Drumlins
Describe the spatial characteristics of drumlins in Ireland and explain their relationship to the evolution of the last lowland ice sheets in Ireland.
Drumlins are undoubtedly among the most intensively studied of all glacial landforms and have bee particularly widely used as ice-directional indicators. They frequently occur in ‘fields’ or ‘swarms’ in lowland areas where there was little obstruction to the passage of ice, or in piedmont zones where flow was radiative or dispersive. They are also occasionally found on the floors of glacial troughs. Many are ellipsoidal in form, some kilometres in length have been observed (Lemke 1958). Most possess a prominent stoss end with a trailing distal slope. It is generally agreed with the direction of the drumlin long axis reflects local direction of ice movement with the stoss end usually pointing up-glacier. The ice moulded or streamlined form appears to be produced by variations in stress levels at the base of the ice, although the precise mode of formation of the features is far from clear. The Kingscourt drumlins mentioned below gives a detailed account of the spatial characteristics and it’s internal components. ‘In addition to the regional ice flow trends displayed by their long axes, the overall shape of drumlins can provide information on former glacial dynamics, such as indications of basal ice pressure and rate and type of ice flow (Doornkamp and King 1971)’[1].
The recent work on drumlins has tended to concentrate on three aspects: drumlin shape and distribution, stone orientations within drumlins and theoretical considerations of pressure distributions within the ice and the till. Vernon (1966), in a study of drumlins in County Down, noted that they are concentrated in bands both perpendicular and parallel to ice flow but that their spacing is variable. Doornkamp and King (1971) point out that where drumlin density is high, the drumlins themselves were small. This is not as obvious as it seems,
Drumlins are undoubtedly among the most intensively studied of all glacial landforms and have bee particularly widely used as ice-directional indicators. They frequently occur in ‘fields’ or ‘swarms’ in lowland areas where there was little obstruction to the passage of ice, or in piedmont zones where flow was radiative or dispersive. They are also occasionally found on the floors of glacial troughs. Many are ellipsoidal in form, some kilometres in length have been observed (Lemke 1958). Most possess a prominent stoss end with a trailing distal slope. It is generally agreed with the direction of the drumlin long axis reflects local direction of ice movement with the stoss end usually pointing up-glacier. The ice moulded or streamlined form appears to be produced by variations in stress levels at the base of the ice, although the precise mode of formation of the features is far from clear. The Kingscourt drumlins mentioned below gives a detailed account of the spatial characteristics and it’s internal components. ‘In addition to the regional ice flow trends displayed by their long axes, the overall shape of drumlins can provide information on former glacial dynamics, such as indications of basal ice pressure and rate and type of ice flow (Doornkamp and King 1971)’[1].
The recent work on drumlins has tended to concentrate on three aspects: drumlin shape and distribution, stone orientations within drumlins and theoretical considerations of pressure distributions within the ice and the till. Vernon (1966), in a study of drumlins in County Down, noted that they are concentrated in bands both perpendicular and parallel to ice flow but that their spacing is variable. Doornkamp and King (1971) point out that where drumlin density is high, the drumlins themselves were small. This is not as obvious as it seems,
Bibliography: Ehlers, J. Gibbard, P. Rose J. (1991). Glacial Deposits in Great Britain and Ireland. Rotterdam. Balkema, Hepworth Holland, C Lowe, J. J. Walker, M.J.C. (1984). Reconstructing Quaternary Environments. London. Longman. Price, R.J. (1973). Glacial and Fluvioglacial Landforms. Edinburgh. Oliver and Boyd. [2] Price, R.J. (1973). Glacial and Fluvioglacial Landforms. Pp 80. [3] Coxon in Hepworth Holland, C. (2001). The Geology of Ireland. Pp 416. [5] Coxon in Hepworth Holland, C. (2001). The Geology of Ireland. Pp 419. [6] Coffaigh (1996) in http://ppg.sagepub.com/cgi/content/abstract/20/1/1 [7] Price, R.J