Andalusia PAU Geology and Environmental Sciences common mistakes
Andalusia PAU Geology and Environmental Sciences · Understand the traps and how to avoid them.
When asked to identify a mineral from its physical properties, candidates list the properties (hardness, lustre, cleavage) as separate facts but never commit to a name, or they name a mineral from a single property such as colour alone.
Colour is the most visually obvious property and the easiest to recall, so it dominates the answer, while the diagnostic combination (cleavage pattern, hardness relative to a known reference, streak, reaction with dilute acid) is not systematically applied. Candidates also fear being wrong and hedge by describing instead of concluding.
What to do instead
Adopt a fixed decision routine for every mineral identification: streak first, then hardness against a reference set (fingernail 2.5, copper coin 3.5, steel nail 5.5, glass 5.5, quartz 7), then cleavage or fracture, then special tests (effervescence with dilute HCl for calcite, magnetism for magnetite, taste/solubility for halite). Practise on ten specimens and write the routine out each time until it is automatic.
On a geological map question, candidates read the outcrop pattern and the strike and dip symbols but never reconstruct the three-dimensional structure, so they describe 'layers' or 'folds' without stating the fold axis orientation, the relative age of the units, or the position of the map within a larger structure.
Map interpretation is taught as a separate skill from structural geology, and under time pressure candidates transcribe symbols rather than integrate them. The rule that younging direction plus dip direction defines anticline versus syncline is often memorised but not applied to the actual symbols on the map.
What to do instead
Work every map in a fixed order: (1) list the units in age order from the legend, (2) mark strike and dip on each outcrop, (3) trace the fold axes and classify each fold from the dip directions on its two limbs, (4) draw a cross-section along the specified line before answering any question. Answer the cross-section question first; it forces the 3D reconstruction.
When explaining plate tectonics, candidates describe the Earth's interior as static layers and treat plate movement as driven by 'convection' without naming the mechanism, and they place the asthenosphere, lithosphere and mesosphere at the wrong depths or conflate them with the compositional layers (crust, mantle, core).
Textbook diagrams show compositional and mechanical layering side by side, and candidates merge the two classifications. 'Convection currents' is a phrase learned at school and never upgraded to slab pull, ridge push and mantle drag, so the causal chain is missing.
What to do instead
Build two separate tables: compositional layers (crust, mantle, core with depths and compositions) and mechanical layers (lithosphere, asthenosphere, mesosphere, outer and inner core). Then write one sentence per driving force: slab pull from the negative buoyancy of subducting lithosphere, ridge push from elevated topography at ridges, and mantle drag at the base of the plate. State which dominates.
When asked to classify a rock, candidates give the name without the criteria, or classify a metamorphic rock by its protolith rather than by its texture and mineral assemblage, and they confuse the terms for foliation (slaty, schistose, gneissose) with the rock names.
Rock names are memorised as labels attached to pictures rather than as the output of a classification key based on texture, mineralogy and, for igneous rocks, silica content and grain size. Metamorphic grade is treated as a synonym for depth rather than as a temperature-pressure assemblage.
What to do instead
For each rock, state the three-part justification before the name: texture (grain size, foliation, crystallinity), mineral assemblage, and inferred origin (extrusive/intrusive, clastic/chemical, protolith and grade). Learn index minerals (chlorite, biotite, garnet, staurolite, kyanite, sillimanite) as a grade sequence and place each metamorphic rock on that sequence.
On stratigraphy and palaeontology questions, candidates use fossils as decoration ('this layer contains ammonites') rather than as tools, and they fail to apply the principles of superposition, original horizontality, cross-cutting relationships and faunal succession to determine relative ages of events.
Fossils are learned as a taxonomy exercise (identify the phylum) while the principles of relative dating are learned as separate definitions. Candidates do not practise ordering events in a cross-cutting diagram, so they never connect the two.
What to do instead
For any sequence, list the events in order and justify each step with a named principle. For fossils, always state the biozone, the age range and the environment it indicates, and use index fossils (ammonites, graptolites, trilobites, foraminifera) to correlate. Practise ordering events on diagrams with an unconformity, an intrusion, a fault and a fold, and name the unconformity type (angular, disconformity, nonconformity).
When explaining a natural hazard, candidates describe the phenomenon but omit the hazard-specific variables that determine risk, and they present risk as a single quantity rather than as a function of hazard, exposure and vulnerability.
Hazard and risk are used interchangeably in everyday language, and the exam's environmental-management framing is not applied to the geodynamics content. Candidates also answer the mechanism question instead of the risk question, or vice versa.
What to do instead
Write the definition explicitly at the start of every hazard answer: risk = f(hazard, exposure, vulnerability), and state which factor each management measure reduces. For each hazard, list the controlling variables (for floods: discharge, recurrence interval, land use, impermeability; for landslides: slope angle, lithology, water content, vegetation; for earthquakes: magnitude, depth, distance, site amplification, building codes).
On pollution questions, candidates describe the source of a pollutant but do not trace its pathway, its transformation, or its effect, and they treat air, water and soil pollution with the same generic vocabulary instead of using the specific parameters of each medium.
Pollution is learned as a list of pollutants and their effects, not as a source-pathway-receptor chain. The parameters that make an answer examinable (BOD and COD for water, PM10 and PM2.5, NOx, SO2, ozone and photochemical smog for air, pH, cation exchange capacity and heavy-metal mobility for soil) are not attached to the right medium.
What to do instead
Answer every pollution question as a chain: source, emission, transport and transformation, receptor, effect, and control measure. Attach at least two quantitative parameters to each medium and use them. For soil, distinguish contamination from pollution and explain how pH and organic matter control metal mobility. For water, distinguish oxygen-demanding from eutrophying and from toxic pollution.
When asked about sustainability or environmental management, candidates give a list of generic measures ('recycle', 'raise awareness', 'use renewable energy') without linking them to the specific environmental problem in the question or to the Spanish and Andalusian legal and planning framework.
These questions invite moralising, and candidates substitute attitude for analysis. The legal instruments and the concept of environmental impact assessment are known by name but not by function, so they are not used as the analytical tools they are.
What to do instead
For every management question, name the instrument, its function and its limitation: environmental impact assessment and its stages, protected natural areas and their zoning, integrated water management at river-basin scale, waste hierarchy (prevention, reuse, recycling, recovery, disposal), and the precautionary and polluter-pays principles. Close by stating which indicator would show whether the measure worked.
When describing the atmosphere or hydrosphere, candidates give static descriptive facts (layer names, percentages of gases, ocean names) without the processes that connect them to the lithosphere, such as the water cycle fluxes, the greenhouse effect mechanism, ocean-atmosphere coupling or the role of the biosphere in the carbon cycle.
Physical environment content is learned as geography revision, so the dynamic and quantitative aspects (energy balance, albedo, residence times, fluxes between reservoirs) are skipped. The interactions that the exam explicitly asks about are the part candidates prepare least.
What to do instead
For each sphere, learn the reservoirs and the fluxes between them, with at least one number per flux. Be able to draw the carbon and water cycles from memory with arrows and labels, and explain the greenhouse mechanism as absorption and re-emission of longwave radiation by specific gases, not as 'the atmosphere traps heat'. Link each cycle to a geological process (weathering and carbonate deposition, volcanism as a CO2 source).
When explaining magmatism or metamorphism, candidates describe the rock types produced but not the tectonic setting, the magma source, or the pressure-temperature path, so the answer does not explain why that rock forms where it does.
Igneous and metamorphic petrology are studied as catalogues of rock names, and the link from plate boundary to magma composition (partial melting of peridotite, fractionation, assimilation) or to metamorphic facies is not practised. Candidates also confuse the geothermal gradient with the actual P-T path of a rock.
What to do instead
For every igneous or metamorphic rock, state the tectonic setting, the source material, the melting or metamorphic mechanism, and the P-T conditions. Use the sequence: at divergent boundaries, decompression melting of peridotite gives basaltic magma; at subduction zones, flux melting from released water gives calc-alkaline magmas; at collision zones, crustal thickening gives regional metamorphism with a clockwise P-T path. Draw the P-T diagram with the facies fields and plot the rock on it.