Weathering

• Rocks are worn down by a process called denudation, caused by weathering and erosion
• Weathering involves rocks being physically broken into smaller pieces or sediments, which remain in the same place
• There are three types of weathering: mechanical, biological, and chemical
• Mechanical weathering is the physical breaking down of rocks into smaller pieces
• Steps of freeze-thaw action:

  1. Water fills up the cracks (joints) in the mountains

  2. At night, the water freezes and the cracks expand by 10%

  3. This freezing and thawing cycle repeats until the cracks expand, weakening the rock and causing it to break into smaller pieces

  4. These pieces fall down and accumulate at the bottom, forming a pile called scree
• freeze thaw action is very active in upland areas such as mountains
• Freeze-thaw action is the most common type of mechanical weathering
• Biological weathering occurs when rocks are worn down by animals, plants, and living organisms
• Chemical weathering is caused by chemical changes when rock is dissolved or decays
• Carbonation is an example of chemical weathering
• In the process of carbonation:

  1. Water vapor mixes with carbon dioxide in the atmosphere

  2. This forms a weak carbonic acid (rainwater)

  3. The weak carbonic acid falls onto exposed limestone

  4. This converts the calcium carbonate (present in limestone) into calcium bicarbonate, which dissolves
• A karst landscape is made up of limestone.
• You can see th effects of carbonation in a karst landscape