摘要:

AbstractThis paper supplements earlier reports on palsas and pingo-like frost mounds in northeasternmost Scandinavia (Fig. 1) and treats a form of circular to oval lakes having characteristics of both the palsa and the pingo form groups. The lakes differ from other lakes of regular shape by being enclosed by a low, uniform wall.The circular lakes are interpreted as a collapse stage of frost mounds, which may have originated as palsas or as pingos. Also, some localities with fossil circular forms have been observed, mostly situated at lower elevations.The climatic significance of the collapse features is briefly analyzed in comparison with that of the palsas. For the fossil, low-elevation rings, a climatological and temporal interpretation is advanced referring to radiocarbon dating and to the occurrence of fossil ice-wedge polygons in the area.

ISSN:0435-3676    

DOI:10.1080/04353676.1969.11879787

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractInternal drainage was studied on Mikkaglaciären and Storglaciären in northern Sweden by means of salt injections. The internal drainage of Mikkaglaciären was found to occur in two separate systems in semilateral positions, systems corresponding on the surface of the glacier to areas of crevasses with different strike directions (cf. Stenborg 1968). The relative amounts of ablation for the different areas could be correlated with the discharge in the corresponding frontal streams.The drainage model devised for Mikkaglaciären is assumed to be valid for other glaciers with the same main characteristics. It appeared to be applicable to Storglaciären, with one exception, caused by a topographical anomaly. In connection with this anomaly, a re-arrangement of the drainage took place between the two years of observation (1960 and 1968).Summaries of the investigations and conclusions concerning Mikkaglaciären and Storglaciären are given on page 26 and on pages 30 and 34 respectively. Some general views on methods (use of tracers), on the physical possibilities of drainage penetration and the development of internal drainage courses, and on the glaciological and morphological applicability of the drainage model devised for Mikkaglaciären are given in separate sections (pp. 14 f. and pp. 36 ff.).

ISSN:0435-3676    

DOI:10.1080/04353676.1969.11879788

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractA sediment core from Trullvatnet, a lake at 1 m a.s.l. in the inner Murchisonfjorden area, northwestern Spitsbergen, was examined. The sediments in the 3 m-long core cover a period of about 7000 C14years and show a sequence of two marine-lacustrine contacts in the lower region. The renewed connexion with the sea of the basin between 5500±140 and 4745±120 C14years ago, followed by a final isolation, suggests an interruption in the general negative trend of shoreline displacement.

ISSN:0435-3676    

DOI:10.1080/04353676.1969.11879789

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

ISSN:0435-3676    

DOI:10.1080/04353676.1969.11879790

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractThe results of 64 till fabric analyses taken from three superposed tills are described. Analysis of the fabric of the basal till shows that Highland ice moved across the Lothians from W to E. Over some parts of the district, the basal till is covered by the intermediate till. The consistent regional fabric pattern of this till indicates Southern Uplands ice-movement from SW to NE. Finally the uppermost or Roslin till is seen to represent a minor readvance probably from the north.The present till fabric results from the basal till agree closely with the classical nineteenth century fabric analyses carried out around Edinburgh.

ISSN:0435-3676    

DOI:10.1080/04353676.1969.11879791

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractVery commonly small-scale current ripples display wave-like changes of elevation in a direction transverse as well as parallel to current flow. It is shown theoretically. and confirmed experimentally, that such changes of elevation of a rippled bed record an adjustment of the bed to a three-dimensional fluid motion. Combined with the basic flow, which is characterised by transverse regions of flow separation, are corkscrew vortices parallel to flow that resemble Taylor-Görtler vortices. The instability leading to these vortices in the flow over a rippled bed very probably is largely of centrifugal origin, since there are regions in the flow where the circulation decreases away from the local centres of streamline curvature.Experiments made with beds of a fine-grained quartz sand reveal that the characteristic wavelength of features due to the vortices diminishes with increasing relative roughness and Froude number of flow. But as the stream-wise crest-to-crest distance of ripples changes but little with either relative roughness or Froude number, over the greater part of the practical range of these parameters, the result of an increase of flow roughness or speed is to make ripples more irregular, as is shown quantitatively from the experiments. We find empirically that the mean wavelengths of the spanwiseand streamwisefeatures of a rippled bed are related to relative roughness and Froude number by the expressionin whichis the mean ripple height,is the mean flow depth, andFris the Froude number based on mean flow depth and velocity. This expression appears applicable to the much larger dunes formed in water, which also commonly display wave-like ridges and furrows parallel to flow. In having lee projections, certain transverse desert dunes resemble ripples and dunes found in water, and would appear affected by centrifugally unstable wind flows. Wavelength ratios for these dunes overlap in value with ratios measured from subaqueous bed forms.

ISSN:0435-3676    

DOI:10.1080/04353676.1969.11879792

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor