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Limestone pavements

• 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

• 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.

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.