Weathering Flashcards
(20 cards)
what is weathering
the breakdown of rock at/near ground surface when exposed to air, moisture or organic matter
where does weathering happen
in situ (in place)
how is weathering different to erosion
weathering is where rock is changed/broken in place , this becomes erosion if the weathered rock moves
what is physical weathering
this is the breaking down of rocks or breaking rocks apart without changing their chemical composition
what is chemical weathering
decomposition of rock caused by acidic reactions
where does chemical weathering usually happen
in wet and hot conditions
is weathering a marine or subaerial process and why
usually are subaerial processes because they usually happen on the cliff face or cliff top
what are 4 main types of physical weathering
freeze thaw, salt crystallisation , wetting and drying(slaking) ,biological weathering
how does freeze thaw weathering work
when water gets into cracks in rocks and freezes causing it to expand , then when it thaws it contracts , this puts pressure on surrounding rock causing it to crack and break
when is freeze thaw most effective
during very cold winters
what is salt crystallisation
this is where salt crystals deposit into cracks in rock/cliffs and over time the crystals build up , this puts pressure on surrounding rock causing it to crack
what is wetting and drying
this affects rocks made out of clay mostly as when the material expands when it’s wet and contracts when it’s dry , this leads to cracks in the clay rock
what does wetting and drying usually lead to
salt crystallisation and freeze thaw
what is an example of biological weathering
where the roots of growing plants grow deep into cracks in rocks , causing the cracks to get bigger which means rock segments can break away
what are 3 main types of chemical weathering
oxidation , carbonation and hydrolysis
what is oxidation weathering
this is where oxygen dissolved in sea water and therefore reacts with it, which causes rocks and cliffs to disintegrate
what type of rock does oxidation affect most and what does it cause
iron rich rocks , and causes a yellow/brown rusty colour
what is carbonation weathering
this is where CO2 dissolved in rain (acidic rain) creates a weak carbonic acid
the carbonic acid reacts with the calcium carbonate in limestone to form calcium bicarbonate
calcium bicarbonate is very soluble so it’s easily dissolved , this gradually will weather away the rock
what is hydrolysis
this is where acidic water reacts with the minerals in rocks/cliffs, which makes weak clays and soluble salts
these are weak materials so make the rock weaker so it’s more likely to break apart
what type of rock does hydrolysis affect the most
granite
