Earth and space: rocks, weather, climate, solar system and universe
Earth and space covers rocks and the rock cycle, weathering, weather versus climate, and Earth's place in the solar system and universe. The exam rewards explanation rather than naming alone.
Rocks and the rock cycle
Igneous rocks form from cooling magma or lava (basalt, granite). Sedimentary rocks form from compacted sediments (limestone, sandstone) and may contain fossils. Metamorphic rocks form when heat and pressure alter existing rock (marble from limestone, slate from shale). Weathering breaks rock in place (freeze–thaw, acid rain); erosion transports material; deposition lays it down. Soil forms from weathered rock, humus and organisms.
Weather and climate
Weather is the day-to-day state of the atmosphere; climate is the long-term average. Air pressure, temperature, humidity and wind drive weather. The greenhouse effect keeps Earth warm: greenhouse gases absorb and re-emit infrared radiation. Increasing CO₂ from burning fossil fuels enhances this, causing global warming, sea-level rise and more extreme weather.
Earth in space
Day and night come from Earth's rotation (24 hours); seasons come from Earth's 23.5° tilt as it orbits the Sun - not from distance. The Moon orbits Earth roughly every 28 days, producing phases; eclipses occur when the Sun, Earth and Moon line up. The solar system has eight planets; the Sun is a star; a light year is a distance. Evidence for the Big Bang includes redshift and the cosmic microwave background.
Worked example
Explain why Ireland has summer in June even though Earth is farther from the Sun in July. In June the northern hemisphere is tilted towards the Sun, so sunlight strikes at a steeper angle and days are longer, delivering more energy per unit area. Distance is not the cause.
Traps
- Saying seasons are caused by distance from the Sun.
- Confusing lunar phases with eclipses.
- Using 'climate change' to describe a single hot day.