Theory question 304
Underground Water and Karst(a) State three characteristics of limestone region. (b) Describe the formation of limestone pillar. (c) In what two ways is limestone important to man?
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(a) Little surface drainage (dry valleys, disappearing streams); swallow holes and sink holes; underground caves and streams; bare rocky surfaces with grikes and clints (limestone pavement); thin soils; springs at the base.
(b) Rain water containing carbon dioxide (weak carbonic acid) seeps through joints in the cave roof and dissolves calcium carbonate; drops hang from the roof and, as water evaporates and CO₂ escapes, calcite is deposited forming stalactites; drops falling on the floor build stalagmites; when a stalactite and stalagmite grow and join, a limestone pillar (column) is formed.
(c) Raw material for cement; building stone; flux in iron smelting; lime for agriculture and chemical industries; tourism (caves); groundwater sources.
Explain both stalactite and stalagmite growth.