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Delta Modern Language School
Grade 4
Date ......./......./………

             Important points on Unit (4) Concept 4.1

                  Breaking down and moving rocks

Factors that change the Earth’s surface: -

Wind, Water and Weather changes.

➢ Sand is formed by breaking down of some types of rocks into smaller
   particles.

➢ Erosion of the sandcastles and coasts is a result of natural erosion (the
   forces of water and wind).

➢ Some changes of the Earth’s surface can be very fast and other changes
   can be very slow that may take hundreds of millions of years.

          Fast Changes                       Slow Changes

• They are observed in             • They are observed in coastal
   Sandcastles.                      rocks over time.

• It may completely disappear in   • Little differences can be observed
   few minutes as a result of the    in their shape after many years
   force of sea waves.               after breaking off some parts.

Canyons: They are deep valleys covered by flowing water.

➢ Canyons are formed due to the slow changes
   that happened to their rocks over many
   years.

➢ A canyon has needle-like parts and slopes at
   the sides, it is formed by the action of water.

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