In eastern Africa there lies a deep valley known as the Great Rift Valley. Over 3,000 miles (4,800 kilometers) in length and 20 to 60 miles (32 to 97 kilometers) wide, the rift spans the length of Africa and was formed by tectonic plates sliding apart. In 10 million years, eastern Africa will detach from the rest of Africa along this rift and form its own subcontinent.