2.2a+-+Weathering

__From the syllabus__
Candidates should be able to:
 * Recognize that weathering involves the breakdown of rock in situ and, as such, should be distinguished from erosion.
 * Describe what is meant by different types of weathering – physical/mechanical (freeze-thaw action, exfoliation), chemical (carbonation, oxidation) and biological.
 * Explain the main factors influencing the type and rate of weathering – climate and rock features (mineral composition, grain size of the rock, presence of lines of weakness). The influence of climate on the rate of weathering could be illustrated with reference to simple explanation as to why weathering is more rapid in humid tropical regions of the world than in temperate regions.
 * Demonstrate an understanding that the natural environment presents hazards and offers opportunities for human activities. (NB: In the case of weathering, an example of this is how the process is responsible for the creation of soils)


 * Physical Weathering:** the disintegration of rock into smaller pieces without any chemical change in the rock; this is most likely in areas of bare rock where there is no vegetation to protect the rock from extremes of weather e.g. freeze-thaw and exfoliation (or onion weathering).
 * Freeze-Thaw Weathering:** also called frost-shattering as it occurs in cold climates when temperatures are often around freezing point and where exposed rocks contain many cracks. Water enters the cracks during the warmer day and freezes during the colder night. As the water turns into ice it expands and exerts pressure on the surrounding rock, causing pieces to break off.
 * Scree:** a slope of loose, large angular rocks broken away from the mountainside by freeze-thaw weathering.
 * Weathering:** the break-down or decomposition of rock by biological, physical or chemical processes.

[|Weathering mind map.pdf]