Upland limestone - surface features

Limestone pavements

Features of Limestone LandscapeThe formation of a limestone pavement

  • During periods of glaciation, glacial abrasion scraped away the topsoil to expose the bare rock underneath.
  • As limestone is a permeable rock, water is able to seep down through the cracks and into the rock.
  • Rainwater is a weak carbonic acid which reacts with the limestone as it passes through the rock, dissolving the stone while enlarging joints and bedding planes.
  • On the surface the chemical weathering widens and deepens cracks to form grykes.
  • This leaves exposed blocks of limestone called clints and the resulting pattern of blocky rock is called a limestone pavement, eg Malham Cove.

Potholes/swallow holes

Gaping Gill, Ingleborough, North Yorkshire
Gaping Gill, Ingleborough, North Yorkshire

  • Surface water and rain do not flow far on exposed limestone as they rapidly infiltrate into the rock and soil.
  • Where a joint or intersection of joints has been greatly weathered or dissolved, water can pass down through the limestone.
  • A stream travelling over an impermeable rock will very quickly disappear when it has to travel over limestone.
  • These swallow holes can be many metres deep leading down to a series of underground features.
  • An example of a swallow hole in the Yorkshire Dales is Gaping Gill.

Upland limestone drainage feature

Intermittent drainage

  • When a stream disappears through the permeable limestone, it travels underground through a complex series of caves.
  • It eventually works its way down to a level of impermeable rock or until it reaches the top of the water table.
  • The stream flows over the impermeable rock until it reaches the surface as a spring.
  • Where limestone lies on top of impermeable rock along a valley there can be several springs formed along the intersection of the two rocks. This is called a spring line.
  • An example of a disappearing/reappearing stream in the Yorkshire Dales is Fell Beck.