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Raasay Fissures [Overview]

Isle of Raasay, Inverness-shire.

Generic reference to a series of deep fissures on Bein Na Leac and Dun Caan, Raasay. The coordinates given are for the centre of Loch Mna. There is no known cave at this location.

The fissures on Raasay are the result of massive tectonic action. They are located mainly in Jurassic sandstone up to 200 m thick interspersed with bands of Lias limestone varying from one to four metres in thickness.

There are at least five main groups of clefts and fissures on Raasay. These are the Screapadal, Loch Mna, Hallaig, Escarpment Top and Beinn Na Leac fissures. Those on Beinn Na Leac should be separated into the East Beinn group and those overlooking Rubha Na Leac. [Salvona, 2009]

The Raasay Site of Special Scientific Interest (SSSI) extends from South Fearns up the neast coast of Raasay to Screapadal. It Includes the whole of the coast between and covers also the fissure cave areas at Bein Na Leac and east of Loch Mna.

Raasay Site of Special Scientific Interest (SSSI) lies on the south-eastern coast of the Island of Raasay, which itself lies off the east coast of the Isle of Skye. The site encompasses a range of geological and biological features comprising an assemblage of upland habitats, woodland, vascular plants, freshwater lochs, Jurassic geology and more recent landslips. To the north of Hallaig a large area has been affected by mass movement, specifically rotational landslips, and remains highly unstable. It is a unique site with a geological configuration different from that of the nearby rotational slides on the Trotternish Ridge, which were formed by rotational failure of large blocks of rock but with no evidence of lavas being involved in the first two stages of land sliding. The east facing cliff at the rear of the landslips is about 70 metres high. At the base of the cliffs a 500m wide hollow is occupied by a loch which formed in the lee of the back-tilted landslide blocks. These slide blocks form a north-south trending ridge which is dissected by a labyrinth of open fissures of unknown depth. The fissures are up to 4m wide and opened in response to internal deformation of the slipped rock mass. The toe of the landslip is being actively eroded by the sea and movements have been recorded during the present [21st?] century. Bathymetric maps suggest that the Hallaig landslide complex extends offshore, into an area that includes the UK's deepest (300m) submarine channel. The Hallaig landslip is the only UK mass movement site with good evidence for recent tectonic activity, which is interpreted as movement generated along fault lines and slumping on the steep submarine slopes. [Raasay SSSSI Citation]

Alternative Names: None recorded.

Notes: The island of Raasay, as well as affording a variety of scenic walks, offers a wide scope for underground exploration. This ranges from a souterrain to sea caves and an extensive ironstone/limestone mine as well as some of the deepest fissure caves in Scotland which may yield the most extensive systems of this type. [Salvona, 2009]