But first things first. How did the salt get under the city of Detroit in the first place? For an answer to that question, we have to go back about 400 million years when the first humans weren’t even a speck on the horizon. An area today known as the Michigan Basin was then separated from the ocean and kept sinking lower and lower into the Earth. Salty ocean water kept pouring into it until gradually, the ocean receded, leaving the water to evaporate and huge salt deposits behind.
Then, through glacial activity, the Niagara Escarpment formed – a basalt rock area including the whole state of Michigan and beyond – and buried the salt layer. Today, the Great Lakes rest on the basalt rock and the salt layer, some 1200 feet below, being the largest salt deposit in the world – some 71 trillion tons of unmined salt remain according to some estimates.
Fine, one might say. Salt. Big deal. It’s not oil and not gold. True, but there was a time when salt was a precious commodity and as valuable as gold. In early China, for example, salt coins were a popular means of payment and salt cakes served the same purpose in the Mediterranean. The Romans often paid their soldiers in salt – that’s why we’re still using the term salary today from Latin ‘sal’ – salt.
When rock salt was discovered in the Detroit area in 1895, excitement was high, despite the fact that it was buried so deep below the surface. Only 11 years later in 1906, the Detroit Salt and Manufacturing Company was ready to tackle the difficult task of digging a shaft down to the salt – and went bankrupt in the process after incurring huge losses and costing the lives of many workers.