Theory question 206
Underground Water and Karst(a) Write explanatory notes on the following: (i) springs; (ii) caverns. (b) Highlight four ways in which limestone is important to man.
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(a)(i) A spring is a natural outflow of underground water at the surface; it forms where the water table meets the surface, where permeable rock rests on impermeable rock, along faults, or in limestone areas where underground streams come out (resurgent/vauclusian springs). Types: valley, scarp-foot, dyke, fault springs, hot springs.
(ii) Caverns are large underground caves in limestone formed by carbonation: rainwater with carbon dioxide dissolves the rock along joints and bedding planes; underground streams widen them; may contain stalactites, stalagmites and pillars; e.g. Carlsbad Caverns (USA).
(b) Raw material for cement (Ewekoro, Nkalagu, Obajana); building stone; making lime for agriculture to reduce soil acidity; flux in iron and steel making; chalk; glass, paper and chemical industries; tourist attractions (caves); limestone areas good for grazing; water from springs.
Explain how each feature forms.