Ice erosion, primarily through glaciers, works through two main processes: abrasion and plucking (also known as quarrying). These processes reshape landscapes over long periods, carving out valleys and transporting vast amounts of rock and sediment.
Abrasion: The Sandpaper Effect
Abrasion occurs as glaciers, laden with rock debris and sediment, slide over the underlying bedrock. This embedded material acts like sandpaper, grinding and polishing the rock surface. The finer material creates glacial striations (scratches and grooves) that indicate the direction of ice movement. The coarser material can carve out larger features.
- Process: Glacier moves -> embedded rocks scrape bedrock -> grinding & polishing occurs -> striations & grooves formed.
- Effect: Smoothing and polishing of rock surfaces. Creation of striations indicating glacial flow direction.
Plucking (Quarrying): The Icy Excavator
Plucking involves the removal of larger pieces of rock from the bedrock. This process is particularly effective in areas with fractured or jointed rock.
- Process:
- Meltwater Penetration: Meltwater from the glacier seeps into cracks and joints in the bedrock.
- Freezing and Expansion: The water freezes, expands, and exerts pressure on the surrounding rock.
- Rock Fracture: The pressure causes the rock to fracture and weaken.
- Plucking: As the glacier moves, it pulls away the loosened rock fragments.
- Transportation: The plucked rock fragments are then carried away within or on the glacier.
- Effect: Significant removal of bedrock material, creating a jagged and uneven landscape. Formation of cirques (bowl-shaped depressions) and other glacial features.
Summary of Ice Erosion Processes
| Process | Description | Result |
|---|---|---|
| Abrasion | Grinding and polishing of bedrock by sediment-laden ice. | Smoothed and polished rock surfaces; striations and grooves. |
| Plucking | Removal of large rock fragments due to freeze-thaw action and glacial movement. | Jagged and uneven landscape; formation of cirques and other glacial features. |
In essence, ice erosion is a powerful combination of grinding and excavation, resulting in dramatic changes to the landscape over geological timescales.
