Digital Geological Map Data of Great Britain - 25k (DiGMapGB-25) version 2

Data identifying landscape areas (shown as polygons) attributed with geological names. The scale of the data is 1:25 000 scale. Onshore coverage is partial and BGS has no intention to create a national coverage at this scale. Areas covered are essentially special areas of 'classic' geology and include Llandovery (central Wales), Coniston (Lake District) and Cuillan Hills (Isle of Skye).

Data are supplied as five themes: bedrock, superficial deposits, mass movement, artificial ground and linear features.

Bedrock geology describes the main mass of solid rocks forming the earth's crust. Bedrock is present everywhere, whether exposed at surface in outcrops or concealed beneath superficial deposits or water bodies. The bedrock theme defines landscape areas (shown as polygons) attributed with geological names.

Geological names are based on the lithostratigraphic or lithodemic hierarchy. The lithostratigraphic scheme arranges rock bodies into units based on rock-type and geological time of formation.

Where rock-types do not fit into the lithostratigraphic scheme, for example intrusive, deformed rocks subjected to heat and pressure resulting in new or changed rock types; then their classification is based on their rock–type or lithological composition. This assesses visible features such as texture, structure, mineralogy.

Superficial deposits are younger geological deposits formed during the most recent geological time; the Quaternary. These deposits rest on older rocks or deposits referred to as bedrock. The superficial deposits theme defines landscape areas (shown as polygons) attributed with a geological name and their deposit–type or lithological composition.

Mass movement describes areas where deposits have moved down slope under gravity to form landslips. These landslips can affect bedrock, superficial or artificial ground.

Mass movement deposits are described in the BGS Rock Classification Scheme Volume 4. However the data also includes foundered strata, where ground has collapsed due to subsidence (this is not described in the Rock Classification Scheme).

Caution should be exercised with this data; whilst mass movement events are recorded in this layer, due to the dynamic nature of occurrence significant changes may have occurred since the data was released, as such it should be viewed as a snapshot in time (data should be regarded as at 2008).

Artificial (man-made) theme (shown as polygons) indicates areas where the ground surface has been significantly modified by human activity. Whilst artificial ground may not be considered as part of the 'real geology' of bedrock and superficial deposits it does affect them. Artificial ground impacts on the near surface ground conditions which are important to human activities and economic development.

Due to the constantly changing nature of land use and re-use/redevelopment, caution must be exercised when using this data as it represents a snapshot in time rather than an evolving picture hence the data may become dated very rapidly.

Linear features (shown as polylines) represent geological structural features e.g. faults, folds or landforms e.g. buried channels, glacial drainage channels at the ground or bedrock surface (beneath superficial deposits). Linear features are associated most closely with the bedrock theme either as an intrinsic part of it for example marine bands or affecting it in the case of faults. However landform elements are associated with both bedrock and superficial deposits.

All five data themes are available in vector format (containing the geometry of each feature linked to a database record describing their attributes) as ESRI shapefiles and are available under BGS data licence.