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Caves and karst in Scotland

Karst may be defined as a distinctive landscape created by erosion of a soluble rock where the topography and landforms are a consequence of efficient underground drainage.

Going underground

The characteristic features of karst therefore include disrupted surface drainage (e.g. streams that vanish underground), dry valleys and caves. Limestone, and to a lesser extent dolomite (magnesium-rich limestone) are the most common rocks that are sufficiently soluble in natural surface waters to form karst.

Karst is a very minor component of Scotland's landscape. Only in Assynt do solution features (in Durness dolomite) occur on a scale where they create distinctive landforms. These include karst and caves in the Trail gill and Allt nan Uamh valleys, and caves near Knockan and on the Achmore plateau.

Pre-glacial karst features were largely removed by Scotland's last glaciers; so karst features mostly post-date the end of the glaciation, around 11,500 years ago. However, many cave passages pre-date the last glaciation, which peaked around 22,000 years ago.

The Durness dolomite extends both north and south of Assynt from Smoo Cave on the north coast, to small caves near Loch Slapin on Skye and others around Kishorn. There are also caves and limestone pavements in Glen Creran.

Thin Jurassic limestones contain small caves around Broadford on Skye, and also the cave passages of Uamh nan Breagaire at Applecross. Small caves also occur in Dalradian marble (heated and compressed limestone) near Schiehallion, and at Uamh nan Uachdar in the Grampians south of Glen Spean. There are no records of caves in the limestones of the Midland valley.

Wave action

Some caves are cut into rocks that are neither limestone or dolomite. These features lie along ancient raised shorelines and were cut largely by wave action when they lay at sea-level. In many cases this was probably shortly after the last period of glaciation (ice cover) in Scotland, during and just after the ice melt. Well-known examples include Fingal's Cave on Staffa, cut into a ~65 million year-old columnar-jointed lava flow; and King's Cave on Arran, cut into ~250 million year-old New Red Sandstones.

Last updated on Monday 14th December 2015 at 09:45 AM. Click here to comment on this page