Rate of Weathering

Weathering and Erosion

Under the plants and water on Earth, there are rocks. Rocks are made of minerals. There are thousands of minerals on Earth. Only a few minerals make up most rocks, however. Different minerals give rocks different colors, shapes, sizes, and textures. Texture is how something looks and feels. Name all the colors you see on this rock wall. Which parts might feel smooth, sharp, or rough?

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A world of rocks

Kalman, B. (2009) What shapes the land? St. Catharines, Ont.: Crabtree Pub.

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How do living things change their environment?

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How do living things change their environment?

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the work of termites

human activities

transpiration by plants

the remains of coral animals

the work of beavers

What are Weathering and Erosion?

New land is created, but land is also worn down and carried away. The wearing and moving of land is called erosion. Erosion changes the landscapes on Earth. Landscapes are all the parts of the Earth you can see, such as mountains. Wind, rain, rivers, ocean waves, and ice all erode, or wear away, the land on mountains, coasts, deserts, and other landscapes.

What is erosion?

​Rocks are made weak by weather. Wind, rain, snow, ice, heat, cold, and frost can all weaken rocks. This weakening is called weathering. One way that weather weakens and breaks up rocks is by heating and cooling them. In some places the weather is hot during the day and cool at night. During the day, heat makes the rocks expand, or become larger. At night, the cool air makes rocks contract, or become smaller. Growing and shrinking makes the cracks in rocks wider. Eventually, the rocks break into pieces.

What is weathering?

​Kalman, B. (2009) What shapes the land? St. Catharines, Ont.: Crabtree Pub.

Labelling

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Ice erosion

Mechanical Erosion

Wind erosion

Water erosion

Chemical erosion

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How does deforestation affect soil erosion?



Deforestation ​​

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soil erosion. Tree roots act to ​

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soil. With the trees removed wind and rain dislodge soil ​

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easily.

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increases

hold

more

Multiple Choice

Does acid rain weather rocks at a slower rate or faster rate than ordinary rain? Why?

• a faster rate, because acids are powerful agents of chemical weathering

• a faster rate, because acids are powerful agents of mechanical weathering

• a slower rate, because acids react poorly with rocks and minerals

• a slower rate, because acids usually flow quickly over rocks without changing them

In some places the ground is too steep or too rocky to soak up any water. In other places, the ground may be able to soak up some of the water from a rainfall, but not all. Rainwater that the ground cannot soak up is called runoff. Runoff trickles or flows downhill into streams, rivers, lakes, and oceans. Runoff saturates, or fills the land with water. It removes the thin top layer of soil and carries it away.

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Running off with the soil

​Kalman, B. (2009) What shapes the land? St. Catharines, Ont.: Crabtree Pub.

Multiple Choice

What determines the amount of runoff that flows across the land during a rainstorm?

• the ability of the ground to soak up water

• the depth and width of a river channel

• the size of a lake

• the distance of the land to the ocean