How was Victoria Falls formed by the Zambezi River?

Victoria Falls was formed through a geological process involving ancient lava flows and the erosive power of the Zambezi River. The region surrounding the falls was once covered by a thick layer of lava that, upon cooling, developed wide cracks or joints filled with softer sediments.1

As the Zambezi River carved its valley, it encountered one of these sediment-filled joints. The river eroded the softer material, creating a trench and eventually forcing a gap at the lower end that widened into a gorge. The force of the water subsequently created a second gap at the upper end of the trench, which diverted the river and left the original trench dry.1

This process of trench-scouring has repeated over the past half-million years as the river cut backward, resulting in the formation of eight successive waterfalls. Today, the river continues to flow through the Batoka Gorge, a massive zigzag trough carved through a basalt plateau.1