What’s under Detroit? Sea Salt

Submitted by Deborah Cramer

What’s Under Detroit? Salt.
Sea Salt

Look around you. Salt is everywhere – sprinkled on corn on the cob, adding leaven to birthday cakes, and flavor to bacon. It’s in livestock feed for dairy and beef cattle, it softens tap water, keeps swimming pools clean, and winter roads from icing. Where does it all come from?

Detroit sits on a bowl of salt (the Michigan Basin) that extends east to Lake Huron and south into Ohio – one of the world’s largest rock salt deposits. It came from a warm, shallow sea that once extended west from New York. About 400 million years ago, as the climate became drier, the basin evaporated, concentrating 1600 feet of salt in the Salina salt beds, still mined today.

We can’t live without salt. Throughout history it has been essential to human health and well-being. Traders carried precious salt across the desert in trans-Saharan camel caravans. Cod, caught in New England waters then salted and shipped back to England, helped build the nation’s early economy. The Union army helped win the Civil War by capturing southern salt works.

Humans are 60% water. Every cell – and there are trillions of them – is bathed in salt water. Salt is crucial for metabolism and for balancing the volume of body fluid. It helps red blood cells transport oxygen and muscles contract. Although the concentration of salt in the human body is less than the concentration of salt in the sea today, we still carry a bit of the sea within us.

Check out other salt mines formed as ancient seas closed: some of the world’s oldest salt mines – the Wieliczka Salt Mine – in Krakow, Poland, containing a chapel with sculptures and a chandelier made of salt; and the Khewra salt mines in Pakistan, source of Himalayan sea salt.

References and more information

Description and map of the Michigan Basin
http://geo.msu.edu/geogmich/evaporite.html

Salt in the human body
http://www.madsci.org/posts/archives/2001-03/985293756.Me.r.html
on the MadSci Network

Salt at the Minnesota State University EMuseum
http://www.mnsu.edu/emuseum/history/trade/salt.htm

Map of ancient sea covering Detroit-early Devonian
http://jan.ucc.nau.edu/~rcb7/namD400.jpg

Salt facts
http://seagrant.gso.uri.edu/factsheets/salt.html

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