(a) List: (i) three factors that influence weathering; (ii) two effects of landslides.
(b) Describe the following processes of weathering: (i) exfoliation; (ii) frost action.
(a)(i) Factors that Influence Weathering:- -Climate -Rock structure-Vegetation -Topography/relief - Time -Animals (ii) Effects of Landslide:--Loss of human life -Debris can block streams, or rivers to form a temporal lake Destruction of properties -Displacement of people - Silting of rivers and lakes -Destruction of settlements-Destruction of farmlands-Renders an area vulnerable to soil erosion -The debris can block highways and railway lines.
(b) Description of Processes of Weathering:- (i) Exfoliation:- A form of mechanical or physical weathering-Takes place in arid and semi-arid regions -there is a big difference between daytime and nighttime temperatures -As the rocks are heated in the daytime, the outer layers expand - expansion is more on the surface than in the interior - As it cools in the night it contracts - Contraction is more on the surface than in the interior - Continuous expansion and contraction produce stress on the outermost layer- the outer layer pulls away -The outer layer peels off from the cooler interior -in a process called exfoliation - the peeling resembles that of onion peels-the boulder left behind after the peeling is called exfoliation domes - Could also be as a result of unloading of over-burden or pressure release -This occurs mainly in the Tropics -Plutonic rocks are under pressure-- the rocks are compressed by overburden -When exposed by erosion- the pressure on them is released -The rocks expand slightly in volume - the expansion causes the surtace layer to crack and peel off-The rock peels are thin and parallel to the rock surface-The onion-like peels called "sheet structire" -exfoliation dome is left behind.
(ii) Frost action: A form of mechanical or physical weathering -Also called frost wedging-Takes place in mid-latitude and temperate regions-Can also occur in mountainous regions - such areas are subject to freezing -Cracks and crevices need to develop on rocks -Water in the form of rainfall or snow seeps into the cracks-the water freezes -Water increases in size when it freezes-Water increases by 10% when frozen -The frozen water exerts pressure on the walls of the rock -The pressure widens the cracks -In the day or summer, ice melts and Water seeps deeper into the widened cracks -the process of freeze and thaw continues -This eventually lead to the shattering of rocks into blocks in a process called frost action -Angular rock fragments accumulate -Called talus and Screes.
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