Weathering

Weathering is the breaking down of rocks into small particles such as sand and pebbles. There are 2 types of weathering - physical and chemical weathering.

1. Physical Weathering can be of several types:

• Exfoliation (or flaking) of rocks due to expansion in extremely high daytime temperatures, and contraction in very cold night time temperatures
• Expansion of ice in cracks of the rock, where water in the cracks freezes and expands to break the rock
• Abrasion by particles such as sand carried by wind or water
• Damage from tree roots
• Damage from animals walking or by machinery such as cars and bulldozers

2. Chemical Weathering occurs when natural chemicals break down rocks. Examples are:

• Slightly acidic rain that has been combined with carbon dioxide in the air slowly deteriorates rocks over time
• Acids from decaying plants such as lichens also breaks down rocks

Erosion

Erosion is the process of carrying away the small rock particles such as sand and pebbles. The main agents of erosion are:

• Water (in rivers, ocean waves and glaciers)
• Wind
• Gravity (when rocks fall from a cliff face or in a mudslide)
• Animals and machinery