Weathering and Erosion
Distinguish breakdown, transport, and deposition, then use climate, energy, landform, and experimental evidence to explain landscape change.
Weathering and Erosion
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Weathering breaks; erosion carries; deposition drops
weathering: breakdown in placeerosion: removal and transportdeposition: settling when transport energy decreasesMechanical weathering changes rock size without changing mineral identity. Chemical weathering changes minerals through reactions such as oxidation, dissolution, and hydrolysis.
Climate controls weathering
Warm wet conditions favor chemical reactions; freeze-thaw needs water and repeated temperature crossing around freezing.
Surface area changes rate
Smaller fragments expose more material to chemical attack.
Transport sorts sediment
Fast water can carry larger particles; falling velocity deposits larger material first.
Landforms record energy
Cut banks, bars, deltas, dunes, and glacial deposits reveal transport and deposition conditions.
People change erosion risk
Vegetation removal, construction, farming, and channel modification affect runoff and sediment movement.
Use BREAK → MOVE → DROP
BREAK: Was material physically fragmented or chemically changed?
MOVE: What agent transported it—water, wind, ice, or gravity?
DROP: Where did energy decrease enough for deposition?
More than one stage may appear in the same scenario.
Why it works
This prevents the common error of calling every change “erosion,” even when the question describes breakdown or deposition.
Five forms you should recognize
Problem: Powder and a solid block of equal limestone mass contact equal acid.
The powder reacts faster because it has greater exposed surface area.
Problem: A bend has a steep outside bank and a sandy inside bar.
Faster outer flow causes erosion; slower inner flow causes deposition.
Problem: A stream becomes muddy after trees are removed.
Exposed soil and faster runoff increase erosion and sediment transport.
Problem: Melting ice leaves an unsorted mixture from clay to boulders.
The unsorted deposit is consistent with glacial till.
Problem: A beach narrows after one storm.
The storm redistributed or removed sand, but repeated observations are needed to determine a long-term trend.
Check before you commit
- Calling weathering transport
- Calling deposition erosion
- Assuming chemical weathering is fastest in cold dry climates
- Ignoring surface area in reaction-rate comparisons
- Assuming every sediment deposit is well sorted
- Using one storm to prove a permanent trend
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Weathering and Erosion FAQ
Can weathering and erosion happen together?
Yes. Rock may weather while fragments are being removed and transported.
Why are river pebbles often rounded downstream?
Repeated collision and abrasion wear down edges during transport.
Does vegetation stop all erosion?
No. It usually reduces erosion by protecting and binding soil, but extreme rainfall or slope failure can still move material.
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