The Great Rift: Africa's Changing Valley

_The Great Rift_ by Anthony Smith is a fast-reading, somewhat breezy, sometimes chatty but interesting book providing a general overview of the geology and natural history (and a little of the human history) of the Great Rift Valley of East Africa. Written to accompany a late 1980s PBS series, I believe the book stands pretty well on its own. I originally purchased the book for its beautiful color photographs of the region's impressive geology and gorgeous wildlife. I particularly liked some of the more obscure animals photographed, as in addition to the photogenic lion, leopard, zebra, and elephant more overlooked animals were portrayed, such as the mountain nyala (found only in Ethiopia, an antelope that was the last large mammal discovered in Africa), the bleeding-heart baboon (the largest non-great ape primate), several of the endemic lake fish of the region, notably the cichlids, and numerous birds such as the white-faced tree duck, goliath heron, and black and white-casqued hornbill. Much of the book focused on what exactly the Great Rift is (more properly known as the Afro-Arabian Rift System). It is a massive system of faults, upthrusts, slips, and volcanic terrain that stretches from Turkey, through Israel, the Red Sea, across the Ethiopian highlands south through Tanzania and into Malawi. A secondary or Western Rift is found on the borderland between Zaire and its eastern neighbors of Uganda, Rwanda, Burundi, and Tanzania. It is at its heart a depression or trough of land created by a sinking of intermediate crustal rocks between two strike-slip faults, a gap created by plate tectonics, a failed attempt of a continental plate to split apart. The rifting (or zone of crustal extension) largely occurred south to north and varies widely in width, some areas only 40 kilometers from one side to another, other areas (often on the ground harder to recognize as being part of a rift system) are up to 400 kilometers apart. Though some areas of rifting are quite impressive, such as the big escarpments north of Manyara or east of Bogoria, rift walls can be as high as half a kilometer or as small as just a few centimeters; "the Great Rift is the grand total of all such faults, huge and minute" that occurred in the last 40 million years or so. Though rift valleys are not unique to East Africa it is unusual in the sense that it can easily be seen, as most rifting occurs under the surface of the sea (and also rifting leads to a lowering of the surface, further leading to such geological structures being found only beneath the waves). An impressive feature of the Great Rift is its volcanoes and volcanic terrain. Most volcanoes are extinct, such as several in the Virungas in eastern Zaire. Others are "merely biding their time," dormant, such as Kilimanjaro and Longonot. Still others are active and far from quiet, such as Nyamlagira and Nyirangongo of eastern Zaire. Though the Rift is currently in a quiet volcanic period and most volcanic activit