摘要:

AbstractDuring 1959–63 cirque forms in Swedish Lapland were inventoried by air photo interpretation in combination with field checks. Some field work was also performed during 1970–71.The concepts of glacial cirque and nivation cirque are briefly discussed as well as some systems to classify cirque forms. The author also presents a classification system of his own.On the enclosed point map the regional distribution of quite 2000 cirque forms can be studied. About half of them are regarded as glacial cirques. Some characteristics in their regional distribution are pointed out, e.g. mountains rich in cirque forms in relation to mountains with few forms. Formations, supposed to be cirque stairways, are mentioned.The vertical distribution of the cirque forms is described and discussed with regard to cirque type as well as to variations within the investigated area—particularly from east to west but even from north to south. In this connection special attention is paid to the lowest cirque forms and their importance as indicators of lower glaciation levels.The orientation (aspect) of these Laplandish cirque forms is studied too, e.g. with regard to cirque type and regional variation. An attempt is made to analyse such factors that are thought to be determinative for the cirque aspect. Thus the author discusses prevailing winds and general topography, exposure to sunlight and rock type/rock tectonics. As a link in these analyses the attitude of about 6000 joints and cleavage planes were measured and plotted on fabric diagrams—some of them are presented in this paper. A few concluding remarks on the age of the cirque forms are made too.The paper is illustrated by photos, maps, sketches, diagrams, tables, and plates.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879948

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

ABSTRACTTopoclimatic effects on glacier balance encourage shade, lee and east-facing glaciers in varying combination in different regional climates and at different altitudes. Present-day glaciers usually face slightly east of poleward on average: in Scandinavia and the Urals, consistent westerly winds strengthen the lee tendency, especially where gentle summits favour drifting of snow. Eastward cirque aspects are found in the Falkland Islands, New Hampshire and Central Spain, east-northeast aspects in the American Rockies, the Faeroes, Central Europe, Japan and Tasmania. In Scandinavia, the British Isles and the Carpathians, northeastward resultants are most common, showing a lee effect tempered with a shade effect. Elsewhere (in the Canadian Arctic, Alaska, British Columbia, western U.S.A., central Chile, the Alps, southwest and central Asia, the Altai and even Papua—New Guinea), both cirque and glacier aspect resultants are poleward or within 30°further east. This situation reflects differential ablation from direct solar radiation as a more important factor than wind. Cirque aspects provide a constraint on palaeoclimatic reconstructions but cannot provide precise information on palaeowind directions.The degree of asymmetry (vector strength) varies more locally and is usually greater in ranges which were only just high enough to nourish glaciers. For a temporal comparison of glaciers with cirques, this observation may be formalised as a“law of decreasing glacial asymmetry with increasing glacier cover”.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879949

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

ABSTRACTResults of measurements of cirque size, shape, site and aspect are presented for the Kintail-Affric-Cannich area of northwest Scotland and are compared with those derived for cirques elsewhere. The correlation structure of the descriptors suggests that as cirgue size increases, the degree of cirque enclosure increases in both plan and profile dimensions, and overall cirque gradient decreases. As size increases, length also tends to increase slightly relative to cirque amplitude, but length to breadth ratio remains relatively constant. The assumption of a space-time transformation leads to the hypotheses that cirque headwall retreat proceeds slightly faster than downcutting and that semicircular equilibrium forms are not developed in this area.Variations in cirque morphometry and location are largely the function of local-scale, rather than macro-scale factors, in particular the maximum altitude of the area draining into each cirque.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879950

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

ABSTRACTOne of the most fundamental ways in which ice sheet erosion modifies the topography is by altering the valley pattern. It is assumed that purely fluvial valley systems are dendritic in pattern. This presumably represents the pre-glacial state. Purely alpine glaciation will tend to retain the dendritic system, whereas if active ice sheets take over, the landscape will become progressively modified by multiple watershed breaching, so that the valleys become increasingly inter-connected. This assumption is tested by using topological measures of network connectivity, applied to the valley pattern of Scotland. Several areas in West Greenland and British Columbia are used for comparison. The most suitable measure of network connectivity appears to be theα-index. Values in Scotland range from 0 % (indicating a wholly dendritic pattern) in the southeast of the country to>7 % around the southwestern Great Glen and in Wester Ross. The results seem to fit what is known about the pattern of glaciation from other evidence, though some interesting problem areas like the Glenshiel district are revealed. Mountainous islands which develop their own radial system of ice outflow have prevented the mainland ice from altering their valley pattern and so retain the low values ofαassociated with alpine glaciation. Results from West Greenland and British Columbia fall within the same range.Areas of total glaciation intensity are also derived from a combination of theα-index and the percentage of alpine type valley heads in each area. High intensity corrie glaciation and ice-sheet modification are not necessarily mutually exclusive.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879951

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

AbstractAn analysis of 320 cirques with similar lithology indicates that the depth of cirque erosion varies systematically in relation to the topoclimatic factors, altitude and aspect. Altitude and aspect presumably exert direct control over glacier mass balance thereby affecting variations in the degree of cirque floor lowering. Within the Sierra Nevada Mountains of central California altitude and aspect exert independent effects as well as an interaction effect upon the depth of cirque erosion.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879952

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

AbstractA bedrock form similar to a glacial cirque was found west of Lake Siljan in the province of Dalarna, central Sweden, below 500 m a.s.l. Glacial cirques at such low altitudes have not up to now been described from the central part of Sweden.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879953

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

ABSTRACTFour stratigraphic successions in lacustrine sediments exposed beneath prominent terraces in the Okanagan Valley, British Columbia, Canada, are described. Sedimentation processes are deduced from interpretation of vertical and spatial changes in primary sedimentary structure, texture, attitude and thickness of beds, and palaeocurrent. Summer intervals consist of finely graded and massive silts deposited from turbid inflowing meltwater. In addition thick deposits (>10 cm) of climbing-ripple cross-lamination, and convoluted beds are the result of subaqueous slumps. A mechanism for slumping based on differential compaction of lake bed sediments is proposed.Late summer and winter deposition differs strikingly from the classical varve model. Proximal intervals show rapidly alternating units of structureless sand, current bedded sand and laminated silts. The sands are considered to have been emplaced by slides occurring on delta fronts during drawdown of lake levels at the end of the melt season. Properties of both grain flow and dispersed turbidity underflow deposits are revealed, and a quantitative mechanism for acceleration of grain flows with transition to turbidity flows is presented. Upward thinning of both summer and winter intervals as a result of ice marginal retreat is evident. Final attitudes of the sediment bodies, the deep basins occupied by present day lakes, and terraces underlain by lacustrine deposits are the result of melt out of large masses of glacier ice buried beneath the lacustrine sediments. A model of alpine lake sedimentation based on changing depositional processes with time and distance from the ice margin is presented.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879954

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

摘要:

ABSTRACTThe location of tributary drainage basins nested within higher order systems forms the basis for a proposed classification into order-formative and order-excess subsystems. The significance of these order types in generating distinctions within an order level is examined with a battery of twenty-five network parameters sampled over two contrasting geomorphic environments. The contribution of the order-type effect is found to vary with parameter and data set. Empirical analyses based upon samples of drainage networks defined solely by stream order level are of doubtful interpretation where this variance contribution is ignored.

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879955

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879956

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor

ISSN:0435-3676    

DOI:10.1080/04353676.1977.11879957

出版商:Taylor&Francis    

年代:1977

数据来源: Taylor