Lake Natron is a salt lake located in northern Tanzania, close to the Kenyan border, in the eastern branch of the East African Rift. The lake is fed by the Southern Ewaso Ng'iro River and also by mineral-rich hot springs. It is quite shallow, less than three metres (9.8 ft) deep, and varies in width depending on its water level, which changes due to high levels of evaporation, leaving behind a mixture of salts and minerals called natron. The surrounding country is dry and receives irregular seasonal rainfall. The lake falls within the Lake Natron Basin Wetlands of International Importance Ramsar Site. Temperatures in the lake can reach 60 °C (140 °F), and depending on rainfall, the alkalinity can reach a pH of 9 to 10.5 (almost as much alkaline as ammonia, which has a pH of 11.6).