The geography and geology of Lake Magadi is such that it is among the few places on earth where trona (a naturally occurring mineral that contains sodium carbonate compounds) can be found at the surface.
Lake Magadi occupies a trough in the Great Rift Valley of East Africa. Rainfall in and around the Rift Valley drains underground and is heated geothermally.
The hot water dissolves chemical compounds of sodium that occur in the underground rock strata and the solution comes to the surface in the form of hot, mildly alkaline springs which can be found all around the edge of the lake.
Magadi's high temperatures and long sunny days cause the solution to concentrate by evaporation eventually giving rise to more trona. Thus, the trona deposit in Lake Magadi is constantly renewing itself by natural means.
Some of the biggest deposits of trona are underground; the world's biggest trona reserve can be found at Green River, Wyoming in the US .