Physical Geography: Earth's structure, plate tectonics, rocks and landforms
What the domain tests
This domain examines the Earth's internal structure, plate tectonics, the rock cycle and the processes that shape landforms. Questions often ask you to identify layers, explain boundary processes, classify rocks and link weathering, erosion and deposition to named landscapes, including Namibian examples.
Core rules and concepts
- The Earth has a crust, mantle, outer core and inner core; the lithosphere is the rigid crust plus upper mantle, and it is broken into plates.
- Convection currents in the mantle move plates. At divergent boundaries plates separate, creating ridges and rift valleys. At convergent boundaries plates collide, producing subduction zones, trenches, fold mountains or volcanic arcs. At transform boundaries plates slide, causing earthquakes.
- The rock cycle links igneous rocks (cooled magma), sedimentary rocks (compacted and cemented sediments) and metamorphic rocks (changed by heat and pressure).
- Weathering breaks rock in place; erosion removes and transports material; deposition lays it down. Landforms result from the balance between these processes.
Worked example
A map shows a deep ocean trench beside a chain of volcanic islands. Explain the boundary. Reasoning: a trench indicates subduction, so one oceanic plate is denser and sinks beneath another. Melting of the descending plate produces magma, which rises to form a volcanic island arc. The boundary is convergent, oceanic–oceanic. Naming the process, plate type and resulting landforms earns the marks.
Traps that cost marks
- Confusing weathering with erosion: weathering does not transport material.
- Saying all convergent boundaries make fold mountains; oceanic–oceanic convergence makes island arcs and trenches.
- Mixing up the mantle and the core, or calling the lithosphere the whole mantle.
- Describing a rock as sedimentary without giving the compaction/cementation process.