Question

There are two kinds of weathering: mechanical weathering and chemical weathering. Mechanical weathering happens when something breaks down due to physical forces. High or low temperatures, water, and pressure can cause mechanical weathering.


High temperatures can cause minerals in soil or stone to grow bigger. Low temperatures can cause ice to form. Ice expands when it forms. This can make soil looser or crack rocks. This is also how water pipes burst in the winter. Just like in rocks, the ice splits open the pipes.


Another example of mechanical weathering is when ocean waves beat down rocks and soil near the sea. It also happens when rocks go from being under high pressure to lower pressure. It makes them expand and crack.


Granite cracked due to expanding rock

Weathering from chemical reactions is called chemical weathering. The chemicals can come from the atmosphere or from living things. Acid rain can cause chemical weathering. Acid rain is rain filled with pollution. The acid can break down some materials.


Rusting is also chemical weathering. When iron touches water, it becomes weaker. It turns red. This process is called rusting.


A sculpture damaged by acid rain

Living things can cause weathering. Growing plants can force soil and rocks apart. Think about plants growing through the sidewalk. Plants can also release chemicals that wear down stone.


Erosion

Erosion is similar to weathering, but it isn’t the same thing. Weathering only involves materials breaking down. Erosion is when something moves those materials somewhere else.


Many different things can cause erosion. Rain and flowing water can sweep away loose rock and soil. Wind can sweep away loose particles. Even gravity can cause erosion. You can see this when rocks fall down a mountainside.


Humans also cause erosion. Cutting down trees and farming loosen soil. This makes it easier for erosion to sweep that soil away.


Erosion caused by deforestation

If you’ve seen a river full of dirt, you’ve seen erosion. The water is moving dirt and rocks from somewhere else. Rocks falling down a mountain are another sign of erosion. The Grand Canyon was made because of erosion. The huge rock formations in the Grand Canyon were made by the Colorado River and the wind.


A rock formation in the Grand Canyon

Erosion can be good or bad. For example, the Nile River eroded healthy soil and brought it to Egypt. This soil made it easier to grow food for the ancient Egyptians.


But, erosion can cause dangerous mudslides. These mudslides can bury villages and towns. Erosion can also move healthy soil away. This makes it hard for plants to grow in that area. The area can become like a desert. People need to be careful about making erosion happen.


Our planet is always changing. Weathering and erosion are a big part of why. Understanding weathering and erosion is important. It teaches us how Earth has changed and how it will change.


Questions
What is the main reason weathering and erosion are important?


They helped ancient people survive.


They change the landscape of the earth.


They are the exact same thing.


They can crack rocks very quickly.

Answer 1

They change the landscape of the earth.

The passage says weathering and erosion are a big part of why our planet is always changing and help us understand how Earth has changed and will change.