them. If the latter were to be included in this articular column, there would be a significant overlap with environmental geology, glacial geology, sedimentology, volcanology, and a host of other. fields of study that merit entire columns of their own. The primary purpose of this issue, therefore, is to identify those sites that present clear images and simple descriptions of the great variety of landforms a t the Earth's surface. Previous topics of this column and their corresponding hypertext links are available from the web page listed below. All of the URL addresses in the current article will be available on the publication date of the next issue of the iournal. Please visit: htbdl Web site for one of the largest member organizations in geomorphology. Contains the IAG-GEOMORPHLIST, an e-mail distribution list for the international geomorphological community. If you have a technical question that is not answered by the web sites listed below, the directory of subscribers includes e-mail addresses and fields of expertise for several hundred members.

Aurignacian Settlement Patterns in the Vézère Valley

Aurignacian Settlement Patterns in the Vézère Valley

The glacial impact on an exhumed sub-Mesozoic etch surface in southwestern Sweden

AbstractAlong the northern part of the western coast of Sweden, the landscape is characterized by joint-aligned valleys with intervening rock hills. Precambrian bedrock is exposed over large areas and the Quaternary cover is mainly restricted to the bottom of narrow valleys. The well-exposed bedrock exhibits many glacial forms, but recently the major landforms have been interpreted as exhumed sub-Mesozoic etch forms. To gain insight into the relative roles of different processes in shaping the present forms, we studied a granite area where the rock hills contain fractures and narrow clefts with weathering forms and saprolite remnants. Marks of glacial erosion are found only in the upper parts of the clefts, where erosion by subglacial meltwater has exploited weathered preglacial sheeting structures to form furrows with concave cross profiles (p forms). On the summit surfaces, glacial erosion has been of greater importance, but the roche moutonnees found here are also structurally controlled. The main impact of glacial erosion is plucking on the order of tens of metres. Thus, landscapes labelled “areally scoured glacial terrain” can, at some locations, also be described as stripped and slightly incised etch surfaces.

Integrated resource study for conservation and management of Ropar wetland ecosystem, Punjab

Integrated resource study in Ropar wetland ecosystem was undertaken to analyse physiography, drainage, landuse and vegetation status. Various thematic maps have been prepared using black and white aerial photographs on 1:20,000 scale and IRS 1A LISS-II (FCC) on 1:50,000 scale. The Ropar wetland ecosystem is comprised of six major landforms i.e. Siwalik hills, Valley, Piedmont plain, Alluvial plain, River terraces and River courses. The study area show high drainage density with sub dendritic and sub parallel drainage. The area has poor vegetative cover which results in extensive erosion and sedimentation of Ropar lake. The water spread and. qualitative turbidity level in the notified wetland area was also monitored. Anthropogenic pressure, industrial pollution, sedimentation, eutrophication, illegal fishing and flooding have been identified as major threats to the wetland. Keeping in view the threats to Ropar wetland, the conservation measures have been suggested.

Evolution of the Lower Gangetic Plain landforms and soils in West Bengal, India

Three major landforms, Uplands, Old Fluvial/Deltaic Plains and Young Fluvial Plains are identified from the Lower Gangetic Plains of West Bengal, India, on the basis of remote sensing and field studies. Morphologic, quantitative and thermoluminescence studies of soils of the study area have been conducted. Two types of Uplands are recognised: Upland in the west overlain by red soils (autochthonous and allochthonous types) and upland in the north (Barind Tract), characterised by three topographic levels. Aspects of the autochthonous Upland Red Soils (Lower to Middle Pleistocene age) show the ferrugination (ferrisol) phase of development. Soils of the Old Fluvial/Deltaic Plains (6–3 ka) and Lower Level of the Barind Tract have argillic horizons and exhibit the fersiallitisation phase of development. Development of ferrugination and fersiallitisation phases was favored due to the pre-weathered nature of the parent material. Soils of the Old Fluvial/Deltaic Plains, Barind Tract (Lower Level) and Young Fluvial Plains show effects of hydromorphism due to waterlogging in the form of segregations of Fe–Mn oxides/gleying and chloritisation, probably due to ferrolysis in the upper horizons of some of these soils. Neotectonics seems to have affected development of landforms and soils significantly. Due to reactivation of some basement faults in the western region, some tectonic blocks subsided, causing transgression during the Early Pleistocene and at ca. 7 ka. Subsequent uplift of these blocks caused regressions and development of soils on the exposed landscapes. Episodic uplift of the Barind Tract in the northern region may have given rise to three topographic levels. Some faults confine the courses of the Damodar, Ganga and Bhagirathi rivers.

Multistage landform development, with particular reference to a cratonic bornhardt

The multistage concept is explained and illustrated, with particular reference to a bornhardt from the southern Yilgarn Block of southwestern Western Australia. Hyden Rock is a complex inselberg developed on Archaean granite. It probably developed through fracture‐controlled differential subsurface weathering in the Cretaceous, followed in the Eocene by erosion of the lateritic regolith and exposure of the massive compartment as an inselberg. But the variations in fracture density to which Hyden Rock owes its origin developed long before the Cretaceous, probably in the latest Archaean or earliest Proterozoic. The relief amplitude of the residual has increased through the Cainozoic.A rich assemblage of minor forms (basins, runnels, tafoni, pitting, displaced slabs, A‐tents) is developed on the bornhardt and, though their mode of development varies, the origin of many can be traced back to magmatic and tectonic events of Late Archaean and earliest Proterozoic times. Others were initiated at the weathering front during the later Mesozoic, and many have developed since exposure, beginning in the Eocene. A few are related to tectonism during the later Quaternary.The residual is a multistage form. Its development as a major landform can be traced back some 120 million years, and the structures to which the outlines of the bornhardt, and those related to several minor features, originated in later Archaean times. The geomorphological evolution of landforms of the shield lands and cratons extends over vast ages and cannot be regarded as a geologically recent phenomenon.

Different Agroecosystem Productivities Across Three Landforms with Similar Natural Productivities in Central Himalaya

ABSTRACT This paper compares the agricultural productivity with that of natural vegetation in three major landforms (mountains, foothill belts, and adjacent plains) of the Central Himalaya, and causes of difference or similarity in productivities are examined. In the hills, the average net primary production (NPP) of rainfed agriculture was about two times lower than that of the average irrigated (valley) hill agriculture. Compared to hill agriculture the NPP of bhabar (foothill belt) agriculture was much higher. On average, tarai (adjacent plain) agriculture was about twice as much as that of the bhabar, and several times greater than hill agriculture. The average NPP of rainfed crop fields of hill agriculture realized only about 13% of the average NPP of natural forests. The NPP of bhabar (foothill belt) agriculture was 32% lower. The NPP of tarai (adjacent plain) agriculture was generally higher than that of the natural forests. This study emphasizes that different agricultural productivities can be obtained in a region having similar productivities in natural ecosystems due to the difference in vulnerability of the land, subsequent removal of natural biomass, and differences in socio-economic conditions.

Human Resources and Sustainable Agriculture: A Case Study from Central Himalaya

ABSTRACT This study analyzes human labor as a renewable resource to develop sustainable agriculture by taking examples from a regional landscape of the Central Himalaya. The technology level in agricultural systems of the studied region (Kumaun) differs with change in the major landforms, viz., traditional in mountain, transitional in the foothill belt, and modern in the adjacent alluvial plain. Human labor contributes 63–65% of the total power in traditional agriculture, about 30% in transitional agriculture, and 8% in modern agriculture. Contribution of human labor input to the total energy input decreases towards the modernization. In traditional agriculture, more time was devoted to yield collection and soil preparation operations. Human labor efficiency increased towards the modernization. With labor saving devices, human labor in transitional agriculture was more efficient than in modern agriculture. Using manpower as a renewable resource, with a suitable framework of technology, can be a useful tool in sustainable agriculture.

Relationships Between Grass, Shrub and Tree Cover on Four Landforms of Semi-Arid Eastern Australia, and Prospects for Change by Burning.

The range of grass, shrub and tree levels present in the Louth region of western New South Wales was determined in an area where woody weeds are considered to be rampant, and the prospects for change by burning were evaluated. Relationships between the three vegetation elements in each of four major landforms were determined by regression and reduction in the canopy cover of woody vegetation after one or two fires were simulated. Basal cover of grass was negatively related to canopy cover of woody vegetation, except in the Sandplains and Dunefields landform. The relationship here was curvilinear with maximum grass cover occurring at 10% canopy cover of the woody vegetation. Pastoralism was considered to become less efficient when the canopy cover of woody vegetation exceeded 5%; 44% of sites measured were below this threshold. The remaining sites could be divided into two groups; one which would fall below the threshold if burnt with a prescribed fire (21%) and the other which required two fires or an equivalent second treatment to reduce the cover below the threshold (35%). The survey confirmed the perception of pastoralists, administrators and scientists that shrub cover is unacceptably high for pastoralism throughout much of the region. Additionally the perennial grass cover was very low and this would increase the instability of forage supply to pastoral herbivores. The high spatial variability in the composition of vegetation indicates that graziers need to identify and treat areas where return on investment in rehabilitation will be highest and most certain.

Ecological classification and analysis of wetland ecosystems, northern Lower Michigan, U.S.A.

We describe an ecological, multifactor approach to wetland classification in which ecosystem types are identified on the basis of the simultaneous integration of physiography, climate, hydrology, soil, and vegetation. Aerial photographs and field reconnaissance were used to characterize the diversity of wetlands of the 4000-ha University of Michigan Biological Station, northern Lower Michigan. Twenty-eight wetland units, including nutrient-rich swamps, ombrotrophic bogs, and many intermediate types, were identified. Eight wetland ecosystems, composing 79% of the total wetland area, were sampled extensively and classified primarily on the basis of the major glacial landforms and physiographic features of the region. Canonical variates analysis was used to evaluate the distinctness of these physiographically determined units in relation to various biotic and abiotic variables. Wetland types were poorly discriminated by canonical variates analysis of overstory composition data; better separation among types was achieved using ground-flora vegetation, hydrology, or soil characteristics. To demonstrate the utility of the multifactor approach to applications in wetland ecology, vegetation–environment relationships were examined using canonical correspondence analysis. Patterns of ground-flora community composition across all ecosystems were related to substrate characteristics, primarily organic matter composition, in addition to water chemistry and light. The results suggest that a multifactor approach, within a landscape framework, is useful in distinguishing wetlands at local scales, particularly where differences in overstory vegetation among ecosystems tend to be masked by human-caused disturbance. However, the landform-mediated differences in various wetland characteristics that we observed argue for a consideration of landscape-level physiography in classification and management even at broader scales.

Major volcanic landform formation on Venus: Possible determination by compression tectonics and crustal thickening

While low level shield volcanoes have formed on Venus, major volcanic structure formation in Ishtar Terra has been restricted to caldera formation. It is possible that the combination of compression tectonics and crustal thickening inhibits the amount of magma which reaches the surface in Ishtar Terra. In certain situations, coronae on Venus may form as undeveloped volcanic structures due to restricted magma rise in thick crustal areas.

PROBABLE PALEOPERIGLACIAL MORPHOSEQUENCES IN THE NORTHERN BLUE RIDGE

Isolated occurrences of different types of bouldery deposits and diamictons in the Central Appalachians have been documented in the literature and attributed to accelerated freeze-thaw during Pleistocene cold intervals. These features have never before been examined together as a suite of genetically related landforms in a regional context. This paper documents the character and distribution of major paleoperiglacial landforms and deposits in the Northern Blue Ridge, including block streams, block-covered slopes, tors, and scarps. The distribution of these features was found to be governed by rock structure and thickness of outcrops; other variables, such as elevation, aspect, and proximity to the glacial border, were of less importance. These features are now stable, in decay, and therefore relict. [Key words: scarps, tors, diamictons, block streams, paleoperiglacial, Northern Blue Ridge, Central Appalachians.]

Geomorphologic environment and age of supergene enrichment of the Cuajone, Quellaveco, and Toquepala porphyry copper deposits, southeastern Peru

Copper ore grades of the Cuajone, Quellaveco, and Toquepala porphyry Cu(-Mo) deposits, situated at 3,000 to 4,000 m a.s.l. on the Pacific slope of the Cordillera Occidental of southernmost Peru (lats 17 degrees 02'-17 degrees 15' S), have been markedly increased by supergene sulfide enrichment. Following the emplacement of the hypogene mineralization in the early Eocene (52-57 Ma) as the terminal stage in the development of the Toquepala Group continental volcano-plutonic terrane, this Andean transect was gradually reduced by erosion in a semiarid climate to a low altitude topography; unroofing of the deposits had taken place by the mid-Oligocene. The initiation of cordilleran uplift at ca. 25 to 26 Ma, accompanied by the episodic eruption of felsic ash-flow tuffs at the oceanward front of the volcanic arc, led to more rapid erosion and the conversion of the mid-Tertiary landscape into the subplanar Altos de Camilaca surface. This regionally extensive pediplain constitutes the major landform component of the present precordillera surrounding the porphyry centers; its final configuration was attained at ca. 18 to 19 Ma. Ash-flow tuff eruption was widespread and frequent at this time.Supergene enrichment began in the late Oligocene during the progressive lowering of topography and continued through the more abrupt water-table depression resulting from the latest Oligocene to early Miocene uplift. However, the distribution of chalcocite, sensu lato, in the three porphyry deposits and the local postmineralization landforms and volcanic histories differed significantly during the latter interval. At Toquepala and, to a lesser extent, Quellaveco, the landform regimes were dominated by open valleys and ignimbrite blanketing was short-lived, whereas the exposed Cuajone deposit was both the site of aggressive early Miocene valley incision and the deposition of an unusually thick, in part welded, ash-flow tuff at 22.8 + or - 0.7 Ma. As a result, the enrichment blanket at Cuajone remained relatively thin and was even partially eroded in the early Miocene, whereas the blankets at Quellaveco and Toquepala were thickened.Continued strong uplift in the mid-Miocene (ca. 8-15 Ma) generated the array of apron and terrace pediments of the Multiple Pediment stage which dominates the lower cordilleran slopes and, in the mineralized areas, led to the deepening of existing valleys and the development of new fluvial channels. Ignimbrite eruption persisted throughout the Miocene. Again, local regimes of erosion and volcanism proved inimical to supergene activity at Cuajone, but enrichment continued at Quellaveco and, particularly, Toquepala, where there is no record of later Miocene ash-flow accumulation. Uplift in this period was apparently also most extensive in the vicinity of the Toquepala deposit, which experienced the formation of a deep chalcocite blanket, while the extant enrichment zone at Quellaveco was thickened.The development of enriched assemblages containing massive chalcocite had clearly terminated by 13.1 + or - 0.4 Ma at Cuajone and by 9.5 + or - 0.5 Ma at Quellaveco; the timing of later enrichment at Toquepala is less constrained, but a mid-Miocene age is probable. Supergene upgrading of the three Peruvian deposits was contemporaneous with that of copper mineralization in northernmost and northern Chile, as at Chuquicamata and La Escondida, and in the Copiapo mining district, in all of which areas a late Oligocene to mid-Miocene age has been inferred for supergene alteration. This major and regionally developed metallogenic episode took place during and between two major periods of cordilleran uplift, under semiarid climatic conditions. The termination of intense enrichment along this 2,000-km stretch of the Cordillera Occidental in the late Miocene was a direct result of marked climatic desiccation, which not only reduced the overall supergene activity but focused fluvial erosion, leading to the incision of steep-walled canyons less favorable for supergene alteration than the earlier subplanar landforms.

Constraints from deep crustal structure on long-term landform development of the British Isles and Eastern United States

It is assumed that some major landforms not easily explained by surface geology could be controlled by deep crustal properties. The concept was first applied in the British Isles and then to the U.S. Atlantic provinces. Both regions were affected by similar orogenies in late Precambrian/Paleozoic times and presently belong to the passive margins of the North Atlantic Ocean. In both areas, the pattern of rifting was greatly influenced by preexisting tectonic fabric of the continental crust. In the British Isles, pre-Mesozoic structures are cut obliquely by the Atlantic margin, while in the U.S. border, the present margin is nearly parallel to the Paleozoic sutures. The British Isles were affected by differential block-tectonics during the Tertiary. Examples are given of regional-scale landforms linked with crustal hinges. Recent data confirm the great heterogeneity of the crust beneath the British Isles. Each crustal unit has its own isostatic response according to the state of stress and its own dynamic equilibrium between rock resistance, erosion processes and uplift rate. In the Atlantic provinces of the United States, the regional physiographic framework is simpler, but allochthonous terranes thrust westward over the Grenville basement and shelf-sediments have buried some major discontinuities in the deep crust. Reverse faults associated with the NW-SE compressional stressfield are numerous but cannot explain regional-scale landforms like the Blue Ridge escarpment above the Piedmont. Rock control is not the direct cause of the escarpment. The Blue Ridge from reaches its highest relief where discontinuities in the deep crust interfere with surficial geological features. Ocean to continent creep processes are suggested to explain the sustained uplift of the Appalachian highlands and the relatively stable position of the mountainous front since middle Mesozoic times.

The Geomorphology of Rock Coasts

This reference text deals with the geomorphology of rock coasts. It brings together the results of research conducted by coastal engineers, biologists, geologists and physical geographers from many parts of the world. The first section of the book discusses changes in sea level and the effects of mechanical wave action, chemical weathering, solution, bio-erosion, frost, and mass movement on rock coasts. The second section is concerned with the major landforms which result from these processes. These include cliffs, shore platforms, coastal karst, bays, headlands, and elevated marine terraces.

Mire Development, Pool Formation and Landscape Processes on Patterned Fens in Dalarna, Central Sweden

(1) Mire development and pool formation were examined stratigraphically on patterned fens in Dalarna, central Sweden. The palaeoecological study was complemented by mapping of the surface and substratum topography, description of modern landforms, analysis of the water chemistry and diatom flora, and phytosociological study of the vegetation. (2) Forty-three releves are organized into seven noda, which separate along a moisture gradient. The major landforms include mire-margin hummocks, pine islands, ridges, flarks, mud bottoms, and open-water pools. (3) Peat cores along a 900-m transect from the base to the top of one fen slope show that the mire developed through upslope paludification. Basal radiocarbon dates decrease sequentially from 9040 + 80 years B.P. at the base of the slope to 1640 + 50 years B.P. at a point 100 m from the top of the fen. Buried forest soils and stumps of Pinus sylvestris at the base of the peat indicate that forest communities were replaced by sedge fen. (4) Pools and ridges develop through gradual differentiation of the mire surface some thousands of years following mire initiation. The basal 2 m of peat beneath a flark and adjoining ridge are identical until this differentiation began. (5) Deep pools are underlain by more than 1 m of algal gyttja, which grades downward into peat detritus and then peat. Radiocarbon-dated profiles indicate that pools initially deepen through peat degradation before the deposition of algal sediment starts. (6) The surface patterning is dynamic. The total pool area on the mire increases with time and the size, shape and orientation of individual pools may change. Pools expand through gradual submergence of marginal areas as well as through coalescence. Pool drainage may occur through coalescence of pools at different elevations, through ridge erosion, and through subsurface piping. (7) The overall development of the mires involves progressive diversification on two scales. The regional landscape increases in complexity and landform diversity as mires form and replace forest communities. On the mires, local diversification involves the development and alteration of surface features through time.

Ballooning Spiders as a Component of Arthropod Fallout on Snowfields of Mount Rainier, Washington, U.S.A.

In 1975 and 1976, fallout (aerially dispersing arthropods trapped on snow) was collected from large permanent alpine snowfields on Mount Rainier (4392 m), Cascade Mountains. Spiders comprised 5.5% of all specimens collected, being fifth in abundance after Homoptera, Heteroptera, Hymenoptera, and Diptera. Overall, spider fallout density decreased steadily with elevation, probably reflecting a decrease of spider density in the atmosphere with altitude. Spiders from distant sources reached higher elevations. From April to October, spider fallout density (and thus spider dispersal in this area) showed a moderate peak in May/June, a minimum in September, and a high peak in October, similar to patterns known elsewhere. Only 5 of 23 spider species found in fallout were previously known as ballooners. Species ballooning as adults belonged to the families Araneidae, Theridiidae, Salticidae, and Thomisidae, not just Linyphiidae as previously reported. Analysis of probable origins of fallout species shows the importance of major landforms and weather patterns to success of spider aerial dispersal. Compared with embarkment and flight of ballooners, their immigration has been little studied; alpine fallout is an important potential source of such data.

Machine processing of LANDSAT data for soil survey: the Benue Valley savanna case study

Abstract A ground-truth (GT) map, produced by fieldwork and the interpretation of large-scale black and white aerial photographs, was compared with digital/graphical output from LANDSAT data of the savanna around Makurdi in central Nigeria. The GT maps were digitized, grid-converted and then aggregated while the LANDSAT data were resampled for the purpose of rectification on the ERDAS 400 microcomputer at the Michigan State University. A visual comparison of the maps was done by overlaying the digital maps on the GT map using a colour monitor while the histogram listing provided an approximate quantitative comparison. The two algorithms of supervised classification (maximum likelihood and minimum distance) produced similar results but the third unsupervised classifier algorithm, cluster analysis, produced a far simpler map that is ideal as a reconnaissance soil/resource survey map. The major landforms were recognized by image processing but the reflectance-based classification resulted in misgroupings bec...