rock formations and rock cycle Select a lesson
 


What are rocks made ofIgneous rocks formationFormation of sedimentary rocksFormation of metamorphic rocksphysical weathering of rocksChemical weathering of rocksBiological weathering of rocksRock erosion and transportExplain the rock cycle



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The rock cycle for kids


Physical Weathering

Physical factors such as freezing and thawing, temperature, rain, winds, waves, water pressure and others can cause rocks to break up into tiny pieces. Specific types of physical weathering occur in specific places.

Here are a few examples:

Weathering by temperature changes:
The sun’s energy can heat up rocks to very high temperatures. This causes rocks like granite to expand. As temperatures fall, the rocks cool down and contract. Continuous expansion and contraction causes pressure on the outer layers of the rock. Cracks develop as a result, and eventually, the outer layers of the rock wear off. This is also known as exfoliation.

Weathering by water, wind and waves:
Winds, water and waves pound on rocks and wears them up. Prolonged action causes larger rocks with rugged surfaces to smoothen. During runoff, water carries sand and smaller debris and smashes them against larger rocks in their path. The resulting abrasion causes wearing of rocks.

Freeze and thaw:
Put a glass of water in a freezer and it will break up. Why? This is because water expands when it freezes. Take a look at the diagram below:

physical weathering example

When water collects in rock pores and cracks and spaces they expand when they freeze, particularly in cold climates. The freezing widens and causes additional cracks. When the ice thaws, the water enters into new cracks again and causes further cracks as they freeze. Soon the rocks break apart. (learn about how weathering can impact landforms)

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Types of rocks for kids