Theory question 104
Rocks and Soil Formation(a) Enumerate four economic importance of rocks: (i) to man; (ii) in agriculture.
(b) State two characteristics of each of the following: (i) igneous rock; (ii) metamorphic rock.
(c) Describe the mode of formation of sedimentary rocks.
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(a)(i) To man (any four): building materials (granite, marble, sandstone); road construction (gravel, laterite); source of minerals and metals; fuels (coal); cement from limestone; ornaments and monuments; tourism
(ii) In agriculture (any four): parent material of soil; source of plant nutrients; lime from limestone/chalk; rock phosphate fertilizer; gypsum; materials for farm buildings and roads; water storage (aquifers)
(b)(i) Igneous (any two): formed from cooled magma; crystalline; hard and compact; no layers or fossils
(ii) Metamorphic (any two): formed from other rocks by heat and pressure; hard, often banded or foliated; recrystallised; no fossils
(c) Rocks are weathered into particles which are carried by water, wind or ice and deposited in layers in seas, lakes and rivers; remains of plants and animals may also accumulate; over long periods the layers are compacted by the weight above and cemented together, forming layered (stratified) rocks such as sandstone, shale and limestone
Four uses each for man and agriculture.