Lesson Notes By Weeks and Term - Senior Secondary 3

Weathering

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TERM – 1ST TERM

WEEK FOUR

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Geography

Topic: WEATHERING

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Weathering and mention its types
  2. Explain the processes of weathering
  3. Discuss the effects of weathering on soil formation and farming

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher introduces and explain the meaning of weathering to the students. Teacher discusses the types of weathering

Students as a class; describe weathering and mention its types.

STEP 2

EXPLANATION

Teacher discusses the processes of weathering

Students in small groups, discuss the processes of weathering (temperature changes,  alternate wetting and drying, frost action etc)

STEP 3

DEMONSTRATIO

N

Teacher discusses the effects of weathering on soil formation and farming

 Individual students, highlight the effects of weathering on soil formation and farming. Students, in small groups project evidences of weathering in highland areas on cardboards

STEP 4

NOTE TAKING

The teacher writes a summarized note on the board

The students

copy the note in

their books

 

NOTE

WEATHERING

Weathering is the process by which rocks and minerals are broken down into smaller particles at or near the Earth's surface. This breakdown can occur through various mechanisms, including physical, chemical, and biological processes. Weathering is a fundamental step in the formation of soil and contributes to the ongoing alteration of the Earth's landscape.

Types of Weathering

  1. Mechanical Weathering: These process breaks down rocks into smaller particles without changing their chemical composition. It occurs through physical forces like temperature changes, frost action, wind, water, and abrasion.
  2. Chemical Weathering: This is the process by which rocks and minerals are broken down through chemical reactions, altering their composition. Various agents such as water, acids, oxygen, and organic substances can contribute to chemical weathering.
  3. Biological Weathering: This is the breaking down of rocks through the influence of living organisms. Plants, fungi, bacteria, and animals contribute to this process by physically or chemically altering the rock. For instance, plant roots may penetrate cracks in rocks, causing them to break apart, while certain organisms release acids that contribute to chemical weathering.

Processes of Weathering:

  1. Initiation: Weathering begins when rocks are exposed to environmental conditions. This can result from natural processes like uplift, erosion, or human activities.
  2. Breakdown: Rocks undergo physical, chemical, or biological processes that lead to their breakdown into smaller particles.
  3. Transportation: Weathered material may be transported by agents like wind, water, or ice, moving it away from its original location.
  4. Deposition: The transported material is deposited when the transporting agents lose their energy. This can lead to the accumulation of sediments in new locations.
  5. Soil Formation: The accumulated weathered material, combined with organic matter, contributes to the development of soil, supporting plant growth and other ecosystem functions.

Effects of Weathering on Soil Formation

  1. Weathering breaks down minerals in rocks into smaller particles. This mineral breakdown contributes to the mineral content of soils.
  2. Weathering processes influence soil texture by determining the proportions of sand, silt, and clay particles.
  3. Chemical weathering releases nutrients from minerals, making them available for plant uptake.
  4. Chemical weathering can alter the pH of the soil. For example, the breakdown of limestone can lead to the release of calcium carbonate, affecting soil alkalinity.
  5. Weathered material combines with organic matter derived from decaying plants and animals, fostering the development of humus in the soil.

Impact of weathering on Farming

  1. Weathering processes contribute to the release of essential nutrients, promoting soil fertility.
  2. Soil structure influenced by weathering affects water retention. Well-structured soils retain water effectively, providing a consistent water supply for crops.
  3. Weathering releases nutrients from minerals, ensuring a continuous supply of essential elements for plant growth.
  4. Intense weathering may lead to soil erosion if not managed properly.
  5. Farmers may need to manage soil pH based on the effects of weathering. Adding amendments can help neutralize acidity or alkalinity, creating an optimal pH for specific crops.

EVALUATION: 1. What is Weathering?

  1. Mention and discuss the 3 types of weathering.
  2. Describe the processes of weathering
  3. Mention 5 Effects of Weathering on Soil Formation

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively