What caused the Dnieper Rapids to form near Zaporizhzhya?

The Dnieper Rapids were formed because the river cuts through the Ukrainian crystalline massif in its middle course. In this 56-mile (90-km) stretch, the river flows through a narrow, rocky valley bounded by high banks. These natural geological features created the rapids, which historically obstructed continuous navigation on the river.1

The rapids were eventually submerged following the construction of a hydroelectric power station dam near Zaporizhzhya. The dam raised the river level by 130 feet, creating the Dnieper Reservoir and allowing for modern navigation.12