NCEA Level 2 Earth and Space Science cheat sheet

Earth's internal structure: crust (5–70 km thick), mantle (to ~2900 km depth), liquid outer core, solid inner core; the iron-rich core generates the magnetic field via the geodynamo.

Plate tectonics: lithospheric plates move 1–10 cm/yr over the asthenosphere; divergent boundaries create new crust, convergent boundaries destroy it (subduction) or build mountains, transform boundaries slide past.

Seafloor spreading evidence: symmetric magnetic striping either side of mid-ocean ridges, youngest crust at ridges, matching continental margins and fossil correlations.

Rock cycle: igneous (crystallised magma/lava), sedimentary (compaction and cementation of deposited grains), metamorphic (heat and pressure without melting); any rock type can transform into any other.

Relative dating rules: superposition (older below), cross-cutting relationships (faults/intrusions younger than what they cut), inclusions older than host rock; index fossils and key beds correlate strata.

Absolute dating: radiometric decay uses half-life T½; after n half-lives the parent fraction remaining is (1/2)^n. Carbon-14 suits organic material up to ~50,000 years; uranium-lead suits ancient rocks.

Earthquakes and volcanoes: seismic waves (P primary, S secondary, surface waves) reveal internal layers; S-waves cannot pass liquid, evidencing the liquid outer core. Volcano type relates to magma viscosity and setting.

Landscape processes: weathering breaks rock in place, erosion transports it, deposition builds landforms; rivers, glaciers, wind and waves each produce characteristic landform suites.

NZ plate setting: the Pacific Plate subducts beneath the Australian Plate along the Hikurangi margin and Alpine Fault marks a transform boundary - explaining frequent earthquakes, volcanism and uplift.

Earth-Sun-Moon geometry: seasons arise from the 23.5° axial tilt, not distance from the Sun; hemispheres receive opposite seasons.

Moon phases: the Moon orbits Earth in ~27.3 days (sidereal) but the phase cycle is ~29.5 days (synodic); phases depend on the Sun-Earth-Moon angle, with new moon between Sun and Earth and full moon opposite.

Eclipses: solar eclipse requires new moon with Moon near a node (aligned Sun-Moon-Earth); lunar eclipse requires full moon with Earth between Sun and Moon; nodal tilt makes eclipses rare.

Tides: mainly caused by the Moon's gravitational gradient, with spring tides at new and full moon (aligned forces) and neap tides at quarter phases (perpendicular forces); two high tides per ~24 h 50 min.

Solar System structure: four inner terrestrial planets, asteroid belt, four outer gas/ice giants, Kuiper Belt, Oort Cloud; orbits are ellipses described by Kepler's laws (equal areas in equal times, P² ∝ a³).

Stars: apparent brightness depends on luminosity and distance; colour indicates surface temperature (blue hottest, red coolest); the Hertzsprung-Russell diagram plots luminosity against temperature.

Stellar life cycle: nebula → protostar → main sequence (hydrogen fusion) → red giant/supergiant → planetary nebula plus white dwarf (low mass) or supernova plus neutron star/black hole (high mass).

Light evidence: emission and absorption spectra identify elements; redshift of galaxy spectra indicates recession, supporting an expanding universe and the Big Bang model.

Scale: one light-year ≈ 9.46 × 10¹² km; astronomical unit (AU) ≈ 1.5 × 10⁸ km; distances in the universe are measured in parsecs and light-years, not kilometres.

Carbon cycle: reservoirs are atmosphere (CO₂), biosphere (organic carbon), oceans (dissolved CO₂ and carbonate), lithosphere (fossil fuels and limestone); fluxes include photosynthesis, respiration, combustion and weathering.

Greenhouse effect: gases such as CO₂, CH₄, H₂O and N₂O absorb outgoing infrared radiation and re-emit it, warming the lower atmosphere; the effect is natural but enhanced by human emissions.

Climate vs weather: climate is long-term average and variability (typically 30 years); weather is short-term atmospheric state; proxies such as ice cores, tree rings and sediments reconstruct past climate.

Ocean circulation: thermohaline circulation is driven by temperature and salinity differences; warm surface currents (e.g. Gulf Stream) and cold deep currents redistribute heat globally.

Albedo and feedbacks: ice and snow have high albedo and reflect solar energy; melting ice reduces albedo (positive feedback); warmer air holds more water vapour (another positive feedback).

Energy balance: incoming solar radiation must balance outgoing longwave radiation plus reflection; imbalance changes global mean temperature. Insolation varies with latitude, season and surface type.

Human impacts: burning fossil fuels and deforestation raise atmospheric CO₂; consequences include sea-level rise from thermal expansion and ice melt, ocean acidification, and shifted weather patterns.

Earth's spheres: atmosphere (gas), hydrosphere (water), lithosphere (rock), biosphere (life) and cryosphere (ice) interact - e.g. volcanic ash affects climate, which affects ecosystems.

Mitigation vs adaptation: mitigation reduces causes (renewable energy, carbon sinks, efficiency); adaptation reduces harm (sea walls, drought-resistant crops, flood planning).