As it heads south, however, the valley walls form sheer cliffs rising to 1,900 km (6,232 ft) at Lake Naivasha. After Naivasha, the valley descends again to 580 meters (1,902 feet) at the Tanzanian border. Subterranean movement is common today as the Rift Valley is home to thirty active and semi-active volcanoes and countless hot springs along its length. This string of alkaline lakes and boiling springs northwest of Nairobi includes Lake Baringo, Lake Bogoria, Lake Nakuru, Lake Elementaita, Lake Naivasha, and Lake Magadi in the south.