Physical and Chemical Weathering of Rocks

Wednesday, April 8, 2020

Weathering of rocks is a physical or chemical change that changes the characteristics of rock on earth 
There are two major types of weathering.

Chemical weathering changes which involve rocks being changed into new substances or new minerals chemically.

chemical weathering

Physical weathering involves breaking rocks into smaller fragments caused by environmental factors.


Three major types of physical weathering
  • Abrasion
  • Frost Wedging
  • Thermal stress
Abrasion is a mechanical scraping and can be caused by the following factors.
  • Wind
  • Water /waves
  • Glaciers
  • Gravity
  • Plants/animals
Frost wedging occurs as water expanding as it freezes causing the rock to break apart.

Thermal stress results when heat and changes in temperature cause rock to expand and contract and this can break the rock apart. 
Chemical changes occur when a chemical reaction creates a new substance.

Oxidation occurs as oxygen o2 combines with iron in rock and creates new compounds.

When iron reacts with oxygen, it forms iron oxide commonly called rust, which weakens the rock.


Hydrolysis occurs when hydrogen reacts and creates a new substance.
For example, Hydrolysis causes feldspar to turn into clay.

Carbonation is the process of mixing water with carbon dioxide to make carbonic acid. This acid then breaks down and weakens rocks. Caves may be formed by carbonation dissolving limestone. Rainwater picks up carbon dioxide from the air and as it percolates through the soil slowly dissolves out the limestone.

Helpful Resources on weathering

Weathering Playlist

Weathering Crossword Puzzle


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