Physical Geography: Processes, Systems and Quantitative Interpretation
Physical Geography in MATSEC AM Geography examines the processes that shape the lithosphere, atmosphere, hydrosphere and biosphere, and your ability to interpret field and graph data. Questions often require a process explanation plus a quantitative check.
Core rules and concepts
- Tectonic activity is driven by mantle convection; divergent, convergent and transform boundaries produce distinctive landforms and hazard patterns.
- Weathering is in situ disintegration or decomposition; erosion is the removal and transport of material. Do not use the terms interchangeably.
- River systems tend toward a graded long profile: concave-up, with downstream fining of load and increasing discharge.
- Coastal sediment cells link erosion, transport and deposition; intervention in one part of a cell can shift erosion elsewhere.
- The hydrological cycle is a closed global system but an open local catchment system; inputs, stores, flows and outputs must balance over time.
- Climate reflects latitude, altitude, continentality, ocean currents and pressure belts; ecosystems respond through succession and nutrient cycling.
Worked example
A river has width 15 m, mean depth 3.0 m and mean velocity 1.2 m/s. Find discharge. If velocity doubles while the cross-section stays unchanged, find the new discharge and state one geomorphological consequence.
Area = 15 × 3.0 = 45 m². Discharge Q = A × v = 45 × 1.2 = 54 m³/s. New Q = 45 × 2.4 = 108 m³/s. Reasoning: discharge is volume per second, so units must be m³/s, not m/s. The higher velocity raises competence and capacity, so the river can transport coarser and more sediment, increasing erosion or deposition downstream depending on gradient.
Traps that cost marks
- Confusing discharge with velocity: Q = A × v, so a wide shallow channel can carry more water than a narrow deep one.
- Describing a landform without naming the process and scale (e.g. “the sea erodes” instead of hydraulic action, abrasion, attrition or solution).
- Treating groundwater as instantly renewable; recharge rates can be far below abstraction rates.
- Reading a climograph as temperature bars and precipitation line, or ignoring the axis units.
- Assuming all hazards are controlled by hazard magnitude alone; vulnerability and exposure also matter.