Parts of extensive forests dating back 7,500 years that once marked Ireland’s Atlantic rim have been spectacularly exposed by the recent storms hitting the west coast. The powerful winds and pounding sea swell which stripped away layers of sand and stone shoreline have revealed patches of a “drowned” forest along the north Galway coastline west of Spiddal.
Walking out on to the shoreline at low tide, geologist Prof Mike Williams points to the oak, pine and birch stumps and extensive root systems which were once part of woodlands populated by people, wolves and bears.
These woodlands extended out into lagoons and marshlands that pre-dated the formation of Galway bay, Prof Williams says. An extensive layer of peat also exposed at low tide in the same location in Spiddal was formed by organic debris which once carpeted the forest floor.
The stumps at Spiddal are surrounded by root systems which are largely undisturbed. The carpet of peat is covered in strands of a reed called phragmites, which can tolerate semi- saline or brackish conditions.
“These trees are in their original growth position and hadn’t keeled over, which would suggest that they died quite quickly, perhaps in a quite rapid sea level rise,” Prof Williams adds.
Up until 5,000 years ago Ireland experienced a series of rapid sea level rises, he says. During the mid-Holocene period, oak and pine forests were flooded along the western seaboard and recycled into peat deposits of up to two metres thick, which were then covered by sand.
Prof Williams estimates that sea level would have been at least five metres lower than present when the forests thrived, and traces of marine shell 50cm below the peat surface suggest the forest floor was affected by very occasional extreme wave events such as storm surges or tsunamis.
He says most west coast sand-dune systems date to a “levelling” off period in sea level change about 5,000 years ago. Dunes in Doolin, Co Clare, are older still, having first formed around 6,500 years ago.
Prof Williams has located tree stumps in south Mayo and Clare, along with Galway, which have been carbon dated to between 5,200 and 7,400 years ago at the chrono centre at Queen’s University, Belfast. Some of the trees were nearly 100 years old when they perished.
Prof Williams believes the locations of the stumps should be afforded special area of conservation status. “Come the summer and the sands will have covered this over again until the next experience of extreme weather.”
With colleague Eamon Doyle, he is due to publish a paper on the findings in the Irish Journal of Earth Sciences . The research was supported by the Burren and Cliffs of Moher Geopark and the Geological Survey of Ireland.
Meanwhile, the links between archaeology, geography and the natural world are the theme of a series of Friday lunchtime talks running in Galway's City Museum to mark 90 years of archaeology at NUI Galway.
The landscape of Tara, Co Meath, is subject of today's talk by Conor Newman at 1.10pm. More details on website nuigalway.ie/archaeology