The land is always changing. Some changes are very fast. A volcano can erupt in a day and pour out lava. An earthquake shakes the ground in seconds. A landslide can carry away part of a hill in minutes, and a flood can change a river bank overnight.
Other changes are very slow. Wind and rain wear away rock over hundreds or thousands of years; this is called weathering and erosion. A river slowly cuts a valley deeper. A canyon can take millions of years to form. People slow erosion by planting trees and grass, whose roots hold soil in place, and by building walls along rivers and coasts.
Worked example
Is the Grand Canyon an example of a fast change or a slow change?
- A river cut down through rock a tiny bit each year.
- It took millions of years.
Answer:So it is a very slow change.
Key words
- erosion
- rock and soil being carried away by water, wind or ice
- weathering
- rock being broken down where it is
- volcano
- an opening where melted rock comes out
- landslide
- a fast slide of soil and rock down a slope
Practise this
New questions every time.
NGSS-referenced: 2-ESS1-1