Knock Dhu and Sallagh Braes ASSI

Knock Dhu and Sallagh Braes has been declared an ASSI because of the variety of earth science features, habitats and species that the site supports.

The large, semi-circular, cliff at Sallagh Braes is notable for huge landslips which occurred in the past as a result of the geology and the glacial history of the site. The cliffs are composed of harder rocks (basalt and chalk) underlain by softer rocks (particularly Jurassic mudstone), making them very unstable. It is thought that this instability was exacerbated at the end of the last Ice Age, as a result of ice withdrawal. When the ice receded, the unsupported steep cliffs, underlain by the softer rocks, were prone to huge landslips which are evident today.

The complex topography of cliffs, ravines and scree and the combination of basalt and limestone rock provides a wide variety of habitats at Knock Dhu and Sallagh Braes, making it one of the most important sites in Northern Ireland for mosses. A number of rare species are found on the site including Fringed Extinguisher-moss, Oeder’s Apple-moss and Downy Veilwort. Of particular note is the presence of a small population of Brown Screw-moss which was recently found on limestone cliffs at Sallagh Braes. This species was thought to be extinct in Ireland, having not been recorded since 1962.