Geology in Dublin
The occurrence of marine shells in the Glacial deposits of Co. Wicklow was for a long time naturally regarded as evidence of submergence beneath the sea. The striations, however, that are found on the rock-floor show that ice sheets traversed the whole country, and the uplift of materials from lower to higher layers of moving ice may now be regarded as well established. Much of our knowledge of tin-history of East Leinster in Glacial times is due to the pioneer-observer Maxwell H. Close, whose work in the Dublin district has been completed by G. W. Lamplugh. The latter geologist also showed how such immature ravines as the Scalp south of Dublin, which is cut across a granite spur, and the Glen of the Downs in Co. Wicklow already recognised by Close as post-glacial are due to torrential waters set free by the melting of the ice-fronts. The gravels accumulated in subglacial channels form grass-covered mounds and ridges (eskers) in the Lucan and Tallaght area of the plain, and the 
Norman Tymon Castle stands on a small typical esker near Babrothery. Evidence from Europe shows that a dry age followed the final melting of the glaciers. Then came the milder years when bogs gathered in the plain, and- even across the crests of The Leinster Chain, from which they are now being washed or blown away. The tree-stems found in the mountain bogs indicate at least one forest epoch, when the slopes were clad with conifers to heights of 1800 ft. or more.
The floor of the Irish Sea, when freed from ice, very probably rose for a time as land, and channels may have been carved out in it by denudation of the glacial drifts. Peat and forests spread outward from the present coastline. A submergence allowed blue, 
marine muds to accumulate over these terrestrial beds, and a final elevation brought the drowned peat again near to the tidemarks. The coast between Bray and Killiney records these changes, and a raised beach connects Howth with the mainland, and is traceable under the east of Dublin city. The falls of the Liffey at Leixlip may be ascribed to this last uplift the river, like so many in East Leinster, has since sought its former channel through a deep covering of drift. The general drift-platform, indeed, raised the surface over which the rivers ran, and the return of the sea to about its pre-Glacial level has allowed them to cut ravines in the boulder-clays and gravels. The steep banks of the Liffey below Lucan or the Dodder at Tallaght and Kathfarnham afford fine examples of excavation. A pre-glacial northerly course has been indicated for the Liffey and for its important tributary, the Kings River, under the Slievethoul range, and down the Slade of Saggart into the plain. The rockravine at the Pollaphuca waterfall is clearly post-glacial, and the drift tilled hollow above the barrier traversed by it has been ascribed to glacial scour.