Weathering, Erosion and Deposition: Grade 4 Study Guide
The surface of the Earth is always changing, sometimes slowly and sometimes in a flash.
The shape of the land is the result of three linked processes. Weathering breaks rock into smaller pieces. Erosion moves those pieces from one place to another. Deposition is when they are dropped and settle in a new place.
Some changes are slow, such as a river carving a canyon over millions of years, and some are fast, such as a landslide, volcanic eruption or earthquake. Maps and rock layers (fossils in them) give evidence of how landscapes changed.
Weathering
Weathering can be physical (rock is broken without changing what it is made of) or chemical (the rock's minerals change). Water seeps into cracks, freezes and expands, splitting the rock. Plant roots grow in cracks and push them wider. Rain slightly acidic from carbon dioxide can dissolve some rocks, such as limestone.
| Process | Agent | Result |
|---|---|---|
| Weathering | frost, roots, rain | rock breaks into pieces |
| Erosion | water, wind, ice, gravity | pieces are carried away |
| Deposition | slowing water or wind | sediment settles in new place |
Erosion and deposition
Moving water is the biggest agent of erosion. Fast rivers pick up soil, sand and pebbles. When the river slows, such as where it meets a lake or sea, it drops the sediment and builds a delta. Wind moves dust and sand to form dunes. Glaciers scrape valleys as they slide. Gravity pulls rocks downhill.
A cliff cracks.
Rain carries the pieces to a stream.
The river carries sediment downstream.
Sediment settles in a delta.
Reducing the impact on people
Humans can slow erosion. Planting trees and grass holds soil, terraces on slopes slow runoff, and sea walls or dunes protect the coast. Engineers test different solutions using models, such as a tray of sand and a watering can.
Worked example and common misconceptions
Example: In a stream table, a steeper slope carries more sand and builds a bigger delta. Common misconceptions: thinking all changes take millions of years, or mixing up weathering (breaking) with erosion (moving). A simple memory aid is W-E-D: Weather, Erode, Deposit.
Check your understanding: model answers
1. Weathering breaks rock into pieces; erosion carries the pieces away. 2. A slowing river drops sediment where it meets a lake or sea. 3. For example, plant grass or trees on the slope.
✨ Key Takeaways
- Weathering breaks, erosion moves, deposition drops.
- Water is the main agent of change.
- Some changes are slow and some are fast.
- People can reduce erosion.
💬 Questions for Discussion & Reflection
- What is the difference between weathering and erosion?
- How is a delta formed?
- Give one way to reduce soil erosion.
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