**8. Interpreting Discrete Debris Accumulations**

Table 1 (after Whalley, 2009) lists the main features likely to be seen as Younger Dryas Discrete Debris Accumulations in the uplands of the British Isles. This must, at present, be taken as a rather rough typology. It has not proved possible to provide a key system to help identify features. There are three reasons for this. First, the features themselves are somewhat variable in form and location on a hillside. Secondly, the debris input location and type needs to be taken into account (following from Figure 3). Thirdly, the interpretation itself may change. Thus, some of the following photographs show variations in form. The diverse papers about the origin of the Beinn Alligin 'rockslide' exemplifies both the second and third reasons starting with the original description (Sissons, 1975; Whalley, 1976) and with further detailed interpretations (Ballantyne, 1987; Ballantyne & Stone, 2004; Gordon, 1993). A clear example of a change in opinion is that by Wilson, already mentioned, in revising his formation model of some rock glaciers in northern Ireland to be massive rockslides. This view then casts doubt on the interpretation of the rock glacier (in the same geology) on Islay (Dawson, 1977). This also illustrates a further difficulty, that of terminology, a problem that has long bedevilled this area of research, especially that of rock glaciers (Hamilton & Whalley, 1995; Martin & Whalley, 1987).


Using Discrete Debris Accumulations to Help Interpret

glacier.

input to protect the ice.

Upland Glaciation of the Younger Dryas in the British Isles 11

Fig. 6. Terminal area of a small glacier descending from Y Glydder, Snowdonia (SH 625727). This may have been a debris covered section of the lower glacier or even an incipient rock

Fig. 7. Corrie in Tröllaskagi, Northern Iceland where there has been a small glacier but very little debris to protect the ice from melting (Whalley, 2009). The debris cover is left as an indistinct trace after the ice has melted. A neighbouring corrie has a distinct rock glacier feature (Whalley et al., 1995) produced by high ice fluxes but with corresponding debris


Table 1. This table (derived from Whalley 2009), provides a summary of the main discrete debris accumulations likely to be found in the British Isles and Ireland, other than moraines. The features are listed alphabetically but those marked \* are not referred to in this paper. Protalus lobe is equivalent to 'lobate rock glacier' or 'valley wall rock glacier' of some workers. A protalus ramparts is also known as 'winter nival ridge', 'pronival ridge' or 'snow-bed feature'.
