Caves, subsidence and soluble rocks

Dissolution of soluble rocks produces landforms and features collectively known as 'karst'. Britain has four main types of soluble or 'karstic' rocks each with a different character and associated potential hazards.

Coastal Landslides Limestone

Karst is most often seen in limestone, a rock made up mainly of calcium carbonate.

Coastal Landslides Chalk

Chalk is a very distinctive, pure form of limestone, and is the most widespread carbonate rock in the country.

Coastal Landslides Gypsum

Karst in gypsum (hydrated calcium sulphate) is present mainly in the Permian rocks of eastern and north-eastern England.

Coastal Landslides Salt

In Britain, salt (halite or sodium chloride) occurs mainly in the Permian and Triassic rocks of central and north-eastern England.

Engineering problems

Engineering problems associated with these karstic rocks include subsidence, sinkhole formation, uneven rock-head and reduced rock-mass strength. Sinkhole formation and subsidence has the potential to cause damage to buildings and infrastructure.

It can be triggered by man-made disturbance of the ground, a change in drainage patterns, heavy rain or by water abstraction. Karstic rocks are often important aquifers, so their vulnerability to pollution is of particular concern.

Sinkholes Sinkholes (or dolines)

Sinkholes and associated phenomena are a common hazard in many karst terrains in the UK. Whilst the vast majority are small and do not cause any problems, some have the potential to damage property and infrastructure, or create problems during construction and development. In extreme and very rare cases sinkhole collapse may cause injury or even death.

Dissolution hazards team

Distribution of soluble (karstic) rocks in the Great Britain.

The dissolution hazards team investigates, defines, describes and databases the dissolution (karst) features of the UK. The information is compiled using geographic information system (GIS) technology that allows many different data sources to be combined. The database forms part of the hydrogeological inventory for the UK and is an important modelling resource for aquifer protection and the determination of hydrogeological/contaminant pathways. The information also underpins the national dissolution datasets-GeoSure and GeoReports.

When completed, the dataset will be suitable for incorporation into automatic site reporting.

For further information about the Dissolution Hazards Project contact: enquiries@bgs.ac.uk