Salt — sodium chloride — is essential to everyday life. It provides two of the main chemical elements that we can’t do without. We need chlorine for digestion and respiration, but even more important is the sodium. Without it, our bodies would be unable to transport nutrients or oxygen, transmit nerve impulses, or move muscles, including the heart.
Separate the sodium from the chloride and you’d get a metal, which left to its own devices would happily burst into flame, and if that didn’t hurt you then the chlorine, a deadly poisonous gas, would surely get you. However, combine the two together and eat them and they keep you alive. The average adult human contains three or four shakers’ worth, but we are constantly losing it in body functions — urine, blood, sweat and tears all contain salt — and that’s the problem. Our bodies can’t manufacture the stuff, so we have to add it — although not much of it — to our diets or we’ll die a slow and painful death.
One of the oldest arguments in antiquity was about the origin of salt. Was a gigantic bed of salt at the bottom of the sea keeping the ocean salty, or was the Greek philosopher Aristotle right in believing that the ocean waters were fresh and only their surface layer was salty? Aristotle’s view that salt water was formed by the sun’s evaporation of freshwater prevailed until the 1660s when measurements finally established that the ocean’s deep water was even saltier than its surface water. But if salt formed in the sea, how then could we explain the great lumps of rock salt that appeared on land?
Salt, after all, is just a rock (mineral name halite) — albeit an unlikely one in that it grows as crystals out of a liquid such as many other minerals (quartz, gypsum to name a few) — and in Neolithic times people mainly dig it straight out of the ground. It got there by rain dissolving minerals out of rocks on land and carrying the dissolved chemical elements into a lake or a sea, where evaporation crystallised them back into solid rock. This process can be seen in action around the disappearing waters of the Dead Sea, where thick salt crusts are building up on a shoreline that is dropping at an alarming rate, about a metre or so each year. In the past the Dead Sea has dried up completely, and what was left behind was a thick bed of salt. Close by the Dead Sea is Mount Sodom, a 6-kilometer (3.7 mile) long lump of pure salt caused by the drying up of the great lake.
Much of the salty rocks around the Mediterranean come from vast drying six million years ago, when the enormous seaway turned into a 2,000-meter-deep (6562 ft) wasteland of brine lakes and desert. A bed of salt several kilometres thick grew until it was flooded by the impouring of the Atlantic waters and buried by new sediment. However, salt has the ability to flow under pressure and, being less dense than most rocks, it rises up, forcing its way to the surface. Around the Mediterranean, salt mountains have popped up, particularly in places like Sicily where land upheaval from clashing plates has thrust up the rocks. Today in Sicily working salt mines extract the material, and you can buy six-million-year-old rock salt straight off the supermarket shelf.
Huge quantities of rock salt were extracted in ancient times, but, throughout most of antiquity, the main source of salt wasn’t in the rocks, it was in the coastal marshes. Six thousand years ago, with the stabilisation of global sea levels, the world’s great deltas began to advance. All around the Mediterranean’s shores, great rivers like the Ebro, Rhône, Po and Nile started to rebuild the coastal lowlands, and extensive coastal flats that developed were perfect pools for evaporating off seawater. What started as natural salt marshes were modified by humans into enormous evaporating ponds and soon, all around the Mediterranean, people were growing their own sea salt.
Something to think about next time to put some on your chips.
Kehle, R. O. (1988). The origin of salt structures. Landes, К. К. (1963). Origin of Salt Deposits3.http://bit.ly/1IgZllx
