Saturday, January 21, 2012

LIMESTONE

What is Limestone?
Limestone is an organic, sedimentary rock. This means it was formed from the remains of tiny shells and micro-skeletons deposited on the sea bed. They were compressed to form solid rock. Limestone is made up of calcium carbonate and reacts with diluted hydrochloric acid. Limestone is formed in layers - called bedding planes. These bedding planes contain vertical cracks called joints. Joints and bedding planes make the rock permeable.

Stalagmites and stalactites



Erosion of Limestone
Weathering is the breakdown of rock by physical, chemical or biological processes. Limestone areas are weathered when rainwater, which contains a weak carbonic acid, reacts with limestone. When it rains limestone is dissolved. Rainwater erodes the joints and bedding planes. In doing this Karst scenery is created.

Limestone (Karst) Features - overview




Limestone (Karst) Features - above ground
Karst scenery includes:
  • Swallow hole - An exposed limestone joint down which a surface river 'disappears'.
  • Clints and grykes - Rainwater flowing over an impermeable surface will, on reaching (permeable) limestone, be able to dissolve the joints into grooves called grykes, leaving blocks or clumps of limestone in between called clints
  • Limestone pavements - Exposed clints and grykes. The video below shows a limestone pavement at Malham, Yorkshire Dales.
video



Limestone (Karst) Features - below ground
  • Stalactite - Water dripping from the roofs of caves leave behind microscopic particles of calcium carbonate. These build up as icicle shaped stalactites.
  • Stalagmite - Drips splashing onto the floor of caves leave behind microscopic particles of calcium carbonate. These build up on the floor of caves.

Limestone and recreation
Limestone areas are popular due to the range of leisure activities that people can participate in. These include walking, pot holing, climbing and abseiling


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