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

  • Biological weathering
  • Chemical weathering
  • Mechanical weathering

Biological Weathering

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

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

Weeds can grow through pavement, and their roots can widen existing cracks.

Chemical Weathering

Chemical weathering is the breakdown of rocks into smaller pieces due to chemical reactions.

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.

Consider, for example, a limestone statue.

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

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

Mechanical Weathering

Mechanical weathering involves 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 temperature changes. 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.

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