Glen of the Downs

Glen of the Downs

The Glen of the Downs is the largest example in Ireland of a meltwater channel. It was formed by melting water draining from beneath the edge of the Irish Sea ice sheet about 15,000 years ago. Later the ice thawed to form large glacial lakes around Enniskerry and the glen formed an outlet channel to the south. Native woodland now covers the valley slopes. (Richard Nairn)

copyright R. Nairn

Glen of the Downs
copyright R. Nairn

Glen of the Downs

The Glen of the Downs is the largest example in Ireland of a meltwater channel. It was formed by melting water draining from beneath the edge of the Irish Sea ice sheet about 15,000 years ago. Later the ice thawed to form large glacial lakes around Enniskerry and the glen formed an outlet channel to the south. Native woodland now covers the valley slopes. (Richard Nairn)

copyright R. Nairn

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4. Glen of the Downs

Glacial valley, woodland, stream

Map reference: T2611 Nearest town: Delgany

Landscape: This deep glacial valley formed as a meltwater channel near the margin of an ice sheet. The water may have been forced out under pressure with the great weight of ice above. The rocks are ancient Cambrian quartzites of the Bray group, similar to those on the Great Sugarloaf mountain to the north-west.The valley sides rise over 100 metres (300 feet) from the road which runs alongside a small stream. The valley is filled with broadleaved woodland, although there are some conifer plantations at the southern end and on higher ground to the east. In Victorian times the view from the rectangular room of the nearby Bellevue House was described as 'a scene of luxurious softness, combined with grandeur and significance'.

Habitats: Most of the woodland on the steeper slopes is oak with some birch, cherry and rowan. The understorey is composed of holly, honeysuckle and bramble in the more open areas. The luxuriant ground flora includes woodrush, wood sage, ivy and bilberry. On the valley floor to the east of the road a small stream flows south towards Delgany. This is surrounded by ash and hazel woodland although there is a lot of introduced laurel. Wild garlic is especially abundant on the damp soils here with wood anemone, wood sorrel and lesser celandine in spring. There is a fine stand of planted beech trees to the west of the road.They cast a dense shade in summer, which reduces the ground flora but provides good conditions for fungi in the autumn.