GEO • SHS 1Term 1WAEC / WASSCE SyllabusFree Trial Topic
The Earth as a Planet & the Earth's Crust
Shape, size, proofs of the Earth's sphericity, rotation and revolution, day and night, seasons, longitudes, standard time, and internal crust structure.
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Real-World Context & Relevance in Ghana
Ghana lies along the Greenwich Meridian (0° Longitude passing through Tema), placing the country in the Greenwich Mean Time (GMT) zone.
Key Syllabus Learning Objectives
- 1Provide scientific proofs verifying the spherical shape of the earth
- 2Distinguish between the effects of earth's rotation and revolution
- 3Calculate international standard time differences using longitudinal degrees
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Comprehensive Syllabus Study Notes
• The Shape of the Earth: An oblate spheroid (slightly flattened at the poles and bulging at the Equator).
• Proofs of Earth's Sphericity:
- Circumnavigation of the earth without falling off an edge.
- Ship's visibility at sea (mast appears before hull when approaching shore).
- Curved circular shadow cast on the moon during lunar eclipses.
- Sunrise and sunset times vary eastward across the globe.
- High-altitude aerial and satellite photographs from space.
• Earth Motions:
- Rotation: Spins on its axis once every 24 hours from west to east; causes day and night, deflections of wind (Coriolis effect), and 1 hour time difference per 15° of longitude.
- Revolution: Orbits the sun in an elliptical path every 365¼ days; causes the four seasons, varying lengths of day and night, and changing midday sun altitude.
• Internal Structure: Crust (Lithosphere: SIAL and SIMA), Mantle (Asthenosphere), and Core (Barysphere: outer liquid, inner solid NIFE - Nickel and Iron).
- The Shape of the Earth: An oblate spheroid (slightly flattened at the poles and bulging at the Equator).
- Proofs of Earth's Sphericity:
- Circumnavigation of the earth without falling off an edge.
- Ship's visibility at sea (mast appears before hull when approaching shore).
- Curved circular shadow cast on the moon during lunar eclipses.
- Sunrise and sunset times vary eastward across the globe.
- High-altitude aerial and satellite photographs from space.
- Earth Motions:
- Rotation: Spins on its axis once every 24 hours from west to east; causes day and night, deflections of wind (Coriolis effect), and 1 hour time difference per 15° of longitude.
- Revolution: Orbits the sun in an elliptical path every 365¼ days; causes the four seasons, varying lengths of day and night, and changing midday sun altitude.
- Internal Structure: Crust (Lithosphere: SIAL and SIMA), Mantle (Asthenosphere), and Core (Barysphere: outer liquid, inner solid NIFE - Nickel and Iron).
Practical Example:
Ghana lies along the Greenwich Meridian (0° Longitude passing through Tema), placing the country in the Greenwich Mean Time (GMT) zone.
Core Takeaway:
Remember the 15° rule: 15° of longitude = 1 hour time difference. Places east are ahead (+); places west are behind (-).
WAEC / WASSCE Examiner Tips
- Remember the 15° rule: 15° of longitude = 1 hour time difference. Places east are ahead (+); places west are behind (-).
Common Candidate Pitfalls & Errors to Avoid
- Believing the Earth turns through one degree in an hour instead of fifteen degrees in an hour, which throws every time calculation out by a factor of fifteen.
- Subtracting the time for a place east of the zero meridian rather than adding it, so the town is given a clock behind Greenwich.
- Confusing local mean time, which changes with longitude, with a standard time zone, which Ghana keeps whole.
- Treating the international date line as an ordinary time-zone boundary and forgetting that the calendar day changes there.
- Using the Earth's diameter where a radius is required when comparing the thickness of the crust with the whole planet.
Topic Mastery Checklist
- Provide scientific proofs verifying the spherical shape of the earth
- Distinguish between the effects of earth's rotation and revolution
- Calculate international standard time differences using longitudinal degrees
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