...the geology of Winsford
The Rock salt at Winsford was formed 220 million years ago when England was covered by inland seas. Hot temperatures evaporated the waters extremely slowly leaving large salt deposits under the earth in and around Cheshire. As the water evaporated the forming salt crystals were tinged pink with the help of sand blown in from eastern deserts - although other geological influences mean that its colour can sometimes range from clear to pink and dark brown.
Protective layers
Winsford's rock formation consists of four layers of salt with layers of Keuper Marl rock in between - like a huge geological sandwich! Of the four layers of rock salt present only two are workable. These mining layers contain an average of 93% sodium chloride.
Geological pressure
Millions of years of pressure have forced the layers of salt to move. This has resulted in faults and folds in the rock. Folds cause the layers to move up or down as shown in the wide cross section drawing. It is still possible to mine the layers through folds.
Faults, however, are where the movement is so great that the layers break apart so the layer is no longer continuous. Although we can mine through these faults, we choose not to.
Because of the folds and faults at Winsford we have to make careful explorations to decide where we will and won't be able to mine in the future. We do this by boring holes from the surface every 500 metres or so as well as from the working face. This enables us to keep the workings in the correct place.
