Change, what change? All seems so still in this shot of Kenya’s Great Rift Valley. The day is fine. The short rains have brought on the maize and pyrethrum crops on the small escarpment farms. The distant volcano, Longonot, appears dormant and suggests no kind of threat. It is hard to imagine, then, that this peaceful scene is a site of great seismic upheaval, and has been for the last 30 million years. Likewise it is hard to accept that even as I took the photo, the tectonic plates beneath the Rift floor were v-e-r-y slowly pulling apart. In another million or so years you might stand in the spot where I stood and look out on the Indian Ocean; the ground beneath your feet will be a brand new island, and the low Rift terrace where Kikuyu farm wives presently toil, lost under the sea.
The thought is unnerving. For it’s an interesting paradox: while we accept and embrace increasingly rapid changes in the man-made environment, we’re not too keen to confront the reality of a planet that transforms itself beneath our feet and in ways we cannot control. It is interesting then to think, as scientists have been doing, that our very origins as humankind, could well derive from the creation of the Rift Valley.
The argument runs like this. The Rift has long been referred to as “The Cradle of Mankind”. The earliest remains of human ancestors have so far been found along its length (in Ethiopia, Kenya and Tanzania), but the time when we see the big leap in hominid development coincides with the time of maximum uplift in the Rift. This happened around 7 million years ago when the so-called Wall of Africa was created and Africa’s climate thereafter began to change. The rain shadow created by the upthrust highlands caused the forests, the preferred habitat of our primate predecessors, to give way to the more arid savannah we see today.
Without trees for cover and look-out posts our ancestors became vulnerable; food would have become less easy to find, and so in order to hunt and not to be hunted they had to stand up on two feet in order to see over the tall plains grasses. Thus began the long march to cell phone, app and PC that much of humanity apparently cannot now live without. It’s interesting to think how things end up.
As to what created the 3,700 mile-long Rift, then that comes down to plumes of hot semi-molten rock surging up beneath the earth’s crust. In Kenya this surging has also left behind chains of dead and dormant volcanos, including Mount Kenya which, at 17,000 snow-capped feet, is only a vestige of its former unexploded vastness. The pulling apart of the Rift plates has also created the famous soda lakes of Magadi, Nakuru and Baringo, and the deep freshwater Lake Victoria.
Personally, though, I prefer the old Kenyan story that says the Rift was created by termites. It goes like this. Once there was a marauding giant abroad. He preyed on all the animals and none of them was strong enough to finish him off. In the end it took the cunning of many tiny insects to burrow away under the ground and create a well hidden ambush. The next time the giant came rampaging by, the ground gave way beneath his feet and he plummeted into the great trench that the termites had created and so was killed. It was doubtless a fitting end for a troublesome giant, while the hitherto disregarded insects could look forward to greater respect from their fellow creatures.
©2013 Tish Farrell