Option T5: GEOLOGY OF THE LITHOSPHERE Key Idea 2: Oceanic lithosphere is formed at divergent plate boundaries and reabsorbed by subduction at convergent plate boundaries Knowledge and Geological techniques Comments understanding and skills a. The ocean crust has a Geological interpretation of Candidates may wish to layered structure: seismic layers 1, 2 and 3 make reference to the seismic layers 1, 2 and 3. (sediments, pillow lavas, International Ocean sheeted dykes and gabbro) Discovery Program using evidence from ophiolites (IODP) e.g. Joides 360 and ocean drilling. expedition. b. Ophiolites and ocean Investigation of an ophiolite Candidates are expected drilling provide evidence complex. to have studied an for the origin and example of an ophiolite composition of the oceanic complex (e.g. Oman, crust and upper mantle. Troodos) or a British example (e.g. Ballantrae, Anglesey or the Lizard). c. Ocean basin evolution can Analysis of the evidence for Candidates should be be traced from continental ocean growth and destruction aware that the Wilson rifts through narrow seas as a cyclic event. cycle provides a to mature ocean basins: theoretical framework to the J. Tuzo Wilson cycle. understand the evidence for long term plate movements (e.g. East African Rift Valley-Red Sea, to the Atlantic and the Pacific oceans and through to their eventual closure, as in the case of the collision of the Indian with the Eurasian plate). d. Rates and directions of Interpretation of ocean seafloor spreading may be magnetic anomaly profiles and calculated from the dating maps and ocean floor age of oceanic crust and from distribution maps; calculation the patterns of ocean of rates of seafloor spreading magnetic anomalies from magnetic anomaly and caused by field reversals: mantle plume (hotspot) data – use of radiometric dating plumes as frames of reference and ocean drilling to date for absolute plate movements. magnetic anomalies.
Option T5: GEOLOGY OF THE LITHOSPHERE Key Idea 2: Oceanic lithosphere is formed at divergent plate boundaries and reabsorbed by subduction at convergent plate boundaries Knowledge and understanding Geological techniques and skills Comments a. The ocean crust has a layered structure: seismic layers 1, 2 and 3. Geological interpretation of seismic layers 1, 2 and 3 (sediments, pillow lavas, sheeted dykes and gabbro) using evidence from ophiolites and ocean drilling. Candidates may wish to make reference to the International Ocean Discovery Program (IODP) e.g. Joides 360 expedition. b. Ophiolites and ocean drilling provide evidence for the origin and composition of the oceanic crust and upper mantle. Investigation of an ophiolite complex. Candidates are expected to have studied an example of an ophiolite complex (e.g. Oman, Troodos) or a British example (e.g. Ballantrae, Anglesey or the Lizard). c. Ocean basin evolution can be traced from continental rifts through narrow seas to mature ocean basins: the J. Tuzo Wilson cycle. Analysis of the evidence for ocean growth and destruction as a cyclic event. Candidates should be aware that the Wilson cycle provides a theoretical framework to understand the evidence for long term plate movements (e.g. East African Rift Valley-Red Sea, to the Atlantic and the Pacific oceans and through to their eventual closure, as in the case of the collision of the Indian with the Eurasian plate). d. Rates and directions of seafloor spreading may be calculated from the dating of oceanic crust and from the patterns of ocean magnetic anomalies caused by field reversals: use of radiometric dating and ocean drilling to date magnetic anomalies. Interpretation of ocean magnetic anomaly profiles and maps and ocean floor age distribution maps; calculation of rates of seafloor spreading from magnetic anomaly and mantle plume (hotspot) data – plumes as frames of reference for absolute plate movements.