Navan to Bective
The Boyne Valley in the Ice Age
Robert T. Meehan & William P. Warren
The Geological Survey of Ireland 1999.
Take the Trim Road, the R161, out of Navan. It crosses a flat till plane as far as Balreask where Teach na Teamhrach is. This flat area underlain by till was deposited beneath the ice which crossed the area around 20,000 years ago. Till is sediment deposited by or from glacier ice; unsorted and unstratified and generally tightly packed. Passing Balsoon Demesne the road crosses a meltwater channel which has been incised into the underlying till by meltwater during deglaciation. Just past this meltwater channel, 7 km south of Navan, turn left towards Bective Abbey. The sign is for Kilmessan.
Bective Abbey is a substantial remains of the second Cistercian monastery founded in Ireland in 1147. The remains are chiefly of a smaller 15th century abbey built on the site of the 12th and 13th century Gothic complex.
The Boyne channel is quite wide at this point and has only one terrace on its northern side. The abbey is built on this terrace which provided an excellent level site, close to, but above the level of the river and its fertile flood plain and therefore dry and safe from floods when the river overflows its banks. The terrace is composed of glaciofluvial gravels which were laid down during deglaciation by the meltwater flowing through this part of the Boyne System from the Midlands. Glaciofluvial means of or pertaining to rivers made up of meltwater from glaciers or ice sheets.
The modern floodplain is relatively wide close to the Abbey and is generally sandy in texture, reflecting in its well drained appearance. On the southern side of the river a steep escarpment has formed where the river has cut into the bedrock which is quite close to the surface at this point. An escarpment is a steep slope or cliff on one side of a hill or ridge with sides of varying slope angle. In fact, on the southern side of Bective Bridge, 200 metres from the road a steep cliff has been cut into a well bedded limestone outcrop. Behind this outcrop much of the area around Balsoon and Balgeeth is dominated by thick glaciofluvial gravels and sands which were deposited at the margin of the ice as it retreated across the area during deglaciation.