Source :

The Boyne Valley in the Ice Age - Robert T. Meehan & William P. Warren

Published by the Geological  Survey of Ireland 1999

The Hill of Tara was the Seat of the High Kings of Ireland and its source to many of the Great Legends. The site has been an important one since the Neolithic (Stone Age) when a passage tomb was built. It had its heyday in the third century A.D. following the reign of Cormac Mac Airt.

The hill is cored by limestone bedrock which was streamlined by ice during the ice age. The bedrock once outcropped on the southern side of the hill but has since been removed by small scale quarrying, the scars of which can still be seen. The view from the hill is quite spectacular, showing the entire Boyne Valley and a very large part of the east midlands. The region dominated by the Hill of Tara covers some of the richest farmland in Ireland. It is an area underlain by a thick covering of till and glacial sands and gravels. The high hills of Slieve na Calliagh and Lloyd Hill can be seen to the northwest, the Mourne Mountains to the northeast, the Wicklow Mountains to the southeast and Slieve Bloom (in the distance) to the southwest.