Limestone pavement

Malham Cove

A limestone pavement is a flat expanse of exposed limestone formed by a combination of chemical weathering and erosion. Limestone pavements in England, Wales and Ireland are mainly formed on Carboniferous limestone (they are mainly on older limestones in Scotland) and we focus here on those in Yorkshire.

Ingleborough

Grykes and clints

Grykes are the blocks of limestone that form the pavement. They are chemically weathered so that their surface is covered by a series of pits and hollows (called karren).

Clints (sometimes called by their German name, flachkarren) are fissures separating the grykes in a limestone pavement. They may be well over a metre in depth, and formed when the joints in the limestone were widened by chemical weathering.

How do limestone pavements form?

  1. During the last ice age, much of Britain was covered by ice sheets and glaciers. During this time the soil and weaker surface rocks of the Pennines were scoured away, leaving broad expanses of exposed limestone such as those at Ingleborough, Malham and Scales Moor, Yorkshire.
  2. With the retreat of the glaciers, moraine material was left behind and a forest eventually established itself. Rain water that percolated through the soils became acidic and gradually dissolved the limestone surface.
  3. Under the soil, rain water picked out the joints in the limestone and gradually widened them by dissolving the rock. This created deep fissures called grykes. The blocks of limestone (the clints) were also attacked by the rain and small holes and gulleys formed on their surface, which are called karren.
  4. The ice finally retreated about 12 000 years ago. The soil on the top of the limestone pavement was eroded, washed down into the grykes and removed altogether by the drainage system. This erosion has increased during the past few thousand years, first by forest clearance and later by agricultural pursuits.
  5. The exposed limestone pavements have been constantly weathered chemically, which further widens the grykes and deepens the karren.