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 |
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“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.”
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| 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.
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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.
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| 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.
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| 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.
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
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