How do abrasion and attrition differ?

Abrasion wears the bed; attrition rounds the load itself.

Why does traction dominate the upper course?

Steep slopes give fast flow with enough power to roll coarse pebbles.

S4 Geography River Processes, Paper 1: erosion and transportation

2026-11-05

Fast upper-course flow makes hydraulic action and abrasion strongest, while load size decides between traction, saltation, suspension and solution.

Focus　Judge grain size first, then name the matching erosion and transportation process.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 3 · Intermediate 4 · Challenge 2 · Error redo 1
Chapter	Chapter: S4 Geography: River Management and Water Resources
Level	S4

02　Questions (10 items)

FoundationWater forced into cracks compresses air and prises rock apart. Name this erosion process.
FoundationSand and gravel carried by the river scrape the bed. Name this process.
FoundationStones knock against each other and become smaller and rounder. Name this process.
IntermediateRiver water dissolves a limestone bed. Name this process.
IntermediateLarge pebbles roll along the river bed. Name this transportation process.
IntermediateFine sand bounces along in short hops. Name this transportation process.
IntermediateSilt and clay are carried while held up in the water. Name this process.
ChallengeName the whole area drained by a river from source to mouth.
ChallengeName the point where a river enters the sea and the point where it begins.
Error redoA slow, wide, sandy reach is dominated by which transportation process?

03　Answers and one-line notes

#	Answer	One-line note
1	hydraulic action	Fast flow compresses air in cracks and prises rock apart.
2	abrasion	The load acts like sandpaper and deepens the channel.
3	attrition	Attrition rounds the load but does not deepen the bed directly.
4	solution (corrosion)	Weakly acidic water dissolves limestone and forms karst features.
5	traction	Traction needs strong flow and is common in floods and upper courses.
6	saltation	Grains hop repeatedly and form a large part of the load.
7	suspension	The finest load travels far and settles at the mouth.
8	drainage basin	A watershed divides one basin from the next.
9	mouth; source	The source lies in highland; the mouth often has a delta or estuary.
10	suspension	Slow water carries only the finest load; traction and saltation need faster flow.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

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