Earth and Space Science: Earth systems, plates, cycles and sky motions
What this domain tests
Earth and Space Science at Level 1 treats Earth as a system. You need the layered interior and plate tectonics, the rock and carbon cycles, climate change evidence, and the scale and motions behind seasons and Moon phases.
Core rules
- Earth's layers: thin crust, solid mantle, liquid outer core (which generates the magnetic field) and solid inner core. Density increases with depth.
- Plate boundaries: divergent (plates separate, new crust forms), convergent (subduction or collision) and transform (plates slide past). Earthquakes and volcanoes cluster at these boundaries.
- Rock cycle: igneous rock cools from magma or lava; sedimentary rock forms from deposited, compacted material; metamorphic rock forms under heat and pressure. Any type can become any other.
- Carbon cycle: photosynthesis removes CO₂; respiration, combustion and decay release it; oceans and limestone store it.
- Seasons: caused by the 23.5° axial tilt, not by distance from the Sun. The Southern Hemisphere has summer when the South Pole tilts toward the Sun.
- Moon phases: produced by the changing angle between Earth, Moon and Sun - the Moon does not change shape.
Worked example
Magnetic stripes show seafloor 300 km from a ridge formed 3.0 million years ago. Rate = distance ÷ time = 300 000 m ÷ 3 000 000 yr = 0.10 m yr⁻¹, which is 10 cm yr⁻¹. Because matching stripes occur on both sides of the ridge, this figure is the half-spreading rate; the full spreading rate is about 20 cm yr⁻¹.
Traps that cost marks
- Claiming summer happens because Earth is nearer the Sun.
- Reversing the rock cycle, or calling melted rock sedimentary.
- Confusing the natural greenhouse effect with the enhanced greenhouse effect.
- Dividing in km and reporting a rate in cm without converting.
- Explaining phases as Earth's shadow - that is a lunar eclipse.