Weathering and Mass Movement

Mechanical Weathering

Mechanical weathering is the psychical breakdown of rock by environmental factors

The process:

Constantly happening

Unable to see a rock expanding due to the temperature fluctuation although it does happen. It weakens the rock causing it to eventually break down

Thermal Expansion

When temperature fluctuations affect rocks (process known as thermal expansion):

The tendency for minerals to expand and contract based on rapid change of temperature.

The change of temperature cause stress and small cracks within the rocks which lead to the gradual breakdown of the rock

Frost shattering

Frost shattering is:

The breakdown of rock due to the expansion of ice

It happens in the crevices between rocks.

Day when temperatures are warm, water trickles into cracks and pores within rocks

Night: temperature drops , water freezes and expands, the cracks within the rocks widen and eventually shatter portions of the rock

Plant Activity

The roots of plants and trees grow into cracks within rocks

As the roots grow in size, they widen the cracks. The roots often win the battle and push the rock, causing pieces of the rock to fall off.


Abrasion is the breakdown of rock by friction.

Stationary rocks are scraped away by other loose rock and mineral fragments.

These fragments are carried away by the air or water and come in direct contact with the stationary rocks.

In deserts, abrasion occurs where sand is picked up and carried away by the wind. The sand acts like natural sandpaper, smoothing the surface layer of rocks.