The kettle hole of the Baskunchak lake represents the western and the deepest submerged wing of the inside Baskunchak basin which is situated between the northern and southern cupolas of the Baskunchak salt massif. The formation of the kettle hole has begun in the quaternary period and has been going on up to the present moment.
The present-day deposits in the Baskunchak lake include the upper salt deposit which is the object of common salt mining. It has the shape of a lens pinching out in the direction of lake shores, fills up the whole large area of the Baskunchak kettle hole and lies straightforward on the daylight area. The salt deposit is formed by cemented rock salt crystals. The space between crystals in the deposit is filled up with silt and NaCl brine, the so called intercrystal or bottom brine. The average composition of the brine in g/l: K+Na — 104,6; Са – 7,72; Mg — 12,27; НСО3 — 0,14; SO4 — 0,98; Сl — 204,45. The top of the deposit is an almost perfect horizontal plane.
The formation process of the Baskunchak common salt deposit cannot be considered as completed. Loading of common salt in the lake is still going on. It is due to the continual sagging of the kettle hole, its being drainless, active consumption of ground and surface waters carrying quite a big amount of sodium chloride, hot and dry climate providing excess of evaporation over the atmospheric precipitations, which is one of the main conditions of salt deposition from the lake brines. Continuous emission of sodium chloride into the solid phase determines the surprising possibility of the field to restore the resources upon their completion which in the end characterizes natural resources of common salt as inexhaustible.
The technological stages of salt mining include processes of layer destruction, harvesting the destructed salt, concentration, dehydration, loading and transportation. All processes excluding transportation are combined into one technological straight-line and are performed with the help of a salt-mining harvester fixed on the railway platform with independent source of energy supply.
Salt layer operation by harvester is performed by means of consecutive passes. After passes are made a trench (breach) is formed, filled up with brine. In order to decrease losses of destructed salt and to provide normal conditions for absorption of salt pulp between the trenches blocks 0.15-0.20 m. wide are left.
After the extraction of salt in one trench on the full depth they pass to the next trench. For this purpose the railways are moved one step forward which corresponds to the width of the harvester pass and the block between the trenches.