weathering Flashcards
what is weathering?
the break down of rocks over time
what are the three types of weathering?
mechanical (freeze-thaw, salt crystallisation, wetting and drying)
chemical (carbonation, oxidation, solution)
biological (plant roots, birds, seaweed acid, decaying vegetation)
what are the three types of mechanical weathering?
freeze-thaw
salt crystallisation
wetting and drying
what are the three types of chemical weathering?
carbonation
oxidation
solution
what are the four types of biological weathering?
plant roots
birds
seaweed acids
decaying vegetation
explain what is freeze-thaw weathering?
water enters cracks
freezes
water expands by around 10% in volume
increasing pressure on rock
cracks develop
cracks grow and cliff grows weak
more vulnerable to other processes of erosion
explain what is salt crystallisation weathering?
seawater evaporates
salt left behind
crystals grow over time
exert pressure on rock
forcing cracks to widen
explain what is wetting and drying weathering?
clay expands when wet
contract when dry
continues over time
causes rocks and cliffs to breakup
explain what is carbonation weathering?
rainwater absorbs CO2 from the air
weak carbonic acid
reacts with calcium carbonate in rocks
form calcium bicarbonate
explain what is oxidation weathering?
minerals are exposed to air because of cracks
mineral becomes oxidised
increases its volume
causing rock to crumble
explain what is solution weathering?
when rock minerals are dissolved
explain what is plant root weathering?
roots of plants grow into cracks
exert pressure
splitting rock
explain what is bird weathering?
eg puffins dig burrows into cliffs
weakening them
making erosion more likely
explain what is seaweed acid weathering?
some seaweed contain sulphuric acid
if this hits rocks or cliffs
acid will dissolve some of the rocks minerals
explain what is decaying vegetation weathering?
water that flows through decaying vegetation
and then over coastal areas
will be acidic
thus causing chemical weathering
what can effect the prominence of weathering?
the temperature and climate
colder — mechanical more common
warmer — chemical more common
