Catalonia PAU Geology & Env Sci common mistakes
Catalonia PAU Geology & Env Sci · Understand the traps and how to avoid them.
When asked to identify a plate boundary from a description (e.g. a deep-ocean trench paired with a volcanic arc and shallow-to-deep earthquakes), the candidate labels it a 'divergent boundary' or 'transform fault' because they fixate on the word 'trench' or 'fault' rather than assembling all three clues together.
Candidates memorise boundary names as isolated labels and never build a decision checklist that links topography, seismicity distribution and magmatic style. Under exam pressure the first familiar keyword triggers a premature answer.
What to do instead
Before answering, write a three-row table on the answer sheet: topography / earthquake depth pattern / magma type. Fill each row from the stem, then match the completed pattern to the boundary type. Practise with ten mixed descriptions until the table takes under a minute.
In questions on metamorphism, the candidate states that a rock 'melts' to become a higher-grade metamorphic rock, or claims that increasing pressure alone produces migmatites, confusing the metamorphic and igneous fields.
The rock cycle is often learned as a simple loop with arrows, which hides the fact that metamorphism is a solid-state process and that melting marks the boundary into igneous territory. The distinction is rarely tested in class, so it stays fuzzy.
What to do instead
Memorise the boundary explicitly: metamorphism = solid-state recrystallisation; melting begins only when temperature exceeds the wet solidus, producing migmatite then magma. For each metamorphic facies you revise, state its approximate P-T field and note whether melting is possible there.
When explaining coastal or fluvial landforms, the candidate describes erosion as the whole process and omits transport and deposition, so a question about a delta, spit or alluvial fan is answered only in terms of 'the sea wears away the rock'.
Weathering, erosion, transport and sedimentation are taught together and blur into one idea. Candidates also default to the most visually dramatic process (erosion) and forget that the landform in the stem is constructional, not excavation.
What to do instead
For every landform question, force a four-step chain: source of material, weathering, agent and direction of transport, site and cause of deposition. If the landform is depositional (delta, spit, fan, dune, moraine), the answer must name the depositional mechanism and the reason energy dropped.
The candidate treats soil as inert 'dirt' and answers soil-profile or soil-fertility questions by listing only parent rock, ignoring climate, organisms, topography and time, and omitting horizon differentiation (O, A, B, C).
Soil is often covered briefly at the end of the external-geodynamics unit, so it is revised as a definition rather than as a system with five forming factors. Candidates also confuse soil texture (particle size) with structure (aggregation).
What to do instead
Learn the five soil-forming factors as a checklist (climate, organisms, relief, parent material, time) and the horizon sequence as a diagram you can redraw from memory. Practise distinguishing texture from structure with three concrete examples each.
On relative-dating questions the candidate applies superposition and cross-cutting relationships but forgets that a fault or intrusion is younger than everything it cuts, and older than nothing it does not cut, producing an inverted sequence.
Principles are memorised as separate slogans rather than as an ordered procedure. Candidates also skip the step of identifying which contacts are depositional and which are intrusive or faulted before ordering events.
What to do instead
Use a fixed routine: (1) mark every contact as depositional, intrusive, fault or unconformity; (2) apply superposition within each undisturbed package; (3) place cross-cutting features after the units they cut; (4) place unconformities between the youngest folded unit and the oldest overlying bed. Write the numbered event list before choosing an option.
The candidate uses fossils as simple 'age labels' without recognising facies control, so they claim a specific ammonite zone proves a specific environment, or use a benthic assemblage to correlate across an ocean basin.
Index fossils are taught as markers of time, and the parallel idea that organisms are also environmental indicators is not separated clearly. Candidates therefore over-extend a single fossil's meaning.
What to do instead
For each fossil group you revise, record two separate facts: its time range (biostratigraphic value) and its facies preference (pelagic vs benthic, reef vs deep water). In answers, state which of the two you are using and why the other does not apply.
When asked to identify a mineral or rock, the candidate names it from colour alone, calling any dark fine-grained rock 'basalt' and any shiny grey mineral 'galena', without testing hardness, cleavage, lustre or acid reaction.
Colour is the most salient property and the easiest to remember, so it dominates recall. Candidates also lack practice in applying diagnostic tests systematically under time pressure.
What to do instead
Adopt a fixed identification order: lustre, hardness (fingernail, coin, steel, glass), cleavage versus fracture, colour and streak, then special tests (HCl, magnetism). For rocks, decide texture first (phaneritic, aphanitic, foliated, clastic grain size), then composition. Learn five minerals and five rocks to this full standard.
On climate questions the candidate explains the seasons by Earth's varying distance from the Sun, or attributes the greenhouse effect to the ozone layer, mixing up two distinct atmospheric mechanisms.
Everyday phrases ('closer to the Sun in summer', 'the ozone hole causes warming') circulate widely and feel intuitive. The correct mechanisms involve axial tilt and infrared absorption by specific gases, which require a mental model candidates rarely rehearse.
What to do instead
Write out the two mechanisms in one sentence each and keep them side by side: seasons = axial tilt changing solar angle and day length; greenhouse effect = certain gases absorb outgoing long-wave radiation. State explicitly that ozone absorbs ultraviolet and is a separate issue, and that distance varies little and affects both hemispheres oppositely.
In hydrology questions the candidate treats groundwater and surface water as unrelated reservoirs, so they explain a falling water table as 'less rain on the river' and ignore recharge, infiltration, aquifer type and the base-flow connection.
The water cycle is drawn as a closed loop of arrows, which makes the stores look static and the links abstract. Candidates also conflate porosity with permeability and confined with unconfined aquifers.
What to do instead
Redraw the cycle with named stores and fluxes, then add the groundwater link: infiltration, recharge area, water table, base flow to rivers. Learn the porosity/permeability distinction and the confined/unconfined distinction with one real example each, and use them explicitly in answers.
On environmental-impact and risk questions the candidate lists generic 'pollution' or 'destruction of habitat' without quantifying the pressure, naming the affected receptor, or proposing a monitoring and mitigation measure, so the answer earns partial credit at best.
These questions look like opinion prompts, so candidates answer in generalities. They also confuse prevention, mitigation and compensation, and rarely link a hazard to exposure and vulnerability to produce risk.
What to do instead
Use a fixed four-part structure for every impact or risk answer: pressure (with magnitude or rate), receptor and pathway, consequence, and response (prevention, mitigation or compensation, plus an indicator to monitor). For risk, always state hazard x exposure x vulnerability and name one land-use planning measure.