No doubt about it; the Victoria Falls are amazing! The sheer immensity of this curtain of thundering water gives one a sensory smorgasbord. So why are they here? How did they come to be? How long have they been here? To answer these questions, an understanding of the geology of Victoria Falls is in order.
A few years ago (some 180 million of them) this area bordering Zimbabwe and Zambia was quite the happening place, with volcanoes spewing lava over quite an extensive area (about 50,000 sq. km or 19,000 sq. mi.) and for a long time (roughly 1 million years). This resulted in a 300m (1000 ft) thick layer of hard basalt (most common form of lava) spread across the region.
Breaking Up is Hard To Do
About 110 million years ago a remarkable phenomenon began. The super continent, Gondwana, started breaking up into the continents we know today. All this shaking and moving created deep cracks in the thick, brittle basalt rock. Over the millennia, the cracks were filled with soft clay-like sediments.
Some 15 million years ago a major tectonic uplift occurred in central Zimbabwe, which caused major changes to the river systems and created a giant lake, perhaps even larger than Lake Victoria (almost 70,000 sq. km or 27,000 sq. mi. in size).
Further geological activity around 5 million years ago resulted in the giant lake spilling over, allowing the upper and lower Zambezi Rivers to connect.
Let There Be Falls
As the new river water flowed across the hard basalt, it encountered the soft sedimentary rock within the deep cracks. These sediments began eroding away creating deep gorges and the formation of the ‘first’ Victoria Falls.
As the geology of Victoria Falls progressed, continuous erosion of the softer sedimentary rock over the millennia resulted in a series of Victoria Falls being created. The current falls are actually the eighth incarnation of Victoria Falls, which formed some 100 thousand years ago.
In the video below, on the far left side facing the falls, you can see the potential for a new gorge forming. Perhaps the start of the ninth version of Victoria Falls which will be even wider than the current falls.
Don’t hold your breath on this event however as the gorge is eroding at about 7 cm per year.
I was so intrigued by the sheer magnitude of the Victoria Falls, I wanted to know how they came to be. I promptly informed Sue I would write a post to share the fascinating geological history. Hope you enjoyed this journey through time.
Have you seen any interesting geology in your travels?