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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: Dynamics of the Earth's Interior

John Rudge and Sanne Cottaar

8 lectures and 6 practicals

This course brings together ideas from seismology, petrology, geochemistry, mineral physics, and fluid mechanics to study the rich dynamics of the Earth’s interior. We focus particularly on the dynamics of convection, both in the mantle and the inner core, and the dynamics of mantle melting and melt transport.

The first half of the course will focus on global seismological observations, discussing observations of isotropic and anisotropic velocity variations, discontinuities, and attenuation, from the upper mantle down to the inner core. We will show how seismological observations can be interpreted in terms of composition and dynamics. The second half of the course is devoted to the study of melt migration. We will introduce the rich fluid dynamics of two-phase flow, and show how laboratory experiments can be used to place constraints on the rheology of partially molten rock. 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. Finally, the effect of glacial cycles on magmatism will be investigated, touching on some recent controversies: Are Milankovich cycles recorded in crustal thickness variations?

Course requirements: Recommended: Part II Core Geophysics

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