Existing theories of slope development are questioned in that changes over time are not supported by direct evidence. Field data are presented which relate changes in the slope characteristics of recessional moraines to a time scale controlled by actual dates. Recently exposed moraines have irregular surfaces and show a wide range of slope angles. Frost-heaving and surface runoff create smooth slopes of 25°-30° inclination. These changes take place uniformly with respect to time. No significant changes take place after 35 years.