Physical Geography: Earth's Interior, Landforms and Geomorphic Processes
What this domain tests
Physical geography questions here test seismic evidence for Earth's layering, plate-tectonic controls on landforms, and the distinction between weathering, erosion and deposition.
Core rules
- Crust, mantle, outer core (liquid), inner core (solid). Discontinuities: Mohorovičić (Moho) at crust–mantle, Gutenberg at mantle–outer core, Lehmann at outer–inner core.
- P-waves are longitudinal and pass solids, liquids and gases; S-waves are transverse and cannot pass liquids. The S-wave shadow zone begins at about 103° from the epicentre, proving a liquid outer core.
- Endogenic processes build relief: folding, faulting, volcanism, plate convergence. Exogenic processes wear it down: weathering, mass movement, erosion, transport, deposition.
- Divergent margins create ridges; convergent margins create trenches, island arcs and fold mountains; transform margins create faults.
Worked example
A station 120° from an epicentre records P-waves but no S-waves. Reasoning: the ray path to 120° passes through the outer core. S-waves cannot propagate through liquid, so they are not recorded. P-waves slow and refract at the core boundary, producing the P-wave shadow zone between about 103° and 142°.
Traps
Focus (hypocentre) is underground; epicentre is at the surface. P-waves arrive first but do not always cause the most damage. Weathering breaks rock in place; erosion removes it. The Moho is the crust–mantle boundary, not the lithosphere–asthenosphere boundary.