Weathering process is considered to be one of the important topics as per UPSC exam point of view. This weathering process is further categorised into three types: physical, chemical and biological weathering. By keeping all these things in mind Testbook has prepared best quantility notes in which all important topics are covered in a very easy language. These notes are important for other competitive exams also like State civil service and many more.

Weathering – Introduction:

• The process of action of elements of weather and climate over the Earth material is called the weathering process. 
• The disintegration of rocks can be of various types like mechanical disintegration and chemical disintegration. All this disintegration can occur because of elements of weather and climate. During the weathering process of rock some minerals are removed through chemical/ physical leaching by groundwater because of this concentration of remaining minerals increases. 
• Weathering process can be categorized into three types: physical, chemical and biological.Thus in the below notes we will study types of weathering,Biological weathering,Chemical weathering,Physical or Mechanical Weathering to understand the whole physical weathering phenomenon.

Physical Weathering (UPSC Geography) NCERT Notes: Download PDF Here

Physical Weathering:

• Physical weathering is also known as mechanical weathering. This weathering depends on the kind of applied forces. 
• Force which is applied during physical weathering are: gravitational forces such as overburden pressure, load, and shearing stress, expansion force this force occurs due to temperature changes, crystal growth or animal activity, water pressure which is controlled by wetting and drying cycles.
• One of the major causes of physical or mechanical weathering is thermal expansion and pressure.
  

Check out NCERT notes on Weathering here.

Some Examples Of Physical Weathering Mechanisms 

Below we will discussing physical weathering mechanism in details

Unloading and Expansion:

• Process by which removal of overlying rock loads occur because of continuous erosion as it causes release of vertical pressure. 
• Because of this there occurs an expansion of the upper layer of remaining rocks which occur due to disintegration of rocks. 
• There occurs a development of fractures which is roughly parallel to the ground surface.
• The area has a curved ground surface from which massive sheets or exfoliated slabs are produced from arched fractures. 
• Exfoliation sheets are formed by the expansion because release of pressure and unloading may measure hundreds or even thousands of metres in horizontal extent. 
• Examples of exfoliated domes are: big, smooth, rounded domes. 

Temperature Changes and Expansion:

• With increase in temperature there occurs expansion of  minerals and with fall in temperature it pushes against its neighbor because of this there occurs corresponding contraction. 
• Because of the differential heating process and the expansion and contraction process of the surface layer and their subsequent exfoliation from the surface which result in the conversion of smooth rounded surfaces into rocks. 
• Rocks which are formed from such exfoliation are granites, smooth surfaced and rounded small to big boulders called tors. 

You can check NCERT notes on Factors controlling temperature distribution here.

Freezing, Thawing and Frost Wedging:

• Frost weathering is caused by a freezing cycle and thawing i.e. melting of ice or snow because of warmer weather. 
• Its effectiveness is maximum at the high elevations in mid-latitude where there is often repetition in freezing and melting. 
• Rapid freezing process of water often leads to its sudden expansion and high pressure. This expansion process shows its effects on joints, cracks, and small intergranular fractures to become wider and wider till the rock breaks apart.

You might also like: NCERT notes on Biological Weathering

Salt Weathering:

• There occurs expansion in salt in rock because of thermal action, hydration and crystallization.
• These salt may be calcium, sodium, magnesium, potassium and barium as all of them have a tendency to expand. 
• This expansion process in salt depends on the temperature and their thermal properties. 
• This expansion process of salt is favoured by high temperature ranges between 30-500C of surface temperatures in desert. 
• Most effective salt weathering process is salt crystallization. It is seen in areas of alternate wetting and drying conditions. 

Also read: Classification of Soil in India for UPSC here

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