Topic 4: EARTH STRUCTURE AND GLOBAL TECTONICS Key Idea 1: The Earth has a concentrically zoned structure and composition Knowledge and Geological techniques Comments understanding and skills a. The Earth has a layered Analysis of seismological Candidates should be able structure: crust, mantle, evidence for the internal to use evidence to interpret outer and inner core. structure of Earth: P and S body the state, depth and Each layer has a waves, surface waves, time- probable composition of the distinctive composition distance curves, shadow zones, layers. Earth’s and/or rheological velocity-depth models of Earth properties. Direct and structure, density distribution indirect evidence is with depth. derived from meteorite (stony, iron) Translation of information For exemplification of compositions, mantle between graphical, numerical mathematical skills see xenoliths, mean density and algebraic forms. Mathematical Guidance calculations and for AS Geology. geophysical P19: Measurement of the measurements densities of representative The mathematical skills (seismology, samples of Earth layers (e.g. identified are not exclusive geomagnetism, gravity, granite, basalt). to this section of the conductivity). specification. Simple analysis of geomagnetic evidence for core composition and processes. b. The crust is a thin layer Interpretation of geophysical Candidates should be given of distinctive data on crustal structure the opportunity to evaluate composition overlying (seismic, gravity, magnetic) and validate the new the mantle; continental from continental and oceanic knowledge obtained from and oceanic crust can areas. current ongoing scientific be recognised and research. distinguished by their Analysis of ocean drilling data the significance of differing thicknesses, to re-interpret the serpentinite at the Mohorovičić composition and discontinuity (Moho) at the base Moho discontinuity structure. of the crust (e.g. Joides Resolution 360).
Topic 4: 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. P19: 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 AS 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
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