Table of Contents
Although climate is the main factor affecting weathering, other factors also play a significant role in determining the rate and type of weathering.
Rocks with already made cracks are easily attacked by weathering agents, e.g water in cracks or by humic acids.
The mineral composition of rock determines the type and rate of weathering,for example rocks such as limestone are susceptible to carbonation because of their calcium carbonate composition whereas rocks such as granite are made up of minerals that react at different rates; quartz is more resistant than feldspar.
Light coloured rocks such as granite and rhyolite and minerals such as quartz and micas reflect sunlight and are poor conductors of heat. As such insolation only operates a few inches away from the surface (the outer layers of rocks).
The hardness of rock can determine what weathering can take place and how fast. For example hard resistant rocks such as granite(quartz) and gabbro need episodes of repeated expansion and contraction or freezing and cooling before they can start to crack.
In addition., quartz in granite is very resistant to chemical weathering. Conversley soft rocks such as limestone and chalk easily gets weathered and washed away in solution.
Vegetation shelters rock from agents of weathering making weathering such as insolation impossible and or providing humic acids from decayed vegetation which promotes and accelerates hummification (chelation) and carbonation.
In addition,vegetation can weather rocks through plant root action.
On steep slopes weathered debris can be removed by mass wasting exposing the rocks to more agents of weathering eg insolation.
Conversely, on flat gentle slopes weathered debris or vegetation may cover the rock from futher weathering.
In addition, gentle slopes promote infiltration which supply abundant moisture to the soil favouring weathering such as hydrolysis or oxidation.
Sun facing slopes are more prone to agents of weathering such as insolation promoting Insolation weathering or speeding up chemical reactions.
Conversely sun backing slopes are sheltered from insolation promoting weathering such as freeze thaw.
(North facing slopes receive high insolation in the Southern Hemisphere whereas in the Northern Hemisphere,south facing slopes receive high insolation)
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