Physical Geology and Earth Processes
What the exam tests
Physical Geology and Earth Processes tests the Earth's layered interior, plate tectonics, earthquakes and volcanism, and the surface processes - weathering, erosion, transport and deposition - driven by running water, wind, glaciers, groundwater and waves. Kerala items commonly use monsoon lateritisation, Western Ghats landslides and coastal erosion as contexts.
Core rules
- Discontinuities: Mohorovičić (crust–mantle), Gutenberg (mantle–core), Lehmann (outer–inner core). Oceanic crust is thin, dense and basaltic; continental crust is thick and granitic.
- Plate boundaries: divergent (mid-ocean ridge), convergent (trench, island arc) and transform (conservative, crust neither created nor destroyed).
- Weathering happens in place; erosion removes and transports. Physical (frost shattering, exfoliation, salt crystallisation), chemical (hydrolysis, oxidation, carbonation) and biological processes act together in Kerala's hot, wet climate.
- Streams cut V-shaped valleys, then meander and build deltas; glaciers cut U-shaped valleys and leave moraines; wind builds barchans; waves cut cliffs and build spits.
Worked example
Surface temperature is 28 °C and the geothermal gradient is 25 °C per km. Temperature at 8 km = 28 + (25 × 8) = 28 + 200 = 228 °C. Multiply the gradient by depth, then add the surface value; the common error is to subtract it or to omit the surface temperature.
Traps
Swapping the Moho and Gutenberg discontinuities. Calling laterite an erosional landform when it is a leached weathering profile. Writing 'erosion' where the question asks for weathering, or describing the rock cycle without naming the process at each arrow.