Herbert Huppert Institute of Theoretical Geophysics, Department of Applied Mathematics and Theoretical Physics, Cambridge, U.K. Gravity currents in nature and industry Wednesday 16th, March 14:05-14:55pm, Carslaw Building Room 373. Gravity currents occur whenever fluid of one density flows predominantly horizontally into fluid of a different density. Industrial and natural occurrences of gravity currents, driven by horizontal density differences, are ubiquitous. This seminar will present a wide review of some of the recent work in this subject. Low Reynolds number currents propagate under a balance of buoyancy and viscous forces and can be completely analysed using lubrication theory to evaluate their rate of spread over either a permeable or impermeable boundary. High Reynolds number currents propagate under a balance of buoyancy and inertia forces and can be analysed using the concepts of shallow water theory. Situations to be discussed will include consideration of the effects of suspended particulate matter, rotation, inward and outwardly propagating axisymmetric currents, and currents propagating into a stratified ambient or a flowing ambient. The seminar will end with a discussion of the spreading of an initially circular cylinder of granular material. Applications will be considered to: lava flows; sea breezes; turbidity currents; the intrusion of volcanic eruption columns into the atmosphere; and rock falls.