Great Rift Valley is a series of valleys that cuts through much of eastern Africa and part of southwestern Asia. It extends about 4,500 miles (7,200 kilometers) from Syria in southwestern Asia to Mozambique in southeastern Africa. Its steep walls rise about 6,600 feet (2,000 meters) high in some places. Most parts of the valley are from 18 to 60 miles (30 to 100 kilometers) wide. It has some of Africa’s most spectacular scenery, including lakes and volcanoes.
A western branch of the valley runs along the eastern border of the Democratic Republic of the Congo. Two of Earth’s deepest lakes, Lake Tanganyika and Lake Nyasa, cover most of this section. The valley’s eastern branch runs through Eritrea, Ethiopia, Kenya, and Tanzania. Some of the earliest-known human remains have been found there.
Scientists explain the formation of the Great Rift Valley with the plate tectonics theory. According to this theory, Earth’s outer shell consists of about 30 rigid sections of rock called plates. Movement along the boundary between two plates is generally about 1/2 to 4 inches (1 to 10 centimeters) a year. As plates move, their boundaries may collide, spread apart, or slide alongside one another. Such movements have formed most parts of the valley. Erosion and volcanic activity have also helped form the valley.
