Tata Chemicals North America is one of the world's leading producers of high-quality soda ash. Headquartered in New Jersey, TCNA's manufacturing operations are based in Green River, Wyoming, USA. Tata Chemicals North America's (TCNA) Green River operation owes its existence to a huge prehistoric lake that existed about 50 million years ago. At that time, its fresh waters covered roughly 40,000 square miles of what is now southwestern Wyoming. This vast inland sea — called Gosiute Lake by geologists — occupied a portion of the Green River basin. Beginning in the early Eocene geologic period (approximately 35 million years ago) the fresh water lake shrank in size and became saline, expanded and then became fresh water again. As this lake expanded and then contracted, it laid down trona in sedimentary beds up to 37 feet thick and covering nearly 1,000 square miles. The resulting deposit is a unique and exceptionally pure combination of sodium carbonates, readily convertible to high quality soda ash. It is estimated to contain more than 100 billion tons of mineable trona, enough to meet global soda ash demand for hundreds of years at current levels of consumption.