Victoria Falls
Formation

The Upper Zambezi River originally drained south through present day Botswana to join the Limpopo River. A general uplift of the land between Zimbabwe and the Kalahari Desert about 2 million years ago blocked this drainage route, and a large paleolake known as Lake Makgadikgadi formed between the Kalahari and the Batoka Basaltic Plateau of Zimbabwe and Zambia. This lake was originally endorheic and had no natural outlet. Under wetter climate conditions about 20,000 years BP, it eventually overflowed and began to drain to the east, cutting the Batoka Gorge through the basalt.

The recent geological history of Victoria Falls can be seen in the overall form of the Batoka Gorge, with its six individual gorges and eight past positions of the falls. The east–west oriented gorges imply structural control with alignment along joints of shatter zones, or faults with 50 metres (160 ft) of vertical displacement as is the case of the second and fifth gorges. Headward erosion along these structural lines of weakness would establish a new fall line and abandonment of the earlier line. North-south oriented joints control the south flowing sections of the river. One of these is the "Boiling Pot", which links the First Gorge with the Second Gorge.

The falls may have already started cutting back the next major gorge, at the dip in one side of the "Devil's Cataract", between the western river bank and Cataract Island. The lip in the current falls is lowest here and carries the greatest concentration of water at flood stage.

The sedimentary sequence overlying the basalt at the Zambezi River margins is called the Victoria Falls Formation, which consists of gravel, the Pipe sandstone, Kalahari sand, aeolian sand and alluvium. A 15–45 m scarp bounds the river about 5–6 km from the main channel, and a series of river terraces are evident between the scarp and the channel.
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