County Cork Geology
The Blackwater, after bending south at Cappoquin, enters a deep ravine, the sides of which rise to between 300 and 400 ft. Now if a dam 80 ft. high were formed across the river at Dromana, it would, after forming a lake about Cappoquin, make its way to the sea at Dungarvan. Similarly if the east and west passages of the Lee were blocked the river would go along by Midleton to Ballycottin Bay. The Bandon too, under similar circumstances, would find an outlet by the Owenboy valley and enter the sea at Cork Harbour by Carrigaline.
It is evident that the carving of these gorges was begun before the valleys behind had been reduced to anything like their present levels.
Let us now consider events in the light of a theory proposed by Professor Jukes as far back as 1862. After the formation of the Coal Measures the whole of Munster was affected by forces which elevated the crust and produced folds in the rocks. The new land thus formed was subjected to denudation by the sea, and most of our coal supplies were removed, leaving a gently sloping surface of limestone through which here and there the Old Red Sandstone rocks made their appearance in the crests of the folds or anticlines 
where the limestone had been eaten through. Eventually after another uplift a series of rivers flowed down this sloping surface towards the south. The Brinny brook continued its way along the lower course of the Bandon, the stream of the Glanmire valley came down by Passage West, and the Owenacurra flowed past Midleton and by Passage East and effected a j unction with it somewhere in Cork (Holiday Cottages, Cork, Ireland) Harbour, the con- fluent waters going through the harbour entrance to the sea, whilst in the case of the Blackwater the youthful ravines of Dromana and Carnglass formed the channel for a river flowing from the Knockmealdowns.
Continued denudation in the course of time laid bare the sandstone all along the anticlines of the east and west folds, and since the sandstone was more resistant than the limestone which remained in the synclines, the east and west tributary valleys were 
carved out of the latter rock, which yielded so readily to solution by water con- taining carbonic acid gas. The western tributaries of the streams increased more rapidly than those flowing from the east, for the slope of the land was in their favour, the higher ground being in the west; and thus it comes about that the original western tributaries now form the main portions of the present-day rivers. Near Killaloc the Shannon passes through a gorge, the banks of which run up to elevations of 1746 ft. on the western side and 1517 ft. on the eastern, whilst the bed of the river is only 108 ft. above sea level. It is quite certain that the limestone of the plain north of this was much higher than either the Slieve Bernagh or the Arra mountains when the Shannon began its life-work; and that it had power to carve through the more resistant sandstone rocks as rapidly as the lowering of the limestone plain to the north was affected by denudation.
The same reasoning can be applied to the Suir, which leaves the limestone plain and goes through a gorge with sides 250 ft. in height near the city of Waterford.
In Cork (Bed and Breakfasts, Cork, Ireland) the striations on the rocks run east-south-east, and these, taken in conjunction with other glacial data, indicate an ice movement in that direction. The sea to the south was probably occupied by ice, else we should expect to find that tongues of ice escaped through such openings as Cork Harbour, but of this there is no evidence. On the shrinkage of the Irish Sea ice, the Cork ice- sheet advanced, and we find south of Youghal red boulder clay overlying the marly marine deposit, showing that there were no intervening interglacial deposits in this district.
On the shrinkage of the Irish Sea ice, the Cork ice- sheet advanced, and we find south of Youghal red boulder clay overlying the marly marine deposit, showing that there were no intervening interglacial deposits in this district.
In Co. CCork (Hotels, Cork, Ireland) are quite a number of instances of river diversion. The Bride stream that entered the Lee valley from the north by the Shandon dap was blocked by a stratified gravel deposit. This was probably formed in a lake at a time when the Lee valley was occupied by a glacier. After the ice had disappeared this lake sought an outlet and formed the present, ravine known as Gouldings Glen, at the side of the main obstruction. The river soon removed the gravels and cut deeply into the sandstone. Another striking instance occurs at Tattans Gorse, about half-way between Watergrasshill and Midleton. The stream flowing from the north was locked by ice or drift at Dooneen Bridge, and a new course with steep sides 70 ft. high was cut out of sandstone rock a little to the east, and through this the Leamlara stream still flows. At Kiverstown, in the Glanmire valley, the Glashaboy stream has been diverted from its original course by a bank of glacial gravel, and a passage has been cut through the rock (50 ft. deep and 200 to 300 yards long. The stream that flows through the pass of Keimaneigh could not have. cut that famous gorge. More probably it was rapidly cut out by flood waters consequent upon the shrinkage of the ice.
Sometimes two or more sets of striations are observ- ble; in Cork and Kerry we have many examples of his. Thus at the head of the Slaheny valley is a rock surface with two distinct sets of striations and a third somewhat less distinctly marked. The chief glaciation has produced ridges and furrows running S. 33 E., while a later set of striations runs E. 10 S. These later striations are found on only one side of the smoothed idges, and consequently we assume that the striated side of the ridge was that opposed to the motion of the after glacier.
While, as already stated, the general course of the glaciers in Cork (Self Catering, Cork, Ireland) was east-south-east, they nevertheless followed valleys which deviated from this direction. Thus a part of the glacier from the Roughty valley, east of Kilgarvan, went N.E. towards Ballyvourney, while an- other part kept on down the valley of the Toon to Macroom. The striations show that meanders of the valleys were also followed fairly closely by the ice, or that a differential movement existed in different parts of the same ice mass.
The gravels have been already referred to as being formed by floods consequent upon the breaking up of the ice-sheet. They are found at different levels. The higher ones were formed by the earlier floods at a time when the hill-tops were stripped of ice, the lower ones later on when ice occupied only the lower parts of the valleys. Behind the village, of Watergrasshill, at a height of 600 ft., are representatives of these earlier flood gravels, while in the Lee valley, about Cork and also about Middleton, are later deposits.
Eskers, or low winding ridges formed of water-worn Glaciated rock surface, Co. Cork and stratified material, are not developed in such fine proportions in Munster as in Kings County, Westmeath, or Tyrone. A small one occurs at Dooneen Bridge, 5 miles south-west of Limerick, and another at Kenmare, just below the Great Southern Railway Hotel. These seem to have been formed where sub-glacial streams heavily charged with sediment and flowing in ice tunnels reached the quiet waters of a lake or estuary. The gravels which were spread out on the bottom of the valleys by the floods during the time of recession f the ice have since been cut into by the rivers, and terraces have been formed marking the different successive flood levels. Good examples of these are seen in he Lee valley at Inniscarra and Carrigrohane, six and Terraces at Inniscarra on the River Lee three, miles respectively west of Cork. In these the highest terraces give approximately the level of the old gravel-covered plain. As the river deepened its bed new flood terraces were formed at successively lower levels. At many points along the southern coast-line from Carnsore Point to Baltimore portions of an old shore- line have been traced. Where well preserved, as at Myrtleville, a little west of the entrance to Cork 
Harbour,it consists of a tidal platform rising from present mean- tide level on tlie outer edge to a few feet above high- tide mark on the landward side. Upon this we get, amongst other deposits, one of boulder clay. Now if we consider that the gorges of the Lee at Passage East and Passage West were formed by the cutting action of the river when the land stood at a higher level, we must admit, on the testimony of the raised beaches, that a pre-glacial subsidence admitted the sea to the lower parts of the rivers and formed those long inlets or rias, examples of which we have in Waterford and Cork Harbours and in the long inlets which form such striking features of the coast-line of Cork and Kerry. As this old beach corresponds with those on the opposite side of St Georges Channel, it is fair to assume that Ireland was separated from England before the advent of the glacial period, though during a part of this period a land-connection may have been re-established. Be that as it may, we have at the present time the sea level very nearly restored to the old position which it occupied before the coming of the ice age.