Pebbles on a mountain side are unlike pebbles worn by the waves. In their tiny peaks and steep inclines they may well bear a fractal resemblance to the mountain on which they rest. Usually rest. For of course the ambient conditions and interior volcanic potential of the mountain can at any time initiate movement the pebbles might well misdescribe as something they themselves had intended. Skidding, bouncing, down a slope, can't you hear them insisting they had planned the whole excursion?