Ingleton: Swilla Glen

© Craven & Pendle Geological Society

Information Boards

Entrance to the Waterfall Walk

Limestone

: Tracing the Anticline :
Carboniferous Great Scar Limestone

Tufa

: Tufa Screen :

The Ingleton Glens are particularly important to the geologist with the key feature being the exposure of the Lower Palaeozoic basement rocks that lie below the Carboniferous Great Scar Limestone. As you can see from the photograph (left) the paths are well maintained.

The car park is built on an alluvial flat that covers Coal Measure sandstones on the downthrow side of the South Craven Fault.

On entry to Swilla Glen you will have crossed the South Craven Fault. The only evidence for this is a wet ground to the left of the path.

The initial outcrop of limestone in Swilla Glen dips gently downstream forming the southern limb of an anticline. As you walk along the valley you should be able to see the limestone begin to exhibit a much more shallower dip. This indicates that you have (or are about to) reach the crest of the anticline. Later along the path the limestone will begin to dip gently to the north.

Limestone is made of almost soluble calcium carbonate. It’s solubility is greatly increased by the presence of carbon dioxide (as found in rain water). The interaction of rain water and limestone leads to the formation of soluble calcium bicarbonate. When the carbon dioxide is later released from solution, (typically in flowing water and spray over a waterfall) the carbonate is reformed and deposited as tufa.

This is a typical feature found throughout the Yorkshire Dales limestone country. It is to be found in Malham at Janet's Foss.

The photo to the left shows the tufa screen in Swilla Glen. For the chemists amongst you this is chemcal equation that defines the process.