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8. Humans and glaciation
Living in a country like Ireland which has been covered by ice several times in the recent geological past, the effect of glaciation on humans is bound to be a marked one. There are several aspects of the Irish landscape which are a result of glaciation which have a profound effect on us in our daily lives. These are examined here in turn.Tourism
Soil Parent Materials
Soil and Gravel Aquifers
Engineering Aspects
Building Materials
Groundwater Protection
Education
Tourism
Ireland was almost completely covered by ice during the last glaciation. Thus our landscape is essentially a glacial one. Only about 5% of the countryside consists of bedrock outcrop (usually in mountainous areas) and the remainder of Irelands area is underlain by glacial material or glacially influenced materials (river alluvium, peat or coastal deposits).The simple fact that in order to reach bedrock over the majority of the country you must dig through several metres of soft debris (boulder clay) is testament to the huge effect glaciers have had on our landscape. Furthermore, the sculpting effect of the ice has been astounding, especially in mountainous areas where bedrock crops out. The attractiveness of the rugged glacial landscapes containing steep valley sides, waterfalls and scoured rock surfaces makes these areas very attractive to tourists. Just think of many of our most famous scenic sites:
The ice sculpted slopes of the Maumturk Mountains in Connemara
provide spectacular scenery for the hillwalker.
- Glendalough, Glenmacnass and Glenmalure (U-Shaped Valleys)
- Connemara (ice sculpted rock - see photo above)
- The Poisoned Glen (U-Shaped Valley)
- Killary harbour (a fjiord)
- The Cavan-Monaghan lakes (interdrumlin ponds)
- Curragh (outwash plain)
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Soil parent materials
Ireland has a long and well established agricultural heritage and this is a direct result of the suitability of Irish soils to agriculture. However, again this is directly related to glaciation. The fact that the majority of our soils are deep, well drained and suitable for tillage is related to the characteristics of the parent material.This parent material is of course the boulder clay, sands and gravels or clay which has been deposited by glaciers and their meltwater over the countryside. So without deep well drained parent materials we would have no deep, well drained soils. We would not have these parent materials without glaciation.
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Sand and gravel aquifers
Groundwater is an extremely important resource in Ireland and about 25% of Irelands drinking water comes from groundwater. In some counties, such as Roscommon and Laois, groundwater accounts for up to 80% of drinking water supplies.Much of this water is sourced in the Carboniferous limestone bedrock but the second most important source are the sands and gravels which were deposited by glacial meltwater at the end of the ice age. These sands and gravels are very porous and hold millions of gallons of water in their interstices. When this reserve is tapped into the water is clean and easily extracted.
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Engineering aspects
This aspect is very important and not so often realized. Glacial deposits provide the foundation for almost all major engineering undertakings. This has always been the case throughout history. The first people who came to live in Ireland after the end of the Ice Age 10,000 years ago made little impact on the landscape. They made their tools by working pebbles from streams or beaches. They had little ability to modify their environment. We can say they were reactive rather than proactive and would have chosen camping and dwelling sites in response to the amenities offered by existing shape of the landscape.When the first farmers came about 5,000 years ago with more advanced skills and technology they interacted in a more proactive way with the landscape. They built walls around fields, and they built tombs, often on hill-tops. They were builders in stone. They sought out particular types of stone from both local and distant sources and they used existing landscape features to great advantage. They appreciated the natural resources and used them to best advantage.
Bronze Age cultures that followed used the landscape in a similar way and left their distinctive mark on the landscape often modifying the existing Stone Age monuments. Human nature changes very little and still many of our roads still lie atop eskers, and drumlin tops still attract house builders. Today decisions as to road routes and other major engineering undertakings must take foundation conditions and topography into account and aggregate and other mineral resources must be properly planned. Planners must take account of all heritage considerations in planning. Glacial geology is critical in all of these areas.
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Building materials
Gravel pit cut into glacial sands and gravels
in County Meath
Glacial deposits provide us with much of our basic building materials. Sorted sands and gravels are easily extracted and require little sieving into various size ranges, so are prefect when used in making concrete blocks, pillars and other goods. Boulder clay is often used for fill. It is estimated that building materials extracted from glacial deposits is worth more than £100 million to the Irish economy each year.
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Groundwater protection
Groundwater protection is vital. These animals
have been dumped into a pit cut into sands and gravels.
The effluent seeps down into the groundwater which is
then extracted for drinking! A well situated close to
this pit would spell disaster for anyone drinking from it.
All water is vulnerable to pollution, and groundwater is no exception. The glacial deposits are the most important natural feature in influencing the vulnerability of groundwater to pollution. They can act as a protecting, filtering layer over the groundwater, depending on their type, permeability and thickness. In general, the higher the clay content, the lower the permeability and the greater the thickness, the greater the protection of groundwater from pollution. Were it not for glacial deposits all groundwater would be extremely vulnerable. Groundwater is most vulnerable where glcaial deposits are absent or very thin. The mapping of the glacial deposits thereby allows a groundwater vulnerability assessment to be made for any area or site.
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Education
Ireland has a glacial landscape fantastic by any standards. Basically the whole country has been affected in one way or another by ice and we possess relic landforms of every variety and size range. The pioneering work on glacial landscapes in the mid-nineteenth century was carried our largely in Ireland, and the Irish language has added many names and terms to the glacial literature e.g. drumlin, esker, corrie.Our landscape therefore provides a base for teaching about glacial studies at every level. As time goes on more and more glacial geology and geology students from abroad spend time in Ireland studying our landscape. So the next time you're tired walking up that hill, ponder a moment on why its there, and enjoy interpreting the landscape like geologists do too!!
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