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Erosion Processes

Learn how hydraulic action, abrasion, attrition and solution wear away rock.

  • Define and explain Erosion Processes in your own words
  • Use key terms such as erosion accurately
  • Apply what you have learned to new examples and questions
  • Avoid the common mistakes learners make with this topic

This lesson focuses on Erosion Processes: learn how hydraulic action, abrasion, attrition and solution wear away rock.

Definition: Erosion Processes

Learn how hydraulic action, abrasion, attrition and solution wear away rock.

Key ideas

Four processes of erosion

Hydraulic action is the force of the water itself; abrasion is material scraping against rock like sandpaper; attrition is pebbles knocking together and becoming smaller and rounder; solution is minerals dissolving in slightly acidic water. All four act together in rivers and at the coast.

Erosion is not weathering

Weathering breaks rock down where it sits — for example, freeze-thaw shattering or rainwater dissolving limestone. Erosion then picks the broken material up and moves it. At the coast, both work together: weathering weakens a cliff while waves erode its base.

Key term — erosion: The wearing away of rock and soil by moving water, wind or ice, which then carries the material away.

Worked example: Erosion Processes

Name the four processes of river erosion.

Hydraulic action, abrasion, attrition and solution.

Answer: Hydraulic action, abrasion, attrition and solution.

Common mistakes
  • Confusing erosion with weathering Weathering breaks rock in place; erosion moves it. Freeze-thaw is weathering, but a river carrying pebbles away is erosion.
  • Saying the fastest flow is on the inside of the bend It is the outside of the bend: faster water erodes the outer bank, while slower water on the inside deposits to form a slip-off slope.

Practice

Give one difference between weathering and erosion.
One moves material, the other does not.

Weathering breaks rock down in place; erosion wears it away and transports it.

A cliff is being undercut by waves at its base. Which process is at work, and what might happen next?
The force of the water is doing the work.

Hydraulic action (with abrasion). The overhang will eventually collapse, causing the cliff to retreat.

Why does erosion happen on the outside of a meander bend?
Think about where the water flows fastest.

Water flows fastest on the outside of the bend, giving it more energy to erode the outer bank.

In which course of a river would you find a waterfall?
Think about where the slope is steepest.

The upper course.

Quick check

Erosion Processes — quick check

Which of these best defines "erosion"?

The wearing away of rock and soil by moving water, wind or ice, which then carries the material away.

What is deposited on the inside of a meander bend, and what landform does it create?

Sand and shingle are deposited, building a gently sloping slip-off slope (point bar).
Key takeaways
  • Erosion Processes: learn how hydraulic action, abrasion, attrition and solution wear away rock.
  • Four processes of erosion: Hydraulic action is the force of the water itself; abrasion is material scraping against rock like sandpaper; attrition is pebbles knocking together and becoming smaller and rounder; solution is minerals dissolving in slightly acidic water.
  • hydraulic action: Erosion caused by the sheer force of water — waves or river currents compress air into cracks, widening them.
  • Watch out for: confusing erosion with weathering
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