Radar to show what lies below the sand of Longis Common

GROUND-penetrating radar could help finally reveal the secrets of Longis Common in Alderney in a few weeks, centuries after sand covered the area.

The final day of the 2018 dig on the Longis site which was led by Dr Jason Monaghan. (Picture by David Nash)
The final day of the 2018 dig on the Longis site which was led by Dr Jason Monaghan. (Picture by David Nash)

A grant from the Royal Archaeological Institute is allowing Dr Rob Fry, from Reading University, to come to the island to spend a week scanning as much of the area as he can.

States archaeologist Phil de Jersey said this was the first time he has seen the scanning technique used in the island and he was excited to see what it could find.

‘Longis has very deep sand deposits and that’s what GPR does,’ he said.

‘It can get a lot deeper [than other techniques] and it does it in slices through the layers, so you can get a pictures of what structures there could be at one metre down, 1.5m down or two metres down.’

It will not just pick up stone structures, but also where the ground has been disturbed, such as post holes or cuts in the earth.

The common became a focus for archaeological interest after Iron Age bones were found when an electrical cable was dug in 2017.

It led to evidence of a Roman settlement and several Iron Age graves being found. But it has proved a challenge to know where to look next.

Dr de Jersey said that given unlimited time, organisers would like to cover 75,000sq. m of the common.

But with just seven days to do the scanning, Dr Fry will be doing as much as he can in that time.

Damp soil should not slow the equipment, which will be carried in a harness, but vegetation might.

Overall the two-metre deep layer of blown-in sand had protected the history of the area.

‘The Longis Common sand came in during the late Roman and early Medieval era and no one did much in the area again,’ Dr de Jersey said. ‘So the chances are, it [the history] is all still there, which is fantastic.’

But the specialists need to know where to dig.

‘If we just removed some sand and dug a big hole, we could then not find anything,’ Dr de Jersey said.

‘So hopefully the GPR will give us an idea of where we could dig at a later date.’

It is hoped that dig will take place early next year, but still needs to be firmed up.

The nearby Nunnery has been dug a number of times before and Dr de Jersey said there was only a few areas left to explore in the historic site. But the common was still largely unexplored.

He said they were not sure what they could find. There are hundreds of years between the few Iron Age burials found, so he said it would be nice to find some bones that filled in the large time gaps, or some grander graves, with interesting grave goods.

He also said it would be amazing to find more evidence about where the Iron Age people lived.

‘I would love to find a [Roman] villa and it would be nice to find a mosaic,’ he said.

‘In the Paddock Field dig, we did get possible tessera, which would be used in mosaics, so you never know.’

While some of the common was dug by Occupying forces during the World War II, who used the sand for construction, Dr de Jersey said the forces would stop when they reached earth, meaning the archaeology was not disturbed.

The work starts at the end of this month.

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