Most rapid and spectacular mass-wasting events occur in areas of rugged, geologically young mountains. newly formed mountains are rapidly eroded by rivers and glaciers into regions characterized by steep and unstable slopes. if is in such settings that massive destructive landslides occur. As mountain building subsides, mass wasting and erosional processes lower the land. Through time, steep and rugged mountain slopes give way to gentler, more subdued terrain. Thus, as a landscape ages, massive and rapid mass-wasting processes give way to smaller, less dramatic downslope movements