Dale, Mary Louise

2018-05-22T12:38:11Z

2018-05-22T12:38:11Z

1981

Only the rock wall parts of cirques may be consistently defined and delimited. They form the basis of a study of glacier source areas in part of the Scottish Highlands. The rock walls data were abstracted from the recently published photogrammetrically contoured 1:10,000 O.S. maps, with the aid of aerial photographs.

The distribution of cirques in the Highlands has long been attributed to a mean annual precipitation pattern during glaciation similar to that of the present day. From morphometric and trend surface analyses of rock walls a more complex set of relationships emerges. The location, size, shape and aspect and altitudinal distributions are determined by the regional and local rates of glacierization and the neighbouring topography, as well as by a precipitation gradient that was much steeper than at present.

Because of the wide variety in potential for glacierization across the study area erosion rates varied and erosion was not synchronous. In the many cycles of erosion during the Quaternary (as indicated by oceanic core evidence) there were times when the most favourably sited, but often small, rock walls were eroded, but also long periods when these were submerged below major ice bodies and the large rock walls at high altitudes were eroded more slowly. The best-developed rock walls occur on the western islands where they were advantageously placed for precipitation and were seldom over-ridden by external ice.

The azimuths of rock walls are clustered about NE. The contribution of lee effects (precipitation and prevailing wind) to this distribution pattern is considered through the statistical examination of plateaux above rock walls. Plateaux to the SW of rock walls are most consistently correlated with rock wall base altitudes, indicating winds predominantly from that direction. A model of radiation incident on rock walls of various azimuths and angles was constructed to identify the contribution of shading from direct sunlight to glacierization of rock wall sites. This is found to be only locally effective at northerly facing rock walls. In the formerly driest parts of the study area the availibility of plateaux is the more decisive factor in determining rock wall locations and altitudes. It is inferred that the average winter synoptic situation during glacierization was cyclonic, with fronts accompanied by south-easterly to southerly winds lying across the area. Following the passage of each depression winds veered to a prevailing south-westerly direction.

http://hdl.handle.net/1842/30152

The University of Edinburgh

Annexe Thesis Digitisation Project 2018 Block 19

Already catalogued

Rock walls in glacier source areas in part of the Highlands of Scotland

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy