The National Monuments Service is investigating a report of serious damage to a unique 3,000 year-old “vitrified” hillfort close to Cavan.
The hillfort is a listed monument on private land, and is the only confirmed example of its type on the island of Ireland, according to archaeologist Michael Gibbons.
“Vitrified” forts were built of stone but laced with timber, and subjected to intense heat which fused the rock and gave them a glass-like aspect.
Archaeologists have long been mystified by the reason for the burning at high temperature – conducted either during warfare, for ritual or ceremonial purposes, or as a warning to opponents.
About 70 such forts have been identified in Scotland, and several hundred more across Europe.
The fort at Shantemon, several kilometres north-east of Cavan town, is the only confirmed example here, and dates from 1200 to 1,000 years BC, Mr Gibbons says.
It was first identified as a “vitrified” fort by clergyman and author Rev Caesar Otway in the Transactions of the Royal Irish Academy in 1818, and was marked as such on an early Ordnance Survey map of the area.
As Mr Gibbons describes, vitrification occurs when a timber frame stone rampart is “consumed by fire with heat in between 750 and 1000 degrees Celsius”.
“At these temperatures, the burning rampart collapses, and the rock fractures and becomes liquid,” he says.
“Days after the fire burns out and the rampart finally cools, the burnt and molten rocks form blocks of conglomerate stone, giving it a glass-like appearance,” he says.
Mr Gibbons was visiting the area with Galway city heritage officer Dr Jim Higgins when both noticed the damage, as confirmed by aerial photographs.
Mr Gibbons lodged a report last month with the Office of Public Works. Under current legislation, any work close to a listed monument requires two months’ notice.
The Department of Culture, Heritage and the Gaeltacht has confirmed that it received a report in relation to a listed monument, and had conducted an inspection.
It said it could not comment further while its report, which is “under consideration”, was the subject of an ongoing investigation.
It said that this fort is “not a national monument in the ownership of the State and the Office of Public Works does not, therefore, have a role with regard to its care and protection”.
Mr Gibbons says it is a “ tragedy” that the fort’s significance was not recognised earlier by the State and given greater protection, given its “undoubted status” within Irish archaeology and its international significance.
The fort was an example of the deep connections between the north-east and Scotland, with the dating of some of these structures extending from the Bronze Age to the 7th century AD, Mr Gibbons says.
