Shape & Size of the Earth

Grade 10 · Geography

Semester 1 | Period 1 | Week 3

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Subject: Geography

Semester: 1

Period: 1

Week: 3

School Name: ___________________________
Teacher’s Name: _________________________
Subject: Geography
Grade Level: Grade 10
Date: ____________
Week & Period: Week 3, Period 1
Lesson Duration: 45 minutes

Topic: Shape & Size of the Earth

Sub-Topics:

  1. Dimensions of the Earth
    • Equatorial circumference, polar circumference, radius, surface area.
    • Flattening at the poles.
  2. Proof of the Earth’s Spherical Shape
    • Historical proofs (Aristotle, explorers).
    • Scientific proofs (satellite pictures, horizon, lunar eclipse, time zones, circumnavigation).

 

Learning Objectives

By the end of the lesson, students should be able to:

  1. State the dimensions of the Earth (circumference, radius, area).
  2. Explain why the Earth is not a perfect sphere but an oblate spheroid.
  3. List and explain at least 3 proofs that the Earth is spherical.
  4. Relate the Earth’s shape to day/night and navigation.

 

Previous Knowledge

Students already know:

  • The Earth is one of the 8 planets in the solar system.
  • The moon is spherical and influences tides (Week 2).

 

Instructional Materials

  • Globe
  • Chalkboard/whiteboard drawings
  • Charts showing Earth’s dimensions and shape
  • Pictures of Earth from satellites

 

Lesson Development – ABC Model

A – Anticipation (Warm-up / Starter)

Time: 5–10 minutes

Activity:
Teacher asks:

  • “Is the Earth flat or round?”
  • “When you look at the horizon, what do you observe?”
  • “Why do ships disappear bottom-first when moving away on the ocean?”

Teacher’s Role:

  • Engage students in a debate (flat vs. round Earth).
  • Display a globe and ask students to compare it to what they see around them.

Learner’s Role:

  • Share opinions and observations.
  • Answer warm-up questions.
  • Observe the globe and identify visible features.

 

B – Building Knowledge (Main Lesson Body)

Time: 25–30 minutes

Teacher’s Role:

  1. Explain the Dimensions of the Earth
    • Equatorial circumference: 40,075 km.
    • Polar circumference: 40,008 km.
    • Equatorial radius: 6,378 km.
    • Polar radius: 6,357 km.
    • Earth’s surface area: about 510 million km².
    • Earth is an oblate spheroid (slightly flattened at the poles and bulging at the equator).
  2. Proof of the Spherical Shape of the Earth
    • Ships disappear bottom-first over the horizon.
    • Different constellations are seen from different parts of the world.
    • During a lunar eclipse, Earth casts a round shadow on the moon.
    • Time difference: When it is day in Africa, it is night in America.
    • Circumnavigation: Magellan’s voyage proved Earth is round.
    • Satellite photographs show a round Earth.

 

Learners’ Activities:

  • Copy notes into notebooks.
  • Observe globe and diagrams.
  • Take part in discussion and group classification of proofs into scientific vs. historical.
  • Answer oral questions posed by teacher.

 

Assessment Checks:

  • Quick drill: “Is Earth a perfect sphere? Why or why not?”
  • Individual exercise: Write down 3 proofs that Earth is spherical.

 

Notes (Expanded & Detailed):

  1. Dimensions of the Earth
    • Equatorial circumference = 40,075 km.
    • Polar circumference = 40,008 km.
    • Surface area = 510 million km² (71% water, 29% land).
    • Shape = oblate spheroid (flattened at poles, bulging at equator).
  2. Proofs of Spherical Shape
    • Ships disappearing over horizon.
    • Round shadow of Earth during lunar eclipse.
    • Different stars/constellations visible in northern vs. southern hemisphere.
    • Time zones vary across the world.
    • Sailors and explorers (e.g., Magellan) circumnavigated the Earth.
    • Satellite images confirm Earth’s roundness.

 

C – Consolidation (Conclusion & Assessment)

Time: 5–10 minutes

Summary:

  • The Earth is not flat but spherical in shape.
  • Exact measurements show it is an oblate spheroid.
  • Historical and modern evidence prove Earth’s roundness.

Evaluation Method:
Students answer orally:

  1. State the equatorial circumference of Earth.
  2. Why is Earth called an oblate spheroid?
  3. Mention 2 scientific proofs of Earth’s spherical shape.

 

Assignment:

  1. Draw a neat diagram of Earth showing equator, poles, and bulge.
  2. Write short notes on any 3 proofs of Earth’s spherical shape.
  3. Research: What role did Ferdinand Magellan play in proving Earth’s shape?

 

Differentiation / Inclusive Strategies

  • Struggling Learners: Provide simplified diagrams of Earth and step-by-step notes.
  • Advanced Learners: Research how satellites measure Earth’s shape.
  • Students with Disabilities: Use tactile globes or raised diagrams for better understanding.

 

Teacher’s Reflection (After Class)

  • What worked well? ___________________________________________
  • What needs improvement? _____________________________________
  • Students’ engagement level: □ High □ Medium □ Low
  • Next steps: Provide a quiz to reinforce Earth’s dimensions.