Weathering and Erosion
Weathering and erosion are natural processes that slowly break down and reshape the Earth’s surface. Together, they play a key role in shaping landscapes such as mountains, valleys, cliffs, and coastlines. These processes work over long periods of time and are influenced by climate, rock type, and human activity.
What Is Weathering?
Weathering is the process by which rocks are broken down in situ, meaning they are broken down where they are, without being moved. Weathering weakens rock and prepares it to be removed by erosion.
There are three main types of weathering.
Physical (Mechanical) Weathering
Physical weathering breaks rock into smaller pieces without changing its chemical composition. This type of weathering is common in cold or dry climates.
Examples include:
• Freeze-thaw weathering, where water enters cracks, freezes, expands, and splits the rock
• Thermal expansion, where rocks expand in heat and contract when cooled
Chemical Weathering
Chemical weathering occurs when rocks are broken down by chemical reactions. Rainwater is naturally slightly acidic and can react with certain minerals, causing rock to dissolve or weaken.
This type of weathering is most effective in warm, wet climates.
Examples include:
• Carbonation, where acidic rainwater reacts with limestone
• Oxidation, where iron-rich rocks react with oxygen, causing rusting
Biological Weathering
Biological weathering is caused by living organisms. Plant roots can grow into cracks in rock and force them apart, while animals and humans can also contribute to rock breakdown.
Examples include:
• Tree roots splitting rock
• Burrowing animals loosening material
What Is Erosion?
Erosion is the process by which weathered material is moved from one place to another. This movement is caused by natural forces such as water, wind, ice, and gravity.
Erosion shapes landscapes by transporting material away from its original location and depositing it elsewhere.
Types of Erosion
Water Erosion
Rivers and rainfall can carry rock and soil downhill, carving valleys and shaping floodplains.
Wind Erosion
In dry environments, wind can pick up fine particles and wear away rock surfaces.
Ice (Glacial) Erosion
Glaciers scrape and pluck rock as they move, creating steep valleys and sharp ridges.
Gravity (Mass Movement)
Material can move downhill due to gravity, causing landslides or rockfalls.
