G16: Erosion, Transport & Deposition
The processes of erosion, transport and deposition by rivers, wind, ice and gravity, and the landforms they create.
Erosion, Transport & Deposition
The processes of erosion, transport and deposition by rivers, wind, ice and gravity, and the landforms they create.
Key Fact: Erosion is the removal and transport of weathered material by rivers, wind, ice and gravity
Key Fact: River erosion processes: hydraulic action (force of water), abrasion (sediment scraping bedrock), attrition (particles rounding), solution (dissolving)
Key Fact: Transport methods: traction (rolling large particles), saltation (bouncing), suspension (fine particles carried in water), solution (dissolved load)
Key Fact: Deposition occurs when the transporting agent loses energy: river slows (inside of meander, floodplain), glacier melts, wind drops
Key Fact: Glacial erosion: plucking (freezing onto rock and pulling fragments), abrasion (rock-laden ice scouring bedrock, producing striations)
Key Fact: Wind erosion and deposition: deflation (removing fine material), abrasion (sand-blasting), loess (wind-blown silt deposits)
📋 Key Vocabulary and Concepts
For Erosion, Transport & Deposition, you must know:
- Hydraulic action: Erosion by the sheer force of water pressing against river banks and bed, compressing air in cracks and prising rock apart
- Abrasion: Erosion where sediment carried by water, ice or wind scrapes against bedrock, wearing it down like sandpaper
- Saltation: A mode of sediment transport where particles bounce along the river bed or ground surface
- Plucking: Glacial erosion where meltwater freezes onto rock, and as the glacier moves it pulls rock fragments away
- Striations: Scratches grooved into bedrock by rock fragments embedded in the base of a moving glacier
❓ Practice Questions
Q: Name the four processes of river erosion.
Q: Describe the four methods of sediment transport by rivers.
Q: What causes deposition to occur?
Q: How does glacial erosion differ from river erosion?
Q: What are striations and what do they indicate?
✅ Answers
- Hydraulic action (water force), abrasion (sediment scraping bedrock), attrition (particles colliding and rounding), solution (dissolving soluble rocks).
- Traction: large particles roll along the bed. Saltation: medium particles bounce along the bed. Suspension: fine particles carried within the water flow. Solution: dissolved minerals carried invisibly in the water.
- Deposition occurs when the transporting agent (river, wind, ice) loses energy and can no longer carry its sediment load. This happens when velocity decreases, gradient flattens, the flow meets an obstacle, or the glacier melts.
- Glaciers erode by plucking (freezing onto rock and pulling it away) and abrasion (rock-laden ice grinding bedrock, producing striations and roches moutonnees). Rivers erode by hydraulic action and abrasion with water-borne sediment. Glaciers are much more powerful at eroding solid bedrock and carving U-shaped valleys.
- Scratches and grooves on bedrock surfaces caused by rock fragments frozen into the base of a glacier scraping across the rock. They indicate the direction of ice movement.
🎯 Exam Tips
- Four erosion processes: hydraulic action, abrasion, attrition, solution
- Four transport methods: traction, saltation, suspension, solution
- Deposition = loss of energy (velocity, gradient, volume decrease)
- Glacial: plucking and abrasion; River: hydraulic action and abrasion
📝 Exam Technique
GCSE Geology Exam Tips — Erosion, Transport & Deposition:
1. For Erosion, Transport & Deposition questions, use correct geological terminology and classify features precisely
2. Reference specific geological time periods and processes
3. When interpreting data, consider the quality and limitations of the evidence
4. Apply your understanding of Erosion, Transport & Deposition to fieldwork observations and map data
5. For evaluation, weigh competing geological theories with evidence
1. For Erosion, Transport & Deposition questions, use correct geological terminology and classify features precisely
2. Reference specific geological time periods and processes
3. When interpreting data, consider the quality and limitations of the evidence
4. Apply your understanding of Erosion, Transport & Deposition to fieldwork observations and map data
5. For evaluation, weigh competing geological theories with evidence
⚠️ Common Errors
✗ Attrition and abrasion are the same ✓ Abrasion is sediment scraping the BEDROCK (wearing down the river bed). Attrition is particles colliding with EACH OTHER, making them smaller and rounder
✗ Deposition only happens in still water ✓ Deposition occurs whenever transport energy drops below the threshold needed to carry the sediment, which can happen in slow but still-moving water (e.g. inside of a meander bend)
✗ Glaciers carry sediment on top only ✓ Glaciers carry sediment at the base (subglacial, by abrasion and plucking), within the ice (englacial), and on the surface (supraglacial, from rockfall onto the ice)
✍️ Model Answer
Full-Mark Response
Describe the processes of erosion, transport and deposition by rivers and glaciers, and compare their effectiveness. [6 marks]
Rivers erode by hydraulic action (water force compressing air in cracks and prising rock apart), abrasion (sediment scraping the bedrock like sandpaper), attrition (particles colliding and rounding each other), and solution (dissolving soluble rocks like limestone). Rivers transport sediment by traction (rolling large clasts), saltation (bouncing medium particles), suspension (carrying fine silt in the water column) and solution (dissolved load). Deposition occurs when flow energy drops, e.g. on the inside of meander bends, on floodplains and in deltas. Glaciers erode primarily by plucking (meltwater refreezes onto bedrock and the moving ice pulls rock fragments away) and abrasion (rock debris embedded in the ice base grinds the bedrock, producing striations, roches moutonnees and rock flour). Glaciers are far more effective at eroding solid bedrock than rivers because of their immense weight and the rocks embedded in their base. They carry enormous loads of unsorted sediment (boulders to clay) that they deposit as till (moraines) when the ice melts. While rivers sort sediment by size during transport (coarse in high energy, fine in low energy), glaciers deposit unsorted till because all sizes are carried together and dumped when the ice melts. Glaciers carve distinctive U-shaped valleys, while rivers form V-shaped valleys.
📊 AO Deep Dive
Assessment Objective Analysis
AO1 (Knowledge & Understanding): Demonstrate knowledge and understanding of erosion, transport & deposition, including key geological concepts, observational data and theoretical models relevant to OCR J357.
AO2 (Application of Knowledge): Apply knowledge and understanding of erosion, transport & deposition to both familiar and unfamiliar geological contexts, using field evidence and theoretical principles to explain phenomena.
AO3 (Analysis & Evaluation): Analyse geological data related to erosion, transport & deposition, evaluate evidence from observations and investigations, and construct reasoned arguments using scientific methodology.
📝 Exam Questions by Topic
🎬 Video Resources
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