WAEC Geography 2023 Theory — Question 13

Model answer

(a) Weathering is the gradual disintegration or decay of rocks in situ by chemical or mechanical processes. (b)(i) Frost action: Also called frost wedging or freeze-thaw weathering, this takes place in mid-latitude and temperate regions (and can also occur in mountainous regions) that are subject to freezing. Water that has entered cracks in rocks freezes and expands, exerting pressure on the rock; repeated freezing and thawing widens the cracks until the rock breaks apart. (ii) Exfoliation: This takes place in arid and semi-arid regions, where there is a big difference between daytime and night-time temperatures. As the rocks are heated during the daytime, the outer layers expand more than the interior; as they cool at night, the outer layers contract more than the interior. This continuous expansion and contraction produces stress on the outermost layer, which eventually causes the outer layer to peel/pull away from the rock in curved sheets/flakes.