erosion surfaces

Langwell Forest

deep weathering

Cairngorm tors

 

The tors of Smean

Image by Alan Moar

 

 

 

 

 

 

 

 

 

The tors of Smean

 

 

 

 

 

 

 

 

 

 

Glacially-transported conglomerate block on Smean

Tors

Definition: a small rock hill produced by differential weathering and erosion

Conglomerate tors are a striking element of the scenery of the inselbergs of southern Caithness. They are amongst the most impressive in Britain, with the largest summit tors rising over 10 m above their surroundings.

The tors are developed in Devonian conglomerate. The tors present an irregular detail in outline but the influence of dip is strong. On Morven, a line of crags surmounted by tors relates to a particularly tough bed of conglomerate. The tors are products of differential weathering and erosion, resistant rock knobs which have merged due to local contrasts in the jointing, bedding and bed thickness in the conglomerate. The surfaces appear fragile, with cobbles of quartzite loosening from the sand matrix, but recent cosmogenic age determinations indicate exposure over timescales of hundreds of thousands of years.

The tors at lower elevations and at exposed sites have been modified by the passage of ice, losing summit blocks. Crn Mr on Smean, for example, has been reduced to a streamlined rock ridge. This demonstrates that the tors predate at least the last glaciation. Moreover, the subdued forms of the summit tors on Morven indicate that glacier ice has flowed slowly across this hill summit.