Earth and Space Science
Earth and Space Science
This domain covers Earth materials, the rock cycle, soil, weather and climate, the water cycle, and the solar system. GTLE questions often use local examples - Harmattan, rainy seasons, galamsey, coastal erosion - and ask you to distinguish closely related terms.
Core rules and concepts
- Rocks are igneous (cooled magma/lava), sedimentary (compacted or cemented sediments) or metamorphic (changed by heat/pressure). The rock cycle links them through melting, cooling, weathering, erosion, deposition and metamorphism. Soil forms from weathered rock, organic matter, air and water over long periods.
- Weather is the short-term state of the atmosphere; climate is the long-term pattern. Ghana's seasons are driven mainly by the movement of the Inter-Tropical Convergence Zone (ITCZ) and prevailing winds: moist south-westerlies bring rain, while the dry Harmattan from the north-east brings dust and low humidity.
- The water cycle: evaporation, transpiration, condensation, precipitation, runoff and infiltration. Groundwater is stored in aquifers and can be depleted or polluted.
- Solar system: eight planets orbit the Sun; inner planets are rocky, outer planets are gas/ice giants. Seasons arise from Earth's axial tilt (about 23.5°), not distance from the Sun. Moon phases arise from the changing angle between Earth, Moon and Sun; eclipses occur only when the alignment is near a node because the Moon's orbit is tilted about 5°.
Worked example
Explain why Ghana's southern coast often has two rainy seasons while the north has one. Reasoning: the ITCZ migrates north and south. When it passes over the south, moist south-westerly air rises and condenses, giving rain; the north gets rain when the ITCZ reaches it later. The south can be crossed twice (on the way north and on the return), producing a double maximum, while the north experiences a single wet season. Local relief and distance from the coast modify this pattern.
Traps that cost marks
Saying seasons are caused by Earth's distance from the Sun; confusing weather with climate; calling the Moon's phases Earth's shadow; treating all rocks as permanent; assuming all rain comes from the sea without condensation; mixing up infiltration and runoff.