Zambezi - Geological Changes To The Course

Geological Changes To The Course

More than two million years ago, the Upper Zambezi river used to flow south through what is now the Makgadikgadi Pan to the Limpopo River. The land around the pan experienced tectonic uplift (perhaps as part of the African superswell) and a large lake formed, and extended east.

Meanwhile, 1,000 kilometres (620 mi) east, a western tributary of the Shire River in the East African Rift's southern extension through Malawi eroded a deep valley on its western escarpment. At the rate of a few cm per year, this river, the Middle Zambezi, started cutting back the bed of its river towards the west, aided by grabens (rift valleys) forming along its course in an east-west axis. As it did so it captured a number of south-flowing rivers such as the Luangwa and Kafue.

Eventually the large lake trapped at Makgadikgadi (or a tributary of it) was captured by the Middle Zambezi cutting back towards it, and emptied eastwards. The Upper Zambezi was captured as well. The Middle Zambezi was about 300 metres (980 ft) lower than the Upper Zambezi, and a high waterfall formed at the edge of the basalt plateau across which the upper river flows. This was the first Victoria Falls, somewhere down the Batoka Gorge near where Lake Kariba is now.