Plumes are fluid motions that are produced by continuous sources of buoyancy. Convective currents set up by heated bodies such as a cigarette and a space heater are examples. The fluid in contact with the body attains a higher temperature than its surrounding fluid, rises as a result of its lower density, and in so doing draws ambient fluid radially inwards to mix with the warm fluid in the plume. Whereas the plume generated in this fashion may be laminar near the body, at some distance above it will break up into eddies by virtue of the momentum it derives from the force of buoyancy. Other examples of plumes include sewage effluentSewage discharge from sea outfalls, the localised high temperature fluid discharge from the earth’s crust at the bottom of the deep ocean (hydrothermal vents), the injection of concentrated brine (from desalination plants) into sea water, fire plumes, hot gases from smokestacks and volcanic eruptions.