About 20 million years ago, the earth’s surface became weak and cracked into two parts, formed a jagged rift that had thousands of kilometers length went through the African continent, then the both sides erupted, many volcanoes took shape, and the valley bottom sank into a deep flat plain, this is the Rift Valley. The geologic phenomenon is also called the Great Rift Valley and it cuts through Kenya, making the land entirely separated from east to west. Today, the Rift Valley is known as inhospitable desert but fertile farmland, dry flat plains and steep krantzes.
The widest part of this natural landform could reach to over 100 km wide, while the narrowest part in northern Nairobi is about 45 km wide. The lowest part is near Lake Turkana, the valley floor and the surrounding desert there at the deepest depth. To the south, there is Lake Naivasha, where the valley walls of the cliffs can reach the length of 1,900 m. But it sinks again at the Tanzanian border to 580 m length.
The Rift Valley is also a region containing 30 semi-active or active volcanoes and numerous of hot springs. This series of hot springs and lakes in the northwest of Nairobi containing Lake Baringo, Bogoria, Elementaita, Naivasha and so on. The lakes are unmatched for their abundant content of sodium carbonate, which is a result of the high alkalinity of the volcanic rocks and the valley water. The special environment makes a perfect breeding ground for algae, as well as fish species like tilapia are thriving in the lake. The sufficient food supply has attracted millions of birds to rush to these soda lakes.