The Map that Changed the World

Britain's first geological map

By Lisa Hendry

More than 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.

Download a larger version of William Smith's 1815 geological map PDF (6.4MB)

Fifteen facts about this ground-breaking map: 1. The complete map measures 2.6m by 1.8m and is made up of 15 sections.

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.

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.

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.

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 (such as ammonites) 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.

Sourced from: Britain's first geological map | Natural History Museum (nhm.ac.uk)

Smith’s Explanation of His Map of Geological Strata in England and Wales Smith’s Explanation of His Map of Geological Strata in England and Wales (victorianweb.org)

William Smith’s Geological Map of England William Smith’s Geological Map of England (nasa.gov)

William Smith William Smith (1769-1839) (nasa.gov)

Videos to Watch Map that changed the World – William Smith Strata Map Map that changed the World - William Smith Strata Map - YouTube

A Short History of Geological Mapping: from William Smith to present A Short History of Geological Mapping: from William Smith to present. With Owen Green & Mike Searle - YouTube

Explore Geology Discovery Geology – British Geological Survey Discovering Geology - British Geological Survey (bgs.ac.uk)

Interactive Geology Maps of Australia Interactive Maps (ga.gov.au)