Unit 5 Lesson 2 How Does Earth’s Surface Change Slowly? · PDF file•Weathering is the breaking down of rock into ... •Glaciers slide along slowly. ... •As a river flows,...

Unit 5 Lesson 2 How Does Earth’s Surface Change Slowly?

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What Weathering Can Do


• Weathering is the breaking down of rock into smaller pieces.




• Weathering can happen when tree roots push into the

surface of rock. It can happen when animals burrow into the ground.




• Weathering is often caused by patterns of freezing and thawing.

• First, rain falls into cracks in rock and freezes.







• As liquid water turns to ice it expands. This widens the cracks.

• When the ice melts, or thaws, the rock is weaker.

• Pieces crumble and fall away. Little by little, the shape of the rock changes.




• Take a look at the picture and imagine how water can cause rocks to crumble and change shape.


Erosion Motion


• Erosion happens when soil, rocks, or sand are moved.

• Wind, water, and glaciers can all cause erosion. It happens everywhere. Wind blows desert sand. Waves wash away beach sand.


Erosion Motion



Erosion Motion



Erosion Motion


• A glacier is a large, thick sheet of moving ice.


Erosion Motion


• Glaciers slide along slowly.

• As they move, many glaciers cut paths through the ground.

• Glaciers also pick up pieces of weathered rock, sand, and soil.


Erosion Motion


• Glaciers push or carry the rocks and soil as they move.

• Sometimes glaciers move enough soil to form a whole island!


Erosion Motion



Soil Moves Around


• As a river flows, soil and rocks are swept downstream.

• Now, there is less soil on the riverbanks, and tree roots may be uncovered.

• Plants that need soil may be affected. Without the support of their roots anchored in deep soil, the trees might fall.


Soil Moves Around



Why It Matters Soil Moves Around


• As soil is washed away from a riverbank it ends up somewhere else.

• As a river nears the ocean, the rocks and soil are dropped.

• This process makes a landform called a delta. A river delta is full of rich soil.









Unit 5 Lesson 2 How Does Earth’s Surface Change Slowly? · PDF file•Weathering is the breaking down of rock into ... •Glaciers slide along slowly. ... •As a river flows,...

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