St Ninian's Isle tombolo

The impressive tombolo at St Ninian's Isle is composed mostly of shell sand. Its symmetrical curving form is particularly striking when seen from above, a good viewpoint being the Ward of Scousburgh. For most of the year, the tombolo is dry, but it can sometimes be submerged in winter. It makes an excellent, often bracing, walk but there are plenty of sheltered corners for picnicking or sunbathing.

The tombolo offers access to St Ninian’s Isle, on which can be found the site of a chapel. Here, in 1958, a Lerwick schoolboy discovered a horde of Celtic silver, presumed to have been hidden by monks to keep it safe from Viking raiders. The original horde is kept in Edinburgh, but there are replicas in the Shetland Museum and Archives.

The tombolo is formed as waves break simultaneously along its length, resulting in beautifully symmetrical sweeping beaches facing north and south. The first known depiction of the tombolo is in a chart drawn around 1700. It formed as sea levels rose after the last ice-age but the forces that created it continue to work, making it the largest active sand tombolo in Britain. In winter sand is lost from the centre and builds up at the ends, while in summer the opposite occurs. During low tides it can be 70m wide, but during high spring tides the centre can become submerged. In the Northern Isles tombolos are usually formed from gravel, cobbles or boulders. St Ninian's tombolo is sand, though there is evidence for a gravel core beneath. Blown sand trapped by marram grass forms dunes at either end. They are more extensive to the east due to the dominance of westerly winds. Behind the dunes is machair - grassland with many wildflowers that benefit from the calcium in the sand.

St. Ninian's Isle is in the South Mainland and is signposted from the A970.

Sea-level rise