Southern Ireland’s crust is being levered downwards by “isostatic rebound,” where land mass that was depressed by the huge weight of ice sheets during the last glacial period rises, the Connacht Tribune reportrd. This means that northern parts of Ireland are rising while southern areas, such as Connemara, are going down.
Welsh-based geologist Jonathon Wilkins came up with his findings while investigating the South Connemara coastline while on vacation in Connemara.
He said he was traveling along a road in Mainis, near Carna, when, “I realized something strange was happening in the landscape. Close to the laboratory of NUI Galway’s Ryan Institute the tide was flooding sinuous channels in a peat bog, not a salt-marsh as I had first supposed, and peat bogs don’t accumulate in salt water.”
Wilkins found there were numerous tree stumps with radiating root plates.
The stumps are buried beneath peat, up to two meters in one location.
“The level of the stumps is below the highest tide level, and it has to be assumed that they didn’t grow with their roots in the sea,” Wilkins writes in an article published in Earth Science Ireland, an online magazine.
“So here is very powerful evidence that sea level, to my surprise, is rising in this area, and demonstrably over quite a short time scale.”
"Changes in the disposition of the shoreline can be very complex and difficult to unravel where there is sediment redistribution in the form of shingle bars and sand dunes which comprise re-mobilized glacial sediments, but here there are virtually none.
"There is just peat and granite bedrock or boulders, and once the peat is suspended in the seawater it floats away and is completely lost.
"The sea level rise is well known, it turns out, and is the consequence of much thicker ice in the northern part of the country causing a stronger isostatic rebound.
"The crust beneath southern Ireland is being levered downwards by this movement, so Belfast, Dublin and Donegal are going up and the southern counties including Galway are going down.
"As the sea is also rising slowly world-wide due to warming, the picture is less simple than it is drawn here, but it is certain that the sea has encroached considerably onto the land around Galway Bay since the ice melted, and the more recent effect is demonstrated very clearly in these key localities.
"Erratic boulders are everywhere on the South Connemara shore, but I had not expected that they were mostly surrounded by a blanket bog until it was claimed by the sea, and that the strange, watery landscape is indeed being shaped by a slow drowning."
Wilkins’ article was raised at a meeting of Galway City Council by Sinn Féin Councillor Cathal Ó Conchuir, who said further academic investigation was warranted.
*Originally published March 2015