The Lyonesse Project

This project is co-ordinated by Historic Environment Projects, Cornwall Council. It will include the participation of experts from Cardiff, Aberystwyth, Exter and Plymouth Universities as well as the Cornwall and Isles of Scilly Maritime Archaeological Society (CISMAS). The project will also seek to engage the local diving community on Scilly.

Project Manager - Charlie Johns

The Isles of Scilly from the air

The Isles of Scilly from the air


“So all day long the noise of battle roll’d
Among the mountains by the winter sea,
Until King Arthur’s table, man by man,
Had fallen in Lyonesse about their lord.”

Alfred Lord Tennyson

The land of Lyonesse is a legendary, low-lying country said to once extend westwards from Land’s End to the Isles of Scilly. Elizabethan antiquaries collected reports current in the 16th century stating that Lethowstow, the Cornish name for this area, contained 'fair-sized towns and 140 churches' and was suddenly engulfed by the sea.

Although much of this can be dismissed as fantasy, inundation legends are found in many other parts of north-western Europe. Such stories may have their origins in folk memories of submergences that occurred during the prehistoric period.


Sea-level Rise

Since the Last Glacial Maximum (circa 20,000 BP) rising sea-level has served to isolate the Isles of Scilly from the Cornish mainland and transform them into their present form.  This process would have impacted significantly upon the islands’ inhabitants, as areas once suitable for settlement gradually became inundated.

The Isles of Scilly

The Isles of Scilly

An early submergence model for the islands postulated by Thomas has more recently been questioned by Ratcliffe and Straker through the dating of inter-tidal peat deposits. The Lyonesse project aims to build on previous work, resolve the question of sea level rise in Scilly and provide data to inform climate change studies.


Geophysical Survey - Sidescan sonar

Sidescan sonar will be used to locate and map areas of exposed peat on the seabed. Peat is a poor sonar reflector while sand, the predominant material on the seabed in St Mary’s Sound, is a very good sonar reflector. The outcrops of peat on the seabed should therefore be easy to locate using sidescan sonar.

The CISMAS CMax sidescan sonar
The CISMAS CMax sidescan sonar






Post-processing of the sidescan sonar data will allow plans of the areas of exposed peat to be input into the GIS database. The sidescan images will also be mosaiced to form a continuous image of the seabed surface. The sidescan equipment will be loaned to the project by CISMAS and operated during the project by CISMAS members. CISMAS has conducted similar surveys with success on the Colossus debris field survey and the Mounts Bay Maritime Survey.


Palaeoenvironmental Sampling

In the first year of field work the mapping and sampling of inter-tidal peats will be carried out during the lowest tides and will use existing data as a starting point to confirm areas of peat and to establish their hieght above ordanance datum. An initial assessment of the quality and quantity of material available at the potential inter-tidal sampling locations will be made.

Sampled peat and sand deposits will be dated using Accelerator Mass Spectrometry (AMS) and Optically Stimulated Luminescence (OSL) absolute dating methods.

The initial results of offshore survey will be used to identify a test site for offshore peat sampling. Various techniques for land and sea-based sampling will be tested. For offshore sampling, we anticipate using diver and diver-assisted sampling. Sampling of submerged peat or petrified forest exposures will be undertaken by divers from CISMAS.

CISMAS diver entering the water
A CISMAS diver entering the water.

Sample profiles will be selected to represent as wide a range of elevations as possible, including offshore locations. Results from the initial sampling will feed back into the second year of fieldwork, informing on further sample locations and sampling methods.

The second year of fieldwork will complete survey of the inter-tidal peats and check to see if any additional areas have been exposed. Work will focus on sampling a much larger range of inter-tidal and offshore peats, based on the data collected in year one, and increasing the range of elevations
sampled. Particular efforts will be made to retrieve offshore profiles based on the survey in year one. If the locations from the previous season require further sampling they will be revisited, although it is hoped to keep repeat sampling to a minimum.


English Heritage

The Lyonesse project is a two year project funded by English Heritage. Field work will commence in the summer of 2009, with further field work being carried out in 2010. For further information contact the Historic Environment Projects or CISMAS.


Further Reading

Ratcliffe, J and Straker, V. 1996. The Early Environment of Scilly: palaeoenvironmental assessment of cliff-face and inter-tidal deposits 1989-1993. CAU, Truro

Thomas, C, 1985. Exploration of a Drowned Landscape: archaeology and history of the Isles of Scilly. Batsford, London