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We have measured concentrations of cosmogenic 10 Be and 26 Al produced in situ at bare bedrock surfaces of successive sheets developing on a granite dome in Korea and calculated the exfoliation rate of sheeting joints. The exfoliation rate was obtained using a simple model in which the sheeting joints experience intermittent denudation, i.e. peeling off along the bedrock face. We find that the average exfoliation (erosion) rate of the episodic peeling-off process is 5·6 cm/ka − − − − −1 . The analysis is useful for understanding the evolution of granite sheeting structures on this dome in Korea.impact is applied at various points a few millimetres apart. This technique is used in the present study, with 30 impact points; the mean value from these impacts is denoted by L s .The results show that (1) the surface layer of Sh-1 has the largest strength reduction, i.e. severe weathering; and (2) the strength reduction, i.e. degree of weathering, becomes progressively smaller from Sh-1 to Sh-5 (Table I). These results suggest that the sheets have been exfoliated from Sh-1 to Sh-5 in that order. S. Wakasa et al.erosion of sheets, we estimate the average exfoliation (erosion) rate of these sheets as 5·6 cm ka −1 . This is the average rate of a highly episodic process, and integrated rate, however. The rate at which the hardness of each sheet surface reduces due to weathering was obtained from the relation between the surface exposure duration of the sheet and the values obtained from the Equotip hardness test. The reduction in hardness is rapid early on and then proceeds more slowly, consistent with previous studies. 1256S. Wakasa et al.