Seabed survey identifies fault line that united Ireland

An offshore "Eiscir riada" or glacial ridge which gives the island of Ireland one of its "feet", and a 40km fault line extending…

An offshore "Eiscir riada" or glacial ridge which gives the island of Ireland one of its "feet", and a 40km fault line extending from the Shannon estuary, are among new discoveries by the State's €12 million seabed survey.

The 40km sub-sea fault line extending up to the Shannon mouth marks the "suture" joining the island of Ireland, which was formerly in two halves, according to scientists addressing a Marine Institute conference in Galway yesterday.

It has already been dubbed the "Kerry" or "Brendan" trough, after the mountain and navigating saint of the same name. However, a formal name will have to be approved at international level, with local consultation.

A 15km-long glacial moraine or sub-sea "Eiscir riada" identified off the southwest coast gives the Dingle peninsula its particular shape - and the island a distinctive "foot" - Koen Verbruggen of the Geological Survey of Ireland (GSI) told the conference.

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It was confirmed by a Russian colleague, Andrey Borovik, during work on data collected by the ships involved in the national seabed survey.

Further geological study and dating of such features may contribute to climate change research, which stands to benefit from much of the information gathered during the survey, Mr Verbruggen said. Already, mapping was carried out under the seabed survey off Belmullet, Co Mayo, for a new wave energy site.

Drill cores taken by the project in Galway Bay last year have also shown evidence of "extreme weather events" in the relatively recent past, which may be linked to past climate change.

The Galway Bay data is contributing to a new study on groundwater interactions, and the impact on cyclical flooding and drought events which are predicted to become more frequent.

The survey data is also being used by scientists working on the feasibility of extracting aggregates from the Irish Sea. Such offshore extraction could reduce significantly the carbon footprint of the construction industry, if it does not impact negatively on fish spawning and marine habitats.

The seabed survey was initiated almost a decade ago, and is currently focusing on inshore sub-sea mapping after extensive work with a fleet of vessels offshore. This latest phase, known as Infomar (Integrated mapping for the sustainable development of Ireland's marine resource), is managed jointly by the GSI and the Marine Institute.

Last year, Infomar scientists surveyed more than 4,600sq km, and areas off Dingle were mapped, along with Bantry, Dunmanus and Galway Bays.

Marine Institute scientists John Evans and Tommy Furey said that the focus this year will be on mapping the northwest, including Sligo and Donegal bays, using both airborne laser and ship-mounted acoustic systems. Work will also be carried out off Waterford and Cork and in Dublin Bay.

The project has a €4 million annual budget until the end of this year, but the Government has committed to continuing it until 2012 under the National Development Plan. An appraisal of its value is currently being carried out by consultants.

Lorna Siggins

Lorna Siggins

Lorna Siggins is the former western and marine correspondent of The Irish Times