The origins of systematic geological mapping in Britain

BGS Information Hub


Henry Thomas De la Beche (1796–1855) was perhaps the first person to geologically survey an entire Ordnance Survey one-inch topographical map sheet.

His first completed sheet (Old Series 22) was undertaken at his own expense in 1830–31 and covered south-east Devon and part of Dorset, including Lyme Regis where he was then living.

Ordnance sheet 22
Information icon

Part of Ordnance sheet 22, Sidmouth to Lyme Regis, geologically coloured (De la Beche’s personal copy, 1834 colouring scheme).

In May 1832 De la Beche succeeded in obtaining financial support from the Board of Ordnance to undertake a geological survey of Devonshire. One stipulation was that he should consult with the Geological Society to come up with an agreed scheme of colours.

The resulting table of 16 formations (right) soon became inadequate as more rock units were identified during the course of mapping. Today BGS recognises some 2500 formations — see the BGS Lexicon of Named Rock Units.

Founding of the Geological Survey

With the support of the Geological Society, De la Beche next succeeded in establishing the Geological Survey on a formal basis, on 11 July 1835, as a department within the Ordnance Survey.

Mapping progressed into Cornwall, and by 1837 the whole of South West England had been geologically surveyed.

Preservation of field maps and fossils

The Devonian Controversy of 1834–39 involved a dispute over the application of fossil evidence to stratigraphic interpretation. The dispute threatened to undermine the authority of the Geological Survey, but it led to an appreciation of the need to establish a scientifically based collection of fossils in support of the mapping programme.

De la Beche preserved his field maps (cut up into slips) as a record of his actual observations. BGS now holds more than three million fossil specimens, about half a million rock samples (excluding borehole material), and 68 512 registered field slips (excluding Old Series one-inch slips, example below right, which are currently unregistered).

Application of colour to geological maps

watercolour cakes
Information icon

A selection of watercolour cakes supplied by the firm of James Newman, some of which were specially formulated for the use of the Geological Survey.

The colours chosen to depict rock formations usually attempted to match the overall colour of the rocks themselves, as exemplified by William Smith’s celebrated geological map of England and Wales (1815), and the Geological Society’s own version compiled by G. B. Greenough (1819) — the latter being the starting point for De la Beche’s first colour scheme.

As more formations were recognised it became necessary to employ a wider range of colours or to combine them with ornament.

The colours themselves were based on watercolour pigments available from art dealers, but in due course a need arose for the Survey to negotiate the production of specially formulated pigments.

Why the constant need for revision?

Given the rapid pace at which the Government of the day expected the Geological Survey to proceed, and the cartographic limitations imposed by the one-inch scale, De la Beche soon came to recognise the provisional nature of the geological mapping being conducted at that time.

In addition, the significance of superficial deposits was not recognised until the Survey had reached the northern Welsh Borders and East Anglia, where glacial deposits thickly blanket the bedrock geology.

The introduction of topographical maps at the six-inch scale in the mid-nineteenth century created a need, and fulfilled a desire, for more detailed geological information.

This process of adding greater detail and refinement has continued up to recent times, with each resurvey adding greater understanding to what is essentially an interpretation based on the best available evidence.

Mapping in the 21st century

BGS SIGMA mapping software
Information icon

Data collection using the latest technology; a rugged tablet PC with BGS•SIGMAmobile software.

Since 2007, BGS has dispensed with the use of paper field slips and now gathers field data utilising a tablet PC.

BGS offers free access to geological map data via iGeology, a free smartphone App. iGeology allows the user to access a geological map of the UK by browsing the map or by entering a place name or postcode.

You may also be interested in:

BGS Maps Portal

BGS Maps Portal

High resolution viewing of images of almost all small and medium scale maps produced by BGS since mapping started in 1832.

Show more
BGS Maps Portal

About the BGS maps portal

The scope of the site is described, what map series are included and what are excluded. Includes brief notes on navigating and using the Maps portal.

Show more
Sir Roderick Impey Murchison

Geological survey historical notes

Brief historical notes and links to key documents on the early 1:63 360 map series for England and Wales, Scotland and Ireland.

Show more
Geological history of England Wales

Geological Survey History -England and Wales

A short history of the Geological Survey of England and Wales.

Show more

Get in touch

For more information about our datasets, technologies and map viewers please contact us

Was this page helpful?

  • How can we make this section better?*

  • Please select a reason*

  • How can we make this section better?*