Earth and Space Science
Domain 2: Earth and Space Science
This domain covers Earth's interior and plate tectonics, rocks and surface processes, the hydrologic cycle, weather and climate, and the Earth-Sun-Moon system. Questions ask you to interpret rock sequences, maps, and astronomical diagrams and to explain observable phenomena.
Earth's interior and plate tectonics
Earth has a solid inner core, liquid outer core, mantle, and crust. Convection in the mantle drives plate motion. Divergent boundaries create new crust (mid-ocean ridges, rift valleys); convergent boundaries produce subduction, trenches, volcanoes, and mountains; transform boundaries produce earthquakes. Oceanic crust is denser than continental crust and subducts.
Rocks, weathering, and erosion
The rock cycle links igneous, sedimentary, and metamorphic rocks. Igneous rocks form from cooling magma or lava; sedimentary rocks form from compaction and cementation of sediments; metamorphic rocks form under heat and pressure. Weathering breaks rock in place; erosion transports sediment. The law of superposition states that undisturbed sedimentary layers are oldest at the bottom.
Earth-Sun-Moon system
Earth's 23.5° axial tilt causes seasons, not distance from the Sun. The Moon's phases result from the changing angle between Earth, Moon, and Sun; the Moon does not emit its own visible light. Solar eclipses occur at new moon; lunar eclipses at full moon. Spring tides occur at new and full moons; neap tides at quarter moons.
Worked example
A student finds undisturbed sedimentary layers: the bottom layer contains a trilobite fossil; the middle layer contains a dinosaur bone; the top layer contains a horse tooth. Which is oldest? Reasoning: In undisturbed sedimentary rock, superposition places the bottom layer oldest. The trilobite is therefore oldest, the dinosaur bone intermediate, and the horse tooth youngest. This is relative dating; it gives order, not absolute ages. Radiometric dating would be needed for numerical ages.
Traps that cost marks
Do not explain seasons by Earth's distance from the Sun. Do not confuse weathering with erosion. Do not say the Moon makes its own light. Do not confuse a new moon with a solar eclipse; alignment must be precise. Do not treat index fossils as age numbers; they indicate relative age.