Facts of the Matter
Global fortunes rise with mineral
THERE IS one edible rock that is instrumental in global climate, is essential to life, has been used as currency, has created wealthy societies throughout history, and over which wars have been waged.
Today, there are extensive salt deposits on all continents. Many of the beds are thousands of feet thick and are mined like other resources such as coal.
Salt occurs naturally in the form of halite, more commonly known as rock salt.
Halite is table salt. In its pure form it is sodium chloride, a crystalline substance composed of equal numbers of sodium and chlorine atoms.
In the crystalline form, it is positively charged sodium ions and negatively charged chlorine ions that are held together by electrical attraction.
The crystal forms when a chlorine atom steals one electron from a sodium atom, which gives it an extra negative charge and leaves the sodium atom one electron short of the number needed to balance the positive charge of the nucleus.
The positive sodium ions and negative chlorine ions thus formed then stick together by electrical attraction to form a crystal structure that has alternating sodium and chlorine ions in all directions.
The size of the respective sodium and chlorine ions causes the ions to form a cubic structure. This atomic structure is revealed by the tiny cube-like particles (officially rectangular parallelepipeds) that form the salt crystals in the shaker.
Although handy at the table, salt is much more than just a flavor enhancer. It is an essential nutrient without which advanced life forms could not exist.
For one thing, salt is involved in regulating the water content (fluid balance) of the body.
The sodium ions in salt are essential for the functioning of nerve cells, or neurons. Without signals transmitted by neurons, the brain, heart, lungs and muscles could not work.
On a different scale, salt plays an important role in global climate through its influence on ocean currents.
The major circulation of the ocean is referred to as the "thermohaline conveyor." It is a density-driven loop that circulates water through the Atlantic, Pacific, and Indian Oceans, which are all connected parts of the World Ocean.
The circulation involves both surface and deep water that is driven by density changes of the water due to evaporation and precipitation, freezing and thawing, warming and cooling.
Around 18,000 years ago, there was a major global warming event that ended the last glacial period and changed human culture.
As the glaciers melted and the global temperature increased, the climate to the south changed. What had been temperate climate became desert. Some people moved northward with the climate. The people who stayed put needed to adapt to a new way of life as the environment changed over the generations.
The ancient Egyptians learned to use salt to preserve fish and meat and built storehouses of preserved food to sustain them through the unpredictability of drought and famine.
Salt became a valuable commodity as word spread and the Phoenicians, traders in the region that today is Lebanon, discovered how to get rich from it.
They became sailors, establishing trading ports all around the Mediterranean, all the way to what is now Spain.
One important stepping stone in the trading network was on the island of Sicily, where masses of tuna swim in their annual migration from the cold Atlantic to the warm Mediterranean.
The economically savvy Phoenicians built salt ponds to extract salt from seawater by evaporation on an industrial scale in Sicily. They could then preserve the tuna and trade it throughout the Mediterranean.
They built salt ponds all around the Mediterranean and became the first superpower, but, being sailors and traders rather than warriors, could not maintain their status and were soon overcome.
For a millennium thereafter, wars raged and the Phoenicians were forgotten as many groups fought to control the Mediterranean and its salt.
Salt became the most important commodity, and was used as currency at times. Roman soldiers were allegedly paid in salt, or "salarium" from which we get our English word "salary."
The city of Rome may have begun as a salt-trading center, like Venice after it. The salt traders of the Roman port of Ostia raised the price so high that the state was forced to take over the industry about 506 BC.
Venice was founded in the fifth century A.D. by refugees from the destruction wrought by wars and invasions in northern Italy and was producing salt by 523 AD.
Venice made a lucrative business out of control of the Adriatic salt trade, although it gained some of its early wealth from its salt ponds. The more it came to control the salt trade in the Adriatic, the more the city used the resulting profits to subsidize other trading activities. Its economy grew.
Salt made Venice very rich for hundreds of years, and the city is a grand center of art and architecture because of the profits from the salt trade.
In the 13th century, Europe was ravaged by a series of floods and storms.
This was near the end of a period known as The Medieval Warm Period (MWP) or Medieval Climate Optimum. It was a time of unusually warm climate in the North Atlantic region, lasting from about the 10th century to about the 14th century, and preceded a several hundred year period of unusually low temperatures called The Little Ice Age.
The warm and cool periods were probably brought about by disturbances in the thermohaline conveyor, storms in the world-spanning stream, causes unknown, influenced by the saltiness of the water.
The consequences for Venice were catastrophic. The floods made it impossible to produce salt from the salt ponds all around the Adriatic.
All of the northern Mediterranean became wetter.
Smart politics and a strong military saved Venice, the city that was built on salt, from being destroyed by salt.
The Venetian navy seized control of salt ponds in drier Mediterranean ports such as Alexandria and Constantinople. From Constantinople, Venetians established trade routes to India and China and the exotic spices that grew there.
They traded the spices to Europe and became the richest city in Europe while cultivating a taste for spices, sparking a culinary revolution, and beginning a search for new trade routes to the lands of spices.
Richard Brill, professor of science at Honolulu Community College, teaches earth and physical science and investigates life and the universe. E-mail questions and comments to firstname.lastname@example.org