Physical/Mechanical Weathering

Physical Breakdown of Rocks

What is Physical Weathering

  • Over time, constant exposure to forces, such as wind, water, cold and heat, takes their toll on rocks.
  • These forces lead to physical weathering which is defined as the physical breakdown of rock without changing the chemical composition of the rock, by environmental factors

Process of Physical Weathering

  • A physical process that is always happening, it's just occurring slower than our senses can detect.
  • There are many different procedures that are part of physical weathering, they include;
  • Thermal Expansion
  • Frost shattering
  • Plant activity
  • Abrasion

Thermal Expansion

  • Thermal expansion is the ability of fluctuating temperatures to affect rocks, which is the the tendency for the minerals, and these minerals to expand and contract based on temperature, such as day and night temperatures
  • An example is Grus which is the accumulation of coarse-grained and loose fragments left behind. Which is the direct result of the physical breakdown of rocks

Frost Shattering

  • A type of mechanical weathering where we see the breakdown of rock due to the expansion of ice
  • This occurs between the crevices of rocks
  • During the day when temps are warm, water trickles into the rock, then at night the temp drops the water freezes and expands
  • As this continues cracks within the rocks widen and eventually shatter parts of the rock
  • Around coastal areas the water seeping into the rock can contain salt and when expanded can leave some interesting weathering patterns

Plant Activity

  • The roots of plants and trees grow into cracks within rocks , as the roots grow in size they widen the cracks in the rocks
  • in the end the root is too strong and eventually breaks the rock apart.


  • Abrasion is a breakdown of a rock by friction.
  • Stationary rocks are literally scraped away by other loose rock and mineral fragments
  • These small fragments are carried by the air or water and come in contact with other stationary rocks acting as a natural sandpaper