Earth Science: Geology, Meteorology and Astronomy
Earth science questions connect internal and external Earth processes with atmospheric circulation and astronomical observation. Expect diagram interpretation, time and distance calculations, and explanations that link cause to observable evidence.
Core rules
- Plate tectonics: divergent, convergent and transform boundaries produce characteristic earthquakes, volcanoes and topography. P waves arrive before S waves; S waves do not travel through liquids.
- Rocks: igneous, sedimentary and metamorphic types are classified by origin; superposition and cross-cutting relationships establish relative age.
- Atmosphere: pressure falls with altitude; air moves from high to low pressure and is deflected by the Coriolis effect; fronts mark boundaries between air masses.
- Astronomy: Kepler's third law relates orbital period and radius; apparent magnitude depends on distance as well as luminosity; seasons arise from axial tilt, not distance from the Sun.
- Radioactive dating uses half-life: after n half-lives, the parent fraction is (1/2)ⁿ.
Worked example
An earthquake records a 6.0 s interval between the first P and S arrivals. Taking vP = 6.0 km/s and vS = 3.5 km/s, let distance be d. Then d/3.5 − d/6.0 = 6.0. Multiplying by 21 gives 6d − 3.5d = 126, so 2.5d = 126 and d = 50.4 km. The reasoning assumes straight-line propagation and constant speeds, which should be stated.
Traps
Confusing focus with epicenter, reading apparent magnitude as luminosity, reversing the Coriolis deflection between hemispheres, and halving a parent isotope repeatedly without counting half-lives lose marks. In relative dating, a cross-cutting feature is younger than the rocks it cuts.