WJEC A-Level Geology F2 Surface and Internal Processes: a deep dive on weathering, erosion, transport, deposition, sedimentary structures and the Earth's internal heat engine

What F2 actually demands

F2 explains how the rock cycle is powered at both ends. At the surface, weathering, erosion, transport and deposition break rock down and rework it into sediment, recording their action in grain texture and sedimentary structures. At depth, the Earth's own heat drives convection, melting and metamorphism. Examiners want you to describe each process with the correct mechanism, to read structures as way-up and environment evidence, and to explain the internal heat engine quantitatively.

This guide ties the three topics of the unit together. Each has a matching dot-point page with practice questions; this overview connects them.

Surface breakdown and transport

Physical weathering (freeze-thaw, exfoliation, thermal expansion, biological action) reduces grain size; chemical weathering (hydrolysis of feldspar to clay, carbonation of limestone, oxidation, dissolution) decomposes the minerals, fastest in warm, wet climates. Erosion removes the products and transport carries them, with abrasion rounding grains (recording distance) and a consistent agent sorting them (recording the transport medium).

Deposition and sedimentary structures

Sediment is deposited where the transport agent loses energy, and the environment sets the grain size, sorting and structures of the rock. Bedding, cross-bedding, graded bedding, ripple marks and desiccation cracks record current direction, energy and exposure, and several act as way-up indicators that reveal the original younging direction even in folded rocks.

The internal heat engine

The Earth's heat comes from radioactive decay and residual heat of formation. The geothermal gradient (about 25 to 30 degrees Celsius per kilometre on average) and heat flow vary with tectonic setting. This heat drives slow mantle convection, which powers plate motion and the deep limb of the rock cycle through melting and metamorphism.

Check your knowledge

Attempt these under timed conditions, then check against the solutions.

1. Distinguish between weathering and erosion. (2 marks)
2. Name the chemical process that weathers feldspar to clay. (1 mark)
3. Explain how graded bedding is used to determine way-up. (2 marks)
4. State the depositional environment suggested by large-scale cross-bedding and excellent sorting in a fossil-free sandstone. (1 mark)
5. Name the two main sources of the Earth's internal heat. (2 marks)
6. State an average value for the geothermal gradient and explain why it varies. (2 marks)