Valencian Community PAU Geology and Environmental Sciences cheat sheet

Earth's interior divisions by composition: crust (continental ~30-70 km, oceanic ~5-10 km), mantle (to ~2900 km depth), core (Fe-Ni, outer liquid, inner solid).

Mechanical layering: lithosphere (crust + rigid upper mantle, ~100 km), asthenosphere (partially molten, low velocity zone), mesosphere, outer and inner core.

Seismic evidence: P waves (longitudinal, travel through solids and liquids) refract at the 2900 km discontinuity (Gutenberg); S waves (transverse) cannot pass the liquid outer core, creating the S-wave shadow zone beyond 103°.

Moho discontinuity separates crust from mantle; Lehmann discontinuity marks the inner-core boundary; density increases with depth (crust ~2.7-3.0 g/cm³, core ~13 g/cm³).

Geothermal gradient averages ~25-30 °C/km in the crust; heat flow comes from radioactive decay and primordial heat, driving convection.

Isostasy: Airy model (crustal roots, thicker crust floats higher) and Pratt model (density differences); post-glacial rebound demonstrates isostatic adjustment.

Earth's magnetic field is generated by the geodynamo in the liquid outer core; palaeomagnetic reversals recorded in oceanic basalts support seafloor spreading.

Gravity anomalies: positive over dense/mafic bodies, negative over low-density or subsurface voids; used to infer subsurface structure.

Lithospheric plates move 1-10 cm/yr; evidence: continental fit, matching fossils and strata (e.g. Glossopteris, Karoo), palaeoclimate indicators, palaeomagnetism and seafloor magnetic stripes.

Divergent boundaries: mid-ocean ridges (new oceanic crust, normal faults, shallow earthquakes) and continental rifts (East African Rift).

Convergent boundaries: ocean-ocean (island arcs), ocean-continent (Andean-type arc, compressional folding), continent-continent (Himalayan-type collision, no volcanism).

Transform boundaries: horizontal shear, strike-slip faults (San Andreas); lithosphere neither created nor destroyed.

Wadati-Benioff zones: inclined seismic zones marking subducting slabs, reaching ~700 km depth; deep earthquakes only occur in cold subducting slabs.

Hotspots (Hawaii, Iceland) produce intraplate volcanism; the age progression of seamounts tracks plate motion direction.

Wilson cycle: continental rifting, ocean opening, subduction, collision and suturing; recorded by ophiolites (obducted oceanic lithosphere).

Ridge push and slab pull are the main driving forces; mantle convection provides the underlying energy.

Magma types: basaltic (mafic, ~50% SiO₂, high T ~1200 °C, low viscosity), andesitic (intermediate), rhyolitic (felsic, ~70% SiO₂, lower T, high viscosity, explosive).

Bowen's reaction series: olivine → pyroxene → amphibole → biotite (discontinuous) and Ca-plagioclase → Na-plagioclase (continuous), then K-feldspar, muscovite, quartz.

Igneous textures reflect cooling rate: phaneritic (slow, intrusive), aphanitic (fast, extrusive), porphyritic (two-stage), vitreous (rapid quench), pyroclastic (explosive).

Intrusive forms: batholith, stock, laccolith, sill (concordant), dyke (discordant), volcanic neck; extrusive forms: lava flows, domes, pyroclastic deposits.

Metamorphic agents: heat, pressure (lithostatic and directed), and chemically active fluids; metamorphism is solid-state (no melting).

Metamorphic types: contact/thermal (around plutons, hornfels), regional/dynamothermal (orogenic belts, foliated rocks), dynamic (fault zones, mylonite), burial, hydrothermal.

Foliated sequence for pelitic rocks with increasing grade: slate → phyllite → schist → gneiss; non-foliated: quartzite (from sandstone), marble (from limestone), hornfels.

Index minerals (chlorite, biotite, garnet, staurolite, kyanite, sillimanite) define metamorphic zones and isograds; facies reflect P-T conditions.

Stratigraphic principles: superposition, original horizontality, lateral continuity, cross-cutting relationships, inclusions, faunal succession; unconformities (angular, disconformity, nonconformity) mark gaps.

Relative dating uses lithostratigraphy, biostratigraphy (index fossils: wide distribution, short time range) and event stratigraphy; absolute dating uses radiometric decay (t½ = ln2/λ).

Common radiometric systems: ¹⁴C (~5,730 yr, organic material <50 ka), K-Ar and Ar-Ar (volcanic rocks), Rb-Sr, U-Pb (zircon, oldest rocks), Sm-Nd.

Geological time scale: Hadean, Archaean, Proterozoic (Precambrian ~88% of Earth history), then Phanerozoic: Palaeozoic (Cambrian-Ordovician-Silurian-Devonian-Carboniferous-Permian), Mesozoic (Triassic-Jurassic-Cretaceous), Cenozoic (Palaeogene, Neogene, Quaternary).

Major events: origin of life ~3.8 Ga, Great Oxidation Event ~2.4 Ga, Cambrian explosion ~541 Ma, end-Permian extinction ~252 Ma (~90% species), K-Pg extinction 66 Ma (Chicxulub impact, iridium anomaly).

Fossilisation requires rapid burial, hard parts and anoxic conditions; preservation types include permineralisation, moulds/casts, amber, trace fossils and carbon films.

Biostratigraphic correlation uses biozones; chronostratigraphic units (system, series, stage) correspond to geochronological units (period, epoch, age).

Palaeoenvironmental reconstruction uses facies analysis, sedimentary structures, isotopes (δ¹⁸O for temperature, δ¹³C for carbon cycle) and palaeomagnetism.

Weathering types: physical (freeze-thaw, salt crystallisation, thermal expansion, unloading), chemical (hydrolysis, oxidation, carbonation, dissolution) and biological; climate controls the dominant type (hydrolysis in humid tropics, frost shattering in cold zones).

Karst: dissolution of limestone by CO₂-charged water; landforms include lapies, dolines, poljes, caves, stalactites/stalagmites, sinkholes.

Erosion agents: water, wind, ice, gravity and waves; transport modes: traction, saltation, suspension, solution; competence depends on velocity, capacity on discharge.

Fluvial landforms: V-shaped valleys, meanders, oxbow lakes, floodplains, terraces, alluvial fans, deltas; Hjulström curve relates erosion/deposition to grain size and velocity.

Glacial processes: plucking and abrasion produce U-shaped valleys, cirques, arêtes, moraines, drumlins, erratics, till and varves; periglacial features include permafrost and patterned ground.

Aeolian landforms: dunes (barchan, transverse, longitudinal/linear, star), loess, yardangs, ventifacts; wind sorts fine material better than water.

Coastal processes: wave refraction, longshore drift, cliffs, wave-cut platforms, spits, tombolos, barrier islands, beaches and dunes.

Sedimentary rocks: clastic (conglomerate, sandstone, shale), chemical (limestone, evaporites, chert) and organic (coal); structures include cross-bedding, graded bedding, ripple marks and mudcracks indicating environment.

Mineral definition: naturally occurring, inorganic, crystalline solid with definite chemical composition; identification by hardness (Mohs 1-10), lustre, cleavage, streak, colour, density, acid reaction.

Silicate structures: nesosilicates (olivine, garnet), inosilicates (pyroxene, amphibole), phyllosilicates (mica, clay), framework (quartz, feldspar); non-silicates include carbonates, sulphides, oxides, halides.

Igneous classification by silica content and mineralogy: ultramafic (peridotite), mafic (gabbro/basalt), intermediate (diorite/andesite), felsic (granite/rhyolite).

Sedimentary classification by grain size: gravel >2 mm, sand 0.0625-2 mm, silt 0.004-0.0625 mm, clay <0.004 mm (Udden-Wentworth scale).

Metamorphic rock identification uses foliation and index minerals; parent rock (protolith) can often be inferred (limestone → marble, sandstone → quartzite).

Energy resources: coal (peat → lignite → bituminous → anthracite with increasing rank), oil and gas in traps (anticline, fault, salt dome), uranium, geothermal.

Metallic ores: sulphides (pyrite, chalcopyrite, galena, sphalerite), oxides (hematite, magnetite, bauxite), native elements; gangue is the non-economic fraction.

Industrial rocks: limestone for cement, gypsum for plaster, clays for ceramics, aggregates; reserves are economically extractable, resources are not yet proven.

Risk = hazard × exposure × vulnerability; hazard is the probability of a damaging event, vulnerability the susceptibility of exposed elements.

Earthquake magnitude (Richter, moment magnitude Mw) measures energy released (logarithmic); intensity (Mercalli/EMS-98) measures observed effects and damage, decreasing with distance from the epicentre.

Seismic hazard assessment uses historical seismicity, fault mapping, recurrence intervals, and probabilistic ground-motion models; building codes and microzonation reduce vulnerability.

Volcanic hazards: lava flows, pyroclastic flows, ash fall, lahars, tsunamis, gases; VEI 0-8 classifies explosivity; monitoring uses seismographs, tiltmeters, gas and thermal sensors.

Mass movements classified by material and movement type: falls, slides (rotational/translational), flows (debris flow, mudflow), creep; triggered by rainfall, earthquakes, slope steepening and vegetation loss.

Slope stability depends on shear strength versus shear stress; the factor of safety FS = resisting forces / driving forces; FS > 1 indicates stability.

Flood mitigation: dams and reservoirs, levees, channelisation, retention basins, reforestation, floodplain zoning, flood-risk maps (return period T and probability P = 1/T per year).

Tsunami warning relies on seismic detection, sea-level buoys (DART) and rapid evacuation plans; coastal hazard maps define inundation zones.

Atmospheric layers: troposphere (0-12 km, temperature decreases, weather occurs), stratosphere (ozone layer, temperature increases), mesosphere, thermosphere, exosphere; pressure decreases exponentially.

Composition of dry air: N₂ ~78%, O₂ ~21%, Ar ~0.93%, CO₂ ~0.04%; water vapour varies and is the main natural greenhouse gas.

Greenhouse effect: gases absorb outgoing infrared radiation; key absorbers are H₂O, CO₂, CH₄, N₂O, O₃ and CFCs; without it Earth's mean surface temperature would be about -18 °C instead of +15 °C.

Global circulation: Hadley, Ferrel and Polar cells; trade winds, westerlies, polar easterlies; Coriolis deflection; ITCZ, jet streams, subtropical anticyclones.

Climate types follow Köppen classification (A tropical, B arid, C temperate, D continental, E polar); climate elements: temperature, precipitation, humidity, wind, pressure.

Climate variability: El Niño/La Niña (ENSO), North Atlantic Oscillation, Milankovitch cycles (eccentricity ~100 ka, obliquity ~41 ka, precession ~23 ka).

Climate records: ice cores (CO₂ and δ¹⁸O), tree rings, corals, sediments, instrumental records since ~1850; feedbacks include albedo, water vapour and permafrost carbon.

Anthropogenic forcing: rising CO₂ from fossil fuels and land-use change; mitigation (renewables, efficiency, carbon sinks) versus adaptation (infrastructure, flood defence, agriculture shifts).

Water cycle fluxes: evaporation, transpiration, condensation, precipitation, runoff, infiltration, percolation, groundwater flow; oceans hold ~97% of water, only ~0.6% is liquid freshwater.

Watershed/catchment: area drained by a river system; divide separates catchments; hydrograph shows discharge response to precipitation (lag time, base flow, peak flow).

Aquifer types: unconfined (water table) and confined (artesian, potentiometric surface); porosity, permeability and transmissivity control storage and flow.

Darcy's law: Q = K·A·(Δh/ΔL), where K is hydraulic conductivity and Δh/ΔL the hydraulic gradient.

Groundwater overexploitation causes water-table decline, land subsidence, saltwater intrusion in coastal aquifers and drying of springs.

Water quality indicators: BOD, COD, dissolved oxygen, nitrates, phosphates, turbidity, pH, conductivity, heavy metals, faecal coliforms.

Eutrophication: nutrient enrichment (N, P) causes algal blooms, oxygen depletion and fish kills; mitigation includes wastewater treatment and buffer strips.

Water management: dams, desalination, reuse, demand management, pricing, river-basin plans; EU Water Framework Directive targets good ecological status.

Ecosystem components: biotope (abiotic) and biocenosis (biotic); trophic levels: producers, consumers, decomposers; food chains and webs; energy flows one way, matter cycles.

Ecological pyramids: numbers, biomass, energy (energy pyramid never inverted); ~10% energy transfer between trophic levels.

Biodiversity levels: genetic, species, ecosystem; hotspots and endemism; threats include habitat loss, invasive species, overexploitation, pollution, climate change (HIPPO).

Population dynamics: exponential growth (r) versus logistic growth (K carrying capacity); limiting factors, density dependence, r- and K-strategists.

Soil profile horizons: O (organic), A (topsoil, humus), B (illuviation), C (weathered parent material), R (bedrock); soil texture triangle (sand, silt, clay).

Soil degradation: erosion, salinisation, compaction, loss of organic matter, contamination; conservation measures include terracing, contour ploughing, crop rotation.

Biogeochemical cycles: carbon (photosynthesis, respiration, combustion, dissolution), nitrogen (fixation, nitrification, denitrification), phosphorus (sedimentary, limiting nutrient), water cycle.

Ecological succession: primary (bare substrate, pioneer species) and secondary (after disturbance); climax community; resilience and stability concepts.

Environmental Impact Assessment (EIA) stages: screening, scoping, baseline study, impact prediction, mitigation, reporting, public consultation, decision and monitoring.

Air pollutants: primary (CO, NOx, SO₂, particulates, hydrocarbons) and secondary (ozone, PAN, sulphuric/nitric acid); photochemical smog and acid rain (pH <5.6).

Air pollution control: cyclones, electrostatic precipitators, bag filters, scrubbers, catalytic converters, low-sulphur fuels, renewable energy substitution.

Water pollution sources: point (industrial discharge, sewage outfalls) versus diffuse (agricultural runoff); treatment stages: primary (physical), secondary (biological), tertiary (nutrient removal).

Soil pollution: heavy metals (Pb, Cd, Hg, Cu), pesticides, hydrocarbons; remediation by excavation, soil washing, phytoremediation, bioremediation, immobilisation.

Waste hierarchy: prevention > reuse > recycling > recovery (energy) > disposal; landfill leachate and biogas management; hazardous waste requires controlled storage.

Noise, light and thermal pollution; radioactive waste classification and storage; marine plastics and microplastics.

Environmental management tools: ISO 14001, EMAS, life-cycle assessment, carbon footprint, environmental taxes, circular economy and the polluter-pays principle.

Topographic maps: scale (1:25,000 means 1 cm = 250 m), contour lines, contour interval, spot heights, slope steepness (closer contours = steeper), gradient = vertical difference / horizontal distance × 100.

Geological map interpretation: strike and dip symbols, cross-sections, apparent versus true dip, fold axes, fault traces, outcrop patterns (V-rules in valleys).

Strike and dip measurement uses a geological compass/clinometer; strike is the compass direction of the horizontal line on a bedding plane, dip is the maximum inclination perpendicular to strike.

Sampling principles: representative, random or systematic grid sampling, composite samples, chain of custody, avoiding contamination; sample size depends on grain size (larger for coarse material).

Laboratory techniques: XRD for mineral identification, XRF for elemental composition, thin-section petrography under polarising microscope, grain-size analysis by sieving and sedimentation.

Water analysis: pH meter, conductivity meter, dissolved oxygen probe, titration for alkalinity/chloride, spectrophotometry for nitrate and phosphate.

Data presentation: tables, graphs, scatter plots, contour maps, histograms, rose diagrams for directional data; statistical measures of mean, median, standard deviation and correlation.

Field safety and ethics: risk assessment, PPE, permissions, minimum disturbance, recording coordinates (GPS) and field notes with sketches and photographs.