The Landscape of Abbey and Surroundings

From talk given at Abbey's Hidden Heritage Conference - February 2014

Zena Hoctor

Introduction

In order to understand what shapes the landscape that surrounds the village of Abbey we need to be aware of

  •  the bedrock that forms its skeleton,
  •  the loose rock, stones, gravel and soil on top of the bedrock which create the   small hills and hollows
  • and the climatic changes it has undergone.

All of these things influence the land we live on today.

Moving back in time

To begin our exploration of the landscape of Abbey and the surrounding region, we travel back approximately 500 million years, to a time when the location of the land on which Abbey now stands was 30o south of the equator. At that time the continents as we know them today did not exist. Instead there were two great landmasses separated by a huge ocean, known as the Iapetus. The climate was very hot and the land was covered by desert. Over time, the action of the heat and torrential rains broke up the rocks that made up these landmasses. Sediments were carried by rivers into the Iapetus Ocean and deposited on the seabed.

The Creation of the Old Red Sandstone

Due to the continuous movement of the earth’s plates, the two landmasses moved towards each other and by the time approximately 100 million years had passed, the Iapetus Ocean had closed and the two landmasses had collided. This huge collision crumpled and crushed the rocks on the ocean floor and pushed them up creating a chain of mountains.

As soon as these mountains were created, they began to be eroded. Torrential rivers swept down the mountain sides, cutting out deep valleys and ripping away the loose rock, which had originally been deposited on the floor of the Iapetus Ocean. All the materials carried by the rivers were dumped at the base of the mountain slopes in great fans of debris. Over the following millennia these rocks, muds and sediments solidified and formed the Old Red Sandstone rocks which we see all around us today in the Slieve Aughty Mountains.

Limestone forms

Approximately 340 million years ago the land that would eventually form Ireland had drifted to about 10o south of the equator. Here it was covered by a warm, shallow tropical sea full of corals and shellfish. Naturally precipitated calcite from the seawater and calcite in animal and plant remains accumulating on the sea floor eventually compacted to form limestone. Many of the skeletons of the marine organisms were preserved in this limestone as fossils and are still visible today in the limestone rock that underlies most of south-east Galway.

Shaping the Landscape

The two major rock types, Old Red Sandstone and Limestone, found around Abbey were laid down in flat, horizontal layers many millions of years ago. Yet the landscape that surrounds us today is full of dips, hollows and even mountains. What happened?

The earth’s plates constantly move, bumping and grinding off each other. About 290 million there was collision of continental plates in southern Europe and the stresses in the earths plate pushed so far north that the rocks of southeast Galway were folded and tilted, pushing up the Slieve Aughty mountain range.

Ice Depositions

As well as huge earth movements there have been great climatic changes throughout time. These changes included ice ages. The last ice age in Ireland occurred between 25,000 and 12,000 years ago. At that time glaciers moved in a north-east to south-west direction across south-east Galway and out into Galway Bay. Moving slowly across the landscape they scoured the surface and carried away loose rock and soil.

About 12,000 years ago, as the climate began to warm, the ice began to melt. Sand, gravels, stones and rocks (glacial drift) that had been trapped in the ice dropped back onto the landscape. How and where they fell, depended on how and where the ice melted. Glacial drift was deposited in different ways in different locations and so resulted in many different landforms.

Around Abbey, kames are a common glacial drift landscape feature. They are small rounded hills of sand and gravel. They formed when the rate of melting of the glacier was greater that it’s rate of advance i.e. it literally stopped and melted where it stood, dropping its load onto the landscape.

Eskers were formed when the meltwater flowed under the glacier like an underground river. Sand, gravel and small rocks carried in the water settled out on the ‘bed’ of the river. The ice formed the ‘banks’ of the river. When the ice ‘banks’ melted, the water of the river dispersed. The ‘bed’ survived as a long narrow sinuous ridge of layered sand and gravel, standing high above the surrounding landscape. Eskers are visible running to the north of Abbey around Duniry and Tynagh.

When the meltwater ran off the sides of the glaciers, the glacial drift was deposited in lines parallel to the direction of the flow of the glaciers. This type of deposition created small hump-backed hills of glacial drift. Today, we refer to these hills as drumlins (droim-ridge or hill). They can be distinguished from kames, as they occur in lines. A line of drumlins extends in a north-east to south-west trend from the Slieve Aughty Mountains near Derrybrien to Tubber, indicating the flow of the glacier across south Galway into north Clare and out into the Atlantic.

 

 

This page was added on 14/09/2014.

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