Summary of site:
The term ‘esker’ is derived from the Irish and describes gravel ridges. The village of Eskragh and its eponymous river are in an area strewn with many such features. Between Corkhill and Brackagh a series of sinuous ridges, some bifurcating, are prominent features in the landscape.
The exposure described in the full account is 1km south of Eskragh village and shows a section across one esker. It consists of concentric beds of gravel, 30-50cm thick, separated by thin, intermittent sands. The pebble particle size in the gravels is generally less than 10cm, except for the right side of the exposure where boulders more than 40cm across form loose layers. The core of the esker has tabular units of sediment inclined at 25-50º to the south. Sediments on the flanks of the ridge have slumped and are inclined outwards at around 45 degrees.
This esker was formed within the ice by meltwater coursing through curved ice tunnels at high velocities. It was finally choked by the rock fragments it was transporting and the arched bedding of the gravels, their inclination, the sandy partings and the collapsed flanks (following melting) are typical features. In curved tunnels, full to the roof with high velocity water, the flow tends to be helical (i.e. spiralling); the larger boulders, corkscrewing along, will tend to lodge on the inside of bends in less turbulent water, exactly the situation seen in the outcrop. This esker is believed to have formed south-west to north-east.
The section is likely to be similar to others in the immediate area which are typically 600-800m long.