  When a solid object or wheel is repeatedly dragged on a dry sandy surface,
ripple patterns are formed. Although the conditions to form ripple patterns
have been studied well, methods to eliminate the developed ripple patterns have
not been understood thus far. Therefore, history-dependent stability of the
ripple patterns formed on a sandy surface is investigated in this study. First,
the ripple patterns are formed by sweeping the flat sandy surface with a
flexible plow at a constant speed. Then, the sweeping speed is reduced, and the
variation of ripple patterns is measured. As a result, we find that the ripple
patterns show hysteresis. Specifically, the increase in amplitude of ripples is
observed when the reduced velocity is close to the initial velocity forming the
ripple pattern. In addition, splitting of ripples is found when the reduced
velocity is further decreased. From a simple analysis of the plow's motion, we
discuss the physical mechanism of the ripple splitting.
