Top section of William Smith's 1815 geological map of Britain

The top area of Britain's first geological map, published in 1815 by William Smith

Britain's first geological map

Two hundred years ago, a man called William Smith did something extraordinary. He became the first person to map the geology of an entire nation.

Not only was this scientifically significant, but in the process he produced something rather beautiful.

Smith's colourful and sophisticated geological map was based on his astute observation that rock layers (strata) could be identified by the fossils they contain. He noticed that the layers always seemed to appear in the same order and realised it was possible to predict where specific types of rock could be found across the country.

Smith’s map and ideas paved the way for a better understanding of geological time and laid the founding principles for geological surveys worldwide. His concept of using fossils to identify rocks is still very important today.

Fifteen facts about this ground-breaking map on its 200-year anniversary:

1. The complete map measures 2.6m by 1.8m and is made up of 15 sections.

You can see a full life-size replica of the map in our Images of Nature gallery.

2. Smith single-handedly mapped the geology of the whole of England, Wales and southern Scotland - an area of more than 175,000 km2.

3. A geological cross-section of the country from Snowdon to London accompanies the map. This illustrates Smith’s observation that strata across much of southern England dip towards the southeast, with younger strata lying on top of older ones.

Part of William Smith's 1815 map showing a geological cross-section from Snowdon to London

Geological cross-section from Smith's 1815 map
 

4. Smith used an innovative colour and shading system to represent each rock layer. Twenty-three strata were meticulously hand-coloured in different tints. Dark shading at the base of each stratum becomes lighter towards the top, creating a 3D impression.

5. He wanted to create something both useful and pleasing to the eye so he chose relevant but vivid colours to represent the rocks.

A particularly colourful segment of Smith's 1815 map from the Cotswold area

Smith illustrated the order in which rock layers occur by using darker shades for the base of each layer
 

6. The official title Smith gave to his map is certainly descriptive:

'A Delineation of the Strata of England and Wales, with Part of Scotland; Exhibiting the Collieries and Mines, the Marshes and Fen Lands Originally Overflowed by the Sea, and the Varieties of Soil According to the Variations in the Substrata, Illustrated by the Most Descriptive Names'.

It reflects the fact that Smith saw his map as a tool for industry and agriculture. To help people locate coal, for example.

7. Geologists today still use many of Smith’s names for strata, including London clay, green sand and cornbrash.

8. Smith made his first attempt to map the geology of an area in 1799, starting with Bath. He made his first small-scale attempts to prepare a national geological map in 1801, sketching the outcrop pattern of seven strata onto an existing map of England and Wales.

9. It took Smith another 14 years to gather enough information and funds to publish the first version of his map of Great Britain.

10. Smith dedicated the map to Sir Joseph Banks, the then President of the Royal Society and the project's most influential supporter.

Inscription on William Smith's 1815 map

The inscription Smith wrote on his 1815 map, dedicating it to Sir Joseph Banks
 

11. Britain's foremost cartographer of the time, John Carey, produced the topographical map on which he superimposed Smith's strata.

12. Publication of the map was funded by subscriptions. The map was offered in six different formats costing from five guineas to 12 pounds. 

13. Approximately 400 copies of the 1815 map were issued. Many are signed by William Smith himself. Less than 10% are known to still exist.

14. The Museum's collection includes five copies of Smith's 1815 map. 

15. Smith's ability to map Britain's geology was based on his realisation that the combinations of distinctive fossils within a rock can be used to identify it. He amassed a unique fossil collection. He used this as evidence to order his strata and make his maps. The Museum now cares for more than 2,000 of Smith’s fossils.

Fossil Explorer app

Uncover the ancient plants and animals hidden beneath your feet with this free app.