Ice Age experts explore local landscape
Eskers at Clonmacnoise, Ferbane, Birr and Clara, as well as the ridges and mounds in fields surrounding Tullamore were explored by an international group of Ice Age experts recently.
A field trip led by Catherine Delaney, senior lecturer at Manchester Metropolitan University, explored how climate change is affecting and causing modern ice sheets to recede.
The group, made up of glaciologists from the USA, Canada, China, Japan, South Korea, Sweden, France, and the UK, looked at the landscape and sediments left behind by ice sheets after the last Ice Age.
"It is very hard to study what happens under a modern ice sheet - they are kilometres thick. This is why Offaly is so important," Catherine Delaney told the Offaly Independent.
"All over the county you can see the 'footprint' of the last ice sheet to cover Ireland, about 18-20,000 years ago. It’s exceptionally well-preserved in Offaly," she explains.
"First of all, there are the eskers, which are world famous, and were formed in tunnels under an ice sheet," continues Catherine. "By studying the the geomorphology of the eskers and the sediments they are formed from, we can reconstruct what was happening to meltwater under the ice sheet.
"Just as interesting are the small mounds and hillocks you see in many of the fields in Offaly. They don’t look like anything much, but they were formed by the ice sheet squeezing the wet sediment underneath it as it moved. The patterns these ridges and mounds make show that the ice sometimes speeded up and surged forward, and then stopped and stagnated for a bit.
"Finally, as the ice retreated, it formed a dam running north to south across Offaly, that blocked a huge lake against the watershed between the Shannon and the Barrow and Boyne rivers. As the ice retreated westward, the water escaped down the Shannon, but before that happened, it covered an area over 1600km2.
"The meltwater coming off the ice sheet carried fine sediments into this lake, and these are found underneath the bogs - in fact, they are the reason there are so many bogs in Offaly.
"As part of my research in Offaly, I and my colleagues have been looking at these sediments, as they contain a record of what was happening to the ice sheet, and we will be presenting our research at the INQUA Congress."
"These samples are key to understanding what is causing sea-level rise, which affects us all, says Catherine.
"Ice sheets don’t react straightforwardly to an increase in temperature. Sometimes they will speed up and spread out, as the extra water lubricates the base of the ice so it can slide more quickly.
"Sometimes they slow down and stop flowing because new tunnels open up and move the meltwater away efficiently. All of this affects how quickly the ice gets to the warmer margins of the ice sheet, and how quickly the ice sheet melts."