Earth Science: Strata, Weather and Air Masses, Celestial Motion
What this domain tests
This section covers rock layers and their relative ages, the behaviour of air masses that produces Kagoshima's weather, and the motions of Earth and Moon that give day, night, seasons and phases. Questions usually present a sequence or a diagram and ask you to order events or explain a cause.
Geology and strata
Law of superposition: in undisturbed sedimentary rock, lower layers are older. Any feature that cuts across layers - a fault or an igneous intrusion - is younger than the rock it cuts. An unconformity marks missing time removed by erosion. Fossils give relative ages and evidence of past environments. Igneous rock cooled from magma, sedimentary rock formed from compacted deposited grains and may hold fossils, metamorphic rock was altered by heat and pressure.
Weather and air masses
Air moves from high pressure to low pressure; wind is named by where it comes from. Warm air rises, expands and cools, and water vapour condenses at the dew point to form cloud. A cold front brings steep cloud, heavy short showers; a warm front brings gentle prolonged rain. High pressure means sinking air and settled fair weather; low pressure means rising air, cloud and rain. Sea breezes blow onshore by day because land heats faster than water.
Celestial motion
Rotation in 24 hours gives day and night and the apparent daily circling of stars. Revolution in 365¼ days combined with the 23.4° axial tilt gives the seasons. Moon phases come from the changing sunlit portion we see, not from Earth's shadow.
Worked example
A limestone bed with marine fossils lies at the bottom of a cliff, sandstone above it, and a vertical igneous dyke cuts through both. Order from oldest to youngest: limestone, sandstone, dyke. The limestone was deposited first (lowest undisturbed layer), sandstone later on top, and the dyke is youngest because it cuts across both.
Traps that cost marks
Explaining seasons by distance from the Sun instead of axial tilt. Confusing phases with eclipses. Saying high pressure brings storms. Naming wind by where it blows to.