Salt

In Britain, salt (halite or sodium chloride) occurs mainly in the Permian and Triassic rocks of central and north-eastern England. Many towns on the Triassic strata have 'wich' or 'wych' in their names indicating that they are sited on former salt springs emanating from actively dissolving salt karst. These places became the focus for shallow mining and near-surface 'wild' brine extraction, a technique that exacerbated the salt karstification. Extraction of natural brine has ceased and modern exploitation is mainly in dry mines or by deep controlled brine extraction leaving brine-filled cavities.

Distorted railway lines near Crew caused by salt dissolution aggravated by past brine extraction.
Distorted railway lines near Crew caused by salt dissolution aggravated by past brine extraction.

Since the cessation of natural brine pumping, the saline groundwater levels have returned towards their pre-pumping state. Brine springs are becoming re-established and natural karstification and subsidence may be expected to occur. The exact nature of the brine flow, and how it might interact with mined and brined areas, has yet to be studied.