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Part III Options: Geophysics

GA: Continental Tectonics

Alex Copley

8 lectures and 6 practicals

This course will describe the causes, nature, and consequences of the active deformation of the continents. The course will begin with a discussion of the earthquake cycle (building upon the material in part 2), and the observations and models that can be used to understand the material properties and behaviour of both earthquake-prone and creeping fault zones, and of the underlying ductile lithosphere. The second section of the course will discuss how active faulting accommodates regional extension, compression, and strike-slip deformation. The characteristics of the deformation in each type of tectonic setting will be described, along with the factors that control the configuration and evolution through time of the faulting, and the resulting geological and topographic structures. The third section will focus on the origin and evolution of continental cratons and cores, and their role in controlling the tectonics of the continents. Finally, the course will cover the forces and material properties that control the evolution and behaviour of mountain ranges. The course covers both observational and theoretical aspects of continental deformation, and describes the current state of knowledge and ongoing debates in the subject area.

Examination: Theory exam: 1.5 hours, answer two questions from a choice of three
Practical exam: 1.5 hours, answer all questions
Marks split 60% to theory paper and 40% to practical paper

 

GB: Rifting and Magmatism

Robert (Bob) White

8 lectures and 6 practicals

This course will discuss oceanic and continental rifting and the resultant magmatic and volcanic processes. It will address the role of mantle temperature and mantle plumes in the magmatism that occurs in rifts, with a particular emphasis on the North Atlantic. The North Atlantic is an excellent natural laboratory with well-studied examples of both ‘cold’ (‘non-volcanic’) and ‘hot’ (‘volcanic’) rifted continental margins. The controls on igneous structure of mantle temperature and spreading rate at oceanic rifts are also well displayed in the North Atlantic, with Iceland representing one of the best known examples of rifting above a mantle plume. We will discuss the insights that can be gained into the processes of building igneous crust and the nature of the underlying mantle in rifts from geophysical studies, in particular using seismic reflection, refraction and earthquake seismology, and satellite and GPS geodesy. Processes of melt injection along spreading rifts and volcanic eruptions will be illustrated using the rich resources of Cambridge studies in Iceland which have captured in unprecedented detail the largest eruption in over 250 years.

Examination: Theory exam: 1.5 hours, answer two questions from a choice of three
Practical exam: 1.5 hours, answer all questions
Marks split 60% to theory paper and 40% to practical paper

 

GC: Magma Dynamics

John Rudge and John Maclennan

8 lectures and 6 practicals

This new Part III course studies the dynamics of melt transport through the Earth's mantle and into the crust, bringing together ideas from petrology, geochemistry, and geophysics. The course begins with some simple insights into melt transport from idealised descriptions of the underlying fluid dynamics.

Rheology plays an important role in any dynamical model of melt transport, and the course will consider constraints on the rheology of partially molten rock from lab experiments and theory. The important role of chemistry in controlling melt pathways will be explored, with particular reference to the reaction-infiltration instability and geological observations from the Oman ophiolite. Current challenges in understanding melt transport in subduction zones will be discussed, looking at the factors which control the location of arc volcanoes. The effect of glacial cycles on magmatism will be investigated, touching on some recent controversies: Are Milankovich cycles recorded in crustal thickness variations? The end of the course turns to shallower processes: what happens to magma in the lower crust? How do melts mix? How can diffusion of trace elements be used to constrain the timing of melt transport and mixing?

Course requirements: Recommended: Part II Core Geophysics, Part II Core Petrology

Examination: Theory paper: 90 minutes, answer two questions from a choice of three
Practical paper (Easter Term): 90 minutes, answer all questions
Marks split 60% to theory paper and 40% to practical paper

Past Tripos papers