An experimental and theoretical investigation of the flow and density distribution arising from the upward turbulent injection of a dense fluid into a stratified environment of finite extent is presented. Initially, the rising fluid reaches a maximum height before the flow reverses direction and intrudes either along the base of the tank or at an intermediate height in the environment. As more dense fluid is added through either a point or line source, both the fountain and the environment evolve with time. We determine expressions for the motion of the ascending and descending ‘fronts’ that mark the vertical extent of the spreading layer. We also consider the changes to the environmental density profile and determine an expression for the rate at which the top of the fountain rises due to these changes. Finally, we apply our results quantitatively to two physical problems: the replenishment of magma chambers and the heating or cooling of a room.