Knowledge and understanding Geological techniques and skills Comments d. Silicates are the commonest rock- forming minerals and are built from silicon- oxygen tetrahedral (single, chain, sheet and framework silicates). Simple analysis of silicate mineral structures from models and diagrams. Candidates should know the chemical structure of silicates as it relates to the physical properties of minerals (e.g. crystal shape, hardness and cleavage) rather than details of the chemical variations between minerals. As exemplified by olivine (single tetrahedra), augite/pyroxene (single chain),hornblende/amphibole (double chain), micas (sheet) and quartz/feldspar (framework). e. Minerals are naturally occurring inorganic chemical compounds or elements with compositions that may be expressed as chemical formulae. Minerals have distinct chemical compositions, atomic structures and physical properties by which they may be identified. SP1: Investigation of diagnostic properties of minerals: colour, crystal shape, cleavage, fracture, hardness, relative density, streak, lustre, reaction with cold dilute (0.5 mol dm−3) hydrochloric acid. SP2: Measurement of the density of minerals. Recognition, using appropriate tests, of the following rock- forming minerals (as specified on the mineral data sheet available for use in the examination) from their diagnostic properties: quartz, calcite, feldspars (orthoclase, plagioclase), augite, hornblende, olivine, micas (biotite, muscovite), haematite, galena, pyrite, chalcopyrite, fluorite, barite, halite, gypsum, garnet, chiastolite/andalusite. Candidates should be able to investigate the physical/chemical properties of minerals (including unfamiliar minerals) in the laboratory and field. Candidates should be able to measure the density of minerals using an appropriate technique and evaluate the accuracy of such calculations. Candidates will be required to use a mineral data sheet of diagnostic mineral properties in their identification of the stated minerals.
Knowledge and understanding Geological techniques and skills Comments SP3: Application of classification systems using distinguishing characteristics to identify unknown minerals. Candidates should be able to use flow charts to classify minerals (including unfamiliar minerals) from their observed physical/chemical properties. f. Rocks are composed of aggregates of minerals, pre-existing rocks or fossils. g. Igneous, sedimentary and metamorphic rocks display differences of composition and texture that reflect their mode of origin. Observation and investigation of hand specimens of a variety of rocks (including sampling in the field) in order to: identify and interpret component composition interpret colour and textures (crystalline/clastic; crystal or grain size/shape; sorting; foliation; mineral alignment/bedding/cryst- alline banding) and hence deduce the mode of origin of the rock as igneous, metamorphic or sedimentary. SP4: Production of scaled annotated scientific drawings of rock samples from hand samples using a light microscope, or hand lens observation. Use and manipulation of the magnification formula magnification = size of image size of real object Candidates should be able to determine the origin of igneous, sedimentary and metamorphic rocks from their differing textures and mineralogies (including unfamiliar rocks) in the laboratory and field. Scientific drawings to include samples in the laboratory and the field using appropriate scales.
Knowledge and understanding Geological techniques and skills Comments e. A study of fluvial, marine, and aeolian sediments demonstrates these differences. Investigation of textures of sediments from different depositional environments. SP5: Production of full rock description of macro and micro features from hand specimens and unfamiliar field exposures of sedimentary rocks in order to interpret component composition, colour and textures, to identify rock types and to deduce their environment of deposition. SP6: Construction of graphic logs using appropriate scale and symbol sets for unfamiliar geological sequences and exposures to record data relevant to an investigation. SP7: Use of photomicrographs to identify minerals and rock textures of sedimentary rocks in order to identify rock types and to deduce their environment of deposition. Interpretation of maps, photographs and graphic logs showing the following sedimentary features: bedding, cross-bedding, graded bedding, laminations, desiccation features, ripple marks (symmetrical and asymmetrical), sole structures (load/flame, flute cast). Candidates should be aware of the link between process and product in their studies of the stated sedimentary environments: fluvial (rivers, deltas alluvial fans and playa lakes) aeolian (wind dominated e.g. desert dunes) marine (shallow water – lagoon/reef/beach systems) marine (deep water – submarine fan turbidites) Candidates should be able to explain the formation of the stated sedimentary structures.
Knowledge and understanding Geological techniques and skills Comments Identification in hand specimen of the following sedimentary rocks from their composition, texture and other diagnostic features: sandstones (orthoquartzite, arkose, greywacke), shale/mudstone, limestones (shelly, oolitic, chalk), conglomerate, breccia. Investigation of contrasts between fluvial, marine and aeolian sediments. Use of logarithms in relation to quantities that range over several orders of magnitude. Construction and interpretation of frequency tables and diagrams, bar charts and histograms. Knowledge of the characteristics of normal and skewed distribution. Plotting of variables from experimental or other circular data. Understanding of the terms mean, median and mode. Selection and use of a statistical test. Plotting of two variables from experimental or other linear data. Candidates need only have knowledge of the sedimentary rocks indicated. Candidates should be able to identify the stated sedimentary rocks in hand specimen and the field. It is understood that it might not be possible to investigate the full range of rocks in the field or that this list is exclusive. For exemplification of mathematical skills see Mathematical Guidance for A level Geology. The mathematical skills identified are not exclusive to this section of the specification. f. Sedimentary rocks may result from the accumulation of organic material (limestone, coal) or by precipitation of solid material from solution (evaporites). Analysis of biogenic components in sedimentary rocks. Candidates should be able to describe the order of precipitation of evaporate minerals from seawater in terms of their relative solubilities – low (calcite/dolomite gypsum/anhydrite potassium/magnesium salts).
Knowledge and understanding Geological techniques and skills Comments Sedimentary rocks exhibit differences in texture which influences porosity and permeability: grain angularity, sphericity, size, sorting, which reflects: the nature of rocks from which they were derived conditions of climate, weathering, erosion and deposition operating during their formation post-depositional factors as sediments are formed into sedimentary rocks: diagenesis and lithification (compaction, recrystallisation, cementation, pressure solution). Investigation of the concept of ‘sediment maturity’. Immature sedimentary rocks characterised by a wide range of mineral compositions and/or lithic clasts; mature sedimentary rocks with restricted mineralogies dominated by mineral species resistant to weathering and erosional processes. Understanding that y = mx + c represents a linear relationship. Candidates should be aware of the range of texture in descriptive terms (as used on a grain size comparator): angularity – very angular to well rounded sphericity – high to low sphericity size – reference to the Wentworth scale sorting – very well to poorly sorted For exemplification of mathematical skills see Mathematical Guidance for A level Geology. The mathematical skills identified are not exclusive to this section of the specification.
Knowledge and understanding Geological techniques and skills Comments SP8: Production of full rock description of macro and micro features from hand specimens and/or unfamiliar field exposures of igneous rocks in order to interpret component composition, colour and textures, to identify rock type and to deduce their cooling history. Identification in hand specimen of the following igneous rocks from their composition, texture and other diagnostic features: Silicic: granite Mafic: gabbro, dolerite, basalt Ultramafic: peridotite. SP9: Use of photomicrographs to identify minerals and rock textures of igneous rocks to identify rock type and to deduce their cooling history. Use of ratios, fractions and percentages. Calculation of the circumferences, surface areas and volumes of regular shapes. Construction and interpretation of frequency tables and diagrams, bar charts and histograms. Knowledge of the characteristics of normal and skewed distributions. Candidates need only have knowledge of the igneous rocks indicated. Candidates should be able to identify the stated igneous rocks in hand specimen and the field. It is understood that it might not be possible to investigate the full range of rocks in the field or that this list is exclusive. For exemplification of mathematical skills see Mathematical Guidance for A level Geology. The mathematical skills identified are not exclusive to this section of the specification.
Knowledge and understanding Geological techniques and skills Comments Partial melting of rock at depth to form magma occurs in a number of different interplate and intraplate tectonic settings: beneath divergent plate margins – partial melting of mantle rocks generates basaltic magma near to convergent plate margins – partial melting of subducted oceanic lithosphere and overlying lithospheric wedge generates andesitic magma in mantle plumes (hotspots) – partial melting of mantle rocks generates basaltic magma in deeply buried lower continental crust during orogeny – melting and assimilation of crustal material generates granitic magma. Investigation of the role of rising convection cells in decompression melting. Investigation of global distribution of mantle plumes from maps. Volcanic hazards result from: blast/explosion ash fall, pyroclastic flows (nuées ardentes) and gases lava flows debris flows and mudflows (lahars). Investigation, using geological data from a wide variety of volcanic monitoring techniques (including ground deformation, gravity and thermal anomalies, gas emissions and seismic activity), of the risk of volcanic hazards and the extent to which they can be managed and controlled in order to reduce risk. Candidates are expected to have studied specific examples of the stated hazards and monitoring techniques but will not be required to recall details of these examples in an assessment.
Knowledge and understanding Geological techniques and skills Comments f. Preservation can give rise to a wide range of fossil materials: actual remains, hard parts, petrification by mineral replacement (calcification, silicification, pyritisation), carbonisation, moulds/casts. g. Fossil accumulations may be preserved without appreciable transportation (life assemblages) or preserved after transportation (death assemblages), or as derived fossils re- deposited in later sediment. Analysis of modern and fossil assemblages to interpret the degree of transportation prior to burial. Candidates should be able to determine transport history based on the degree of fragmentation, sorting or alignment of specimens within a fossil assemblage. The fossil record is: biased, in favour of marine organisms, with body parts resistant to decay, that lived in low energy environments, and suffered rapid burial incomplete, as natural processes can distort or destroy fossil evidence (predation, scavenging, diagenesis, bacterial decay, weathering, erosion, metamorphism) Candidates should be aware of the importance and limitations of a Lagerstätte in providing exceptional preservation e.g. Ediacaran (Precambrian), Burgess Shale (Cambrian), Wenlock Series (Silurian), Solnhofen (Jurassic).
Topic F3: TIME AND CHANGE Key Idea 2:Geological events can be placed in relative and absolute time scales Knowledge and understanding Geological techniques and skills Comments a. Geological events can be placed in relative time scales using criteria of relative age: evolutionary change in fossils, superposition of strata, unconformities, cross- cutting relationships, included fragments,‘way- up’ criteria. Interpretation of age relations of rocks and rock sequences using maps, cross-sections and in the field. b. Some rocks and minerals can be dated radiometrically to give an absolute age. This involves radioactive decay and the principles of radiometric dating; radioactive series and radioactive half-life; radiometric dating as exemplified by Potassium – Argon (40K– 40Ar), Samarium – Neodymium (147Sm –143Nd). Simple use of the principles of radiometric dating (decay rates and the half-life concept) to calculate the absolute age of a sample. Evaluation of the assumptions, accuracy and limitations inherent in the radiometric dating method. Candidates will need to know that differences between the K – Ar and Sm – Nd methods and understand the principle of using the gradient of an isochron to establish relative age in the latter. Candidates will not be expected to plot isochrons or calculate age from isochrons but simply interpret relative age. c. Fossils are used in relative dating. Observation and identification of appropriate morphological features and their changes through time: graptolites – number and position of stipes, thecal shape in the Early Palaeozoic. cephalopods – suture lines in the Late Palaeozoic and Mesozoic (goniatite, ceratite and ammonite). Candidates are expected to be able to provide a relative date to a formation based on graptolite or cephalopod assemblages within the appropriate time frame (Early Palaeozoic and Mesozoic).
Topic F4: EARTH STRUCTURE AND GLOBAL TECTONICS Key Idea 1: The Earth has a concentrically zoned structure and composition Knowledge and understanding Geological techniques and skills Comments a. The Earth has a layered structure: crust, mantle, outer and inner core. Each layer has a distinctive composition and/or rheological properties. Direct and indirect evidence is derived from meteorite (stony, iron) compositions, mantle xenoliths, mean density calculations and geophysical measurements (seismology, geomagnetism, gravity, conductivity). Analysis of seismological evidence for the internal structure of Earth: P and S body waves, surface waves, time-distance curves, shadow zones, velocity-depth models of Earth structure, density distribution with depth. Translation of information between graphical, numerical and algebraic forms. SP18: Measurement of the densities of representative samples of Earth layers (e.g. granite, basalt). Simple analysis of geomagnetic evidence for core composition and processes. Candidates should be able to use evidence to interpret the state, depth and probable composition of the Earth’s layers. For exemplification of mathematical skills see Mathematical Guidance for A level Geology. The mathematical skills identified are not exclusive to this section of the specification. b. The crust is a thin layer of distinctive composition overlying the mantle; continental and oceanic crust can be recognised and distinguished by their differing thicknesses, composition and structure. Interpretation of geophysical data on crustal structure (seismic, gravity, magnetic) from continental and oceanic areas. Analysis of ocean drilling data to re-interpret the Mohorovičić discontinuity (Moho) at the base of the crust (e.g. Joides Resolution 360). Candidates should be given the opportunity to evaluate and validate the new knowledge obtained from current ongoing scientific research. the significance of serpentinite at the Moho discontinuity
Topic F4: EARTH STRUCTURE AND GLOBAL TECTONICS Key Idea 2:The Earth’s internal heat is the underlying cause of lithospheric plate motions that control global geological processes Knowledge and understanding Geological techniques and skills Comments a. The uppermost part of the mantle and the overlying crust form a rigid outer shell of the Earth known as the lithosphere, forming tectonic plates, underlain by a weaker upper mantle zone known as the asthenosphere. The asthenosphere is evidenced by the seismological low velocity zone (LVZ). Investigation of how the plate tectonics paradigm developed over time, from continental drift, through active mantle convection carrying passive tectonic plates, to modern theories of the causes of plate movement (slab pull and ridge push). Candidates should be aware of the importance of the plate tectonic model in providing an underlying framework to understand how the Earth works. b. The lithosphere consists of several plates in relative motion. Three types of plate boundary are recognised; divergent, convergent (involving subduction) and conservative. There is a relationship between seismicity, volcanicity and plate boundaries. Interpretation of the evidence for plate tectonic theory from: direct measurement – ocean floor drilling, relative movement using GPS global maps of the distribution of continents, volcanoes, earthquake epicentres/foci, ocean trenches and ridges, orogenic belts and palaeoecological /palaeoenvironmental zones seismic tomography an investigation of the geomagnetic/geoelectrial properties of rocks and minerals geothermal data (hot spots, heat flow). SP19: Investigation of the relationships between earthquake data (focal depth, magnitude and distance from plate boundaries) using data on Google EarthTM. Teachers may find the following resource useful in the delivery of F4:
Knowledge and understanding Geological techniques and skills Comments Use of a scatter diagram to identify a correlation between two variables. c. Forces driving plates are a matter of current debate involving thermal convection of the mantle together with gravitational forces and ocean lithosphere density differences at subduction zones. Evaluation of the possible mechanisms for plate movement (role of mantle convection, slab pull, ridge push). Candidates should be aware that currently the possible mechanisms for plate movement are much disputed. d. Some rocks contain a record of the direction of the Earth’s magnetic field at the time of their formation, known as remanent magnetism. This is linked to ferromagnetism in some iron minerals and their Curie temperatures. e. Palaeomagnetism can be used to determine changes of latitude as different continents moved through geological time, indicating continental drift. Ocean floor magnetic anomalies indicate sea floor spreading. Candidates should be aware of remanent magnetic inclination in determining changes in continental latitude through geological time. Knowledge of Polar Wandering Curves is not required.
Knowledge and understanding Geological techniques and skills Comments b. The substitution of one element for another in the crystal structure of a mineral depends upon atomic radius and valency; solid solution as exemplified by olivine and plagioclase feldspar. Investigation of magma crystallisation and differentiation processes using phase diagrams (plagioclase feldspar, olivine). Candidates should be able to interpret phase diagrams between solid solution end members from: Ca-rich plagioclase (Albite) to Na rich (Anorthite) Mg-rich olivine (Fosterite) to Fe-rich (Fayalite). c. The formation of magma chambers under ocean ridges and rises can be interpreted from models. Analysis of ocean survey data to investigate current models of how oceanic ridges (particularly mid ocean ridges-MORs) are formed (e.g. RRS James Cook – 2016). Candidates should be familiar with new models of ocean ridge formation (using data from seismic tomography and de e p ocean drilling) involving symmetrical and asymmetrical spreading ocean core complexes (OCC) the significance of serpentinite. https://teacheratseablog. wordpress.com/tag/science/
Topic G1 : ROCK FORMING PROCESSES Key Idea 2:The mineralogy and texture of metamorphic rocks are determined by the composition of the parent rock and the conditions of metamorphism Knowledge and understanding Geological techniques and skills Comments a. Igneous and sedimentary rocks contain minerals that are stable or metastable at the temperature and pressure of their formation. Changes in temperature and/or directed stress over time lead to the growth of new minerals with different stability fields. Analysis of simple pressure- temperature-time paths involved in contact and regional metamorphism. Simple analysis of phase diagrams showing stability fields of selected metamorphic minerals: kyanite/sillimanite/ andalusite. Candidates should appreciate that prograde metamorphic effects result from increases in temperature and (usually) pressure. Retrograde metamorphism (though uncommon) allows prograde mineral assemblages to revert to those more stable at less extreme temperature and pressure. Detailed knowledge of metamorphic facies is not required. b. Mineralogical changes during metamorphism depend on the composition of the parent rock and the temperature/pressure field. SP20: Investigation of contact metamorphism using the ‘Metamorphic Aureole’ simulation experiment. c. Contact and regional metamorphism of mudstone/shale lead to the growth of new minerals indicative of the type and grade of metamorphism: low to high grade metamorphism. Candidates are expected to use evidence from index minerals to arrange clay- rich rocks in order of their increasing grade. d. Contact, regional and dynamic metamorphism result from different pressure/temperature conditions and produce characteristic textural changes associated with recrystallization, ductile flow and shear deformation. Study of diagrams/photomicrographs to identify and analyse the following metamorphic textures: granoblastic; porphyroblastic; mylonitic.
Topic G1: ROCK FORMING PROCESSES Key Idea 3: Sedimentary processes can be understood using scientific modelling Knowledge and understanding Geological techniques and skills Comments a. Sedimentary processes which are infrequent and/or difficult to observe (e.g. turbidity currents) can be understood and explained using scientific models. Application of the Hjulstrom graph. Determination of the slope and intercept of a linear graph. b. The distribution of environments represented by rocks in a vertical stratigraphic column is related to the distribution of those environments laterally (Walther's Law); marine transgressions and regressions, diachronous stratigraphic boundaries. Application of Walther’s Law to extend interpretation from two- dimensional data (borehole logs, cliff sections, graphic logs) to three-dimensions. Candidates are expected to relate vertical sequences (e.g. outcrop of borehole) with the lateral changes in facies identified in modern sedimentary environments (e.g. a delta) and understand that lithofacies are not necessarily time- dependent.
Topic G2: ROCK DEFORMATION Key Idea 1: Geological structures are formed when rock material undergoes deformation Knowledge and understanding Geological techniques and skills Comments a. The nature of rock deformation is determined by the competence of the parent rock and conditions during deformation (temperature, confining pressure, strain rate). Recognition of the differences in deformation of competent and incompetent rocks. Candidates are expected to predict the effects of deformation (brittle fracture and ductile flow) on rocks of different competences. b. Fold characteristics; amplitude, wavelength, interlimb angle (open, tight, isoclinal), axial plane attitude (upright, inclined, overturned, recumbent), plunging folds. Identification of plunge direction (of axis) and axial planar cleavage. Represent limb dip and strike data on a polar equal area stereonet (polar plots only not projections or great circles). Plotting of variables from experimental or other circular data. For exemplification of mathematical skills see Mathematical Guidance for A level Geology. The mathematical skills identified are not exclusive to this section of the specification. c. Fault type is determined by the orientation of the principal stresses. Technical terms to describe fault elements: slickensides, fault gouge, fault breccia. Analysis of the relationship between fault type (normal, reverse/thrust, strike-slip) and the orientation of the principal stress components  int, Candidates will be expected to interpret the effect of dip-slip or strike- slip relative movement, but not oblique fault movement. d. Structural reactivation: earlier-formed faults can be reactivated during later tectonism; folds may be refolded. Structural inversion: reactivation of normal faults in compression or reverse faults/thrusts in extension. Recognition of evidence for fault reactivation on geological maps, cross- sections, diagrams and photographs. e. The nature of outcrop patterns formed by the intersection of geological structures with a topographic surface are displayed on geological maps. Calculations involving measurements of: true bed thickness vertical bed thickness width of outcrop angle of dip. Use of sin, cos and tan in physical problems. For exemplification of mathematical skills see Mathematical Guidance for A level Geology. The mathematical skills identified are not exclusive to this section of the specification.
Topic G3: PAST LIFE AND PAST CLIMATES Key Idea 1: Fossils provide evidence for the increasing diversity of life through geological time Knowledge and understanding Geological techniques and skills Comments The fossil record provides evidence of changes in floras and faunas through geological time and the development of higher life forms: Precambrian life: life possibly evolved early in Earth history (3.8 billion years ago). The Ediacaran fauna represents the oldest diverse set of multicellular, soft bodied organisms (565 Ma) The Cambrian Explosion: the development of mineralised skeletons led to a wide variety of advanced marine invertebrates by the early Cambrian Life in the ocean diversified in stages identified by separate fauna: a basic understanding of the difference between Cambrian, Palaeozoic and modern faunas Interpretation of evolutionary diagrams. Analysis of the possible causes of faunal diversification at the Precambrian-Cambrian boundary. Interpretation of simple diversity curves (Sepkoski’s curves). Candidates should be familiar with the use of cladograms in showing the relationships amongst organisms and in the development of evolutionary trees. Candidates should be able to evaluate a range of hypotheses (environmental, developmental and ecological) that have been proposed for the sudden faunal diversification at the Precambrian-Cambrian boundary. Candidates will be expected to interpret modes of life from an analysis of vertebrate morphologies including: size, shape, dentition (carnivore v herbivore), pelvis, vertebrae, limbs, ornamentation (horns, plates, feathers).
Knowledge and understanding Geological techniques and skills Comments The Phanerozoic was marked by the migration of organisms onto the land during the Palaeozoic. Vertebrate development of amphibians from fish, reptiles from amphibians and mammals and birds from reptiles. Colonisation of the land by plants. Analysis of the morphology of fossil vertebrates (including dinosaurs) to interpret function/mode of life. Candidates should be aware of fossil evidence in vertebrate development (as exemplified by Ichthyostega, Archaeopteryx). Diversity increased through the Phanerozoic punctuated by many declines caused by mass extinction events. Mass extinctions may result from a variety of causes including: asteroid impact (Alvarez) large scale volcanicity (flood basalts) changes in land/sea levels rapid climate change. Evaluation of contrasting hypotheses regarding mass extinctions. Candidates should be aware of the evidence for the various theories including: Asteroid impact – shocked quartz, spherules, iridium, tsunamis deposits, Chixulub crater Volcanicity – flood basalt (Deccan Plateau), palaeomagnetic evidence of timing. c. Mass extinctions are exemplified by the end- Permian (P-T) and Cretaceous-Paleogene (K-Pg) boundary events. d. There are alternative interpretations of evolutionary patterns based on the fossil record. Gradual change (gradualism) vs stability interrupted by sudden change (punctuated equilibrium). Evaluation of alternative interpretations of evolutionary patterns.
Topic G4 : EARTH MATERIALS AND NATURAL RESOURCES Key Idea1: Geological processes lead to the concentration and accumulation of natural resources in deposits that can be exploited; economic deposits can be concentrated by igneous and sedimentary processes Knowledge and understanding Geological techniques and skills Comments Processes of formation of metalliferous ores. Igneous associations of ores – magmatic segregation, hydrothermal activity. Sedimentary associations of ores – placer deposits; residual deposits; precipitated deposits. Geological map interpretation (ore body geometry, field relations); section-drawing through ore bodies. Calculation of the circumferences, surface areas and volumes of regular shapes. Recognition and making use of appropriate units in calculations. Use of ratios, fractions and percentages. Geological map interpretation; section drawing through industrial mineral deposits. Candidates are expected to have studied the formation of cumulate deposits (e.g. iron chromite ores), massive sulphide ores (black smokers), hydrothermal ores associated with igneous intrusions (hydrothermal mineral veins, pegmatite deposits). Candidates are expected to have studied the formation of placer deposits, residual deposits (bauxite) and precipitated deposits (BIFs and evaporates). b. Processes of formation of non-metallic minerals of economic importance: china clay. Candidates are expected to have studied the formation of china clay only. c. Formation of sedimentary deposits of economic importance as “bulk minerals” for aggregate: sand and gravel. Candidates are expected to be aware of the accumulation of sand and gravel deposits in a range of environments: river, river terrace, glacial/fluvioglacial, beach.
Topic G4 : EARTH MATERIALS AND NATURAL RESOURCES Key Idea 2:Permeable rocks offer pathways for oil and gas migration; highly porous rocks can act as natural reservoirs for underground supplies of oil and gas Knowledge and understanding Geological techniques and skills Comments a. Porosity and permeability of rock and sediments affects the presence, distribution and migration of fluids (water, oil and natural gas): primary/secondary porosity in rock; factors that affect porosity and permeability. Analysis of rock textures in terms of porosity and permeability (grain size, shape, packing, sorting; cementation); primary and secondary porosity. b. Fluid flows in rocks and sediment can be modelled using Darcy’s Law. Application of Darcy’s Law to model fluid flow: Q =  kA   L  Candidates will be required to apply, but not recall, Darcy’s Law to measure fluid flow in rocks. For exemplification of Darcy’s Law see Mathematical Guidance for A level Geology. c. Oil and gas migration are controlled by geological factors: migration paths – relative buoyancy of oil and natural gas; structural and stratigraphic traps for hydrocarbons; reservoir rocks and cap rocks. Analysis of geological cross- sections through oil and natural gas bearing structures. d. The characteristics of Analysis of the controls on Candidates are expected to subsurface geology groundwater quality which have studied the differing which control the flow of result from geochemistry geologies associated with groundwater (carbonates and sulfates), the formation of springs. (hydrogeology) include aquifer filtration, residence confined and unconfined time and sources of pollution. aquifers, aquicludes, aquitards, the water table, piezometric surfaces, cones of depression and recharge zones. −
Topic G4 : EARTH MATERIALS AND NATURAL RESOURCES Key Idea 3: A wide range of prospecting techniques can be employed to explore for mineral resources Knowledge and understanding Geological techniques and skills Comments Techniques used to prospect for mineral resources. geophysical surveying – gravity (Bouguer), seismic, magnetic, electrical. geochemical prospecting – river water, river sediment and soil sampling. Each method has particular applications and limitations. Geological map interpretation; simple analysis of geophysical and geochemical data related to mineral exploration. Selection of appropriate geophysical methods for different mineral searches, depending upon the geometry and physical properties of the target body. Interpretation of seismic reflection sections to identify potential oil and natural gas-bearing structures. Candidates are expected to have studied the following geophysical prospecting techniques: gravity (Bouguer) seismic (reflection only – 2 way time) magnetic (including aeromagnetic) electrical (resistivity only) electromagnetic (EM survey) Teachers may find the following resource useful in delivering part of this section: b. Microfossils are used for correlation in prospecting for oil and natural gas. Construction of geological cross- sections from borehole data, including dating and correlation using microfossils. Candidates should be aware of the use of the following: foraminifera, calcareous nannofossils and palynomorphs (pollen, spores and dinoflagellates)
Topic T1 : GEOHAZARDS Key Idea 1: Natural geohazards have a worldwide impact on human populations including in the British Isles Knowledge and understanding Geological techniques and skills Comments Seismic hazards. There is a relationship between earthquakes and active fault zones. The magnitude of an earthquake event is measured on the Moment Magnitude scale (MW ). The intensity of earthquake damage around an event is measured on the modified Mercalli scale and is related to earthquake size, depth, distance, local ground conditions and building standards. Seismic hazards include ground shaking, liquefaction. Tsunamis can cause devastation in coastal areas following an undersea earthquake (landslide or volcanic eruption). Analysis of geological data from appropriate case studies of each the following: a major earthquake a mass movement event to compare and contrast the nature of the geological hazards. Investigation of the factors that affect the impact of earthquakes and mass movements. Though candidates are expected to be familiar with appropriate case studies they will not be required to recall specific case study detail in assessments. Teachers should be aware of the link with volcanic hazards outlined in F2. Candidates should be aware that shaking is linked to the natural frequency of vibration of a building (resonance) and depends upon the earthquake frequency (Hz) and the height/shape of the building. Candidates should be aware of the physical, social and economic factors that affect the impact of geohazards (including population density, building type and density, hazard awareness/preparation and level of economic development).
Knowledge and understanding Geological techniques and skills Comments Mass movement hazards. The mechanism and triggering of rock avalanches, landslides and debris flows are linked to angle of slope, lithology, weathering, load, groundwater regime, rainfall, ground vibration, vegetation cover. c. The British Isles is prone to local natural geohazards at different scales associated with: earthquakes, landslides, shrinking and swelling clays and subsidence (including sink holes). Analysis of the causes and effects of geohazards in the British Isles from appropriate data sets. Teachers may find the following resources useful in the delivery of T1: d. There is evidence that significant tsunamis have affected the British coast in the recent geological past. Candidates are expected to be aware of the Storegga slide.
Topic T1 : GEOHAZARDS Key Idea 3:Engineering activities can have a major impact on the natural environment Knowledge and understanding Geological techniques and skills Comments Extraction of geological raw materials and economic storage of waste products involves interference with the surface and/or subsurface environment. Quarrying and mining. Problems associated with the extraction of rock and minerals – stability of working faces, rock falls, ground subsidence, flooding, surface/groundwater pollution and waste tipping. Waste disposal. Problems of ground contamination, including groundwater pollution and methane gas production, can be ameliorated by good geological site selection and engineering practice. There are special problems with the disposal of highly toxic chemical and radioactive waste. Analysis of the methods of extraction of geological raw materials to identify potential environmental problems and the ways by which these may be minimised. Analysis of landfill engineering data for the disposal of domestic waste or underground sites for the disposal of highly toxic chemical and radioactive waste. Candidates will be expected to have studied extraction from open cast pits and underground mines.
Knowledge and understanding Geological techniques and skills Comments Contaminated land. Problems with the management and remediation of industrial brownfield sites associated with toxic chemical materials, ground instability, subsidence and groundwater pollution. Analysis of the issues associated with the remediation of one industrial brownfield site. Candidates will be expected to have studied: toxic heavy metal contamination (e.g. cadmium, mercury , lead and arsenic) of soil and groundwater problems of ground pollution and instability of former landfill sites remediation solutions (e.g. phytoremediation, solidification and stabilisation methods) Teachers may find the following resources helpful: Civil engineering work should take account of geological factors to avoid: problems of ground instability associated with weathering, dip of strata, folding, faulting, rock cleavage, joint patterns and fracture density interference with the hydrological system: pore water pressure, surface and underground drainage (porosity, permeability, water table, aquifers) Simple analysis of rock slope stability involving friction angle and orientation of rock discontinuities. Analysis of the suitability of sites using a variety of geological and geotechnical data.
Knowledge and understanding Geological techniques and skills Comments radon gas – sources and pathways to surface, surface geology of high-risk areas. c. In building major structures geological factors and geological rock properties must be taken into account (e.g. dams and reservoirs, cuttings and tunnels, buildings). Candidates should be aware of the impact of valley shape, rock structure (bedding, jointing, faulting, cleavage), rock strength (unconfined compressive strength – UCS), porosity and permeability in major engineering projects.
Topic T2 : GEOLOGICAL MAP APPLICATIONS Key Idea 2: Geological maps contain information relevant to a wide range of geological applications Knowledge and understanding Geological techniques and skills Comments a. Geological maps provide an essential database of detailed information about the distribution of rocks at the surface that can be used to interpret or predict subsurface geological conditions. Use of geological maps at various scales to identify from outcrop patterns and other data on geological maps: conformable and unconformable sedimentary formations metamorphic sequences and igneous bodies (and any associated metamorphic effects) structural features. Additional map resources (for free online viewing of all BGS maps) Copies of past WJEC Geology A level question papers (GL4) featuring colour BGS maps can be accessed using the “GL4 BGS colour maps and past questions” resource in the Resources for Teachers section of the Eduqas A level Geology webpage. This resource, with additional mark schemes is repeated on the secure website. Geological maps provide an essential database for geological applications: design of construction projects identification of geological hazards location of resources – groundwater, fossil fuels; alternative energy sources identification of environmental issues Use of geological maps at various scales to: assess the potential of surface sites for a range of engineering projects on the basis of the prevailing geology identify geological hazards (landslides, subsidence) at defined surface sites on the basis of the prevailing geology interpret subsurface geology in connection with groundwater (water table, springs, aquifers, artesian wells), coal, oil, natural gas and geothermal energy identify the environmental issues specific to
Knowledge and understanding Geological techniques and skills Comments d. The fragmentary terrestrial record of climate change contrasts with a near complete oceanic record: oxygen isotope evidence (18O/16O) from ocean sediments provides evidence of climate fluctuations through the Quaternary. Candidates should understand the principles behind the oxygen isotope evidence for climate change and be able to analyse simple oxygen isotope curves, linking them to radiocarbon dates. e. Ice core evidence for atmospheric change. Candidates should know how measurement of past concentrations of gases (including carbon dioxide and methane) in the atmosphere can be obtained directly from ice core data (Antarctica and Greenland) and how ice cores are dated to give a record of climatic climate.
Option T4: GEOLOGICAL EVOLUTION OF BRITAIN Key Idea 1:The Neoproterozoic and Phanerozoic stratigraphy of the British area has been determined largely by the assembly of lithotectonic terranes during three orogenic events Knowledge and understanding Geological techniques and skills Comments a. Rocks from all the major subdivisions of geological time occur in Britain and surrounding shelf areas: Precambrian, Early and Late Palaeozoic, Mesozoic, Cenozoic. Study of geological maps at various scales including maps linking onshore and offshore areas. Use of maps and related data to investigate major geological processes operating in different parts of the British area from the Precambrian to the Quaternary. Candidates are expected to use their fieldwork to collect and analyse data of a selected area(s) to interpret the local stratigraphy and place into a wider context. Information used to investigate the geological history of the British Isles also includes remote sensing techniques that provide an indirect way to investigate the subsurface geology. The principles associated with: potential field measurements gravity (Bouguer anomaly) and magnetic surveys borehole analysis; as exemplified by the Mochras Borehole. seismic reflection surveys; onshore and offshore. Application of remote sensing and subsurface data collection to help interpret the Palaeozoic and Neoproterozoic geology of the British area. Teachers may find the following resource useful in delivering part of this section: c. A number of orogenic events have affected the British area: location and large-scale geology. Ages, main structures and dominant trends of the Caledonian and Variscan orogenic belts; Alpine orogenic influences in Britain. Interpretation of geological maps to identify outcrop patterns associated with large- scale geological features of orogenic belts; fold shapes and descriptors, plunging folds; fault descriptors; regional structural trends as displayed by major folds and faults.
Knowledge and understanding Geological techniques and skills Comments d. Study of the geology (plutonic/volcanic and metamorphic rocks) of these orogenic belts aids the reconstruction of the plate tectonic regimes in which they developed. Collation and evaluation of geological evidence to interpret the Caledonian and Variscan orogenic belts and Palaeogene Igneous Province in plate tectonic terms. e. The Palaeogene Igneous Province of NW Britain provides evidence of the early history of the opening of the North Atlantic Ocean, with associated basaltic volcanicity. Interpretation of the geological characteristics of the Palaeogene Igneous Province in plate tectonic terms. Candidates should be aware of the tectonic link between the opening of the North Atlantic ocean and the rifting of the North Sea.
Option T4: GEOLOGICAL EVOLUTION OF BRITAIN Key Idea 2:The evidence for the northward drift of the British area through the Neoproterozoic and Phanerozoic Knowledge and understanding Geological techniques and skills Comments a. The palaeomagnetic field direction in some British rocks provides evidence of latitude at the time of magnetisation. The use of palaeomagnetic data to calculate palaeolatitudes for the British area, and interpretation of apparent polar wandering curves to determine palaeolatitude changes through time. Candidates should be aware of the role of magnetic inclination, declination and polar wandering curves in determining palaeolatitude. Rocks in Britain show evidence of major climatic change through Phanerozoic time as a result of the northward drift of the British area, exemplified by: Devonian and Permo- Triassic – semi-arid and desert terrestrial and hypersaline marine deposits. Carboniferous, Jurassic and Cretaceous – tropical, shallow marine and terrestrial (coal) deposits. Candidates should be able to understand the significance of changes in rock type (to include limestone, sandstone and coal) and fossils (to include corals, plants and microfossils) in determining climate change through the Palaeozoic.
Knowledge and understanding Geological techniques and skills Comments Early Mesozoic. Separation of Laurasia and Gondwana by the Tethys ocean in southern Europe. Rifting and subsidence in the North Sea area related to the opening of the Atlantic Ocean. Late Mesozoic. During the Cretaceous, continued opening of the Atlantic and continued subsidence of the North Sea area. Cenozoic. Formation of the Alps with related tectonic uplift in the British area. Ongoing subsidence in North Sea area. and plant remains. Coal seams and seat-earths with rootlets. continental red beds and evaporites. Permo- Triassic – semi-arid and desert terrestrial; hypersaline marine deposits; Jurassic shallow marine shelf deposits. open marine Cretaceous chalk deposits recording a period of high global temperatures and sea levels. shallow and non-marine Paleogene deposits recording transgressive- regressive cycles.
Option T5: GEOLOGY OF THE LITHOSPHERE Key Idea 1: The Earth’s heat loss leads to cooling and the development of a strong outer shell (lithosphere) underlain by a layer of lower strength (asthenosphere) Knowledge and understanding Geological techniques and skills Comments a. The Earth loses heat through its surface, leading to the formation of a cold, rigid outer layer known as the lithosphere: surface heat flow and temperature variation with depth, rock strength related to temperature. Graphical comparison of continental and oceanic geotherms with the mantle solidus curve to explain lithosphere/asthenosphere distinction. Candidates should be aware that the strength of materials depends upon temperature which changes with depth (pressure). Approximately 99% of Earth’s internal heat loss at the surface is by conduction through the crust, with mantle convection the dominant method of heat transport from deep within the Earth. b. The base of the lithosphere is defined as the 1300 oC isotherm; lithospheric thickness differs between continents and oceans. Candidates will be expected to analyse data in a variety of forms to demonstrate that the oceanic lithosphere is typically between 50-140 km thick (but beneath the mid-ocean ridges can be only 1- 2km), while continental lithosphere ranges in thickness from 40 km to about 150 km, though even deeper under cratons. c. Global seismology provides evidence for the distinction between lithosphere and asthenosphere: seismic low velocity zone in upper mantle. Ray path modelling to show refraction of earthquake body waves through low velocity zone. Interpretation of P- and S- wave velocity-depth curves and identification of low velocity zone.
Knowledge and understanding Geological techniques and skills Comments d. The crust is a surface layer of distinctive composition at the top of the lithosphere: seismological estimates of crustal thickness; Mohorovičić discontinuity (Moho). Simple interpretation of seismic refraction data to define crustal layering and reflection data to investigate the internal structure of the crust. Candidates should know that the ocean crust is between 5-10 km thick in contrast to the continental crust which ranges between 30-50km. Continental crust in excess of 50 km is exceedingly rare and accounts for less than 10% of the continental crust. e. The generation of magma in different geological settings results in a range of igneous bodies and products: oceanic ridge systems (including mid- ocean ridge basalts (MORBs)), large igneous provinces (LIPs), island arcs and cordilleran mountain belts. Interpretation of heat flow variation across an ocean basin. Evaluation of the evidence for the existence of mantle plumes. Candidates should be aware of the ongoing mantle plume debate amongst scientists and that alternative hypotheses for the observed evidence attributed to the plume model have been proposed. https:// plumesdebate
Knowledge and understanding Geological techniques and skills Comments b. Being of relatively low density, continental lithosphere resists subduction and tends to avoid destruction during plate tectonic cycles, hence the Earth’s oldest crustal rocks are found in continental areas. Investigation of the age distribution of rocks in continental areas using geological maps. Candidates are expected to have investigated geochronological map data for a continental area e.g. North America and be able to relate this to the evolution of the continent. Orogenic belts are sites of major lithospheric thickening. continent-continent collision. continent-island arc collision. cordilleran mountain belts. incorporation of oceanic lithosphere into orogenic belts; ophiolites and accretionary prisms. partial melting and granite. magmatism; delamination. isostatic uplift and gravitational collapse. Identification of large scale features of continental geology and interpretation of their origin and tectonic setting. Investigation of isostasy in continental and oceanic lithosphere. d. Forces acting on the continental crust (plate boundary forces and gravitational spreading) give rise to tectonic stresses that cause brittle and ductile deformation on all scales in crustal rocks. Field interpretation of folds and faults in terms of applied stresses, and their relationship to the regional structural setting. Candidates should be aware that folds and reverse faults indicate crustal shortening in orogenic belts (e.g. Himalayas) but post- orogenic extension by gravitational collapse results in normal faulting. Regional structures. fold and thrust belts. nappe structures occur in compressive tectonic settings and may include large-scale recumbent together with shearing along low angle, thrust faults.
Knowledge and understanding Geological techniques and skills Comments f. Major sedimentary basins are controlled by lithospheric extension (extensional basins) and lithospheric loading (foreland basins). Investigation of the origin and structural control of major sedimentary basins using maps and sections. Candidates should be able to explain the formation of extensional basins (e.g. North Sea Viking Graben, Aegean Sea) and foreland basins (e.g. Po basin – Italy, Adriatic Sea).
Analysis: Each bed should be analysed to determine the processes involved in deposition and the environment of deposition of the sedimentary rock contained. In this way, changes in the environment of deposition up the sequence (over time) can be determined. Teacher/Technician notes: Practical techniques which may be assessed: Construct graphic logs using appropriate scale and symbol sets for unfamiliar geological sequences and exposures. Use sampling techniques in fieldwork. Use appropriate apparatus to record a range of quantitative measurements (to include mass, time, volume, temperature and length).