Weathering is the process of breaking down large rocks into smaller pieces. There are three main types of weathering we will look at:

  • Biological weathering
  • Chemical weathering
  • Mechanical weathering

Biological Weathering

Biological weathering is a form of weathering that is caused by plants and animals, in which they break rocks into smaller pieces.

An example of this is when you see weeds growing in a pavement. The weed roots grow into the cracks of the rock, making the cracks deeper and breaking away smaller pieces of rock.

Weeds are able to grow out of pavements and the roots will find cracks, making them larger.

Chemical Weathering

Chemical weathering is the breakdown of rocks caused by chemical reactions, breaking down rocks into smaller pieces

The most common example of chemical weathering is rainwater eroding certain types of rocks. For example, rainwater can be slightly acidic, as it contains dissolved carbon dioxide (CO2). Minerals in certain rocks can react with the acidic rainwater, leading to weathering of the rock.

For example, the limestone statue below:

  • The small pieces of rock dissolved in the water are carried away.

Erosion is the movement of weathered rock and other materials by gravity, water, or wind.

Mechanical Weathering

Mechanical weathering is the breaking down of rocks through physical force. In this process, there is no change to the chemical nature of the rock.

Mechanical weathering is typically caused by extreme hot and cold temperatures. An example is freeze-thawing, which is when water seeps into cracks, then freezes and expands. This puts pressure on the cracks, causing the breakdown of rocks into smaller pieces.

Another example is when water bashes into rocks and causes weathering.