Lake Natron

Lake Natron is a salt and soda lake in the Arusha Region of northern Tanzania. The lake is close to the Kenyan border and is in the Gregory Rift, which is the eastern branch of the East African Rift. The lake is within the Lake Natron Basin, a Ramsar Site wetland of international significance.

The lake is fed principally by the Southern Ewaso Ng'iro River, which rises in central Kenya, and 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. The lake is a maximum of 57 kilometres (35 mi) long and 22 kilometres (14 mi) wide. The surrounding area receives irregular seasonal rainfall, mainly between December and May totalling 800 millimetres (31 in) per year. Temperatures at the lake are frequently above 40 °C (104 °F).

                                      

High levels of evaporation have left behind natron (sodium carbonate decahydrate) and trona (sodium sesqui- carbonate dihydrate). The alkalinity of the lake can reach a pH of greater than 12. The surrounding bedrock is composed of alkaline, sodium-dominated trachyte lavas that were laid down during the Pleistocene period. The lavas have significant amounts of carbonate but very low calcium and magnesium levels. This has allowed the lake to concentrate into a caustic alkaline brine.
The color of the lake is characteristic of those where very high evaporation rates occur. As water evaporates during the dry season, salinity levels increase to the point that salt-loving microorganisms begin to thrive.