18/05/2021
Another beautiful natural wonder to see on the NC500 in the northern highlands , when staying at Greenland house
Smoo Cave is a large combined sea cave and freshwater cave in Durness in Sutherland. The cave name is thought to originate from the Norse 'smjugg' or 'smuga', meaning a hole or hiding-place.
The cave is unique within the in that the first chamber has been formed by the action of the sea, whereas the inner chambers are freshwater passages, formed from rainwater dissolving the carbonate dolomites. Partway through the cave the waters of Allt Smoo also drop in as a 20 metres (66 ft) high waterfall.
The cave is composed of three main sections: a large sea cave entrance chamber, a waterfall chamber and a short freshwater passage which leads to a terminal sump chamber with some flowstone formations at the rear.
The cave entrance and main chamber have been considerably enlarged by sea action to approximately 40 metres (130 ft) wide and 15 metres (49 ft) high, the largest sea cave entrance in Britain.
The entrance is located at the end of a 600 metres (660 yd) long tidal gorge (Geodha Smoo) which was once part of the cave, now collapsed. Several remnant pillars can be seen along the eastern side of the Geodh along with a large section of the previous roof which has been partly buried by the grassy slope . The sea rarely enters the sea cave nowadays (only during spring tides) as the area has undergone isostatic uplift.
The present-day cave is 83 metres (272 ft) long up to the terminal sump at the rear of the third chamber / passage. The cave travels further however as an active stream of notable size resurges here at all times. Previous dye-testing has linked an underwater passage to an initial sink point in the Allt Smoo stream about 100 metres (330 ft) upstream from the main waterfall, implying that the cave system is at least twice as long as once thought.
Cave divers from the Grampian Speleological Group have dived this sump for a distance of about 40 metres (130 ft), although large volumes of silt and peat in the water have prevented further exploration. It is worth noting that the main waterfall is often dry and will only become active once this upstream sink overflows.
Archaeological investigations have turned up Neolithic, Norse and Iron Age artifacts, and it is thought that usage may extend back to the Mesolithic age.
Tours of the cave operate during the summer, taking visitors to the inner chamber by boat.