In the beginning, the Earth was entirely fluid. Many fluid processes still occur within and on what is commonly called 'the solid Earth'. The purpose of these lectures is to introduce students to fluid mechanical concepts that can be used to interpret quantitatively a series of geological situations. The course starts with an introductory, overview lecture that describes the current geometry of the Earth. The concepts of compositional convection and the role that it plays in the evolution of the inner core is described. The convective processes that occur in the mantle are then briefly reviewed along with a discussion of the recent ideas of thermal plumes, which may originate at the base of the mantle. The dynamics involved in the operation of volcanoes is also discussed. This includes a summary of our knowledge of magma chambers beneath volcanoes and the processes that lead to their eruption, the evolution of volcanic eruption columns in the atmosphere and the flow of lava on the Earth's surface.
The second lecture will introduce the fundamental ideas of turbulent plumes and thermals in a quiescent environment. The important ideas of entrainment of ambient fluid will be described and quantified. This is an area where powerful use can be made of judicious dimensional reasoning and part of the lecture will explain this all-important technique. As an illustration, the physics of volcanic eruption columns will be described along with the fate of many cubic kilometres of small ash particles as they propagate through the atmosphere and then slowly fall to Earth.
The third lecture concentrates on effects occurring whenever there is fluid at one temperature adjacent to a solid that can react with it. The distinction is made between melting and dissolving of the solid into the fluid and quantitative calculations are discussed showing how the rate of formation of new fluid can be evaluated. The results are applied to understanding the flow of ancient lava flows, which produced a major part of the world's nickel.
Gravity currents occur whenever fluid of one density flows primarily horizontally into fluid of a different density. There are basically two different types of gravity current: those that flow at a high Reynolds number and those that flow at a low Reynolds number. The fourth lecture outlines the fundamental dynamics of both these (quite different) cases and presents applications to lava flows, lava domes and industrial outflows.
The fifth lecture concentrates on an area of current active research: the dynamics of particle-driven flows. The lecture evaluates quantitatively the surprising effects that even relatively small concentrations of particles can make to flows. Areas that are discussed include the effects of particles on convecting fluids and in particle-driven gravity currents. The results are applied to understanding crystal evolution in convecting magma chambers, and ancient 'turbidite' deposits in lakes and the deep sea, and the formation of 'ignimbrites' as a result of catastrophic volcanic eruptions.
The sixth lecture deals with flows in porous media. The governing equations are (somewhat heuristically) derived and various phenomena, and the analytical solutions describing them, are presented. There are many environmental applications of these concepts: from water drainage in soils through oil exploration, production and extraction in sandstones to mineralization in reactive porous rocks near the surface of the Earth.