Weathering and Erosion: Breaking Down Earth's Surface

Weathering and Erosion: Breaking Down Earth's Surface

Learning Objective

At the end of the lesson, you will be able to identify the different forms of weathering, understand how ice, plant roots, and changes in temperature cause weathering, recognize the types of weathered material and how they differ in size, and comprehend how the transport of weathered material can cause erosion.

Introduce the lesson's objectives to the students and explain how they will be able to apply what they learn.

What do you already know about weathering and erosion?

What is Weathering?

Weathering is the process of breaking down rocks, soil, and other materials on Earth's surface.

Explain to students that weathering can be caused by physical, chemical, and biological processes, and that it is the first step in the erosion process.

Forms of Weathering

There are two forms of weathering: mechanical and chemical.

Discuss the differences between mechanical and chemical weathering and give examples of each.

Mechanical Weathering

Mechanical weathering is the process of breaking down rocks into smaller pieces without changing their chemical composition. Examples of mechanical weathering include ice wedging, plant roots, and changes in temperature.

Explain to students the different ways mechanical weathering can occur and give examples of each.

Ice Wedging

Ice wedging occurs when water seeps into cracks in rocks, freezes, and expands, causing the rock to break apart.

Demonstrate ice wedging with an interactive activity, such as freezing water in a container with a rock inside and observing the effects.

Plant Roots

Plant roots can grow into cracks in rocks and widen them as they grow.

Show students pictures of plants growing on rocks and explain how their roots can break down the rock over time.

Temperature Changes

Temperature changes can cause rocks to expand and contract, eventually causing them to break apart.

Give examples of temperature changes that can cause mechanical weathering, such as freezing and thawing cycles.

Chemical Weathering

Chemical weathering is the process of breaking down rocks by changing their chemical composition. Examples of chemical weathering include oxidation, hydration, and carbonation.

Explain the different ways chemical weathering can occur and give examples of each.

Oxidation

Oxidation occurs when oxygen reacts with minerals in rocks to form new compounds.

Give examples of rocks that can be affected by oxidation, such as iron-rich rocks that rust when exposed to air and water.

Hydration

Hydration occurs when water combines with minerals in rocks to form new compounds.

Explain how hydration can cause rocks to break down over time and give examples of rocks that can be affected by hydration.

Carbonation

Carbonation occurs when carbon dioxide in the air reacts with minerals in rocks to form new compounds.

Give examples of rocks that can be affected by carbonation, such as limestone that dissolves over time when exposed to acidic rainwater.

Types of Weathered Material

There are three types of weathered material: boulders, gravel, and sand.

Explain the differences between boulders, gravel, and sand and how they are created through weathering.

Boulders

Boulders are large rocks that have been weathered down to a size greater than 256 mm.

Give examples of boulders and explain how they can be transported through erosion.

Gravel

Gravel is made up of rocks that have been weathered down to a size between 64 mm and 256 mm.

Give examples of gravel and explain how it can be transported through erosion.

Sand

Sand is made up of rocks that have been weathered down to a size between 0.063 mm and 2 mm.

Give examples of sand and explain how it can be transported through erosion.

Erosion

Erosion is the process of transporting weathered material from one location to another.

Explain to students the different ways erosion can occur, such as through water, wind, or glaciers.

Water Erosion

Water erosion occurs when water carries weathered material from one location to another.

Give examples of water erosion, such as rivers carving out canyons or beaches forming from sand transported by waves.

Wind Erosion

Wind erosion occurs when wind carries weathered material from one location to another.

Give examples of wind erosion, such as sand dunes forming in deserts or sandblasting effects on rock formations.

Glacial Erosion

Glacial erosion occurs when glaciers carry weathered material from one location to another.

Give examples of glacial erosion, such as U-shaped valleys carved by glaciers or moraines left behind by retreating glaciers.

Review

Today we learned about weathering and erosion. We discussed the different forms of weathering, including mechanical and chemical, and how ice, plant roots, and changes in temperature can cause weathering. We also talked about the types of weathered material and how they differ in size, and how the transport of weathered material can cause erosion.

Review the main points of the lesson and ask students if they have any questions or need clarification on any topics.

Write down 3 things you learned in this lesson.

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.

Write down 2 things you want to know more about.

Here, students enter two things they would like to know more about. This not only increases involvement, but also gives them more ownership.

Ask 1 question about something you haven't quite understood yet.

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.