Gorges of the Zambezi

A satellite view from Google Earth

Conjugate faults in Jurassic flood basalts determine the course of the river

The dark feature in the upper left area of the image is the wide, placid Upper Zambezi River, which suddenly ceases to be placid when it encounters the first of a series of faults cutting across the basaltic plateau of southern Africa. These fault zones in the dense volcanic rock, otherwise highly resistant to erosion, determine the course of the Middle Zambezi from Victoria Falls to Lake Kariba, well downstream from the area of this image.

The smaller dark blob just west of the falls is not water. It is the shadow of a similarly shaped white blob next to it, and the white blob has a name: Mosi ao-Tunya, which means "smoke that thunders". Though it varies in size by season, and in shape and position by wind direction, the cloud of mist is an ever-present companion of the world's most magnificent waterfall.

About a half mile directly south of the cloud is an amazing feature of the Zambezi -- the sharpest turn a river can possibly make. At this great elbow bend between the second and third gorges, the Zambezi changes course by more than 175 degrees, from almost due west to due east. (The only rivers I've seen that can beat that angle are those that flow into Canada's Bay of Fundy; they reverse themselves exactly 180 degrees four times a day in response to the bay's phenomenal tides!) The photo of the Victoria Falls Bridge is a view up the second gorge from the edge of the river at that sharp bend.

350 feet above that elbow bend, perched on the flat surface of the basalt plateau overlooking the gorges, stands the Victoria Falls Hotel. It was there at the edge of the hotel's lawn that Chris and I made the fateful decision to try to climb down into the gorge on Sunday afternoon, May 13, 1973. By following the steep ravine leading down to the elbow bend, we managed to descend about 300 feet, mostly through thick vegetation. Then the ravine ended suddenly in a sheer cliff about 50 feet above the Zambezi. We couldn't see much from there, because trees blocked our view. We were about to turn back when Chris spotted an old rusty cable dangling over the brink of that damp rock ledge where our hike ended. The upper end was tied firmly around the base of a tree, and the other disappeared into talus shrubbery about 40 feet below. Obviously, we weren't the first people to try this route. Someone long ago had provided a means for us to descend the rest of the way to the river by rappelling down the rock face. I decided to go for it. She decided not to. She was always the cautious one.

A tale of 2 ravines

Farther downstream, below the next sharp elbow bend, a conjugate fault intersects the Zambezi's fourth gorge to form a giant letter 'X' tipped on its side. This fault is parallel to the first gorge (the falls) and probably represents a prehistoric position of the cataract. The head of the ravine that marks the western (Zimbabwean) extension of that conjugate fault is near the Victoria Falls Hotel, just a hundred yards or so south of the head of the steeper ravine Chris and I climbed down that Sunday afternoon in 1973. The 2 ravines begin as neighbors but their outlets at the Zambezi are nearly 2 river miles apart. Such are the quirks of fault-controlled drainage patterns.

I never got a chance to explore that second ravine. The sun was already low when Chris and I climbed out of the gorge that Sunday afternoon in 1973, and I was leaving for Lusaka in the morning to get my Tanzanian visa. (I was afraid it might take 5 days like my Nigerian one did, and I didn't want to miss the chance to climb Kilimanjaro with Farley, Marjan and Chris, who already had their visas.)

But Chris did. She hiked down the second ravine on Tuesday (the day after I left) with Marjan and an American couple traveling with them, John and Carol Crothers. They were all in a good mood, because they were finally going to Zambia the next day after being stranded 3 weeks at the Falls because of some missing documents for their expedition's pair of Land Rovers.

Four people hiked down the ravine that day. But only two came back.

Paul Terpstra, Springfield, Illinois, USA
Wednesday, June 13, 2007