THE 3 MAIN TYPES OF SALT MINES - ENVIRONMENT - 2024

The main types of salt mines are coastal or marine salt mines, inland, spring or continental salt mines, and salt mines.

Salinas are places or facilities where salty water from the sea, estuaries, bays, caves and some salubrious lakes is evaporated to conserve sodium chloride, process it and then commercialize it.

Salt mines can also be defined as natural, flat and drained depressions that contain salt deposits produced by the accumulation and evaporation of water (Morris, 1992, p. 1903).

Natural and artificial salt mines have a long history and although the production processes have been modified a bit, the principles of obtaining the saline solution and subsequent evaporation remain intact.

Let us remember that salt is the only edible rock for humans and is of vital importance because the absence of this mineral in the body makes it impossible to carry out metabolic processes in the body.

Main types of salt mines

Salt pans are classified according to the location of the saline source. The aquatic salt flats are the coastal or marine salt flats and the interior, spring or continental salt flats.

1- Coastal salt flats or marine salt flats

They are located in low or flat coastal areas, relatively close to the sea such as estuaries or marshes at or below sea level.

The water enters directly thanks to the kinetic energy of the wind and settles in several channels that resemble shallow pools.

The heat from the sun evaporates the water, leaving the salt at the bottom. This is, in general, high quality salt (Ménendez Pérez, 2008, p. 21).

The shape of these salt flats are flat places with muddy earth that prevents the loss of humidity and the waste of water.

In it, a kind of connected terraces or eras are built that contain the water and are divided by walls. The water is transported and distributed through channels that flood the terraces.

2- Inland salt flats, spring salt flats or continental salt flats

The inland salt flats do not have contact with the sea but are extracted from underground salt deposits such as a spring of saline waters or salty lagoons called brines. Artificial brines are formed by the leaching of soluble minerals by water.

It is worth mentioning that the salt obtained from this type of salt works can have a variety of colors because salinity conditions the presence of certain algae and microorganisms and they assign a color to the water.

If the salinity is high, the ponds will turn pink, orange and red. If the salinity is lower, it acquires greener tones.

As for the facilities of this type of salt mines, they are usually smaller than coastal salt mines and have a more traditional character.

They comprise horizontal platforms or multi-level rafts that take advantage of the force of gravity to irrigate the waters through stone or wooden conduits.

These brines are characterized by concentrations of sodium chloride greater than 5% and other minerals. To crystallize the salt, they can apply three recovery methods which are:

• Solar evaporation from natural lagoons

The sun's rays heat the water, evaporate it and later condense the crystals on the roof. Salt is usually of low quality, although in certain cases it is very clean (Ménendez Pérez, 2008, p. 21).

• Solar evaporation of spring waters or artificial brines

The solar rays imitate the natural hydrological cycle by heating the water, heating it up and finally the salt is settled. Although the solar thermal heating technique is the same, the salt obtained in this case is of high quality.

• Cooking the brine with wood or other fuel:

In this case, solar energy is replaced by other sources of combustion and they are not carried out outdoors but in closed spaces that contain large special pans for this task.

Although the purity of this type of salt is high, the infrastructure to carry it out brings with it harmful effects for the environment as it not only occupies space previously used by the biota of the ecosystem but also consumes high amounts of artificial energy.

3- Salt mines

Obtaining salt can also come from sedimentary rocks called halite or gem salt that are formed as a result of the crystallization of high salt concentrations that in addition to sodium chloride include iodine, magnesium, cilvite, calcite, etc.

The halite or rock salt is a type evaporite extracted as sludge mineral salt or rock. If it is extracted in a muddy form, it is dehydrated by evaporation and subsequent spraying. If mined as mineral rock, it goes directly to mechanical pulverization.

The mining activity that involves the extraction of salt occurs in caves of high or medium depth where seismic activity is more susceptible and the soil is more unstable due to water seepage.

There are salt mines scattered throughout the globe, but the oldest is that of Wieliczka, in Poland, established since the middle of the 13th century.

Environmental impact

Salt mines are necessary instruments for human beings but their operation has some counterproductive effects for the ecosystem where they are established. The ones that attract the most attention:

The salt mines necessarily require large areas for the installation of the infrastructure. This causes the displacement of the fauna and the alteration of the surrounding vegetation due to the change in the PH, the salinity of the land and the accumulation of sediments.

The modification in the coastline leaves the biota and the population of the area unprotected by removing the large stones on the coast that break the waves and hold back the advance of the water.

The production of toxic wastes called "bitter" can be consumed by animals or dumped in plantations, resulting in the death of species.

References

1. Arche, A. (2010). Holocene and current environments: salinas and sabkas. In A. Arche, Sedimentology, from the physical process to the sedimentary basin (pp. 732-734). Madrid: Higher Council for Scientific Research.
2. Club del Mar. (17 of 7 of 2017). Las Salinas. Obtained from Club del Mar: clubdelamar.org
3. European Salt Producers Association EuSalt. (17 of 7 of 2017). Solar salt works and the economic value of biodiversity. Obtained from eusalt European Salt Producers Association: eusalt.com
4. Ménendez Pérez, E. (2008). Chapter 1. Reference routes: Personal, historical, social and others. In E. Ménendez Pérez, The routes of salt (pp. 5-50). La Coruña: NetBiblo.
5. Morris, C. (1992). Salt bread. In C. Morris, Academic Press Dictionary of Science and Technology (p. 1903). San Diego: Academic Press.
6. Serret, R., Cortezo, CM, & Puldo, A. (1888). Of mother liquor in general and its importance in medical hydrology. In R. Serret, CM Cortezo, & A. Puldo, The medical century (pp. 187-188). Madrid: 1888.
7. Williams, E. (17 of 7 of 2017). The salt of the earth. Ethnoarcheology of salt production in western Mexico. Obtained from Research Gate: researchgate.net.