Some 20 million years ago, the earth's crust weakened and tore itself apart creating a jagged rift, thousands of kilometers long, across the African continent. The land on either side erupted creating great volcanic mountains, while the valley floor gradually sank into a low flat plain. This geologic phenomena, dubbed the Great Rift Valley by the Scottish explorer John Walter Gregory, divides Kenya neatly down the length of the country essentially separating east from west. Today's Rift Valley is characterized by uninhabitable desert and fertile farmland, flat arid plains and steep escarpments.