THE earth's landscape is always changing - rocks and soil are worn away by water, wind, ice and gravity.
This process is known as erosion and can happen suddenly, such as when a landslide happens, or gradually, such as when a river carves a deep valley into the surface of the earth. -
The Encyclopedia of Questions and Answers, Dorling Kindersley
Landscape changes
THE earth's landscape is always changing - rocks and soil are worn away by water, wind, ice and gravity.
This process is known as erosion and can happen suddenly, such as when a landslide happens, or gradually, such as when a river carves a deep valley into the surface of the earth. -
The Encyclopedia of Questions and Answers, Dorling Kindersley