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Moving mountains on Clare Island

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Clare Island, Landslide
Earth Move Knockmore landslide on Clare Island. Grianghraf: Cormac Ó Cionnaith

Moving mountains on Clare Island

Cormac Ó Cionnaith


DURING the stormy weather before Christmas, a large landslide occurred on Clare Island in Clew Bay as tonnes of peat and rocks slid down Knockmore Mountain. Fortunately, it did not happen in the vicinity of the houses. Had it done so, there could have been a repeat of the damage inflicted on Dooncarton Mountain near Pullathomas on the night of September 13, 2003, when over 80mm of rain fell in 90 minutes.
It was not the first landslide on Clare Island, as one happened on the north side of the island six years ago, while a major one also occurred in the 1940s.
Luckily, there was no damage done on this occasion, other than a blockage to the source that supplies water to the reservoir. Being the main water supplier on the island, it could have been a dry Christmas but for the timely intervention and good work two days before the great feast by Mayo County Council workers.
Clare Island, situated three miles from the mainland at Roonagh harbour, is about 95% mountainous and its neighbours are Caher and Inishturk to the southwest, with Achill some four miles to the north. Knockmore faces south and rises 462 metres above the Atlantic Ocean.
There is concern that a landslide may occur again which might cause extensive damage or even lead to loss of life, and there is a desire among locals to see some preventative action taken, like the installation of kinetic landslide barriers.
Some weeks after Christmas, about 15 miles to the south east of Clare Island, a similar landslide occurred near Leenane. One of the many peaks near Ben Gorm (700m), which is part of the Mweelrea mountain range, lost thousands of tonnes of its cover and the debris came to rest at the back windows of a local house, while more silt and peat made its way across the main road.
This mountain is well known to people visiting the famed Aasleigh Falls, where some of the most dramatic scenes from the film ‘The Field’ were shot, and a short distance from the Western Way walking route. Like Knockmore on Clare Island, this mountain has a similar orientation and the landslide occurred at about the same elevation, with evidence of past landfalls. Fresh markings nearby would indicate that more movement could occur in the not-too-distant future.
Various theories are being put forward as to why the landslides took place, the most common being the over-grazing by sheep. Some soil engineers will tell you that the long spell of fine weather experienced last summer in particular caused the peat to crack open due to its delicate state, which was punctured by the march of tiny hoofs. When the severe rains came in November and December, the land expanded, burst apart and, without the normal heather to keep it intact, the avalanche resulted.