Map drawn by Stephen Hannon.
Some of the landscape features produced by the Ice Age are shown here. The map, which is simplified and generalized, shows the drumlin belt, and some (but not all) of the midland esker systems. The identification of areas with corries is indicative only. Knowledge about the impact of the Ice Age in Ireland has been built up over many decades and is the result of much patient research by many workers.
Although the map focuses on Ireland, it should be remembered that Ireland 's glaciation was part of a wider ice regime that also covered most of Britain. Moreover, the seas around Ireland were frozen, with a frozen ocean extending north-west to Iceland.
The extent of relatively recent glaciation across Ireland is shown in red and yellow on this map. The limits of this last major ice sheet can be traced in the landscape as zones where extensive, hummocky ‘moraines’ are significant. These mark the furthest point limits to which it is thought the ice advanced (perhaps after intervening retreats) during the last period between about 80,000 and 13,000 years ago. This last major period of glaciation is usually known in Ireland as the Midlandian. It was punctuated by at least one mild phase around 65,000 to 35,000 years ago.
A much earlier period of glaciation, or glaciations, occurred between about 300,000 and 130,000 years ago. This is usually referred to as the Munsterian, and may have been more extensive than the Midlandian. Areas with ‘Munsterian’, but not ‘Midlandian’, glacial deposits may be found in the zones coloured grey on this map.
The limits of the main Midlandian ice sheet run from west Clare through Limerick, south Tipperary , mid-Kilkenny and Carlow into Wicklow. Ice also advanced down the Irish Sea coming onshore in Co. Wexford (and, in earlier phases, also in Co.Waterford). The main ice sheet may have been 1000 meters thick in places, and covered most lowland areas except in the far south. Some hills or mountains may have protruded as 'nunataks' above the ice.
In some instances, however, the mountains were sufficiently bulky to allow enough snow to accumulate for local glaciations, including local ice caps, to develop. The most extensive such area was in south-west Munster where a 'Cork-Kerry' glaciation, centred on or close to the Kenmare river, developed independent of the general ice sheet. A Cork-Kerry ice sheet from Midlandian times extended eastwards to Ovens west of Cork city. Other areas where local mountain ice caps may have formed were the Wicklow and Mourne mountains, and the highlands of Donegal.
Most parts of Ireland were clear of ice by about 13,000 years ago, but a small area in north Antrim may have been affected by a readvance of ice from Scotland in a late cold phase. In some other areas, there is also evidence of a final ice phase between about 10,600 and 10,000 years ago. At Lough Nahanagan in Co. Wicklow, a small corrie glacier re-formed, the last expression of the most recent glaciation. Only time (or better science) will tell if the last ten thousand years represent a warm interval before another phase of glaciation.