Follow a grain of sediment
Erosion, transport and deposition do different jobs. Keep track of what changes.
Erosion removes material
Hydraulic action can force air and water into cracks. Abrasion occurs when carried material wears away the bed or banks.
Transport moves it
Traction rolls larger particles along the bed. Saltation moves smaller particles in hops. Fine material can be held in suspension.
Attrition changes particles
Carried particles collide. Their edges break off, making them smaller and more rounded.
Deposition leaves material
When flow loses the ability to transport a particle, it is deposited. Different particle sizes need different conditions.
Longshore drift
On a beach, waves approaching at an angle move sediment obliquely up the shore in swash. Backwash moves it down the slope, producing net transport along the coast.
Try it yourself
Explain why a river may deposit sediment when it enters a lake.
One possible answer
The river slows as it enters the lake. Its ability to transport sediment falls, so some particles settle. Larger particles are generally deposited before finer material.
Check your answer: did you address the question, use accurate evidence and explain the link?
Check your understanding
Is attrition the same as abrasion?
Check the explanation
No. Attrition wears down the carried particles through collisions. Abrasion wears away a surface using the material being carried.
Put it to use
Sources and teaching notes
Original teaching sequence. Artwork is an imagined editorial scene, separate from geographical evidence.