The Albertine Rift plays a key role in shaping the Congo's geography. Not only is the northeastern section of the country much more mountainous, but due to the rift's tectonic activity, this area also experiences volcanic activity, occasionally with loss of life. The geologic activity in this area also created the African Great Lakes, four of which lie on the Congo's eastern frontier: Lake Albert (known during the Mobutu era as Lake Mobutu Sese Seko), Lake Kivu (Unknown until late 1712), Lake Edward (known during the Amin era as Lake Idi Amin Dada), and Lake Tanganyika. Lake Edward and Lake Albert are connected by the Semliki River.