Geology Site Account

Site name: The Gibson Boulders, Margaret Way, Saffron Walden.

Grid reference: TL 5369 3817

Brief description of site:

Large collection of glacial erratic boulders contained within a mound of grass and trees at the junction of two roads in the Gibson Gardens housing estate in the centre of Saffron Walden. The site consists of the largest number and greatest variety of erratic boulders in Essex, all of them brought to this spot by the owner of the land in the nineteenth century. The site is accessible at all times.

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Summary of the geological interest

At the junction of Gibson Gardens and Margaret Way in Saffron Walden is a collection of large boulders, some lying on the surface and others poking through the grass. All of them were brought to this spot by the owner of the land in the nineteenth century.

Erratic boulders are stones that have been transported by ice and these particular examples were carried to Essex by the great Anglian ice sheet which covered almost the whole of Britain during the coldest period of the Ice Age, some 450,000 years ago. Boulders such as these would have been frequently found in clay pits and gravel pits which were common around Saffron Walden in Victorian times.

The Gibson Gardens housing estate was built on land which was formerly the magnificent gardens at the rear of Hill House in the High Street. An 1877 map shows that this mound was a feature in the gardens and was the site of a summer house, the brick foundations of which can still be seen today. Until his death in 1883, the house and gardens were owned by George Stacey Gibson, naturalist and author of the first Flora of Essex which was the standard work on Essex botany until the 1970s. Gibson also had a great interest in geology (his collection of over 6,000 fossils was donated to Saffron Walden Museum on his death) and there seems little doubt that he must have formed this collection of unusual boulders in his garden. It is very fortunate that the site has survived the subsequent development.

Scientific interest and site importance

There are at least 25 boulders visible, of varying sizes up to 1.2 metres long. Most are obscured by vegetation and some almost completely buried. It is likely that there are many more buried in the mound. At least 9 different rock types are represented, some of which are distinctive rocks from the north of England and Scotland. The study of erratics can provide valuable clues to the flow of ice across the country and the nature of the landscape during the Ice Age.

The rock types include sedimentary rocks such as sarsens, puddingstone, sandstone, millstone grit, limestone and septarian nodules. There are also igneous rocks such as granite, dolerite and basalt. The largest boulder is a slab of colourful puddingstone approximately 1.2 metres long lying on its side in the centre of the mound.

This mound is of scientific and educational importance as it contains the largest number and greatest variety of erratic boulders in Essex. The stones link geology and social history and can tell a story not only about the Ice Age but also about the history of the town and one of its most famous residents.

Other information

This site is of historic interest. George Stacey Gibson was a famous naturalist and contributor to the prosperity of the town. The site also provides evidence of the former existence of these gardens, now completely lost to development.

The archive of photographs in Saffron Walden Museum (Pole 1997) contains several photographs of Hill House and the gardens in their heyday. A photograph of the summerhouse, taken in 1952, shows a few boulders at the base of the mound (Campbell 2000).

The site is adjacent to the pavement and accessible at all times.

The Gibson boulders. Photo: G. Lucy.