Radar gets under the surface of Bermuda’s historical sites
A trio of archaeological experts is using radar technology to unearth secrets about Bermuda’s past.
Ground-penetrating radar, which uses pulses to create subsurface images, is already beginning to offer a glimpse into Bermuda’s history as part of an ongoing archaeological study.
The survey takes in three environmentally different sites – King’s Square in St George’s; Smallpox Bay on Smith’s Island in St George’s Harbour; and Trunk Island in Harrington Sound – and is being carried out by Michael Jarvis of the University of Rochester, David Givens, director at Jamestown Rediscovery and Peter Leach of Geophysical Survey Systems in New Hampshire.
The technology, which involves GPR units being wheeled over the surface of the sites, is being used for the first time in Bermuda for archaeological purposes. It is able to identify underground features such as concrete, asphalt, metals, pipes, cables and masonry as well as geological soil strata and buried archaeological and natural features.
The extent of a natural bay that sits on the current site of King’s Square and the location of a house that was documented on a 1663 map of Trunk Island in Hamilton Parish are just some of the promising discoveries being made.
Dr Jarvis said that while the precision of the radar in Bermuda’s environment was unknown before the work was carried out in April, initial indications were that it had been a success.
He said: “It worked extremely well in all three scenarios, which means it is probably a game changer for future archaeological surveys.
“The high value of this technology is you can cover a football pitch in two days going back and forth. You may see an early site and it is extremely important internationally so we know to stop a bulldozer from destroying that piece of heritage.
“We have lost dozens maybe hundreds of sites in Bermuda and we don’t even know what we lost.”
The team is working in partnership with the Bermuda Aquarium, Museum and Zoo, Bermuda National Trust, the St George’s Foundation and the Corporation of St George's.
GPR units can be used on a variety of surfaces including rock, soil, ice, fresh water, pavement and the floors of structures, to detect voids, structural cracks, changes in material properties and subsurface objects.
While radar images have been collected, they are in the post-production phase that will convert them into 3D plans. This data will be instrumental in identifying specific sites, some of which may be excavated this summer.
According to the project proposal paper: “There will be considerable public interest in the surveying at King’s Square, given its prominent location in this World Heritage Site town. Findings will be of tremendous interest given the longstanding conjectures and uncertainties regarding the locations and potential survival of traces of early town appurtenances.”
Survey results would be relevant to the outstanding universal value and management plan of the World Heritage Site.
He added: “The GPR survey’s results may also guide the planning and execution of future archaeological work in the area to ‘ground truth’ GPR imaging results.”
The initial findings indicate where the land was extended in several phases and has led the team to believe that about half of what is now King’s Square, the public centre of Bermuda’s first capital, is created land. The area is portrayed in numerous 19th-century sketches and photographs that reveal it once featured a natural cove or inlet, as well as a 17th-century Bermuda Company storehouse, bridge and fortified battery and public dock.
The project proposal paper published before the survey was carried out, said: “The anticipated stratigraphic profile thus includes packed heavily trafficked layers, an uneven/unknown matrix of likely large and small rubble and limestone rock fill (likely with trash, building debris, redeposited material/strata, and possibly deliberately scuttled boats to aid in land reclamation), a level surface built up during St George’s 17th-century occupation, and underlying pre-contact natural and bedrock strata.”
Seasonal excavations on Smith’s Island since 2012 have revealed numerous sharply defined circular and square features cut vertically into bedrock crust. The proposal paper said that because the site had a medical component – an 18th-century quarantine pest house and a 19th-century military retreat site from epidemics in St George’s, and was possibly the site of Governor Richard Moore’s briefly occupied 1612 town, it is expected the area would have numerous easily discernible features, ranging from possible graves to timber frame construction elements.
Trunk Island is the site of a house on English mathematician Richard Norwood’s 1663 island survey.
Dr Jarvis said: “We were particularly looking for the 1663 house and on the crest of a hill we found a square cut down into the bedrock – post processing should show its shape – it is right where the map has the house so it is highly promising.
“Trunk Island is five acres and a typical house of that period is 12ft by 16ft – the size of a detached garage, and without the radar we would be looking randomly.
“We know from the map that the Roberts family lived there in that house in that year but we know nothing about them, what they ate, what they did – all that can come from a subsequent dig.
“By the 1670s, the evidence of people living there falls by the wayside. In the 18th century no one was documented as living on the island.”
Dr Jarvis added: “The work creates a guide that we are excited to revisit this summer. The survey puts Xs on the map and now we can come back and dig. I am in great suspense.”