Polar and sub-polar areas
high latitude areas are mainly affected by freeze-thaw
action. conditions may also occur on mountains in
temperate areas. degree of activity depends on the no of freeze-thaw cycles not the degree of frost, so rate of W in cold areas is
restricted. chemical action is restricted by the cold temps which slows rates of
chemical reactions. however, CO2 is more soluble at low temps, so carbonation can
occur. hydration may occur in waterlogged areas in summer.
Humid temperate areas
physical W is minimal; screes of upland areas may be relict features of periglacial
conditions in the last 2million years. similar the tors of areas such as Dartmoor may
have formed in past climates. all chemical and biological W processes are
significant due to the wet climate and the blanket of vegetation which causes
biological effects. pollution effects are important, especially in urban areas
Arid and semi-arid areas
rates of W are slowest here. illustrated by well-preserved archaeological remains.
chemical action slow due to lack of moisture. salt crystal growth, and physical
expansion and contraction due to large diurnal ranges of temperature may lead to
granular disintegration, block disintegration and exfoliation.
Humid tropical areas
most rapid W rates. regolith is up to 40m deep and rocks are observed to weather
significantly in decades. rates of chemical reaction are accelerated by the hot wet
conditions; in particular the increased ionisation of water increases the rate of
hydrolysis of silicates. increase rate of W at higher temps is known as the Van’t
Hoff’s law.
