Rivers and wind move things
Erosion carries pebbles, soil and sand away.
Sand on the riverbed
Have you seen fine sand lying on a riverbed or at the edge of a lake? It was not made there. It came from somewhere else.
How did the sand get there?
What this lesson covers
The idea
Erosion is the breaking down and moving of rock pebbles, soil and sediments from one place to another by natural forces like wind and flowing water; it is a physical change.
Sand on the riverbed
Have you seen fine sand lying on a riverbed or at the edge of a lake? It was not made there. It came from somewhere else.
How did the sand get there?
- Flowing water or wind carried it from another place
- It grew there like a plant
- It fell from the sky as snow
Start the flow
Pick flowing water or wind, then press Start the flow. Try both.
Moved from place to place
Water and wind picked up pebbles, soil and sand and moved them. Pebbles knocked about in a river become smooth. Nothing new was made, only moved and broken.
Erosion is the breaking down and moving of rock pebbles, soil and sediments from one place to another by natural forces like wind and flowing water. It is a physical change.
- Force | What it moves
- Flowing water | Pebbles, soil, sand
- Wind | Sand and fine soil
Notes
Erosion is the breaking down and moving of rock pebbles, soil and sediments from one place to another by natural forces like wind and flowing water. It is a physical change.
Check yourself
Which of these natural forces can cause erosion?
River pebbles often look smooth. Why?
Erosion is a …
During a landslide, rocks and soil slide down a hill. This is an example of …
- Only a magnet. A magnet does not move rocks in nature. Flowing water and wind do.
- Flowing water and wind — correct. Yes!
- Only a candle flame. A flame burns things. It does not carry pebbles, soil and sand away.
- The flowing water keeps rubbing and knocking them — correct. Yes!
- They were made smooth in a factory. River pebbles are natural. Constant erosion by flowing water makes them smoother.
- They were painted. Nobody painted them. Flowing water smooths them.
- physical change — correct. Yes!
- chemical change. In erosion no new substance forms. Things are only broken down and moved.
- change that can never happen. Erosion happens all the time, in rivers and in the wind.
- a chemical change. No new substance forms. The rocks and soil are only moved.
- burning. There is no fire, so it is not burning.
- a physical change — correct. Yes!