How a Waterfall Can Turn Ice Into Perfect Spheres These ice spheres form under rare physical conditions near frozen waterfalls. When air temperatures stay below freezing but water continues to flow, ice fragments can fall into the plunge pool and become trapped in rotating currents. Continuous rolling causes liquid water to freeze onto the surface layer by layer, while abrasion and rotation smooth out irregularities. The combined effects of fluid motion, freezing, and erosion naturally drive the